Exploratory Research Laboratories, Research Center, Ajinomoto Pharmaceuticals, Co, Ltd, Kanagawa, Japan.
PLoS One. 2013 Nov 27;8(11):e82346. doi: 10.1371/journal.pone.0082346. eCollection 2013.
Differentiation of cancer stem cells (CSCs) into cancer cells causes increased sensitivity to chemotherapeutic agents. Although inhibition of mammalian target of rapamycin (mTOR) leads to CSC survival, the effect of branched chain amino acids (BCAAs), an mTOR complex 1 (mTORC1) activator remains unknown. In this study, we examined the effects of BCAA on hepatocellular carcinoma (HCC) cells expressing a hepatic CSC marker, EpCAM. We examined the effects of BCAA and/or 5-fluorouracil (FU) on expression of EpCAM and other CSC-related markers, as well as cell proliferation in HCC cells and in a xenograft mouse model. We also characterized CSC-related and mTOR signal-related molecule expression and tumorigenicity in HCC cells with knockdown of Rictor or Raptor, or overexpression of constitutively active rheb (caRheb). mTOR signal-related molecule expression was also examined in BCAA-treated HCC cells. In-vitro BCAA reduced the frequency of EpCAM-positive cells and improved sensitivity to the anti-proliferative effect of 5-FU. Combined 5-FU and BCAA provided better antitumor efficacy than 5-FU alone in the xenograft model. Stimulation with high doses of BCAA activated mTORC1. Knockdown and overexpression experiments revealed that inhibition of mTOR complex 2 (mTORC2) or activation of mTORC1 led to decreased EpCAM expression and little or no tumorigenicity. BCAA may enhance the sensitivity to chemotherapy by reducing the population of cscs via the mTOR pathway. This result suggests the utility of BCAA in liver cancer therapy.
肿瘤干细胞 (CSC) 的分化导致对化疗药物的敏感性增加。尽管抑制哺乳动物雷帕霉素靶蛋白 (mTOR) 会导致 CSC 存活，但作为 mTOR 复合物 1 (mTORC1) 激活剂的支链氨基酸 (BCAA) 的影响尚不清楚。在这项研究中，我们研究了 BCAA 对表达肝 CSC 标志物 EpCAM 的肝癌 (HCC) 细胞的影响。我们研究了 BCAA 和/或 5-氟尿嘧啶 (FU) 对 HCC 细胞中 EpCAM 和其他 CSC 相关标志物的表达以及细胞增殖的影响，以及在 HCC 细胞和异种移植小鼠模型中的作用。我们还通过敲低 Rictor 或 Raptor 或过表达组成型活性 Rheb (caRheb) 来表征 HCC 细胞中与 CSC 相关和 mTOR 信号相关的分子表达和致瘤性。还检查了 BCAA 处理的 HCC 细胞中 mTOR 信号相关分子的表达。体外 BCAA 降低了 EpCAM 阳性细胞的频率，并提高了对 5-FU 抗增殖作用的敏感性。与单独使用 5-FU 相比，联合使用 5-FU 和 BCAA 在异种移植模型中提供了更好的抗肿瘤疗效。高剂量 BCAA 刺激激活了 mTORC1。敲低和过表达实验表明，抑制 mTOR 复合物 2 (mTORC2) 或激活 mTORC1 导致 EpCAM 表达降低，几乎没有或没有致瘤性。BCAA 可能通过 mTOR 途径减少 CSCs 的数量从而提高对化疗的敏感性。这一结果表明 BCAA 在肝癌治疗中的应用价值。
