低剂量DNA去甲基化药物对肝癌瘤床免疫细胞重激活的调控机制研究

The traditional Hepatocellular carcinoma (HCC) research mainly concerns on tumor cells, which tries to explain liver tumorigenesis from the alterations of genes and phenotypes of cancer cell itself. Large evidences have revealed the "immune suppression" condition in tumor bed, and the amount of lymphocytes, especially CD8+ T cells correlates with the prognosis of HCC patients. Thus, it is important to reverse the immune suppression and establish the antitumor immune system in tumor bed. Low doses of DNA demethylating drugs have long term epigenetic "memory" effects to directly inhibit tumor growth, which have been applied in hematological tumors in clinic. The department of biological therapy in our hospital first registered the clinical trials of "low dose decitabine based therapy in patients with refractory and/or chemotherapy resistant solid tumors". The clinical observations and pathological results indicated that the tumor cells disappeared, replaced by the CD8+ T cells in the tumor bed, after receiving this treatment, suggesting that the low doses of DNA demethylating drugs could induce the antitumor immune responses and kill the tumor cells. Therefore, we aim to study the molecular mechanism of the immune cells reactivation in HCC cancer bed treated by the demethylating drugs, to establish the research foundation for the regimen and assessment of the low dose decitabine based immune reactivation treatment in HCC patients.

传统肝癌研究注重肿瘤细胞自身，从癌细胞本身基因和表型的改变来解释肿瘤。大量证据显示肝癌瘤床处于"免疫抑制"状态，瘤内淋巴细胞的数量，尤其是CD8阳性细胞的数量与患者预后密切相关，因此解除免疫抑制，建立强大的"瘤床免疫"对肝癌治疗至关重要。低剂量DNA去甲基化药物具有长期的表观修饰"记忆"效应，可直接抑制肿瘤细胞生长，临床上用于治疗恶性血液系统肿瘤。我院生物治疗病区在国际上率先注册了应用低剂量去甲基化药物治疗复发难治性实体瘤的临床试验，临床观察及病理学研究发现接受该疗法的肝癌患者瘤灶中肿瘤细胞消失，取而代之的是大量CD8阳性淋巴细胞，提示低剂量去甲基化药物可诱发重建"瘤床免疫"，从而杀伤肝内肿瘤细胞。基于此，我们拟从分子、细胞、动物模型以及临床病理样本多个层次研究去甲基化药物诱发肝癌瘤床免疫重建的调控作用及其分子机制，为建立并优化低剂量去甲基化药物为基础的临床整体治疗策略与评估体系奠定基础。

肿瘤细胞逃避机体的免疫监视是肿瘤发生与发展的重要因素。通过增强机体的免疫系统活性，解除免疫抑制，从而达到杀伤肿瘤作用，是当今肿瘤治疗的研究热点方向。我院生物治疗科在国际上率先注册了应用低剂量去甲基化药物治疗复发难治性实体瘤的临床试验，临床研究发现，在复发难治性卵巢癌及消化道肿瘤中，低剂量地西他滨具有化疗增敏作用，且联合CIK免疫细胞治疗能够进一步显著提高疾病反应率及持久性。深入机制研究证明，低剂量DNA去甲基化药物地西他滨具有免疫调控作用。地西他滨治疗后，患者外周T细胞的TCR多样性增加；体内外实验证明低剂量地西他滨能够直接促进T淋巴细胞增殖、活化及其杀伤活性，而且地西他滨治疗后外周T细胞活性增强的卵巢癌患者，临床反应性好，无进展生存期长，外周IFN-γ+ T细胞比例可作为地西他滨疗效的体外预测指标。