Differential expression of 2IgB7-H3 and 4IgB7-H3 in cancer cell lines and glioma tissues.

B7-H3 protein is an important tumor antigen, but the expression of its isoforms, 4IgB7-H3 and 2IgB7-H3, in tumor tissues remains unknown due to the lack of specific monoclonal antibodies (mAbs). In the present study, a mAb (9C3) specifically recognizing 2IgB7-H3, but not 4IgB7-H3, was prepared. Using 9C3 and a previously prepared mAb (4H7) that recognizes 4IgB7-H3 and 2IgB7-H3, the differential expression of 2IgB7-H3 and 4IgB7-H3 was analyzed in a variety of tumor cell lines by flow cytometry. It was found that 4IgB7-H3 had a more broad spectrum of expression among the cell lines compared with 2IgB7-H3. The expression of the two isoforms was further examined in glioma tissues using reverse transcription-polymerase chain reaction and immunohistochemistry techniques. The data revealed that 2IgB7-H3, but not 4IgB7-H3, was specifically expressed in glioma. Taken together, these results demonstrated for the first time that 2IgB7-H3 is a valuable biomarker for the diagnosis of glioma.