Combined effects of low-dose gambogic acid and NaI131 in drug-resistant non-small-cell lung cancer cells

Abstract

Background Radioactive seed is a method for treating drug-resistant, late-stage non-small cell lung cancer (NSCLC), but has undesirable side effects. Gambogic acid (GA), an ingredient of traditional Chinese medicine, exerts broad-spectrum antitumour activities via several pathways. This study aimed to elucidate the mechanism involved in the combined effect of low-dose GA and NaI131 to sensitize the antitumour activity of NaI131 in drug-resistant NSCLC cells. Methods Human NSCLC cell line A549 and drug-resistant cell lines A549/DDP and A549/Taxol were treated with NaI131, low-dose GA or a combination of both; control group of each cell line was treated with phosphate-buffered saline. Following treatment, cell proliferation, apoptosis, cell cycle, and levels of expression of apoptosis-related proteins namely CDK1, Cyclin B, mtp53, HSP90, and Bax, Bcl-2 respectively, and P-glycoprotein 1 (P-gp) known to confer resistance to chemotherapy, were detected using western blotting and immunofluorescence. mRNA levels of mtp53 and HSP90 were measured using qRT-PCR. Results Compared to the control group, A549, A549/DDP, and A549/Taxol cells treated with NaI131, GA or combination of drugs exhibited G2/M arrest, increased percentage of total apoptotic cells, significantly reduced protein levels of CDK1, Cyclin B, mtp53, HSP90, Bcl-2 and P-gp, increased protein levels of Bax and decreased mRNA levels of mtp53 and HSP90. The changes in the combination group were significantly different from the other groups. Conclusion In NSCLC cell lines, low-dose GA could enhance the effect of NaI131 on G2/M arrest, promote cell apoptosis, reduce drug-resistance and hence could be explored as a potential radionuclide sensitizer.