Abstract: BACKGROUND ＆ AIM： Translation elongation factor TEF-1δ (Genbank Accession Number AF304351) was identified as a novel cadmium - responsive proto-oncogene. The objective of this research is to determine if antisense TEF-1δ reverses the oncogenic potential of Cd-transformed BALB/c-3T3 cells. MATERIAL AND METHODS： We first established stable expression system of CdCl2-transformed BALB/c-3T3 cells with the expression vector containing TEF-1δ cDNA in the antisense orientation using calcium phosphate and G418 selection protocols. Then the reversal of the oncogenic potential of these cells was tested by soft agar and nude mouse tumorigenicity assay. RESULTS: The results demonstrated that expression of the antisense TEF-1δ in the CdCl2-transformed BALB/c-3T3 cells resulted in reversal of the transformed phenotype of cells. This was evidenced by a 28 ％～44 ％ decrease in the number of anchorage-independent colonies growing on soft agar and the significant reduced tumorigenic potential of cells in nude mice compared with the corresponding controls. In addition to a significant delay in the onset of appearance of tumors, a significant reduction in size and a 54 ％～58 ％ decrease in weight of the tumors were also observed in mice injected with the TEF-1δ antisense expressing cells compared with the corresponding controls. CONCLUSION: These results indicate that antisense TEF-1δ mRNA expression reverses its oncogenic potential and targeting TEF-1δ expression through its antisense may have therapeutic value for cancer induced by cadmium. 　　

Key words: cadmium chloride (CdCl2), antisense TEF-1δ, reversal, carcinogenicity