Purge of malignant cells from bone marrow by hematoporphyrin derivatives and light exposure in vitro

During autologous bone marrow graft in treatment of malignant diseases, it is critical to purge malignant cells from the marrow. In the present study, the sensitivity to photodynamic inactivation of 3 leukemic cell lines was compared with their counterpart normal hematopoietic cells. After mouse leukemic L1210 cells were treated with a preparation of hematoporphyrin derivatives, YHpD, 10 micrograms/ml for 1 h and irradiated with black light (peak wavelength 395 nm, light intensity 0.6 mW/cm2) for 5 min, the survival rate of clonogenic cells decreased to less than 10%, while that of bone marrow granulocyte-macrophage progenitor cells (CFU-GM) in DBA/2 mice remained at nearly normal level (greater than 80%). Similar results were obtained when human leukemic HL-60 cells were compared to human CFU-GM and mouse leukemic L615 cells to CFU-GM in 615 strain mice. It is suggested that hematoporphyrin photoradiation may be useful for selectivity killing leukemic cells in bone marrow.