c-MET immunohistochemical expression in sporadic and inflammatory bowel disease associated lesions

BACKGROUND Post-colonoscopy colorectal cancer(CRC)rates for patients with inflammatory bowel disease(IBD)are unacceptably high.During colonoscopy,an intravenous fluorescent anti-c-MET probe may improve endoscopic detection of lesions.However,c-MET expression in IBD lesions is poorly defined,limiting translational studies.AIM To comprehensively define c-MET expression in sporadic and IBD-associated colorectal carcinogenesis.METHODS c-MET expression was immunohistochemically assessed in 319 formalin-fixed paraffin-embedded tissue specimens,colonoscopically or surgically retrieved between 1994-2017.Tissue included:30 normal colorectal biopsies,30 hyperplastic polyps(HP),31 sessile serrated lesions(SSL),55 tubular/tubulovillous adenomas with low(TA-LGD,n=32)or high grade dysplasia(TA-HGD,n=23),26 sporadic(s)-CRCs,16 quiescent IBD biopsies,11 active/inflamed IBD biopsies,18 IBDassociated dysplastic lesions(IBD-dys),and 102 IBD-CRCs.Expression was scored by two independent observers as:0=absent,1=weak,2=moderate or 3=strong.Mann-Whitney U and Kruskal-Wallis tests were used to assess significance.RESULTS Positive epithelial cytoplasmic and membranous c-MET expression was observed in all tissues,indicating there is ubiquitous expression in the colorectum.c-MET expression was weak in normal colonic epithelium compared with each of the sporadic colonic lesions,including TA-LGD(P<0.001),TA-HGD(P=0.004),HP(P<0.001),SSL(P<0.001),and s-CRC(P<0.001).Specifically,in sporadic(non-IBD)lesions,expression was stronger in TA-LGD compared with normal mucosa(P<0.001),and stronger in s-CRC compared with TA-HGD(P=0.004).However,there was no significant difference between TA-LGD and TA-HGD(P=0.852).Further,there was no difference in c-MET expression between HP and SSL(P=0.065).In IBD,expression was weaker in quiescent colonic mucosa compared with inflamed colonic mucosa(P<0.001).There was no difference between inflamed colonic mucosa and IBD-dys(P=0.512)or IBD-CRC(P=0.296).However,expression was stronger in IBD-dys(P<0.001)and IBD-CRC(P<0.001)compared with quiescent IBD colonic mucosa.CONCLUSION The characterisation of c-MET expression suggest that an intravenous probe may improve the endoscopic detection of lesions in both non-IBD patients and IBD patients with quiescent disease.