Esteban-Barragán Miguel A, Avila Pilar, Alvarez-Tejado Miguel, Gutiérrez M Dolores, García-Pardo Angeles, Sánchez-Madrid Francisco, Landázuri Manuel O
Servicio de Inmunología, Hospital de la Princesa, Universidad Autónoma de Madrid (UAM), Diego de León 62, 28006 Madrid, Spain.
Cancer Res. 2002 May 15;62(10):2929-36.
The von Hippel-Lindau tumor suppressor gene (VHL) is absent or inactivated in the VHLcancer syndrome and in most sporadic renal cancers. VHL is requiredfor the assembly of a proper extracellular fibronectin matrix, although the exact mechanism remains unknown. In this report, we demonstrate that 786-O renal cancer cells are unable to organize an adequate matrix even in the presence of an excess of exogenous fibronectin. Because the formation of integrin fibrillar adhesions plays a pivotal role in the organization of extracellular fibronectin, we next examined the expression and subcellular distribution of integrins in VHL- cells and their wild-type VHL stably transfected counterparts. The levels of beta1 and alphav integrins were increased in VHL- cells when compared with VHL+ transfectants. Early after plating, both VHL+ and VHL- cells were capable of assembling classic "patch-like" alphav focal contacts. As the culture advanced and cells became confluent, alphav integrins partly relocated to the intercellular junctions in VHL+ transfectants, which then developed large beta1 fibrillar-type adhesions and anchored firmly to the substrate. In contrast, confluent VHL- cells were unable to assemble beta1 fibrillar adhesions, and alphav focal contacts remained unchanged at all stages of the culture. Exogenous activation of beta1 integrins with either divalent cations or activating antibodies partly restored the capability of VHL- cells to assemble beta1 fibrillar adhesions and fibronectin fibers. Finally, pulse-chase studies of metabolically labeled 786-O cells revealed that the maturation of the common beta1-integrin chain was delayed in VHL- cells when compared with VHL+ cells. Our results show that VHL is an important regulator of integrins and is essential for the formation of beta1 fibrillar adhesions. These findings help to explain the abnormal extracellular matrix organization and increased motility of VHL- renal cancer cells.
在VHL癌症综合征和大多数散发性肾癌中，冯·希佩尔-林道肿瘤抑制基因（VHL）缺失或失活。尽管确切机制尚不清楚，但VHL是形成合适的细胞外纤连蛋白基质所必需的。在本报告中，我们证明786 - O肾癌细胞即使在存在过量外源性纤连蛋白的情况下也无法组织形成足够的基质。由于整合素纤维状黏附的形成在细胞外纤连蛋白的组织中起关键作用，接下来我们研究了VHL缺失细胞及其稳定转染野生型VHL的对应细胞中整合素的表达和亚细胞分布。与VHL阳性转染细胞相比，VHL缺失细胞中β1和αv整合素的水平升高。接种后早期，VHL阳性和VHL缺失细胞都能够组装经典的“斑块样”αv黏着斑。随着培养进行且细胞汇合，αv整合素部分重新定位于VHL阳性转染细胞的细胞间连接，随后形成大的β1纤维状黏附并牢固地锚定在底物上。相比之下，汇合的VHL缺失细胞无法组装β1纤维状黏附，并且αv黏着斑在培养的所有阶段都保持不变。用二价阳离子或激活抗体对外源性β1整合素进行激活，部分恢复了VHL缺失细胞组装β1纤维状黏附及纤连蛋白纤维的能力。最后，对代谢标记的786 - O细胞进行脉冲追踪研究发现，与VHL阳性细胞相比，VHL缺失细胞中常见的β1整合素链的成熟延迟。我们的结果表明，VHL是整合素的重要调节因子，对β1纤维状黏附的形成至关重要。这些发现有助于解释VHL缺失肾癌细胞异常的细胞外基质组织和增加的运动性。
