STAT1 and neoplasm: Inasmuch as both Stat1 [53] and p27Kip1[55] are involved in suppression of angiogenesis and Stat1 phosphorylation is affected by tumor hypoxia [56], tumor microenvironment may have more pronounced effects on the inhibition of tumor growth of Ras-transformed cells containing Stat1S727A than cells containing Stat1 WT.