MacDonald Tyler M, Thomas Lynn N, Gupta Aurinjoy, Barnes Penelope J, Too Catherine Kl
Department of Biochemistry & Molecular Biology, Faculty of Medicine, Dalhousie University Halifax, NS, Canada.
Department of Pathology, Faculty of Medicine, Dalhousie University Halifax, NS, Canada.
Am J Cancer Res. 2020 May 1;10(5):1321-1343. eCollection 2020.
Plasma membrane carboxypeptidase-D (CPD) hydrolyzes C-terminal arginine (Arg) from extracellular substrates, and Arg is converted into nitric oxide (NO) in the cell. CPD is upregulated by prolactin (PRL) and androgens in breast cancer (BCa) cells, increasing NO production to promote cell survival. EDD E3 ubiquitin ligase, upregulated by PRL/androgens, is implicated in TORC1 signaling. This study investigated CPD and EDD in triple-negative (TNBC) and HER2+ BCa. Kaplan-Meier analysis showed a negative correlation between CPD or EDD mRNA expression in TNBC patients and relapse-free survival. Immunohistochemistry showed that benign and malignant breast tissues stained abundantly for the PRL receptor (PRLR) and androgen receptor (AR). CPD and EDD staining were elevated in TNBC and HER2+ tumors as compared to benign tissues. In TNBC/HER2+ cell lines, CPD and EDD protein expression were upregulated by PRL or synthetic androgen methyltrienolone (R1881) at 3-6 h. PRL/R1881-induced CPD in TNBC and HER2+ cells increased intracellular NO production, which was abolished by PRLR antagonist ∆1-9-G129R-hPRL and AR antagonist flutamide. In turn, treatment with NO increased viability and decreased apoptosis in Arg-deprived TNBC cells. Cell viability and apoptosis were also affected in HER2+ cells with CPD knockdown. Lastly, EDD knockdown decreased PRL/R1881-induced phosphorylation of initiation factor 4E binding protein-1 and decreased 4E release in TNBC cells. In summary, PRL/R1881-induced CPD promotes TNBC/HER2+ cell survival through production of NO, and EDD promotes TNBC cell survival by TORC1 activation. This study implicates CPD and EDD as useful therapeutic targets for TNBC/HER2+ tumors, and suggests that PRLR and AR blockade are also beneficial to these patients.
质膜羧肽酶 - D（CPD）可水解细胞外底物的C末端精氨酸（Arg），Arg在细胞内转化为一氧化氮（NO）。在乳腺癌（BCa）细胞中，CPD受催乳素（PRL）和雄激素上调，增加NO生成以促进细胞存活。EDD E3泛素连接酶受PRL/雄激素上调，参与TORC1信号传导。本研究调查了三阴性（TNBC）和HER2 + BCa中的CPD和EDD。Kaplan - Meier分析显示TNBC患者中CPD或EDD mRNA表达与无复发生存之间呈负相关。免疫组织化学显示良性和恶性乳腺组织中催乳素受体（PRLR）和雄激素受体（AR）染色丰富。与良性组织相比，TNBC和HER2 +肿瘤中CPD和EDD染色升高。在TNBC/HER2 +细胞系中，PRL或合成雄激素甲基三烯olone（R1881）在3 - 6小时可上调CPD和EDD蛋白表达。PRL/R1881诱导的TNBC和HER2 +细胞中的CPD增加细胞内NO生成，这被PRLR拮抗剂∆1 - 9 - G129R - hPRL和AR拮抗剂氟他胺消除。反过来，用NO处理可增加精氨酸缺乏的TNBC细胞的活力并减少细胞凋亡。CPD敲低的HER2 +细胞的细胞活力和凋亡也受到影响。最后，EDD敲低降低了PRL/R1881诱导的起始因子4E结合蛋白 - 1的磷酸化，并降低了TNBC细胞中4E的释放。总之，PRL/R1881诱导的CPD通过产生NO促进TNBC/HER2 +细胞存活，而EDD通过激活TORC1促进TNBC细胞存活。本研究表明CPD和EDD是TNBC/HER2 +肿瘤有用的治疗靶点，并表明阻断PRLR和AR对这些患者也有益。
