Abstract
Molecular heterogeneity is a frequent event in cancer responsible of several critical issues in diagnosis and treatment of oncologic patients. Lung tumours are characterized by high degree of molecular heterogeneity associated to different mechanisms of origin including genetic, epigenetic and non-genetic source. In this review, we provide an overview of recognized mechanisms underlying molecular heterogeneity in lung cancer, including epigenetic mechanisms, mutant allele specific imbalance, genomic instability, chromosomal aberrations, tumor mutational burden, somatic mutations. We focus on the role of spatial and temporal molecular heterogeneity involved in therapeutic implications in lung cancer patients.
Keywords: lung cancer, molecular heterogeneity, therapy, driver mutations
1. Introduction
Tumor heterogeneity represents a well-known event in cancer, responsible of several critical issues in diagnosis and treatment of cancer patients. Different levels of heterogeneity have been recognized in cancer particularly interpatient, intratumor and intertumor.
Interpatient heterogeneity is related to genetic and phenotypic variations, observed among individuals with the same tumor type; it could explain the different treatment response of each patient. Intratumor heterogeneity refers to subclonal diversities of tumor cells observed within a single tumor, whereas intertumor heterogeneity is considered as diversity between primary tumor and its metastases 1-3.
Distinct cellular populations within a tumour could differ in a wide spectrum of features from the expression of cell markers to the genetic or epigenetic alterations which could cause heterogeneity 4.
Heterogeneity of molecular profile represents one of the most challenging issues in cancer, particularly in lung cancer, in the light of the resulting therapeutic implications.
In lung cancer, different levels of molecular heterogeneity have been recognized including inter-patients, intra- and inter-tumour variability. Molecular heterogeneity between lung cancer patients with the same histotype represents a proven biological process resulting frequently in different treatment response for each individual patient 1,5.
Furthermore, a high degree of genetic diversity between the primary lung tumor and corresponding metastatic lesions could play a pivotal role in the therapeutic context of lung cancer patients 6-14.
In this review, we provide an overview of recognized mechanisms underlying molecular heterogeneity in lung cancer, including genetic as well as epigenetic sources and non-genetic sources such as cancer stem cells (CSCs) and immune contexture. We focus on the role of spatial and temporal molecular heterogeneity involved in therapeutic implications in lung cancer patients.
2. Mechanisms of origin of molecular heterogeneity in lung cancer
In lung cancer, heterogeneity could be attributed to several different sources 15, 16, related to genetic, epigenetic and non-genetic mechanisms (Fig. 1).
Lung tumours are characterized by extensive genomic aberrations including aneusomy, gains and losses of large chromosome regions, gene rearrangements, copy number gain, amplifications 17.
Genomic instability represents one of the hallmarks in human cancer resulting in various genetic aberrations at different level from mutations in single or few nucleotides to changes of part or entire chromosomes 18.
The term chromosomal instability (CIN) defines a type of genomic instability associated to numerical and structural variations of part or whole chromosomes, for example gain or loss of chromosome fragments, translocations, deletions and amplifications of DNA 19, 20. CIN could have clinical importance in lung cancer patients being generally associated with poor prognosis regardless of other conventional risk factors such as tumour stage, age and sex 21- 23.
Furthermore, CIN may frequently generate the intertumor heterogeneity resulting in a possible increase, before the treatment, of resistant pre-existing sub-clones. Consistent with the selective pressure related to drug treatment, tumor cells characterized by hight levels of CIN might promote drug resistence 24, 20. Moreover, genomic diversity facilitates the adaptation of cancer cell populations in the context of tumor microenvironment resulting in tumor progression and poor prognosis 19.
Jamal‑Hanjani and colleagues have recently performed whole-exome sequencing on multiple regions in a cohort of 100 non-small cell lung cancer (NSCLC) patients who had not received previous systemic therapy. Their results showed widespread intratumor heterogeneity for both somatic copy-number alterations and mutations, particularly an elevated copy-number heterogeneity was associated with an increased risk of recurrence or death (hazard ratio, 4.9; P = 4.4×10-4), statistically significant in multivariate analysis. These finding demonstrate that intratumor heterogeneity due to CIN in NSCLC is strictly associated to increased risk of recurrence or death, suggesting its potential prognostic role 25.
Human malignancies are characterized by a high variable frequency of somatic mutations between and within tumor types, ranging from about 0.001 to 400 per megabase (Mb), suggesting the complexity mutational burden underlying the carcinogenesis 26. Lung cancer is featured by a high tumor mutational burden (TMB) compared to other cancer type, probably related to smoking habits frequently observed in lung cancer patients. Recent finding have highlighted the pivotal role of the TMB as predictor of response to immunotherapies 27.
The tumorigenesis in lung cancer represents a multi-step process involving genetic alterations. Previous studies proposed a mathematical modeling related to a clonal mutation burden in several cancer types, suggesting that lung cancer reflects predominantly mutations accumulated early during tumorigenesis compared to others cancers with late mutation rate 28.
Mutant allele specific imbalance (MASI) represents another genetic mechanism that could promote heterogeneity and impact tumorigenesis, progression, metastasis, prognosis and potentially therapeutic responses in cancer. MASI could occur with copy neutral alteration defined as acquired uniparental disomy (UPD), or with loss of heterozygosity (LOH) due to the loss of the wild-type allele 29. Previous studies reported that MASI is a frequent event in some major oncogenes, such as EGFR, KRAS, PIK3CA, and BRAF 29.
In lung cancer, EGFR MASI is a frequent event counted approximately in 26-37% of cases, more commonly associated with exon 19 deletion than with exon 21 mutation 30, 31. Although related to poor disease-specific survival, EGFR MASI seems not to be associated with time to progression and overall survival, nor to sensitivity to treatment with EGFR specific inhibitors 32.
Although intratumoral molecular heterogeneity in human cancer has historically attributed to genetic alterations, to date a high degree of heterogeneity has been related to epigenetic mechanisms, including DNA methylation, chromatin remodeling, and post-translational modification of histones 16, 33.
Epigenetic modifications induce a variability in gene expression determining a remarkable diversity. Recently, several studies analyzed a potential predictive role of epigenetic modifications in lung cancer, particularly microRNA (miRNAs) and DNA methylation 34. MiRNAs play a crucial role in post-transcriptional regulation of several genes expression by binding to messenger RNA (mRNA) through complementary sequences. Physiologically, a single miRNA can modulate cell growth, differentiation and apoptosis, therefore an altered expression of miRNAs in different cancer types can affect the deregulation of cellular activities 35. Recent findings showed a promising predictive role of miRNA signatures for chemotherapy response and clinical outcome in NSCLC patients, particularly miR-1290, miR-196b, and miR-135a in tumor tissue and miR-25, miR-27b, miR-21, and miR-326 in blood 34. Although preliminary results are encouraging, further prospective studies and clinical validation on large patient cohorts are needed in order to use these miRNAs as predictive biomarkers of the response to treatment to platinum-based chemotherapy in NSCLC patients.
