MDC1 and cancer: After p-ATM-mediated phosphorylation of H2AX following DNA damage arising from radiation and/or anti-cancer drugs, MDC1 (mediator of DNA damage checkpoint protein 1)/NFBD1 (nuclear factor with BRCT domains protein 1) (henceforth NFBD1) binds to γH2AX and serves as an anchor protein for the subsequent recruitment of MRN (Mre11-Rad50-Nbs1) DNA damage sensor complex [3,4,5].