Mutant HRAS as novel target for MEK and mTOR inhibitors

HRAS is a frequently mutated oncogene in cancer. However, mutant HRAS as drug target has not been investigated so far. Here, we show that mutant HRAS hyperactivates the RAS and the mTOR pathway in various cancer cell lines including lung, bladder and esophageal cancer. HRAS mutation sensitized toward growth inhibition by the MEK inhibitors AZD6244, MEK162 and PD0325901. Further, we found that MEK inhibitors induce apoptosis in mutant HRAS cell lines but not in cell lines lacking RAS mutations. In addition, knockdown of HRAS by siRNA blocked cell growth in mutant HRAS cell lines. Inhibition of the PI3K pathway alone or in combination with MEK inhibitors did not alter signaling nor had an impact on viability. However, inhibition of mTOR or combined inhibition of MEK and mTOR reduced cell growth in a synergistic manner. Finally, Ba/F3 cells transformed with mutant HRAS isoforms Q61L, Q61R and G12V demonstrated equal sensitivity towards MEK and mTOR inhibition. Our results show that HRAS mutations in cancer activate the RAS and mTOR pathways which might serve as a therapeutic option for patients with HRAS mutant tumors

The EBI2-oxysterol axis promotes the development of intestinal lymphoid structures and colitis.

The gene encoding for Epstein-Barr virus-induced G-protein-coupled receptor 2 (EBI2) is a risk gene for inflammatory bowel disease (IBD). Together with its oxysterol ligand 7α,25-dihydroxycholesterol, EBI2 mediates migration and differentiation of immune cells. However, the role of EBI2 in the colonic immune system remains insufficiently studied. We found increased mRNA expression of EBI2 and oxysterol-synthesizing enzymes (CH25H, CYP7B1) in the inflamed colon of patients with ulcerative colitis and mice with acute or chronic dextran sulfate sodium (DSS) colitis. Accordingly, we detected elevated levels of 25-hydroxylated oxysterols, including 7α,25-dihydroxycholesterol in mice with acute colonic inflammation. Knockout of EBI2 or CH25H did not affect severity of DSS colitis; however, inflammation was decreased in male EBI2 <sup>-/-</sup> mice in the IL-10 colitis model. The colonic immune system comprises mucosal lymphoid structures, which accumulate upon chronic inflammation in IL-10-deficient mice and in chronic DSS colitis. However, EBI2 <sup>-/-</sup> mice formed significantly less colonic lymphoid structures at baseline and showed defects in inflammation-induced accumulation of lymphoid structures. In summary, we report induction of the EBI2-7α,25-dihydroxycholesterol axis in colitis and a role of EBI2 for the accumulation of lymphoid tissue during homeostasis and inflammation. These data implicate the EBI2-7α,25-dihydroxycholesterol axis in IBD pathogenesis

PTPN2 controls differentiation of CD4(+) T cells and limits intestinal inflammation and intestinal dysbiosis

Loss-of-function variants within the gene locus encoding protein tyrosine phosphatase non-receptor type 2 (PTPN2) are associated with increased risk for Crohn's disease (CD). A disturbed regulation of T helper (Th) cell responses causing loss of tolerance against self- or commensal-derived antigens and an altered intestinal microbiota plays a pivotal role in CD pathogenesis. Loss of PTPN2 in the T-cell compartment causes enhanced induction of Th1 and Th17 cells, but impaired induction of regulatory T cells (Tregs) in several mouse colitis models, namely acute and chronic dextran sodium sulfate colitis, and T-cell transfer colitis models. This results in increased susceptibility to intestinal inflammation and intestinal dysbiosis which is comparable with that observed in CD patients. We detected inflammatory infiltrates in liver, kidney, and skin and elevated autoantibody levels indicating systemic loss of tolerance in PTPN2-deficient animals. CD patients featuring a loss-of-function PTPN2 variant exhibit enhanced Th1 and Th17 cell, but reduced Treg markers when compared with PTPN2 wild-type patients in serum and intestinal tissue samples. Our data demonstrate that dysfunction of PTPN2 results in aberrant T-cell differentiation and intestinal dysbiosis similar to those observed in human CD. Our findings indicate a novel and crucial role for PTPN2 in chronic intestinal inflammation.Mucosal Immunology advance online publication, 10 December 2014; doi:10.1038/mi.2014.122

