Targeting ribosome biogenesis reinforces ERK-dependent senescence in pancreatic cancer.

Pancreatic adenocarcinomas (PDAC) often possess mutations in K-Ras that stimulate the ERK pathway. Aberrantly high ERK activation triggers oncogene-induced senescence, which halts tumor progression. Here we report that low-grade pancreatic intraepithelial neoplasia displays very high levels of phospho-ERK consistent with a senescence response. However, advanced lesions that have circumvented the senescence barrier exhibit lower phospho-ERK levels. Restoring ERK hyperactivation in PDAC using activated RAF leads to ERK-dependent growth arrest with senescence biomarkers. ERK-dependent senescence in PDAC was characterized by a nucleolar stress response including a selective depletion of nucleolar phosphoproteins and intranucleolar foci containing RNA polymerase I designated as senescence-associated nucleolar foci (SANF). Accordingly, combining ribosome biogenesis inhibitors with ERK hyperactivation reinforced the senescence response in PDAC cells. Notably, comparable mechanisms were observed upon treatment with the platinum-based chemotherapy regimen FOLFIRINOX, currently a first-line treatment option for PDAC. We thus suggest that drugs targeting ribosome biogenesis can improve the senescence anticancer response in pancreatic cancer.

Sci-Sat AM: Brachy - 07: Plastic scintillation detector validation for kV dosimetry.

PURPOSE: To characterize the plastic scintillation detectors (PSDs) response in the diagnostic energy range. A fast and adaptable method for real-time dosimetry in superficial x-ray therapy and interventional radiology is proposed. METHOD: A PSD (1 mm diameter and 10 mm long) is coupled to a 5 m long optical fiber. Scintillation photons are guided to a polychromatic photodiode which provides an electrical current proportional to the input light signal. If the incident energy spectrum is known, the dose measured in the PSD's polystyrene sensitive volume can be converted to score dose in any other media such as air, water or soft tissues using the large cavity theory (LCT). A software simulating x-ray tube spectra and filtration has been benchmarked and is used for analysis. The method is confirmed by Monte Carlo simulations. RESULTS: PSDs cannot be assumed energy independent with low-energy photons as a factor 2 has been observed in the energy response between 80 kVp and 150 kVp. When the dose is converted to the desired medium, the PSD's energy dependence is compensated and a 2.1% standard deviation was observed upon the studied energy ranges, which is inside the measurement and calculation uncertainties. Percent depth dose (PDD) measurements are in good agreement with Monte Carlo simulations and results can be improved if the proposed method is applied to compensate beam hardening. CONCLUSION: PSDs present great potential for real-time dose measurements with radiologic photon energy.

Cytotoxicity of fumonisin B1: implication of lipid peroxidation and inhibition of protein and DNA syntheses.

The effects of fumonisin B1 (FB1) from Fusarium moniliforme on lipid peroxidation and protein and DNA syntheses were studied in monkey kidney cells (Vero cells). FB1 was found to be a potent inducer of malondialdehyde (MDA), one of the secondary products formed during lipid peroxidation. At 0.14 microM (0.1 microg/ml), FB1 induced 0.496 +/- 0.1 nmoles of MDA/ mg protein, compared to the control level 0.134 +/- 0.01 nmoles of MDA/mg protein (P < 0.005). No inhibition of protein or DNA synthesis was observed at this concentration of FB1. Inhibition of protein and DNA syntheses was observed at FB1 concentrations > 14 microM (10 microg/ml) with an IC50 of 33 microM for both protein synthesis and DNA synthesis. These results indicate that lipid peroxidation is a very sensitive cellular response to the mycotoxin fumonisin B1 observed at concentrations lower than that required to inhibit cellular synthesis of macromolecules, protein and DNA. This oxidative damage induced by FB1 concentrations encountered in naturally contaminated foodstuffs and feed might lead to mutagenicity and genotoxicity.

The effect of cold acclimation and deacclimation on cold tolerance, trehalose and free amino acid levels in Sitophilus granarius and Cryptolestes ferrugineus (Coleoptera).

