IRF1 and esophageal squamous cell carcinoma: ESCC cells were transiently transfected with either empty vector, wild-type STAT1β or STAT1βY701F, then the mRNA expression levels of several known STAT1 downstream targets (including IRF1, TAP1, CXCL10, GBP2 and ICAM10) were analyzed.11 Compared to transfection with empty vector, STAT1β transfection at 24 h significantly increased the mRNA expression of all five target genes examined (Figure 3c).