Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
Cancer Lett. 2021 Apr 1;502:25-33. doi: 10.1016/j.canlet.2020.12.044. Epub 2021 Jan 10.
Therapy resistance to a selective B-Raf inhibitor (BRAFi) poses a challenge in treating patients with BRAF-mutant melanomas. Here, we report that RNA interference of mortalin (HSPA9/GRP75), a mitochondrial molecular chaperone often upregulated and mislocalized in melanoma, can effectively induce death of vemurafenib-resistant progenies of human B-Raf melanoma cell lines, A375 and Colo-829. Mortalin depletion induced death of vemurafenib-resistant cells at similar efficacy as observed in vemurafenib-naïve parental cells. This lethality was correlated with perturbed mitochondrial permeability and was attenuated by knockdown of adenine nucleotide translocase (ANT) and cyclophilin D (CypD), the key regulators of mitochondrial permeability. Chemical inhibition of MEK1/2 and ERK1/2 also suppressed mortalin depletion-induced death and mitochondrial permeability in these cells. These data suggest that mortalin and MEK/ERK regulate an ANT/CypD-associated mitochondrial death mechanism(s) in B-Raf melanoma cells and that this regulation is conserved even after these cells develop BRAFi resistance. We also show that doxycycline-induced mortalin depletion can effectively suppress the xenografts of vemurafenib-resistant A375 progeny in athymic nude mice. These findings suggest that mortalin has potential as a candidate therapeutic target for BRAFi-resistant BRAF-mutant tumors.
针对选择性 B-Raf 抑制剂（BRAFi）的治疗抵抗是治疗 BRAF 突变型黑色素瘤患者的一个挑战。在这里，我们报告称，线粒体分子伴侣 mortalin（HSPA9/GRP75）的 RNA 干扰，其在黑色素瘤中经常上调和定位错误，可有效诱导人 B-Raf 黑色素瘤细胞系 A375 和 Colo-829 的 vemurafenib 耐药后代死亡。Mortalin 耗竭诱导 vemurafenib 耐药细胞死亡的效果与在未接触 vemurafenib 的亲本细胞中观察到的效果相似。这种致死性与线粒体通透性的改变有关，并且可以通过敲低腺嘌呤核苷酸转运体（ANT）和环孢菌素 D（CypD）（线粒体通透性的关键调节剂）来减弱。MEK1/2 和 ERK1/2 的化学抑制也抑制了这些细胞中 mortalin 耗竭诱导的死亡和线粒体通透性。这些数据表明，mortalin 和 MEK/ERK 调节 B-Raf 黑色素瘤细胞中 ANT/CypD 相关的线粒体死亡机制，并且即使在这些细胞产生 BRAFi 耐药后，这种调节仍然是保守的。我们还表明，强力霉素诱导的 mortalin 耗竭可以有效地抑制无胸腺裸鼠中 vemurafenib 耐药 A375 后代的异种移植物。这些发现表明 mortalin 可能成为 BRAFi 耐药 BRAF 突变型肿瘤的候选治疗靶点。
