ATM and colorectal carcinoma: Here we followed ATM activation, indicated by ATM-pS1981 (pATM), in response to hypoxia (18 h, 0.1% O2) in two different cancer cell lines (human follicular thyroid carcinoma cells FTC133 and human colorectal carcinoma HCT116 cells) and this was compared to ATM auto-phosphorylation in normoxia (21% O2) (Figure 1A).