Alpha (1,3)galactosyltransferase is the major xenoantigen associated with hyperacute rejection of xenotransplants. Tumor vaccines engineered to express this gene may show promise in breaking tumor tolerance. However there has been a lack of alternative tumor models to the highly published B16 with which to study the immunology associated with alpha(1,3) galactosyltransferase modified tumor vaccines. Moreover, limited in vivo models exist to study the basic biology of alpha(1,3) galactosyltransferase in xenotransplantation experiments. Therefore, we have developed a gastrointestinal stromal tumor, CA320M, derived from C57/BL6 alpha(1,3)galactosyltransferase knock-out mice. The approach, however, is based in part on the sensitivity of tumor cells to the effects of complement. Tumors expressing complement resistance factors such as membrane cofactor (CD46), decay accelerating factor (CD55) and protectin (CD59) have been shown to be more resistant to complement lysis. Anchored to the membrane by a glycosylphosphotidylinositol moiety (GPI-anchored), CD55 and CD59 can be cleaved by Bacillus thuringiensis phosphatidylinositol-specific phospholipase C (PIPLC). The PIPLC native signal sequence was replaced with the human epidermal growth factor signal sequence, EGFssPIPLC, to induce secretion from mammalian cells. (Abstract shortened by UMI.)