MECHANISMS OF TGE-B RESISTANCE IN COLON CARCINOMA CELLS

TGF-β可能在结肠癌的治疗中取得成功 因为它抑制应答性人结肠癌的增殖 细胞和elastomic分化样效应。 然而，大约50% 测试的结肠癌细胞对TGF-β无反应。 整体 本提案的目标是扩展先前建立的模型系统 人结肠癌细胞中的TGF-β抗性，并利用这种 模型系统，以确定潜在的TGF-β的可能机制 阻力 从这一建议中获得的结果将确定目标 用于开发药物， TGF-β对上皮性结肠肿瘤的抑制作用，或 发展对TGF-β生长调节的抗性。 领域 旨在阐明的作用机制和/或 对TGF-β的抗性包括：（1）受体结合的表征 和受体亚型在抗性和敏感克隆，（2） G蛋白和ras的参与或改变的研究 TGF-β（G 蛋白质似乎参与TGF-β诱导的有丝分裂， 成纤维细胞），和（3）研究调节的改变 核原癌基因c-myc、c-fos和c-jun的表达（和 它们的蛋白质产物）以鉴定这些分子中的任何改变 信号转导和转录调控之间的联系。 先前 研究表明，最初鉴定的TGF-β抗性克隆中有3/4 过度表达c-myc，这一事件已被证明可以改变TGF-β 其他细胞的反应。 额外的实验将集中在细胞环境作为一个 改变TGF-β反应性的介质。 生产过剩，或 对生长刺激性自分泌因子的反应性 克隆可能超过TGF-β的任何潜在抑制作用。 因此，EGF，TGF-α和EGF受体参与TGF-β 阻力将得到解决。

TGF-beta may potentially be successful in the treatment of colon cancer since it inhibits the proliferation of responsive human colon carcinoma cells and elicits differentiation-like effects. However, approximately 50% of colon carcinoma cells tested were unresponsive to TGF-beta. The overall goal of this proposal is to expand a previously-established model system for TGF-beta resistance in human colon carcinoma cells, and to utilize this model system to identify possible mechanisms underlying TGF-beta resistance. The result obtained from this proposal will identify targets for the development of drugs which will either mimic the inhibitory effects of TGF-beta on epithelial colon tumors or which will eliminate the development of resistance to growth regulation by TGF-beta. Areas of investigation aimed at elucidating mechanisms of action of and/or of resistance to TGF-beta include: (1) Characterization of receptor binding and receptor subtypes in the resistant and sensitive clones, (2) Investigation of the involvement or alteration of G proteins and of ras oncoproteins in transduction of cellular signals generated by TGF-beta (G proteins appear to be involved in TGF-beta-induced mitogenesis in fibroblast cells), and (3) Investigation of alterations in the regulation of expression of the nuclear proto-oncogenes c-myc, c-fos, and c-jun (and their protein products) to identify any alterations in these molecular links between signal transduction and transcriptional regulation. Previous work indicated that 3/4 of initially-identified TGF-Beta-resistant clones over-expressed c-myc, an event which has been shown to alter TGF-Beta responsiveness in other cells. Additional experiments will be focused on the cellular environment as a mediator of altered TGF-beta responsiveness. Overproduction of, or responsiveness to, growth stimulatory autocrine factors in the resistant clones may outweigh any potential inhibitory effects of TGF-beta. Therefore, involvement of EGF, TGF-alpha and the EGF receptor in TGF-beta resistance will be addressed.