STAT1 and lymphoma: What is more, 5 μM STI-571 completely inhibited the STAT1 phosphorylation in ABPC 20 and pre B v-Abl lymphoma and the STAT3 tyrosine phosphorylation in pre B v-Abl, and it virtually completely inhibited the tyrosine and serine phosphorylation of STAT3 in ABPC 20.