JPM-OEt (50 mg/kg; i.p.; daily for 30 days) reduces tumor cathepsin B activity significantly. JPM-OEt (50 mg/kg; i.p.; twice daily for 4 weeks) leads to tumor regression in the RIP1-Tag2 (RT2) mouse model of pancreatic islet cell tumorigenesis. JPM-OEt (50 mg/kg; i.p.; daily from 63 to 98 days) causes a significant delay in the increase of tumour burden during the first 2 weeks of treatment.