SRC KINASES IN COLON TUMORIGENESIS AND METASTASIS

结直肠癌目前是美国第二大常见的癌症，估计每年发现15万例，有5.6万人死于这种疾病。在过去几年中，在确定导致该疾病发展的基因变化方面取得了显著进展。然而，这一进展尚未导致新疗法的发展，以延长晚期结肠癌患者的生存期。结肠肿瘤细胞信号转导途径的研究是一个有前景的研究领域，也可能导致新的治疗药物的开发。我的实验室和其他人一直在研究src家族非受体酪氨酸激酶的表达和活性及其在结肠上皮细胞生长调节中的潜在作用。Src激活是结肠癌中最常见的表观遗传事件之一，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激活在致瘤性中的作用，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激活直接诱导血管内皮生长因子（VEGF）的表达，并进一步通过与局灶黏附激酶（FAK）的组成性关联，抑制细胞凋亡。为续期提出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。我们将验证异常Src/FAK信号复合物解除了导致VEGF表达和细胞凋亡抑制的常见“生存”途径的下游中间体的假设。虽然Src单独可能对致瘤性生长很重要，但Src和Yes激活都可能发生在肝转移中，并且具有不同的预后结果。因此，本提案需要验证的第二个假设是Src和Yes激活在肿瘤进展中发挥不同于致瘤性生长的作用。该提案的具体目的是：(1)确定Src/Yes与病灶粘附激酶（FAK）相互作用的要求，以显示其致瘤性和/或转移潜力；(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常见生存途径中的作用；(3)确定Src致瘤表型所需的结构域，以及Src和Yes的特定结构域是否诱导已建立的结肠肿瘤细胞系转移潜能的差异。这些研究的结果将阐明结肠肿瘤细胞致瘤生长和转移所需的重要信号转导通路，这些通路中的中间体可能作为该疾病的预后标记物和/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.