Role of Protein Kinase C in Colon Carcinogenesis

描述(申请人提供)：结肠癌是美国癌症死亡的第二大原因。它是一个多步骤的过程，涉及调控上皮细胞增殖、分化和生存的信号通路的渐进性变化。PKCbetaII可诱导结肠的过度增殖，是体内结肠癌发生的早期步骤所必需的。PKCbetaII通过激活新的PKCbetaII-&GT；COX-2-&GT；TGFbetaRII信号轴，诱导大鼠肠上皮(RIE)细胞抵抗TGFbeta的生长抑制作用。PKCbetaII还通过激活PKCbetaII-&gt；ras/MEK-&gt；PKCI/rac1信号通路诱导RIE细胞的侵袭性表型。在这项建议中要检验的总体假设是，PKCbetaII是人类结肠癌细胞转化表型所必需的。目的1验证PKCbetaII通过激活PKCbetaII-&gt；COX-&gt；？TGFbetaRII信号轴对人结肠癌细胞产生TGFbeta耐药的假说。目的2验证PKCbetaII在体外对人结肠癌细胞的非锚定生长和侵袭，以及对体内肿瘤的发生和转移的重要作用。PKCbetaII在人类结肠癌中的表达也将被评估，并与临床结果进行比较。目的利用两种互补的转基因K-RAS小鼠模型与PKCbeta KO小鼠杂交，验证PKCII在K-RAS介导的体内结肠癌发生中所必需的假说。目的4验证PKCbetaII和PKC/I在体内协同促进结肠癌发生的假说。PKC/I在PKCbetaII介导的结肠癌发生中的作用将在PKCbetaII转基因小鼠与表达PKC/I的转基因小鼠杂交中进行评估，PKCbetaII和PKC/I在结肠癌进展、侵袭和转移中的协同作用将在转基因PKCbetaII小鼠与表达固有活性PKC/I的小鼠杂交中进行评估。这些研究将确定PKCbetaII在人结肠癌细胞转化中的作用，PKCbetaII促进细胞转化的信号机制，以及PKCbetaII和PKC？致癌K-RAS在体内促进结肠癌的发生。他们还将评估PKCbetaII作为结肠癌潜在的治疗靶点和预后标记物，并开发新的结肠癌遗传模型，该模型可能适用于体内从起始到浸润性癌的所有阶段的结肠癌发生研究。

DESCRIPTION (provided by applicant): Colon cancer is the second leading cause of cancer death in the United States. It arises by a multi-step process involving progressive changes in signaling pathways that regulate epithelial cell proliferation, differentiation and survival. PKCbetaII induces hyperproliferation in the colon, and is required for early steps in colon carcinogenesis in vivo. PKCbetaII induces resistance to the growth inhibitory effects of TGFbeta in rat intestinal epithelial (RIE) cells through activation of a novel PKCbetaII->Cox-2->TGFbetaRII signaling axis. PKCbetaII also induces an invasive phenotype in RIE cells through activation of a PKCbetaII->Ras/Mek->PKCI/Rac1 signaling pathway. The overall hypothesis to be tested in this proposal is that PKCbetaII is required for the transformed phenotype in human colon cancer cells. Aim 1 will test the hypothesis that PKCbetaII confers TGFbeta resistance on human colon cancer cells by activating the PKCbetaII->Cox-->?TGFbetaRII signaling axis. Aim 2 will test the hypothesis that PKCbetaII is important for anchorage-independent growth and invasion of human colon cancer cells in vitro, and for tumorigenicity and metastasis in vivo. PKCbetaII expression will also be assessed in human colon cancers and compared with clinical outcome. Aim 3 will test the hypothesis that PKCII is required for K-Ras-mediated colon carcinogenesis in vivo using two complementary transgenic K-Ras mouse models crossed to PKCbeta KO mice. Aim 4 will test the hypothesis that PKCbetaII and PKC/I collaborate to promote colon carcinogenesis in vivo. The role of PKC/I in PKCbetaII-mediated colon carcinogenesis will be assessed in transgenic PKCbetaII mice crossed to transgenic mice expressing kinase-deficient PKC/I. Synergism between PKCbetaII and PKC/I in colon cancer progression, invasion and metastasis will be assessed in transgenic PKCbetaII mice crossed to mice expressing constitutively-active PKC/I. These studies will determine the role of PKCbetaII in human colon cancer cell transformation, the signaling mechanisms by which PKCbeta/II contributes to cellular transformation, and the relationship between PKCbetaII, PKC? and oncogenic K-Ras in promoting colon carcinogenesis in vivo. They will also assess PKCbetaII as a potential therapeutic target and prognostic marker in colon cancer, and develop new genetic models of colon cancer that may be suitable for studying all stages of colon carcinogenesis from initiation to invasive carcinoma in vivo.