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

问题：粘液表皮样癌（MEC）是最常见的恶性唾液腺癌， 成人和儿童。无情的生长和对化疗的抵抗是MEC的标志。果然 没有FDA批准的治疗这种癌症的药物因此，主要的治疗方法仍然是根治性手术， 通常与高发病率、低生活质量和不可接受的低5年生存率（21- 30岁）相关。 II-IV期MEC患者为25%。理由：缺乏细胞系和动物模型是由 NIH/NIDCR是发现唾液腺癌新疗法的主要障碍。第一次融资 循环中，我们产生并表征了第一组经验证的致瘤性人MEC细胞系， 异种移植肿瘤模型（Warner等，2013年）。使用这些模型，我们证明了MEC遵循 癌症干细胞假说和ALDH/CD 44鉴定MEC癌症干细胞（亚当斯等人，2015）。 来自其他肿瘤类型的新证据表明，癌症干细胞对治疗具有抗性， 导致肿瘤复发，这是MEC患者临床管理的关键挑战。为了 为了开发一种方法来克服对治疗的抵抗，我们将工作重点放在制定策略上， 靶向MEC癌症干细胞。我们观察到，Akt-mTOR-S6 K1通路是组成性激活的， MEC癌症干细胞。在初步研究中，我们表明，用替西罗莫司抑制mTOR导致 MEC癌干细胞分数的显著降低和Bmi-1（自我更新标志物）的抑制， vivo.我们还研究了MDM 2，一种参与发病机制的肿瘤细胞存活增强剂。 的MEC。我们进行了令人兴奋的观察，MDM 2-p53相互作用的小分子抑制剂（例如MI-2000）可以抑制MDM 2-p53相互作用。 773)在体外和异种移植肿瘤中消融MEC癌症干细胞。有趣的是，已经表明S6 K1 调节MDM 2蛋白的稳定性，提供mTOR通路和MDM 2之间的机制联系。我们 假设mTOR和/或MDM 2的治疗性抑制消除了癌症干细胞并使其敏感 粘液表皮样癌化疗。为了解决这一假设，我们提出以下具体建议： 目标：S.A.# 1：确定mTOR通路对癌症干细胞存活/自我更新的影响，以及 粘液表皮样癌的复发S.A.编号2：确定治疗性抑制对 MDM 2-p53相互作用对粘液表皮样癌生长和复发的影响S.A.编号3：确定 治疗性抑制mTOR和/或MDM 2对粘液表皮样癌耐药性的影响 常规化疗（顺铂）。意义：这种竞争性的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肿瘤发生。在这里，我们的重点是开发 一种靶向MEC癌症干细胞的基于机制的疗法，用于使用临床相关的 mTOR和/或MDM 2-p53。因此，这项工作的成功结果将为治疗提供支持， 快速进展到旨在提高粘液表皮样癌患者生存率的临床试验。

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.