Reporter cell lines to screen for inhibitors or regulators of the KRAS-RAF-MEK1/2-ERK1/2 pathway

The RAS-regulated RAF-MEK1/2-ERK1/2 signalling pathway is activated in cancer due to mutations in RAS proteins (especially KRAS), BRAF, CRAF, MEK1 and MEK2. Whilst inhibitors of KRASG12C (lung adenocarcinoma) and BRAF and MEK1/2 (melanoma and colorectal cancer) are clinically approved, acquired resistance remains a problem. Consequently, the search for new inhibitors (especially of RAS proteins), new inhibitor modalities and regulators of this pathway, which may be new drug targets, continues and increasingly involves cell-based screens with small molecules or genetic screens such as RNAi, CRISPR or protein interference. Here we describe cell lines that exhibit doxycycline-dependent expression KRASG12V or BRAFV600E and harbour a stably integrated EGR1:EmGFP reporter gene that can be detected by flow cytometry, high-content microscopy or immunoblotting. KRASG12V or BRAFV600E-driven EmGFP expression is inhibited by MEK1/2 or ERK1/2 inhibitors (MEKi and ERKi). BRAFi inhibit BRAFV600E-driven EmGFP expression but enhance the response to KRASG12V, recapitulating paradoxical activation of wild type RAF proteins. In addition to small molecules, expression of iDab6, encoding a RAS-specific antibody fragment inhibited KRASG12V- but not BRAFV600E-driven EmGFP expression. Finally, substitution of EmGFP for a bacterial nitroreductase gene allowed KRASG12V or BRAFV600E to drive cell death in the presence of a pro-drug, which may allow selection of pathway inhibitors that promote survival. These cell lines should prove useful for cell-based screens to identify new regulators of KRAS- or BRAF-dependent ERK1/2 signalling (drug target discovery) as well as screening or triaging 'hits' from drug discovery screens.

The pharmaceutical solvent N-methyl-2-pyrollidone (NMP) attenuates inflammation through Krüppel-like factor 2 activation to reduce atherogenesis

N-methyl-2-pyrrolidone (NMP) is a versatile water-miscible polar aprotic solvent. It is used as a drug solubilizer and penetration enhancer in human and animal, yet its bioactivity properties remain elusive. Here, we report that NMP is a bioactive anti-inflammatory compound well tolerated in vivo, that shows efficacy in reducing disease in a mouse model of atherosclerosis. Mechanistically, NMP increases the expression of the transcription factor Kruppel-like factor 2 (KLF2). Monocytes and endothelial cells treated with NMP express increased levels of KLF2, produce less pro-inflammatory cytokines and adhesion molecules. We found that NMP attenuates monocyte adhesion to endothelial cells inflamed with tumor necrosis factor alpha (TNF-α) by reducing expression of adhesion molecules. We further show using KLF2 shRNA that the inhibitory effect of NMP on endothelial inflammation and subsequent monocyte adhesion is KLF2 dependent. Enhancing KLF2 expression and activity improves endothelial function, controls multiple genes critical for inflammation, and prevents atherosclerosis. Our findings demonstrate a consistent effect of NMP upon KLF2 activation and inflammation, biological processes central to atherogenesis. Our data suggest that inclusion of bioactive solvent NMP in pharmaceutical compositions to treat inflammatory disorders might be beneficial and safe, in particular to treat diseases of the vascular system, such as atherosclerosis.

Cellular Notch responsiveness is defined by phosphoinositide 3-kinase-dependent signals

Background

Notch plays a wide-ranging role in controlling cell fate, differentiation and development. The PI3K-Akt pathway is a similarly conserved signalling pathway which regulates processes such as differentiation, proliferation and survival. Mice with disrupted Notch and PI3K signalling show phenotypic similarities during haematopoietic cell development, suggesting functional interaction between these pathways.

Results

We show that cellular responsiveness to Notch signals depends on the activity of the PI3K-Akt pathway in cells as diverse as CHO cells, primary T-cells and hippocampal neurons. Induction of the endogenous PI3K-Akt pathway in CHO cells (by the insulin pathway), in T-cells (via TCR activation) or in neurons (via TrKB activation) potentiates Notch-dependent responses. We propose that the PI3K-Akt pathway exerts its influence on Notch primarily via inhibition of GSK3-beta, a kinase known to phosphorylate and regulate Notch signals.

Conclusion

The PI3K-Akt pathway acts as a "gain control" for Notch signal responses. Since physiological levels of intracellular Notch are often low, coincidence with PI3K-activation may be crucial for induction of Notch-dependent responses.

A Lyme borreliosis human serosurvey of asymptomatic adults in Ireland

Blood samples were obtained through the Blood Transfusion Service in Ireland in order to obtain information on the prevalence of asymptomatic B. burgdorferi infections and in an attempt to identify the type of habitat that presents the most risk of infection. Areas in the country were rated as low, medium or high risk based on the availability of suitable tick habitat, access to the public and the distribution of deer, the latter parameter being related to both the occurrence of rodent reservoir hosts and woodland recreational areas. Approximately 100 plasma samples from each of four areas were analysed for IgG anti-Borrelia antibodies by indirect immuno-fluorescence with a titre of 1 :80 indicating a positive reaction in asymptomatic individuals. Prevalence figures of 15, 11, 8 and 5% were obtained for high, high/medium, medium/low and low risk areas respectively. No positive samples were detected in blood from an Icelandic population which is not exposed to I. ricinus bites. The overall subclinical prevalence (9.75%) is surprisingly high in view of the apparent rarity of clinical cases in Ireland, though under-diagnosis probably occurs. These results seem to indicate that farmland is less important than woodland as Lyme borreliosis habitat. If this is so, it is probably due to the presence in woodland of Apodemus sylvaticus, a putative reservoir host, and also to the use of such areas for recreation at certain times of the year.