Human colorectal carcinomas specifically accumulate Mr 42,000 ubiquitin-conjugated cytokeratin 8 fragments.
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 carcinoma 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.
Nishibori
H
H
Pathology Division, National Cancer Center Research Institute, Tokyo.
Matsuno
Y
Y
Iwaya
M
M
Osada
T
T
Kubomura
N
N
Iwamatsu
A
A
Kohno
H
H
Sato
S
S
Kitajima
M
M
Hirohashi
S
S
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D001483:Base Sequence; D003110:Colonic Neoplasms / Q000378:metabolism*; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007633:Keratins / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000378:metabolism*; D012004:Rectal Neoplasms / Q000378:metabolism*; D012811:Sigmoid Neoplasms / Q000378:metabolism*; D014452:Ubiquitins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D009363:Neoplasm Proteins; D014452:Ubiquitins; D007633:Keratins