Ribozyme to TGF-beta1 mRNA abrogates immunosuppressive effects of human colorectal adenocarcinoma HRT-18 cells in vitro and in vivo.

Transforming growth factor-beta1 (TGF-beta1) is overexpressed in a variety of malignant epithelial tumors and was suggested to be a marker of colorectal cancer. Moreover, there is growing evidence that TGF-beta1 contributes to tumor progression by regulating tumor cell proliferation and differentiation, inducing a favorable tumor microenvironment, promoting migration and invasion, and suppressing macrophage cytotoxicity. Therefore, we stably transfected an anti-TGF-beta1 hammerhead ribozyme into the human colorectal adenocarcinoma cell line HRT-18. Expression of this ribozyme resulted in significant inhibition of TGF-beta1 expression on mRNA and protein level. This was associated with an enhanced tumor cell differentiation and a reduced tumor growth in vivo. The capability of tumor cells to suppress ROI production of co-cultivated human macrophages was abrogated in transfectants. Taken together, inhibition of TGF-beta1 in colorectal carcinoma cells might be an interesting therapeutic tool leading to reduced tumor cell growth and increased macrophage cytotoxicity. Thus, a gene-therapeutic approach using anti-TGF-beta1 ribozyme in combination with established anti-tumor agents is of great promise.