pyrimidinones and Leukemia--Erythroblastic--Acute

Carboplatin (CBDCA) and the pyrimidine aglycone divicine displayed cytotoxic effects of murine erythroleukemic cells (MELC), with ID50 values of 158 and 37 microM, respectively. Combination of CBDCA and divicine, at a 2:1 ratio, increased cytotoxicity considerably. Under specific conditions of time schedule of administration, the association of CBDCA and divicine resulted in a clear synergistic activity. Alkaline elution studies on both unirradiated and gamma-irradiated MELC demonstrated opposite patterns of DNA damage with the two molecules. Thus, CBDCA elicited DNA interstrand crosslinks (ISC), while divicine resulted in DNA single strand breaks (SSB). Association of both molecules led in the unirradiated cells to a higher SSB frequency than recorded with divicine alone. Accordingly, intracellular activation of CDBCA by redox cycling of divicine seems not to be involved. Rather, intracellular platinum appears to enhance cytotoxicity of divicine.

Topics: Animals; Antineoplastic Agents; Carboplatin; Cell Line; Cell Survival; DNA Damage; DNA, Neoplasm; Dose-Response Relationship, Drug; Drug Synergism; Gamma Rays; Kinetics; Leukemia, Erythroblastic, Acute; Mice; Pyrimidinones; Tumor Cells, Cultured

Many new photosensitizers and laser wavelengths are being tested to improve photodynamic therapy by enhancing specific tumor uptake and/or retention, lowering systemic toxicity, and increasing laser tissue penetration. In this study the potential synergistic effects of rhodamine-123 (Rh-123) and merocyanine-540 (MC-540) sensitization of human tumor cell lines after laser exposure were explored. In a first series of experiments, the kinetics of uptake of Rh-123 and M-540 were tested on three human leukemia cell lines (K562, RAJI, 729HF2), P3 squamous carcinoma, and M26 melanoma. Our results demonstrate a clear difference in the rate and amount of uptake of MC-540 (K562 > P3 > RAJI > 729HF2 > M26) and Rh-123 (P3 > RAJI > 729HF2 > K562 > M26) by these cell lines. In a second series of experiments, M26 tumor cells were sensitized with either Rh-123 (1 microgram/ml) or with MC-540 (20 micrograms/ml) alone or with a combination of the two dyes for 60 minutes, then exposed to the argon (514.5 nm) laser at nonthermal energy levels. Our results demonstrate a significant enhancement of the tumoricidal effects of the laser on M26 carcinoma cells after sensitization with both dyes together (MC-540 and Rh-123) when compared to each dye alone. As with combination antibiotherapy, the synergistic effects of two laser dyes that have different intracellular targeting sites appear to enhance tumoricidal effects significantly after exposure to a matching laser wavelength. The data provide evidence for effective laser phototherapy by dye synergy.

Topics: Antimetabolites, Antineoplastic; Burkitt Lymphoma; Carcinoma, Squamous Cell; Cell Survival; Drug Synergism; Fluorescent Dyes; Hot Temperature; Humans; Laser Therapy; Leukemia, B-Cell; Leukemia, Erythroblastic, Acute; Lung Neoplasms; Melanoma; Neoplasms; Photochemotherapy; Photosensitizing Agents; Pyrimidinones; Radiation Dosage; Rhodamine 123; Rhodamines; Tumor Cells, Cultured

The Friend virus complex was used as a model to study the effects of merocyanine 540 (MC 540)-mediated photosensitization on enveloped viruses. Simultaneous exposure to the lipophilic dye MC 540 and white light inactivated cell-free virus, cell-associated virus, and virus-transformed cells. When used under experimental conditions that are known to preserve most mature blood cells, at least some coagulation factors, and a significant portion of the pluripotent hematopoietic stem cell compartment, MC 540-mediated photosensitization reduced virus titers by greater than or equal to 4 log and the concentration of in vitro clonogenic erythroleukemia cells by greater than or equal to 5 log. Animals that received a single intravenous injection of photosensitized virus were resistant to a subsequent challenge with live virus. High sensitivity to MC 540-mediated photosensitization appears to be a property that is shared by other enveloped viruses. Thus, photosensitization mediated by MC 540 may be of benefit in the sterilization of blood products (in particular, cellular products), the production of vaccines, and selected areas of antiviral therapy.

