MAPK3 and neoplasm: For instance, exosomes derived from rat pancreatic adenocarcinoma have been observed to activate cytotoxic T cell (CTL) responses specific to tumor antigens while simultaneously inhibiting leukocyte proliferation by downregulating the Zeta chain of T cell receptor-associated protein kinase 70 (ZAP70) and extracellular signal-regulated kinases 1,2 (ERK1,2) [117].