PDF(Pubmed)
Abstract：
Triple-negative breast cancer (TNBC) is thought to be an estradiol-independent, hormone therapy-resistant cancer because of lack of estrogen receptor alpha 66 (ERα66). We identified a membrane-bound splice variant, ERα36, in TNBC cells that responds to estrogen (E2) and may contribute to bone osteolysis. We demonstrated that the MDA-MB-231 TNBC cell line, which expresses ERα36 similarly to MCF7 cells, is responsive to E2, forming osteolytic tumors in vivo. MDA-MB-231 cells activate osteoclasts in a paracrine manner. Conditioned media (CM) from MDA-MB-231 cells treated with bovine serum albumin-bound E2 (E2-BSA) increased activation of human osteoclast precursor cells; this was blocked by addition of anti-ERα36 antibody to the MDA-MB-231 cultures. Osteoclast activation and bone resorption genes were elevated in RAW 264.7 murine macrophages following treatment with E2-BSA-stimulated MDA-MB-231 CM. E2 and E2-BSA increased phospholipase C (PLC) and protein kinase C (PKC) activity in MDA-MB-231 cells. To examine the role of ERα36 signaling in bone osteolysis in TNBC, we used our bone-cancer interface mouse model in female athymic homozygous Foxn1nu mice. Mice with MDA-MB-231 tumors and treated with tamoxifen (TAM), E2, or TAM/E2 exhibited increased osteolysis, cortical bone breakdown, pathologic fracture, and tumor volume; the combined E2/TAM group also had reduced bone volume. These results suggest that E2 increased osteolytic lesions in TNBC through a membrane-mediated PLC/PKC pathway involving ERα36, which was enhanced by TAM, demonstrating the role of ERα36 and its membrane-associated signaling pathway in bone tumors. This work suggests that ERα36 may be a potential therapeutic target in patients with TNBC.
摘要：
三阴性乳腺癌（TNBC）被认为是一种不依赖雌二醇的乳腺癌，由于缺乏雌激素受体α66（ERα66）而导致激素治疗耐药的癌症。我们鉴定了一种膜结合剪接变体,在对雌激素（E2）有反应的TNBC细胞中，ERα36可能有助于骨溶解。我们证明了MDA-MB-231TNBC细胞系，类似于MCF7细胞表达ERα36，对E2有反应，在体内形成溶骨性肿瘤。MDA-MB-231细胞以旁分泌方式激活破骨细胞。来自用牛血清白蛋白结合的E2(E2-BSA)处理的MDA-MB-231细胞的条件培养基(CM)增加人破骨细胞前体细胞的活化;这通过向MDA-MB-231培养物中添加抗ERα36抗体而被阻断。用E2-BSA刺激的MDA-MB-231CM处理后，RAW264.7鼠巨噬细胞中的破骨细胞激活和骨吸收基因升高。E2和E2-BSA增加MDA-MB-231细胞中的磷脂酶C(PLC)和蛋白激酶C(PKC)活性。探讨ERα36信号在TNBC骨溶解中的作用,我们在雌性无胸腺纯合Foxn1nu小鼠中使用了骨癌界面小鼠模型。患有MDA-MB-231肿瘤并用他莫昔芬（TAM）治疗的小鼠，E2或TAM/E2表现出骨质溶解增加，皮质骨破坏,病理性骨折,和肿瘤体积；E2/TAM组合组的骨体积也减少。这些结果表明，E2通过涉及ERα36的膜介导的PLC/PKC途径增加了TNBC的溶骨性病变，该途径被TAM增强，证明ERα36及其膜相关信号通路在骨肿瘤中的作用。这项工作表明ERα36可能是TNBC患者的潜在治疗靶点。
