Increased expression of MNK1b, the spliced isoform of MNK1, predicts poor prognosis and is associated with triple-negative breast cancer.

MAP kinase interacting kinases (MNKs) modulate the function of oncogene eukaryotic initiation factor 4E (eIF4E) through phosphorylation, which is necessary for oncogenic transformation. MNK1 gives rise to two mRNAs and thus two MNK1 isoforms, named MNK1a and MNK1b. MNK1b, the splice variant of human MNK1a, is constitutively active and independent of upstream MAP kinases. In this study, we have analyzed the expression of both MNK1 isoforms in 69 breast tumor samples and its association with clinicopathologic/prognostic characteristics of breast cancer. MNK1a and MNK1b expression was significantly increased in tumors relative to the corresponding adjacent normal tissue (p < 0.001). In addition, MNK1b overexpression was found in most of the triple-negative tumors and was associated with a shorter overall and disease-free survival time. Overexpression of MNK1b in MDA-MB-231 cells induced an increase in the expression of the MCL1 antiapoptotic protein and promoted proliferation, invasion and colony formation. In conclusion, a high expression level of MNK1b protein could be used as a marker of poor prognosis in breast cancer patients and it could be a therapeutic target in triple-negative tumors.

Characterization of MNK1b DNA Aptamers That Inhibit Proliferation in MDA-MB231 Breast Cancer Cells.

Elevated expression levels of eukaryotic initiation factor 4E (eIF4E) promote cancer development and progression. MAP kinase interacting kinases (MNKs) modulate the function of eIF4E through the phosphorylation that is necessary for oncogenic transformation. Therefore, pharmacologic MNK inhibitors may provide a nontoxic and effective anticancer strategy. MNK1b is a truncated isoform of MNK1a that is active in the absence of stimuli. Using in vitro selection, high-affinity DNA aptamers to MNK1b were selected from a library of ssDNA. Selection was monitored using the enzyme-linked oligonucleotide assay (ELONA), and the selected aptamer population was cloned and sequenced. Four groups of aptamers were identified, and the affinities of one representative for rMNK1b were determined using ELONA and quantitative polymerase chain reaction. Two aptamers, named apMNK2F and apMNK3R, had a lower Kd in the nmol/l range. The secondary structure of the selected aptamers was predicted using mFold, and the QGRS Mapper indicated the presence of potential G-quadruplex structures in both aptamers. The selected aptamers were highly specific against MNK1, showing higher affinity to MNK1b than to MNK1a. Interestingly, both aptamers were able to produce significant translation inhibition and prevent tumor cell proliferation and migration and colony formation in breast cancer cells. These results indicate that MNK1 aptamers have an attractive therapeutic potential.

Progression of liver stiffness predicts clinical events in HIV/HCV-coinfected patients with compensated cirrhosis.

BACKGROUND: Our objective was to assess the predictive value of the changes of liver stiffness (LS) for clinical outcome in HIV/HCV-coinfected patients with compensated liver cirrhosis and a LS value < 40 kPa. METHODS: Prospective cohort of 275 HIV/HCV-coinfected patients with cirrhosis, no previous liver decompensation (LD) and LS < 40 kPa. The time from diagnosis to LD and/or hepatocellular carcinoma (HCC) and the predictors of this outcome were evaluated. Significant progression of LS was defined as an increase ≥ 30 % over the baseline value at any time during the follow-up. RESULTS: After a median (Q1-Q3) follow-up of 32 (20-48) months, 19 (6.9 %, 95 % CI: 3.8 %-9.9 %) patients developed a first LD and/or HCC. At the end of the follow-up, 247 (90 %) patients had undergone a further LS examination. Of them, 77 (31 %) patients had a significant progression of LS. The mean (SD) survival time free of LD and/or HCC was 67 (3) and 77 (1) months in patients with or without significant progression of LS (p = 0.01). Significant progression of LS was an independent predictor of LD and/or HCC (Adjusted Hazard Ratio 4.63; 95 % confidence interval: 1.34-16.02; p = 0.015). CONCLUSIONS: Significant progression of LS is associated with a higher risk of clinical events in HIV/HCV-coinfected patients with compensated cirrhosis and LS < 40 kPa.

eIF4F complex disruption causes protein synthesis inhibition during hypoxia in nerve growth factor (NGF)-differentiated PC12 cells.

Poor oxygenation (hypoxia) influences important physiological and pathological situations, including development, ischemia, stroke and cancer. Hypoxia induces protein synthesis inhibition that is primarily regulated at the level of initiation step. This regulation generally takes place at two stages, the phosphorylation of the subunit α of the eukaryotic initiation factor (eIF) 2 and the inhibition of the eIF4F complex availability by dephosphorylation of the inhibitory protein 4E-BP1 (eukaryotic initiation factor 4E-binding protein 1). The contribution of each of them is mainly dependent of the extent of the oxygen deprivation. We have evaluated the regulation of hypoxia-induced translation inhibition in nerve growth factor (NGF)-differentiated PC12 cells subjected to a low oxygen concentration (0.1%) at several times. Our findings indicate that protein synthesis inhibition occurs primarily by the disruption of eIF4F complex through 4E-BP1 dephosphorylation, which is produced by the inhibition of the mammalian target of rapamycin (mTOR) activity via the activation of REDD1 (regulated in development and DNA damage 1) protein in a hypoxia-inducible factor 1 (HIF1)-dependent manner, as well as the translocation of eIF4E to the nucleus. In addition, this mechanism is reinforced by the increase in 4E-BP1 levels, mainly at prolonged times of hypoxia.

Application of transient elastometry to differentiate mild from moderate to severe liver fibrosis in HIV/HCV co-infected patients.

BACKGROUND/AIMS: Transient elastometry (TE) is accurate for detecting cirrhosis (F=4) in human immunodeficiency virus (HIV)/hepatitis C virus (HCV) co-infected patients. However, this procedure is less precise to differentiate mild (F < or = 1) from moderate to severe (F > or = 2) fibrosis using the cut-off value of 7.2kPa, a level previously proposed by some authors. Because of this, we elaborated and validated cut-off values of liver stiffness (LS) to better discriminate F < or = 1 from F > or = 2 in HIV/HCV co-infected subjects to aid therapy decisions. METHODS: One hundred and ninety-seven co-infected patients with liver biopsy and TE measurement, without prior therapy against HCV infection, were included. RESULTS: To diagnose F < or = 2, a cut-off of 9.0kPa showed a positive predictive value of 87%. To discard F > or = 2, a cut-off of 6.0kPa showed a negative predictive value of 90%. Considering all the patients, 61 (31%) patients yielded LS values < or = 6.0kPa and 81 (41%) patients showed LS values > or = 9.0kPa. There were no severe classification errors as the NPV of L < or = S6.0kPa for F > or = 3 was 100% and the NPV LS > or = 9.0kPa for F=0 was also 100%. CONCLUSIONS: The usefulness of TE can be enhanced using two different cut-off values to identify patients with F < or = 1 and F > or = 2.