Abstract
Purpose
Hepatocellular carcinoma (HCC) is among the leading causes of cancer-related deaths with a very poor prognosis. Consequently, there is an urgent need for better understanding the molecular mechanisms, novel prognostic biomarkers, and more effective treatment options. There is an emerging link between oxytocin (OXT), the oxytocin receptor (OXTR), and cancer. However, the role of OXT or the OXTR in HCC remains unknown. The research question of this study was: Are there genetic alterations in the oxytocin (OXT) and oxytocin receptor (OXTR) genes in hepatocellular carcinoma (HCC) patients and do these alterations impact overall survival and disease-free survival.
Methods
In this retrospective study, we reviewed 360 individual HCC patient data from The Cancer Genome Atlas (TCGA) using cBioPortal accessed in April 2018. The data in The Cancer Genome Atlas are from various institutions in the United States
Results
We found that 3% (11 of 360) of cases showed genetic alterations in the OXTR gene. The median months survival was lower for HCC cases with genetic alterations in the OXTR gene as compared to cases without genetic alteration in this gene (33.0 versus 60.84, respectively. Additionally, the median months disease-free survival was lower in cases with genetic alterations in the OXTR gene as compared to cases without alterations (8.64 versus 21.55, respectively).
Conclusions
OXTR is a promising prognostic biomarker for HCC, and OXTR antagonists could have a future role as therapeutic agents for a subset of HCC patients. Further study of the detailed molecular mechanisms of OXT and OXTR in HCC is warranted.
Keywords: oxytocin receptor, hepatocellular carcinoma, genetic alteration, oxytocin
Introduction
Hepatocellular carcinoma (HCC) is the sixth most common cancer and the second leading cause of cancer-related deaths worldwide [1]. It is also the most common primary malignancy of the liver. HCC is often detected at advanced stages and most patients will therefore need systemic therapy, such as sorafenib. However, sorafenib therapy only minimally enhances patient survival. Due to the poor prognosis for HCC patients, the detailed molecular mechanisms of the disease need to be better understood to aid discovery of prognostic biomarkers and more effective therapeutic strategies.
Oxytocin is a nine-amino acid peptide hormone, synthesized mainly in the hypothalamus and secreted into the blood stream as an inactive precursor protein from the OXT gene and is activated upon binding to its G-protein coupled receptor, the oxytocin receptor (OXTR) [2]. OXT is traditionally mostly known for playing roles in the female reproductive system during pregnancy and lactation. However, newer studies have shown it to play roles in the male reproductive system as well. Even further, it has been shown to play important roles in stress, trust, anxiety, social interaction and bonding, and parental care [3, 4], and consequently on the neuropsychiatric disorders linked to these social behaviors. More recently, emerging evidence has linked OXT and OXTR to roles in various cancer [4]. Recent findings have shown that OXT promotes cell proliferation in breast, prostate, osteosarcoma, and lung cancers [5, 6]. To promote cell proliferation, OXT binds to its receptor which results in MAPK cascade activation, leading to transient ERK1/2 phosphorylation and cell proliferation [2]. While it is known that OXTR is expressed in liver tissues where it likely plays roles in regulating glycogen levels[7], a role for OXT and OXTR in HCC have not been reported to date.
Genetic alterations in several genes encoding proteins have been implicated in HCC pathogenesis. These include P53, P16, P73, APC, PTEN, IGF-2, BRCA2, SMAD2, SOCS, beta-catenin, retinoblastoma proteins, c-myc and cyclin D1 proteins [8, 9]. Additionally, several signaling pathways are known to be involved in HCC development including MAPK pathway activation via the Ras protein leading to ERK1/2 activation and ultimately proliferation [8]. To our knowledge, no previous studies have tried to explore the correlation of OXT or OXTR genetic alterations and clinical features in HCC. This study aimed to assess the genetic alterations of OXT or OXTR and its correlation with overall survival and disease-free progression in HCC using data from The Cancer Genome Atlas (TCGA).
Methods
In this study, the cBioPortal for Cancer Genomics online analysis tool was used to analyze the genetic alterations (mutations, copy-number alterations, mRNA expression, protein expression in the OXT and OXTR genes in the cancer study “Liver Hepatocellular Carcinoma) using data from TCGA. The genes “OXT” and “OXTR” were entered into the input box. The data type priority “Mutation”, “CNA (DNA copy-number alterations)”, “mRNA expression” and “Protein expression” were selected. Clinical information of each patient with OXTR genetic alterations were also retrieved and presented in Table 1.
Table 1.
