PGAM1 and cancer: We investigated whether the PGAM1-Chk1 interaction might be involved in the oncogenic Ras-induced senescence (OIS) of human cells on the basis of our previous findings that oncogenic stimuli provoked this interaction in cancer cells.23 PGAM1, one of two isoforms of PGAM, is expressed predominantly in human primary fibroblasts (Supplementary Fig. 1a).23 For this purpose, we utilized the NanoLuc Binary Technology (NanoBiT) system to detect the PGAM1-Chk1 interaction (Fig. 1a).