Canadian and French laboratory strains of Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) were cold acclimated by placing adults at 15, 10 and 5 degrees C successively for 2wk at each temperature before deacclimating them for 1wk at 30 degrees C. Unacclimated S. granarius had an LT(50) (lethal time for 50% of the population) of 12days at 0 degrees C compared with 40days after the full cold acclimation. At -10 degrees C, unacclimated C. ferrugineus had an LT(50) of 1.4days compared with 24days after the full acclimation. Cold acclimation was lost within a week after returning insects to 30 degrees C. Trehalose, as well as the amino acids proline, asparagine, glutamic acid and lysine were higher in cold acclimated insects for both species. For S. granarius, glutamine was higher in cold acclimated insects and isoleucine, ethanolamine and phosphoethanolamine, a precursor of phospholipids, were lower in cold acclimated insects. For C. ferrugineus, alanine, aspartic acid, threonine, valine, isoleucine, leucine, phenylalanine and phosphoethanolamine were higher in cold acclimated insects. For both species tyrosine was lower in cold acclimated insects. There were small but significant differences between Canadian and French strains of S. granarius, with the Canadian strain being more cold hardy and having higher levels of trehalose. There were small but significant differences between male and female S. granarius, with males being more cold hardy and having higher levels of proline, asparagine and glutamic acid. In conclusion, high levels of trehalose and proline were correlated with cold tolerance, as seen in several other insects. However, correlation does not prove that these compounds are responsible for cold tolerance, and we outline further tests that could demonstrate a causal relationship between trehalose and proline and cold tolerance.

Analysis for alpha-amylase isoenzymes by automated isoelectric focusing.

We describe the fractionation of alpha-amylase (EC 3.2.1.1) isoenzymes by use of the Pharmacia "Phastsystem" electrophoresis apparatus. The separation is done by isoelectric focusing on "Phastgel IEF 5-8." A complete run, including staining, takes 4 h and can easily resolve eight isoenzymes. Samples can be analyzed in a routine laboratory with use of conventional reagents.

Comparison of three methods for the elimination of the labile fraction of HbA1.

Three different procedures were used to remove the "labile" fraction in the chromatographic quantitation of hemoglobin A1 (HbA1) by a minicolumn assay: (a) preincubation of the erythrocytes at 37 degrees C in isotonic saline for 4 h, (b) preincubation in the presence of semicarbazide-aniline at pH 5.0 for 30 min, and (c) preincubation in acetate buffer at pH 5.5 for 30 min. The results show that the two latter methods are not only more rapid but are also slightly more effective. The use of the acetate buffer is preferred because this reagent is more easily prepared and also because the presence of semicarbazide and aniline did not markedly accelerate the dissociation of Hb pre-A1c at pH 5.5. The procedure relies simply on the greater instability of Schiff base in acidic solution. There is a significant correlation between the "labile" fraction and the plasma glucose concentration at sampling time. The results support the view that the elimination of the "labile" precursor is essential to preserve the utility of the assay.

Light chain disease and massive proteinuria.

We describe the case of a 64-year-old man with lambda type light chain disease, in whom panhypogammaglobulinemia was associated with anemia, massive Bence Jones proteinuria (24.6 g/L), and renal failure. Lambda type light chains were present in the serum.

Glycated hemoglobin in uremic patients as measured by affinity and ion-exchange chromatography.

We estimated glycated ("glycosylated") hemoglobin in erythrocytes of hemodialyzed uremic patients by the aminophenylboronic acid affinity-chromatographic method and by an ion-exchange chromatographic method. As expected, apparent HbA1 concentrations were above normal in the uremic patients, owing to interference by the carbamylated hemoglobin. However, there was no significant difference between values for uremic and normal subjects when glycated hemoglobin was measured by the affinity method. Evidently it is unaffected by the presence of hemoglobin species modified by reactants not displaying a cis-1,2-diol group, such as carbamylated hemoglobin. For this reason it is preferable to the ion-exchange chromatographic method for accurate measurement of glycated hemoglobin.