Interactions of merocyanine 540 with human brain tumor cells

Merocyanine 540 (MC 540), a photosensitizing dye, has been used in preclinical studies and in a phase I clinical trial for the purging of leukemia, lymphoma, and neuroblastoma cells from bone marrow grafts. We evaluated MC 540 as an agent for the inactivation of brain tumor cell lines of medulloblastoma or glioma origin. The U373 glioma and 74SA medulloblastoma demonstrated significantly reduced survival as determined by in vitro clonogenic assay compared to normal glial cells when exposed to MC 540 and light. U87 glioma and Daoy medulloblastoma, however, were less sensitive than normal glial cells to MC 540 photoinactivation. In vivo injection of MC 540 into mice with malignant brain tumors disclosed greater dye incorporation into the malignant tissue compared with normal control mice brains or normal tissue surrounding the brain tumor. Increased uptake of MC 540 was observed in mice injected with either photosensitive (U373 and 74SA) or photoresistant (Daoy) cell lines. These data suggest that MC 540 may be an effective agent against certain brain tumors and that dye uptake in vivo does not reflect photosensitivity.