New trends in molecular and cellular biomarker discovery for colorectal cancer

Table 1 Associated biomarkers for colorectal cancer and their predictive value

Biomarkers		Molecular basis	Predictive value	Detection method
Category	Type
Pathological characteristics	Tumor stage		Diagnostic, prognostic and predictive markers	Diagnostic radiology and pathological/cytological examination
	Lymph node status
	Grade of differentiation
	Anatomy of invasion
Proliferation markers	Ki67	Nuclear antigen associated with proliferation	Diagnostic and prognostic markers	IHC
	Cyclins	Regulation of cell cycle phase transition	Diagnostic and prognostic markers	IHC
Chromosome abnormalities	p53	Tumor suppressor gene which shows loss of function	Diagnostic, prognostic and predictive markers	IHC, RT-PCR, FISH
	H-ras, K-ras, N-ras	Membrane-associated GTPase integral to signal transduction cascade, if mutated, causes increased cellular proliferation	Diagnostic, prognostic and predictive markers	IHC, RT-PCR, FISH
	Telomere length	Pathologic telomere length dynamics	Diagnostic and prognostic markers	RT-PCR, Flow cytometry
	Telomerase activity	Maintenance of telomeres and therefore chromosomal length	Diagnostic and prognostic markers	TRAP assay
		enables progression through successive cell cycles
Hypoxia-regulated genes	HIF-1	HIF-1 transcription factor complex stabilized in hypoxic conditions, leading to transcription of hypoxia-regulated genes	Diagnostic and prognostic markers	IHC
	Glut-1	Increased Glut-1 expression caused by malignant transformation and upregulated by hypoxia. Promotes switch to anaerobic glycolysis to support hypoxic tumor	Diagnostic and prognostic markers	IHC
Angiogenesis	VEGF	Angiogenic growth factor	Prognostic and predictive markers	IHC, FISH, immunoassay
	PD-ECGF	Angiogenic growth factor with thymidine phosphorylase activity	Prognostic and predictive markers	IHC
	Vascularity	New vasculature supports tumor growth	Prognostic and predictive markers	IHC staining for endothelial receptors e.g., CD31, CD34, von Willebrand (factor VIII) combined with measurement of ICD or MVD using digital image analysis techniques
Epigenetics	Aberrant DNA hypermethylation	Inactivation of key tumor suppressor genes including APC, ATM, BMP3, CDKN2A, SFRP2, GATA4, GSTP1, HLTF, MLH1, MGMT, NDRG4, RASSF2A, SFRP2, TFPI2, VIM, and WIF1	Diagnostic, prognostic and predictive markers	PCR-based methods and Pyrosequencing
	Aberrant DNA hypomethylation	Lids to chromosomal instability and global loss of imprinting	Diagnostic and prognostic markers	PCR based methods and Pyrosequencing
Tumor specific expression patterns	Gene expression patterns	Unique signature of the dysregulated genes/pathways at different forms and stages of CRC	Diagnostic, prognostic and predictive markers	Array-based methods, NGS, RT-PCR
	MicroRNA expression patterns	Unique signature of the dysregulated microRNAs at different forms and stages of CRC	Diagnostic, prognostic and predictive markers	Array-based methods, NGS, RT-PCR

FISH: Fluorescent in-situ hybridization; HIF-1: Hypoxia inducible factor-1; HPLC: High pressure liquid chromatography; ICD: Intercapillary distance; IGF-1: Insulin growth factor-1; IHC: Immunohistochemistry; MVD: Microvessel density; NGS: Next generation sequencing; PD-ECGF: Plateletderived endothelial cell growth factor; RT-PCR: Reverse transcription–polymerase chain reaction; RIA: Radioimmunoassay; VEGF: Vascular endothelial growth factor.