Perivascular niche for salivary gland cancer stem cells and resistance to therapy

问题：粘液表皮样癌(MEC)是我国最常见的恶性涎腺癌 成人和儿童都有。无情的生长和对化疗的抗药性是MEC的特征。事实上，在那里 不是FDA批准的治疗这种癌症的药物。因此，主要的治疗仍然是根治性手术，这是 通常与高发病率，较差的生活质量和令人无法接受的低5年存活率21- II-IV期MEC患者为25%。基本原理：缺乏细胞系和动物模型是由 NIH/NIDCR是发现涎腺癌新疗法的主要障碍。在第一笔资金中 周期中，我们建立并鉴定了第一组有效的致瘤人类MEC细胞系和 异种移植肿瘤模型(Warner等人，2013年)。使用这些模型，我们演示了MEC遵循 癌症干细胞假说以及ALDH/CD44识别MEC癌症干细胞(Adams等人，2015年)。 来自其他肿瘤类型的新证据表明，癌症干细胞对治疗和 促使肿瘤复发，这是MEC患者临床管理中的关键挑战。在一次努力中 为了开发一种克服治疗耐药性的方法，我们将工作重点放在开发策略上。 以MEC癌症干细胞为靶点。我们观察到Akt-mTOR-S6K1通路在 MEC癌症干细胞。在初步研究中，我们表明，用坦西罗莫司抑制mTOR会导致 MEC肿瘤干细胞比例显著下降和BMI-1(自我更新标志)的抑制 活着。我们还研究了MDM2，它是一种肿瘤细胞存活的增强剂，与发病机制有关。 MEC的。我们做了令人兴奋的观察到，MDM2-P53相互作用的小分子抑制剂(例如，MI- 773)在体外和异种移植瘤中去除MEC癌细胞干细胞。有趣的是，S6K1已经被证明是 调节MDM2蛋白的稳定性，在mTOR通路和MDM2之间提供了一种机械联系。我们的 假说是，mTOR和/或MDM2的治疗抑制可以消除癌症干细胞并使其增敏 粘液表皮样癌转为化疗。为了解决这一假设，我们提出了以下具体建议 目标：S.A.#1：确定mTOR通路对肿瘤干细胞存活/自我更新的影响，以及 粘液表皮样癌复发的探讨。S.A.#2：确定治疗抑制的效果 MDM2-P53相互作用在粘液表皮样癌生长和复发中的作用S.A.#3：确定 治疗抑制mTOR和/或MDM2对黏液表皮样癌耐药的影响 常规化疗(顺铂)。意义：这一竞争性更新建立在一个关键发现的基础上 在第一个资助周期，即癌症干细胞驱动MEC肿瘤的形成。在这里，我们的重点是开发 以MEC肿瘤干细胞为靶点的机制治疗与临床相关的抑制物 MTOR和/或mdm2-p53。因此，这项工作的成功结果将为一种能够 迅速推进旨在提高粘液表皮样癌患者存活率的临床试验。

The Problem: Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland cancer in adults and in children. Relentless growth and resistance to chemotherapy are hallmarks of MEC. Indeed, there is no FDA-approved drug for this cancer. Therefore, the primary treatment still is radical surgery, which is typically associated with high morbidity, poor quality of life, and an unacceptably low 5-year survival rate of 21- 25% for patients with stage II-IV MEC. Rationale: Lack of cell lines and animal models was identified by the NIH/NIDCR as a major roadblock to the discovery of new therapies for salivary gland cancer. In the 1st funding cycle, we generated and characterized the first panel of validated tumorigenic human MEC cell lines and xenograft tumor models (Warner et al., 2013). Using these models, we demonstrated that MEC follows the cancer stem cell hypothesis and that ALDH/CD44 identifies MEC cancer stem cells (Adams et al, 2015). Emerging evidence from other tumor types demonstrates that cancer stem cells are resistant to therapy and drive tumor recurrence, which are key challenges in the clinical management of patients with MEC. In an effort to develop an approach to overcome resistance to therapy, we focused our work on developing strategies targeting MEC cancer stem cells. We observed that the Akt-mTOR-S6K1 pathway is constitutively active in MEC cancer stem cells. In pilot studies, we showed that inhibition of mTOR with Temsirolimus results in significant decrease in the fraction of MEC cancer stem cells and inhibition of Bmi-1 (marker of self-renewal) in vivo. We have also investigated MDM2, an enhancer of tumor cell survival that is involved in the pathogenesis of MEC. We made the exciting observation that small molecule inhibitors of the MDM2-p53 interaction (e.g. MI- 773) ablate MEC cancer stem cells in vitro and in xenograft tumors. Interestingly, it has been shown that S6K1 regulates MDM2 protein stability, providing a mechanistic link between the mTOR pathway and MDM2. Our hypothesis is that therapeutic inhibition of mTOR and/or MDM2 ablates cancer stem cells and sensitizes mucoepidermoid carcinomas to chemotherapy. To address this hypothesis, we propose the following specific aims: S.A.#1: To define the effect of the mTOR pathway on the survival/self-renewal of cancer stem cells, and on the recurrence of mucoepidermoid carcinomas. S.A.#2: To define the effect of therapeutic inhibition of the MDM2-p53 interaction on the growth and recurrence of mucoepidermoid carcinomas. S.A.#3: To determine the effect of therapeutic inhibition of mTOR and/or MDM2 on the resistance of mucoepidermoid carcinomas to conventional chemotherapy (Cisplatin). Significance: This competing renewal builds upon a key discovery made in the 1st funding cycle, i.e. cancer stem cells drive MEC tumorigenesis. Here, our focus is on developing a mechanism-based therapy targeting MEC cancer stem cells for ablation with clinically relevant inhibitors of mTOR and/or MDM2-p53. As such, successful outcome of this work will provide support for a therapy that can quickly progress towards a clinical trial aiming at improving the survival of mucoepidermoid carcinoma patients.