Department of Biochemistry, Microbiology and Biotechnology, University of Limpopo, Private Bag X1106, Sovenga 0727, Polokwane, South Africa.
Genes (Basel). 2019 Jan 14;10(1):41. doi: 10.3390/genes10010041.
Several pathways are deregulated during carcinogenesis but most notably, tumour cells can lose cell cycle control and acquire resistance to apoptosis by expressing a number of anti-apoptotic proteins such as the Inhibitors of Apoptosis Protein (IAP) family of proteins that include survivin, which is implicated in cancer development. There is no study which had proven that arsenic trioxide (As₂O₃) has any effect on the splicing machinery of survivin and its splice variants, hence this study was aimed at determining the cytotoxic effect of As₂O₃ and its effect on the expression pattern of survivin splice variants in MCF-7 cells. As₂O₃ inhibited the growth of the MCF-7 cells in a concentration-dependent manner. The Muse Cell Analyser showed that As₂O₃-induced G2/M cell cycle arrest, promoted caspase-dependent apoptosis without causing any damage to the mitochondrial membrane of MCF-7 cells. As₂O₃ also deactivated two survival pathways, Mitogen-Activated Protein Kinase (MAPK) and Phosphoinositide 3-Kinase (PI3K) signalling pathways in MCF-7 cells. Deactivation of the two pathways was accompanied by the upregulation of survivin 3α during As₂O₃-induced G2/M cell cycle arrest and apoptosis. Survivin 2B was found to be upregulated only during As₂O₃-induced G2/M cell cycle arrest but downregulated during As₂O₃-induced apoptosis. Survivin wild-type was highly expressed in the untreated MCF-7 cells, the expression was upregulated during As₂O₃-induced G2/M cell cycle arrest and it was downregulated during As₂O₃-induced apoptosis. Survivin variant ΔEx3 was undetected in both untreated and treated MCF-7 cells. Survivin proteins were localised in both the nucleus and cytoplasm in MCF-7 cells and highly upregulated during the As₂O₃-induced G2/M cell cycle arrest, which can be attributed to the upregulation of survivin-2B. This study has provided the first evidence showing that the novel survivin 2B splice variant may be involved in the regulation of As₂O₃-induced G2/M cell cycle arrest only. This splice variant can therefore, be targeted for therapeutic purposes against Luminal A breast cancer cells.
在癌变过程中，有几个途径会失调，但最值得注意的是，肿瘤细胞可以通过表达许多抗凋亡蛋白（如凋亡蛋白抑制剂（IAP）家族蛋白）来失去细胞周期控制并获得对细胞凋亡的抗性，其中包括 Survivin，它与癌症的发展有关。目前还没有研究证明三氧化二砷（As₂O₃）对 Survivin 及其剪接变异体的剪接机制有任何影响，因此本研究旨在确定 As₂O₃对 MCF-7 细胞中 Survivin 剪接变异体的表达模式的细胞毒性作用。As₂O₃以浓度依赖的方式抑制 MCF-7 细胞的生长。Muse Cell Analyser 显示，As₂O₃诱导的 G2/M 细胞周期阻滞，促进 caspase 依赖性细胞凋亡，而不会对 MCF-7 细胞的线粒体膜造成任何损伤。As₂O₃还使 MCF-7 细胞中的两条存活途径失活，即有丝分裂原活化蛋白激酶（MAPK）和磷脂酰肌醇 3-激酶（PI3K）信号通路。两条通路失活伴随着 Survivin 3α在 As₂O₃诱导的 G2/M 细胞周期阻滞和凋亡过程中的上调。发现 Survivin 2B 仅在 As₂O₃诱导的 G2/M 细胞周期阻滞过程中上调，而在 As₂O₃诱导的凋亡过程中下调。野生型 Survivin 在未经处理的 MCF-7 细胞中高度表达，在 As₂O₃诱导的 G2/M 细胞周期阻滞过程中上调，并在 As₂O₃诱导的凋亡过程中下调。未在未经处理和处理的 MCF-7 细胞中检测到 Survivin 变异体ΔEx3。Survivin 蛋白在 MCF-7 细胞的细胞核和细胞质中均有定位，并且在 As₂O₃诱导的 G2/M 细胞周期阻滞过程中高度上调，这可能归因于 Survivin-2B 的上调。本研究首次提供了证据表明，新型 Survivin 2B 剪接变异体可能仅参与了 As₂O₃诱导的 G2/M 细胞周期阻滞的调节。因此，该剪接变异体可作为针对 Luminal A 型乳腺癌细胞的治疗靶点。
