T351 protein, a novel tumor associated antigen and potential target for immunotherapy

Tumor immunotherapy has attracted many attentions in recent years because of its high specificity. However, the use of immunotherapy is hampered by the lack of defined target tumor antigens. T351 gene, a novel tumor associated gene identified by mRNA differential display, encodes a transmembrane protein. We found that T351 is overexpressed in tumor tissues and tumor cell lines at both mRNA and protein levels by quantitative reverse transcription-PCR, immunohistochemistry and flow cytometry analyses, respectively. We also show that the extracellular portion of T351 protein termed T351pro.philic specifically activate CTLs to lyse tumor cell targets. In addition, a monoclonal antibody raised against T351pro.philic (McAb C1-1) induced murine macrophages to kill tumor cells effectively both in vitro and in vivo. These results suggest that T351 protein is a novel tumor associated antigen.