DLL4 and neoplasm: Dll4 allelic deletion or sDll4 treatment reduces the rate of tumor growth in this spontaneous model of insulinoma in the pancreas, while the number of tumors per mouse were unchanged, indicating that the transforming event caused by SV40 large T antigen under insulin promoter is independent on Dll4/Notch pathway, while the tumor growth is promoted by the expression of Dll4 in the vasculature.