Topics: Animals; Antiviral Agents; Cell Line, Transformed; Cell Transformation, Viral; Cell-Free System; Drug Resistance, Microbial; Female; Friend murine leukemia virus; Kinetics; Leukemia, Erythroblastic, Acute; Mice; Mice, Inbred DBA; Pyrimidinones; Radiation-Sensitizing Agents; Virion

When human erythroleukemic cells are induced to differentiate in vitro, the lipids in the plasma membrane that bind the fluorescent dye merocyanine 540 are redistributed into a cap at one pole of the cell. This capping phenomenon can also be observed in uninduced cells that have been incubated with cytochalasin B, an agent which disrupts actin-containing microfilaments or with local anesthetics which act on both microfilaments and microtubules. Colchicine which acts on microtubules, however, has no effect. This suggests that the uniform distribution seen in uninduced cells is maintained by the cytoskeletal microfilaments and that loss of these structures leads to spontaneous redistribution of merocyanine 540-binding sites.

Topics: Benzoxazoles; Binding Sites; Cell Line; Cell Membrane; Humans; Kinetics; Leukemia, Erythroblastic, Acute; Pyrimidinones

Topics: Animals; Cell Differentiation; Cell Nucleus; Cells, Cultured; Erythrocyte Membrane; Erythrocytes; Erythropoiesis; Lectins; Leukemia, Erythroblastic, Acute; Leukemia, Experimental; Mice; Pyrimidinones; Receptors, Concanavalin A; Receptors, Drug; Receptors, Mitogen; Spleen; Surface Properties

Transformed murine hematopoietic cells of several lineages bound the fluorescent membrane probe merocyanine 540, whereas their normal counterparts did not. Similar selective binding was reproduced in artificial liposomes which bound this probe above their phase transition temperature, but not below it. The regions of the membrane to which merocyanine 540 binds along with the receptors for the lectin concanavalin A, but not the receptors for the lectin wheat germ agglutinin, were rearranged during the course of induced differentiation of erythroleukemia cells. Based on these findings, we propose a model of hematopoietic cell surface differentiation in which proteins such as concanavalin A receptors, which are destined for removal from the plasma membrane, are specifically associated with disordered, liquid-like lipid domains which can be visualized with merocyanine 540. For the specific case of erythroid differentiation, these domains and their associated proteins are collected at the region of the membrane where nuclear extrusion occurs and are eliminated from the reticulocyte plasma membrane by the enucleation event.

Topics: Animals; Cell Line, Transformed; Cell Membrane; Hematopoiesis; Hematopoietic System; Leukemia, Erythroblastic, Acute; Liposomes; Membrane Fluidity; Mice; Pyrimidinones; Receptors, Concanavalin A; Receptors, Mitogen

Normal erythroid cells and both uninduced and induced erythroleukemia cells were stained with the leukemia-specific fluorescent probe merocyanine 540 and its analogs. The external membranes of normal intact cells bound the dye, but this general low-affinity binding was completely abolished by the addition of competing serum. In contrast, erythroleukemia cells bound the dye even in the presence of serum; binding was not affected by reversing the sign of the charge carried by MC540, but was abolished upon removal of certain hydrophobic side chains. When the erythroleukemia cells were induced to differentiate, the distribution of dye-binding regions was altered by the cell such that staining became localized to one region of the membrane. Concomitantly, conconavalin A binding sites were redistributed and became localized in the same region of the membrane as the merocyanine binding sites. Merocyanine 540 is thus shown to bind to a hematopoietic surface feature whose topological distribution is subject to cellular control during differentiation. This leukemia-specific marker may be one of several eliminated during enucleation of mammalian erythroid cells.

Topics: Animals; Benzoxazoles; Cell Line; Chickens; Dimethyl Sulfoxide; Erythrocyte Membrane; Erythrocytes; Erythropoiesis; Female; Fluorescent Dyes; Leukemia, Erythroblastic, Acute; Mice; Pyrimidinones; Receptors, Concanavalin A; Staining and Labeling; Structure-Activity Relationship