Beyond strictly genetic and epigenetic mechanisms, the heterogeneity could result from various non-genetic mechanisms, including the lung stem cell populations and the immune contexture of lung cancer 15.
CSCs represent a crucial non-genetic source of heterogeneity providing different subclonal lineages dynamically maintained in various solid tumors, including lung cancer 36, 37. Several studies showed that CSCs drive tumor formation and progression, metastasis, recurrence and drug resistance. CSCs have unique characteristics including capacity of self-renewal, multipotency, ability to initiate new tumors in vivo, increased capacity of proliferation and differentiation 38, 39. Studies in genetically engineered mouse models have enabled to prove the existence of lung stem cells able to self-renew regenerating lung parenchima, bronchioles, alveoli and pulmonary vessels 40. Moreover, the distinctive biology of pre-existing different lung cells could drive the distinct phenotypes and genotypes of tumors, resulting in heterogeneity since the tumor initiation. Historically, various lung stem cell populations in different anatomical sites lead to the development of different istotypes 41.
Increasing evidence has highlighted the key contribution of microenvironment in the initiation and progression of lung cancer, since cancer cells are closely interconnected with the milieu of the tumor. The immune contexture of lung cancer is composed of several elements including endothelial cells, fibroblasts, myeloid cells, including T cells, B cells, natural killer cells, mature and immature dendritic cells, tumor-associated macrophages, neutrophils, and mast cells.
Lung tumor heterogeneity could be caused by different acidity and oxygen conditions, or variable concentrations of growth factors that could generate different levels of selective pressure, which in turn could sustain the survival of some clones rather than others 42.
Furthermore, the microenvironment can affect drug resistance since a determinate tumor context could improve the formation of protective compartments in response to treatments. In NSCLC, a typical example is EGFR TKI resistance due to activating MET signaling pathway based on increased hepatocyte growth factor (HGF) secretion by stromal fibroblasts under the stimulation of tumor-derived factors 43.
The variable pressure of lung tumor environment could generate inter- and intra-tumoral heterogeneity that affects sensitivity to target- and immuno- therapy response 44.
Finally, in lung cancer the mixture of genetic aberrations, epigenetic features, differentiation hierarchies of lung stem cell populations and microenvironmental factors all contribute to outgrowth of subpopulations of cells that may have genetic, epigenetic, and/or phenotypic differences, resulting in a condition of heterogeneity.
3. Molecular heterogeneity between histotypes
Lung cancer is historically classified based on tumor histology into small cell (SCLC) and non-small cell lung cancer (NSCLC), the latter accounting of about 80% of cases. NSCLC include different histotypes such as adenocarcinoma (ADC), adenosquamous carcinoma, squamous cell carcinoma (SqCC), and large cell carcinoma. Lung neuroendocrine tumours (LNETs) are classified into different histological types including typical carcinoid, atypical carcinoid, large-cell neuroendocrine carcinoma (LCNEC), and SCLC 45. The different histotypes are associated with specific different mutational profiles (Table 1) 46-73.
Table 1.
Histotype | Type of genomic aberrations | Gene | Frequency (%) | Currently available Target therapy | Ref. | ||
---|---|---|---|---|---|---|---|
NSCLC | ADC | Fusions | ALK | 3-7 | A | 46 | |
ROS1 | 2-3 | A | 47 | ||||
RET | 1-2 | NA | 47 | ||||
NTRK1 | 1-2 | NA | 48 | ||||
Mutations | EGFR | 30-40 | A | 49 | |||
BRAF | 0.5-5 | NA | 47 | ||||
KRAS | 20-30 | NA | 47 | ||||
MET | 3-4 | NA | 50 | ||||
PTEN | 1.7 | NA | 51 | ||||
PDGFRA | 6-7 | NA | 52 | ||||
PIK3CA | 5 | NA | 53, 54 | ||||
TP53 | 52 | NA | 55 | ||||
Copy number gene alterations | Gains | ERBB2 | 2-5 | NA | 56 | ||
EGFR | 10 | NA | 57 | ||||
MET | 2-5 | NA | 50 | ||||
TERT | 75 | NA | 58 | ||||
Losses | CDKN2A | 7 | NA | 59 | |||
SqCCs | Fusions | FGFRs | 23 | NA | 60 | ||
Mutations | TP53 | 79 | NA | 55 | |||
NF1 | 10 | NA | 52 | ||||
FGFR1 | 20 | NA | 60 | ||||
FGFR2 | 3 | NA | 61 | ||||
DDR2 | 2-3 | NA | 62 | ||||
BRAF | 4-5 | NA | 63 | ||||
KRAS | 1-2 | NA | 64 | ||||
PDGFRA | 4 | NA | 52 | ||||
PIK3CA | 15 | NA | 53, 54 | ||||
PTEN | 10 | NA | 51 | ||||
Copy number gene alterations | Gains | SOX2 | 65 | NA | 65 | ||
PIK3CA | 15 | NA | 53, 54 | ||||
TP53 | 79 | NA | 55 | ||||
Losses | CDKN2A | 15 | NA | 59 | |||
PTEN | 8 | NA | 66 | ||||
SCLC | Mutations | TP53 | 90 | NA | 67, 68 | ||
RB1 | 90 | NA | 67, 68 | ||||
EP300 | 4-6 | NA | 69, 70 | ||||
CREBBP | 4-6 | NA | 69, 70 | ||||
PTEN | 10-18 | NA | 68 | ||||
Copy number gene alterations | Gains | MYC | 20-30 | NA | 71 | ||
MYCN | 20-30 | NA | 71 | ||||
MYCL1 | 20-30 | NA | 71 | ||||
SOX2 | 27 | NA | 72 | ||||
FGFR1 | 5-6 | NA | 73 |
Technological advances in molecular biology have provided a comprehensive means of molecular profile and the identification of driver oncogenes.
Oncogenes generally encode proteins that regulate several cellular processes including proliferation and survival. Mutations, gene rearrangements and gene amplification represent the most common genetic aberrations that could activate an oncogene, leading to a deregulated expression and/or function of the gene 5.
The definition of “driver” and “passenger” mutations represents a key point related to the tumorigenesis and the treatment with specific inhibitors. The term “driver” refers to somatic mutations that are able to increase the fitness of the cell, whereas “passenger” includes mutations that are biologically neutral and not confers growth advantage 74-76.
A “driver” mutation is causally related to cancer development, so in this view targeting a “driver” mutation with specific inhibitors represents generally a successful therapeutic strategy in cancer.
