Table_2_FDXR drives primary and endocrine-resistant tumor cell growth in ER+ breast cancer via CPT1A-mediated fatty acid oxidation.xlsx

BackgroundThe majority of breast cancers (BCs) expressing estrogen receptor (ER) have shown endocrine resistance. Our previous study demonstrated that ferredoxin reductase (FDXR) promoted mitochondrial function and ER+ breast tumorigenesis. But the underlying mechanism is not clear.
MethodsLiquid chromatography (LC) tandem mass spectrometry (MS/MS)-based metabolite profiling was utilized to reveal the metabolites regulated by FDXR. RNA microarray was utilized to determine the potential downstream targets of FDXR. Seahorse XF24 analyzer was performed to analyze the FAO-mediated oxygen consumption rate (OCR). Q-PCR and western blotting assays were used to measure expression levels of FDXR and CPT1A. MTS, 2D colony formation and anchorage-independent growth assays were used to evaluate the effects of FDXR or drug treatments on tumor cell growth of primary or endocrine-resistant breast cancer cells.
ResultsWe found that depletion of FDXR inhibited fatty acid oxidation (FAO) by suppressing CPT1A expression. Endocrine treatment increased the expression levels of both FDXR and CPT1A. Further, we showed that depletion of FDXR or FAO inhibitor etomoxir treatment reduced primary and endocrine-resistant breast cancer cell growth. Therapeutically, combining endocrine therapy with FAO inhibitor etomoxir synergistically inhibits primary and endocrine-resistant breast cancer cell growth.
DiscussionWe reveal that the FDXR-CPT1A-FAO signaling axis is essential for primary and endocrine-resistant breast cancer cell growth, thus providing a potential combinatory therapy against endocrine resistance in ER+ breast cancer.

背景：大多数表达雌激素受体（estrogen receptor, ER）的乳腺癌（breast cancers, BCs）已出现内分泌治疗抵抗。我们既往的研究显示，铁氧还蛋白还原酶（ferredoxin reductase, FDXR）可促进线粒体功能与ER阳性乳腺肿瘤发生，但具体分子机制尚不明确。
方法：本研究采用基于液相色谱（liquid chromatography, LC）串联质谱（tandem mass spectrometry, MS/MS）的代谢组学分析，以揭示FDXR调控的代谢物谱；通过RNA芯片（RNA microarray）技术筛选FDXR的潜在下游靶标；使用Seahorse XF24分析仪检测脂肪酸氧化（fatty acid oxidation, FAO）介导的氧消耗速率（oxygen consumption rate, OCR）；采用实时荧光定量PCR（Q-PCR）与蛋白质免疫印迹（western blotting）实验检测FDXR与肉碱棕榈酰转移酶1A（CPT1A）的表达水平；通过MTS实验、二维集落形成实验及非锚定依赖性生长实验，评估FDXR干预或药物处理对原代或内分泌抵抗型乳腺癌细胞增殖的影响。
结果：本研究发现，FDXR敲低可通过抑制CPT1A的表达阻断脂肪酸氧化过程；内分泌治疗可同时上调FDXR与CPT1A的表达水平。进一步实验显示，FDXR敲低或脂肪酸氧化抑制剂依托莫司（etomoxir）处理均可抑制原代及内分泌抵抗型乳腺癌细胞的增殖。在治疗层面，内分泌治疗联合FAO抑制剂依托莫司可协同抑制原代及内分泌抵抗型乳腺癌细胞的增殖。
讨论：本研究揭示FDXR-CPT1A-FAO信号轴对原代及内分泌抵抗型乳腺癌细胞的增殖至关重要，从而为ER阳性乳腺癌的内分泌抵抗治疗提供了潜在的联合疗法策略。