BACKGROUND Sirtuin-7 (SIRT7) is associated with the maintenance of tumorigenesis. However, its functional roles and oncogenic mechanisms in prostate cancer (PCa) are poorly understood. Here, we investigated the roles and underlying molecular mechanisms of SIRT7 in PCa cell growth and androgen-induced autophagy. METHODS The LNCap and 22Rv1 PCa cell lines were subjected to quantitative reverse transcription (RT)-PCR to characterize their genes encoding SIRT7, AR, and SMAD4. The proteins produced from these genes were quantified by western blotting and immunoprecipitation analysis. SIRT7-depleted cells were produced by transfection with plasmid vectors bearing short hairpin RNAs against SIRT7. The proliferation of each cell line was assessed by CCK8 and EdU assays. Autophagic flux was tracked by mRFP-GFP-LC3 adenovirus under an immunofluorescence microscope. Apoptosis was evaluated by flow cytometry. Tumors were induced in mouse axillae by injection of the cell lines into mice. Tumor morphology was examined by immunohistochemistry and relative tumor growth and metastases were compared by a bioluminescence-based in vivo imaging system. RESULTS SIRT7 depletion significantly inhibited cell proliferation, androgen-induced autophagy, and invasion in LNCap and 22Rv1 cells (in vitro) and mouse xenograft tumors induced by injection of these cells (in vivo). SIRT7 knockdown also increased the sensitivity of PCa cells to radiation. Immunohistochemical analysis of 93 specimens and bioinformatic analysis revealed that SIRT7 expression was positively associated with androgen receptor (AR). Moreover, the AR signal pathway participated in SIRT7-mediated regulation of PCa cell proliferation, autophagy, and invasion. SIRT7 depletion downregulated the AR signal pathway by upregulating the level of SMAD4 protein in PCa cells. CONCLUSION SIRT7 plays an important role in the development and progression of human PCa and may be a promising prognostic marker for prostate cancer.

中文翻译：

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SIRT7耗竭通过抑制前列腺癌中的AR信号传导来抑制细胞增殖和雄激素诱导的自噬。

背景Sirtuin-7（SIRT7）与肿瘤发生的维持有关。然而，人们对其功能在前列腺癌（PCa）中的作用和致癌机理了解甚少。在这里，我们调查了SIRT7在PCa细胞生长和雄激素诱导的自噬中的作用和潜在的分子机制。方法对LNCap和22Rv1 PCa细胞株进行定量逆转录（RT）-PCR，以表征其编码SIRT7，AR和SMAD4的基因。通过蛋白质印迹和免疫沉淀分析定量从这些基因产生的蛋白质。通过用带有针对SIRT7的短发夹RNA的质粒载体转染，生产出SIRT7缺失的细胞。通过CCK8和EdU测定评估每种细胞系的增殖。在免疫荧光显微镜下，通过mRFP-GFP-LC3腺病毒追踪自噬通量。通过流式细胞术评估细胞凋亡。通过将细胞系注射到小鼠中，在小鼠腋窝中诱导肿瘤。通过免疫组织化学检查肿瘤形态，并通过基于生物发光的体内成像系统比较相对肿瘤的生长和转移。结果SIRT7耗竭显着抑制LNCap和22Rv1细胞（体外）和通过注射这些细胞（体内）诱导的小鼠异种移植瘤中的细胞增殖，雄激素诱导的自噬和侵袭。SIRT7敲低还增加了PCa细胞对辐射的敏感性。对93个标本进行的免疫组织化学分析和生物信息学分析表明，SIRT7表达与雄激素受体（AR）正相关。此外，AR信号通路参与了SIRT7介导的PCa细胞增殖，自噬和侵袭的调控。SIRT7耗竭通过上调PCa细胞中SMAD4蛋白的水平来下调AR信号通路。结论SIRT7在人类PCa的发展和进程中起着重要作用，并且可能是前列腺癌的有希望的预后标志物。