Mesenchymal Stromal Cells and Stromal Fibroblasts in Radiotherapy Resistance

描述（由申请人提供）：癌症复发和治疗耐药是当前癌症治疗的主要障碍，其潜在机制尚不清楚。近年来，低氧肿瘤微环境被认为是介导治疗失败的主要原因之一。在复杂的肿瘤微环境成分中，间充质干细胞（MSCs）及其衍生物间充质成纤维细胞目前被认为是癌症进展的每一步的主要调控因子，包括原发性肿瘤生长和继发性转移。此外，越来越多的证据表明，MSCs和间质成纤维细胞也通过药物治疗引起的蛋白质组学或代谢变化在化疗耐药中发挥关键作用。然而，间充质干细胞和间质成纤维细胞是否参与放疗抵抗尚不清楚。我的初步结果显示，与癌细胞相比，间充质干细胞对电离辐射的敏感性要低得多。在乳腺癌和黑色素瘤小鼠模型中，与未处理的MSCs相比，照射后的MSCs在促进原发肿瘤生长和癌细胞肺转移方面发挥了强大的潜力。通过基因表达比较，显示辐照后的MSCs表达高水平的骨桥蛋白（OPN）和CCL-5。OPN的缺乏在很大程度上消除了受照射的间充质干细胞的促癌作用。因此，我们假设MSCs及其衍生的间质成纤维细胞是促进癌症进展的关键辐射应答基质成分，通过过度表达OPN、CCL-5和其他介质。这些间质特征很可能导致放疗后的放射耐药或癌症复发。为了验证这一假设，在本奖项的指导阶段（K99），我将首先验证辐射调节的OPN和CCL-5在MSCs上表达的促肿瘤潜力的功能和分子机制。此外，我将把MSCs的发现扩展到它们的衍生间质成纤维细胞，并开发新的间质标志物（OPN， CCL-5和可能的其他因素）来预测乳腺癌患者的放疗失败。在我的指导阶段的所有这些努力将有助于该奖项的R00阶段的拟议工作-开发有效的治疗方法来治疗动物模型的临床复发/放疗失败。在这个独立的阶段，我将尝试在小鼠身上建立放疗抵抗模型和癌症复发模型，然后测试潜在的化学抑制剂或中和抗体来预防和治疗这些失败。这项研究结合了我之前在间充质干细胞生物学和免疫学方面的培训，以及我目前在乳腺癌转移、治疗耐药和放射肿瘤学方面的培训，这使我在独立阶段进入了一个新的领域，研究MSCs和间质成纤维细胞在治疗耐药中的作用。该结果不仅为我们了解基质放射学基础提供了重要信息，而且有助于开发针对基质OPN、CCL-5和其他可能的介质作为辅助剂的新疗法，以提高放射治疗的疗效。

DESCRIPTION (provided by applicant): Cancer recurrence and treatment resistance represent the primary obstacles to current cancer therapies, with the underlying mechanisms largely unclear. In recent years, the hypoxic tumor microenvironment is regarded as one of the major causes mediating the treatment failures. Among the complicated tumor microenvironmental components, mesenchymal stem/stromal cells (MSCs) and their derivative stromal fibroblasts are currently recognized as master regulators in every step of cancer progression including primary tumor growth and secondary metastasis. Moreover, accumulating evidence suggests that MSCs and stromal fibroblasts also play critical roles in chemoresistance through their proteomic or metabolic changes elicited by drug treatments. However, little is known whether MSCs and stromal fibroblasts are involved in radiotherapy resistance. My preliminary results revealed a much less susceptibility of MSCs to ionizing radiation, compared to cancer cells. In mouse models of breast cancer and melanoma, in contrast to untreated MSCs, the irradiated MSCs exerted a robust potential in promoting primary tumor growth and lung metastasis of cancer cells. Through gene expression comparison, irradiated MSCs were shown to express high levels of osteopontin (OPN) and CCL-5. Deficiency of OPN largely abrogated the cancer promoting effects of irradiated MSCs. We therefore hypothesize that MSCs and their derivative stromal fibroblasts are key radiation-responsive stromal components to facilitate cancer progression, through overexpression of OPN, CCL-5 and other mediators. Those stromal features very likely lead to radioresistance or cancer recurrence after radiotherapy. To test this hypothesis, in the mentored phase (K99) of this award, I will first validate the function and molecular mechanisms of radiation-modulated OPN and CCL-5 expression on MSCs in the tumor promoting potential. Furthermore, I will extend the findings in MSCs to their derivative stromal fibroblasts and develop novel stromal markers (OPN, CCL-5 and possibly other factors) to predict the radiotherapy failure in breast cancer patients. All of these endeavors during my mentored phase will contribute to the proposed work in the R00 phase of this award-to develop effective therapeutics to treat clinical relapse/failure of radiotherapy in animal models. During this independent phase, I will attempt to establish radiotherapy resistance model and cancer relapse model in mice, followed by testing potential chemical inhibitors or neutralizing antibodies to prevent and treat these failures. This study combines my previous training in mesenchymal stem cell biology and immunology, and my current training in breast cancer metastasis, treatment resistance and radiation oncology, which brings me to a new field investigating the roles of MSCs and stromal fibroblasts in treatment resistance at my independent stage. The results will not only provide important information for our understanding of the basic stroma radiology, but also help to develop novel therapeutics to target stromal OPN, CCL-5 and possibly other mediators as adjutants to improve the efficacy of radiotherapy.