merocyanine-dye and Melanoma

The efficiency of photodynamic effect (PDE) for Photofrin II (PfII), Verteporfin, and Merocyanine 540 (MC540) was compared against neoplastic cells. Triplet state lifetimes and singlet molecular oxygen quantum yields were correlated with biological effect. PfII triplet lifetime was two times longer than that of Verteporfin, however, its singlet molecular oxygen quantum yield was two times lower in comparison with Verteporfin. High singlet molecular oxygen quantum yield of Verteporfin resulted in high biological efficacy. To achieve 50% mortality of cells four times lower light dose and five times lower concentration of Verteporfin were applied in comparison with PfII. The same level of cell damage was reached using 10 times higher light dose and two times higher concentration of MC540 in comparison with PfII. Our results confirm that singlet molecular oxygen based mechanism, prevalent for Verteporfin and PfII, was highly effective against melanoma cells. Verteporfin can be used at small doses with high cellular damage efficiency.

Topics: Animals; Cell Line, Tumor; Cell Survival; Dihematoporphyrin Ether; Dose-Response Relationship, Radiation; Kinetics; Melanoma; Mice; Oxygen; Photochemotherapy; Photosensitizing Agents; Porphyrins; Pyrimidinones; Signal Transduction; Verteporfin

Induction of mitochondrial permeability transition (MPT) and cytosolic translocation of cytochrome C are considered essential components of the apoptotic pathway. Hence, there is the realization that mitochondrial-specific drugs could have potential for use as chemotherapeutic agents to trigger apoptosis in tumor cells. Recently, we showed that photoproducts of merocyanine 540 (pMC540) induced tumor cell apoptosis. In this study, we focused on identifying mitochondrial-specific compounds from pMC540 and studied their apoptotic potential. One purified fraction, C5, induced a drop in mitochondrial transmembrane potential and cytosolic translocation of cytochrome C in HL60 human leukemia cells. Moreover, the addition of C5 to purified rat liver mitochondria induced MPT as indicated by mitochondrial matrix swelling, which was completely inhibited by cyclosporin A, an inhibitor of the inner-membrane pore. Supernatant of C5-treated mitochondria showed a dose-dependent increase in cytochrome C, which was also inhibited in the presence of cyclosporin A, strongly indicating a direct effect on the inner-membrane pore. Despite the strong mitochondrial reactivity, C5 elicited minimal cytotoxicity (less than 25%) against HL60 leukemia and M14 melanoma cells because of inefficient caspase activation. However, prior exposure to C5 significantly enhanced the apoptotic response to etoposide or the CD95 receptor. Thus, we demonstrate that MPT induction and cytochrome C release by the novel compound C5, in the absence of effective caspase activation, is insufficient for triggering efficient apoptosis in tumor cells. However, when used in combination with known apoptosis inducers, such compounds could enhance the sensitivity of tumor cells to apoptosis. (Blood. 2000;95:1773-1780)

Topics: Animals; Antineoplastic Agents; Apoptosis; Biological Transport; Caspase Inhibitors; Caspases; Cyclosporine; Cytochrome c Group; Cytosol; Enzyme Activation; Enzyme Inhibitors; Etoposide; Fluorescence; HL-60 Cells; Humans; Intracellular Membranes; Melanoma; Mitochondria; Mitochondria, Liver; Neoplasm Proteins; Oligopeptides; Permeability; Photochemistry; Pyrimidinones; Radiation-Sensitizing Agents; Rats; Rats, Wistar; Signal Transduction; Skin Neoplasms; Staurosporine; Tumor Cells, Cultured

If the interplay between caspase proteases and mitochondria decide the fate of the cell during apoptosis, they may constitute useful molecular targets for novel drug design. We have shown that photoactivated merocyanine 540 (pMC540) triggers caspase-mediated apoptosis in HL60 leukemia and M14 melanoma cells. Because pMC540 is a mixture of photoproducts, we set out to purify the biologically active component(s) from this mixture and to investigate their ability to directly activate intracellular caspases and/or trigger mitochondrial events associated with apoptosis. Two photoproducts, namely C1 and C2, purified and characterized by mass spectroscopy and nuclear magnetic resonance (NMR) analysis, effectively induced apoptosis in HL60 and M14 cells. Interestingly, both C1 and C2 induced non-receptor-dependent activation of caspase 8, which was responsible for the downstream activation of caspase 3 and cell death. Both compounds induced the release of cytochrome C from mitochondria of tumor cells and from purified rat liver mitochondria; however, different mechanisms were operative in cytochrome C translocation in response to C1 or C2. C1-induced cytochrome C release was mediated by the mitochondrial permeability transition (MPT) pore and accompanied by a decrease in mitochondrial transmembrane potential (triangle uppsim), whereas cytochrome C release in response to C2 was independent of MPT pore opening. These findings do not exclude the possibility that changes in mitochondrial triangle uppsim are critical for apoptosis in some instances, but support the notion that this may not be a universal step in the apoptotic process. Thus, identification of two novel anticancer agents that directly activate effector components of the apoptotic pathway could have potential implications for the development of newer chemotherapeutic drugs.

Topics: Animals; Antineoplastic Agents; Apoptosis; Caspase 3; Caspase 8; Caspase 9; Caspases; Cytochrome c Group; Enzyme Activation; Humans; Leukemia, Promyelocytic, Acute; Melanoma; Membrane Potentials; Mitochondria; Mitochondria, Liver; Photochemistry; Pyrimidinones; Rats; Tumor Cells, Cultured

The molecular events involved in tumor cell death induced by novel photoproducts of merocyanine 540 (pMC540) are poorly understood. Using HL60 leukemia and M14 melanoma cell lines we investigated the role of the apoptotic pathway in pMC540-mediated cell death. Tumor cells exposed to pMC540 showed cell size shrinkage and an increase in the sub-diploid DNA content. A loss of membrane phospholipid asymmetry associated with apoptosis was induced by pMC540 in both tumor cell lines as evidenced by the externalization of phosphatidylserine. A dose-dependent increase in caspase-3 protease activity suppressed by the tetrapeptide inhibitor DEVD-CHO was observed in both cell lines. Western blot analysis of poly (ADP-ribose) polymerase, a caspase substrate, showed the classical cleavage pattern (116 to 89 kDa) associated with apoptosis in pMC540-treated cell lysates. Furthermore, caspase inhibition blocked the externalization of membrane PS, indicating that the loss of membrane phospholipid asymmetry is a downstream event of caspase activation. These findings demonstrate that tumor cell death induced by pMC540 is mediated by caspase proteases.

Topics: Apoptosis; Cell Size; Cysteine Endopeptidases; DNA, Neoplasm; Enzyme Activation; Humans; Leukemia; Melanoma; Phosphatidylserines; 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