The effects of nicotine or cotinine exposure on H841 cell proliferation. (A,B) Cell titer blue assay, showing that nicotine/cotinine exposure has no effect on H841 cell viability. H841 cells treated with 1 µM nicotine or 10 µM cotinine for two days (A), or five days (B), followed by cell titer blue analysis. (C) Histogram, showing that nicotine/cotinine exposure has no effect on H841 cell proliferation. H841 cells treated with 10 µM nicotine or 10 µM cotinine for five days and counted. (D,E) Colony formation analysis, indicating that nicotine/cotinine treatment has no effect on H841 cell proliferation. H841 cells treated with 10 µM nicotine or 10 µM cotinine for 2 weeks, followed by colony formation analysis.