Muluhngwi Penn, Krishna Abirami, Vittitow Stephany L, Napier Joshua T, Richardson Kirsten M, Ellis Mackenzie, Mott Justin L, Klinge Carolyn M
Department of Biochemistry & Molecular Genetics, Center for Genetics and Molecular Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Department of Biochemistry & Molecular Genetics, Center for Genetics and Molecular Medicine, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Cancer Lett. 2017 Mar 1;388:230-238. doi: 10.1016/j.canlet.2016.12.007. Epub 2016 Dec 13.
Endocrine-resistance develops in ∼40% of breast cancer patients after tamoxifen (TAM) therapy. Although microRNAs are dysregulated in breast cancer, their contribution to endocrine-resistance is not yet understood. Previous microarray analysis identified miR-29a and miR-29b-1 as repressed by TAM in MCF-7 endocrine-sensitive breast cancer cells but stimulated by TAM in LY2 endocrine-resistant breast cancer cells. Here we examined the mechanism for the differential regulation of these miRs by TAM in MCF-7 versus TAM-resistant LY2 and LCC9 breast cancer cells and the functional role of these microRNAs in these cells. Knockdown studies revealed that ERα is responsible for TAM regulation of miR-29b-1/a transcription. We also demonstrated that transient overexpression of miR-29b-1/a decreased MCF-7, LCC9, and LY2 proliferation and inhibited LY2 cell migration and colony formation but did not sensitize LCC9 or LY2 cells to TAM. Furthermore, TAM reduced DICER1 mRNA and protein in LY2 cells, a known target of miR-29. Supporting this observation, anti-miR-29b-1 or anti-miR-29a inhibited the suppression of DICER by 4-OHT. These results suggest miR-29b-1/a has tumor suppressor activity in TAM-resistant cells and does not appear to play a role in mediating TAM resistance.
约40%的乳腺癌患者在接受他莫昔芬（TAM）治疗后会出现内分泌抵抗。尽管微小RNA在乳腺癌中表达失调，但其对内分泌抵抗的作用尚不清楚。先前的微阵列分析表明，miR-29a和miR-29b-1在MCF-7内分泌敏感型乳腺癌细胞中被TAM抑制，但在LY2内分泌抵抗型乳腺癌细胞中被TAM刺激。在此，我们研究了TAM在MCF-7细胞与TAM耐药的LY2和LCC9乳腺癌细胞中对这些微小RNA差异调节的机制，以及这些微小RNA在这些细胞中的功能作用。敲低研究表明，ERα负责TAM对miR-29b-1/a转录的调控。我们还证明，miR-29b-1/a的瞬时过表达降低了MCF-7、LCC9和LY2细胞的增殖，并抑制了LY2细胞的迁移和集落形成，但并未使LCC9或LY2细胞对TAM敏感。此外，TAM降低了LY2细胞中DICER1的mRNA和蛋白水平，DICER1是miR-29的已知靶点。支持这一观察结果的是，抗miR-29b-1或抗miR-29a抑制了4-羟基他莫昔芬（4-OHT）对DICER的抑制作用。这些结果表明，miR-29b-1/a在TAM耐药细胞中具有肿瘤抑制活性，且似乎在介导TAM耐药中不起作用。
