The HPB-AML-I cell line possesses the properties of mesenchymal stem cells

To examine this possibility, we characterized HPB-AML-I by performing cytochemical, cytogenetic, and phenotypic analyses, induction of differentiation toward mesenchymal lineage cells, and mixed lymphocyte culture analysis.HPB-AML-I proved to be negative for myeloperoxidase, while surface antigen analysis disclosed that it was positive for MSC-related antigens, such as CD29, CD44, CD55, CD59, and CD73, but not for CD14, CD19, CD34, CD45, CD90, CD105, CD117, and HLA-DR. Karyotypic analysis showed the presence of complicated abnormalities, but no reciprocal translocations typically detected in AML cases. Following the induction of differentiation toward adipocytes, chondrocytes, and osteocytes, HPB-AML-I cells showed, in conjunction with extracellular matrix formation, lipid accumulation, proteoglycan synthesis, and alkaline phosphatase expression. Mixed lymphocyte culture demonstrated that CD3+ T-cell proliferation was suppressed in the presence of HPB-AML-I cells.We conclude that HPB-AML-I cells appear to be unique neoplastic cells, which may be derived from MSCs, but are not hematopoietic progenitor cells.Mesenchymal stem cells (MSCs) constitute a cell population, which features self-renewal and differentiation into adipocytes, chondrocytes, and osteocytes. Human MSCs have been isolated from various tissues and organs, such as muscle, cartilage, synovium, dental pulp, bone marrow, tonsils, adipose tissues, placenta, umbilical cord, and thymus (reviewed by [1]). The biological roles of MSCs were initially described by Friedenstein and colleagues in 1970s. They observed bone formation and reconstitution of the hematopoietic microenvironment in rodents with subcutaneously transplanted MSCs (reviewed by [2]). In addition to providing support for the early stage of hematopoiesis, MSCs have also been reported to suppress the proliferation of CD3+ T-cells [3], which led to the utilization of MSCs in the management of various pathologic conditions, such as graft-versus-hos