CCL2介导胃癌细胞多药耐药及其机制研究

Intrinsic or acquired drug resistance is the major cause resulting into the treatment failure of human cancers including gastric cancer. Despite of intensive investigations into drug resistance, there is no clinical approaches effective to reverse drug resistance. In addition, little was known about the contribution of tumor cell-secreted cytokines to drug resistance. In the preliminary study of this project, we have established two gastric cancer cell lines resistant to cisplatin as well as other chemotherapeutic drugs such as ADM and As2O3. Moreover, the secretion of chemokine (C-C motif) ligand 2 (CCL2) was up-regulated and its downstream signaling pathways include PI3K/AKT, STAT-3 were activated in drug resistant cells. CCL2 depletion reversed drug resistance accompanied with the activation of apoptosis and autophagy while exogenous CCL2 conferred drug resistance to gastric cancer cells. Based on these preliminary results, we speculated that gastric cancer cell can secrete CCL2 in an autocrine or paracrine manner to activate PI3K/Akt, STAT-3 signaling, eventually conferring drug resistance. In this study, we will try to prove this hypothesis by exploring the regulation and function of CCL2 in gastric cancer cells resistant or sensitive to cisplatin or other chemotherapeutic drugs. By doing so, we believe that this study will clarify the contribution of CCL2 to drug resistance and be helpful to develop clinical managements to effectively reverse drug resistance and improve chemotherapy efficacy.

化疗耐药是导致胃癌治疗失败的主要原因。尽管肿瘤耐药相关研究较多，但目前临床上仍缺乏逆转耐药的有效手段，而肿瘤细胞分泌性因子在化疗耐药中的作用也知之甚少。在本项目前期研究中，我们诱导建立了顺铂耐药胃癌细胞模型，发现顺铂耐药胃癌细胞呈现多药耐药特征；进一步通过细胞因子筛选、敏感和耐药细胞共培养等方法发现细胞因子CCL2可以促进胃癌细胞耐药性形成，且涉及细胞自噬和凋亡等生物学过程；同时，耐药细胞中PI3K/AKT、STAT-3等CCL2下游信号通路异常激活。因此，我们认为胃癌细胞可能通过自分泌和旁分泌CCL2来影响PI3K/AKT、STAT-3等信号通路，进而抑制细胞自噬和凋亡水平，最终获得多药耐药能力。为验证该假说，本项目将通过分子、细胞、动物、临床等不同水平层次研究，分析CCL2在胃癌细胞多药耐药中的调控及其作用机制，以揭示肿瘤化疗耐药机制，从而为逆转肿瘤耐药和提高化疗疗效提供新的思路。

肿瘤耐药性是导致临床化疗失败的主要原因，而对肿瘤细胞分泌细胞因子在耐药性调节过程中的作用知之甚少，研究其作用及机制将为发展有效的肿瘤耐药血清标志物提供科学依据。本项目采用前期构建的顺铂耐药细胞株BGC823/DDP和SGC7901/DDP为主要细胞模型，利用细胞因子芯片技术筛选顺铂耐药细胞与敏感细胞分泌的差异细胞因子，并进一步用酶联免疫吸附法进行验证；分析筛选获得的细胞因子在调节胃癌细胞耐药的作用及其机制研究。结果：（1）肿瘤耐药细胞通过自分泌或旁分泌细胞因子产生并维持对顺铂的耐药性。（2）细胞因子CCL2在顺铂耐药细胞上清液中表达显著升高并具有维持肿瘤耐药性的功能。（3）CCL2在异质肿瘤耐药性传递过程中发挥重要信使作用。（4）顺铂耐药细胞内自噬水平受抑制，激活自噬可诱导细胞凋亡，逆转其耐药性。（5）CCL2通过激活PI3K/AKT信号通路抑制细胞自噬，从而发挥其促进肿瘤耐药的作用。（6）胃癌患者血清中CCL2含量显著升高，而手术切除肿瘤后血清中CCL2含量则显著下降；胃癌组织中CCL2高表达与细胞自噬水平呈负相关关系。本研究首次发现并阐明了CCL2对胃癌顺铂耐药的作用及其调控机制，从而为发展有效的肿瘤耐药血清标志物、逆转肿瘤耐药、提高治疗效果提供新的思路。