Radioiodine therapy of colon cancer following tissue-specific sodium iodide symporter gene transfer.

We investigated the feasibility of using radioiodine therapy in colon carcinoma cells (HCT 116) following tumor-specific expression of the human sodium iodide symporter (hNIS) using the carcinoembryonic antigen (CEA) promoter. HCT 116 cells were stably transfected with an expression vector, in which hNIS cDNA has been coupled to a CEA promoter fragment. This promoter is responsible for tissue-specific expression of CEA in gastrointestinal tract epithelium, and has been shown to target therapeutic genes to colorectal cancer cells. Functional NIS expression was confirmed by iodide uptake assay, Western blot analysis, immunostaining and in vitro clonogenic assay. The stably transfected HCT 116 cells concentrated (125)I about 10-fold in vitro without evidence of iodide organification. In contrast, transfection of control cancer cells without CEA expression did not result in iodide accumulation. Western blot analysis using a hNIS-specific antibody revealed a band of approximately 90 kDa. In addition, immunostaining of stably transfected HCT 116 cells revealed hNIS-specific membrane-associated immunoreactivity. In an in vitro clonogenic assay approximately 95% of stably transfected HCT 116 cells were killed by exposure to (131)I, while only about 5% of NIS-negative control cells were killed. Further, using an adenovirus carrying the NIS gene linked to the CEA promoter, high levels of tumor-specific radioiodide accumulation were induced in HCT 116 cells. In conclusion, a therapeutic effect of (131)I has been demonstrated in colon carcinoma cells following induction of tumor-specific iodide uptake activity by CEA promoter-directed NIS expression in vitro. This study demonstrates the potential of NIS as a therapeutic gene allowing radioiodine therapy of colon cancer following tumor-specific NIS gene transfer.

Bispecific single-chain antibodies as effective tools for eliminating epithelial cancer cells from human stem cell preparations by redirected cell cytotoxicity.

High-dose chemotherapy (HDC) with autologous bone marrow or peripheral stem cell transplantation is discussed as one option to treat the extensive stage of a variety of tumors. Effective methods to eliminate contaminating tumor cells from human bone marrow or stem cell grafts may improve the outcome of the patients. We investigated 3 recombinant bispecific single-chain antibodies (bscAbs) directed against 17-1A (EpCAM), c-erbB-2 (HER-2/neu) and LeY on the one and CD3 on the other binding site for their ability to induce lysis of epithelial tumor cells by retargeting autochthonous T lymphocytes present in bone marrow mononuclear cells (BMMC) and in peripheral stem cell mononuclear cells (PSMC). The bscAbs showed remarkable specific lysis of different epithelial tumor cell lines with BMMCs as well as with PSMCs as effector cells. Investigation of the alpha 17-1A-alpha CD3 bscAb revealed a significant correlation between the percentage of CD3(+) cells present in the BMMCs and the rate of lysis as well as the absence of detrimental effects on the viability of hematopoietic progenitor cells as determined by colony-forming unit assays (CFUs). Our results indicate that recombinant bispecific single-chain antibodies could be new tools for purging of human bone marrow and peripheral stem cell grafts from contaminating epithelial cancer cells for patients receiving autologous stem cell transplantation after HDC.