Combination of nelfinavir and tamoxifen enhances the effect of nelfinavir-induced pathways. The oestrogen receptor-positive breast cancer cell lines MCF7 and T47 D and the oestrogen receptor-negative breast cancer cell lines MDA-MB-435 and MDA-MB-453 were incubated with the indicated nelfinavir (NFV) and tamoxifen (TAM) concentrations for 48 hours and were analysed by Western blotting. Staining intensities of selected bands were analysed using a gel documentation system and program (BioRad Quantity One; BioRad, Munich, Germany), and were related to the corresponding β-actin expression value as an internal control (CON). For autophagy marker light chain 3B (LC3B) expression, the lower LC3B-II band was used for calculations. BiP, binding protein; T/N, tamoxifen and nelfinavir combination.