NSCLC is one of the tumors with a higher mutation rate of protein-altering mutations, particularly adenocarcinomas showed a rate of 3.5 per Mb and squamous cell carcinomas a rate of 3.9, compared to the rate of 1.8 across all tumor types 77. Large-scale sequencing studies have shown a broad spectrum of genetic aberrations in NSCLC and a different genetic profile between lung adenocarcinomas and lung squamous cell carcinomas 25, 78-80.
NSCLC molecular profile is markedly distinct from other lung cancer histotypes: mainly in adenocarcinoma specific therapeutic targets have been defined. EGFR activating mutation, ALK rearrangements (ALK-R) and ROS1 rearrangements (ROS1-R) represent genetic hallmarks that predict a good response to treatment with specific tyrosine kinase inhibitor (TKI) in lung cancer with adenocarcinoma histology. Beyond these targetable alterations, other genomic aberrations have been reported in adenocarcinoma, including mutations, copy number gene alterations, as well as fusion mechanisms involving the receptor tyrosine kinase, such as ROS1, NTRK1 and RET (Table 1).
The updated molecular testing guidelines for the selection of lung cancer patients proposed by the College of American Pathologists (CAP), the International Association for the Study of Lung Cancer (IASLC), and the Association for Molecular Pathology (AMP) suggest the analysis of genetic alterations of additional genes such as ERBB2, MET, BRAF, KRAS, and RET not indicated as a routine stand-alone assay however as additional genes for laboratories that perform next-generation sequencing panels 47, 81.
Historically, a better understanding of the genetic aberrations was confined exclusively to adenocarcinoma, but more recently next-generation sequencing technologies are allowing a better molecular characterization also in other hystotypes.
Recently, increasing interest in comprehensive genome-wide characterization of SqCC has been reported, however, unfortunately no therapeutic targets have been yet identified. As it would be expected, molecular landscape in SqCC is distinct from the 'driver' mutations generally associated to adenocarcinoma. Several recurrent mutations have been found in SqCC, including DDR2 mutations, FGFR1 amplification, FGFR2,3,4 mutations and rearrangements (Table 1).
Recently, Devarakonda and colleagues analysed the molecular profile of 908 resected NSCLC specimens by sequencing a targeted panel consisting of 1,538 genes. The analyzed panel set of genes was selected based on knowledge of the most frequent genes involved in lung cancer pathogenesis, regardless of their clinical implications 27. Sequencing results show that the genes most differentially mutated between ADC and SqCC were KRAS (19% versus 2%), TP53 (44% versus 69%), and STK11 (21% versus 2%); furthermore aberrations in receptor tyrosine kinase/RAS signaling were detected in approximately 70% of ADCs analyzed. As previously reported, activating mutations in KRAS, HRAS, NRAS, and EGFR were identified only in 3% of SqCCs 27.
Unfortunately, until now no molecular targets have been identified for the treatment with specific inhibitors of LNETs, thus surgery and/or conventional systemic therapy represents the treatment of choice for these tumors 82. Previous studies analysing genomic aberrations in SCLC shown that the most frequent are inactivating mutations in TP53 and Rb1 genes, whereas activating mutations of EGFR, KRAS, as well mutations of PIK3CA, c-Myc amplification, c-KIT overexpression and PTEN mutation/loss are rare 83-85.
Recently, Simbolo and colleagues performed a comprehensive molecular analysis of LNETs, showing a prognostic impact of aberrations involved in RB1 and TERT in all histological subtypes, MEN1 mutations in SCLCs and KMT2D in ACs 86.
In the context of the predictive value of target therapies, preliminary data showed that the alterations involved in PI3K/AKT/mTOR pathway activation could be a potential therapeutic target, particularly PIK3CA mutations and copy gains of PIK3CA and RICTOR 87.
In conclusion, high heterogeneous genomic profiles between different histotypes of lung cancer could provide an explanation for great variable treatment response and prognostic stratification histotypes-related factors.
4. Inter- and intra-tumor heterogeneity of oncogenic driver mutations in NSCLC
In the last decade, the therapeutic decision-making approach based on the presence of oncogenic “driver” aberrations has incredibly changed the treatment of NSCLC patients with the development of target therapies, particularly specific inhibitor of EGFR, ALK and ROS1 aberrations.
In NSCLC, oncogenic driver mutations are frequently associated with specific clinical and pathological features, including histologic subtypes, gender, ethnic, age, past smoking history/status of other common oncogenes.
Dietz and colleagues investigated the spatial distribution of allele frequencies of KRAS and EGFR mutations in lung adenocarcinomas throughout whole tumor sections in correlation to all different histopathological patterns. The variant allele frequencies (VAFs) of KRAS and EGFR mutations were determined for all segments by digital PCR and their results showed that mutant allele frequencies were significantly higher in segments with a predominant solid pattern compared to all other histologies (p < 0.01) 88.
Heterogeneous distribution of EGFR mutations was observed within a primary tumor composed of mixed atypical adenomatous hyperplasia, bronchoalveolar carcinoma, and adenocarcinoma 89.
Previously, we demonstrated that homogeneity in EGFR aberrations occur within lung mixed ADCs regardless histological patterns, contrary to ALK rearrangements that are generally observed in solid patterns and exclusively in the adenocarcinoma areas of adenosquamous lung carcinomas 90.
In lung cancer, frequently cytologic samples or small biopsies represent the only specimens for tumor diagnosis and affect the choice of treatment, thus a potential genetic heterogeneity within a primary tumor could crucially affect clinical outcome to a specific treatment.
NSCLC patients harboring targetable driver mutations generally respond well to specific inhibitors, however some patients show short responses and TKIs resistance that could be frequently explained through molecular heterogeneity between the primary lung tumors and the metastases 91-93.
The intratumor genetic heterogeneity represents one of the most critical issues related to sensitivity to the treatment and ultimately to resistance to specific TKI. In literature, several studies in lung cancer series reported discrepancies in EGFR, ALK and KRAS mutational status between primary tumors and corresponding metastases 94-99. Moreover, numerous studies have revealed the concordance of EGFR status in primary tumours and corresponding metastases, suggesting a possible explanation of the discordance due to technical limitations 6, 14, 90, 100, 101. In contrast, several results demonstrated hetereogeneity in the EGFR mutation status between the primary lung tumor and the metastases 94, 102, 103.
Chen et al analyzed EGFR mutational condition in paired samples of primary lung adenocarcinoma and regional lymph nodes or distant metastases. Heterogeneity of EGFR mutations was higher (rate of 24.4%; 10 of 41) in patients with multiple pulmonary nodules resulting in significant clinical implications since the current guidelines recommend biopsy in only one lesion 93.
For ALK gene, some data revealed disconcordance between ALK rearrangement in primary NSCLC tumor and corresponding metastases 98, 105.
In conclusion, discordances between oncogenic driver mutations status in primary lesions and metastases may have significant implications in treatment with specific inhibitors of NSCLC patients.
