E-Mail IMAGE: Regulation of "spine " molecules in HL-60 wt versus Fgr KO cells by RA. HL-60 wt and FGR KO cells were cultured for 72 h in the absence or presence of... view more Credit: Correspondence to - Andrew Yen - ay13@cornell.edu Using a leukemic patient-derived in vitro model of a non-APL AML, these authors previously found that RA evokes activation of a macromolecular signaling complex, a signalosome, built of numerous MAPK-pathway-related signaling molecules; and this signaling enabled Retinoic-Acid-Response-Elements to regulate gene expression that results in cell differentiation/cell cycle arrest. Toward mechanistic insight into the nature of this novel signaling, they now find that the NUMB cell fate determinant protein is an apparent scaffold for the signalosome.