Treatment of Peritoneal Carcinomatosis by Targeted Delivery of the Radio-Labeled Tumor Homing Peptide 213Bi-DTPA-[F3]2 into the Nucleus of Tumor Cells

Background α-particle emitting isotopes are effective novel tools in cancer therapy, but targeted delivery into tumors is a prerequisite of their application to avoid toxic side effects. Peritoneal carcinomatosis is a widespread dissemination of tumors throughout the peritoneal cavity. As peritoneal carcinomatosis is fatal in most cases, novel therapies are needed. F3 is a tumor homing peptide which is internalized into the nucleus of tumor cells upon binding to nucleolin on the cell surface. Therefore, F3 may be an appropriate carrier for α-particle emitting isotopes facilitating selective tumor therapies. Principal Findings A dimer of the vascular tumor homing peptide F3 was chemically coupled to the α-emitter 213 Bi ( 213 Bi-DTPA-[F3] 2 ). We found 213 Bi-DTPA-[F3] 2 to accumulate in the nucleus of tumor cells in vitro and in intraperitoneally growing tumors in vivo. To study the anti-tumor activity of 213 Bi-DTPA-[F3] 2 we treated mice bearing intraperitoneally growing xenograft tumors with 213 Bi-DTPA-[F3] 2 . In a tumor prevention study between the days 4–14 after inoculation of tumor cells 6×1.85 MBq (50 µCi) of 213 Bi-DTPA-[F3] 2 were injected. In a tumor reduction study between the days 16–26 after inoculation of tumor cells 6×1.85 MBq of 213 Bi-DTPA-[F3] 2 were injected. The survival time of the animals was increased from 51 to 93.5 days in the prevention study and from 57 days to 78 days in the tumor reduction study. No toxicity of the treatment was observed. In bio-distribution studies we found 213 Bi-DTPA-[F3] 2 to accumulate in tumors but only low activities were found in control organs except for the kidneys, where 213 Bi-DTPA-[F3] 2 is found due to renal excretion. Conclusions/Significance In conclusion we report that 213 Bi-DTPA-[F3] 2 is a novel tool for the targeted delivery of α-emitters into the nucleus of tumor cells that effectively controls peritoneal carcinomatosis in preclinical models and may also be useful in oncology.