Localization of alpha 2-macroglobulin in human primary sarcomas and synthesis in established cell lines

The presence of alpha 2-macroglobulin (alpha 2M) was detected with the avidin-biotin technique in more than 20-yr-old paraffin blocks from human sarcomas. alpha 2M was found mainly in the cytoplasm of the tumor cells, and almost all tumor cells were positive. This serum glycoprotein, which is a major plasma proteinase inhibitor with a wide specificity, was also shown to be synthesized and secreted by all three cell lines derived from primary sarcomas but was not detected in cultures of the autologous skin fibroblasts. For the detection of alpha 2M in situ and in vitro an antiserum to tumor-associated alpha 2-macroglobulin was used.