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Actinoporins are the most abundant group of sea anemone cytolytic toxins. Their membranolytic activity is of high interest for the development of novel anticancer drugs. However, to date the activity of actinoporins in malignant cells has been poorly studied. Here, we report on recombinant analog of Hct-S3 (rHct-S3), belonging to the combinatory library of Heteractis crispa actinoporins. rHct-S3 exhibited cytotoxic activity against breast MDA-MB-231 (IC50 = 7.3 µM), colorectal HT-29 (IC50 = 6.8 µM), and melanoma SK-MEL-28 (IC50 = 8.3 µM) cancer cells. The actinoporin effectively prevented epidermal growth factor -induced neoplastic transformation of JB6 Cl41 cells by 34% ± 0.2 and decreased colony formation of HT-29 cells by 47% ± 0.9, MDA-MB-231 cells by 37% ± 1.2, and SK-MEL-28 cells by 34% ± 3.6. Moreover, rHct-S3 decreased proliferation and suppressed migration of colorectal carcinoma cells by 31% ± 5.0 and 99% ± 6.4, respectively. The potent anti-migratory activity was proposed to mediate by decreased matrix metalloproteinases-2 and -9 expression. In addition, rHct-S3 induced programmed cell death by cleavage of caspase-3 and poly (ADP-ribose) polymerase, as well as regulation of Bax and Bcl-2. Our results indicate rHct-S3 to be a promising anticancer drug with a high anti-migratory potential.

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The effects of temperature and pH on the spatial structure of carcinoembryonic antigen (CEA) and its various derivatives are studied by circular dichroic spectroscopy and differential UV spectroscopy. The spatial organization of the protein portion of CEA and its derivatives as revealed by spectroscopic evidence is discussed with respect to the antigenic activity of the species studied. We conclude that the protein portion of CEA consists mainly of a β-structural type. Using the various modifications of the sugar moiety and the protein portion, antigenic determinants of CEA are shown to possess the main conformational character of the molecule while participation of the sugars in the formation and orientation of the carbohydrate chains relative to the protein core of the antigen appear to be important.

Effects of temperature and pH on the spatial structures of trophoblast-specific β₁ -glycoprotein (TSG) and its various derivatives and fragments have been studied by circular dichroic spectroscopy. The spatial organization of the protein portion of TSG derivatives, as revealed by the spectroscopic evidence, has been discussed with respect to the antigenic activity of the species studied. We concluded that the TSG protein portion consists mainly of a β-structural type. The antigenic determinants were shown to be topographic, and are preferentially localized in the protein portion; only about 15 % of the TSG antigenic activity failed to bear a direct relation to the spatial structure. The antigenic determinants seemed to include a tryptophan residue.