MAPK3 and colitis: Since the STAT3 and ERK1/2 signaling pathways are downstream of EGFR, we quantified the transcript expression of Egfr and all 7 known EGFR ligands — Ereg, Areg, Egf, Hbegf, Tgfa, Epgn, and Btc — in colitis-associated tumors from Phd2+/– and WT control mice by qRT-PCR.