H2AX and cancer: Consistently, 24 h treatment of 2.0 mM sodium butyrate alone did not affect cell viability, with no detectable increase in the γ-H2AX foci in either HEK293 or cancer MCF-7 cells line; however, when combined with etoposide, 2.0 mM butyrate sensitized MCF-7 cancer cells but not HEK293 cells to produce more γ-H2AX foci.