TGFBeta receptor antagonists as anticancer agents

转化生长因子-β是由许多癌组成性分泌和激活的多肽。它们有助于肿瘤的侵袭和转移，诱导血管生成和逃避免疫破坏的能力。出于同样的原因，癌细胞本身通常对TGF β介导的生长停滞是难治的。这种特殊的情况提出了一个问题，即阻断肿瘤来源的TGF β对正常组织（基质细胞、微血管内皮细胞和免疫细胞）的作用是否可能构成癌症治疗的新方法。在过去，已经采用了几种不同的策略来抵消TGF β在癌症和其他疾病中的生物学效应。这些方法包括使用TGF β中和抗体、TGF β结合蛋白（如核心蛋白聚糖）和TGF β 1反义RNA寡核苷酸。使用这些方法中的每一种的动物实验和小规模临床研究已经提供了TGF β的失活具有预测的抗肿瘤作用的概念证据。然而，这些化合物中的任何一种的更大规模的测试和进一步的临床开发已经被技术困难和有限的可用性所破坏。我们现在提出了一种通过靶向TGF β信号传导中的关键分子，即I型TGF β受体（TbetaR-I）丝氨酸-苏氨酸激酶来阻断TGF β作用的替代策略。小分子选择性TbetaR-I拮抗剂可能比上述方法更有效，并且在生产和生物利用度方面不应受到相同的限制。我们在SCIOS，Inc.的合作伙伴已经鉴定了几种有前景的先导化合物，其在体外无细胞以及细胞系统中抑制TbetaR-I激酶活性。此外，我们已经开发了测量TbetaR-I激酶抑制剂在体内的作用的能力，使用专有的高灵敏度抗体，选择性地检测磷酸化Smad 2。我们打算使用多种不同的TGF β生物学效应测定法来检查先导化合物对体外正常细胞的影响。然后将测试最好的TbetaR-I拮抗剂对小鼠中可移植肿瘤的抗肿瘤活性，特别关注它们对转移、血管生成和抗肿瘤免疫的作用。最后，将进行化合物在效力、选择性和生物利用度方面的优化，以获得具有有利毒性特征的类似物，其可以进一步开发用于临床用途。

Transforming Growth Factor-betas are polypeptides that are constitutively secreted and activated by many carcinomas. They contribute to the tumor's ability to invade and metastasize, to induce angiogenesis and to escape from immune destruction. By the same token, cancer cells themselves are generally refractory to TGFbeta-mediated growth arrest. This particular set of circumstances raises the question whether blocking the effects of tumor-derived TGFbeta on normal tissue (stromal cells, microvascular endothelial cells and immune cells) might constitute a novel approach to cancer treatment. In the past, several different strategies have been employed to counteract the biological effects of TGFbeta in cancer and other diseases. These have included the use of TGFbeta neutralizing antibodies, of TGFbeta- binding proteins, such as decorin, and of TGFbeta1 antisense RNA oligonucleotides. Animal experiments and small-scale clinical studies using each of these approaches have provided proof of concept that inactivation of TGFbeta has the predicted anti-tumor effect. However, larger scale testing and further clinical development of any of these compounds has been marred by technical difficulties and limited availability. We now propose an alternative strategy to blocking TGFbeta action by targeting the key molecule in TGFbeta signaling, i.e. the type I TGFbeta receptor (TbetaR-I) serine-threonine kinase. Small molecular selective TbetaR-I antagonists are likely to be more effective than the approaches mentioned above, and should not be subject to the same limitations in terms of production and bioavailability. Our collaborators at SCIOS, Inc. have identified several promising lead compounds that inhibit TbetaR-I kinase activity in cell-free as well as in cellular systems in vitro. In addition, we have developed the capability to measure effects of TbetaR-I kinase inhibitors in vivo, using a proprietary highly sensitive antibody that selectively detects phosphorylated Smad2. We intend to examine the effects of lead compounds against normal cells in vitro using a number of different assays for TGFbeta's biological effects. The best TbetaR-I antagonists will then be tested for their antitumor activity against transplantable tumors in mice, with particular attention to their effects on metastasis, angiogenesis and anti-tumor immunity. Finally, optimization of the compounds in terms of potency, selectivity and bioavailability will be carried out to derive analogs with a favorable toxicity profile that can be developed further for clinical use.