CASP3 and pancreatic insulinoma: As a positive control, we showed increased abundance of cleaved caspase 3 by immunofluorescence (IF) staining in 832/13 rat insulinoma cells treated with the apoptotic inducer camptothecin (22) (Fig. 7E) coinciding with a 40% loss in cellular viability assessed by MTS assay (data not shown).