SAMHD1 expression contributes to doxorubicin resistance and predicts survival outcomes in diffuse large B-cell lymphoma patients

Diffuse large B-cell lymphoma (DLBCL) is a commonly diagnosed, aggressive non-Hodgkin's lymphoma. While R-CHOP chemoimmunotherapy is potentially curative, about 40% of DLBCL patients will fail, highlighting the need to identify biomarkers to optimize management. SAMHD1 has a dNTPase-independent role in promoting resection to facilitate DNA double-strand break (DSB) repair by homologous recombination. We evaluated the relationship of SAMHD1 levels with sensitivity to DSB-sensitizing agents in DLBCL cells and the association of SAMHD1 expression with clinical outcomes in 79 DLBCL patients treated with definitive therapy and an independent cohort dataset of 234 DLBCL patients. Low SAMHD1 expression, Vpx-mediated, or siRNA-mediated degradation/depletion in DLBCL cells was associated with greater sensitivity to doxorubicin and PARP inhibitors. On Kaplan-Meier log-rank survival analysis, low SAMHD1 expression was associated with improved overall survival (OS), which on subset analysis remained significant only in patients with advanced stage (III-IV) and moderate to high risk (2-5 International Prognostic Index (IPI)). The association of low SAMHD1 expression with improved OS remained significant on multivariate analysis independent of other adverse factors, including IPI, and was validated in an independent cohort. Our findings suggest that SAMHD1 expression mediates doxorubicin resistance and may be an important prognostic biomarker in advanced, higher-risk DLBCL patients.

DNA-PK is activated by SIRT2 deacetylation to promote DNA double-strand break repair by non-homologous end joining

DNA-dependent protein kinase (DNA-PK) plays a critical role in non-homologous end joining (NHEJ), the predominant pathway that repairs DNA double-strand breaks (DSB) in response to ionizing radiation (IR) to govern genome integrity. The interaction of the catalytic subunit of DNA-PK (DNA-PKcs) with the Ku70/Ku80 heterodimer on DSBs leads to DNA-PK activation; however, it is not known if upstream signaling events govern this activation. Here, we reveal a regulatory step governing DNA-PK activation by SIRT2 deacetylation, which facilitates DNA-PKcs localization to DSBs and interaction with Ku, thereby promoting DSB repair by NHEJ. SIRT2 deacetylase activity governs cellular resistance to DSB-inducing agents and promotes NHEJ. SIRT2 furthermore interacts with and deacetylates DNA-PKcs in response to IR. SIRT2 deacetylase activity facilitates DNA-PKcs interaction with Ku and localization to DSBs and promotes DNA-PK activation and phosphorylation of downstream NHEJ substrates. Moreover, targeting SIRT2 with AGK2, a SIRT2-specific inhibitor, augments the efficacy of IR in cancer cells and tumors. Our findings define a regulatory step for DNA-PK activation by SIRT2-mediated deacetylation, elucidating a critical upstream signaling event initiating the repair of DSBs by NHEJ. Furthermore, our data suggest that SIRT2 inhibition may be a promising rationale-driven therapeutic strategy for increasing the effectiveness of radiation therapy.

Development and evaluation of an observational Back-Exposure Sampling Tool (Back-EST) for work-related back injury risk factors

We developed and evaluated an observational Back-Exposure Sampling Tool. A literature review suggested 53 exposure variables; these were reduced to 20 following field trials. Kappas for agreement beyond chance between six observers assessing exposures in 72 photos ranged from 0.21 to 1.0, with the highest values for posture type, trunk angle, manual materials handling, hands on item, and load weight. Intraclass correlations for agreement between pairs observing 17 workers once per minute for a full-shift were >0.74 for most postural, trunk angle, and manual materials handling variables. In validity testing, the proportions of shifts in flexion/extension and lateral bending observed for 169 full-shifts were compared to inclinometer measurements. Pearson correlations were 0.42 for 45-60 degrees flexion and 0.9 for >60 degrees flexion, but only 0.11-0.19 for lateral bending and trunk flexion less than 45 degrees . When lower flexion angles were collapsed to include trunk extension, correlations increased to >0.5.

Susceptibilities of Eikenella corrodens, Prevotella intermedia, and Prevotella nigrescens clinical isolates to amoxicillin and tetracycline

The AB Biodisk Etest showed that 106 (100%) and 98 (92%) isolates of Eikenella corrodens were susceptible to amoxicillin and tetracycline, respectively. Twenty-three (68%) Prevotella intermedia isolates and 14 (67%) Prevotella nigrescens isolates were susceptible to amoxicillin. Seventy-nine percent of the P. intermedia isolates and 67% of the P. nigrescens isolates were susceptible to tetracycline. A higher percentage of beta-lactamase-producing isolates of P. intermedia and P. nigrescens were identified with selective agar containing amoxicillin than with nonselective agar.

