MAPK3 and acute lymphoblastic leukemia: Analysis of the phosphorylation status of signaling proteins in the unstimulated condition—which captures intrinsic signaling alterations—documents constitutive phosphorylation of pErk1/2, pNF-κB p65, pLck, ZAP70Y319, and pSTAT3 in all T-ALL cell lines, with a higher activation of Erk1/2, Lck, and ZAP70Y319 in Jurkat and higher levels of basal pSTAT3 in MOLT4 cells.