(PQA2) Interstitial stiffness as a physicochemical modulator of obesity-induced b

描述（由申请人提供）：肥胖是乳腺癌的一个关键风险和预后因素，乳腺癌最常见于绝经后女性的激素受体阳性（HR+）疾病。然而，肥胖导致乳腺癌的分子机制仍然知之甚少，考虑到美国肥胖症的流行，这一点尤其令人震惊。缺氧、细胞外基质（ECM）沉积改变和基质雌激素升高是肥胖微环境的特征，但这些参数的综合影响是否在功能上证实了肥胖依赖性乳腺肿瘤的发生仍不清楚。在肥胖脂肪组织中，缺氧是由扩散限制的氧运输引起的，其诱导氧化应激，其可以通过增加肌成纤维细胞分化来增强纤维化组织重塑。反过来，肌成纤维细胞提高ECM硬度，这不仅扰乱上皮形态发生，而且还可以影响巨噬细胞募集和活化。事实上，与瘦脂肪组织相比，肥胖脂肪组织中的巨噬细胞活化升高，并通过刺激芳香酶表达（一种催化雄激素前体转化为雌激素的酶）来增加乳腺癌风险。然而，肥胖诱导的缺氧是否通过僵硬依赖性巨噬细胞活化促进肿瘤发生，并最终增强雌激素合成，仍是未知数。该项目将研究总体假设，即缺氧通过提高肌成纤维细胞分化增加肥胖脂肪组织中的间质ECM硬度，以及由此产生的ECM理化性质的变化促进恶性肿瘤（i）通过直接影响肿瘤细胞和（ii）通过改变巨噬细胞依赖的基质芳香化酶表达和活性的诱导。为了解决这一假设，将追求三个具体目标。目的1：确定肥胖相关缺氧增强乳腺脂肪组织间质ECM硬度的能力。目标二：表征ECM硬度增加对HR+乳腺肿瘤细胞的影响，并确定巨噬细胞增强基质芳香酶的能力。目标3：评估ECM硬度增加和基质雌激素升高对HR+肿瘤发生的综合影响，并评估治疗性硬度降低是否可以抑制该过程。这些研究将采用多学科方法进行，利用研究团队的工程、生物学和临床专业知识。总的来说，这些发现应该建立肥胖和HR+乳腺癌的僵硬依赖性肿瘤发生之间的功能联系，并激发干扰这些途径的新治疗策略。通过该项目获得的见解也应该为其他非乳腺癌提供广泛的相关性，这些癌症的患病率同样随着肥胖而增加。

DESCRIPTION (provided by applicant): Obesity represents a key risk and prognostic factor for breast cancer, which most commonly presents as hormone receptor positive (HR+) disease in postmenopausal women. However, the molecular mechanisms underlying obesity-driven breast cancer remain poorly understood, which is particularly alarming given the obesity epidemic in the U.S. Hypoxia, altered extracellular matrix (ECM) deposition, and elevated stromal estrogen are characteristic of the obese microenvironment, but whether or not the integrated effects of these parameters functionally corroborate towards obesity-dependent breast tumorigenesis remains unclear. In obese adipose tissue, hypoxia is caused by diffusion-limited oxygen transport, which induces oxidative stress that can enhance fibrotic tissue remodeling via increasing myofibroblast differentiation. Myofibroblasts, in turn, elevate ECM stiffness, which not only perturbs epithelial morphogenesis, but can also impact macrophage recruitment and activation. Indeed, macrophage activation is elevated in obese vs. lean adipose tissue and enhance breast cancer risk by stimulating aromatase expression, an enzyme that catalyzes the conversion of androgen precursors to estrogens. Nevertheless, it remains unknown whether obesity-induced hypoxia promotes tumorigenesis via stiffness-dependent macrophage activation, and ultimately, enhanced estrogen synthesis. This project will investigate the overall hypothesis that hypoxia increases interstitial ECM stiffness in obese adipose tissue by elevating myofibroblast differentiation and that the resulting changes in ECM physicochemical properties promote malignancy (i) via direct effects on tumor cells and (ii) by altering macrophage-dependent induction of stromal aromatase expression and activity. To address this hypothesis, three specific aims will be pursued. Aim 1: Determine the ability of obesity-associated hypoxia to enhance interstitial ECM stiffness of mammary adipose tissue. Aim 2: Characterize the effects of increased ECM stiffness on HR+ mammary tumor cells and determine the ability of macrophages to enhance stromal aromatase. Aim 3: Assess the integrated effects of increased ECM stiffness and elevated stromal estrogen on HR+ tumorigenesis, and evaluate whether therapeutic reduction of stiffness can inhibit this process. These studies will be conducted using a multidisciplinary approach that leverages the engineering, biology, and clinical expertise of the investigative team. Collectively, the findings should establish a functional link between obesity and stiffness-dependent tumorigenesis of HR+ breast cancer, and motivate novel therapeutic strategies that interfere with these pathways. Insights gained by this project should also offer broad relevance to other non-breast cancers whose prevalence is similarly enhanced with obesity.