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

Abstract

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 SGC7901/VCR cells were determined using flow cytometric analysis. Results: (1) SGC7901 cells exhibited positive staining of PKC-α. SGC7901/VCR cells exhibited stronger staining of PKC-α than SGC7901 cells. The higher dosage vincristine selected, the much stronger staining of PKC-α was observed on SGC7901/VCR cells. (2) Both SGC7901 and SGC7901/VCR cells exhibited positive staining of PKC-βI and PKC-βII 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 7901 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 SGC 7901/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-α but not with anti-PKC-βI, PKC-βII and PKCγ antibodies. Conclusion: PKC-α, but not PKC-βI, PKC-βII or PKCγ, may play a role in multidrug resistance of gastric cancer cells SGC7901/VCR.