MAPK3 and neoplasm: We observed a decrease in p‐ERK1/2 upon silencing of EPHA4 in PDO, whereas overexpressing EPHA4 resulted in an increase of p‐ERK1/2 (Figure S16K, Supporting Information), consistent with prior studies.[50, 52] In addition, we noted a similar behavior in p‐MEK1/2 to that of p‐ERK1/2, potentially elucidating how EPHA4 could impact tumor sensitivity to the MEK inhibitor.