Department of Human Genetics, Hannover Medical School, Carl-Neuberg-Str. 1, 30629 Hannover, Germany.
Center for Chromosome Stability, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
Int J Mol Sci. 2022 May 4;23(9):5131. doi: 10.3390/ijms23095131.
Chromosomal instability (CIN) can be a driver of tumorigenesis but is also a promising therapeutic target for cancer associated with poor prognosis such as triple negative breast cancer (TNBC). The treatment of TNBC cells with defects in DNA repair genes with poly(ADP-ribose) polymerase inhibitor (PARPi) massively increases CIN, resulting in apoptosis. Here, we identified a previously unknown role of microRNA-449a in CIN. The transfection of TNBC cell lines HCC38, HCC1937 and HCC1395 with microRNA-449a mimics led to induced apoptosis, reduced cell proliferation, and reduced expression of genes in homology directed repair (HDR) in microarray analyses. was identified as a new target gene by immunoprecipitation and luciferase assays. The reduced expression of led to an increased frequency of ultrafine bridges, 53BP1 foci, and micronuclei. The induced expression of microRNA-449a elevated CIN beyond tolerable levels and induced apoptosis in TNBC cell lines by two different mechanisms: (I) promoting chromatid mis-segregation by targeting endonuclease and (II) inhibiting HDR by downregulating key players of the HDR network such as , , and . The ectopic expression of microRNA-449a enhanced the toxic effect of PARPi in cells with pathogenic germline variants. The newly identified role makes microRNA-449a an interesting therapeutic target for TNBC.
染色体不稳定性 (CIN) 可以是肿瘤发生的驱动因素，但也是预后不良的癌症（如三阴性乳腺癌 (TNBC)）有希望的治疗靶点。用聚 (ADP-核糖) 聚合酶抑制剂 (PARPi) 治疗 DNA 修复基因缺陷的 TNBC 细胞会大大增加 CIN，导致细胞凋亡。在这里，我们确定了 microRNA-449a 在 CIN 中的一个先前未知的作用。用 microRNA-449a 模拟物转染 TNBC 细胞系 HCC38、HCC1937 和 HCC1395 导致细胞凋亡、细胞增殖减少和同源定向修复 (HDR) 基因在微阵列分析中的表达减少。通过免疫沉淀和荧光素酶测定鉴定为新的靶基因。 的表达减少导致超细线、53BP1 焦点和微核的出现频率增加。microRNA-449a 的诱导表达将 CIN 提高到不可容忍的水平，并通过两种不同的机制在 TNBC 细胞系中诱导细胞凋亡：(I) 通过靶向内切酶 促进染色单体错误分离，以及 (II) 通过下调 HDR 网络的关键成员，如 、 、 和 ，抑制 HDR。microRNA-449a 的异位表达增强了 PARPi 在具有致病性种系 变体的细胞中的毒性作用。新确定的作用使 microRNA-449a 成为 TNBC 的一个有趣的治疗靶点。
