MRE11 and colorectal carcinoma: Even the cell lines that had little or no detectable levels of Mre11 (RKO, LS411N, HCT116; Figure 1) did not respond to niraparib monotherapy in the EC50 ranges that BRCA deficient cell lines do (EC50s ≥ 1000 nM for MSI CRC cell lines and EC50s ≤ 100 nM for BRCA1/2 mutant cell lines using the same assay conditions) (Figure 2A and Table 1; [3]).