Mesenchymal Stromal Cells and Stromal Fibroblasts in Radiotherapy Resistance

描述(申请人提供)：癌症复发和治疗耐药性是当前癌症治疗的主要障碍，其潜在机制很大程度上尚不清楚。近年来，肿瘤缺氧微环境被认为是导致治疗失败的主要原因之一。在复杂的肿瘤微环境成分中，间充质干细胞及其衍生的间质成纤维细胞目前被认为是肿瘤发展过程中包括原发肿瘤生长和继发转移在内的每一步的主要调节细胞。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或代谢变化在化疗耐药中发挥关键作用。然而，骨髓间充质干细胞和间质成纤维细胞是否参与放射治疗耐药尚不清楚。我的初步结果显示，与癌细胞相比，MSCs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，与未经治疗的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。基因表达比较显示，照射后的MSCs表达高水平的骨桥蛋白(OPN)和CCL-5。骨桥蛋白的缺失在很大程度上削弱了照射后MSCs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辐射反应的主要间质成分，通过OPN、CCL-5和其他介质的过度表达促进癌症的进展。这些间质特征很可能导致放射抵抗或放射治疗后癌症复发。为了验证这一假设，在该奖项的指导阶段(K99)，我将首先验证辐射调节的OPN和CCL-5在MSCs上表达在促进肿瘤潜力中的功能和分子机制。此外，我将把在MSCs中的发现扩展到其衍生的间质成纤维细胞，并开发新的间质标记物(OPN、CCL-5和可能的其他因子)来预测乳腺癌患者的放射治疗失败。在我的指导阶段，所有这些努力都将有助于该奖项R00阶段的拟议工作-开发有效的疗法来治疗动物模型中的临床复发/放射治疗失败。在这个独立的阶段，我将尝试建立小鼠的放射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。这项研究结合了我以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，这将我带入一个新的领域，在我的独立阶段研究间充质干细胞和间质成纤维细胞在治疗耐药中的作用。这一结果不仅为我们了解间质的基础放射学提供了重要的信息，而且有助于开发以间质OPN、CCL-5和其他可能的介质为辅助的新的治疗方法，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.