Biomarkers of Barrett's esophagus

Table 1 Phases of biomarker production

Phases of biomarker validation and development

Phase 1: Biomarkers of promise are identified based on application in other cancers and elucidation of novel pathways

Phase 2: Cross-sectional studies validate the biomarker of interest to be sufficiently discriminatory and biomarker assays are standardized

Phase 3: Case-control studies with a retrospective but longitudinal design confirm the biomarker is expressed before the development of cancer

Phase 4: Prospective longitudinal studies avoid biases associated with case-control studies

Phase 5: Population-based studies show the impact of biomarker detection on disease burden and cancer control

Table 2 Types of biomarkers in Barrett’s esophagus

	Biomarker	Method	Remarks	Ref.
Diagnostic	TFF3	IHC	To screen asymptomatic patients for BE	[49,50]
	Chromosome 7 and 17 changes	IDKA and FISH	Early stages of BE	[52]
	8q24 (C-MYC), 17q12 (HER2), and 20q13 changes	FISH	Early stages of BE	[53]
	17q11.2 (ERBB2)	Microarray analysis	EAC	[54]
	Serum proteomic analysis	Mass spectrometry	EAC	[55]
Predictive	P16 allelic loss	FISH	Response to therapy	[56]
	DNA ploidy abnormalities	ICDA	Covariate value for recurrence	[57]
	HSP27	IHC	No response to therapy	[58]
	Ephrin B receptor	Microarray	Response to therapy in EAC	[59]
	Genetic polymorphism	qRT-PCR	Associated with clinical outcome	[60]
	P21	IHC	Correlated with better CTX response	[61]
	P53	IHC	Correlated with better CTX response	[62]
Progression markers	ERCC1	IHC	Predicts CTX resistance	[16]
	P53	IHC	Limited efficacy as a progression marker	[13,63]
	DNA abnormalities	Flow cytometry	High risk for progression to EAC	[13]
	LOH of 157p and 9p	Flow cytometry	Predict progression to EAC	[14]
	EGFR	IHC	Overexpression in HGD and EAC	[64]
	Cyclin A	IHC	Predicts progression to dysplasia	[65]
	Cyclin D1	IHC	Risk of Progression to EAC	[19]
	Hypermethylation of p16, RUNX2,HPP1	RT-PCR	Risk of progression to EAC/HGD	[22]
	8 gene methylation panel	RT-PCR	Predicts progression to EAC/HGD	[66]
Prognostic biomarkers	Cathepsin D,AKR1D10,AKR1C2 mRNA levels	Western blot, qRt-PCR	Dysregulation predicts progression to EAC/HGD	[67]
	DCK, PAPSS2, SIRT,TRIM44	RT-PCR, IHC	4 gene signature in EAC , predict 5 year survival	[56]
	P16 loss, C-MYC gain	FISH	Associated with therapy response	[68]
	ASS expression	Microarray	Low expression associated with metastases	[69]
	MicroRNA expression profile	Microarray, RT-PCR	Low level associated with worse prognosis in EAC	[70]
	Cyclin D1	IHC, FISH	Decreased survival	[71]
	EGFR	IHC	Decreased expression associated with decreased survival	[72]
	TGF-α	IHC, ISH	High level indicates progression and metastases	[73]
	TGF-β1	RT-PCR, ELISA	High expression associated with decreased survival	[73]
	APC	PCR	High level associated with decreased survival	[74]
	COX-2	IHC	Associated with metastases and recurrence	[75]
	Telomerase	Southern-blot and PCR	Associated with decreased survival	[76]
	VEGF	IHC	Associated with metastases and decreased survival	[77]
	Cadherin	IHC	Decreased level associated with decreased survival	[78]
	TIMP	IHC, PCR	Decreased level associated with decreased survival	[79]

ACIS: Automated cellular imaging system; ASS: Argininosuccinate synthase; APC: Adenomatous polyposis coli; BE: Barrett’s esophagus; COX: Cyclooxygenase; DCK: Deoxycytidine kinase; DICM: Digital image cytometry; EAC: Esophageal adenocarcinoma; EGFR: Epidermal growth factor receptor; ELISA: Enzymelinked immunosorbent assay; FISH: Fluorescence in-situ-hybridization; ICDA: Image cytometric DNA analysis; HSP27: Heat-shock protein 27; IHC: Immunohistochemistry; LOH: Loss of heterozygosity; PAPSS2: 3'-phosphoadenosine 5'-phosphosulfate synthase 2; PCR: Polymerase chain reaction; qRT: Quantitative reverse transcriptase; MLPA: Multiplex ligation dependent probe amplification; NF-κB: Nuclear factor kappa B; SIRT2: Sirtuin 2; SNP: Single nucleotide polymorphism; TFF3: Trefoil factor 3; TGF: Transforming growth factor; TIMP: Tissue inhibitors of metalloproteinases; TRIM44: Tripartite motifcontaining 44; uPA: Urokinase-type plasminogen activator; VEGF: Vascular endothelial growth factor.