Emerging Applications of Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor

Multiple sclerosis onset after granulocyte macrophage colony-stimulating factor withdrawal

A 51-year old woman with stage III melanoma participated in a phase II clinical trial in which she received subcutaneous rhGM-CSF injections for 3 years. She was in remission by the end of the trial. Seven months after discontinuing GM-CSF she had her first MS event. The unique timeline of rh-GM-CSF injections in a melanoma trial, during which yearly MRI scans showed subtle stable demyelination followed by RRMS onset shortly after discontinuation of treatment, may provide some insight on the role of GM-CSF in MS.

Synthesis of granulocyte-macrophage colony-stimulating factor as homogeneous glycoforms and early comparisons with yeast cell-derived material

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a medicinally important glycoprotein, used as an immunostimulant following bone-marrow transplant. On the basis of reports of its potential utility as an anticancer vaccine adjuvant, we undertook to develop a synthetic route toward single-glycoform GM-CSF. We describe herein a convergent total synthesis of GM-CSF aglycone and two homogeneous glycoforms. Analytical and biological studies confirm the structure and activity of these synthetic congeners.

Growth factor stimulation reduces residual quiescent chronic myelogenous leukemia progenitors remaining after imatinib treatment

The BCR/ABL tyrosine kinase inhibitor imatinib mesylate is highly effective in the treatment of chronic myelogenous leukemia (CML) but fails to eliminate all leukemia cells. Residual leukemia stem and progenitor cells persist in imatinib-responsive patients and may be a potential source of relapse. Previous studies indicate that imatinib preferentially targets dividing cells, and nondividing progenitor cells are resistant to imatinib-mediated apoptosis. We investigated whether growth factor stimulation of progenitor proliferation could reduce the number of residual nondividing cells remaining after imatinib treatment. CML and normal CD34(+) cells were labeled with 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFSE) to track cell division and cultured in low or high concentrations of growth factor to determine effects of growth factor stimulation on nondividing cells. High growth factor concentrations significantly enhanced CML proliferation with or without imatinib treatment and significantly reduced the number of viable, nondividing CFSE bright cells remaining after imatinib exposure. Stimulation with high growth factor before imatinib treatment further reduced the number of residual nondividing CML CD34(+) cells. Importantly, clinically achievable concentrations of granulocyte macrophage colony-stimulating factor alone or in combination with granulocyte colony-stimulating factor also significantly reduced nondividing CML CD34(+) cells. These results support the potential efficacy of growth factor stimulation in reducing the residual leukemia progenitor population in imatinib-treated patients.

Promising agents at the interface of biology and oncology derived through chemical synthesis

This account traces the development of our synthetic glycopeptide- and glycoprotein-based research program over the past decade. We recount the syntheses of a number of biologically relevant, natural product-inspired glycopeptide constructs, including those associated with prostate specific antigen (PSA) and with the gp120 surface envelope protein of HIV. We also describe our progress toward the synthesis of the multiply glycosylated protein, erythropoietin (EPO). Particular emphasis is placed on the development of enabling methodologies which allow for the ligation of complex glycopeptide fragments, thus rendering it possible to access, through purely synthetic means, homogeneous, multidomainal glycopeptide and glycoprotein constructs.