Tumor Necrosis Factor Alpha Induces Stronger Cytotoxicity in ABCG2-Overexpressing Resistant Breast Cancer Cells Compared with Their Drug-Sensitive Parental Line

Tumor necrosis factor alpha (TNF-alpha) has been reported to modulate the multidrug resistance (MDR) phenotype in vitro and in vivo. Multidrug-resistant cells overexpressing the ABCB1 transporter are more susceptible to inhibition of proliferation and induction of apoptosis by TNF-alpha than their drug-sensitive counterparts. This study was aimed to investigate TNF-alpha modulatory and antiproliferative effects on drug-resistant cells overexpressing ABCG2. The effects of TNF-alpha on viability and proliferation rate of MCF-7 breast cancer cells and their ABCG2-overexpressing sublines MCF-7/mitoxantrone (MX) cells were studied using dye exclusion assay, dimethylthiazolyl-2,5-diphenyl tetrazolium bromide technique, and flow cytometric analysis of cell cycle. TNF-alpha influence on MX accumulation was investigated by flow cytometry. ABCG2-overexpressing cells were more susceptible to antiproliferative and cytotoxic effects of TNF-alpha than their parental cells. TNF-alpha increased accumulation of MX in both parental and resistant cells. Higher sensitivity of MDR cells to TNF-alpha cytotoxicity would help in characterization of its complex modulatory effects on cancer cells and benefit us in designing new approaches to overcome MDR.