Abstract 1583: New strategy for the identification of breast cancer antigens that induce therapeutic immune responses in tumor-bearing mice

This study describes a unique strategy designed to identify breast cancer antigens (TAA) that induce therapeutic immune responses in tumor-bearing mice. In a mouse model, the strategy led to the identification of growth factor receptor-bound protein 10 (Grb10) as a newly identified TAA. Grb10 is a signal transduction molecule associated with multiple transmembrane tyrosine kinase receptors. It was discovered by comparing microarrays of cellular breast cancer vaccines highly enriched for cells that induced breast cancer immunity with non-enriched vaccines. The vaccines were prepared by transferring a cDNA expression library derived from SB5b cells, a breast cancer cell line derived from a neoplasm that arose spontaneously in the mammary gland of a C3H/He mouse into LM cells, a mouse fibroblast cell line. As the transferred cDNA integrates spontaneously into the genome of the recipient cells, replicates as the cells divide, and is expressed, the vaccine could be prepared from a little as 10 micrograms of tumor tissue. Relatively few cells in the transfected cell population, however, incorporated cDNA fragments that included genes specifying TAA. (The vast majority specified normal cellular constituents.) A unique strategy was developed, therefore, to enrich the vaccine for immunotherapeutic cells. Comparative microarrays of enriched and non-enriched vaccines resulted in the identification of twenty overrepresented genes. One, the gene for Grb10, was approximately 100-fold overrepresented. To determine if Grb10 in the enriched vaccine was partly responsible for its therapeutic benefits, the gene was incorporated into an expression plasmid that was then transfected into the fibroblast cell line, which was then used as a vaccine. Mice with established breast cancer treated solely by immunization with the fibroblasts modified to express Grb10 developed robust immunity to the breast cancer cells, which, in some instances, was sufficient to result in tumor rejection. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1583. doi:1538-7445.AM2012-1583