5. Heterogeneity of molecular profile and potential value in clinical setting of lung cancer
Tailored therapies based on the identification of molecular targets represent currently a well-established therapeutic scenario in the treatment of NSCLC patients, however short responses and development of resistance are frequently observed in daily clinical practice. Although the optimal efficacy of specific TKIs, a subset of NSCLC patients often shows a mixed response to treatment. Patient-specific response and resistance can originate not only from secondary aberrations induced by targeted therapy but also from intratumoral genetic heterogeneity 106.
To date, different models have been proposed to explain the difference of genetic profile between primary tumour and corresponding metastases. Particularly, a classical model for development of metastases proposes that primary tumor cells have a low metastatic potential, thus the acquirement of enough genetic aberrations improve the metastatic progression. Another theory suggests a metastatic potential of primary tumor that leads a clonal progression from a non-malignant to malignant state, involving random metastases from tumor cells without any significant additional genetic aberrations 103.
Recently, a multicenter prospective cohort study, Tracking Non-Small-Cell Lung Cancer Evolution through Therapy (TRACERx), investigated the intratumor heterogeneity in surgically resected early-stage NSCLCs 25. TRACERx analyzed the intratumor variability of several genetic aberrations including single or dinucleotide base substitutions, small insertions and deletions, somatic copy-number alterations 25.
Jamal‑Hanjani and colleagues demonstrated that some targetable driver mutations involved in EGFR, MET and BRAF are generally clonal and early, compared to other aberrations in genes such as PIK3CA, NF1, KRAS, TP53, and NOTCH family members that are subclonal and appear later in tumor evolution 25.
Beyond heterogeneity of druggable driver mutations, previous studies have analyzed the presence of mutational signatures across human cancer types, proving that specific mutational signatures could correlate with defined tumors 26.
In ADCs, SqCCs and SCLC a higher prevalence of mutational signature associated with smoking has been reported. Similarly, the signature associated to APOBEC, a family of cytidine deaminase enzymes involved in messenger RNA editing, exhibited strong correlations with ADCs and SqCCs 26.
Recently, a multicenter prospective study analyzed the expression clonal and subclonal of these validated mutational signatures suggesting that the signature associated to APOBEC could frequently induce subclonal mutations resulting in a spatial heterogeneity 25.
In lung cancer, another great biological variability was reported between smokers versus never-smokers, since several carcinogens of the tobacco smoke lead to a high mutational rate including both driver and passenger mutations 26, 107.
Recently, Soo and colleagues showed the clinical-pathological features typical of never-smokers analyzed in a wide series of NSCLC, in order to clarify their characteristics still not fully known. Never-smokers showed a higher rate of ALK-rearrangement (26% vs. 4%, p < .001) and EGFR mutations (36% vs. 8%, p < .001) 108.
Genome-wide studies identified several potential genetic marker of susceptibility in LCINS, such as chromosomal locus 5p15.33 comprising TERT and CLPTMIL genes, the hypoxia-inducible factor-2α EPAS1, specific SNPs in CSF1R, p63, TP63 genes, a functional polymorphism in CSF1R gene 109.
The biological differences between these two subsets result in differential response to therapies, including EGFR inhibitors, thus a better genetic characterization of lung cancer in non-smokers (LCINS) is needed 110.
Conclusion
Discordance of molecular profiles between primary lesions and their corresponding metastases in the context of druggable driver mutations could be the key point in personalized medicine of lung cancer patients. Indeed, intra-tumor molecular heterogeneity represents a great source of concern in mixed tumor responses to treatment, including treatment with specific TKI inhibitors but also chemotherapy.
In lung cancer patients the rebiopsy is rarely performed, however in the view of intratumor heterogeneity a single biopsy-based analyses for personalized medicine could be a great limitation.
Acknowledgments
The manuscript was supported by 'Programma Valere', funded by Università Vanvitelli per la Ricerca.
Abbreviations
- CSCs
cancer stem cells
- CIN
chromosomal instability
- NSCLC
non-small cell lung cancer
- TMB
tumor mutational burden
- MASI
mutant allele specific imbalance
- miRNAs
microRNA
- SCLC
small-cell lung carcinoma
- ADC
adenocarcinoma
- SqCC
squamous cell carcinoma
- LNETs
lung neuroendocrine tumours
- ALK-R
ALK rearrangements
- ROS1-R
ROS1 rearrangements
- TKI
tyrosine kinase inhibitor
References
- 1.Jamal-Hanjani M, Quezada SA, Larkin J. et al. Translational implications of tumor heterogeneity. Clin Cancer Res. 2015;21:1258–1266. doi: 10.1158/1078-0432.CCR-14-1429. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Rich JN. Cancer stem cells: understanding tumor hierarchy and heterogeneity. Medicine (Baltimore) 2016;95(1 Suppl 1):S2–S7. doi: 10.1097/MD.0000000000004764. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Burrell RA, McGranahan N, Bartek J. et al. The causes and consequences of genetic heterogeneity in cancer evolution. Nature. 2013;501:338–345. doi: 10.1038/nature12625. [DOI] [PubMed] [Google Scholar]
- 4.Kreso A, Dick JE. Evolution of the cancer stem cell model. Cell Stem Cell. 2014;14:275–291. doi: 10.1016/j.stem.2014.02.006. [DOI] [PubMed] [Google Scholar]
- 5.Vogelstein B, Papadopoulos N, Velculescu VE. et al. Cancer genome landscapes. Science. 2013;339:1546–58. doi: 10.1126/science.1235122. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.de Bruin EC, McGranahan N, Mitter R. et al. Spatial and temporal diversity in genomic instability processes defines lung cancer evolution. Science. 2014;346:251–256. doi: 10.1126/science.1253462. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Walter MJ, Shen D, Ding L. et al. Clonal architecture of secondary acute myeloid leukemia. N Engl J Med. 2012;366:1090–1098. doi: 10.1056/NEJMoa1106968. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Boeckx N, Op de Beeck K, Deschoolmeester V, Anti-EGFR resistance in colorectal cancer: current knowledge and future perspectives. Curr Colorectal Cancer Rep; 2014. pp. 1–15. [Google Scholar]
