Detection and enrichment of carcinoma-in-situ cells in semen by an immunomagnetic method using monoclonal antibody M2A

Carcinoma-in-situ (CIS) is a precursor of germ cell cancers in the testis. Early detection and treatment of CIS can prevent the development of invasive cancer. We have developed an immunomagnetic approach for enrichment of CIS cells from semen. Immunomagnetic beads were coated with monoclonal antibody (mAb) M2A, which is specific for seminoma and CIS. In preliminary mixing experiments, cultured human HEY cells, which express the M2A surface antigen, were added to semen samples and recovered selectively by incubation with M2A-coated immunomagnetic beads followed by magnetic activated cell sorting (MACS). Application of this procedure to ejaculates from five subjects with CIS and 22 control subjects with no evidence of testicular neoplasia resulted in the preferential recovery of a population of large round cells from a 0.5 ml semen sample obtained from CIS subjects (median 1 x 10(4), range 2 x 10(3) to 2 x 10(4)) relative to controls (median 2 x 10(2); range 0 to 10(3)), with no overlap between the two groups (p < 0.001). These results suggest that a subpopulation of large round cells recovered from the semen of CIS patients by incubation with M2A-coated immunomagnetic beads and MACS are CIS cells. Immunomagnetic enrichment of CIS cells in semen will facilitate the definitive identification of exfoliated CIS cells in ejaculates and could be an important first step in a non-invasive screening procedure for testicular CIS.