Department of Dermatology, Guangdong Provincial People's Hospital and Guangdong Academy Medical Sciences, No.106, Zhongshan 2nd Road, Guangzhou, 510000, Guangdong, China.
Dermatology and STD Department, Affiliated Hospital of Nantong University, Jiangsu, China.
J Cancer Res Clin Oncol. 2021 Mar;147(3):767-777. doi: 10.1007/s00432-020-03484-4. Epub 2021 Jan 3.
Approximately 60% of patients with melanoma harbor BRAF mutation and targeting BRAF offers enormous advance in the treatment of those patients. Unfortunately, the efficacy of the BRAF inhibitors is usually restricted by the onset of drug resistance. Therefore, better understanding of the adaptive drug resistance mechanisms is essential for the development of alternative therapeutic strategies, and offers more promising measures to promote the short duration of response to BRAF inhibitors.
The levels of tumor suppressive long noncoding RNA on chromosome 8p12 (TSLNC8) were evaluated by qPCR. The MTT assay, colony formation assay, apoptosis assay, and in vivo xenograft tumor model were performed to assess the functions of TSLNC8 on drug resistance. Western blotting, RNA pull-down, and RNA immunoprecipitation (RIP) assays were applied to investigate the mechanisms of TSLNC8 in melanoma.
Herein, our findings demonstrate that TSLNC8 is significantly downregulated in BRAF inhibitor-resistant melanoma tissues and cells. Moreover, downregulation of TSLNC8 in BRAF inhibitor sensitive cells reduces the toxicity response to BRAF inhibitor PLX4720, and inhibits apoptosis of melanoma cells-treated with PLX4720. Further assay elucidates that TSLNC8 can bind with the catalytic subunit of protein phosphatase 1α (PP1α) to regulate its distribution, and Downregulation of TSLNC8 results in PP1α cytoplasmic accumulation, thus re-activating the MAPK signaling. Eventually, the overexpression of TSLNC8 in BRAF inhibitor PLX4720-resistant melanoma cells restores the sensitive to BRAF inhibitor.
Collectively, our research provides a compelling rationale for resistance to BRAF inhibitor in melanoma, and the patient might benefit from the combinatorial therapy of BRAF inhibitors and lncRNA TSLNC8.
大约 60%的黑色素瘤患者存在 BRAF 突变，针对 BRAF 的治疗为这些患者带来了巨大的进展。不幸的是，BRAF 抑制剂的疗效通常受到耐药性的限制。因此，更好地了解适应性耐药机制对于开发替代治疗策略至关重要，并为促进 BRAF 抑制剂短时间反应提供了更有前途的措施。
通过 qPCR 评估肿瘤抑制性长非编码 RNA 8p12 上的 TSLNC8 水平。通过 MTT assay、集落形成 assay、凋亡 assay 和体内异种移植肿瘤模型评估 TSLNC8 对耐药性的功能。应用 Western blotting、RNA 下拉和 RNA 免疫沉淀（RIP）assay 研究 TSLNC8 在黑色素瘤中的作用机制。
本研究发现，TSLNC8 在 BRAF 抑制剂耐药黑色素瘤组织和细胞中显著下调。此外，在 BRAF 抑制剂敏感细胞中下调 TSLNC8 会降低对 BRAF 抑制剂 PLX4720 的毒性反应，并抑制 PLX4720 处理的黑色素瘤细胞凋亡。进一步的研究表明，TSLNC8 可以与蛋白磷酸酶 1α（PP1α）的催化亚基结合，调节其分布，下调 TSLNC8 导致 PP1α 细胞质积累，从而重新激活 MAPK 信号通路。最终，在 BRAF 抑制剂 PLX4720 耐药黑色素瘤细胞中过表达 TSLNC8 可恢复对 BRAF 抑制剂的敏感性。
总之，我们的研究为黑色素瘤对 BRAF 抑制剂的耐药提供了有力的依据，患者可能受益于 BRAF 抑制剂和 lncRNA TSLNC8 的联合治疗。
