Glass Joshua J, Phillips Phoebe A, Gunning Peter W, Stehn Justine R
Oncology Research Unit, School of Medical Sciences, UNSW Australia, Room 229, Wallace Wurth Building, Sydney, NSW, 2052, Australia.
Current address: ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, and Department of Microbiology and Immunology, The University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, 3010, Australia.
BMC Cancer. 2015 Oct 16;15:712. doi: 10.1186/s12885-015-1741-8.
Neuroblastoma is the most common extracranial solid tumor of childhood. The heterogeneous microenvironment of solid tumors contains hypoxic regions associated with poor prognosis and chemoresistance. Hypoxia implicates the actin cytoskeleton through its essential roles in motility, invasion and proliferation. However, hypoxia-induced changes in the actin cytoskeleton have only recently been observed in human cells. Tropomyosins are key regulators of the actin cytoskeleton and we hypothesized that tropomyosins may mediate hypoxic phenotypes.
Neuroblastoma (SH-EP) cells were incubated ± hypoxia (1 % O2, 5 % CO2) for up to 144 h, before examining the cytoskeleton by confocal microscopy and Western blotting.
Hypoxic cells were characterized by a more organized actin cytoskeleton and a reduced ability to degrade gelatin substrates. Hypoxia significantly increased mean actin filament bundle width (72 h) and actin filament length (72-96 h). This correlated with increased hypoxic expression and filamentous organization of stabilizing tropomyosins Tm1 and Tm2. However, isoform specific changes in tropomyosin expression were more evident at 96 h.
This study demonstrates hypoxia-induced changes in the recruitment of high molecular weight tropomyosins into the actin stress fibres of a human cancer. While hypoxia induced clear changes in actin organization compared with parallel normoxic cultures of neuroblastoma, the precise role of tropomyosins in this hypoxic actin reorganization remains to be determined.
神经母细胞瘤是儿童最常见的颅外实体瘤。实体瘤的异质性微环境包含与预后不良和化疗耐药相关的缺氧区域。缺氧通过其在运动、侵袭和增殖中的重要作用影响肌动蛋白细胞骨架。然而，缺氧诱导的肌动蛋白细胞骨架变化直到最近才在人类细胞中被观察到。原肌球蛋白是肌动蛋白细胞骨架的关键调节因子，我们推测原肌球蛋白可能介导缺氧表型。
将神经母细胞瘤（SH-EP）细胞在±缺氧（1% O₂，5% CO₂）条件下培养长达144小时，然后通过共聚焦显微镜和蛋白质印迹法检测细胞骨架。
缺氧细胞的特征是肌动蛋白细胞骨架更有序，降解明胶底物的能力降低。缺氧显著增加了平均肌动蛋白丝束宽度（72小时）和肌动蛋白丝长度（72 - 96小时）。这与稳定原肌球蛋白Tm1和Tm2的缺氧表达增加和丝状组织有关。然而，原肌球蛋白表达的亚型特异性变化在96小时时更为明显。
本研究证明了缺氧诱导高分子量原肌球蛋白募集到人类癌症的肌动蛋白应激纤维中发生变化。虽然与神经母细胞瘤的平行常氧培养相比，缺氧诱导了肌动蛋白组织的明显变化，但原肌球蛋白在这种缺氧肌动蛋白重组中的精确作用仍有待确定。
