Immunoblot analysis of CD34 expression in histologically diverse neoplasms

CD34 is a heavily glycosylated transmembrane protein of similar to 110 kd w hose function is essentially uncharacterized, First identified in a myeloid leukemia cell line, immunohistological reactivity with anti-CD34 antibodie s is also encountered in a histologically diverse subset of nonhematolympho id neoplasms including angiosarcoma, solitary fibrous tumors, epithelioid s arcomas, spindle cell lipomas, dermatofibrosarcoma protuberans, and myofibr oblastomas, Immunohistological reactivity for CD34 in hematopoietic stem ce lls and endothelial cells has been shown to correspond to the expression of the CD34 protein, With the exception of gastrointestinal stromal tumors, C D34 protein expression has not been investigated in other CD34 immunohistol ogically reactive nonhematolymphoid neoplasms, We undertook this study to e xamine whether the observed reactivity for anti-CD34 antibodies in apparent ly unrelated tumors is due to the expression of the same protein or whether shared epitopes elaborated by other proteins could account for this reacti vity, Immunoblot analyses with anti-CD34 antibodies of six different CD34 i mmunohistologically reactive lesions show the same similar to 110-kd molecu lar weight protein. In addition, two cases of dermatofibrosarcoma protubera ns sl;ow double bands at similar to 110 kd. Laser-capture microdissection o f CD34 immunohistologically reactive epithelioid sarcoma and nonreactive ep idermal cells illustrates that this reactivity is specific to tumor cells, These results show that the observed immunohistological reactivity with ant i-CD34 antibodies is due to the expression of the CD34 protein and not to s hared epitopes on unrelated proteins.