HIF1A and infection: To get a better infection efficacy of adenoviruses in CRC cancer cell lines, HT29 and HCT116 cells were first transduced with adenovirus 5 expressing enhanced green fluorescent protein (Ad5-EGFP) or Ad5-HIF-1α-EGFP at the multiplicity of infection (MOI) of 10, 100 and 1000, respectively, with the effects recorded by microscopy on 48 hours (Fig 1A).