Sorafenib Sensitizes Glioma Cells to the BH3 Mimetic ABT-737 by Targeting MCL1 in a STAT3-Dependent Manner.

The oncogenic transcription factor signal transducer and activator of transcription 3 (STAT3) is overactivated in malignant glioma and plays a key role in promoting cell survival, thereby increasing the acquired apoptosis resistance of these tumors. Here we investigated the STAT3/myeloid cell leukemia 1 (MCL1) signaling pathway as a target to overcome the resistance of glioma cells to the Bcl-2-inhibiting synthetic BH3 mimetic ABT-737. Stable lentiviral knockdown of MCL1 sensitized LN229 and U87 glioma cells to apoptotic cell death induced by single-agent treatment with ABT-737 which was associated with an early activation of DEVDase activity, cytochrome c release, and nuclear apoptosis. Similar sensitizing effects were observed when ABT-737 treatment was combined with the multikinase inhibitor sorafenib which effectively suppressed levels of phosphorylated STAT3 and MCL1 in MCL1-proficient LN229 and U87 glioma cells. In analogous fashion, these synergistic effects were observed when we combined ABT-737 with the STAT3 inhibitor WP-1066. Lentiviral knockdown of the activating transcription factor 5 combined with subsequent quantitative polymerase chain reaction analysis revealed that sorafenib-dependent suppression of MCL1 occurred at the transcriptional level but did not depend on activating transcription factor 5 which previously had been proposed to be essential for MCL1-dependent glioma cell survival. In contrast, the constitutively active STAT3 mutant STAT3-C was able to significantly enhance MCL1 levels under sorafenib treatment to retain cell survival. Collectively, these data demonstrate that sorafenib targets MCL1 in a STAT3-dependent manner, thereby sensitizing glioma cells to treatment with ABT-737. They also suggest that targeting STAT3 in combination with inducers of the intrinsic pathway of apoptosis may be a promising novel strategy for the treatment of malignant glioma.

Curcumin downregulates the inflammatory cytokines CXCL1 and -2 in breast cancer cells via NFkappaB.

The dietary antioxidant Curcumin has been proposed for cancer chemoprevention since it induces apoptosis and inhibits the formation of breast cancer metastases. Curcumin acts through the inhibition of phosphorylation of the inhibitor of kappa B (IkappaB), which in turn reduces the nuclear translocation of nuclear factor kappa B (NFkappaB), an inflammation- and cell survival-related transcription factor. However, it is not clear whether the strong antimetastatic effect can exclusively be explained by inhibition of NFkappaB. Here, we addressed the effects of Curcumin (IC(50) = 17 muM) in MDA-MB-231 breast cancer cells using microarray gene expression analyses. Among the 62 genes whose expression was significantly altered, we found the two inflammatory cytokines CXCL1 and -2 (Groalpha and -beta) that were downregulated. Further validation of the microarray results by quantitative real-time reverse transcription-polymerase chain reaction, western blots and enzyme-linked immunosorbent assay revealed that Curcumin impairs transcription of CXCL1 and -2 >24 h and reduces the corresponding proteins. Using small interfering RNA techniques, we elucidated the underlying molecular mechanism revealing that reduction of CXCL1 and -2 messenger RNA levels is NFkappaB dependent and requires intact IkappaBalpha expression. Moreover, CXCL1 and -2 silencing leads to downregulation of several metastasis-promoting genes among which we found the cytokine receptor CXCR4. We therefore suggest that the decrease of CXCL1 and -2 mediated by Curcumin is involved in the inhibition of metastasis.

Microfabricated differential mobility spectrometry with pyrolysis gas chromatography for chemical characterization of bacteria.

A microfabricated drift tube for differential mobility spectrometry (DMS) was used with pyrolysis-gas chromatography (py-GC) to chemically characterize bacteria through three-dimensional plots of ion intensity, compensation voltage from differential mobility spectra, and chromatographic retention time. The DMS analyzer provided chemical information for positive and negative ions simultaneously from chemical reactions between pyrolysis products in the GC effluent and reactant ions of H+(H2O)n and O2-(H2O)n in air at ambient pressure. Authentic standards for chemicals formed in the pyrolysis of bacteria showed favorable matches with plots from py-GC/DMS analysis and were supported by py-GC/MS results. These and other yet-unidentified constituents provided a means to distinguish Escherichia coli from Micrococcus luteus. A Gram-positive spore former (Bacillus megaterium) was distinguished by an abundant peak for crotonic acid evident in positive and negative ions and not observed with M. luteus. In contrast, plots from py-GC/DMS of lipid A and lipoteichoic acid showed poor matches to plots for a Gram-negative (E. coli) bacterium and a Gram-positive (M. luteus) bacterium and the differences were attributed to differences in genus sources of the biopolymers. A significant percentage of the chemical information available in py-GC/DMS is unidentified, and the analytical utility must be established. Precision in the chemical measurement was determined as +/- 0.2 V, 10% relative standard deviation (RSD), and +/- 0.05 min for compensation voltage, peak intensity, and retention time, respectively. The minimum number of total bacteria (cell forming units) detected was 6000 though detection limits and resolution could be varied by the magnitude of the separation voltage in the differential mobility spectrometer.