MMP9 and neuroblastoma: The formation of this signaling complex at the plasma membrane regulates Rac activation through the PI3k/Akt pathway to promote cellular invasion, a result that is consistent with the finding that ATRA promotes activation of Rac in neuroblastoma cells [40] and increases the invasion of pancreatic cancer cells [7,41] and promotes MMP-9 expression through RARα [42].