Clinical significance of multidrug resistance and P-glycoprotein expression in patients with gastric carcinoma.

Twenty-four fresh tumors of gastric carcinoma were assessed by flow cytometric detection of P-glycoprotein (P-gp) using monoclonal antibody C219. Eight patients were P-gp positive. Differentiated gastric carcinomas contained significantly higher concentrations of P-gp positive. Incidence of P-gp positive was high in advanced stage. In 16 cases estimated chemosensitivity was test assessed by thymidine incorporation assay (TIA). Seven of nine multidrug-resistant cases according to TIA were P-gp positive and all of seven nonmultidrug resistant cases were P-gp negative. Expression of P-gp and multidrug resistance were closely correlated (P < 0.01). Also, in 89 patients with operable gastric carcinoma, the relation between in vitro chemosensitivity test (TIA) and their clinicopathologic features as well as their survival lengths were studied. Thirty-one of 89 specimens from gastric carcinoma patients were multidrug resistant according to TIA. Patients in the multidrug-resistant group had a significantly poorer cumulative survival rate than those who were not multidrug resistant (P < .05). The multivariate analysis showed that multidrug resistance is a useful indicator of prognosis (P < 0.1). We suggest that multidrug-resistant cases or P-gp-positive cases of gastric carcinoma are highly malignant, and these determinations are clinically useful.