Chrysanthemum Lactone Reverses The Resistance Of Human Lung Adenocarcinoma Cell Line A549 To Doxorubicin By Inhibiting NF-κB And HSP70

The incidence of lung cancer has increased considerably over the past 50 years and lung carcinoma has become the leading cause of death by cancer. Chemotherapy resistance represents a major obstacle to the successful treatment of patients with lung carcinomas. P-gp mediated MDR was the first discovered and probably is the most widely observed mechanism in clinical chemotherapy resistance. The sesquiterpene lactone parthenolide (PN) is an active component of the herb feverfew, which has been used for a long time for the treatment of inflammation, migraine, menstrual irregularities, fever, and rheumatoid arthritis. Although its importance in treating the chemotherapy resistance has been shown, the pharmacological benefits of PN for lung cancer with multidrug resistance are underappreciated.In this study, using human lung epithelial carcinoma A549 and A549 derived DOX-resistant A549/DOX cell lines, we investigated the activities of PN in drug resistance and the underlying mechanisms. NF-k B is a ubiquitously expressed transcription factor that regulates several vital functions i.e. it controls apoptosis, cell proliferation and differentiation and it is a major player in the control of immune response and inflammation. Many anticancer agents induce NF-k B nuclear translocation and activation of its target genes, in turn, NF-k. B activation protects cells against apoptotic stimuli, such as those induced by chemotherapeutics, resulting in MDR. PN was also reported as a natural inhibitor of NF-k B, we therefore verified the inhibitory effect of PN on NF-k B pathway. Heat shock proteins (HSPs) are a super family of highly conserved molecular chaperone proteins, which is induced by various stimuli such as infection, high temperature, free radicals, and mechanical stress. The most studied and highly conserved HSPs is the HSP70 family, which functions as ATP-dependent molecular chaperones that assist in folding of newly synthesized polypeptides. HSP70 can also inhibit cellular apoptosis induced by various stresses, and has been reported to the drug resistance. Thus we evaluated whether HSP70 are correlated with P-gp mediated drug resistance.In the present study, we found that PN enhanced the apoptotic cytotoxicity of DOX in DOX-resistant A549/DOX cells. PN inhibited P-glycoprotein (P-gp) up-regulation and promoted the intracellular accumulation of DOX in A549/DOX cells. PN also exhibited dramatic inhibitory effect on NF-kB activation in A549/DOXcells, suggesting that inhibition of NF-kB was involved in antitumor actions of PN. Moreover, we established a correlation between HSP70 and P-gp. Overexpression of HSP70 was positively correlated with P-gp up-regulation independent of NF-kB activation in A549 cells and knockdown of HSP70 caused a reduced expression of P-gp in DOX resistant A549/DOX cells. Interestingly, PN could also effectively inhibit the HSP70 up-regulation. PN can reverse DOX resistance through suppressing P-gp expression by mechanisms involving attenuation of NF-kB activation and HSP70 up-regulation. Our results not only provide insight into potential use of PN in reversing Pgp mediated MDR to facilitate lung cancer chemotherapy, but also highlight a potential role of HSP70 in the development of drug resistance.