- 9.Diaz LA, Williams RT, Wu J. et al. The molecular evolution of acquired resistance to targeted EGFR blockade in colorectal cancers. Nature. 2012;486:1–4. doi: 10.1038/nature11219. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Fojo T, Mailankody S, Lo A. Unintended consequences of expensive cancer therapeutics-the pursuit of marginal indications and a me-too mentality that stifles innovation and creativity: the john conley lecture. JAMA Otolaryngol Head Neck Surg. 2014;140:1225–1236. doi: 10.1001/jamaoto.2014.1570. [DOI] [PubMed] [Google Scholar]
- 11.Kleppe M, Levine RL. Tumor heterogeneity confounds and illuminates. Nat Med. 2014;20:342–344. doi: 10.1038/nm.3522. [DOI] [PubMed] [Google Scholar]
- 12.Marusyk A, Almendro V, Polyak K. Intra-tumour heterogeneity: a looking glass for cancer? Nat Rev Cancer. 2012;12:323–334. doi: 10.1038/nrc3261. [DOI] [PubMed] [Google Scholar]
- 13.Vogelstein B, Papadopoulos N, Velculescu VE. et al. Cancer genome landscapes. Science. 2013;339:1546–1558. doi: 10.1126/science.1235122. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Zhang J, Fujimoto J, Zhang J. et al. Intratumor heterogeneity in localized lung adenocarcinomas delineated by multiregion sequencing. Science. 2014;346:256–259. doi: 10.1126/science.1256930. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Neelakantan D, Drasin DJ, Ford HL. Intratumoral heterogeneity: Clonal cooperation in epithelial-to-mesenchymal transition and metastasis. Cell Adh Migr. 2015;9:265–276. doi: 10.4161/19336918.2014.972761. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.McGranahan N, Swanton C. Clonal Heterogeneity and Tumor Evolution: Past, Present, and the Future. Cell. 2017;168:613–628. doi: 10.1016/j.cell.2017.01.018. [DOI] [PubMed] [Google Scholar]
- 17.Varella-Garcia M. Chromosomal and genomic changes in lung cancer. Cell Adh Migr. 2010;4:100–106. doi: 10.4161/cam.4.1.10884. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Negrini S, Gorgoulis VG, Halazonetis TD. Genomic instability an evolving hallmark of cancer. Nat Rev Mol Cell Biol. 2010;11:220–228. doi: 10.1038/nrm2858. [DOI] [PubMed] [Google Scholar]
- 19.Lee AJ, Endesfelder D, Rowan AJ. et al. Chromosomal instability confers intrinsic multidrug resistance. Cancer Res. 2011;71:1858–1870. doi: 10.1158/0008-5472.CAN-10-3604. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.McGranahan N, Burrell RA, Endesfelder D. et al. Cancer chromosomal instability: therapeutic and diagnostic challenges. EMBO Rep. 2012;13:528–358. doi: 10.1038/embor.2012.61. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Carter SL, Eklund AC, Kohane IS. et al. A signature of chromosomal instability inferred from gene expression profiles predicts clinical outcome in multiple human cancers. Nat Genet. 2006;38:1043–1048. doi: 10.1038/ng1861. [DOI] [PubMed] [Google Scholar]
- 22.Mettu RK, Wan YW, Habermann JK. et al. A 12-gene genomic instability signature predicts clinical outcomes in multiple cancer types. Int J Biol Markers. 2010;25:219–228. doi: 10.5301/jbm.2010.6079. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Yoo JW, Seo KW, Jang SJ. et al. The relationship between the presence of chromosomal instability and prognosis of squamous cell carcinoma of the lung: fluorescence in situ hybridization analysis of paraffin-embedded tissue from 47 Korean patients. J Korean Med Sci. 2010;25:863–867. doi: 10.3346/jkms.2010.25.6.863. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Gerlinger M, Swanton C. How Darwinian models inform therapeutic failure initiated by clonal heterogeneity in cancer medicine. Br J Cancer. 2010;103:1139–1143. doi: 10.1038/sj.bjc.6605912. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Jamal-Hanjani M, Wilson GA, McGranahan N. et al. Tracking the Evolution of Non-Small-Cell Lung Cancer. N Engl J Med. 2017;376:2109–2121. doi: 10.1056/NEJMoa1616288. [DOI] [PubMed] [Google Scholar]
- 26.Alexandrov LB, Nik-Zainal S, Wedge DC. et al. Signatures of mutational processes in human cancer. Nature. 2013;500:415–421. doi: 10.1038/nature12477. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Devarakonda S, Rotolo F, Tsao MS. et al. Tumor Mutation Burden as a Biomarker in Resected Non-Small-Cell Lung Cancer. J Clin Oncol. 2018 doi: 10.1200/JCO.2018.78.1963. [Epub ahead of print] [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Tomasetti C, Vogelstein B, Parmigiani G. Half or more of the somatic mutations in cancers of self-renewing tissues originate prior to tumor initiation. Proc Natl Acad Sci U S A. 2013;110:1999–2004. doi: 10.1073/pnas.1221068110. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Soh J, Okumura N, Lockwood WW, Oncogene mutations, copy number gains and mutant allele specific imbalance (MASI) frequently occur together in tumor cells. PLoS One; 2009. p. 7464. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Oakley GJ, Chiosea SI. Higher dosage of the epidermal growth factor receptor mutant allele in lung adenocarcinoma correlates with younger age, stage IV at presentation, and poorer survival. J Thorac Oncol. 2011;6:1407–1412. doi: 10.1097/JTO.0b013e31821d41af. [DOI] [PubMed] [Google Scholar]
- 31.Malapelle U, Vatrano S, Russo S. et al. EGFR mutant allelic-specific imbalance assessment in routine samples of non-small cell lung cancer. J Clin Pathol. 2015;68:739–741. doi: 10.1136/jclinpath-2015-203101. [DOI] [PubMed] [Google Scholar]
- 32.Takano T, Ohe Y, Sakamoto H. et al. Epidermal growth factor receptor gene mutations and increased copy numbers predict gefitinib sensitivity in patients with recurrent non-small-cell lung cancer. J Clin Oncol. 2005;23:6829–6837. doi: 10.1200/JCO.2005.01.0793. [DOI] [PubMed] [Google Scholar]
- 33.Portela A, Esteller M. Epigenetic modifications and human disease. Nat Biotechnol. 2010;28:1057–1068. doi: 10.1038/nbt.1685. [DOI] [PubMed] [Google Scholar]
