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Radiation therapy is one of the most important approaches to cancer therapy, but radiotoxicity to normal tissue is a serious limitation of this treatment. Compounds which are able to either sensitize cancer cells or protect normal cells to radiation are of great interest. The cytotoxicity of holotoxin A1 and the effects of radiation against DLD-1 and HT-29 cells were measured by MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. The effect of the combination of holotoxin A1 with X-ray on colony formation of cancer cells was determined by the soft agar assay. The effect of holotoxin A1 on the recovery of peripheral blood leukocyte number, mass, and cellularity of the lymphoid organs of irradiated mice, as well as on growth of murine Ehrlich solid carcinoma was studied. Holotoxin A1 enhanced the sensitivity of colorectal carcinoma cells to radiation in vitro. Injection of holotoxin A1 to mice led to an increase in the spleen endogenous colony number and peripheral blood leukocyte number, as well as the weight and cellularity of the lymphoid organs of the irradiated mice. Holotoxin A1 in combination with X-ray radiation effectively inhibited the growth of Ehrlich solid carcinoma in vivo. Holotoxin A1 is suggested to be a promising agent for improving the efficiency of radiotherapy.

The action of seven polyhydroxylated sterol mono-and disulfates (1-7), isolated from ophiuroids, on innate and adaptive immunity was examined in in vitro and in vivo experiments. At least, three of them (1, 2 and 4) increased the functional activities of neutrophils, including levels of oxygen-dependent metabolism, adhesive and phagocytic properties, and induced the expression of pro-inflammatory cytokines TNF- and IL-8. Compound 4 was the most active for enhancing the production of antibody forming cells in the mouse spleen.

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