CATHEPSIN-B AND TUMOR-ASSOCIATED LAMININ EXPRESSION IN THE PROGRESSION OF COLORECTAL ADENOMA TO CARCINOMA

Cathepsin B is a lysosomal cysteine proteinase associated with degrada tion of laminin. It is increased in colorectal carcinoma (CA), Laminin is a major component of basement membrane involved in cell-matrix int eractions and tumor progression. The aim of this study was to correlat e cathepsin B and tumor-associated laminin in colorectal adenomas (ADs ) with increasing grades of dysplasia and in invasive CAs. Forty-five ADs (8 tubular, 16 tubulovillous, 21 villous), 13 adenomas with high-g rade dysplasia/carcinoma irt situ (AHDs), and 17 invasive CAs were imm unostained with polyclonal antibodies to cathepsin B and laminin. Stat istical analysis was performed using exact linear by Linear associatio n test and Spearman rank correlation coefficient. Cathepsin B-positive tumor cells were seen in 30 (67%) ADs, 13 (100%) AHDs, and 17 (100%) CAs, The grade of cathepsin B staining was significantly increased in AHDs and CAs, compared with ADs (P <.0001). Laminin was continuous in all of the ADs and discontinuous or fragmented in the AHDs and CAs (P <.0001), The degree of cathepsin B staining in tumor cells also correl ated with breakdown of laminin. Increased cathepsin B expression and d ecrease in tumor-associated laminin might suggest a mechanism for prog ression of ADs to CAs.