Phorbol Ester TPA Modulates Chemoresistance in the Drug Sensitive Breast Cancer Cell Line MCF-7 by Inducing Expression of Drug Efflux Transporter ABCG2

Fatemeh Kalalinia,Javad Behravan,Fatemeh Elahian,Mitra Hassani,Jamal Kasaeeian

doi:10.7314/apjcp.2012.13.6.2979

Abstract

Recent studies have indicated a link between levels of cyclooxygenase-2 (COX-2) and development of the multidrug resistance (MDR) phenotype. The ATP-binding cassette sub-family G member 2 (ABCG2) is a major MDR-related transporter protein that is frequently overexpressed in cancer patients. In this study, we aimed to evaluate any positive correlation between COX-2 and ABCG2 gene expression using the COX-2 inducer 12-O-tetradecanoylphorbol-13-acetate (TPA) in human breast cancer cell lines. ABCG2 mRNA and protein expression was studied using real-time RT-PCR and flow cytometry, respectively. A significant increase of COX-2 mRNA expression (up to 11-fold by 4 h) was induced by TPA in MDA-MB-231 cells, this induction effect being lower in MCF-7 cells. TPA caused a considerable increase up to 9-fold in ABCG2 mRNA expression in parental MCF-7 cells, while it caused a small enhancement in ABCG2 expression up to 67 % by 4 h followed by a time-dependent decrease in ABCG2 mRNA expression in MDA-MB-231 cells. TPA treatment resulted in a slight increase of ABCG2 protein expression in MCF-7 cells, while a time-dependent decrease in ABCG2 protein expression was occurred in MDA-MB-231 cells. In conclusion, based on the observed effects of TPA in MDA-Mb-231 cells, it is proposed that TPA up-regulates ABCG2 expression in the drug sensitive MCF-7 breast cancer cell line through COX-2 unrelated pathways.

Highlights

In cancer treatment, prolonged chemotherapy could lead to the selective survival of multidrug resistant (MDR) cells that exhibit simultaneous resistance to a wide spectrum of structurally and functionally unrelated chemotherapeutic agents
On the other hand, interesting results were observed in MDA-MB-231 (Figure 3C), whereas small enhancement in ATP-binding cassette sub-family G member 2 (ABCG2) expression up to 67 % was observed in 4 h while increasing the incubation time reverse this process and showed a time-dependent decrease to about 85 % in ABCG2 expression
At basal level, higher Fluorescein isothiocyanate (FITC) fluorescence of MCF-7/MX histogram was observed in compared to FITC fluorescence of MCF-7 and MDA-MB231 histogram which confirmed the overexpression of ABCG2 protein in MCF7/MX cells (Figure 4)

Summary

Introduction

In cancer treatment, prolonged chemotherapy could lead to the selective survival of multidrug resistant (MDR) cells that exhibit simultaneous resistance to a wide spectrum of structurally and functionally unrelated chemotherapeutic agents. One of the mechanisms leading to MDR is the over-expression of membrane efflux protein breast cancer resistance protein (BCRP). The 72 kDa breast cancer resistance protein (BCRP) is the second member of the subfamily G of the human ATP binding cassette (ABC) transporter superfamily, designated as ABCG2 (Mao & Unadkat, 2005). ABCG2 expression has been detected in a large number of hematological malignancies and solid tumors, indicating that this transporter may play an important role in clinical drug resistance of cancers (Ross et al, 2000; Diestra et al, 2002)

Objectives

Methods

Results

Conclusion