No abstract

We have previously reported an altered surface marker expression and chemotaxis of G-CSF-induced neutrophils from patients with severe congenital neutropenia. However, effects of G-CSF and influence of the underlying disease on neutrophils could not be discerned. In this study we have evaluated the effects of G-CSF on neutrophil phenotype and function in patients under chemotherapy and in healthy test subjects. We found a significantly enhanced expression of Fc gamma RI, CD14 and CD54 and a decrease in the level of Fc gamma RIII during G-CSF treatment. In addition, motility of G-CSF-induced neutrophils was significantly decreased. The effects were seen in patients under cytotoxic chemotherapy and in healthy test subjects. Surface marker alterations and neutrophil motility were affected by G-CSF administration in a dose-dependent manner. Kinetic studies on neutrophils from healthy test subjects demonstrated that all effects could be seen after a single administration of 300 micrograms G-CSF and began to appear within 4 h. Release of partially immature neutrophils from the bone marrow and indirect activation of these cells by G-CSF are discussed as possible reasons for the findings presented. They demonstrate that G-CSF has profound effects on neutrophil phenotype and function in vivo which might have clinical implications.

No abstract

The human monocytic cell line U937 was used as a model system to investigate the effects of glucocorticoids on monocytic differentiation. Upon incubation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) (5 x 10(-9) M) for 48 to 72 h, the immature U937 cells ceased to proliferate and became morphologically and functionally macrophage-like. Preincubation of the cells with glucocorticoids (dexamethasone and prednisolone, 10(-7) and 10(-6) M) but not progesterone (10(-6) M) had marked effects: The cells remained in suspension and developed very little cell-cell interaction. This correlated with decreased expression of the surface molecules ICAM-1 and CD18 as determined by fluorescence-activated cell sorter analysis. The TPA-induced ability of the cells to release lysozyme or to generate reactive oxygen radicals (determined as reduction of nitroblue tetrazolium) was markedly reduced. The induction of cyclooxygenase activity and thus the ability to release prostanoids was almost completely abolished. Inhibition of prostanoid synthesis was also observed when the glucocorticoids were administered 24 or 48 h after TPA. The primary step of TPA induction, the activation and translocation of protein kinase C, however, was not affected by glucocorticoids as determined by activity measurements and Western blot analysis. There was no change in the subsequent TPA-induced induction of c-fos. The down-regulation of the differentiation-related oncogenes c-myc and c-myb was the same in cells treated with TPA in the presence or absence of glucocorticoids. Furthermore, no significant effect of glucocorticoids on the TPA-induced growth arrest was observed. Glucocorticoids thus interfere with TPA-induced functions, which are typical for activated macrophages; however, they do not impair the differentiation process and concomitant growth inhibition.

Therapy of selected human malignancies with interferon-a is widely accepted but often complicated by the emergence of interferon-a resistance. Interferon is a pleiotropic cytokine with antiproliferative, antitumour, antiviral and immunmodulatory effect; it signals through the Jak-STAT signal transduction pathway where signal transducer and activator of transcription 1 plays an important role. Here we report both, a lack of signal transducer and activator of transcription induction in interferon-a resistant renal cell carcinoma cells and signal transducer and activator of transcription 1 reinduction of phorbol 12-myristate 13-acetate-stimulated peripheral blood mononuclear cells supernatant. Preliminary experiments on the identification of the molecules that reinducing signal transducers and activators of transcription 1 indicate that interferon-g may be the responsible candidate cytokine, but several others may be involved as well. This work provides the basis for therapeutic strategies directed at the molecular modulation of interferon-a resistance in human neoplasms. Interferon-a (IFN-a) plays an important role in the treatment of various human malignancies, among them renal cell carcinoma (Dorr, 1993); however, response to IFN-a is often impaired by the development of IFN-resistance (Devita et al, 1989), mechanisms of which are poorly understood.Interferon-a belongs to a group of cytokines with antiviral, antiproliferative, antitumour and immunmodulatory activities (Pestka et al, 1987). Binding of IFN-a to the IFN Type I receptor results in oligomerization of the receptor subunits and subsequent transphosphorylation of receptor-associated Janus-kinases Jak1 and Tyk2; activated Jak1 and Tyk2 subsequently phosphorylate tyrosine residues on the associated receptor chain. Signal transducers and activators of transcription (STAT) 1 and 2 can then bind to the receptor by their SH2 domains which are thereupon tyrosine phosphorylated by the receptor-associated Janus-kinases; thereafter, the STATs are released from the receptor and form STAT1-STAT2-heterodimers which translocate to the nucleus where they bind with p48 to form the interferon stimulated gene factor 3 (ISGF3). ISGF3 binds to the interferon stimulated response element (ISRE) in the promoter of IFN-induced genes resulting in transcription of interferon-stimulated genes (ISG) (Schindler and Darnell, 1995;Haque and Williams, 1998).There is evidence that IFN-a resistance is associated with defective components of the Jak-STAT-Pathway (Pansky et al, 2000) e.g., defective activation of ISGF3 (Xu et al, 1994;Wong et al, 1997), lack of STAT1 expression (Sun et al, 1998) or STAT3 induction (Yang et al, 1998. It has been reported that sequential treatment of interferon resistant cells with retinoic acid or tamoxifen followed by interferon-a up-regulates STAT1 expression and ISGF3 activation, respectively, in cells which do not respond to either single agent (Kolla et al, 1996;Lindner et al, 1997).Here we sought (a) to characterize STAT1 deficiency associated wit...