Biomedical subjects

J Fishbaugh

Publications and source records attributed to J Fishbaugh.

21 records · Page 2Linked to original sources

PubMed1986

Cell cycle dependence of calmodulin levels during HL-60 proliferation and myeloid differentiation. No changes during pre-commitment.

The putative role of Ca2+ and calmodulin in regulating cell proliferation and differentiation was tested in HL-60 human promyelocytic leukemia cells. The dependence of retinoic acid (RA)-induced terminal myeloid differentiation of HL-60 promyelocytic leukemia cells on calmodulin levels and calcium ion flux was ascertained. RA-treated and untreated control cells were stained for cellular DNA with a Hoechst dye. Populations of G1/0, S and G2 + M phase cells were isolated by fluorescence activated cell sorting (FACS). Cytosolic calmodulin levels were then measured as a function of cell cycle phase for RA-treated and untreated cells using a radioimmunoassay. RA-treated cells were measured at early times, corresponding to the pre-commitment state, and late times, when significant cell differentiation had occurred. Cellular calmodulin levels increased with progression through the cell cycle. In contrast, no difference in calmodulin levels was observed between RA-untreated or -treated cells in the same cell cycle phases at early or late times. RA-induced HL-60 terminal myeloid differentiation was thus apparently not regulated by cellular cytosolic calmodulin levels. These conclusions were supported by the effects of calmodulin antagonists and calcium flux inhibitors. The calmodulin antagonists trifluoperazine and compound 48/80 both retarded cell growth in a concentration-dependent manner. But at concentrations where cellular effect was evidenced by slight growth inhibition, neither antagonist inhibited RA-induced cell differentiation or G1/0 growth arrest. The same was true of the gated calcium channel inhibitors, verapamil and nitrendipene, and the passive calcium flux inhibitor, CoCl2. RA-induced HL-60 cell differentiation and arrest in G0 was thus apparently not strongly dependent on cellular calmodulin levels or calcium flux. This is in strong contrast to murine erythroleukemia cells. The results argue against a central regulatory role for calmodulin or calcium flux in control of HL-60 growth arrest or differentiation.

Calmodulin↗

PubMed1986

Retinoic acid induced HL-60 myeloid differentiation: dependence of early and late events on isomeric structure.

The capability of HL-60 cells to undergo G1/0 specific growth arrest and myeloid differentiation in response to isomers of retinoic acid (RA) having an altered alkyl chain was determined. At a concentration where beta-all trans RA induces myeloid differentiation and G1/0 specific growth arrest, 11,13-dicis and 9,13-dicis isomers failed to induce significant phenotypic differentiation, assayed by the inducible superoxide production characteristic of mature myeloid cells, but could induce moderate G1/0 specific growth arrest. The 9-cis and 11-cis isomers induced both phenotypic differentiation and G1/0 specific growth arrest. The occurrence of G1/0 specific growth arrest without phenotypic differentiation indicates that the induced cellular programs leading to phenotypic differentiation and G1/0 specific growth arrest are not tightly coupled. Within the 48-h period usually required by beta-all trans RA to induce onset of phenotypic differentiation and G1/0 specific growth arrest, all isomers could complete early events in the cellular programs leading to G1/0 specific growth arrest and phenotypic differentiation, but the dicis isomers could not complete late events in the phenotypic differentiation program. The capability of dicis isomers to drive late events in the G1/0 specific growth arrest program was also compromised. Characteristic early and late changes in Ca2+ binding cytosolic proteins induced by RA and its isomers were consistent with their early and late capabilities. Failure of the dicis isomers to induce differentiation was thus due to a failure in late events associated with aberrations in cytosolic, Ca2+ binding proteins. The results suggest a model in which RA presents two signals to induce HL-60 terminal differentiation.

Calcium-Binding Proteins↗

PubMed1985

Myeloid differentiation-inducing factors produced by pokeweed mitogen-treated normal G1/0 lymphocytes but not chronic lymphocytic leukemia cells.

HL-60 human promyelocytic leukemia cells undergo myeloid differentiation and G1/0 specific growth arrest in response to an activity produced by pokeweed mitogen stimulated peripheral blood mononuclear cells. Elaboration of this myeloid differentiation inducing activity does not require lymphocytic proliferation or pokeweed mitogen induced B-lymphocyte differentiation. The activity is a product of initially stimulated G1/0 lymphocytes. It is not produced by proliferating lymphocytes. The activity is not elaborated by G1/0 peripheral blood lymphocytes of patients with chronic lymphocytic leukemia, cells which are proliferatively refractory to pokeweed mitogen stimulation.

Cell Differentiation↗