Ptn gene expression correlates with disease status in myeloma patients. Mononuclear cells from BM of a MM patient or a healthy donor, PBMCs from a plasma cell leukemia patient, and the myeloma cell lines RPMI 8226, U266, and MM-1S, and the human monocytic cell line THP-1 were analyzed for Ptn gene expression by RT-PCR. Ptn transcripts were not detected in THP-1 cells, or healthy control BM, and only minimally in a patient with indolent MM. In contrast, Ptn was expressed more highly by myeloma patients with active, refractory, or relapsed disease. The highest level of Ptn expression was detected in the malignant cells from a patient with plasma cell leukemia and the myeloma cell lines RPMI 8226, U266, and MM-1S.