Insulin stimulates IGFBP-2 expression in 3T3-L1 adipocytes through the PI3K/mTOR pathway

Insulin-like growth factor binding protein 2 (IGFBP-2) has been implicated in the etiology of several diseases, including the metabolic syndrome. Although IGFBP-2 derives mostly from the liver, recent evidence in mice and humans indicate that aging and obesity are associated with altered IGFBP-2 levels in white adipocytes. The present study was aimed at determining the mechanisms that control IGFBP-2 expression in mature adipocytes. IGFBP-2 mRNA and protein expression in serum-deprived 3T3-L1 adipocytes were twofold increased by acute insulin treatment. Co-treatments with the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin or the mammalian target of rapamycin (mTOR) inhibitor rapamycin blunted the effects of insulin. Coherently, IGFBP-2 mRNA levels were robustly increased in adipocytes lacking either TSC2 or 4E-BP1. Insulin triggered the recruitment of CAAT/enhancer binding protein α (C/EBPα) to the IGFBP-2 proximal promoter. These findings suggest that insulin upregulates IGFBP-2 expression through a PI3K/mTOR/C/EBPα pathway in white adipocytes.     

Immune consequences of kinase inhibitors in development,undergoing clinical trials and in current use in melanoma treatment

Metastatic malignant melanoma is a frequently fatal cancer. In recent years substantial therapeutic progress has occurred with the development of targeted kinase inhibitors and immunotherapeutics. Targeted therapies often result in rapid clinical benefit however responses are seldom durable. Immune therapies can result in durable disease control but responses may not be immediate. Optimal cancer therapy requires both rapid and durable cancer control and this can likely best be achieved by combining targeted therapies with immunotherapeutics. To achieve this, a detailed understanding of the immune consequences of the various kinase inhibitors, in development, clinical trial and currently used to treat melanoma is required.     

Somatostatin receptors: From signaling to clinical practice

Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.     

Akt isoforms differentially protect against stroke-induced neuronal injury by regulating mTOR activities

Protein kinases Akt1 and Akt3 are considered to be more crucial to brain function than Akt2. We investigated the roles of Akt1 and Akt3 in stroke-induced brain injury and examined their interactions with the Akt/mTOR pathways. Focal ischemia was induced in rats. Lentiviral vectors expressing constitutively active Akt1 and Akt3 (cAkt1 and cAkt3) were injected into the ischemic cortex. Infarct sizes and gene and protein expressions in the Akt/mTOR pathways were evaluated. The results show that Akt1 and Akt3 proteins were degraded as early as 1 hour after stroke, whereas Akt2 proteins remained unchanged until 24 hours after stroke. Lentiviral-mediated overexpression of cAkt1 or cAkt3 reduced neuronal death after in vitro and in vivo ischemia. Interestingly, cAkt3 overexpression resulted in stronger protection than cAkt1 overexpression. Western blot analyses further showed that cAkt3 promoted significantly higher levels of phosphorylated Akt and phosphorylated mTOR than cAkt1. The mTOR inhibitor rapamycin blocked the protective effects of both cAkt1 and cAkt3. In conclusion, Akt isoforms are differentially regulated after stroke and Akt3 offers stronger protection than cAkt1 by maintaining Akt levels and promoting mTOR activity.     

Propofol inhibits biological functions of leukaemia stem and differentiated cells through suppressing Wnt/β-catenin and Akt/mTOR

The biological roles of intravenous anaesthetic propofol in cancer have been shown by various studies using cancer cell lines that represent differentiated cancer cells. However, the activities of propofol in cancer stem cells have not been elucidated. In this work, we examined the effects and mechanisms of propofol on acute myeloid leukaemia (AML) differentiated and CD34⁺CD38⁻ stem cells. We found that propofol inhibited growth, differentiation and self-renewal capabilities of AML stem cells regardless of cellular origin and genetic profiling. In addition, propofol inhibited the growth of AML differentiated cells. Propofol significantly induced apoptosis of AML differentiated but not CD34⁺CD38⁻ stem cells. We further found that propofol significantly augmented the efficacy of AML standard therapeutic drugs. Consistent with the previous findings, we showed that propofol suppressed the Akt/mTOR pathway in AML cells. We also found that propofol inhibited pathways important for stem cell maintenance and self-renewal, such as Wnt/β-catenin. Overexpression of constitutively active Akt partially reversed the inhibitory effects of propofol in AML differentiated cells. Stabilization of β-catenin using genetic and pharmacological approaches also partially rescued the inhibitory effects of propofol in AML differentiated and stem cells. Our work shows that propofol targets leukaemia cells at all stages of development, in a cell type-specific manner. Inhibition of both Akt/mTOR and Wnt/β-catenin is required for the action of propofol in AML. Our findings also highlight the activities of propofol on cancer stem cells.     

Therapeutic effect of a new immunosuppressive agent, everolimus, on interleukin-10 gene-deficient mice with colitis

A limited number of therapeutic strategies are currently available for patients with inflammatory bowel disease (IBD). In particular, the maintenance therapy after remission in Crohn's disease (CD) is not satisfactory and new approaches are needed. Interleukin-10 gene-deficient (IL-10-/-) mice, a well-characterized experimental model of CD, develop severe chronic colitis due to an aberrant Th1 immune response. Everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), a new immunosuppressive reagent, has been used successfully in animal models for heart, liver, lung and kidney transplantation. In the present study, we examined the efficacy of everolimus in the treatment of chronic colitis in an IL-10-/- mouse model. Everolimus was administered orally for a period of 4 weeks to IL-10-/- mice with clinical signs of colitis. The gross and histological appearances of the colon and the numbers, phenotype and cytokine production of lymphocytes were compared with these characteristics in a control group. The 4-week administration of everolimus resulted in a significant decrease in the severity of colitis, together with a significant reduction in the number of CD4+ T cells in the colonic lamina propria as well as IFN-gamma production in colonic lymphocytes. Everolimus treatment of established colitis in IL-10-/- mice ameliorated the colitis, probably as a result of decreasing the number of CD4+ T cells in the colonic mucosa and an associated reduction in IFN-gamma production.     

Design,synthesis, and antitumor evaluation of quinoline‐imidazole derivatives

A series of compounds bearing quinoline‐imidazole ( 8a–e , 9a–e , 10a–e , 11a–e , and 12a–e ) not reported previously were designed and synthesized. The target compounds were evaluated for antitumor activity against A549, PC‐3, HepG2, and MCF‐7 cells by the MTT method, with NVP‐BEZ235 being the positive control. Most compounds showed moderate activity and compound 12a showed the best activity against HepG2, A549, and PC‐3 cells, with half‐maximal inhibitory concentration (IC₅₀) values of 2.42 ± 1.02 µM, 6.29 ± 0.99 µM, and 5.11 ± 1.00 µM, respectively, which was equal to NVP‐BEZ235 (0.54 ± 0.13 µM, 0.36 ± 0.06 µM, 0.20 ± 0.01 µM). Besides, the IC₅₀ value of 12a against the cell line WI‐38 (human fetal lung fibroblasts) was 32.8 ± 1.23 µM, indicating that the target compounds were selective for cancer cells. So, 11a and 12a were evaluated against PI3Kα and mTOR to find out if the compounds acted through the PI3K‐Akt‐mTOR signal transduction pathway. The inhibition ratios to PI3Kα and mTOR were slightly lower than that of NVP‐BEZ235, suggesting there may be some other mechanisms of action. The structure–activity relationships and docking study of 11a and 12a revealed that the latter was superior. Moreover, the target compounds showed better in vitro anticancer activity when the C‐6 of the quinoline ring was replaced by a bromine atom.