- 34.Szejniuk WM, Robles AI, McCulloch T. et al. Epigenetic predictive biomarkers for response or outcome to platinum-based chemotherapy in non-small cell lung cancer, current state-of-art. Pharmacogenomics J. 2018;19:5–14. doi: 10.1038/s41397-018-0029-1. [DOI] [PubMed] [Google Scholar]
- 35.Calin GA, Croce CM. MicroRNA signatures in human cancers. Nat Rev Cancer. 2006;6:857–66. doi: 10.1038/nrc1997. [DOI] [PubMed] [Google Scholar]
- 36.Michor F, Polyak K. The origins and implications of intratumor heterogeneity. Cancer Prev Res (Phila) 2010;3:1361–1364. doi: 10.1158/1940-6207.CAPR-10-0234. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Codony-Servat J, Verlicchi A, Rosell R. Cancer stem cells in small cell lung cancer. Transl Lung Cancer Res. 2016;5:16–25. doi: 10.3978/j.issn.2218-6751.2016.01.01. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.Wang P, Gao Q, Suo Z. et al. Identification and characterization of cells with cancer stem cell properties in human primary lung cancer cell lines. PLoS One. 2013;8:57020. doi: 10.1371/journal.pone.0057020. [DOI] [PMC free article] [PubMed] [Google Scholar] [Retracted]
- 39.Sales KM, Winslet MC, Seifalian AM. Stem cells and cancer: an overview. Stem Cell Rev. 2007;3:249–55. doi: 10.1007/s12015-007-9002-0. [DOI] [PubMed] [Google Scholar]
- 40.Kajstura J, Rota M, Hall SR. et al. Evidence for human lung stem cells. N Engl J Med. 2011;364:1795–806. doi: 10.1056/NEJMoa1101324. [DOI] [PMC free article] [PubMed] [Google Scholar] [Retracted]
- 41.Chen Z, Fillmore CM, Hammerman PS. et al. Non-small-cell lung cancers: a heterogeneous set of diseases. Nat Rev Cancer. 2014;14:535–546. doi: 10.1038/nrc3775. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 42.Trédan O, Galmarini CM, Patel K. et al. Drug resistance and the solid tumor microenvironment. J Natl Cancer Inst. 2007;99:1441–1454. doi: 10.1093/jnci/djm135. [DOI] [PubMed] [Google Scholar]
- 43.Yamada T, Takeuchi S, Kita K. et al. Hepatocyte growth factor induces resistance to anti-epidermal growth factor receptor antibody in lung cancer. J Thorac Oncol. 2012;7:272–280. doi: 10.1097/JTO.0b013e3182398e69. [DOI] [PubMed] [Google Scholar]
- 44.Zito Marino F, Ascierto PA, Rossi G. et al. Are tumor-infiltrating lymphocytes protagonists or background actors in patient selection for cancer immunotherapy? Expert Opin Biol Ther. 2017;17:735–746. doi: 10.1080/14712598.2017.1309387. [DOI] [PubMed] [Google Scholar]
- 45.Travis WD, Brambilla E, Nicholson AG. et al. The 2015 World Health Organization Classification of Lung Tumors: Impact of Genetic, Clinical and Radiologic Advances Since the 2004 Classification. J Thorac Oncol. 2015;10:1243–1260. doi: 10.1097/JTO.0000000000000630. [DOI] [PubMed] [Google Scholar]
- 46.Franco R, Rocco G, Marino FZ. et al. Anaplastic lymphoma kinase: a glimmer of hope in lung cancer treatment? Expert Rev Anticancer Ther. 2013;13:407–20. doi: 10.1586/era.13.18. [DOI] [PubMed] [Google Scholar]
- 47.Lindeman NI, Cagle PT, Aisner DL. et al. Updated Molecular Testing Guideline for the Selection of Lung Cancer Patients for Treatment With Targeted Tyrosine Kinase Inhibitors: Guideline From the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology. Arch Pathol Lab Med. 2018;142:321–346. doi: 10.5858/arpa.2017-0388-CP. [DOI] [PubMed] [Google Scholar]
- 48.Vaishnavi A, Capelletti M, Le AT. et al. Oncogenic ad drug-sensitive NTRK1 rearrangements in lung cancer. Nat Med. 2013;19:1469–1472. doi: 10.1038/nm.3352. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 49.Paez JG, Jänne PA, Lee JC. et al. EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy. Science. 2004;304:1497–500. doi: 10.1126/science.1099314. [DOI] [PubMed] [Google Scholar]
- 50.Salgia R. MET in Lung Cancer: Biomarker Selection Based on Scientific Rationale. Mol Cancer Ther. 2017;16:555–565. doi: 10.1158/1535-7163.MCT-16-0472. [DOI] [PubMed] [Google Scholar]
- 51.Jin G, Kim MJ, Jeon HS. et al. PTEN mutations and relationship to EGFR, ERBB2, KRAS, and TP53 mutations in non-small cell lung cancers. Lung Cancer. 2010;69:279–83. doi: 10.1016/j.lungcan.2009.11.012. [DOI] [PubMed] [Google Scholar]
- 52.Kandoth C, McLellan MD, Vandin F. et al. Mutational landscape and significance across 12 major cancer types. Nature. 2013;502:333–339. doi: 10.1038/nature12634. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 53.Engelman JA, Chen L, Tan X. et al. Effective use of PI3K and MEK inhibitors to treat mutant Kras G12D and PIK3CA H1047R murine lung cancers. Nat Med. 2008;14:1351–6. doi: 10.1038/nm.1890. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 54.Kawano O, Sasaki H, Endo K. et al. PIK3CA mutation status in Japanese lung cancer patients. Lung Cancer. 2006;54:209–15. doi: 10.1016/j.lungcan.2006.07.006. [DOI] [PubMed] [Google Scholar]
- 55.Mitsudomi T, Hamajima N, Ogawa M. et al. Prognostic significance of p53 alterations in patients with non-small cell lung cancer: a meta-analysis. Clin. Cancer Res. 2000;6:4055–4063. [PubMed] [Google Scholar]
- 56.Li BT, Ross DS, Aisner DL. et al. HER2 Amplification and HER2 Mutation Are Distinct Molecular Targets in Lung Cancers. J Thorac Oncol. 2016;11:414–9. doi: 10.1016/j.jtho.2015.10.025. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 57.Fiala O, Pesek M, Finek J. et al. Epidermal Growth Factor Receptor Gene Amplification in Patients with Advanced-stage NSCLC. Anticancer Res. 2016;36:455–60. [PubMed] [Google Scholar]
