Determine the molecular and metabolic mechanisms by which A-FABP links dysregulated lipid metabolism-induced obesity/breast cancer risk

本提案的目的是确定高脂饮食（HFD）诱导的脂质失调与肥胖的联系 乳腺癌（BC）风险增加。流行病学研究证实，肥胖会增加 和死亡率，但肥胖/乳腺癌关联的分子机制仍然主要是 未知我们最近的研究表明，脂质伴侣A-FABP（脂肪脂肪酸结合蛋白，也 称为FABP 4）通过调节肿瘤细胞内的促肿瘤活性来促进肥胖相关的BC 相关巨噬细胞（TAM）和细胞外增强BC细胞的侵袭性表型。因此，A- FABP可能是一个新的因素，将脂质代谢失调与肥胖/BC风险联系起来。而且我们 观察到肥胖可以通过消耗不同类型的HFD来诱导，包括饱和脂肪（例如， 可可脂）或不饱和脂肪（例如橄榄油、鱼油）。然而，只有可可脂HFD引起的肥胖才是 与A-FABP表达增加和乳腺肿瘤生长相关。这些观察表明， 新概念，即并非所有HFD诱导的肥胖都是致瘤性的。考虑到肥胖背后的不确定联系- 诱导BC风险，我们假设富含饱和脂肪的HFD通过A-FABP介导 免疫和代谢调节。因此，A-FABP提供了一种新的治疗靶点和生物标志物， 与肥胖相关的BC风险。三个互补但独立的具体目标旨在解决我们的问题 中心假设目的1是确定不同HFD上调A- 用于BC风险的FABP。我们将确定哪些HFD会增加乳腺肿瘤的风险，并进一步分析HFD如何“坏”。 脂肪驱动TAM中的细胞内A-FABP表达，并促进细胞外A-FABP分泌， 脂肪细胞目的二是阐明HFD上调A-FABP在BC中的下游代谢机制 风险和免疫治疗。我们将描述TAMs细胞内A-FABP如何调节FA氧化 (FAO)/HIF 2 α/PD-L1通路的免疫抑制功能，然后描绘细胞外A- FABP重编程BC细胞中的脂质代谢谱以增强其侵袭性表型。我们将进一步 评估用我们独特的人源化抗体阻断A-FABP活性是否改善A-FABP诱导的 代谢失调和降低肥胖/BC风险。目的3是评估A-FABP作为肥胖的生物标志物- 人类的BC。我们将确定外周血单核细胞中A-FABP的功能，并测量A-FABP在外周血单核细胞中的表达。 血清中可溶性A-FABP水平和肿瘤间质中A-FABP表达， 有或没有BC的瘦和肥胖妇女。成功完成这一建议将确定“坏 HFDs”在促进BC风险中的作用，并确定A-FABP介导的分子和代谢机制 HFD诱导的肥胖/BC风险中的促肿瘤活性。

The objective of this proposal is to determine how high fat diet (HFD)-induced lipid dysregulation links obesity with increased breast cancer (BC) risk. Epidemiologic studies have confirmed that obesity increases the risk and mortality of BC, but the molecular mechanisms of obesity/breast cancer associations remain largely unknown. Our recent studies demonstrate that lipid chaperone A-FABP (adipose fatty acid binding protein, also known as FABP4) promotes obesity-associated BC by intracellular regulating pro-tumor activity in tumor associated macrophages (TAMs) and extracellular enhancing aggressive phenotype of BC cells. Thus, A- FABP might represent a new factor linking dysregulated lipid metabolism with obesity/BC risk. Moreover, we observed that obesity can be induced by consumption of different types of HFDs, including saturated fats (e.g. cocoa butter) or unsaturated fats (e.g. olive oil, fish oil). However, only cocoa butter HFD-induced obesity was associated with increased A-FABP expression and mammary tumor growth. These observations suggest a novel concept that not all HFD-induced obesity is tumorigenic. Given the undefined links underlying obesity- induced BC risk, we hypothesized that HFDs rich in saturated fats promote BC risk through A-FABP-mediated immune and metabolic regulations. As such, A-FABP offers a novel therapeutic target and biomarker for obesity-associated BC risk. Three complementary but independent specific aims are designed to address our central hypothesis. Aim 1 is to determine the molecular mechanisms by which different HFDs upregulate A- FABP for BC risk. We will identify which HFDs promote mammary tumor risk and further dissect how the “bad” fat drives intracellular A-FABP expression in TAMs and promotes extracellular A-FABP secretion from adipocytes. Aim 2 is to delineate the downstream metabolic mechanisms of HFD-upregulated A-FABP in BC risk and immunotherapy. We will delineate how intracellular A-FABP in TAMs regulates the FA oxidation (FAO)/HIF2α/PD-L1 pathway for immune suppressive function, followed by delineation of how extracellular A- FABP reprograms lipid metabolic profile in BC cells to enhance their aggressive phenotype. We will further evaluate if blocking A-FABP activity with our unique humanized antibodies improves A-FABP-induced metabolic dysregulation and reduces obesity/BC risk. Aim 3 is to evaluate A-FABP as a biomarker for obesity- associated BC in humans. We will determine the function of A-FABP in peripheral monocytes and measure the levels of soluble A-FABP in serum and A-FABP expression in tumor stroma using specimens collected from lean and obese women with or without BC. Successful completion of this proposal will determine the “bad HFDs” in promoting BC risk and identify the molecular and metabolic mechanisms by which A-FABP mediates the pro-tumorigenic activities in HFD-induced obesity/BC risk.