Given the fact that we and others have previously detected sHLA-E in the supernantants of melanoma and colorectal cell lines by Western blot analysis, we investigated, using our designed ELISA, the production of sHLA-E by tumor cell lines derived from major tumor categories, including solid tumors as melanoma, cancers of the breast, colon and kidney and liquid tumors as mesotheliomas and myelomas [12], [27]. Here, HLA-E is linked to breast cancer.