Tumor necrosis factor(TNF) has been considered as an important candidate for cancer gene therapy based on it9 potent anti-tumor activity. However, since the efficiency of current techniques of gene transfer is not satisfactory, the majorities of current protocols is aiming the in vitro gene transfer to cancer cells and re-introducing genetically modified cancer cells to host In previous study, it was shown that TNF-sensitive cancer cells transfected with TNF-α CDNA would become highly resistant to TNF. Understanding the mechanisms of TNF-resistance in TNF-α gene transfected cancer cells would be an important step for improving the efficacy of cancer gene therapy as we]1 as for better understandings of tumor biology. This study was designed to evaluate the role of new protective protein synthesis in the acquired resistance to TNF of TNF-α gene transfected cancer cells.

We transfected TNF-α c-DNA to WEHI l64, a murine fibrosarcoma cell line, using retroviral vector (pLT12SN(TNF)) and confirm the expression of TNF with PCRf ELISA, MTT assay. Then we determined the TNF resistance of TNF gene transfected cells(WEHI 164-TNF) and the changes of TNF sensitivities after treatments with actinomycin D(transcription inhibitor) and cycloheximide(translation inhibitor).

WEHI 164 which was sensitive to TNF became resistant to TNF after being trsnsfected with TNF-α gene and the resistance to TNF was partially reversed after treatment with actinomycin D, but not with cycloheximide.

The acquired resistance to TNF after TNF-α gene transfection may be associated with synthesis of some protective proteins.