Molecular Assay for Megakaryocyte Stimulating Factor

Megakaryocyte colony-stimulating factor (Meg-CSF) is a lineage specific factor that specifically regulates the proliferation and differentiation of megakaryocytes from bone marrow. Meg-CSF is of significant importance in the treatment of thrombocytopenia due to diseases of a variety of etiologies, or due to chemotherapy and bone marrow transplantation. In the past, tremendous efforts have been made around the world to purify and eventually to molecularly clone this hematopoietic growth factor. However, purification of Meg-CSF has been aborted or hampered largely because of the lack of a quick, sensitive and reliable assay. This Phase I grant will develop a molecular assay for Meg-CSF using a newly-established megakaryoblastic leukemia cell line HIMeg. Preliminary studies have shown that this cell line, treated with vitamin D3 (VD3) or cis-retinoic acid (cis-RA), is able to differentiate into more mature megakaryocytes. Specifically, we will determine (i) if VD3 or cis-RA-induced differentiation is associated with up regulation of megakaryocyte/platelet gene expression and (ii) if functionally purified Meg-CSF induces megakaryocytic differentiation of HIMeg cells. The overall goal is to utilize the unique cell line to discover novel and effective factors/drugs for treatment of thrombocytopenia and megakaryoblastic leukemia.