Figure 1. Lack of cytotoxic and autophagy-inhibiting activity of CQ in acidic conditions. (A) HCT116 and HT29 human colon carcinoma xenografts were treated with vehicle (n = 8) or with CQ (20 mg/kg, n = 8) administered i.p. every second day and tumor volume was monitored for 16 d. (B) The effects of CQ treatment on cell viability were analyzed in HCT116 and Me30966 cells cultured at pH 7.4 or pH 6.8 for 48 h. Data are presented as means ± standard deviations from 2 independent experiments. (C) Me30966 cells were plated in normal RPMI medium and the next day the medium was replaced with media at the indicated pH. Cells were incubated with fresh media for 24 h and BafA1 (50 nM) or CQ (50 μM) added during the last 4 h before collection of cells for WB analysis of LC3 expression. Representative WB analysis shows that CQ does not cause LC3-II accumulation at acidic pH. LC3-II signal in the histograms was quantified by densitometric analysis of 3 independent experiments using Adobe Photoshop and the ratio LC3-II/ACTB was calculated, using the values of the control cells at pH 7.4 for data normalization.