Department of Microbiology and Radiation Oncology, and NYU Cancer Institute, New York University School of Medicine, New York, New York, USA.
Cancer Res. 2013 Jul 15;73(14):4571-8. doi: 10.1158/0008-5472.CAN-13-0218. Epub 2013 May 30.
The tumor microenvironment is a crucial player in the ability of cancer cells to acquire the ability to survive under the hypoxic environment and promote migration and invasion. Translational regulation is an essential part of cancer development and progression. Protein synthesis consumes considerable cellular metabolic energy and is therefore highly regulated, in turn controlling tumor cell proliferation and survival in extreme tumor-host conditions. Protein synthesis is typically downregulated by hypoxia, impairing cell proliferation and migration. Here, we show that breast cancer cells expressing integrin αvβ3, when engaging the extracellular matrix (ECM) protein vitronectin, strongly upregulate both mTOR activity and cap-dependent mRNA translation, which overrides their inhibition by hypoxia and facilitates tumor cell invasion. Interaction of vitronectin with integrin αvβ3 results in the continued activation of the kinase mTOR despite hypoxia through a mechanism that is dependent on integrin-linked kinase but is independent of focal adhesion kinase. Continuous activation of mTOR despite hypoxia involves release of translation initiation factor eIF4E from its repressor protein 4E-BP1, which is required for vitronectin-mediated tumor cell invasion. As integrin αvβ3 is associated with breast cancer cell invasion and metastasis to bone, we propose that the interaction with specific ECM proteins can influence cancer cell invasion, in part, by hyperactivation of mTOR, thereby promoting and sustaining protein synthesis under hypoxic conditions.
肿瘤微环境是癌细胞在缺氧环境中获得生存能力、促进迁移和侵袭的关键因素。翻译调控是癌症发生和发展的重要组成部分。蛋白质合成消耗大量细胞代谢能量,因此受到高度调控,进而控制肿瘤细胞在极端肿瘤宿主条件下的增殖和存活。通常情况下,缺氧会下调蛋白质合成,从而抑制细胞增殖和迁移。在这里,我们表明,表达整合素 αvβ3 的乳腺癌细胞在与细胞外基质(ECM)蛋白 vitronectin 结合时,强烈地上调 mTOR 活性和帽依赖性 mRNA 翻译,这克服了缺氧对其的抑制作用,并促进了肿瘤细胞的侵袭。vitronectin 与整合素 αvβ3 的相互作用导致尽管存在缺氧,激酶 mTOR 仍持续激活,这一机制依赖于整合素连接激酶,但不依赖于粘着斑激酶。尽管缺氧,mTOR 的持续激活涉及翻译起始因子 eIF4E 从其抑制剂 4E-BP1 中释放出来,这是 vitronectin 介导的肿瘤细胞侵袭所必需的。由于整合素 αvβ3 与乳腺癌细胞的侵袭和骨转移有关,我们提出与特定的 ECM 蛋白相互作用可以通过过度激活 mTOR 来影响肿瘤细胞的侵袭,从而在缺氧条件下促进和维持蛋白质合成。