RESUMO
<p><b>OBJECTIVE</b>To improve the protocol of BALB/c 3T3 cell transformation assay, and apply it to the cocarcinogenesis study.</p><p><b>METHOD</b>Appropriate serum concentration, culture media and method of administration were selected by testing their effects on the growth and transformation of BALB/c 3T3 cells. The co-carcinogenic activity between diethylnitrosamine (DEN) and microcystin-LR (MC-LR) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were examined using the improved cell transformation assay. The malignant characteristics of transformed cells were verified by neoplasia in SCID mice.</p><p><b>RESULTS</b>There were strong co-carcinogenic activity between DEN and TCDD. On the contrary, although MC-LR has strong ability to induce cell transformation, the effect was markely inhibited by DEN. The transformed cells show some malignant characteristics.</p><p><b>CONCLUSION</b>The improved BALB/c 3T3 cell transformation assay is reliable and time-saving, and can be efficiently used in the study of cocarcinogenesis.</p>