Pterocarpans induce tumor cell death through persistent mitotic arrest during prometaphase.

Pterocarpans, a family of isoflavonoids found in the diverse Fabaceae, display potent cytotoxic activity over a panel of tumor cell lines, and among those tested, 2,3,9- trimethoxypterocarpan displays the most potent activity. This study evaluates the effects of 2,3,9-trimethoxypterocarpan and its related derivatives on cell cycle progression and microtubule function in select breast cancer cell lines (MCF7, T47d and HS578T). The pterocarpans, with the exception of 3,4-dihydroxy-9-methoxipterocarpan, induced increased frequencies of mitotic cells by inducing arrest in prometaphase. While microtubule organization in interphase cells was not modified during treatment, mitotic cells exhibited high frequencies of monastral spindles surrounded by condensed chromosomes. Immunofluorescence staining with an anti-γ-tubulin antibody showed double-dot labeling in the spindle polar region, suggesting that pterocarpan treatment blocked centrosome segregation. We found that this mitotic arrest was reversible when the cells were treated for up to 24 h followed by recovery in drug-free medium, but not after 48-h treatment followed by incubation in drug-free medium. In that case, treated cells typically underwent cell multinucleation and apoptosis.

Cytoskeleton alterations induced by Geodia corticostylifera depsipeptides in breast cancer cells.

Crude extracts of the marine sponge Geodia corticostylifera from Brazilian Coast have previously shown antibacterial, antifungal, cytotoxic, haemolytic and neurotoxic activities. The present work describes the isolation of the cyclic peptides geodiamolides A, B, H and I (1-4) from G. corticostylifera and their anti-proliferative effects against sea urchin eggs and human breast cancer cell lineages. Its structure-activity relationship is discussed as well. In an initial series of experiments these peptides inhibited the first cleavage of sea urchin eggs (Lytechinus variegatus). Duplication of nuclei without complete egg cell division indicated the mechanism of action might be related to microfilament disruption. Further studies showed that the geodiamolides have anti-proliferative activity against human breast cancer cell lines (T47D and MCF7). Using fluorescence techniques and confocal microscopy, we found evidence that the geodiamolides A, B, H and I act by disorganizing actin filaments of T47D and MCF7 cancer cells, in a way similar to other depsipeptides (such as jaspamide 5 and dolastatins), keeping the normal microtubule organization. Normal cells lines (primary culture human fibroblasts and BRL3A rat liver epithelial cells) were not affected by the treatment as tumor cells were, thus indicating the biomedical potential of these compounds.

Cytotoxicity in the marine dinoflagellate Prorocentrum mexicanum from Brazil.

The microscopic algae in the oceans are crucial food for filter feeding bivalve shellfish (oysters, mussels, scallops, clams, etc.) as well as for the larvae of commercially important crustaceans. Some species of microalgae have the capacity to produce potent toxins, such as saxitoxins and ciguatoxins, which may intoxicate humans. Among the marine phytoplankton, the dinoflagellates are the main toxin producers. Studies on the marine phytoplankton from the São Sebastião Channel, southeastern coast of Brazil, showed a great diversity of dinoflagellates. Some species were collected and cultured at the Marine Biology Center of the São Paulo University (USP). The polar (PEs) (aqueous) and apolar (AEs) (methylene chloride) extracts of the cultivated dinoflagellate species were tested on different stages of the sea urchin development, on mouse erythrocytes and on microfilaments organization in a neuroblastoma cell line. Prorocentrum mexicanum PE and AE induced cells anomalies and cell division inhibition of sea urchin eggs at EC50 of 78.75 microg/mL (95% CI from 32.56 to 190.50) and 22.50 microg/mL (95% CI from 2.96 to 170.80) respectively (n=3). Both AE and PE of P. mexicanum induced hemolysis with EC50 of 65.07 microg/mL (95% CI from 27.40 to 154.60) and 84.29 microg/mL (95% CI from 53.26 to 133.40 microg/mL), respectively. P. mexicanum PE was tested in immunofluorescence for actin filaments organization in neuroblastoma cultured cell.

Cytotoxicity in the marine dinoflagellate Prorocentrum mexicanum from Brazil

The microscopic algae in the oceans are crucial food for filter feeding bivalve shellfish (oysters, mussels, scallops, clams, etc.) as well as for the larvae of commercially important crustaceans. Some species of microalgae have the capacity to produce potent toxins, such as saxitoxins and ciguatoxins, which may intoxicate humans. Among the marine phytoplankton, the dinoflagellates are the main toxin producers. Studies on the marine phytoplankton from the São Sebastião Channel, southeastern coast of Brazil, showed a great diversity of dinoflagellates. Some species were collected and cultured at the Marine Biology Center of the São Paulo University (USP). The polar (PEs) (aqueous) and apolar (AEs) (methylene chloride) extracts of the cultivated dinoflagellate species were tested on different stages of the sea urchin development, on mouse erythrocytes and on microfilaments organization in a neuroblastoma cell line. Prorocentrum mexicanum PE and AE induced cells anomalies and cell division inhibition of sea urchin eggs at EC50 of 78.75 μg/mL (95% CI from 32.56 to 190.50) and 22.50 μg/mL (95% CI from 2.96 to 170.80) respectively (n = 3). Both AE and PE of P. mexicanum induced hemolysis with EC50 of 65.07 μg/mL (95% CI from 27.40 to 154.60) and 84.29 μg/mL (95% CI from 53.26 to 133.40 μg/mL), respectively. P. mexicanum PE was tested in immunofluorescence for actin filaments organization in neuroblastoma cultured cell.

Cytoskeleton alterations induced by Geodia corticostylifera depsipeptides in breast cancer cells

Crude extracts of the marine sponge Geodia corticostylifera from Brazilian Coast have previously shown antibacterial, antifungal, cytotoxic, haemolytic and neurotoxic activities. The present work describes the isolation of the cyclic peptides geodiamolides A, B, H and I (1–4) from G. corticostylifera and their anti-proliferative effects against sea urchin eggs and human breast cancer cell lineages. Its structure–activity relationship is discussed as well. In an initial series of experiments these peptides inhibited the first cleavage of sea urchin eggs (Lytechinus variegatus). Duplication of nuclei without complete egg cell division indicated the mechanism of action might be related to microfilament disruption. Further studies showed that the geodiamolides have anti-proliferative activity against human breast cancer cell lines (T47D and MCF7). Using fluorescence techniques and confocal microscopy, we found evidence that the geodiamolides A, B, H and I act by disorganizing actin filaments of T47D and MCF7 cancer cells, in a way similar to other depsipeptides (such as jaspamide 5 and dolastatins), keeping the normal microtubule organization. Normal cells lines (primary culture human fibroblasts and BRL3A rat liver epithelial cells) were not affected by the treatment as tumor cells were, thus indicating the biomedical potential of these compounds.