He Zhengcheng, Kannan Nagarajan, Nemirovsky Oksana, Chen Helen, Connell Marisa, Taylor Brian, Jiang Jihong, Pilarski Linda M, Fleisch Markus C, Niederacher Dieter, Pujana Miguel Angel, Eaves Connie J, Maxwell Christopher A
Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.
Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.
Oncotarget. 2017 May 16;8(20):32461-32475. doi: 10.18632/oncotarget.15688.
BRCA1 deficiency may perturb the differentiation hierarchy present in the normal mammary gland and is associated with the genesis of breast cancers that are genomically unstable and typically display a basal-like transcriptome. Oriented cell division is a mechanism known to regulate cell fates and to restrict tumor formation. We now show that the cell division axis is altered following shRNA-mediated BRCA1 depletion in immortalized but non-tumorigenic, or freshly isolated normal human mammary cells with graded consequences in progeny cells that include aneuploidy, perturbation of cell polarity in spheroid cultures, and a selective loss of cells with luminal features. BRCA1 depletion stabilizes HMMR abundance and disrupts cortical asymmetry of NUMA-dynein complexes in dividing cells such that polarity cues provided by cell-matrix adhesions were not able to orient division. We also show that immortalized mammary cells carrying a mutant BRCA1 allele (BRCA1 185delAG/+) reproduce many of these effects but in this model, oriented divisions were maintained through cues provided by CDH1+ cell-cell junctions. These findings reveal a previously unknown effect of BRCA1 suppression on mechanisms that regulate the cell division axis in proliferating, non-transformed human mammary epithelial cells and consequent downstream effects on the mitotic integrity and phenotype control of their progeny.
BRCA1缺陷可能扰乱正常乳腺中存在的分化层次结构，并与基因组不稳定且通常表现出基底样转录组的乳腺癌的发生有关。定向细胞分裂是一种已知可调节细胞命运并限制肿瘤形成的机制。我们现在表明，在永生化但无致瘤性的细胞中，或在新鲜分离的正常人乳腺细胞中，经shRNA介导的BRCA1缺失后，细胞分裂轴会发生改变，这对后代细胞会产生不同程度的影响，包括非整倍体、球体培养中细胞极性的扰动以及具有腔特征的细胞的选择性丢失。BRCA1缺失会使HMMR丰度稳定，并破坏分裂细胞中NUMA-动力蛋白复合物的皮质不对称性，从而使细胞-基质粘附提供的极性线索无法引导分裂。我们还表明，携带突变BRCA1等位基因（BRCA1 185delAG/+）的永生化乳腺细胞会重现其中许多效应，但在该模型中，定向分裂是通过CDH1+细胞-细胞连接提供的线索得以维持的。这些发现揭示了BRCA1抑制对增殖的、未转化的人乳腺上皮细胞中调节细胞分裂轴的机制以及对其后代的有丝分裂完整性和表型控制的下游影响的一种前所未知的作用。
