Hypothetical schema of DNR-induced pathway leading to activation of ERK.

PC-derived DAG and ROS-dependent PI3-K products generated by DNR activate distinct pathways, which converge toward PKCζ. Activated PKCζ is then responsible for the activation of Raf-1/MEK/ERK through a still-unknown mediator. DNR, daunorubicin; PC-PLC, phosphatidylcholine-phospholipase C; DAG, diacylglycerol; ROS, radical oxygen species; PI3K, phosphoinositide-3 kinase; PI3P, phosphatidylinositol-3-phosphate; PKCζ, protein kinase C ζ; MEK, mitogen extracellular kinase; ERK, extracellular-regulated kinase; ?, directly or indirectly.