蟾毒灵靶向SRC-3/MIF通路调节M2型巨噬细胞极化逆转结肠癌耐药的机制研究

Drug resistance and immunosuppression are the main reasons for the failure of chemotherapy. M2-polarized macrophage is one of the critical factors of chemotherapy resistance. Our previous study found that the supernatant of chemoresistant colon cancer cell culture could drive macrophage polarization compared with chemosensitive cell. Inhibiting the unusual increasing of macrophage migration inhibitory factor (MIF) in the supernatant could reverse this effect. Bufalin, which could reverse drug resistance of colon cancer, had the ability of reducing M2 macrophage polarization and downregulating the expression and secretion of MIF. Meanwhile, it has also been reported that SRC-3, the target protein of bufalin, can regulate the transcription of MIF. Thus we hypothesize that SRC3/MIF pathway might be a key target of Bufalin in reversing drug resistance of colon cancer by regulating the polarization of M2 macrophages. On this hypothesis, the present project will be performed the following studies, reveal the mechanism of MIF in enhancing drug resistance of colon cancer by driving M2 macrophage polarization; clarify the pharmacological effect and molecular mechanisms of bufalin targeted SRC-3/MIF pathway for regulating the polarization of M2 macrophages to reverse drug resistance in colon cancer. The research provides a theoretical base for the clinical application of bufalin combined with chemotherapy in the treatment of drug resistant colon cancer.

肿瘤化疗耐药及其诱导的免疫抑制是导致化疗失败的主要原因，M2型巨噬细胞是肿瘤细胞产生耐药的关键因素。课题组前期研究发现，结肠癌耐药细胞株上清液相对于其亲本株可促进M2型巨噬细胞的极化，抑制上清液中异常增多的巨噬细胞迁移抑制因子(MIF)可逆转这一现象。课题组长期研究的蟾毒灵，具有逆转结肠癌耐药的作用，同时可减弱M2型巨噬细胞的极化，并下调MIF的表达分泌。已有文献报道蟾毒灵的靶蛋白SRC-3能够调节MIF的转录作用。因此，我们假设SRC-3/MIF通路可能是蟾毒灵调节M2型巨噬细胞极化逆转结肠癌耐药的关键靶点。基于该假设，本课题拟用结肠癌耐药模型及临床标本为对象，明确MIF促进M2型巨噬细胞极化的作用，阐明蟾毒灵通过靶向SRC-3/MIF通路调节M2型巨噬细胞极化逆转结肠癌耐药的机制，分析MIF在临床标本中差异表达的临床意义。该研究为临床应用蟾毒灵联合化疗治疗结肠癌耐药提供理论依据。

M2型巨噬细胞极化是肿瘤化疗耐药的关键因素之一。越来越多的研究表明，化疗耐药可促进M2型巨噬细胞的极化。大量的证据表明蟾毒灵具有显著的抗肿瘤作用，以往的研究也发现蟾毒灵可减少M2巨噬细胞的极化在体内发挥抗肿瘤作用，但其机制仍然存在不清楚。在我们的研究中，我们发现蟾毒灵降低了耐药细胞诱导的M2型巨噬细胞极化在体内和体外;更为重要的是蟾毒灵对M2巨噬细胞极化无明显的直接影响。此外，我们证明蟾毒灵靶向SRC-3蛋白以减少MIF的释放从而调节M2型巨噬细胞的极化。更有趣的是，我们还发现蟾毒灵是临床用药华蟾素主要的活性单体，华蟾素通过调节M2巨噬细胞的极化，增强奥沙利铂在体内和临床上的抗肿瘤作用。总体而言，本研究为临床上应用以蟾毒灵为主要活性单体的药物与化疗结合治疗结直肠癌提供了理论依据。