The deacylase SIRT5 supports melanoma viability by regulating chromatin dynamics.

Cutaneous melanoma remains the most lethal skin cancer, and ranks third among all malignancies in terms of years of life lost. Despite the advent of immune checkpoint and targeted therapies, only roughly half of patients with advanced melanoma achieve a durable remission. SIRT5 is a member of the sirtuin family of protein deacylases that regulate metabolism and other biological processes. Germline Sirt5 deficiency is associated with mild phenotypes in mice. Here we show that SIRT5 is required for proliferation and survival across all cutaneous melanoma genotypes tested, as well as uveal melanoma, a genetically distinct melanoma subtype that arises in the eye, and is incurable once metastatic. Likewise, SIRT5 is required for efficient tumor formation by melanoma xenografts, and in an autochthonous mouse Braf;Pten-driven melanoma model. Via metabolite and transcriptomic analyses, we find that SIRT5 is required to maintain histone acetylation and methylation levels in melanoma cells, thereby promoting proper gene expression. SIRT5-dependent genes notably include MITF, a key lineage-specific survival oncogene in melanoma, and the c-MYC proto-oncogene. SIRT5 may represent a novel, druggable genotype-independent addiction in melanoma. Overall design: RNA-seq was performed on A2058, A375, and SKMEL-2 cell lines infected with either control or SIRT5 shRNA (KD1 or KD2), for a total of 27 samples on the Illumina HiSeq4000 with 50nt paired-end sequencing. Alignment was conducted using STAR v.2.7.3a against Gencode (GRCh38 Release 34 primary assembly), counted using featureCounts, and differential expression was determined using DESeq2 v.1.28.1. A more detailed description is provided in the manuscript. Please note that one of the raw files associated with the 'A375 Non-targetting Control Rep 2' sample is truncated (70414_1_1.fq.gz).

皮肤黑色素瘤仍是致死性最高的皮肤恶性肿瘤，按寿命损失年数计算，其在所有恶性肿瘤中位列第三。尽管免疫检查点治疗与靶向治疗已问世，但仅约半数晚期黑色素瘤患者可获得持久缓解。SIRT5属于沉默信息调节因子（sirtuin）家族的蛋白去酰化酶，可调控代谢及其他生物学过程。生殖系SIRT5缺陷在小鼠中仅表现为轻度表型。
本研究发现，SIRT5对所有受试皮肤黑色素瘤基因型的细胞增殖与存活均为必需；对于葡萄膜黑色素瘤（uveal melanoma）——一种起源于眼部、遗传学特征独特的黑色素瘤亚型，发生转移后无法治愈——同样如此。此外，SIRT5对于黑色素瘤异种移植瘤的有效成瘤以及自发的Braf;Pten驱动小鼠黑色素瘤模型的构建均不可或缺。通过代谢组学与转录组学分析，我们发现SIRT5可维持黑色素瘤细胞的组蛋白乙酰化与甲基化水平，进而促进正常的基因表达。SIRT5依赖性基因显著包括黑色素瘤中关键的谱系特异性存活癌基因MITF，以及c-MYC原癌基因。SIRT5或可成为黑色素瘤中一种新型的、不依赖基因型的可靶向成瘾性靶点。
总体实验设计：对感染对照或SIRT5短发卡RNA（small hairpin RNA, shRNA，KD1或KD2）的A2058、A375及SKMEL-2细胞系进行RNA测序（RNA-seq），共27个样本，采用Illumina HiSeq4000平台进行50nt双端测序。序列比对使用STAR v.2.7.3a，参考基因组为Gencode（GRCh38 Release 34 原始组装序列）；基因计数采用featureCounts完成；差异表达分析使用DESeq2 v.1.28.1。更多详细描述见研究论文。
请注意，"A375 Non-targetting Control Rep 2"样本对应的其中一个原始文件（70414_1_1.fq.gz）存在截断。