Stem Cell Toxicology Group, National Toxicology Program Laboratory, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Toxicol Sci. 2018 Sep 1;165(1):40-49. doi: 10.1093/toxsci/kfy176.
Inorganic arsenic is a human carcinogen that can target the prostate. Accumulating evidence suggests arsenic can disrupt stem cell (SC) dynamics during the carcinogenic process. Previous work demonstrated arsenic-transformed prostate epithelial (CAsE-PE) cells can recruit prostate SCs into rapidly acquiring a cancer SC (CSC) phenotype via the secretion of soluble factors. Exosomes are small, membrane-derived vesicles that contain lipids, RNA, and proteins, and actively contribute to cancer initiation and progression when taken up by target cells. Here we hypothesized that CAsE-PE cells are recruiting SCs to a CSC-like phenotype via exosomal signaling. CAsE-PE cells secreted 700% more exosomes than parental RWPE-1 cells. CAsE-PE exosomes were enriched with oncogenic factors, including oncogenes (KRAS, NRAS, VEFGA, MYB, and EGFR), inflammation-related (cyclooxygenase-2, interleukin 1B (IL1B), IL6, transforming growth factor-β, and tumor necrosis factor-A), and apoptosis-related (CASP7, CASP9, and BCL2) transcripts, and oncogenesis-associated microRNAs. When compared with SCs cultured in exosome-depleted conditioned medium (CM), SCs cultured in CM containing CAsE-PE-derived exosomes showed increased (198%) matrix metalloproteinase activity and underwent an epithelial-to-mesenchymal transition in morphology, suggesting an exosome-mediated transformation. KRAS plays an important role in arsenic carcinogenesis. Although KRAS transcript (>24 000%) and protein (866%) levels were elevated in CAsE-PE exosomes, knock-down of KRAS in these cells only partially mitigated the CSC-like phenotype in cocultured SCs. Collectively, these results suggest arsenic impacts both exosomal quantity and cargo. Exosomal KRAS is only minimally involved in this recruitment, and additional factors (eg, cancer-associated miRNAs) likely also play a role. This work furthers our mechanistic understanding of how arsenic disrupts SC dynamics and influences the tumor microenvironment during carcinogenesis.
无机砷是一种人类致癌物，可靶向前列腺。越来越多的证据表明，砷可以在致癌过程中破坏干细胞 (SC) 的动力学。以前的工作表明，砷转化的前列腺上皮细胞 (CAsE-PE) 可以通过分泌可溶性因子招募前列腺 SC 迅速获得癌症干细胞 (CSC) 表型。外泌体是一种小的、膜衍生的囊泡，含有脂质、RNA 和蛋白质，当被靶细胞摄取时，它们会积极促进癌症的起始和进展。在这里，我们假设 CAsE-PE 细胞通过外泌体信号招募 SC 到 CSC 样表型。CAsE-PE 细胞分泌的外泌体比亲本 RWPE-1 细胞多 700%。CAsE-PE 外泌体富含致癌因子，包括癌基因 (KRAS、NRAS、VEFGA、MYB 和 EGFR)、炎症相关 (环氧化酶-2、白细胞介素 1B (IL1B)、IL6、转化生长因子-β和肿瘤坏死因子-A) 和凋亡相关 (CASP7、CASP9 和 BCL2) 转录物，以及与致癌相关的 microRNAs。与在缺乏外泌体的条件培养基 (CM) 中培养的 SC 相比，在含有 CAsE-PE 衍生外泌体的 CM 中培养的 SC 显示出基质金属蛋白酶活性增加 (198%)，形态上发生上皮间质转化，表明外泌体介导的转化。KRAS 在砷致癌作用中起重要作用。尽管 CAsE-PE 外泌体中的 KRAS 转录物 (>24000%) 和蛋白 (866%) 水平升高，但这些细胞中 KRAS 的敲低仅部分减轻了共培养 SC 中的 CSC 样表型。总的来说，这些结果表明砷既影响外泌体的数量又影响其内容物。外泌体 KRAS 仅在一定程度上参与这种招募，并且可能还有其他因素 (例如，癌症相关的 miRNAs) 也发挥作用。这项工作进一步加深了我们对砷如何破坏 SC 动力学以及在致癌过程中影响肿瘤微环境的机制理解。