Clinical characteristics of TCGA patients with OXTR genetic alterations in HCC.
| Patient No. |
Genetic alteration |
Gender | Race | Ethnicity | HCC risk factor | Disease-free status | Disease-free (Months) |
Diagnosis age (Years) |
Disease stage |
|---|---|---|---|---|---|---|---|---|---|
| 1 | OXTR | F | White | Not Hispanic | None | Recurred/Progressed | 11.17 | 72 | NA |
| 2 | OXTR | F | Asian | Not Hispanic | NA | NA | NA | 61 | Stage IIIC |
| 3 | OXTR | F | White | Not Hispanic | None | Recurred/Progressed | 8.64 | 71 | Stage IIIC |
| 4 | OXTR | F | White | Not Hispanic | Hepatitis C | Recurred/Progressed | 14.85 | 45 | Stage IIIA |
| 5 | OXTR | M | Asian | Not Hispanic | Alcohol Consumption |
Recurred/Progressed | 8.57 | 61 | Stage IIIA |
| 6 | OXTR | F | White | Not Hispanic | None | Recurred/Progressed | 5.22 | 76 | Stage II |
| 7 | OXTR | F | White | Not Hispanic | Alcohol consumption |
Recurred/Progressed | 35.84 | 61 | Stage I |
| 8 | OXTR | F | Asian | Not Hispanic | None | NA | NA | 51 | Stage IIIA |
| 9 | OXTR | M | Black | Not Hispanic | Hepatitis B | Recurred/Progressed | 2.89 | 48 | Stage II |
| 10 | OXTR | F | Asian | Not Hispanic | None | Disease Free | 13.4 | 60 | Stage IIIA |
| 11 | OXTR | F | White | Not Hispanic | None | NA | NA | 81 | Stage I |
Abbreviations: F, female, M, male, NA, not applicable (data unavailable), TCGA, The Cancer Genome Atlas.
For survival analysis, Kaplan-Meier plots with a log rank test were performed to compare the overall survival and the disease-free survival of HCC with at least one alteration or without alteration in query gene(s). Samples with over-expression were identified by a threshold of Z>2 (mean expression over 2 SDs). The a level was set at 0.05.
Results
It was found that 1.7% (6 out of 360) and 3.0% (11 out of 360) of the sequenced tissues from the HCC cases have genetic alterations in the OXT and OXTR genes, respectively. The OXT genetic alterations were amplification (1 case) and mRNA upregulation (5 cases) and the OXTR genetic alterations were either missense mutation (1 case), amplification (2 cases), or mRNA upregulation (9 cases). The median months survival was 33.02 for HCC cases with genetic alterations in the OXTR gene and 60.84 for cases without such alterations. Overall survival data was not available for the OXT gene. The median months disease-free was 8.64 for cases with alterations and 21.55 for cases without alterations in the OXTR gene as shown in Figure 2. Table 1 shows the clinical features of each patient with either OXT or OXTR genetic alterations.
Figure 2. Progression-free Kaplan-Meier estimate in hepatocellular carcinoma.
The median months disease-free was 8.64 for cases with alterations (mutations, copy-number alterations, mRNA expression, protein expression and 21.55 for cases without alterations in the OXTR gene.
Discussion
To our knowledge, this is the first study to explore OXTR genetic alterations in HCC. Our analyses revealed that patients with genetic alterations in the OXTR gene have significantly poorer survival outcomes.
Amico and colleagues had shown the presence of OXT in human pancreatic extracts which suggested the possibility of local synthesis of oxytocin especially since OXT is known to be an endocrine mediator of insulin and glucagon release[10]. There is also the possibility of OXT from the pancreas having local effect on the liver, due to the proximity of these two organs. Importantly, OXT is a systemic hormone that could expectedly have widespread effects on all body organs, including the liver.
Unpublished data from our laboratory indicates that OXTR mRNA and protein overexpression is associated with human pancreatic cancer cell resistance to the chemotherapeutic agent gemcitabine. Thus, OXTR may play a role in pancreatic cancer chemoresistance. Given that HCC patients with OXTR genetic alterations have poorer survival outcomes than those without OXTR genetic alterations, it is possible that OXTR plays a role in HCC chemoresistance as well. Consequently, it would be important to conduct future studies to evaluate OXTR genetic alterations in a large cohort of HCC patients with varying responsiveness to sorafenib.
