Serum/glucocorticoid-regulated kinase 1 (SGK1) is a prominent target gene of the transcriptional response to cytokines in multiple myeloma and supports the growth of myeloma cells.

Multiple myeloma (MM) is a paradigm for a malignant disease that exploits external stimuli of the microenvironment for growth and survival. A thorough understanding of the complex interactions between malignant plasma cells and their surrounding requires a detailed analysis of the transcriptional response of myeloma cells to environmental signals. We determined the changes in gene expression induced by interleukin (IL)-6, tumor necrosis factor-α, IL-21 or co-culture with bone marrow stromal cells in myeloma cell lines. Among a limited set of genes that were consistently activated in response to growth factors, a prominent transcriptional target of cytokine-induced signaling in myeloma cells was the gene encoding the serine/threonine kinase serum/glucocorticoid-regulated kinase 1 (SGK1), which is a down-stream effector of PI3-kinase. We could demonstrate a rapid, strong and sustained induction of SGK1 in the cell lines INA-6, ANBL-6, IH-1, OH-2 and MM.1S as well as in primary myeloma cells. Pharmacologic inhibition of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway abolished STAT3 phosphorylation and SGK1 induction. In addition, small hairpin RNA (shRNA)-mediated knock-down of STAT3 reduced basal and induced SGK1 levels. Furthermore, downregulation of SGK1 by shRNAs resulted in decreased proliferation of myeloma cell lines and reduced cell numbers. On the molecular level, this was reflected by the induction of cell cycle inhibitory genes, for example, CDKNA1/p21, whereas positively acting factors such as CDK6 and RBL2/p130 were downregulated. Our results indicate that SGK1 is a highly cytokine-responsive gene in myeloma cells promoting their malignant growth.

Elevated serum concentrations of activated hepatocyte growth factor activator in patients with multiple myeloma.

OBJECTIVES: Hepatocyte growth factor (HGF) is a potential key factor in multiple myeloma. Conversion of pro-HGF to its active form is a critical limiting step for its biological effects. We aimed to examine the levels of the most potent activator, the hepatocyte growth factor activator (HGFA), in serum and bone marrow plasma of patients with multiple myeloma. METHODS: The activated form of HGFA was measured by an enzyme-linked immunosorbent assay in serum (n = 49) and bone marrow plasma (n = 16) from multiple myeloma patients, and in serum from healthy controls (n = 24). RESULTS: The median concentrations of activated HGFA in myeloma and control sera were 39.7 (range 6.2-450.0) and 17.6 ng/mL (range 4.8-280.6), respectively. The difference was statistically significant (P = 0.037). The median concentration of activated HGFA in bone marrow plasma was 6.1 ng/mL (range 3.5-30.0). CONCLUSION: We here show for the first time that the activated form of HGFA is present at high levels in serum and bone marrow of myeloma patients, thus providing a necessary prerequisite for the activation of HGF.

Mechanisms effecting analysis of volatile flavour components by solid-phase microextraction and gas chromatography.

Quantitative properties of solid-phase microextraction (SPME) have been studied in order to investigate a simple and reliable method for analysing volatile flavour components in strawberries. Monitoring the chemical composition profile of berries will be of interest for the producers in order to optimise growth and storage conditions. By the use of SPME and capillary gas chromatography selected standard components were quantified with accuracy within +/-7% and a linear response were found in all concentration ranges studied, covering three orders of magnitude. Equilibrium constants that describe how various components are distributed between the three phases present, sample, headspace and fibre coating were determined. In the system studied, the majority of analytes remained in the sample. This means that repeated analysis can be performed from a single sample without significantly changing the results. The mass transfers of the flavour components, from the sample and into the fibre, were fitted to a transport model assuming that the rate-controlling step is diffusion within the fibre. The experimental results agreed well with the model for most of the components studied. The response for three of the components (geraniol, linalool and trans-2-hexenyl butanoate) did not agree with the model. These components were present in the gas phase in only minute amounts explaining the deviation from the model. Such components will require a long absorption time (longer than 30 min). For quantitative analysis, it is important to use a very precise pre-determined absorption period and well defined sampling conditions. Internal standards can be omitted.