Synergistic Interactions of 5-Fluorouracil with Inhibitors of Protein Kinase CK2 Correlate with p38 MAPK Activation and FAK Inhibition in the Triple-Negative Breast Cancer Cell Line.

Patrycja Wińska,Mirosława Koronkiewicz,Maria Jolanta Rędowicz,Olena Karatsai,Konrad Chojnacki,Monika Staniszewska

doi:10.3390/ijms21176234

Abstract

Background: The combination effect of 5-fluorouracil (5-FU) with either CX-4945 or a new inhibitor of protein kinase CK2, namely 14B (4,5,6,7-tetrabromo-1-(3-bromopropyl)-2-methyl-1H-benzimidazole), on the viability of MCF-7 and triple-negative MDA-MB-231 breast cancer cell lines was studied. Methods: Combination index (CI) values were determined using an MTT-based assay and the Chou-Talalay model. The effect of the tested drug combinations on pro-apoptotic properties and cell cycle progression was examined using flow cytometry. The activation of FAK, p38 MAPK, and ERK1/2 kinases and the expression of selected pro-apoptotic markers in MDA-MB-231 cell line after the combined treatment were evaluated by the western blot method. Confocal microscopy was used to examine actin network in MDA-MB-231. Results: Our results showed that a synergistic effect (CI < 1) occurred in MDA-MB-231 after treatment with both combinations of 5-FU with 14B or CX-4945, whereas the combination of 5-FU and 14B evoked an antagonistic effect in MCF-7. We conclude that the synergistic interactions (CI < 1) observed for both the combinations of 5-FU and 14B or CX-4945 in MDA-MB-231 correlated with an activation of p38 MAPK, inhibition of FAK, increased expression of apoptogenic markers, prolongation of S-phase of cell cycle, and destabilization of actin network. Conclusions: The obtained results support the recent observation that CK2 inhibitors can improve 5-FU-based anticancer therapy and FAK kinase can be an attractive molecular target in breast cancer therapy.

Highlights

Breast cancer is the most common malignancy among women worldwide and is the second most frequent cause of death in women [1]
Patients with triple-negative breast cancer (TNBC) are difficult to treat by hormonal or anti-HER2 therapy, and only classical cytotoxic agents, such as 5-fluorouracil (5-FU), offer a viable option for those who develop distant metastasis [4,5]. 5-FU is converted inside cells into 5-fluoro-dUMP (F-dUMP, fluoro-deoxyuridine monophosphate), which forms a stable complex with thymidylate synthase (TS) and inhibits deoxythymidine monophosphate production that is essential for DNA replication and repair [6]
The effect of inhibitors directed against two different molecular targets, i.e., protein kinase CK2 and TS, used alone or in combinations, was studied on two different breast cancer cell lines, MCF-7 and MDA-MB-231

Summary

Introduction

Breast cancer is the most common malignancy among women worldwide and is the second (after lung cancer) most frequent cause of death in women [1]. Breast cancer is categorized into three major subtypes based on the presence or absence of molecular markers for estrogen or progesterone receptors and human epidermal growth factor 2 (ERBB2, formerly HER2): (i) hormone-receptor-positive/ERBB2-negative (70% of patients), (ii) ERBB2-positive (15–20%), and (iii) triple-negative (tumors lacking all three standard molecular markers; 15%) [2]. Depending on their receptor signature, these breast cancer subtypes have distinct neoadjuvant/adjuvant treatments, such as hormonal agents and cytotoxic chemotherapy either simultaneously or consecutively [3]. Conclusions: The obtained results support the recent observation that CK2 inhibitors can improve 5-FU-based anticancer therapy and FAK kinase can be an attractive molecular target in breast cancer therapy

Methods

Results

Conclusion