ABSTRACT
Aim To investigate the therapeutic efficacy of DTP-mediated photodynamic therapy (PDT) on SGC7901/VCR human vincristine ( VCR )-resistant gastric cancer cells, and to reveal the relationship between DTP-PDT and P-gp. Methods MTT assay was employed to evaluate the cytotoxicity of DTP-PDT and combination treatment with DTP-PDT and VCR. A SGC7901/VCR-bearing nude mouse model was established, and the tumor volume was measured to draw the growth curve. Cell apoptosis was detected by flow cytometry, and the yield of intracellular singlet oxygen (O2) was determined after DTP-PDT. The expression of MDR1 mRNA and P-gp was determined by qPCR and flow cytometry, respectively. Results DTP-PDT demonstrated significant cytotoxicity on SGC7901/VCR cells and the nude mice transplanted tumor. DTP-PDT could induce the apoptosis of SGC7901/VCR cells and the generation of intracellular O2. DTP-PDT could inhibit the expression of MDR1 mRNA and P-gp, which could be reduced by a-tocopherol. Combined treatment with DTP-PDT and VCR demonstrated synergistic efficacy on resistant cells, which could be reduced by or-tocopherol. Conclusions O2 generated by DTP-me-diated PDT could inhibit the growth of SGC7901/VCR cells and induce cell apoptosis. Meanwhile, it inhibits the over-expression of P-gp on cell membranes, leading to reduced efflux of VCR and synergistic efficacy with DTP-PDT and VCR eventually.
ABSTRACT
Objective To study the photodynamic therapeutical efficacy of a novel photosensitizer DTP on sensitive gastric cancer cells (SGC7901) and vincristine-resistant gastric cancer cells (SGC7901/VCR).Methods The P-gp expression on the SGC7901 and SGC7901/VCR cell membrane was indirectly confirmed by fluorescence microscopy.The survival rates of SGC7901 and SGC7901/VCR cells were evaluated by cell counting kit (CCK-8) after photodynamic therapy with DTP.The intracellular DTP uptake levels of two types of cell were determined using a fluorescence spectrophotometer,and the intracellular DTP distributions were observed by laser scanning confocal microscopy.Results The novel photosensitizer DTP has considerable photodynamic cytotoxic effect on SGC7901 and SGC7901/VCR cells.However,this effect on the SGC7901NCR cells was relatively weak (P＜0.05),and could not be enhanced by P-gp inhibitor verapamil or cyclosporine A(P＞0.05).The DTP uptake level in SGC7901 cells was higher than that in SGC7901/VCR cells (P＜0.05),and could not be enhanced by P-gp inhibitor verapamil and cyclosporin A (P＞0.05).It was found that DTP distributed in the lysosomes of SGC7901 cells and in the lysosomes and mitochondria of SGC7901/VCR cells.Conclusions The novel photosensitizer DTP is not the substrate of multidrug transporter P-gp,and its weaker photodynamic cytotoxic effect on SGC7901/VCR cells is independent of the P-gp overexpression on its cell membrane,which may be related to the distribution of intracellular DTP in the two types of cell.
ABSTRACT
Objective To study the photodynamic therapy (PDT) mediated by a novel porphyrin-typed photosensitizer on human hepatic carcinoma HepG2 cell and the mechanisms.Methods Experiments were derided into four groups:control group,PDT group,photosensitizer group and photosensitizer+PDT group.The photostability of novel photosensitizer upon repetitive illumination was evaluated by bleaching method,and cell survival rate was determined by MTT assay.Cellular uptake of novel photosensitizer was measured with luminescence spectrometer,and cellular localization ofphotosensitizer was observed by laser scanning confocal microscopy (LSCM).Furthermore,apoptotic cell was detected with Hoechst 333342 staining.Results Novel photosensitizer was stable after repetitive light irradiation,and PDT or photosensitizer alone showed no dark cytotoxicity toward HepG2 cell (P＞0.05),but intense killing was observed in photosensitizer+PDT group (P＜0.05).The IC50 is 1.21 μmol/L.Cellular uptake of novel photosensitizer was concentration-dependent and the highest uptake is at concentration of 12.5 μmol/L.Novel photosensitizer localizes in lysosomes of HepG2 cell,and the death mode of HepG2 cell was mainly apoptosis.Conclusions Novel photosensitizer exerts profound cytotoxic effects on HepG2 cell mainly through the initiation of secondary cell apoptosis by lysosome destruction.