Rapamycin Potentiates TGFb Tumor Suppressor Function

描述（由申请人提供）：tgf β是一种有效的内源性肿瘤抑制因子，tgf β诱导的生长抑制在几乎所有人类癌症中都已被废除。引人注目的是，被认为介导tgfa诱导的生长停滞的Smad蛋白在大多数人类乳腺癌中存在并起作用。这些观察结果表明，在人类乳腺癌中，tgf - β信号本身并没有失活，但tgf - β信号从细胞周期调节中分离出来。我们发现，目前正在临床试验的抗癌药物雷帕霉素与TGFa协同诱导正常乳腺上皮细胞的生长停滞，并恢复tgf β诱导的Myc、Ras和E2F1转化上皮细胞的细胞周期停滞。雷帕霉素还能恢复tgf β诱导的几种人类癌细胞系的生长停滞。雷帕霉素与TGFbetaa合作抑制细胞增殖，这是由细胞周期蛋白依赖性激酶Cdk2失活引起的。Cdk2的抑制与细胞周期蛋白依赖性激酶抑制剂p27的结合增加有关。我们假设，雷帕霉素与TGFbeta通过增加与p27的关联以及通过E2F转录因子与Cdk2的解离来协同抑制Cdk2活性，从而抑制人乳腺癌细胞的增殖。我们进一步假设雷帕霉素与体内存在的tgf - β协同抑制肿瘤生长。这些假设将在以下具体目标中得到验证：1)确定tgf β +雷帕霉素治疗诱导未转化乳腺上皮细胞和人乳腺癌细胞生长停滞的机制；2)确定tgf β和雷帕霉素调节p27功能的机制；3)研究tgf β和雷帕霉素在体内抗肿瘤活性的相互作用。拟议的研究将采用乳腺癌作为模型系统，但将对广泛的肿瘤类型具有重要意义。这些研究的结果将为tgf β和雷帕霉素的协同生长抑制机制提供重要的见解，雷帕霉素是一种有效的内源性肿瘤抑制因子，雷帕霉素是一种目前正在进行乳腺癌临床试验的药物。

DESCRIPTION (provided by applicant): TGFbeta is a potent endogenous tumor suppressor and TGFbeta-induced growth arrest is abrogated in almost all human cancers. Strikingly, the Smad proteins thought to mediate TGFa-induced growth arrest are present and functional in most human mammary carcinomas. These observations suggest that in human breast cancer TGFa signaling is not inactivated per se, but that TGFbeta signaling becomes uncoupled from cell cycle regulation. We have discovered that rapamycin, an anti-cancer drug currently in clinical trials, cooperates with TGFa to induce growth arrest of normal mammary epithelial cells, and restores TGFbeta-induced cell cycle arrest in Myc, Ras, and E2F1 transformed epithelial cells. Rapamycin also restores TGFbeta-induced growth arrest in several human carcinoma cell lines. Rapamycin cooperates with TGFbetaa to inhibit cell proliferation, which results from inactivation of the cyclin-dependent kinase Cdk2. Inhibition of Cdk2 is associated with increased binding to the cyclin dependent kinase inhibitor p27. We hypothesize that rapamycin functions with TGFbeta to inhibit the proliferation of human mammary carcinoma cells by cooperatively inhibiting Cdk2 activity through increased association with p27, and through the dissociation of the E2F transcription factor from Cdk2. We further hypothesize that rapamycin cooperates with TGFbeta present in vivo to inhibit tumor growth. These hypotheses will be tested in the following Specific Aims: 1) Determine the mechanisms by which TGFbeta + rapamycin treatment induces growth arrest of no transformed mammary epithelial cells and human mammary carcinoma cells, 2) Determine the mechanisms by which TGFbeta and rapamycin regulate p27 function, and 3) Examine the interaction between TGFbeta and rapamycin anti-tumor activities in vivo. The proposed studies will employ breast cancer as a model system, but will have important implications for a wide array of tumor types. The results of these studies will yield important insights into the synergistic growth inhibitory mechanisms of TGFbeta and rapamycin, a potent endogenous tumor suppressor, and a drug currently in clinical trials against breast cancer, respectively.