Effect of chemotherapeutic agents on DNA damage and apoptosis in <i>MSH3</i>-proficient and –deficient cells.

<p>A, Analysis of pH2AX and pChk2 expression and PARP cleavage in <i>MSH3</i>–deficient HCT116+3+5 cells (left) and SW480 cells (right) with constitutive shRNA knockdown of <i>MSH3</i>. Cells were treated with SN-38 or oxaliplatin for 48h. B, C, Immunofluorescence staining to detect the formation of 53BP1 nuclear foci in irradiated (2Gy) HCT116+3+5 cells with control shRNA (left) versus shRNA suppression of <i>MSH3</i> (right). The percentage of cells with >10 53BP1 nuclear foci was determined at the indicated time-points. At least 100 total cells were counted in each slide. D, Analysis of caspase-3/7 activity in HCT116+3+5 cells with and without <i>MSH3</i> knockdown that were treated with 5-FU, SN-38 or oxaliplatin (48 h). E, Analysis of pH2AX and pChk2 expression and PARP cleavage in 5-FU-treated (48h) HCT116+3+5 cells (left) that are <i>MSH3</i>–deficient and in SW480 cells (right) with constitutive shRNA knockdown of MSH3. Data represent mean ± standard errors from 3 independent experiments. Statistical significance was determined by a two-sided Student's t test (* P<0.05; † P<0.01).