Expression and function of classical protein kinase C isoenzymes in gastric cancer cell line and its drug-resistant sublines

AIM: To investigate the expression and function of classical protein kinase C (PKC) isoenzymes in inducing MDR phenotype in gastric cancer cells. METHODS: Two cell lines were used in the study: gastric cancer cell SGC7901 and its drug-resistant cell SGC7901/VCR stepwise-selected by vincristine 0.3, 0.7 and 1.0 mg.L-1, respectively. The expression of classical PKC ( cPKC) isoenzymes in SGC7901 cells and SGC7901/VCR cells were detected using immunofluorescent cytochemistry, laser confocal scanning microscope and Western blot. The effects of anti-PKC isoenzymes antibody on adriamycin accumulation in SGG7901/VCR cells were determined using flow cytometric analysis. RESULTS: (i) SGC7901 cells exhibited positive staining of PKC-alpha. SGC7901/VCR cells exhibited stronger staining of PKC-alpha, than SGC7901 cells. The higher dosage vincristine selected, the much stronger staining of PKC-alpha, was observed on SGC7901/VCR cells. (2) Both SGC7901 and SGC7901/VCR cells exhibited positive staining of PKC-betaI and PKC-betaII with no significant difference. (3) Compared with SGC7901, SGC7901/VCR cells had decreased adriamycin accumulation and retention. Accumulation of adriamycin in SGC7901 was 5.21 +/- 2.56 mg.L-1, in SGC7901/VCR 0.3 was 0.85 +/- 0.29 mg.L-1, in SGC7901/VCR 0.7 was 0.81 +/- 0.32 mg.L-1, and in SGC7901/VCR 1.0 was 0.80 +/- 0.33 mg.L-1; Retention of adriamycin in SGC 790 L was 2.51 +/- 1.23 mg.L-1, in SGC7901/VCR 0.3 was 0.47 +/- 0.14 mg.L-1', in SGC7901/VCR 0.7 was 0. 44 +/- 0.15 mg.L-1, and in SGC7901/VCR 1.0 was 0. 41 0. 11 mg.L-1. (4) Fluorescence intensity presented adriamycin accumulation in SGC7901/VCR cells was increased from 1. 14 0. 36 to 2.71 +/- 0.94 when cells were co-incubated with anti-PKC-alpha but not with anti-PKC-betaI, PKC-betaII and PKCgamma antibodies. CONCLUSION: PKC-alpha, but not PKC-betaI, PKC-betaII or PKCgamma, may play a role in multidrug resistance of gastric cancer cells SGC7901/VCR.