發現UCP-2調控的「太平洋紫杉醇」新的抗藥性機轉及利用奈米平台改善治療效果

Abstract

Stat3 is more involved in tumor formation and Stat3 inhibition results in reduced cell viability and increased apoptosis in Non-Small Cell Lung Cancer (NSCLC). We have demonstrated that lung cancer cells with constitutive Stat3 activation are more resistant to paclitaxel-induced death. Besides, paclitaxel activates components of the mitogen-activated protein kinase (MAPK) signaling cascade to induce cellular apoptosis. Paclitaxel also stimulates NF-κB and activator protein 1 (AP-1) to promote cell proliferation (Cancer Immunol Immunother 49:78-84, 2000). Many anticancer agents, including paclitaxel, have been reported to generate reactive oxygen species (ROS). ROS have a dual role in cancer chemotherapy efficacy - make cancer cells either more sensitive or resistant to anticancer drugs. ROS may cause constitutive activation of transcription factors, such as NF-κB, AP-1, and Jak/Stat3, to promote cellular proliferation. Besides, increase in UCP-2 expression is to decrease ROS generation, which may contribute to the carcinogenesis of human colon cancer. However, the relationship between the UCP-2 expression and cellular response to chemotherapy-induced oxidative stress has not been well studied. In our study, we found that different human lung cancer cells have different UCP-2 expression. A549, H460 cells and CL1-0 cells expressed higher levels of UCP-2 protein. Paclitaxel did not induce higher levels of mitochondria-derived ROS in them; when UCP-2 was downregulated, paclitaxel might re-induce much ROS to induce cell death. On the contrary, in cancer cells with less UCP-2 expression as in AS2, H157 and CL1-5 cells, paclitaxel may induce ROS to activate Stat3/survivin/Mcl-1, thereby allowing the cancer cells to evade apoptosis. Besides, in lung cancer patients, low UCP-2 expression in cancer cells was also a predictor of a poor response to chemotherapy and had poor survival. In lower UCP-2 expression cancer cells, inhibition of ROS/Stat3 pathway may enhance treatment efficacy. Currently, “siRNAs” and small molecules to inhibit cellular signaling are used to inhibit a specific gene expression. siRNAs are easy to design and have high target selectivity and have a good effect on suppression of gene expression, but they have not performed in the clinic because they are easily degraded by nucleases and their poor pharmacokinetic profile. The FDA approved poly (D, L)-lactide-co-glycolide acid (PLGA) for clinical use in humans because it is biodegradable, biocompatible, and only mildly toxic. Nanoparticles (NPs) can deliver siRNA; besides, nanoparticles (NPs) carrying agents is proved as a vector to overcome chemoresistance related to MDR protein. Since Stat3 activation contributes cellular resistance to paclitaxel, nanoparticles simultaneously delivering Stat3 siRNA and paclitaxel are a useful way to down-regulate Stat3 expression to overcome chemoresistance to paclitaxel. In A549 and A549-derived paclitaxel resistant T12 cells with α tubulin mutation, PLGA NPs delivering paclitaxel are more cytotoxic to cancer cells than pclitaxel alone. To successfully synthesize the PLGA nanocomplex (PLGA-paclitaxel-Stat3 siRNA); first, paclitaxel was encapsulated by PLGA NPs (PLGA-TAX). The surfaces of PLGA-TAX were coated with polyethylenimine (PEI) (PLGA-TAX-PEI). Then, negative charge of siRNA was carried onto the surface of the PLGA NPs by electric attraction of positive charge of PEI (PLGA-TAX-PEI-S3SI). This PLGA-TAX-PEI-S3SI was uptaken into A549 and T12 cells and suppressed intracellular Stat3 expression. Compared to paclitaxel alone, the PLGA nanocomplex can make cellular tubulin more aggregation and were more cytotoxic to the cancer cells. Although lung cancer cells possess constitutively activated Stat3, paclitaxel either activates or suppresses Stat3 activation after chemotherapy through UCP-2-mediated ROS production. In high UCP-2 expression cancer cells where paclitaxel/cisplatin suppresses Stat3 activation, inhibition of UCP-2 with genipin (a derive from plant) can overcome chemoresistance through enhanced ROS-mediated cytotoxic effect; in lower UCP-2 expression cancer cells where paclitaxel/cisplatin activates Stat3, ROS inhibitor can interrupt ROS-induced cellular survival signaling by chemotherapy, which leads to cancer cells death. Therefore in the future, we may use different agents (either UCP-2 inhibitor or ROS scavenger) to enhance treatment efficacy according to cellular UCP-2 expression.