| High-dose chemotherapy supported by hematopoietic stem/progenitor cells transplantation (HSCT) presents an effective access of final cure of leukemia. Autologous HSCT (Auto-HSCT) manifests several advantages over allogenous HSCT (Allo-HSCT), such as easy transplantation of grafts, obviating the need for a HLA-matched donor, without the restriction of age and graft versus host disease (GVHD). Auto-HSCT, therefore, presents a promising approach for leukemia therapy. Auto-HSCT, however, bears the risk of reinfusing residual leukemic cells that contribute to disease relapse and purging procedures, therefore, are needed to eliminate the risk. Pharmacological purging techniques and currently available immunotoxins have been employed in attempt to purge residual leukemic cells in remission marrow. However, the non-specific cytotoxicity of chemotherapeutic agents such as cyclophosphamide and lack of monoclonal antibodies to well characterized leukemia antigens have hindered these attempts. An effective purging technique is a key point for successive Auto-HSCT. Photodynamic therapy (PDT) provides a novel approach for the purpose. PDT, widely studied for its anticancer activity, relies on a bimodal protocol comprised of chemical-photosensitization and light-irradiation. The two components are individually nontoxic but tumoricidal in combination. Through the generation of reactive oxygen species (ROS), PDT affects various aspects of cell biology, particularly singlet oxygen, subsequently resulting in the killing of cancerous cells and thereby tumor ablation. Several researchers reported that human leukemic cell lines exhibit higher susceptibility to PDT than normal bone marrow mononuclear cells (MNC). In those reports, however, minimal residual leukemic cells were detected only with colony formation assays, which was not a sensitive and specific technique. Moreover, there was no report about the kinetic change of the content of photosensitizers in normal bone marrow cells and leukemic cells. As a modality of cancer treatment, PDT must lead to irreversible destruction of the tumor tissue, while keeping side effects such as damage to the surrounding normal tissue as low as possible. Furthermore, the intracellular concentration of photosensitizers was one important factor in the effectiveness of PDT. Therefore, PDT essentially requires a combination of high contrast of the concentration of photosensitizer between tumor and surrounding normal tissue and sufficient concentration of photosensitizer in the target tumor tissue compartment. Hence, knowledge of the time-dependent content and contrast studies can directly deduced the optimal timing for PDT procedure. It was reported that PDT could induce apoptosis through different ways due to various photosensitizers and treated-cells. PDT has been widely used in treatment of solid neoplasm. However, no report about the effects of PDT on leukemic cells in vivo has been found. Taken in consideration that the limited tissue penetration of laser may hinder the anti-tumor efficacy of PDT, a great interest in the use of immunotherapy as adjuvant to PDT has rekindled. In the present study, a new amphipathic photosensitizer, the di-sulfonated di-phthalimidomethyl phthalocyanine zinc (ZnPcS2P2), was used. The data may provide a fundamental basis for the clinical application of ZnPc-PDT. The subjects of the thesis were focused on the following three aspects:1. The effects of ZnPc-PDT on normal hemotopoietic cells, K562 cells, high-tumorigenicity HL60 cells (hHL60 cells), and EL9611 cells.(1) Kinetic change of ZnPcS2P2 in normal bone marrow MNC, K562 cells, and hHL60 cells. Fluorescence intensity of cell extracts was measured with a fluoresence spectrophotometry.(2) The antiproliferative effects of ZnPc-PDT on K562 cells, hHL60 cells and normal hematopoietic cells. The proliferative potency of K562 cells and hHL60 cells was detected by MTT colorimetric assay, Typan blue dye exclusion assay, colony formation test. The proliferative potency of normal hematopoietic cells was evaluate... |
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