Human carcinoembryonic antigen cDNA expressed in rat carcinoma cells can function as target antigen for tumor localization of antibodies in nude rats and as rejection antigen in syngeneic rats

Abstract

We have tried to develop a new model consisting of rats transplanted with syngeneic colon carcinoma PROb cells transfected with cDNA coding for the carcinoembryonic antigen (CEA), the human tumor marker most commonly used as target for MAbs. The antigenic density of the 4 CEA-expressing clones selected for a precise characterization ranged from 5 x 10(4) to 1 x 10(6) CEA molecules per cell. In all clones the CEA was shown to be attached to the membrane by a phosphatidylinositol (PI) anchor. Using a panel of radiolabeled MAbs directed against the 5 major epitopes described on the CEA molecule, we showed that all these CEA epitopes were expressed by the 4 transfectants. Southern-blot analysis showed that the entire CEA cDNA was present in the transfectants. Western-blot analysis, however, showed that the size of the CEA expressed by the 4 transfectants was slightly smaller than that of CEA produced by 2 reference human colon-carcinoma cell lines. Two clones, expressing 1 x 10(5) and 1 x 10(6) CEA molecules per cell, respectively, were grafted s.c. in nude mice and rats. Injection of radiolabeled anti-CEA F(ab')2 fragments into these animals showed specific tumor localization with the highest percentages of injected doses for the transfectants expressing the highest CEA level. When grafted into immunocompetent syngeneic BDIX rats, the CEA-expressing clones induced a strong antibody response against CEA and tumor rejections in a majority of the animals. Although the analysis of the immune response against the CEA-cDNA-transfected carcinoma cells is under investigation, the present results demonstrate that human CEA could function as a rejection antigen when transfected into rat carcinoma cells.

Internalisation enhances photo-induced cytotoxicity of monoclonal antibody-phthalocyanine conjugates

“…The human ovarian carcinoma cell line, SKOv3, purchased from the American Type Culture Collection (HTB-77, Rockville, MD, USA), was maintained according to recommended procedures. The SKOv3 cells were transfected with pRc/CMV/CEA-cDNA (Pèlegrin et al, 1992) using a mammalian transfection kit (Stratagene, La Jolla, CA, USA). Three µg of DNA were precipitated with calcium phosphate according to the manufacturer's instructions and incubated for 16 h with about 3 × 10 6 nonconfluent adherent carcinoma cells.…”

Involvement of circulating CEA in liver metastases from colorectal cancers re-examined in a new experimental model

“…CO115 cells were transfected with pRc/CMV/CEA-cDNA (Pèlegrin et al, 1992) using a mammalian transfection kit (Stratagene, La Jolla, CA, USA). Three µg of DNA were precipitated with calcium phosphate according to the manufacturer's instructions and incubated for 16 h with about 3 × 10 6 nonconfluent adherent carcinoma cells.…”

Expression of transgenic carcinoembryonic antigen (CEA) in tumor-prone mice: An animal model for CEA-directed tumor immunotherapy

“…Alternatively, transfection of a CEA expression vector into a mouse tumor cell line followed by injection of CEA-producing tumor cells into syngeneic mice should allow studies in immunocompetent mice. However, in this case, problems exist with masking of CEA through an induced antibody response (Pèlegrin et al, 1992). Another major limitation of both systems is that the potential side effects of CEA-producing normal tissues cannot be studied.…”