Fig. 5. Capsaicin co-treatment with erlotinib synergistically enhanced cytotoxicity. (A) Erlotinib and capsaicin were combined at a ratio of 1 : 5 or 1 : 20 and the MTS assay was used to analyze cell viability. (B) The mean CI values at a fraction affected (FA) of 0.50, 0.75, 0.90 for erlotinib and capsaicin combined treatment were averaged for three independent experiments. (C) Cells were treated with capsaicin (25, 50 μM) and/or erlotinib (5 μM) for 1–3 days, after which living cells were determined by MTS assay. **p < 0.01 using Student's t-test for comparison between cells treated with a drug alone or with a capsaicin/erlotinib combination. **p < 0.01 using Student's t-test for comparison between cells treated with a drug alone or with the capsaicin/erlotinib combination.