Department of Biochemistry & Molecular Genetics, University of Louisville School of Medicine Louisville, Kentucky, USA.
Pathology and Laboratory Medicine, University of Louisville, Louisville, Kentucky, USA.
Endocr Relat Cancer. 2023 Sep 27;30(11). doi: 10.1530/ERC-23-0148. Print 2023 Nov 1.
Despite the successful combination of therapies improving survival of estrogen receptor α (ER+) breast cancer patients with metastatic disease, mechanisms for acquired endocrine resistance remain to be fully elucidated. The RNA binding protein HNRNPA2B1 (A2B1), a reader of N(6)-methyladenosine (m6A) in transcribed RNA, is upregulated in endocrine-resistant, ER+ LCC9 and LY2 cells compared to parental MCF-7 endocrine-sensitive luminal A breast cancer cells. The miRNA-seq transcriptome of MCF-7 cells overexpressing A2B1 identified the serine metabolic processes pathway. Increased expression of two key enzymes in the serine synthesis pathway (SSP), phosphoserine aminotransferase 1 (PSAT1) and phosphoglycerate dehydrogenase (PHGDH), correlates with poor outcomes in ER+ breast patients who received tamoxifen (TAM). We reported that PSAT1 and PHGDH were higher in LCC9 and LY2 cells compared to MCF-7 cells and their knockdown enhanced TAM sensitivity in these-resistant cells. Here we demonstrate that stable, modest overexpression of A2B1 in MCF-7 cells increased PSAT1 and PHGDH and endocrine resistance. We identified four miRNAs downregulated in MCF-7-A2B1 cells that directly target the PSAT1 3'UTR (miR-145-5p and miR-424-5p), and the PHGDH 3'UTR (miR-34b-5p and miR-876-5p) in dual luciferase assays. Lower expression of miR-145-5p and miR-424-5p in LCC9 and ZR-75-1-4-OHT cells correlated with increased PSAT1 and lower expression of miR-34b-5p and miR-876-5p in LCC9 and ZR-75-1-4-OHT cells correlated with increased PHGDH. Transient transfection of these miRNAs restored endocrine-therapy sensitivity in LCC9 and ZR-75-1-4-OHT cells. Overall, our data suggest a role for decreased A2B1-regulated miRNAs in endocrine resistance and upregulation of the SSP to promote tumor progression in ER+ breast cancer.
尽管成功结合了多种疗法，改善了转移性雌激素受体 α (ER+)乳腺癌患者的生存，但获得性内分泌抵抗的机制仍有待充分阐明。RNA 结合蛋白 HNRNPA2B1（A2B1）是转录 RNA 中 N(6)-甲基腺苷 (m6A) 的阅读器，与亲本 MCF-7 内分泌敏感腔 A 乳腺癌细胞相比，在内分泌耐药的 ER+LCC9 和 LY2 细胞中上调。MCF-7 细胞中 A2B1 过表达的 miRNA-seq 转录组鉴定出丝氨酸代谢途径。在接受他莫昔芬 (TAM) 治疗的 ER+乳腺癌患者中，两个丝氨酸合成途径 (SSP) 关键酶的表达增加（磷酸丝氨酸转氨酶 1 (PSAT1) 和磷酸甘油酸脱氢酶 (PHGDH)）与不良预后相关。我们报道称，与 MCF-7 细胞相比，LCC9 和 LY2 细胞中 PSAT1 和 PHGDH 更高，并且它们的敲低增强了这些耐药细胞中 TAM 的敏感性。在这里，我们证明了 MCF-7 细胞中 A2B1 的稳定适度过表达增加了 PSAT1 和 PHGDH 并导致内分泌抵抗。我们鉴定了在 MCF-7-A2B1 细胞中下调的四个直接靶向 PSAT1 3'UTR（miR-145-5p 和 miR-424-5p）和 PHGDH 3'UTR（miR-34b-5p 和 miR-876-5p）的 miRNA，在双荧光素酶测定中。LCC9 和 ZR-75-1-4-OHT 细胞中 miR-145-5p 和 miR-424-5p 的表达降低与 PSAT1 增加相关，而 LCC9 和 ZR-75-1-4-OHT 细胞中 miR-34b-5p 和 miR-876-5p 的表达降低与 PHGDH 增加相关。这些 miRNA 的瞬时转染恢复了 LCC9 和 ZR-75-1-4-OHT 细胞对内分泌治疗的敏感性。总的来说，我们的数据表明，A2B1 调节的 miRNA 减少在 ER+乳腺癌的内分泌抵抗中起作用，并且 SSP 的上调促进了肿瘤的进展。
