Promoting activity of microcystins extracted from waterblooms in SHE cell transformation assay

Microcystis aeruginosa is the dominant algae in most of the eutrophicated lakes in China. It can produce cyclic heptapeptides, known as microcystins, which can cause liver damage in wild and domestic animals. In this paper, a two-stage transformation assay for demonstrating the carcinogenic effects of the algal toxins is reported. The cell strain used in this assay was derived from embryos of Syrian golden hamster and the algal toxins were extracted from Microcystis aeruginosa, termed microcystis raw toxin (MRT). To elucidate its promoting activity, the target cells were first exposed to a low dosage of 3-methylcholanthrene (MCA) and then to MRT. The results showed that MRT significantly enhanced the MCA initiated cell transformation, and a dose-response relationship was observed, but it failed to induce transformation of SHE cells not pretreated by MCA. These results suggest that the MRT play an important role in the malignant transformation of SHE cells. MRT may thus be a tumor promoter, and this transformation assay with SHE cells may be used to predict tumor prompting activity of environmental chemicals, before long-term in vivo two-stage carcinogenesis experiments are carried out.