Antisense oligonucleotide specific for transforming growth factor-beta 1 inhibit both in vitro and in vivo growth of MBT-2 murine bladder cancer.

INTRODUCTION AND OBJECTIVES

TGF-beta is a potent immunosuppressive cytokine produced by many tumor cells. Secretion of TGF-beta by malignant cells may be a mechanism by which tumor cells escape destruction by tumor-specific T lymphocytes. In this study, we used a TGF-beta producing C3H/He-MBT-2 murine bladder tumor model to investigate the feasibility of antisense oligonucleotide (ODN) gene therapy strategy to block the production of TGF-beta from tumor cells and evaluate its influence on both in vitro tumor growth and in vivo tumor formation.

MATERIALS AND METHODS

Using a plasmid, pRUFCD, we constructed a recombinant plasmid pRUFCD/TGF-beta 1(-) containing antisense TGF-beta ODN and then transfected in into MBT-2 cells by electroporation. Three transfectant clones were successfully obtained by their resistance to 5-fluorouracil and cytosine.

RESULTS

The secretion of TGF-beta from the three obtained TGF-beta antisense-blocked MBT-2 cell clones, as assessed by ELISA, were all decreased. Moreover, they all exhibited smaller colony size in the in vitro anchorage-independent soft agar colony forming assay. Tumor growths in mice injected with these three clones were all inhibited compared with those injected with parental tumor cells.

CONCLUSION

This study demonstrates that after reducing the secretion of TGF-beta 1 on tumor cells by TGF-beta 1 antisense, ODN can inhibit their in vitro growth and in vivo tumor formation suggesting that this approach can be a potentially useful strategy to abolish the adverse immunosuppression effect of TGF-beta 1 producing autologous tumor vaccine and therefore to enhance host antitumor immune response.