Melanoma B16-F1 cells coated with fusion protein of mouse calreticulin and virus G-protein coupled receptor induced the antitumor immune response in Balb/C mice

In apoptotic progress of tumor cells stimulated by special agents, the calreticulin (CRT) was relocated from endoplasmic reticulum onto the cell surface. When used as a cellular antigen to immunize experimental animals, these CRT-coated apoptotic tumor cells could initiate effective antitumor immunoresponse against homologous tumor cells, indicating the value of CRT in antitumor immunotherapy. In order to develop a universal technique that could make CRT-coating more efficient in the tumor cells, in this study, a mouse CRT recombinant gene with virus G-protein coupled receptor (vGPCR) was constructed and cloned into vector pcDNA3.1(+). When the resulting plasmid pcDNA3.1(+)-mCRT/vGPCR was stably transfected into the mouse melanoma B16-F1 cells, the mCRT-vGPCR recombinant protein was synthesized. With the membrane-locating ability of vGPCR in the recombinant protein, mCRT-vGPCR was carried onto the surface of B16-F1 cells efficiently. Overexpression of mCRT-vGPCR on the cell surface could enhance the phagocytosis of B16-F1 by macrophages in vitro. When mCRT-vGPCR coated B16-F1 cells were used as a cell-antigen to immunize mice, the specific antitumor immune response against the homologous tumor cells was initiated efficiently. Our data in this study may provide a new possibility for CRT-mediated tumor immune prevention and treatment.