ATM and cancer: Furthermore, the phosphorylation of STAT1, a key transcription factor downstream of IFNβ pathway that contributes to the activation of IFN-stimulated genes, was also enhanced upon ATM inhibition in a panel of human and murine cancer cells (BT549, MDA-MB-231, H1299, H157, A549, B16-F10 and MC-38) (Fig. 3I, Fig. S3C).