A DNA damage response-like phenotype defines a third of colon cancers at onset. Supplementary data.

A third of de-novo presentations of colorectal cancer display foci of positivity for ℽH2AX, pCHK2, pNBS1 in the absence of apoptosis or senescence associated p21/CDKN1A. This phenotype is reminiscent of an ongoing DNA damage response (DDR).

The TP53 status, the chromosome 20q amplification or the microsatellite instability gene status did not correlate with the DDR phenotype, except for a preferential association with MSH2/MSH6 inactivation and conserved MLH1. Additional lesions of DDR-associated genes may be responsible for this phenotype, which is absent from the remaining cases in this cohort. The outcome, after adjuvant treatment with DNA-damaging drugs, did not differentiate this group from the remaining cases.