FIBRONECTIN REGULATION OF CARCINOMA APOPTOSIS

描述：纤维连接蛋白（FN）及其受体是肿瘤细胞存活的重要调节成分。我们已经确定，羧基末端肝素结合结构域和可变剪接的V区的FN是重要的，这个过程中，因为FN miniprotein（V + H-）含有突变的肝素结合结构域和V区的FN诱导鳞状细胞癌（SCC）细胞凋亡。相反，对应的野生型蛋白（V + H+）或其他不含V区的FN小蛋白促进这些细胞的存活。此外，在SCC细胞中，V + H-介导的细胞凋亡的速率比正常的原代角质形成细胞延迟。这些数据表明，致瘤性已使SCC细胞延迟其发生的细胞凋亡，以响应改变的基质，和FN的V区和肝素结合域调节这些细胞的生存。我们的初步数据表明，V + H-蛋白诱导迟发性SCC细胞凋亡的机制可能涉及硫酸软骨素蛋白聚糖和整合素受体，以及p53和c-myc介导的信号。在原代成纤维细胞中，这种凋亡机制是由硫酸软骨素蛋白聚糖，α 4整联蛋白介导的，并通过一个有趣的新途径，需要下调p53和c-myc。此外，由于p53在该机制中从细胞核重新定位到细胞膜，并且由于整合素相关信号分子粘着斑激酶（pp125FAK）和c-Jun N-末端激酶（JNK）在该途径中被抑制，这表明p53可能与整合素/FAK产生的信号进行通信。我们证实SCC细胞通过细胞表面蛋白多糖和整合素受体抵抗FN基质（V + H-）改变引起的凋亡。这启动了导致FAK、p53和c-myc下调的信号转导途径。其次，由于FN的V区在调节SCC细胞的侵袭、迁移和凋亡中起重要作用，我们认为FN的V区可能在SCC细胞的发病机制中起重要作用。我们将在以下具体目的中检验这些假设：（1）鉴定SCC细胞表面受体，这些受体参与延迟这些细胞中由V + H-FN蛋白诱导的凋亡，并将这些受体与原代角质形成细胞中存在的受体进行比较。(2)检测V + H-FN蛋白诱导的SCC细胞延迟凋亡的信号应答. (3)检测FN可变剪接V区在口腔低度和高度异型增生及口腔癌中的表达。这些研究将有助于解释调节肿瘤细胞生物学的一些细胞-基质相互作用和信号传导机制，并可能为口腔SCC的发病机制提供见解。

DESCRIPTION: Fibronectin (FN) and its receptors are important regulatory components in tumor cell survival. We have determined that the carboxyl-terminal heparin-binding domain and alternatively spliced V region of FN are important to this process, since a FN miniprotein (V+H-) containing a mutated heparin-binding domain and the V region of FN induces apoptosis of squamous cell carcinoma (SCC) cells. In contrast, the counterpart wildtype protein (V+H+) or other FN miniproteins not containing the V region promote survival of these cells. Furthermore, in SCC cells, the rate of V+H--mediated apoptosis is delayed compared to normal primary keratinocytes. These data suggest that tumorigenicity has enabled the SCC cells to delay their onset of apoptosis in response to an altered matrix, and that the V region and heparin-binding domain of FN regulate survival of these cells. Our preliminary data suggest that the mechanism by which the V+H- protein induces delayed SCC cell apoptosis may involve chondroitin sulfate proteoglycan and integrin receptors, and p53 and c-myc mediated signals. In primary fibroblasts, this apoptotic mechanism is mediated by a chondroitin sulfate proteoglycan, the alpha4 integrin, and by an intriguing new pathway that requires downregulation of p53 and c-myc. In addition, since p53 relocalizes from the nucleus to the cell membrane in this mechanism, and since the integrin-associated signaling molecule focal adhesion kinase (pp125FAK) and c-Jun N-terminal kinase (JNK) are depressed in this pathway, this suggests that p53 may communicate with integrin/FAK generated signals. We posit that SCC cells resist apoptosis in response to an altered FN matrix (V+H-) via cell surface proteoglycan and integrin receptors. This initiates a signal transduction pathway that leads to downregulation of FAK, p53 and c-myc. Secondarily, because of its important role in regulating SCC cell invasion, migration, and apoptosis, we posit that the V region of FN may be important to SCC cell pathogenesis. We will test these hypotheses in the following Specific Aims: (1) Identify the SCC cell-surface receptors involved in delaying apoptosis induced by the V+H- FN protein in these cells and compare these receptors to those present in primary keratinocytes. (2) Examine the SCC cell signaling response involved in delaying apoptosis induced by the V+H- FN protein. (3) Examine the expression of the alternatively spliced V region of FN in low grade and high-grade oral dysplasia and oral cancer. These studies will help explain some of the cell-matrix interactions and signaling mechanisms that regulate tumor cell biology, and may provide insights into the pathogenesis of oral SCC.