Fig. 4

Overcoming drug resistance by reducing the amount and changing the distribution of P-gp. a Confocal images and fluorescence intensity of P-gp in NCI/RES-ADR multidrug-resistant cancer cells without any treatment (control) and after treated with LSC nanoparticles with laser irradiation (LSC + L, 1 W cm⁻² for 1 min). The data show that the P-gp distributes not only on the cell plasma membrane but also in the cytoplasm after the LSC + L treatment, whereas it is dominantly located on the plasma membrane for the cells in the control group. In order to confirm the changed distribution of P-gp is owing to the inhibition of ATP, the multidrug-resistant cancer cells were treated with oligomycin (an inhibitor of ATP synthase) for 12 h at 200 ng ml⁻¹, the results confirm that inhibition of ATP can influence the distribution of P-gp. Scale bar: 10 μm. b–c Flow cytometry analysis of P-gp and quantitative data show that the expression of P-gp is slightly but significantly decreased in the multidrug-resistant cancer cells with the LSC + L treatment. These data indicate that multiple mechanisms contribute to the capability of the LSC + L treatment in overcoming the drug resistance of the multidrug-resistant cancer cells. The cells were permeabilized for the immunostaining and flow cytometry analyses. Error bars represent s.d. (n = 3). *p < 0.05 (Kruskal–Wallis H-test)