Liu Xiao, Li Chengyuan, Fu Yunfeng, Liu Jing
Department of Hematology, The Third Xiangya Hospital of Central South University, Changsha 410013, People's Republic of China.
Onco Targets Ther. 2020 Jan 14;13:401-411. doi: 10.2147/OTT.S237343. eCollection 2020.
Treatment of bortezomib (BTZ) improves the clinical outcomes of patients with multiple myeloma (MM). However, primary resistance and acquired resistance to BTZ frequently develop in patients with MM. PH domain leucine-rich repeat protein phosphatase (PHLPP) plays an important role in chemoresistance in a number of cancers. However, the role of PHLPP on MM remains unclear. In this study, we investigated the role of PHLPP in BTZ-resistant MM cells.
BrdU assays, immunoprecipitation, flow cytometry analyses, and immunofluorescence assays were performed.
PHLPP and lysosome-associated membrane protein 2 (LAMP2) levels were downregulated in BTZ-resistant MM cells compared with BTZ-sensitive MM cells, accompanied by inactivation of autophagy pathway evaluated by a reduction in Beclin1, Atg5 and LC3B and increase in p62. Gain- and loss-of-function experiments revealed that PHLPP partially re-sensitized MM cells to BTZ. In addition, PHLPP overexpression increased whereas PHLPP knockdown reduced LAMP2 expression, subsequently regulating the autophagy pathway in MM cells. Further findings demonstrated that LAMP2 knockdown reversed PHLPP-mediated cell apoptosis and autophagy activation in MM cells.
This study demonstrated that PHLPP is a potential strategy for overcoming BTZ resistance in patients with MM.
硼替佐米（BTZ）治疗可改善多发性骨髓瘤（MM）患者的临床结局。然而，MM患者中常出现对BTZ的原发性耐药和获得性耐药。富含PH结构域的亮氨酸重复蛋白磷酸酶（PHLPP）在多种癌症的化疗耐药中起重要作用。然而，PHLPP在MM中的作用仍不清楚。在本研究中，我们调查了PHLPP在BTZ耐药MM细胞中的作用。
进行了BrdU检测、免疫沉淀、流式细胞术分析和免疫荧光检测。
与BTZ敏感的MM细胞相比，BTZ耐药的MM细胞中PHLPP和溶酶体相关膜蛋白2（LAMP2）水平下调，同时自噬途径失活，表现为Beclin1、Atg5和LC3B减少以及p62增加。功能获得和功能丧失实验表明，PHLPP使MM细胞对BTZ部分重新敏感。此外，PHLPP过表达增加而PHLPP敲低降低LAMP2表达，随后调节MM细胞中的自噬途径。进一步的研究结果表明，LAMP2敲低逆转了PHLPP介导的MM细胞凋亡和自噬激活。
本研究表明，PHLPP是克服MM患者BTZ耐药的一种潜在策略。
