Tamoxifen and the PI3K Inhibitor: LY294002 Synergistically Induce Apoptosis and Cell Cycle Arrest in Breast Cancer MCF-7 Cells

Mohamed E Abdallah,Abdullatif Taha Babakr,Bassem Refaat,Riyad Adnan Almaimani,Waleed Hassan Almalki,Omer Fadul Idris,Ashraf N Abdalla,Amar Mohamed Ismail,Shakir Idris,Mohammad Ahmad Althubiti,Mahmoud Zaki El-Readi,Mohammed H Mukhtar

doi:10.3390/molecules25153355

Mohamed E Abdallah, Abdullatif Taha Babakr + Show 10 more

Open Access

https://doi.org/10.3390/molecules25153355

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Abstract

Breast cancer is considered as one of the most aggressive types of cancer. Acquired therapeutic resistance is the major cause of chemotherapy failure in breast cancer patients. To overcome this resistance and to improve the efficacy of treatment, drug combination is employed as a promising approach for this purpose. The synergistic cytotoxic, apoptosis inducing, and cell cycle effects of the combination of LY294002 (LY), a phosphatidylinositide-3-kinase (PI3K) inhibitor, with the traditional cytotoxic anti-estrogen drug tamoxifen (TAM) in breast cancer cells (MCF-7) were investigated. LY and TAM exhibited potent cytotoxic effect on MCF-7 cells with IC50 values 0.87 µM and 1.02 µM. The combination of non-toxic concentration of LY and TAM showed highly significant synergistic interaction as observed from isobologram (IC50: 0.17 µM, combination index: 0.18, colony formation: 9.01%) compared to untreated control. The percentage of early/late apoptosis significantly increased after treatment of MCF-7 cells with LY and TAM combination: 40.3%/28.3% (p < 0.001), compared to LY single treatment (19.8%/11.4%) and TAM single treatment (32.4%/5.9%). In addition, LY and TAM combination induced the apoptotic genes Caspase-3, Caspase-7, and p53, as well as p21 as cell cycle promotor, and significantly downregulated the anti-apoptotic genes Bcl-2 and survivin. The cell cycle assay revealed that the combination induced apoptosis by increasing the pre-G1: 28.3% compared to 1.6% of control. pAKT and Cyclin D1 protein expressions were significantly more downregulated by the combination treatment compared to the single drug treatment. The results suggested that the synergistic cytotoxic effect of LY and TAM is achieved by the induction of apoptosis and cell cycle arrest through cyclin D1, pAKT, caspases, and Bcl-2 signaling pathways.

Highlights

Worldwide, breast cancer (BC) has the highest incidence rate (24.2%) of all cancers in women with more than two million newly diagnosed cases and almost 627,000 deaths (15%) occurred in 2018 [1].In Saudi Arabia, BC has the largest number of incidences between females (3629 cases: 29.7% of total malignancies) [2]
BC is classified according to the gene expression of estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2) into five major molecular subtypes, which are different in growth and prognosis
The ability of LY to improve the cytotoxicity of tamoxifen on MCF-7 breast cancer was evaluated ability of LY

Summary

Introduction

Breast cancer (BC) has the highest incidence rate (24.2%) of all cancers in women with more than two million newly diagnosed cases and almost 627,000 deaths (15%) occurred in 2018 [1]. In Saudi Arabia, BC has the largest number of incidences between females (3629 cases: 29.7% of total malignancies) [2]. Frequent tumor recurrence results in poor prognosis of BC patient of which less than 5% survive for more than ten years [3]. Theses subtypes include luminal A (ER+ /HER2− /low levels of Ki-67 protein), luminal B (ER+ /HER2−/+ /high levels of Ki-67 protein), triple-negative/basal-like (ER− /HER2− ), HER2 enriched (HR− /HER2+ ), and normal-like BC, which is similar to luminal A, but with poor prognosis [5]

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