Survivin Splice Variants in Arsenic Trioxide (As₂O₃)-Induced Deactivation of PI3K and MAPK Cell Signalling Pathways in MCF-7 Cells.

Kagiso Laka,Lilian Makgoo,Zukile Mbita

doi:10.3390/genes10010041

Abstract

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.

Highlights

According to the National Cancer Registry (NCR), more than 100,000 South Africans are diagnosed with cancer each year, of which 21% is attributed to breast cancer [1]
This study focused on analysing the expression pattern of the different survivin splice variants during both As2 O3 -induced apoptosis and cell cycle arrest in breast cancer MCF-7 cells
The purpose of this investigation was to evaluate the potential effect of As2 O3 on the expression of the different survivin splice variants during cell cycle progression and apoptosis of breast cancer cell line, MCF-7

Summary

Introduction

According to the National Cancer Registry (NCR), more than 100,000 South Africans are diagnosed with cancer each year, of which 21% is attributed to breast cancer [1]. Development of breast cancer is characterized by the deregulation of cell cycle control and resistance to apoptosis [2]. Tumour cells can 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 [3]. These proteins inhibit apoptosis by hindering caspase cascade and inhibiting both intrinsic and extrinsic pathways [4]. As reviewed in Mohammad et al [5], Bcl-2 family of proteins, autophagy, proteasome pathway and epigenetics all play a role in resistance to apoptosis

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