Correlation of multidrug resistance with up-regulation of protein kinase C expression in KBV200 cells.

Objective: To investigate protein kinase C (PKC) expression and its association with multidrug resistance (MDR) in KBV200 cells.

Methods: KBV200 cells were preincubated with PKC activator phorbol-12-myristate-13-acetate (PMA, 200 nmol/L) and PKC activity was assayed by measurement of peptide substrate (32)P incorporation from [gamma-(32)P]ATP, with the cells without PMA preincubation serving as the control. Western blotting was performed for assessing the expression of PKC isoform, and the cell inhibition rate was evaluated by MTT assay.

Results: PMA preincubation of the cells significantly enhanced the activity of the total PKC and the membrane fraction, but lowered the PKC activity of the cytosol fraction, as compared with the cells without PMA treatment (P<0.01). PKC-alpha expression was upregulated in the membrane fraction and down-regulated in the cytosol fraction in KBV200 cells after PMA preincubation. PKCbeta expression was slightly elevated in the cytosol fraction but exhibited no obvious changes in the membrane fraction after PMA pretreatment of the cells. The values of IC(50) of vincristine and adriamycin in PMA-treated cells were increased to 2275.5 nmol/L and 233.25 nmol/L, respectively (P<0.01).

Conclusion: PMA can increase the multidrug resistance of KBV200 cells, which suggests the possible involvement of PKC in the mechanism of multidrug resistance of tumor cells.