manumycin and hypericin

Natural compounds originated from plants and microorganisms and their combinations are currently being investigated as a possible treatment for several diseases including cancer. Hypericin (photodynamically-active pigment from Hypericum perforatum L.) and manumycin A (inhibitor of farnesyltransferase from Streptomyces parvulus) belong to the chemicals potentially applicable in clinical practice. In this study we evaluated potential cytotoxic (via trypan blue exclusion test), genotoxic (via DNA-topology and comet assays), and mutagenic effects (via bacterial reverse mutation test) of these compounds and their combinations considering the molecular mechanism of their action in cell-free and cellular systems. Our results did not reveal neither cytotoxic nor mutagenic activities of tested compounds and their combinations. Regarding the genotoxic potential, no damage of plasmid DNA in cell-free system was detected. On the other hand, photoactivated hypericin and manumycin A were able to induce primary DNA damage in human lymphocytes analyzed by comet assay. The possible antagonistic interactions between these two metabolites were estimated using SynergyFinder software analysis and experimental data obtained from comet assay. Our findings indicate that not only the presence of substances, but also their ratio plays an important role in resulting effects of the combined treatment in cellular system.

Topics: Antineoplastic Agents; Comet Assay; DNA Damage; Humans; Mutagenicity Tests; Mutagens

The use of natural products as chemotherapeutic agents and tools for manipulation of apoptosis represent an attractive therapeutic concept. In this study, we investigated the anticancer activities of a combination of two natural compounds with different origin, hypericin (plant product) in its photoactive state and Manumycin A (yeast product) and explored the underlying mechanisms of their pro-apoptotic action using an oxaliplatin-resistant variant of human colon adenocarcinoma cell line HT-29-OxR as the experimental model. CCK-8 assay was performed to evaluate the cytotoxicity of the drugs. CalcuSyn software was used to identify the type of interaction between the two agents. BrdU incorporation assay and colony forming assay were performed to study the short- and long-term proliferation of cells. To evaluate the ability of the drug combination to induce apoptosis, PARP p85 fragment was detected using the ELISA method. Changes in apoptosis-related proteins were examined by immunoassays. Our results showed that a synergistic combination of photoactive hypericin and Manumycin A decreased viability, inhibited both short- and long-term cell proliferation, decreased levels of IAPs proteins (cIAP1, cIAP2, XIAP and survivin), induced an apoptotic PARP cleavage associated with decline in procaspase-3 level, promoted phagocytosis of cancer cells, and restored chemosensitivity to oxaliplatin.

Topics: Anthracenes; Antineoplastic Agents; Apoptosis Regulatory Proteins; Cell Line; Cell Proliferation; Cell Survival; Colorectal Neoplasms; Drug Resistance, Neoplasm; Drug Synergism; Humans; Light; Macrophages; Oxaliplatin; Perylene; Phagocytosis; Polyenes; Polyunsaturated Alkamides

Several photodynamically-active substances and farnesyltransferase inhibitors are currently being investigated as promising anticancer drugs. In this study, the combined effect of hypericin (the photodynamically-active pigment from Hypericum perforatum) and selective farnesyltransferase inhibitor manumycin (manumycin A; the selective farnesyltransferase inhibitor from Streptomyces parvulus) on HT-29 adenocarcinoma cells was examined. We found that the combination treatment of cells with photoactivated hypericin and manumycin resulted in enhanced antiproliferative and apoptotic response compared to the effect of single treatments. This was associated with increased suppression of clonogenic growth, S phase cell cycle arrest, elevated caspase-3/7 activity and time-dependent total cleavage of procaspase-3 and lamin B, cleavage of p21Bax into p18Bax and massive PARP cleavage. Moreover, we found that the apoptosis-inducing factor is implicated in signaling events triggered by photoactivated hypericin. Our results showed the relocalization of apoptosis-inducing factor (AIF) to the nuclei after hypericin treatment. In addition, we discovered that not only manumycin but also photoactivated hypericin induced the reduction of total Ras protein level. Manumycin decreased the amount of farnesylated Ras, and the combination treatment decreased the amount of both farnesylated and non-farnesylated Ras protein more dramatically. The present findings indicate that the inhibition of Ras processing may be the determining factor for enhancing the antiproliferative and apoptotic effects of combination treatment on HT-29 cells.

Topics: Adenocarcinoma; Anthracenes; Antineoplastic Agents; Apoptosis; bcl-2-Associated X Protein; Caspase 3; Caspase 7; Cell Proliferation; Enzyme Inhibitors; HT29 Cells; Humans; Lamin Type B; Perylene; Poly(ADP-ribose) Polymerases; Polyenes; Polyunsaturated Alkamides; Radiation-Sensitizing Agents; ras Proteins