- 58.Zhu CQ, Cutz JC, Liu N. et al. Amplification of telomerase (hTERT) gene is a poor prognostic marker in non-small-cell lung cancer. Br J Cancer. 2006;94:1452–9. doi: 10.1038/sj.bjc.6603110. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 59.Lou-Qian Z, Rong Y, Ming L. et al. The prognostic value of epigenetic silencing of p16 gene in NSCLC patients: a systematic review and meta-analysis. PLoS One. 2013;8:54970. doi: 10.1371/journal.pone.0054970. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 60.Marek L, Ware KE, Fritzsche A. et al. Fibroblast growth factor (FGF) and FGF receptor-mediated autocrine signaling in non-small-cell lung cancer cells. Mol Pharmacol. 2009;75:196–207. doi: 10.1124/mol.108.049544. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 61.The Cancer Genome Atlas Research Network (TCGA). Comprehensive genomic characterization of squamous cell lung cancers. Nature. 2012;489:519–525. doi: 10.1038/nature11404. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 62.Hammerman PS, Sos ML, Ramos AH. et al. Mutations in the DDR2 kinase gene identify a novel therapeutic target in squamous cell lung cancer. Cancer Discov. 2011;1:78–89. doi: 10.1158/2159-8274.CD-11-0005. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 63.Paik PK, Arcila ME, Fara M. et al. Clinical characteristics of patients with lung adenocarcinomas harboring BRAF mutations. J Clin Oncol. 2011;29:2046–51. doi: 10.1200/JCO.2010.33.1280. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 64.Mascaux C, Iannino N, Martin B. et al. The role of RAS oncogene in survival of patients with lung cancer: a systematic review of the literature with meta-analysis. Br J Cancer. 2005;92:131–9. doi: 10.1038/sj.bjc.6602258. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 65.Bass AJ, Watanabe H, Mermel CH. et al. SOX2 is an amplified lineage-survival oncogene in lung and esophageal squamous cell carcinomas. Nat Genet. 2009;41:1238–42. doi: 10.1038/ng.465. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 66.Soria JC, Lee HY, Lee JI. et al. Lack of PTEN expression in non-small cell lung cancer could be related to promoter methylation. Clin Cancer Res. 2002;8:1178–84. [PubMed] [Google Scholar]
- 67.Meuwissen R, Linn SC, Linnoila RI. et al. Induction of small cell lung cancer by somatic inactivation of both Trp53 and Rb1 in a conditional mouse model. Cancer Cell. 2003;4:181–9. doi: 10.1016/s1535-6108(03)00220-4. [DOI] [PubMed] [Google Scholar]
- 68.Karachaliou N, Pilotto S, Lazzari C. et al. Cellular and molecular biology of small cell lung cancer: an overview. Transl Lung Cancer Res. 2016;5:2–15. doi: 10.3978/j.issn.2218-6751.2016.01.02. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 69.Umemura S, Mimaki S, Makinoshima H. et al. Therapeutic priority of the PI3K/AKT/mTOR pathway in small cell lung cancers as revealed by a comprehensive genomic analysis. J Thorac Oncol. 2014;9:1324–1331. doi: 10.1097/JTO.0000000000000250. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 70.Ross JS, Wang K, Elkadi OR. et al. Next-generation sequencing reveals frequent consistent genomic alterations in small cell undifferentiated lung cancer. J Clin Pathol. 2014;67:772–776. doi: 10.1136/jclinpath-2014-202447. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 71.Semenova EA, Nagel R, Berns A. Origins, genetic landscape, and emerging therapies of small cell lung cancer. Genes Dev. 2015;29:1447–62. doi: 10.1101/gad.263145.115. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 72.Peifer M, Fernández-Cuesta L, Sos ML. et al. Integrative genome analyses identify key somatic driver mutations of small-cell lung cancer. Nat Genet. 2012;44:1104–1110. doi: 10.1038/ng.2396. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 73.Schultheis AM, Bos M, Schmitz K. et al. Fibroblast growth factor receptor 1 (FGFR1) amplification is a potential therapeutic target in small-cell lung cancer. Mod Pathol. 2014;27:214–21. doi: 10.1038/modpathol.2013.141. [DOI] [PubMed] [Google Scholar]
- 74.Fisher R, Pusztai L, Swanton C. Cancer heterogeneity: implications for targeted therapeutics. Br J Cancer. 2013;108:479–85. doi: 10.1038/bjc.2012.581. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 75.Haber DA, Settleman J. Cancer: drivers and passengers. Nature. 2007;446:145–6. doi: 10.1038/446145a. [DOI] [PubMed] [Google Scholar]
- 76.Greenman C, Stephens P, Smith R. et al. Patterns of somatic mutation in human cancer genomes. Nature. 2007;446:153–8. doi: 10.1038/nature05610. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 77.Kan Z, Jaiswal BS, Stinson J. et al. Diverse somatic mutation patterns and pathway alterations in human cancers. Nature. 2010;466:869–873. doi: 10.1038/nature09208. [DOI] [PubMed] [Google Scholar]
- 78.Imielinski M, Berger AH, Hammerman PS. et al. Mapping the hallmarks of lung adenocarcinoma with massively parallel sequencing. Cell. 2012;150:1107–20. doi: 10.1016/j.cell.2012.08.029. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 79.Govindan R, Ding L, Griffith M. et al. Genomic landscape of non-small cell lung cancer in smokers and never-smokers. Cell. 2012;150:1121–34. doi: 10.1016/j.cell.2012.08.024. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 80.Campbell JD, Alexandrov A, Kim J. et al. Distinct patterns of somatic genome alterations in lung adenocarcinomas and squamous cell carcinomas. Nat Genet. 2016;48:607–16. doi: 10.1038/ng.3564. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 81.Hanna N, Johnson D, Temin S. et al. Systemic Therapy for Stage IV Non-Small-Cell Lung Cancer: American Society of Clinical Oncology Clinical Practice Guideline Update. J Clin Oncol. 2017;35:3484–3515. doi: 10.1200/JCO.2017.74.6065. [DOI] [PubMed] [Google Scholar]
- 82.Gridelli C, Rossi A, Airoma G. et al. Treatment of pulmonary neuroendocrine tumours: state of the art and future developments. Cancer Treat Rev. 2013;39:466–472. doi: 10.1016/j.ctrv.2012.06.012. [DOI] [PubMed] [Google Scholar]
- 83.Wistuba II, Gazdar AF, Minna JD. Molecular genetics of small cell lung carcinoma. Semin Oncol. 2001;28:3–13. [PubMed] [Google Scholar]
- 84.Shibata T, Kokubu A, Tsuta K. et al. Oncogenic mutation of PIK3CA in small cell lung carcinoma: a potential therapeutic target pathway for chemotherapy-resistant lung cancer. Cancer Lett. 2009;283:203–11. doi: 10.1016/j.canlet.2009.03.038. [DOI] [PubMed] [Google Scholar]
- 85.Tatematsu A, Shimizu J, Murakami Y. et al. Epidermal growth factor receptor mutations in small cell lung cancer. Clin Cancer Res. 2008;14:6092–6096. doi: 10.1158/1078-0432.CCR-08-0332. [DOI] [PubMed] [Google Scholar]
