REGULATION OF GROWTH BY ALPHA V INTEGRINS

整合素αvbeta6在口腔鳞状细胞癌中广泛表达，是口腔鳞状细胞癌细胞系体外增殖、迁移和迁移所必需的。已知的与αvbeta6相互作用的细胞外基质配体是纤维连接蛋白和腱连接蛋白，它们丰富地存在于鳞状细胞的基质中。此外，最近发现αvbeta6可以结合和激活潜伏的转化生长因子β。基因敲除小鼠的研究强烈表明，αvbeta6是激活肺内TGFbeta1所必需的。已知TGFbeta还可调节多种类型癌症的增殖和侵袭，并对肿瘤生长起抑制或刺激作用。因此，αvbeta6可能通过激活转化生长因子β间接影响鳞癌的进展，或直接通过其胞质结构域传递信号。我们的初步数据显示，两种不同的口腔鳞状细胞癌株的增殖强烈依赖于αvbeta6，并且针对αvbeta6的中和抗体干扰了一种称为HSC-3的高侵袭性口腔鳞癌株在裸鼠体内的生长。为了更详细和更严格地描述整合素αv在鳞状细胞癌生长中的作用，我们将使用几个模型系统，包括人鳞状细胞癌细胞系的面板和化学或遗传诱导的小鼠鳞状细胞癌。将使用几种不同的实验方法来评估αv整合素在肿瘤细胞生长中的作用。首先，我们将使用中和抗体或配体类似物破坏αvbeta6功能，或所有αv整合素的功能。我们还将开发具有更高体内效力的中和抗体，并在不同的体内模型中测试它们对鳞癌生长的影响。其次，我们将在SCC细胞系中操纵αvbeta6的表达，并研究这些细胞系在体内的生长情况。第三，在Tet-On系统的控制下，我们将产生有条件地在舌上皮细胞中过度表达Beta6的转基因小鼠。在这些小鼠中，将研究在不同进展阶段存在或不存在αvbeta6的化学致癌作用。此外，我们还将研究αvbeta6对鳞癌生长的影响是通过激活转化生长因子β还是通过直接的alphavbeta6信号来实现的。这些研究的长期目标是详细了解alphav整合素在调节口腔鳞状细胞癌生长、侵袭和进展的途径中的作用。此外，我们正在研究将甲型整合素中和抗体用于口腔癌免疫治疗的可能性。

The alphavbeta6 integrin is frequently neo-expressed in human oral squamous cell carcinoma (SCCs), and is required for proliferation and migration and migration of SCC cell lines in vitro. The known extracellular matrix ligands that interact with alphavbeta6 are fibronectin and tenascin, which are abundant in the stromal matrix of SCCs. In addition, alphavbeta6 was recently shown to bind and activate latent TGFbeta. Knockout mouse studies strongly suggest that alphavbeta6 is required for activation of TGFbeta1 in the lung. TGFbeta is also known to regulate proliferation and invasion of many types of carcinomas, and to exert either inhibitory or stimulatory effects on carcinoma growth. Thus, alphavbeta6 may influence SCC progression either indirectly via activation of TGFbeta, or directly by transmitting signals through its cytoplasmic domain. Our preliminary data show that the proliferation of two different oral SCC lines strongly depends on alphavbeta6, and that a neutralizing antibody to alphavbeta6 interferes with the growth in nude mice of a highly aggressive oral SCC line, termed HSC-3. To characterize the role of alphav integrins in SCC growth in more detail and under more stringent conditions, we will employ several model systems, including panels of human SCC cell lines and chemically or genetically induced SCCs in mice. Several different experimental approaches will be used to assess alphav integrin function in tumor cell growth. First, we will disrupt alphavbeta6 function, or the function of all alphav integrins, using neutralizing antibodies or ligand analogs. We will also develop neutralizing antibodies with higher in vivo potency, and test their effects on SCC growth in different in vivo models. Second, we will manipulate alphavbeta6 expression in SCC cell lines and study growth of these cell lines in vivo. Third, we will generate transgenic mice that conditionally over-express beta6 in the tongue epithelium, under control of the Tet-On system. In these mice, chemical carcinogenesis in the presence or absence of alphavbeta6 at different stages of progression will be studied. In addition, we will investigate whether alphavbeta6 effects on SCC growth are mediated through activation of TGFbeta or through direct alphavbeta6 signaling.. The long-term goal of these studies is to provide a detailed understanding of the involvement of alphav integrins in the pathways that regulate oral SCC growth, invasion and progression. In addition, we are investigating the possibility of using neutralizing antibodies to alphav integrins for immunotherapy of oral cancer.