Kanazawa Kosuke, Kishimoto Kazuhiro, Nomura Miyuki, Kurosawa Koreyuki, Kato Hiroyuki, Inoue Yui, Miura Koh, Fukui Katsuya, Yamashita Yoji, Sato Ikuro, Tsuji Hiroyuki, Watanabe Toshio, Tanaka Takuji, Yasuda Jun, Tanuma Nobuhiro, Shima Hiroshi
Division of Cancer Chemotherapy, Miyagi Cancer Center Research Institute, Miyagi, Japan.
Division of Surgery, Miyagi Cancer Center, Miyagi, Japan.
Cancer Sci. 2021 Jun;112(6):2233-2244. doi: 10.1111/cas.14895. Epub 2021 Apr 10.
According to TCGA database, mutations in PPP6C (encoding phosphatase PP6) are found in c. 10% of tumors from melanoma patients, in which they coexist with BRAF and NRAS mutations. To assess PP6 function in melanoma carcinogenesis, we generated mice in which we could specifically induce BRAF(V600E) expression and delete Ppp6c in melanocytes. In these mice, melanoma susceptibility following UVB irradiation exhibited the following pattern: Ppp6c semi-deficient (heterozygous) > Ppp6c wild-type > Ppp6c-deficient (homozygous) tumor types. Next-generation sequencing of Ppp6c heterozygous and wild-type melanoma tumors revealed that all harbored Trp53 mutations. However, Ppp6c heterozygous tumors showed a higher Signature 1 (mitotic/mitotic clock) mutation index compared with Ppp6c wild-type tumors, suggesting increased cell division. Analysis of cell lines derived from either Ppp6c heterozygous or wild-type melanoma tissues showed that both formed tumors in nude mice, but Ppp6c heterozygous tumors grew faster compared with those from the wild-type line. Ppp6c knockdown via siRNA in the Ppp6c heterozygous line promoted the accumulation of genomic damage and enhanced apoptosis relative to siRNA controls. We conclude that in the presence of BRAF(V600E) expression and UV-induced Trp53 mutation, Ppp6c haploinsufficiency promotes tumorigenesis.
根据TCGA数据库，在约10%的黑色素瘤患者肿瘤中发现了PPP6C（编码磷酸酶PP6）的突变，这些肿瘤中PPP6C突变与BRAF和NRAS突变共存。为了评估PP6在黑色素瘤致癌过程中的功能，我们构建了一种小鼠模型，在该模型中我们可以特异性诱导BRAF（V600E）表达并在黑素细胞中删除Ppp6c。在这些小鼠中，紫外线B照射后的黑色素瘤易感性呈现以下模式：Ppp6c半缺陷（杂合子）>Ppp6c野生型>Ppp6c缺陷（纯合子）肿瘤类型。对Ppp6c杂合子和野生型黑色素瘤肿瘤进行的二代测序显示，所有肿瘤均携带Trp53突变。然而，与Ppp6c野生型肿瘤相比，Ppp6c杂合子肿瘤显示出更高的特征1（有丝分裂/有丝分裂时钟）突变指数，表明细胞分裂增加。对源自Ppp6c杂合子或野生型黑色素瘤组织的细胞系进行分析表明，两者均可在裸鼠中形成肿瘤，但与野生型细胞系来源的肿瘤相比，Ppp6c杂合子肿瘤生长更快。相对于siRNA对照，在Ppp6c杂合子细胞系中通过siRNA敲低Ppp6c可促进基因组损伤的积累并增强细胞凋亡。我们得出结论，在存在BRAF（V600E）表达和紫外线诱导的Trp53突变的情况下，Ppp6c单倍体不足促进肿瘤发生。
