Flt3 mutation, potentiated STAT and MAPK signaling, and Bcl-2 expression are part of a common pathway opposing p53 activity in AML patients. (A) Western blots of the Molm-13 cell line left untreated or stimulated with 20 ng/mL GM-CSF were used to determine whether upstream signaling observed to be important in profiles of STAT and MAPK signaling increases the level of Bcl-2 expression. Actin and Flt3 are shown as controls. (B) Relationships between p53 phosphorylation, p53 expression, and Bcl-2 expression were plotted in 3 dimensions based on correlation coefficient (r²) for the 30 AML patient samples. All relationships where r² was more than 0.60 (solid lines) were plotted. Lines shown are of length 1 − r² units; the closer the correlation between 2 biomarkers in AML blasts, the closer the lines on this graph. Patients with Flt3-LM-DupY591 expressed higher levels of Bcl-2 and phosphorylated p53, relative to other AML samples, as indicated by brackets. Refer to Figure S1 and Table S3 for more information. (C) A graph summarizes chemotherapy response, AML signaling cluster,¹  and Flt3 mutational status. No AML patient with Flt3-LM-SPY591 responded to course one of chemotherapy and these patients primarily displayed a potentiated type 2 signaling profile (SC-P2), as was commonly observed in patients with Flt3-LM. SC-P2 was characterized primarily by potentiated Stat5 and Stat3 signaling responses and an attenuated Stat1 response to IFN-γ. Refer to Table S1 for more information.