Autophagy maintains cells survival in many stressful conditions including starvation, growth factor deprivation and misfolded protein accumulation. Additionally, autophagic survival mechanisms are used by transformed tumor cells to inhibit cell death, limit drug effectiveness and possibly generate drug resistance. However, the mechanism of how cells utilize autophagy during drug resistance is not fully understood. Here, we demonstrate that miR-216b plays an important role in alleviating drug resistance by regulating autophagy in melanoma. We show that miR-216b attenuates autophagy by directly targeting three key autophagy genes Beclin-1, UVRAG and ATG5. Overexpression of these genes from miRNA immune cDNA constructs rescue autophagic activity in the presence of miR-216b. Antagomir-mediated inactivation of endogenous miR-216b led to an increase of Beclin-1, UVRAG, ATG5, and subsequent autophagic activity. More importantly, we have discovered that BRAF(V600E) inhibitor vemurafenib suppresses miR-216b activity, which in turn activates autophagy to generate drug resistance in both BRAFi-sensitive and -resistant cells. Strikingly, ectopic expression of miR-216b increases the efficacy of vemurafenib both in vitro and in vivo. Taken together, these data indicate that miR-216b regulates autophagy by suppressing three key autophagy genes, and enhances the antitumor activity of vemurafenib in BRAF(V600E) melanoma cells.

自噬可在许多压力条件下维持细胞存活，包括饥饿，生长因子剥夺和折叠错误的蛋白质积累。另外，转化的肿瘤细胞使用自噬生存机制来抑制细胞死亡，限制药物有效性并可能产生耐药性。但是，尚不完全了解细胞在耐药过程中如何利用自噬的机制。在这里，我们证明了miR-216b在黑色素瘤中通过调节自噬在减轻耐药性中起着重要作用。我们显示miR-216b通过直接靶向三个关键的自噬基因Beclin-1，UVRAG和ATG5来减弱自噬。在miR-216b的存在下，这些基因从miRNA免疫cDNA构建体的过表达可以挽救自噬活性。Antagomir介导的内源性miR-216b失活导致Beclin-1，UVRAG，ATG5和随后的自噬活性增加。更重要的是，我们发现BRAF（V600E）抑制剂vemurafenib抑制miR-216b活性，进而激活自噬以在BRAFi敏感和耐药细胞中产生耐药性。令人惊讶的是，miR-216b的异位表达增加了维罗非尼的疗效体外和体内。综上所述，这些数据表明，miR-216b通过抑制三个关键的自噬基因来调节自噬，并增强了维拉非尼在BRAF（V600E）黑色素瘤细胞中的抗肿瘤活性。