[Effects of functional inhibition of p-glycoprotein on radiosensitivity of drug-resistant MCF-7/Adr tumor cells].

Objective: To observe the effects of functional inhibition of p-glycoprotein on radiosensitivity of drug-resistant MCF-7/Adr tumor cells.

Methods: Flow cytometry was used to examine the dynamic changes of apoptosis rate and mitochondrial membrane potential (deltapsim) in verapamil-treated and untreated MCF-7/Adr cells after the X-ray exposure.

Results: The apoptotic rate of verapamil-treated cells was 25.53%+/-2.85%, 30.43%+/-2.21%, 39.03%+/-2.60% at 6, 12, and 24 h after X-ray exposure, respectively, and was 16.13%+/-1.16%, 21.73%+/-1.31%, and 27.53%+/-2.55% for the untreated cells. The mean fluorescence intensity of verapamil-treated cells was 75.27+/-4.90, 96.47+/-5.59, 57.77+/-2.55, respectively, at the corresponding time points, in comparison with the intensity of 54.17+/-4.05, 62.30+/-5.93, and 39.53+/-2.65 for the untreated cells. The apoptosis rate and deltapsim of the treated cells were significantly higher than those in the untreated cells at each of the specified time point (P<0.01), and in the former cells, the apoptosis rate reached the maximum at 24 h (F=47.870, P=0.000) and the deltapsim at 12 h after X-ray exposure (F=74.485, P=0.000).

Conclusion: The radiosensitivity of MCF-7/Adr cells is increased after functional inhibition of p-glycoprotein, possibly in relation to the alteration of deltapsim.