Apoptotic activity of the marine diatom Cocconeis scutellum and eicosapentaenoic acid in BT20 cells.

CONTEXT: The marine diatoms Cocconeis scutellum Ehrenberg (Bacillariophyceae) are known to trigger apoptosis in the androgenic gland of the Mediterranean crustacean Hippolyte inermis Leach (Decapoda), affecting the shrimp's sex reversal. OBJECTIVE: The aim of this study was to evaluate a possible apoptotic effect of extracts and fractions from these microalgae also on human tissues. MATERIALS AND METHODS: The chemical profile of C. scutellum was determined by gas chromatography-mass spectrometry (GC-MS) and, afterwards, organic extracts and fractions from the diatoms were used to treat to breast cancer BT20 cells. Double labeling with annexin V-FITC and isotonic propidium iodide (PI) along with flow cytometry analysis enabled the evaluate of cell apoptosis and viability, whereas hypotonic PI staining was used to analyze the cell cycle in BT20 lines. The involvement of specific caspases was studied by Western blotting. RESULTS: Results demonstrated that the diethyl ether extract and, in particular, fraction 3, the richest fraction in eicosapentaenoic acid (EPA) from the diethyl ether extract, selectively induced apoptosis (up to 89.2% at 1 µg/well of fraction 3) and decreased viability in BT20 cells. The apoptotic effect was displayed in a concentration and time-dependent manner, by activating caspases-8 and 3, and arresting the progression of the cell cycle from S to G2-M phase. EPA alone showed similar apoptotic effects in BT20 cells. DISCUSSION AND CONCLUSION: The study demonstrates the apoptotic activity of C. scutellum diatoms on breast cancer cells and suggests their potential use as a source of apoptotic compounds.

CULTURE CONDITIONS INFLUENCE THE GROWTH DYNAMICS AND THE PRODUCTION OF COCCONEIS SCUTELLUM (BACILLARIOPHYTA)(1).

The optimal conditions for the growth of two conspecific benthic diatoms were defined through factorial experimentation. We investigated the roles of light spectrum, nutrient availability, and culture conditions on the laboratory production of Cocconeis scutellum scutellum Ehrenb. and C. scutellum parva Grunow. Diatoms were cultivated in petri dishes, and inverted optical microscopy was used to periodically record their abundance. Growth curves were constructed from these data for each culture condition. In addition, at the end of the experiment we performed weight measurements to determine the total production for each of the considered conditions. We found that cultivation in nonsealed (NS) petri dishes (permitting gas exchange) represented the most productive technique. Cell density and biomass varied among light spectra, although this effect was inconsistent. For example, the Sylvania Gro-Lux lamp (GL) produced the lowest cell density but highest biomass, suggesting that it may promote the production of larger cells. Surprisingly, of the culture media tested, f/2 (a media commonly used for the culture of diatoms) was the least productive. Diatom density and biomass were variably dependent on the combination of experimental culture conditions and strain used. These physical and chemical factors act mainly on given features of the diatom growth curve. These results permitted us to devise adequate culture protocols, to produce a biotechnologically important substance: a proapoptotic compound that specifically destroys the androgenic gland of a shrimp and could find novel applications in human medicine.