Enhanced therapeutic effect on murine melanoma and angiosarcoma cells by boron neutron capture therapy using a boronated metalloporphyrin.

We have already achieved successful treatment of several human patients with malignant melanoma by boron neutron capture therapy (BNCT) using 10B1-paraboronophenylalanine (10B1-BPA). In this communication we used a new compound, a manganese boronated protoporphyrin (Mn-10BOPP), and compared it to 10B1-BPA.HCl with respect to uptake in murine melanoma and angiosarcoma cells as well as to their respective cell killing effects using BNCT. Mn-10BOPP was found to be 3 to 10 times more effectively taken up by melanoma cells and angiosarcoma cells than 10B1-BPA.HCl when the content of 10B was measured by the new method, inductively coupled plasma-mass spectrometry (ICP-MS). In addition, melanoma cells and angiosarcoma cells preincubated with Mn-10BOPP were 15 to 20 times more efficiently killed by BNCT than cells preincubated with 10B1-BPA.HCl. These results suggest that Mn-10BOPP is a suitable compound for BNCT of not only malignant melanoma but also angiosarcoma.