AK4 and non-small cell lung carcinoma: Next, we detected endogenous AK4 and HIF-1α protein expression in 17 human NSCLC cell lines and found that CL1-5, H441, H157, and CL1-3 cells expressed high levels of HIF-1α under normoxic conditions (95% air, 5% CO2) and those cells also expressed high levels of AK4 (Fig. 3a, upper).