HCC cases with genetic alterations in the OXTR gene showed significantly lower median months survival as well as progression-free survival as compared to cases without OXTR gene alterations. These findings indicate the need for future experiments to elucidate the detailed molecular mechanisms of OXT and OXTR signaling in HCC. Notably, HCC cases with alterations in OXT had progression-free median months survival of 55.06 versus 20.99 for HCC cases without OXT gene alterations. However, it is important to note that only 6 out of 360 (1.7%) HCC patients in this entire cohort had OXT gene alterations. Future studies are needed to further determine the clinical implications of this finding. The current data, nevertheless, suggests that OXT likely plays a different role from OXTR in HCC. It is critical that future studies clarify what these disparate roles and their underlying molecular mechanisms are.
Conclusions
Clearly, OXTR is a promising prognostic biomarker in HCC, and it is possible that OXTR antagonists could serve as therapeutic agents and be beneficial to a subset of HCC patients. Further investigation of the detailed molecular mechanisms of OXT and OXTR in HCC is warranted.
Figure 1. Overall survival Kaplan-Meier estimate in hepatocellular carcinoma.
The median months survival was 33.02 for cases with alterations (mutations, copy-number alterations, mRNA expression, protein expression and 60.84 for cases without alterations in the OXTR gene.
Acknowledgements
Funding/Support: Dr. Ogunwobi is supported by the National Cancer Institute grant number 1 U54 CA221704–01A1.
Footnotes
Conflict of Interest:
Olorunseun O. Ogunwobi is a Co-Founder of NucleoBio, Inc, a City University of New York start-up biotechnology company. There are no conflicts of interest relevant to this article.
Ethical approval:
Analysis was performed using publicly available deidentified data from The Cancer Genome Atlas. Ethical approval was unnecessary for this analysis.
Informed consent:
There was no interaction with human subjects or identifiable human subjects information. Hence, informed consent was unnecessary for this analysis.
Publisher's Disclaimer: This Author Accepted Manuscript is a PDF file of a an unedited peer-reviewed manuscript that has been accepted for publication but has not been copyedited or corrected. The official version of record that is published in the journal is kept up to date and so may therefore differ from this version.
References
- 1.Tang A, Hallouch O, Chernyak V, Kamaya A, Sirlin CB. Epidemiology of hepatocellular carcinoma: target population for surveillance and diagnosis. Abdominal radiology (New York). 2018;43(1):13–25. doi: 10.1007/s00261-017-1209-1. [DOI] [PubMed] [Google Scholar]
- 2.Imanieh MH, Bagheri F, Alizadeh AM, Ashkani-Esfahani S. Oxytocin has therapeutic effects on cancer, a hypothesis. European journal of pharmacology. 2014;741:112–23. doi: 10.1016/j.ejphar.2014.07.053. [DOI] [PubMed] [Google Scholar]
- 3.Lopatina O, Inzhutova A, Salmina AB, Higashida H. The roles of oxytocin and CD38 in social or parental behaviors. Front Neurosci. 2012;6:182. doi: 10.3389/fnins.2012.00182. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Lerman B, Harricharran T, Ogunwobi OO. Oxytocin and cancer: An emerging link. World J Clin Oncol. 2018;9(5):74–82. doi: 10.5306/wjco.v9.i5.74. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Taylor AH, Ang VT, Jenkins JS, Silverlight JJ, Coombes RC, Luqmani YA. Interaction of vasopressin and oxytocin with human breast carcinoma cells. Cancer research. 1990;50(24):7882–6. [PubMed] [Google Scholar]
- 6.Whittington K, Connors B, King K, Assinder S, Hogarth K, Nicholson H. The effect of oxytocin on cell proliferation in the human prostate is modulated by gonadal steroids: implications for benign prostatic hyperplasia and carcinoma of the prostate. The Prostate. 2007;67(10):1132–42. doi: 10.1002/pros.20612. [DOI] [PubMed] [Google Scholar]
- 7.Tribollet E, Dubois-Dauphin M, Dreifuss JJ, Barberis C, Jard S. Oxytocin receptors in the central nervous system. Distribution, development, and species differences. Annals of the New York Academy of Sciences. 1992;652:29–38. [DOI] [PubMed] [Google Scholar]
- 8.Daher S, Massarwa M, Benson AA, Khoury T. Current and Future Treatment of Hepatocellular Carcinoma: An Updated Comprehensive Review. J Clin Transl Hepatol. 2018;6(1):69–78. doi: 10.14218/JCTH.2017.00031. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Villanueva A Hepatocellular Carcinoma. The New England journal of medicine. 2019;380(15):1450–62. doi: 10.1056/NEJMra1713263. [DOI] [PubMed] [Google Scholar]
- 10.Amico JA, Finn FM, Haldar J. Oxytocin and vasopressin are present in human and rat pancreas. The American journal of the medical sciences. 1988. 296(5):303–7. [DOI] [PubMed] [Google Scholar]