Ubiquitin hybrid protein gene expression during human colon cancer progression
K. Mafune, J. M. Wong, R. J. Staniunas, M. L. Lu, T. S. Ravikumar, L. B. Chen and G. D. Steele Jr
Department of Surgery, New England Deaconess Hospital, Boston, MA 02215.
Ubiquitin is involved in cell-cycle control and DNA replication through a
specific proteolytic pathway. Our previous studies demonstrated selected
higher expression of a gene encoding ubiquitin-ribosomal protein S27a in
poorly differentiated colon carcinoma cell lines. In this study, we
evaluated this ubiquitin hybrid protein gene expression in surgical
specimens of colon cancers. Northern blot analysis showed that ubiquitin
hybrid protein messenger RNA was overexpressed in primary colon cancers
compared with adjacent normal colon mucosae in 17 of 20 patients. Dot blot
analysis of RNA of 27 tumor samples revealed significantly greater
expression in higher Dukes' stage primary colon tumors and liver
metastases. These data imply that protein translation machinery is highly
activated during progression and metastasis of colon tumors, and that
ubiquitin hybrid protein may be useful as a marker of biological
aggressiveness.
