Cao Juxiang, Dai Xiangpeng, Wan Lixin, Wang Hongshen, Zhang Jinfang, Goff Philip S, Sviderskaya Elena V, Xuan Zhenyu, Xu Zhixiang, Xu Xiaowei, Hinds Philip, Flaherty Keith T, Faller Douglas V, Goding Colin R, Wang Yongjun, Wei Wenyi, Cui Rutao
Department of Pharmacology and Experimental Therapeutics, Boston University Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA.
Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA.
Sci Signal. 2015 Sep 1;8(392):ra87. doi: 10.1126/scisignal.aab1995.
The anaphase-promoting complex or cyclosome with the subunit Cdh1 (APC/C(Cdh1)) is an E3 ubiquitin ligase involved in the control of the cell cycle. Here, we identified sporadic mutations occurring in the genes encoding APC components, including Cdh1, in human melanoma samples and found that loss of APC/C(Cdh1) may promote melanoma development and progression, but not by affecting cell cycle regulatory targets of APC/C. Most of the mutations we found in CDH1 were those associated with ultraviolet light (UV)-induced melanomagenesis. Compared with normal human skin tissue and human or mouse melanocytes, the abundance of Cdh1 was decreased and that of the transcription factor PAX3 was increased in human melanoma tissue and human or mouse melanoma cell lines, respectively; Cdh1 abundance was further decreased with advanced stages of human melanoma. PAX3 was a substrate of APC/C(Cdh1) in melanocytes, and APC/C(Cdh1)-mediated ubiquitylation marked PAX3 for proteolytic degradation in a manner dependent on the D-box motif in PAX3. Either mutating the D-box in PAX3 or knocking down Cdh1 prevented the ubiquitylation and degradation of PAX3 and increased proliferation and melanin production in melanocytes. Knocking down Cdh1 in melanoma cells in culture or before implantation in mice promoted doxorubicin resistance, whereas reexpressing wild-type Cdh1, but not E3 ligase-deficient Cdh1 or a mutant that could not interact with PAX3, restored doxorubicin sensitivity in melanoma cells both in culture and in xenografts. Thus, our findings suggest a tumor suppressor role for APC/C(Cdh1) in melanocytes and that targeting PAX3 may be a strategy for treating melanoma.
后期促进复合物或带有亚基Cdh1的细胞周期体（APC/C(Cdh1)）是一种参与细胞周期调控的E3泛素连接酶。在此，我们在人类黑色素瘤样本中鉴定出编码APC组分（包括Cdh1）的基因中发生的散发性突变，发现APC/C(Cdh1)的缺失可能促进黑色素瘤的发生和进展，但并非通过影响APC/C的细胞周期调控靶点来实现。我们在CDH1中发现的大多数突变是与紫外线（UV）诱导的黑色素瘤发生相关的突变。与正常人类皮肤组织以及人类或小鼠黑色素细胞相比，Cdh1的丰度在人类黑色素瘤组织以及人类或小鼠黑色素瘤细胞系中分别降低，而转录因子PAX3的丰度则升高；随着人类黑色素瘤分期的进展，Cdh1丰度进一步降低。PAX3是黑色素细胞中APC/C(Cdh1)的底物，APC/C(Cdh1)介导的泛素化以依赖于PAX3中D盒基序的方式标记PAX3进行蛋白水解降解。突变PAX3中的D盒或敲低Cdh1均可阻止PAX3的泛素化和降解，并增加黑色素细胞的增殖和黑色素生成。在培养的黑色素瘤细胞中或在植入小鼠前敲低Cdh1可促进阿霉素耐药，而重新表达野生型Cdh1，但不是E3连接酶缺陷型Cdh1或不能与PAX3相互作用的突变体，可在培养物和异种移植中恢复黑色素瘤细胞对阿霉素的敏感性。因此，我们的研究结果表明APC/C(Cdh1)在黑色素细胞中具有肿瘤抑制作用，并且靶向PAX3可能是治疗黑色素瘤的一种策略。