- 86.Simbolo M, Mafficini A, O Sikora K. et al. Lung neuroendocrine tumours: deep sequencing of the four World Health Organization histotypes reveals chromatin-remodelling genes as major players and a prognostic role for TERT, RB1, MEN1 and KMT2D. J Pathol. 2017;241:488–500. doi: 10.1002/path.4853. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 87.Umemura S, Mimaki S, Makinoshima H. et al. Therapeutic priority of the PI3K/AKT/mTOR pathway in small cell lung cancers as revealed by a comprehensive genomic analysis. J Thorac Oncol. 2014;9:1324–1331. doi: 10.1097/JTO.0000000000000250. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 88.Dietz S, Harms A, Endris V. et al. Spatial distribution of EGFR and KRAS mutation frequencies correlates with histological growth patterns of lung adenocarcinomas. Int J Cancer. 2017;141:1841–1848. doi: 10.1002/ijc.30881. [DOI] [PubMed] [Google Scholar]
- 89.Nakano H, Soda H, Takasu M. et al. Heterogeneity of epidermal growth factor receptor mutations within a mixed adenocarcinoma lung nodule. Lung Cancer. 2008;60:136–140. doi: 10.1016/j.lungcan.2007.08.021. [DOI] [PubMed] [Google Scholar]
- 90.Zito Marino F, Liguori G, Aquino G. et al. Intratumor Heterogeneity of ALK-Rearrangements and Homogeneity of EGFR-Mutations in Mixed Lung Adenocarcinoma. PLoS One. 2015;10:e0141521. doi: 10.1371/journal.pone.0139264. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 91.Taniguchi K, Okami J, Kodama K. et al. Intratumor heterogeneity of epidermal growth factor receptor mutations in lung cancer and its correlation to the response to gefitinib. Cancer Sci. 2008;99:929–935. doi: 10.1111/j.1349-7006.2008.00782.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 92.Jiang SX, Yamashita K, Yamamoto M. et al. EGFR genetic heterogeneity of nonsmall cell lung cancers contributing to acquired gefitinib resistance. Int J Cancer. 2008;123:2480–2486. doi: 10.1002/ijc.23868. [DOI] [PubMed] [Google Scholar]
- 93.Chen ZY, Zhong WZ, Zhang XC. et al. EGFR Mutation Heterogeneity and the Mixed Response to EGFR Tyrosine Kinase Inhibitors of Lung Adenocarcinomas. Oncologist. 2012;17:978–985. doi: 10.1634/theoncologist.2011-0385. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 94.Gow CH, Chang YL, Hsu YC. et al. Comparison of epidermal growth factor receptor mutations between primary and corresponding metastatic tumors in tyrosine kinase inhibitor-naive non-small-cell lung cancer. Ann Oncol. 2009;20:696–702. doi: 10.1093/annonc/mdn679. [DOI] [PubMed] [Google Scholar]
- 95.Kalikaki A, Koutsopoulos A, Trypaki M. et al. Comparison of EGFR and K-RAS gene status between primary tumours and corresponding metastases in NSCLC. Br J Cancer. 2008;99:923–9. doi: 10.1038/sj.bjc.6604629. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 96.Monaco SE, Nikiforova MN, Cieply K. et al. Teot LA, Khalbuss WE, Dacic S. A comparison of EGFR and KRAS status in primary lung carcinoma and matched metastases. Hum Pathol. 2010;41:94–102. doi: 10.1016/j.humpath.2009.06.019. [DOI] [PubMed] [Google Scholar]
- 97.Kim H, Xu X, Yoo SB. et al. Discordance between anaplastic lymphoma kinase status in primary non-small-cell lung cancers and their corresponding metastases. Histopathology. 2013;62:305–14. doi: 10.1111/j.1365-2559.2012.04356.x. [DOI] [PubMed] [Google Scholar]
- 98.Wu C, Zhao C, Yang Y. et al. High discrepancy of driver mutations in patients with NSCLC and synchronous multiple lung ground-glass nodules. J Thorac Oncol. 2015;10:778–83. doi: 10.1097/JTO.0000000000000487. [DOI] [PubMed] [Google Scholar]
- 99.Abe H, Kawahara A, Azuma K. et al. Heterogeneity of anaplastic lymphoma kinase gene rearrangement in non small cell lung carcinomas: a comparative study between small biopsy and excision samples. J Thorac Oncol. 2015;10:800–5. doi: 10.1097/JTO.0000000000000507. [DOI] [PubMed] [Google Scholar]
- 100.Park S, Holmes-Tisch AJ, Cho EY. et al. Discordance of molecular biomarkers associated with epidermal growth factor receptor pathway between primary tumors and lymph node metastasis in non-small cell lung cancer. J Thorac Oncol. 2009;4:809–15. doi: 10.1097/JTO.0b013e3181a94af4. [DOI] [PubMed] [Google Scholar]
- 101.Hiley CT, Le Quesne J, Santis G. et al. Challenges in molecular testing in non-small-cell lung cancer patients with advanced disease. Lancet. 2016;388:1002–11. doi: 10.1016/S0140-6736(16)31340-X. [DOI] [PubMed] [Google Scholar]
- 102.Matsumoto S, Takahashi K, Iwakawa R. et al. Frequent EGFR mutations in brain metastases of lung adenocarcinoma. Int J Cancer. 2006;119:1491–1494. doi: 10.1002/ijc.21940. [DOI] [PubMed] [Google Scholar]
- 103.Wang S, Wang Z. Meta-analysis of epidermal growth factor receptor and KRAS gene status between primary and corresponding metastatic tumours of non-small cell lung cancer. Clin Oncol (R Coll Radiol) 2015;27:30–9. doi: 10.1016/j.clon.2014.09.014. [DOI] [PubMed] [Google Scholar]
- 104.Han HS, Eom DW, Kim JH. et al. EGFR mutation status in primary lung adenocarcinomas and corresponding metastatic lesions: discordance in pleural metastases. Clin Lung Cancer. 2011;12:380–386. doi: 10.1016/j.cllc.2011.02.006. [DOI] [PubMed] [Google Scholar]
- 105.Kim H, Xu X, Yoo SB. et al. Discordance between anaplastic lymphoma kinase status in primary non-small-cell lung cancers and their corresponding metastases. Histopathology. 2013;62:305–14. doi: 10.1111/j.1365-2559.2012.04356.x. [DOI] [PubMed] [Google Scholar]
- 106.Dong ZY, Zhai HR, Hou QY. et al. Mixed Responses to Systemic Therapy Revealed Potential Genetic Heterogeneity and Poor Survival in Patients with Non-Small Cell Lung Cancer. Oncologist. 2017;22:61–69. doi: 10.1634/theoncologist.2016-0150. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 107.Hudson AM, Wirth C, Stephenson NL. et al. Using large-scale genomics data to identify driver mutations in lung cancer: Methods and challenges. Pharmacogenomics. 2015;16:1149–60. doi: 10.2217/pgs.15.60. [DOI] [PubMed] [Google Scholar]
- 108.Dias M, Linhas R, Campainha S. et al. Lung cancer in never-smokers - what are the differences? Acta Oncologica. 2017;7:931–935. doi: 10.1080/0284186X.2017.1287944. [DOI] [PubMed] [Google Scholar]
- 109.Choi JR, Park SY, Noh OK. et al. Gene mutation discovery research of non-smoking lung cancer patients due to indoor radon exposure. Ann Occup Environ Med. 2016;28:13. doi: 10.1186/s40557-016-0095-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 110.Wakelee HA, Chang ET, Gomez SL. et al. Lung cancer incidence in never smokers. J Clin Oncol. 2007;25:472. doi: 10.1200/JCO.2006.07.2983. [DOI] [PMC free article] [PubMed] [Google Scholar]