Wong Sophie Y, Ulrich Theresa A, Deleyrolle Loic P, MacKay Joanna L, Lin Jung-Ming G, Martuscello Regina T, Jundi Musa A, Reynolds Brent A, Kumar Sanjay
UC Berkeley-UC San Francisco Graduate Program in Bioengineering, Berkeley, California. Department of Bioengineering, University of California, Berkeley, Berkeley, California.
Department of Neurosurgery, University of Florida, Gainesville, Florida.
Cancer Res. 2015 Mar 15;75(6):1113-22. doi: 10.1158/0008-5472.CAN-13-3426. Epub 2015 Jan 29.
Tumor-initiating cells (TIC) perpetuate tumor growth, enable therapeutic resistance, and drive initiation of successive tumors. Virtually nothing is known about the role of mechanotransductive signaling in controlling TIC tumorigenesis, despite the recognized importance of altered mechanics in tissue dysplasia and the common observation that extracellular matrix (ECM) stiffness strongly regulates cell behavior. To address this open question, we cultured primary human glioblastoma (GBM) TICs on laminin-functionalized ECMs spanning a range of stiffnesses. Surprisingly, we found that these cells were largely insensitive to ECM stiffness cues, evading the inhibition of spreading, migration, and proliferation typically imposed by compliant ECMs. We hypothesized that this insensitivity may result from insufficient generation of myosin-dependent contractile force. Indeed, we found that both pharmacologic and genetic activation of cell contractility through RhoA GTPase, Rho-associated kinase, or myosin light chain kinase restored stiffness-dependent spreading and motility, with TICs adopting the expected rounded and nonmotile phenotype on soft ECMs. Moreover, constitutive activation of RhoA restricted three-dimensional invasion in both spheroid implantation and Transwell paradigms. Orthotopic xenotransplantation studies revealed that control TICs formed tumors with classical GBM histopathology including diffuse infiltration and secondary foci, whereas TICs expressing a constitutively active mutant of RhoA produced circumscribed masses and yielded a 30% enhancement in mean survival time. This is the first direct evidence that manipulation of mechanotransductive signaling can alter the tumor-initiating capacity of GBM TICs, supporting further exploration of these signals as potential therapeutic targets and predictors of tumor-initiating capacity within heterogeneous tumor cell populations.
肿瘤起始细胞（TIC）维持肿瘤生长，产生治疗抗性，并驱动后续肿瘤的发生。尽管人们已经认识到力学改变在组织发育异常中的重要性，并且普遍观察到细胞外基质（ECM）硬度强烈调节细胞行为，但关于机械转导信号在控制TIC肿瘤发生中的作用几乎一无所知。为了解决这个悬而未决的问题，我们将原发性人类胶质母细胞瘤（GBM）TIC培养在一系列硬度的层粘连蛋白功能化ECM上。令人惊讶的是，我们发现这些细胞对ECM硬度线索基本不敏感，避免了通常由顺应性ECM施加的对扩散、迁移和增殖的抑制。我们假设这种不敏感性可能是由于肌球蛋白依赖性收缩力产生不足所致。事实上，我们发现通过RhoA GTP酶、Rho相关激酶或肌球蛋白轻链激酶对细胞收缩性进行药理学和基因激活，可恢复硬度依赖性扩散和运动性，TIC在柔软的ECM上呈现预期的圆形且不运动的表型。此外，RhoA的组成性激活在球体植入和Transwell模型中均限制了三维侵袭。原位异种移植研究表明，对照TIC形成具有经典GBM组织病理学特征的肿瘤，包括弥漫性浸润和继发性病灶，而表达RhoA组成性活性突变体的TIC产生边界清晰的肿块，平均生存时间提高了30%。这是第一个直接证据，表明操纵机械转导信号可以改变GBM TIC的肿瘤起始能力，支持进一步探索这些信号作为潜在治疗靶点以及异质性肿瘤细胞群体中肿瘤起始能力的预测指标。
