Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213.
UPMC Hillman Cancer Center, University of Pittsburgh Medical Center, Pittsburgh, PA 15232.
Proc Natl Acad Sci U S A. 2022 Mar 22;119(12):e2100670119. doi: 10.1073/pnas.2100670119. Epub 2022 Mar 14.
Squamous cell carcinoma of the head and neck (SCCHN) is a devastating disease that continues to have low cure rates despite the recent advances in therapies. Cisplatin is the most used chemotherapy agent, and treatment failure is largely driven by resistance to this drug. Amplification of chromosomal band 11q13 occurs in ∼30% of SCCHN tumors. This region harbors the ANO1 gene that encodes the TMEM16A ion channel, which is responsible for calcium-activated chloride transport in epithelial tissues. TMEM16A overexpression is associated with cisplatin resistance, and high TMEM16A levels correlate with decreased survival. However, the mechanistic underpinning of this effect remains unknown. Lysosomal biogenesis and exocytosis have been implicated in cancer because of their roles in the clearance of damaged organelles and exocytosis of chemotherapeutic drugs and toxins. Here, we show that TMEM16A overexpression promotes lysosomal biogenesis and exocytosis, which is consistent with the expulsion of intracellular cisplatin. Using a combination of genetic and pharmacologic approaches, we find that TMEM16A promotes lysosomal flux in a manner that requires reactive oxygen species, TRPML1, and the activation of the β-catenin–melanocyte-inducing transcription factor pathway. The lysosomal inhibitor hydroxychloroquine (HCQ) synergizes with cisplatin in killing SCCHN cells in vitro. Using a murine model of SCCHN, we show that HCQ and cisplatin retard the growth of cisplatin-resistant patient-derived xenografts in vivo. We propose that TMEM16A enables cell survival by the up-regulation of lysosomal sequestration and exocytosis of the cytotoxic drugs. These results uncover a model of treatment for resistance in cancer, its reversal, and a role for TMEM16A.
头颈部鳞状细胞癌 (SCCHN) 是一种破坏性疾病，尽管近年来治疗方法有所进步，但治愈率仍然很低。顺铂是最常用的化疗药物，治疗失败在很大程度上是由于对这种药物的耐药性。染色体 11q13 带的扩增发生在约 30%的 SCCHN 肿瘤中。该区域包含编码 TMEM16A 离子通道的 ANO1 基因，该通道负责上皮组织中钙激活的氯离子转运。TMEM16A 的过表达与顺铂耐药有关，高 TMEM16A 水平与存活率降低相关。然而，这种效应的机制基础尚不清楚。溶酶体生物发生和胞吐作用已被牵涉到癌症中，因为它们在清除受损细胞器和胞吐化疗药物和毒素方面发挥作用。在这里，我们表明 TMEM16A 的过表达促进了溶酶体的生物发生和胞吐作用，这与细胞内顺铂的排出一致。我们使用遗传和药理学方法的组合发现，TMEM16A 以需要活性氧、TRPML1 和 β-连环蛋白-黑色素生成转录因子途径的激活的方式促进溶酶体通量。溶酶体抑制剂羟氯喹 (HCQ) 与顺铂在体外协同杀死 SCCHN 细胞。使用 SCCHN 的小鼠模型，我们表明 HCQ 和顺铂在体内延缓了顺铂耐药患者来源的异种移植物的生长。我们提出，TMEM16A 通过上调溶酶体隔离和细胞毒性药物的胞吐作用来使细胞存活。这些结果揭示了一种针对癌症耐药性的治疗模型、其逆转以及 TMEM16A 的作用。
