MAPK8 and pancreatic insulinoma: To dissect mechanistic details of the inhibitory effect of photoactivated hypericin on RINm5F insulinoma cell proliferation, we next evaluated if photoactivated hypericin influenced protein levels of the mitogen-activated protein kinases (MAPKs) phospho-JNK, phospho-ERK and phospho-p38 by employing immunoblot analysis.