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. Author manuscript; available in PMC: 2015 Jul 1.
Published in final edited form as: Breast Cancer Res Treat. 2014 Jun 12;146(2):259–272. doi: 10.1007/s10549-014-3014-7

Fig. 7.

Fig. 7

Entinostat enhances trastuzumab/lapatinib efficacy in trastuzumab/lapatinib-resistant HER2+ breast cancer cells. Trastuzumab/lapatinib-resistant SUM190 cells (SUM190-TLR) were obtained by continuously exposing SUM190 cells (which are known to be trastuzumab resistant) to lapatinib (5 μg/ml) for 6 months. Dose-effect curve was analyzed using CalcuSyn software (Biosoft, Cambridge, UK). Combination index (CI) of entinostat, lapatinib and trastuzumab in SUM190-TLR cells: A quantitative measure of the degree of drug interaction. CI value: <0.1 indicates very strong synergism; 0.10-0.30, strong synergism; 0.30-0.70, synergism; 0.70-0.85, moderate synergism; 0.85-0.90, slight synergism; 0.90-1.10, nearly additive; 1.10-1.20, slight antagonism; 1.20-1.45, moderate antagonism; 1.45-3.3, antagonism; 3.3-10, strong antagonism; >10, very strong antagonism. Fractional index (Fa), the fraction of cells affected by the dose.