SMAD4 and pancreatic neoplasm: Interestingly, loss of SMAD4 in pancreatic cancer cells has been shown to shift TGFβ-triggered downstream cascades to mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) signaling, a pathway also known to be triggered upon CXCR4 activation (Bianchi and Mezzapelle, 2020; Hong et al., 2009).