mk-2206 and Hypoxia

Tumor necrosis factor α-induced protein 1 (TNFAIP1) has been documented as a vital regulator of apoptosis and oxidative stress under various pathological conditions. However, whether TNFAIP1 plays a role in myocardial ischemia/reperfusion (I/R) injury has not been well investigated. This work aimed to evaluate the possible role of TNFAIP1 in mediating myocardial I/R injury. Firstly, we demonstrated that TNFAIP1 expression was dramatically increased in rat cardiomyocytes following hypoxia/reoxygenation (H/R) in vitro, and in rat myocardial tissues following I/R treatment in vivo. Silencing of TNFAIP1 alleviated H/R-induced apoptosis, oxidative stress and inflammatory response in rat cardiomyocytes in vitro. Moreover, knockdown of TNFAIP1 ameliorated I/R-induced myocardial injury, infarction size, cardiac apoptosis, oxidative stress and inflammatory response in vivo. Further investigation elucidated that knockdown of TNFAIP1 enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling associated with modulation of the Akt/glycogen synthase kinase-3β (GSK-3β) pathway in vitro and in vivo. Inhibition of Akt markedly abrogated TNFAIP1-knockdown-mediated Nrf2 activation in cardiomyocytes following H/R injury. In addition, suppression of Nrf2 significantly diminished TNFAIP1-knockdown-induced cardioprotective effects in H/R-exposed cardiomyocytes. In summary, this work elucidates that inhibition of TNFAIP1 ameliorates myocardial I/R injury by potentiating Nrf2 signaling via the modulation of the Akt/GSK-3β pathway. Our study highlights a vital role of the TNFAIP1/Akt/GSK-3β/Nrf2 pathway in mediating myocardial I/R injury and suggests TNFAIP1 as an attractive target for treatment of this disease.

Topics: Animals; Apoptosis; Carrier Proteins; Cells, Cultured; Cytokines; Glycogen Synthase Kinase 3 beta; Heterocyclic Compounds, 3-Ring; Hypoxia; Inflammation; Models, Animal; Myocardial Reperfusion Injury; Myocytes, Cardiac; NF-E2-Related Factor 2; Oxidative Stress; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Signal Transduction; STAT1 Transcription Factor

Only a minority of cancer patients benefits from the combination of EGFR-inhibition and radiotherapy in head and neck squamous cell carcinoma (HNSCC). A potential resistance mechanism is activation of EGFR and/or downstream pathways by stimuli in the microenvironment. The aim of this study was to find molecular targets induced by the microenvironment by determining the in vitro and in vivo expression of proteins of the EGFR-signaling network in 6 HNSCC lines. As hypoxia is an important microenvironmental parameter associated with poor outcome in solid tumors after radiotherapy, we investigated the relationship with hypoxia in vitro and in vivo.. Six human HNSCC cell lines were both cultured as cell lines (in vitro) and grown as xenograft tumors (in vivo). Expression levels were determined via western blot analysis and localization of markers was assessed via immunofluorescent staining. To determine the effect of hypoxia and pAKT-inhibition on cell survival, cells were incubated at 0.5% O(2) and treated with MK-2206.. We observed strong in vitro-in vivo correlations for EGFR, pEGFR and HER2 (rs = 0.77, p = 0.10, rs = 0.89, p = 0.03) and rs = 0.93, p = 0.02, respectively), but not for pAKT, pERK1/2 or pSTAT3 (all r(s)<0.55 and p>0.30). In vivo, pAKT expression was present in hypoxic cells and pAKT and hypoxia were significantly correlated (rs = 0.51, p = 0.04). We confirmed in vitro that hypoxia induces activation of AKT. Further, pAKT-inhibition via MK-2206 caused a significant decrease in survival in hypoxic cells (p<0.01), but not in normoxic cells.. These data suggest that (p)EGFR and HER2 expression is mostly determined by intrinsic features of the tumor cell, while the activation of downstream kinases is highly influenced by the tumor microenvironment. We show that hypoxia induces activation of AKT both in vitro and in vivo, and that hypoxic cells can be specifically targeted by pAKT-inhibition. Targeting pAKT is thus a potential way to overcome therapy resistance induced by hypoxia and improve patient outcome.

Topics: Animals; Blotting, Western; Carcinoma, Squamous Cell; Cell Hypoxia; Cell Line, Tumor; Cell Survival; Combined Modality Therapy; ErbB Receptors; Fluorescent Antibody Technique; Head and Neck Neoplasms; Heterocyclic Compounds, 3-Ring; Humans; Hypoxia; Mice; Mice, Inbred BALB C; Mice, Nude; Nitroimidazoles; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Radiation-Sensitizing Agents; Radiotherapy; Receptor, ErbB-2; Signal Transduction; Tumor Microenvironment; Xenograft Model Antitumor Assays