Table 3.
Current biomarkers for CRC.
| Molecular Marker Type | Biomarker | Contribution to Cancer | Predictive Use | Samples Used for the Test | Status | References |
|---|---|---|---|---|---|---|
| DNA | Microsatellite instability (MSI) test. Panel of mononucleotide marker (Bat-25, Bat-26, NR-21, NR-24, MONO-27), ≥30% of unstable loci are considered MSI tumours. | Accumulation of alteration in highly repeated DNA sequences | For MSI+ tumours: Prognosis: good, aggressively: low, treatment: lack of response to 5-FU, good response to irinotecan | Tumour-based samples | In use | [183,184,185] |
| - | KRAS, NRAS | Proliferation enhancement through EGFR-signalling activation | If mutated: Prognosis: bad and poor survival (codon 12 and 13). Treatment: limited response to EGFR | Tumour-based samples, stool | In use for tumour-based samples and under evaluation for stool | [186,187,188] |
| BRAF | Proliferation enhancement through EGFR-signalling activation | If mutated: Classification of CRC: sporadic, Prognosis: poor, Treatment: limited response to EGFR-targeted therapy. | Tumour-based samples | In use | [189,190,191] | |
| CpG Island Methylator Phenotype. e.g., Vimentin methylation. | Transcriptional regulation which lead to colorectal carcinogenesis | Classification of CRC in CIMP, Presence of BRAF mutations | Tumour-based samples, stool, blood samples | Under evaluation in tumour samples and in use for stool | [192,193] | |
| Integrity of cell-free DNA (cfDNA) | Apoptosis | Diagnosis and monitoring | Blood sample | Under evaluation | [194] | |
| RNA | gene microarray and gene panels of RNA | Unknown | CRC diagnosis evaluation of relapse risk | Tumour-based samples, stool, blood | Clinical validation | [195,196] |
| miRNA biomarker panel. e.g., miR-21, miR-106a | Unknown | Diagnosis and prognosis | Tumour-based samples, stool, blood | Clinical validation | [197,198] | |
| EGFR ligand biomarker panel (amphiregulin, epiregulin, DUSP6 and SLC26A3) | Proliferation enhancement through EGFR-signalling activation | Response to EGFR-targeted therapy | Tumour-based samples | Under evaluation | [199,200,201] | |
| Protein | Tumour-specific protein determination. e.g., Calprotectin, CEA, DAF, CA19-9 | Unknown | Diagnosis, prognosis, monitoring | Stool, blood | Clinical validation | [202,203,204,205,206] |
| Others | Circulating nucleic acids, proteins and tumour cells | Unknown | Diagnosis, monitoring | Blood | Clinical validation | [207,208,209] |