Departments of Biochemistry, Molecular Biology and Biophysics, The University of Minnesota-Twin Cities, Minneapolis, Minnesota.
Department of Surgery, The University of Minnesota-Twin Cities, Minneapolis, Minnesota.
Mol Cancer Res. 2023 Aug 1;21(8):836-848. doi: 10.1158/1541-7786.MCR-22-0763.
Fatty acid binding protein 4 (FABP4) is a secreted adipokine linked to obesity and progression of a variety of cancers. Obesity increases extracellular FABP4 (eFABP4) levels in animal models and in obese breast cancer patients compared with lean healthy controls. Using MCF-7 and T47D breast cancer epithelial cells, we show herein that eFABP4 stimulates cellular proliferation in a time and concentration dependent manner while the non-fatty acid-binding mutant, R126Q, failed to potentiate growth. When E0771 murine breast cancer cells were injected into mice, FABP4 null animals exhibited delayed tumor growth and enhanced survival compared with injections into control C57Bl/6J animals. eFABP4 treatment of MCF-7 cells resulted in a significant increase in phosphorylation of extracellular signal-regulated kinase 1/2 (pERK), transcriptional activation of nuclear factor E2-related factor 2 (NRF2) and corresponding gene targets ALDH1A1, CYP1A1, HMOX1, SOD1 and decreased oxidative stress, while R126Q treatment did not show any effects. Proximity-labeling employing an APEX2-FABP4 fusion protein revealed several proteins functioning in desmosomes as eFABP4 receptor candidates including desmoglein (DSG), desmocollin, junction plankoglobin, desomoplankin, and cytokeratins. AlphaFold modeling predicted an interaction between eFABP4, and the extracellular cadherin repeats of DSG2 and pull-down and immunoprecipitation assays confirmed complex formation that was potentiated by oleic acid. Silencing of DSG2 in MCF-7 cells attenuated eFABP4 effects on cellular proliferation, pERK levels, and ALDH1A1 expression compared with controls.
These results suggest desmosomal proteins, and in particular desmoglein 2, may function as receptors of eFABP4 and provide new insight into the development and progression of obesity-associated cancers.
脂肪酸结合蛋白 4（FABP4）是一种分泌性脂肪因子，与肥胖和多种癌症的进展有关。肥胖症会增加动物模型和肥胖乳腺癌患者的细胞外 FABP4（eFABP4）水平，与健康的瘦对照相比。本文使用 MCF-7 和 T47D 乳腺癌上皮细胞表明，eFABP4 以时间和浓度依赖的方式刺激细胞增殖，而非脂肪酸结合突变体 R126Q 未能增强生长。当 E0771 小鼠乳腺癌细胞注射到小鼠体内时，与注射到对照 C57Bl/6J 动物相比，FABP4 缺失动物表现出肿瘤生长延迟和存活率提高。eFABP4 处理 MCF-7 细胞导致细胞外信号调节激酶 1/2（pERK）的磷酸化显著增加，核因子 E2 相关因子 2（NRF2）的转录激活和相应的基因靶标 ALDH1A1、CYP1A1、HMOX1、SOD1 和氧化应激减少，而 R126Q 处理没有显示出任何效果。使用 APEX2-FABP4 融合蛋白进行的接近标记揭示了几种在桥粒中起作用的蛋白质，作为 eFABP4 受体候选物，包括桥粒蛋白（DSG）、桥粒蛋白聚糖、连接斑蛋白、桥粒斑蛋白和细胞角蛋白。AlphaFold 建模预测了 eFABP4 与 DSG2 的细胞外钙粘蛋白重复之间的相互作用，下拉和免疫沉淀测定证实了这种复合物的形成，油酸使其增强。与对照相比，沉默 MCF-7 细胞中的 DSG2 可减弱 eFABP4 对细胞增殖、pERK 水平和 ALDH1A1 表达的影响。
这些结果表明桥粒蛋白，特别是桥粒蛋白 2，可能作为 eFABP4 的受体发挥作用，并为肥胖相关癌症的发生和发展提供了新的见解。
