SRC KINASES IN COLON TUMORIGENESIS AND METASTASIS

结直肠癌目前是美国第二常见的癌症形式，估计每年发现15万例，5.6万人死于这种疾病。在过去的几年里，在识别导致疾病发展的基因变化方面取得了显著的进展。然而，这一进展尚未导致新疗法的开发，以延长晚期结肠癌患者的生存时间。一个很有希望的研究领域也可能导致新的治疗药物的开发，那就是研究结肠肿瘤细胞中的信号转导途径。我的实验室和其他人一直在研究src家族的非受体酪氨酸激酶的表达和活性，以及它们在结肠上皮细胞生长调节中的潜在作用。SRC激活是结肠癌最常见的表观遗传学事件之一，并发生在疾病发展的早期。我们已经证明，单独抑制Src活性可以降低人结肠癌细胞的致瘤性。为了确定src激活在肿瘤发生中的作用，我们研究了src介导的对生长控制至关重要的通路的调节。我们已经证明，Src的激活直接诱导血管内皮生长因子(VEGF)的表达，进而通过与粘着斑激酶(FAK)的结构性结合抑制细胞凋亡。建议续期的研究旨在更好地了解Src激活促进这些生物事件的分子基础。我们将检验这一假说，即异常的Src/FAK信号复合体解除对常见的“生存”途径下游中间体的调控，导致血管内皮生长因子的表达和细胞凋亡的抑制。虽然Src单独对肿瘤的生长可能很重要，但在肝转移瘤中，Src和Yes的激活都可以发生，并且具有不同的预后结果。因此，在这项提议中要检验的第二个假设是，Src和Yes的激活在肿瘤进展中扮演着不同于肿瘤形成生长的角色。该建议的具体目的是：(1)确定与粘着斑激酶(FAK)相互作用对Src/Yes显示其致癌和/或转移潜力的要求；(2)确定Src和FAK在介导导致血管内皮生长因子表达和抑制细胞凋亡的共同生存途径中的作用(S)；以及(3)确定其致瘤表型所需的Src的结构域，以及Src和Yes的特定结构域是否会导致所建立的结肠肿瘤细胞系的转移潜能的差异。这些研究的结果将阐明结肠肿瘤细胞发生生长和转移所需的重要信号转导途径，这些途径中的中间产物可能作为疾病的预后标志和/或靶点。

Colorectal carcinoma currently ranks as the second most frequent form of cancer in the United States, with an estimated 150,000 cases discovered each year, and 56,000 deaths as a result of the disease. In the past several years, remarkably progress has been made toward identifying the genetic changes which lead to the development of the disease. However, this progress has yet to result in the development of new therapies that prolong the survival of patients with late stage colon cancer. A promising area of research that may also lead to the development of novel therapeutic agents is the study of signal transduction pathways in colon tumor cells. My laboratory and others have been studying the expression and activity of the non-receptor tyrosine kinases of the src family and their potential roles in the growth regulation of colonic epithelial cells. Src activation is one of the most frequent epigenetic events in colon cancer, and occurs early in the development of the disease. We have demonstrated that inhibition of Src activity alone decreases tumorigenicity of human colon carcinoma cells. To determine the role of Src activation in tumorigenicity, we have examined the regulation of Src- mediated pathways critical to growth control. We have shown that Src activation directly induces expression of vascular endothelial growth factor (VEGF), and further, through constitutive association with focal adhesion kinase (FAK), inhibits apoptosis. The studies proposed for the renewal of this grant are designed to better understand the molecular basis by which Src activation promotes these biological events. We will test the hypothesis that aberrant Src/FAK signaling complexes deregulate downstream intermediates of a common "Survival" pathway leading to VEGF expression and inhibition of apoptosis. While Src alone may be important to tumorigenic growth, both Src and Yes activation can occur in hepatic metastases, and with different prognostic results. Therefore, a second hypothesis to be tested in this proposal is that Src and Yes activation play distinct roles in tumor progression from those of tumorigenic growth. The specific aims of the proposal are to: (1) determine the requirement of interaction with focal adhesion kinase (FAK) for Src/Yes to exhibit their tumorigenic and/or metastatic potentials; (2) determine the role(s) of Src and FAK in mediating a common survival pathway leading to expression of vascular endothelial growth factor and inhibiting apoptosis; and (3) Determine the structural domains of Src required for its tumorigenic phenotype and if specific structural domains of Src and Yes induce differences in metastatic potential of establish colon tumor cell lines. Results from these studies will clarify important signal transduction pathways required for tumorigenic growth and metastasis of colon tumor cells, and intermediates in these pathways may serve as prognostic markers and/or targets for the disease.