极性蛋白Par3调控乳腺癌紫杉醇化疗耐药的分子机制研究

乳腺癌是全球发病率最高的恶性肿瘤。紫杉醇是乳腺癌治疗的一线药物，但部分患者仍表现出耐药。微管稳定性是影响紫杉醇敏感性的重要因素。极性蛋白Par3通过调控细胞骨架动力学影响乳腺癌侵袭转移，但其是否参与紫杉醇敏感性调控尚未可知。课题组前期发现，Par3低表达患者紫杉醇疗效不佳，Par3下调细胞紫杉醇耐药，微管稳定性降低；Par3可形成液液相分离液滴，加入抑聚剂后液滴及稳定微管束显著减少，提示Par3可能通过相分离提高微管稳定性。Par3下调通过减少相分离液滴形成，抑制微管聚集，促进紫杉醇耐药；联合aPKC抑制剂可减少Par3磷酸化，抑制液滴解聚，逆转耐药。本课题拟使用分子生物学技术、PDX模型及患者标本等手段，深入研究Par3调控液液相分离及微管聚集影响紫杉醇敏感性的机制，并探索其作为疗效预测及紫杉醇增敏靶点的可行性。以期丰富对Par3这一极性蛋白多元调控肿瘤的认知，拓展其临床应用价值。

Breast cancer is the most common malignancy worldwide. Paclitaxel is the cornerstone of the chemotherapy for breast cancer. However, some patients didn’t respond to paclitaxel and eventually experienced relapse or progression, indicating the resistance developed. No effective molecular targets have been found to reverse resistance and predict the response of paclitaxel in breast cancer patients up to now...Resistance to paclitaxel has been extensively explored, and altered microtubule stability is one of the important mechanisms. Polarity protein Par3, the scaffolding protein in Par complex, play a crucial role in the regulation of apical-basal polarity in epithelial cells. Loss of Par3 disrupted cytoskeleton dynamics and promoted breast cancer invasion and metastasis. However, whether Par3 is associated with paclitaxel resistance remains undetermined...In our preliminary experiments, we found that patients with low Par3 level showed a worse efficacy of paclitaxel. Downregulation of Par3 promoted the resistance of paclitaxel in breast cancer cells, inhibited cell apoptosis and reduced microtubule stability. We also observed that Par3 displayed puncta formation near the membrane of SK-BR-3 cells and its fluorescence intensity was correlated with that of the paclitaxel-induced bundles (PIBs). The puncta formation of Par3 and PIBs were disrupted by 1,6-hexanediol, an inhibitor of hydrophobic interaction induced phase separation assemblies. These data suggested that Par3 might promote microtubule polymerization via liquid-liquid phase separation (LLPS). Downregulation of Par3 reduced the assembly of the LLPS droplets and inhibited the polymerization of microtubule. We also supposed that aPKC inhibitor PKCZI195.17 could reduce the phosphorylation of Par3, inhibit the dissociation of Par3 LLPS droplets and reverse the paclitaxel resistance induced by loss of Par3. ..In this proposal, we plan to investigate the mechanism between Par3, LLPS and microtubule stability and its role in paclitaxel resistance. We will employ a multidiscipline approaches encompassing biochemistry and molecular biology, subcutaneous xenografts in nude mice, patient-derived xenograft model and patients tissue samples to pursue our aims above. The proposed studies in this application will not only allow us to advance the knowledge of molecular mechanisms in polarity protein Par3, but may also produce new leads to efficacy prediction and treatment of breast cancer.