DLL4 and neoplasm: Prior to testing the TNP efficacy in tumor-bearing SS.BN3IL2Rγ- and SSIL2Rγ- rats, a MRI study was performed (n = 3 rats per strain) to identify the optimal time point for PTT after systemic injection of TNPs and to detect if there were differences in overall TNP uptake in the tumors on the DLL4-high and DLL4-low host strains.