RETINOBLASTOMA GENE STRUCTURE AND PRODUCT EXPRESSION IN HUMAN GASTRICCARCINOMAS

The role of the retinoblastoma gene (RB1) in human gastric carcinogene sis is yet to be clarified. We report on the analysis of RB1 structure and protein (pRB) expression in gastric carcinomas using Southern blo tting, Western blotting and immunohistochemistry. The relationship bet ween pRB expression and cell proliferation was assessed by a prolifera tion marker (PCNA) in a subset of cases. Non-neoplastic mucosas were s tudied, as controls, by the same methodology. We found a close relatio nship between pRB expression and PCNA in non-neoplastic mucosas as wel l as in gastric carcinomas. All tumours were immunohistochemically pos itive for pRB, although with a variable proportion of non-immunoreacti ve cells. Carcinomas of the diffuse type showed absence of pRB express ion in a larger proportion of neoplastic cells than carcinomas of the intestinal type (P<0.05). Analysis of the RB1 structure using probe p6 8RS2.0 revealed allelic imbalance in 29% of informative cases. No homo zygous deletions and/or rearrangements were detected with p68RS2.0 and cDNA probes. Western analysis revealed no abnormal patterns of pRB. O ur data therefore suggest that major alterations affecting the RB1 gen e are rather infrequent in human gastric carcinomas.