Interferon-alpha 2b modulation of doxorubicin sensitivity in a multidrug resistant cell line

We evaluated the effect of interferon-alpha2b as a chemosensitiser on HCT-1 5 cell line in treatment with doxorubicin. Chemosensitivity was determined by [H-3]-thymidine incorporation and tetrazolium. assays. The levels of exp ression of P-glycoprotein, Bcl-2 oncoprotein and HLA-ABC complex,, and cell cycle/apoptosis analysis were determined by flow cytometry. Dox 50 ng/ml - IFN alpha 2b 500 IU/ml treatment inhibited cell proliferation (47.2 +/- 1. 4 %, p< 0.0001; MTT assay: 40.6 +/- 1.2 %, p < 0.0001) and augmented the ex pression of P-170, Bcl-2 and HLA-ABC, while it didn't exert apoptosis, prod ucing a slight G2/M arrest. A concentration of IFN-alpha 2b, that by itself is not cytotoxic, can potentiate the efficacy of the anticancer drug. This effect is not due to a downmodulation of P-170. The absence of apoptosis a nd augmented levels of Bcl-2 expression suggests that this could be one of the mechanisms of drug resistance exerted by these cells.