IDENTIFICATION AND CLONING OF HUMAN G-PROTEIN GAMMA-7, DOWN-REGULATEDIN PANCREATIC-CANCER

Differentially expressed genes between normal and cancer tissues of th e pancreas were investigated using differential display. Consequently, we identified a fragment cDNA that was expressed in the normal tissue but was rarely expressed in the cancer tissue. This cDNA was screened in cDNA library prepared from the normal pancreatic tissue by rapid a mplification of cDNA ends (5'RACE), 859 bp of cDNA was cloned and sequ enced, and the inferred amino acid sequence was found to encode a G pr otein gamma subunit with 98% homology to cow G protein gamma 7 and com plete homology to human G protein gamma 7. The decreased expression of the G protein gamma 7 was confirmed by Northern blot assay in twelve pancreatic malignancies which included nine duct cell carcinomas, two cystoadenocarcinomas and one blastoma. Reverse transcriptase (RT) poly merase chain reaction (PCR) assay showed no expression of G protein ga mma 7 in five of six pancreatic carcinoma cell lines and two pancreati c cancer tissues. Immunohistochemistry analysis also displayed positiv e staining in the normal tissue but no staining in the cancer tissue. The findings demonstrated that the reduced or suppressed expression of human G-protein gamma 7 may play an important role in pancreatic carc inogenesis. (C) 1998 Academic Press.