Figure 3.

The excess cytotoxicity of cytarabine in MMR-deficient cells is associated an increase in markers of apoptosis and DNA damage. (A) Immunoblot assessing the effects of cytarabine treatment on protein levels. Lysates were obtained from HCT116+/−Chr3 cells exposed to cytarabine (ara-C), or control, for 72 h. Lysates were immunoblotted and probed for expression of PARP, MLH1, γH2AX, and β-actin as a loading control. (B) Bar graph demonstrating percentage change in γH2AX-positive cells by confocal microscopy following treatment with 50 nℳ cytarabine for 24 h, compared with controls. Cells were fixed 24 h following cytarabine exposure. ⩾5 foci per cell was defined as a positive cell. At least 100 cells were counted in a minimum of seven representative fields. (C) Merged images of control (PBS-treated) HCT116 and HCT116+Chr3 cells (top panels) and cytarabine-treated cells (bottom panels). Cells were stained for γH2AX (red) and DAPI (blue).