Hedgehog 信号通路异常激活在乳腺癌内分泌治疗耐药及复发中的作用与靶向治疗

Endocrine therapy is one of the most effective targeted treatment strategies for ER-positive breast cancer. However, relapse and distant metastasis are major obstacles in successful treatment of these breast cancer, and the molecular mechanisms underlying these processes are still fully unknown. We have demonstrated previously that aberrant activation of Hedgehog(Hh) signaling pathway in tamoxifen resistance and metastatic breast cancer was mediated by hyperactive PI3K/AKT signaling. Here we propose that stabilization of Smo and Gli proteins in breast cancer cells is mediated by hyperactive PI3K/AKT signaling that facilitate survival and outgrowth of breast cancer cells as well as acquisition of aggressive phenotype. Therefore therapeutic targeting these two pathways with combination of Hh pathway and PI3K/AKT inhibitors would be a rationale and novel strategy to treat the metastasis of breast cancer. Using human breast cancer cell lines, orthotopic animal model with innovatively molecular techniques and gene expression profiling, we will validate this hypothesis with the following specific aims: (1) Comprehensively elucidate the role of PI3K/AKT in activating Hh pathway in breast cancer. (2) Identify molecular networks involved in the relapse of TAM resistant breast cancer after targeting Hh pathway with GDC-0449, and Determine if combination of Hh and PI3K/AKT inhibitor could be an effective option in inhibiting relapse of of breast cancer. (3) Dissect the downstream signaling networks regulated by hyperactive Hh/Gli1 pathway in aggresive breast cancer and its significance in regulating the recurrence of ER-positive breast cancer These studies may provide crucial insights into molecular networks behind the recurrence and metastasis of breast cancer, and open novel avenues for translational and personalized medicine in breast cancer.

内分泌治疗是目前雌激素受体阳性乳腺癌最有效的治疗策略，但复发与转移仍是这类乳腺癌临床治疗的最大障碍。我们已经证实：在Tamoxifen（TAM）耐药和转移的腺癌细胞中，PI3K/AKT异常活化导致Hedgehog （Hh）信号通路激活。我们假设PI3K/AKT信号通路激活提高了Hh信号通路中关键分子Smo和Gli蛋白的稳定性并活化Hh信号通路，从而有利于乳腺癌细胞生长并获得耐药与转移能力。利用乳腺癌细胞系、动物模型、分子与细胞生物学技术及基因表达谱分析，我们将进一步探讨（1）阐明PI3K/AKT激活Hh信号通路的分子机制。（2）探讨耐药乳腺癌复发机制及联合靶向应用Hh和PI3K/AKT特异性抑制剂是否能有效抑制乳腺癌细胞的生长与转移。（3）明确TAM耐药及复发转移乳腺癌细胞中Hh/Gli调控的分子信号网络。本研究结果将为阐明乳腺癌复发转移机制提供新的依据，为乳腺癌临床个性化治疗开辟新道路。

乳腺癌是我国女性高发恶性肿瘤。大约70%的乳腺癌患者为雌激素受体阳性，抗雌激素等内分泌靶向治疗是这类中肿瘤的有效治疗手段。然而，约30%-40%接受内分泌治疗的患者出现原发或继发性耐药。我们先前研究表明hedgehog-GLI1信号通路异常激活是乳腺癌他莫昔芬耐药的重要因素，且受到异常激活的PI3K/AKT信号通路调控。本研究我们主要探讨：（1）阐明PI3K/AKT激活Hh信号通路的分子机制。（2）探讨耐药乳腺癌复发机制及联合靶向应用Hh和PI3K/AKT特异性抑制剂是否能有效抑制乳腺癌细胞的生长与转移。（3）明确TAM耐药及复发转移乳腺癌细胞中Hh/Gli调控的分子信号网络。我们进一步鉴定了GLI1蛋白序列中GSK3β磷酸化位点，证实过表达GLI1使TAM敏感乳腺癌细胞产生耐药。明确了PI3K/AKT抑制剂GDC-0941单独或联合SMO特异抑制剂GDC-0449能明显抑制TAM耐药乳腺癌细胞生长与运动。进一步发现了单独抑制Hh信号通路或联合TAM能诱导细胞自噬和DNA损伤，并出现非依赖Caspase细胞死亡，而且HSP90抑制剂Ganetespib能显著降低乳腺癌细胞核中DNA修复相关蛋白的稳定性，抑制双链DNA损伤修复过程，有利于逆转乳腺癌细胞耐药表型。更重要的是我们发现GLI1及其调控的下游相关因子EGFR和SNAI1能预测Luminal A 乳腺癌患者的预后。这些结果提示Hh信号通路是调控ER+乳腺癌内分泌治疗耐药的重要通路，而且GLI1相关基因表达标签将成为ER+乳腺癌患者临床诊疗中进一步分层的有用工具，具有重要临床转化意义。