Human colorectal carcinomas specifically accumulate Mr 42,000 ubiquitin-conjugated cytokeratin 8 fragments

H Nishibori, Y Matsuno, M Iwaya, T Osada, N Kubomura, A Iwamatsu, H Kohno, S Sato, M Kitajima, S Hirohashi
1996 Cancer Research  
Recent studies have shown that various tumor cells accumulate ubiquitin (Ub)-conjugated proteins, the profiles of which differ from those of normal cells. To identify the Ub-conjugated proteins accumulated specifically by human carcinoma cells, a two-dimensional immunoblot analysis of 31 surgically resected human primary colorectal carcinoma tissues was performed using an anti-Ub monoclonal antibody, KM691. Two distinct Mr 42,000 and 45,000 proteins in the Triton X-insoluble fractions of
more » ... ma tissues reacted with this antibody, whereas only one Mr 45,000 protein reacted in normal tissues. The Mr 42,000 Ub-conjugated proteins were specific to carcinoma tissues from 25 patients (80.6%). One of the purified Mr 42,000 proteins was digested with Achromobacter protease I. This protein was identified as a cytokeratin 8 (CK 8) fragment based on both molecular mass determination and molecular mass searching of Achromobacter protease I-digested fragments of proteins registered in a protein sequence data base. Two-dimensional immunoblot analysis with an anti-CK 8 antibody confirmed that all of the Mr 42,000 proteins were CK 8 degradation products. These results demonstrate that human colorectal carcinomas specifically accumulate Mr 42,000 Ub-conjugated CK 8 fragments. This accumulation was observed frequently not only in advanced (18/22, 81.8%), but also in early stage cases (7/9, 77.8%), suggesting that it occurs even in the early stages of colorectal carcinoma progression.
pmid:8665509 fatcat:pv2sjgoi25csppbbzgrrzlrcda