Limiting dilution analysis for detection of residual leukemic cells after bone marrow combined decontamination with mafosfamide followed by merocyanine-540-mediated photosensitization

Efficient photodynamic action of Victoria blue BO against the human leukemic cell lines K-562 and TF-1

Photodynamic induced cytotoxicity by Victoria blue BO (VB-BO), merocyanine 540 (MC540), Nile blue A (NB) and 4-tetrasulfonatophenyl-porphyrin (4-TSPP) has been studied on two human leukemic cell lines: K-562 and TF-1. Cells were incubated with dyes and irradiated with different doses of white light. Cell survival was assessed by propidium iodide (PI) staining using flow cytometry analysis. Concentrations of 5 x 10(-8) M VB-BO were found to kill 75% of cells, and a concentration of 1 x 10(-7) M induced more than 99% of cell killing. To obtain the same cytotoxic level, the presence of 2.6 x 10(-5) M of MC540 during irradiation was needed. Under the conditions used, NB was ineffective as a photosensitizer, although uptake studies showed that this dye was taken by the cells in much greater amounts than any other studied dye. Cell cycle distribution of TF-1 cells, surviving MC540 or VB-BO photosensitization has been studied by flow cytometry analysis after staining with Hoechst 33342 and PI. It was found that cells in G1 phase were slightly more resistant toward MC540- and VB-BO-mediated photosensitization than cells in other phases of the cell cycle.

Phototherapy, photochemotherapy, and bone marrow transplantation

Recent preclinical and clinical investigations indicate that phototherapy and photochemotherapy may have applications that go far beyond their "traditional" roles in the treatment of skin disorders, selected solid tumors, and neonatal hyperbilirubinemia. Bone marrow transplantation is one area that may benefit substantially from these new developments. This review focuses on new applications of phototherapy and photochemotherapy that pertain to the inactivation of tumor cells in autologous bone marrow grafts, the prevention and treatment of acute and chronic graft-versus-host disease, the prevention of transfusion-induced allosensitization and graft rejection, and the inactivation of pathogenic viruses and parasites in bone marrow grafts and blood products.