Dose effect relationship of reviparin in chronic hemodialysis: a crossover study versus nadroparin

Low molecular weight heparins (LMWHs) are used for prevention of clotting in the dialysis circuit. The aim of this trial was to define the optimal dose of a new LMWH and to test the efficiency of a single dose at the start of the session. Fifteen patients were treated according to a double blind and crossover design during 4 blocks of 5 consecutive reviparin doses assigned randomly as 50, 60, 70, 85, and 100 IU anti-Xa/kg. Assessment was carried out on screening of fibrin rings or clots in the arterial and venous air traps and on visual detection of fiber in the dialyzer after rinsing. These clinical results were compared to plasmatic anti-Xa activity and thrombin-antithrombin (TAT) complex generation. A standard dose of 70 IU anti-Xa/kg of nadroparin was used as the control. After a bolus of 50 to 100 IU anti-Xa/kg, the occurrence of fibrin rings and clots in the air traps was dependent on three factors: dose of LMWH, time of the session, and patient status. A bolus of 85 IU anti-Xa/kg of reviparin was effective and safe for sessions of 4 h. For this dose, plasmatic anti-Xa activity was 0.96 +/- 0.28 IU/ml at Hour 2 and 0.82 +/- 0.22 IU/ml at Hour 4. TAT complexes are good markers of the activation of the coagulation. They did not increase during a 4 h session after a reviparin bolus of 100 IU/kg. For the same LMWH dose, the trial shows a great variability of the clinical effect and anti-Xa activities from one patient to another. A single dose of 85 IU anti-Xa/kg of reviparin can be used at the start of the dialysis session as a loading dose. We advise adapting the dose during the subsequent sessions according to the appearance of the blood circuit. The benefit of monitoring anti-Xa activity and TAT complexes could be tested in a further trial.

Biocompatibility of haemodialysis membranes: haemodialysis-related leukotriene B4 and C4 generation. France

The aim of our study was (1) to verify whether haemodialysis (HD) with cuprophane (CUP) and polyacrylonitrile (PAN) membranes is associated with the release of vasoactive leukotriene (LT) C4 and chemotactic LTB4 and (2) to analyse the respective roles of lipoxygenase and cyclo-oxygenase metabolites of arachidonic acid in membrane bio-incompatibility. The investigation was performed in 10 uremic patients using hollow-fibre dialysers and dialysed successively, in random order, with CUP and PAN membranes. The arterial and venous (from dialyser) blood was sampled for the measurement of biochemical parameters, plasma LTC4, LTB4 and prostaglandins (PG) 6-keto-F1 alpha, E2, F2 alpha and thromboxane B2 before and after 15, 30 and 240 min of HD. Eicosanoids were measured by RIA after prior extraction and HPLC separation.

RESULTS

CUP HD was associated with a marked early leukopenia and a delayed decrease in blood pO2. Simultaneously, plasma LTB4 and LTC4 increased significantly in arterial blood after 30 min of HD and in venous blood at the end of session of 240 min. Cyclo-oxygenase metabolites increased as well, but nonsignificantly, with a maximum at the end of HD. PAN HD did not significantly change white blood cell count, pO2, or plasma eicosanoid levels.

CONCLUSION

CUP membranes stimulate the release of proinflammatory and vasoactive LTB4 and LTC4. PAN membrane haemodialysis is without such side effects. The release of LTs may be an additional valuable marker of membrane bioincompatibility.

Influence of uremia on polymorphonuclear leukocytes oxidative metabolism in end-stage renal disease and dialyzed patients

The oxygen (O2) consumption, and superoxide anion (O2-.) and hydrogen peroxide (H2O2) production by polymorphonuclear leukocytes (PMNs) were investigated in 5 end-stage renal disease patients, before and after the 1st, 4th and 10th dialysis sessions. Resting values of O2-. production and O2 consumption were not significantly different from values for PMNs from normal subjects. After stimulation by opsonized zymosan or phorbol myristate acetate, the three parameters measured were significantly (p less than 0.001) enhanced in comparison with healthy control values. Cross-incubation studies showed a lack of effect of patient plasma on O2-. production by stimulated control cells: PMN oxidative metabolism would therefore appear to be increased in these patients. The anomalies observed probably arise via a mechanism involving a cellular dysfunction resulting from the renal disease, rather than from the presence of a plasma factor.