低剂量去甲基化药物逆转消化道肿瘤化疗耐药的疗效与机制研究

Chemotherapy is one of the mainstays of cancer therapy, but chemoresistance has become the largest obstacle to the success of cancer chemotherapies. The merging of laboratory and clinical data confirmed that the abnormal epigenomics of both cancer cells and cancer stem cells is the critical regulator of the malignant phenotypes of cancers including drug resistance. Low-dose demethylating drugs, which are mainly applied in hematological tumors in clinic, induced ‘‘memory’’ alterations in epigenomics of cancer. We have registered the clinical trial in the ClinicalTrials.gov database to determine the efficacy of the low-dose demethylating drug combined chemotherapy regimens in patients with chemotherapy resistant solid tumors. The clinical observations indicated that this combined antitumor therapy would promoted the disease control rate and prolonged the progression-free survival of patients with advanced chemoresistant gastrointestinal cancers, suggesting that low-dose demethylating drugs could prevent or reverse non-responsiveness to anti-cancer drugs. Therefore, we aim to confirm the efficacy of low-dose demethylating drugs as the sensitizer of chemotherapy, to illustrate the molecular mechanism of reversion of chemoresistance by demethylating drugs, and to establish and optimize the regimen and assessment system of low-dose demethylating drug combined with chemotherapy in patients with chemoresistant gastrointestinal cancers.

化学药物治疗(化疗)是目前恶性消化道肿瘤的主要治疗手段,化疗耐药是制约肿瘤临床疗效的关键因素。大量研究显示肿瘤细胞和肿瘤干细胞的表观基因组异常改变直接参与了肿瘤化疗耐药的发生。低剂量去甲基化药物具有长期的表观修饰“记忆”效应，目前用于恶性血液系统肿瘤的治疗。本团队生物治疗病区率先注册了国际临床试验，探索低剂量去甲基化药物联合化疗治疗复发难治性实体瘤的可行性。前期基于27例化疗耐药的进展期消化道肿瘤的临床观察发现，该联合疗法可显著提高患者的疾病控制率，延长无进展生存期，提示低剂量去甲基化药物可改善/逆转消化道肿瘤化疗耐药。基于以上发现，本课题拟从体内、体外和临床角度验证低剂量去甲基化药物作为化疗增敏剂的效果，从分子、细胞、组织及整体水平阐明去甲基化药物逆转消化道肿瘤化疗耐药的关键机制，并建立优化的低剂量去甲基化药物联合化疗治疗耐药性消化道恶性肿瘤的整体治疗方案与疗效评估体系。

化疗耐药是目前制约肿瘤临床治疗疗效的关键因素。研究提示表观遗传学改变可能直接参与肿瘤化疗耐药的发生。本课题拟从体内、体外和临床角度探讨低剂量去甲基化药物作为化疗增敏剂的效果和分子机制。针对复发、难治性消化道肿瘤和卵巢癌，应用低剂量去甲基化药物联合化疗、免疫治疗方案，开展了I/II期临床试验探索，获得了较好临床疗效，疾病控制率分别达82.2%和73.9%，分别有2例消化道肿瘤和2例卵巢癌患者达到完全缓解。该方案具有较好安全性，可改善患者化疗耐药，显著提高临床反应率，延长无进展生存期，目前该方案已在多家三甲医院推广，启动了多中心临床试验。依托临床试验结果，本课题从分子、细胞、组织及整体水平对去甲基化药物逆转肿瘤化疗耐药的关键分子和机制进行了探索。初步筛选了表观-化疗联合方案在消化道肿瘤中的疗效预判血浆microRNA标志物（miR-543，miR-1908-5p，miR-3120-5p，miR-651-5p和miR-450a-5p）。结合转录组测序和microRNA测序结果，证实miR-181a/181b、miR-135a、miR-302c受到甲基化调控，在肿瘤发生发展、化疗耐药过程中发挥重要作用。这些miRNA分子通过其靶基因PI3K信号分子PIK3R3、PLAG1发挥抑癌基因功能。去甲基化调控可恢复这些分子的表达，进而改善肿瘤细胞对化疗药物的敏感性。我们的结果为进一步探讨去甲基化药物改善/逆转肿瘤化疗耐药机制开辟了新的视角，并且将为探索新的疗效标志物和临床治疗靶点提供研究基础。本课题相关结果发表SCI论文5篇，总影响因子31，单篇最高10.199。申报国家发明专利2项。