Elevated oxysterol levels in human and mouse livers reflect non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH), a primary cause of liver disease, leads to complications such as fibrosis, cirrhosis, and carcinoma, but the pathophysiology of NASH is incompletely understood. Epstein Barr virus induced G protein coupled receptor 2 (EBI2) and its oxysterol ligand 7α,25-dihydroxycholesterol (7α,25-diHC) are recently discovered immune regulators. Several lines of evidence suggest a role of oxysterols in NASH pathogenesis, but rigorous testing has not been performed. We measured oxysterol levels in livers of NASH patients by liquid chromatography-mass spectrometry and tested the role of the EBI2-7α,25-diHC-system in a murine feeding model of NASH. Free oxysterol profiling in livers from NASH patients revealed a pronounced increase in 24- and 7-hydroxylated oxysterols in NASH compared to controls. Levels of 24- and 7-hydroxylated oxysterols correlated with histological NASH activity. Histological analysis of murine liver samples demonstrated ballooning and liver inflammation. No significant genotype related differences were observed in Ebi2-/- animals and animals with defects in the 7α,25-diHC synthesizing enzymes CH25H and CYP7B1 compared to wildtype littermate controls, arguing against an essential role of these genes in NASH pathogenesis. Elevated 24- and 7-hydroxylated oxysterol levels were confirmed in murine NASH liver samples. Our results suggest increased bile acid synthesis in NASH samples, as judged by enhanced level of 7α-hydroxycholest-4-en-3-one, and impaired 24S-hydroxycholesterol metabolism as characteristic biochemical changes in livers affected by NASH

Aluminum enhances inflammation and decreases mucosal healing in experimental colitis in mice

The increasing incidence of inflammatory bowel diseases (IBDs) in developing countries has highlighted the critical role of environmental pollutants as causative factors in their pathophysiology. Despite its ubiquity and immune toxicity, the impact of aluminum in the gut is not known. This study aimed to evaluate the effects of environmentally relevant intoxication with aluminum in murine models of colitis and to explore the underlying mechanisms. Oral administration of aluminum worsened intestinal inflammation in mice with 2,4,6-trinitrobenzene sulfonic acid- and dextran sodium sulfate-induced colitis and chronic colitis in interleukin 10-negative (IL10(-/-)) mice. Aluminum increased the intensity and duration of macroscopic and histologic inflammation, colonic myeloperoxidase activity, inflammatory cytokines expression, and decreased the epithelial cell renewal compared with control animals. Under basal conditions, aluminum impaired intestinal barrier function. In vitro, aluminum induced granuloma formation and synergized with lipopolysaccharide to stimulate inflammatory cytokines expression by epithelial cells. Deleterious effects of aluminum on intestinal inflammation and mucosal repair strongly suggest that aluminum might be an environmental IBD risk factor.Mucosal Immunology advance online publication, 16 October 2013; doi:10.1038/mi.2013.78

β6‐integrin serves as a novel serum tumor marker for colorectal carcinoma

Abstract Colorectal cancer (CRC) is one of the leading causes of cancer‐related deaths worldwide and the need for novel biomarkers and therapeutic strategies to improve diagnosis and surveillance is obvious. This study aims to identify β6‐integrin (ITGB6) as a novel serum tumor marker for diagnosis, prognosis, and surveillance of CRC. ITGB6 serum levels were validated in retro‐ and prospective CRC patient cohorts. ITGB6 serum levels were analyzed by ELISA. Using an initial cohort of 60 CRC patients, we found that ITGB6 is present in the serum of CRC, but not in non‐CRC control patients. A cut‐off of ≥2 ng/mL ITGB6 reveals 100% specificity for the presence of metastatic CRC. In an enlarged study cohort of 269 CRC patients, ITGB6 predicted the onset of metastatic disease and was associated with poor prognosis. Those data were confirmed in an independent, prospective cohort consisting of 40 CRC patients. To investigate whether ITGB6 can also be used for tumor surveillance, serum ITGB6‐levels were assessed in 26 CRC patients, pre‐ and post‐surgery, as well as during follow‐up visits. After complete tumor resection, ITGB6 serum levels declined completely. During follow‐up, a new rise in ITGB6 serum levels indicated tumor recurrence or the onset of new metastasis as confirmed by CT scan. ITGB6 was more accurate for prognosis of advanced CRC and for tumor surveillance as the established marker carcinoembryonic antigen (CEA). Our findings identify ITGB6 as a novel serum marker for diagnosis, prognosis, and surveillance of advanced CRC. This might essentially contribute to an optimized patient care