cholecalciferol and hexamethylene-bisacetamide

Topics: Acetamides; Amifostine; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Arginine; Azacitidine; Butyrates; Cholecalciferol; Cytarabine; Harringtonines; Hematopoietic Cell Growth Factors; Heme; Homoharringtonine; Humans; Interferons; Myelodysplastic Syndromes; Retinoids

Raised plasma levels of immunoreactive human calcitonin (ihCT) can be found in patients with myeloid leukemia and seem to indicate a poor prognosis. High levels were found in acute undifferentiated and acute myeloblastic leukemia. To test whether CT expression could be a marker of myeloid differentiation, we used the promyelocytic leukemia cell line HL 60 which also expresses ihCT as a model system for myeloid differentiation. Exponentially growing HL 60 cells as well as differentiation induced HL 60 cells expressed a single 1.0 Kb CT transcript. The induction of HL 60 cell differentiation along the granulocytic lineage by DMSO or HMBA had no effect on the level of CT transcripts. Induction of monocytic/macrophagic differentiation by TPA resulted in a transient, about 10-fold elevated expression of CT steady state mRNA after 24 h. In contrast to TPA, induction of HL 60 cell differentiation along the monocytic pathway by Vit D3 had no detectable effect on the level of the CT in RNA expression at corresponding time points. These findings suggest that the transient induction of CT steady state mRNA expression by TPA is rather a direct effect of the phorbol ester than commitment along the monocytic line of differentiation.

Topics: Acetamides; Calcitonin; Calcitonin Gene-Related Peptide; Cell Differentiation; Cell Division; Cholecalciferol; Dimethyl Sulfoxide; Gene Expression; Humans; Leukemia, Promyelocytic, Acute; Macrophages; Models, Biological; Monocytes; Phenotype; RNA, Messenger; Staining and Labeling; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

Patients with acute promyelocytic leukemia (APL) associated with the t(15;17) translocation and fusion of the promyelocytic leukemia (PML) and retinoic acid receptor-alpha (RAR-alpha) genes achieve complete remission but not cure with all-trans retinoic acid (RA), NB4, a cell line derived from a patient with t(15;17) APL that undergoes granulocytic differentiation when treated with pharmacologic doses of RA, was used as a model for differentiation therapy of APL. We found that NB4 cells are resistant to differentiation by nonretinoid inducers such as hexamethylene bisacetamide (HMBA), butyrates, vitamin D3, or hypoxanthine, all of which can induce differentiation in the commonly used HL60 leukemia cell line. Preexposure of NB4 cells to low concentrations of RA for a period as short as 30 minutes abolished resistance to nonretinoids and potentiated differentiation. Sequential RA and HMBA treatment yielded maximal differentiation by 3 days of drug exposure, whereas the effect of RA alone peaked after 6 days and yielded a smaller percentage of differentiated cells. RA also reversed NB4 cell resistance to butyrates and allowed for synergistic differentiation by these agents. Pretreatment with HMBA before exposure to RA failed to stimulate differentiation. Sequential RA/HMBA treatment also markedly increased the extent of differentiation of primary cultures of bone marrow and peripheral blood mononuclear cells from three APL patients. In one case RA/HMBA treatment overcame resistance to RA in vitro. Together, these results suggest that intermittent low doses of RA followed by either HMBA or butyrates may be a useful combination in the treatment of APL. This clinical strategy may help prevent or overcome RA resistance in APL.

Topics: Acetamides; Butyrates; Cell Differentiation; Cholecalciferol; Cytarabine; Drug Synergism; Humans; In Vitro Techniques; Leukemia, Promyelocytic, Acute; Tretinoin; Tumor Cells, Cultured