CD24经sonic Hedgehog通路介导视网膜母细胞瘤低氧微环境下的自噬及耐药机制

Retinoblastoma (RB) is the most common primary eye cancer in children. RB treatment often fails due to chemotherapy resistance. Studies have shown that hypoxia is a basic feature of RB, hypoxia-activated autophagy is an important route for tumor cell to escape anti-tumor drugs . However, the regulatory mechanism remains unclear. Our previous studies established a vincristine-resistant strains SO-RB50 / VCR. We found in hypoxia, CD24 expression is upregulated and increased levels of autophagy, and it is closely related to abnormal activation of the Hedgehog pathway. And in clinical drug-resistant tissues, hypoxia inducible factor HIF and CD24 were over-expressed, which indicates CD24 may regulate autophagy by Hedgehog signaling under hypoxic microenvironment and cause RB resistance to chemotherapy. From the mutual regulations of hypoxia microenvironment and cell autophagy, the project will study the effects of hypoxia microenvironment to cell autophagy by regulating CD24 expression.. We will use microarray, co-immunoprecipitation techniques to screen and determine if Hedgehog signaling pathway is involved in the regulation. Finally, we will elucidate the mechanism how CD24 promotes RB drug resistance under hypoxic microenvironment by using function inactivation and function activated regulation of cell autophagy. The finding will provide new ideas for finding effective clinical drug targets and therapeutic strategies to reverse RB drug resistance.

视网膜母细胞瘤（RB）是婴幼儿最常见眼内原发性恶性肿瘤，常因化疗耐药而导致治疗失败。研究表明缺氧是RB的基本特征，低氧激活的自噬是肿瘤细胞对药物治疗抵抗的重要逃避途径，但其调控机制仍不明确。我们前期研究建立了长春新碱耐药株SO-RB50/VCR，发现在低氧环境下CD24表达上调且自噬水平增加，与Hedgehog通路异常活化密切相关，同时临床耐药组织中缺氧诱导因子HIF和CD24过量表达，提示CD24可能通过Hedgehog信号调控低氧微环境下的自噬而导致RB化疗耐药。本项目拟从低氧微环境与细胞自噬相互调控为切入点，通过调节CD24的表达，观察低氧微环境对细胞自噬影响；再利用表达谱芯片、免疫共沉淀等技术筛选并确定CD24参与脂筏调控Hedgehog信号通路；最后采用功能失活、功能激活调控细胞自噬，观察低氧微环境下CD24促进RB耐药机制，为寻找有效临床靶标及逆转RB耐药的治疗策略提供新思路。

视网膜母细胞瘤（Retinoblastoma，RB）是最常见的儿童眼内恶性肿瘤。在RB临床诊疗过程中，耐药性严重限制了长春新碱（vincristine，VCR）治疗的临床疗效。在本研究中，我们探索了CD24分子对RB患者化学敏感性的影响。我们发现CD24作为一种糖基磷脂酰肌醇（Glycosyl-phosphatidylinositol，GPI）锚蛋白在RB组织和RB细胞系中过表达，并且与RB细胞对VCR治疗的敏感性相关。此外，我们发现CD24通过调节自噬在降低RB对VCR治疗敏感性中起关键作用。机制研究表明CD24募集PTEN到脂筏结构域，通过PTEN/AKT/mTORC1通路激活自噬。GPI锚对CD24的募集功能至关重要。因此，CD24通过调节自噬降低RB细胞对VCR治疗的敏感性。检测或者靶向CD24及其相关通路将会为对临床治疗提供有价值的建议，并可能改善RB患者的预后。