Acquired Resistance to TGFBR1 inhibitors and cancer stem cell outgrowth

描述（由申请人提供）：我们最近证明，体内小分子TGF¿R1抑制剂对转化生长因子- （TGF¿）信号通路的慢性抑制导致小鼠皮肤癌模型中耐药化学引发癌的生长。这是关于TGF¿抑制剂获得性耐药的第一篇报道。此外，这些耐药癌具有侵袭性表型，并表现出皮肤干细胞标记物表达的基因富集。目前的研究目标是确定这种指示癌症干细胞的分子谱是否由于功能性干细胞区室的扩展，并阐明获得耐药性的分子机制。待验证的假设是，TGF¿信号通路的慢性药物抑制诱导耐药状态，导致Smad2/3信号组成性升高，支持CSC室的扩张。在目的1中，我们计划在小鼠皮肤化学诱导癌变模型中使用体内和体外方法来证明这一假设。在目标2中，我们将通过使用靶基因外显子的超深度测序对档案组织进行突变筛选，并在体外进行Smad2激活激酶筛选，来解决获得性耐药和CSC生长的分子机制。了解对TGF -阻断疗法获得性耐药的分子机制有可能改善治疗策略和下一代药物设计。此外，由于CSC与TGF¿信号之间的密切联系，这一知识很有希望为CSC维持的分子调控提供见解，并可能为攻击CSC提供新的药物靶点。

DESCRIPTION (provided by applicant): We have recently demonstrated that chronic inhibition of the Transforming Growth Factor-¿ (TGF¿) signaling pathway by a small molecule TGF¿R1 inhibitor in vivo leads to the outgrowth of drug resistant chemically-initiated carcinomas in a mouse skin cancer model. This is the first report of development of acquired drug resistance to a TGF¿ inhibitor. Moreover, these drug resistant carcinomas have an aggressive phenotype and show gene enrichment for expression of skin stem cell markers. The goal of the current proposal is to determine whether this molecular profile, indicative of a cancer stem cell, is due to expansion of the functional stem cell compartment, and to elucidate the molecular mechanisms for acquisition of drug resistance. The hypothesis to be tested is that chronic pharmacological suppression of the TGF¿ signaling pathway induces a drug-resistant state resulting in constitutively elevated Smad2/3 signaling that supports expansion of the CSC compartment. In Aim 1 we plan to prove this hypothesis using both in vivo and in vitro approaches in the mouse skin model of chemically-induced carcinogenesis. In Aim 2, we will address the molecular mechanisms responsible for acquired drug resistance and CSC outgrowth by mutation screening of archival tissue using ultra-deep sequencing of the exons of target genes, and by undertaking screens for Smad2 activating kinases in vitro. Understanding the molecular mechanisms of acquired drug resistance to TGF¿ blocking therapies has the potential to improve treatment strategies and next generation drug design. In addition, because of the intimate association between CSCs and TGF¿ signaling, this knowledge has great promise to provide insights into the molecular regulation of CSC maintenance and could provide novel druggable targets for attacking CSCs. PUBLIC HEALTH RELEVANCE: We have recently demonstrated that cancer cells can acquire resistant to a new anti-TGF¿ drug. This resistance appears to support outgrowth of cancer stem cells that are the main villains in maintaining the tumor, allowing tumor spread and causing cancer recurrence after therapy. We intend to find out how the cancer evades this drug at the molecular level, which will provide insight into cancer stem cell biology and provide new targets for attacking cancer stem cells.