Mamatha Bhat

eIF4E/4E-BP Ratio Predicts the Efficacy of mTOR Targeted Therapies

Active-site mTOR inhibitors (asTORi) hold great promise for targeting dysregulated mTOR signaling in cancer. Because of the multifaceted nature of mTORC1 signaling, identification of reliable biomarkers for the sensitivity of tumors to asTORi is imperative for their clinical implementation. Here, we show that cancer cells acquire resistance to asTORi by downregulating eukaryotic translation initiation factor (eIF4E)-binding proteins (4E-BPs-EIF4EBP1, EIF4EBP2). Loss of 4E-BPs or overexpression of eIF4E renders neoplastic growth and translation of tumor-promoting mRNAs refractory to mTOR inhibition. Conversely, moderate depletion of eIF4E augments the anti-neoplastic effects of asTORi. The anti-proliferative effect of asTORi in vitro and in vivo is therefore significantly influenced by perturbations in eIF4E/4E-BP stoichiometry, whereby an increase in the eIF4E/4E-BP ratio dramatically limits the sensitivity of cancer cells to asTORi. We propose that the eIF4E/4E-BP ratio, rather than their individual protein levels or solely their phosphorylation status, should be considered as a paramount predictive marker for forecasting the clinical therapeutic response to mTOR inhibitors.

The mTOR pathway in hepatic malignancies

The mechanistic/mammalian target of rapamycin (mTOR) pathway plays a critical role in cellular metabolism, growth, and proliferation and has been evaluated as a target for therapy in various malignancies. The mTOR pathway is a major tumor‐initiating pathway in hepatocellular carcinoma, with up‐regulation seen in up to 50% of tumors. Metformin, which represses mTOR signaling by activating adenosine monophosphate–activated protein kinase, has been shown to decrease liver carcinogenesis in population studies. mTOR inhibitors such as everolimus have been evaluated as adjunctive chemotherapy with some success, although efficacy has been limited by the lack of complete mTOR pathway inhibition. The active site mTOR inhibitors hold greater promise, given that they offer complete mTOR suppression. There is also evidence of mTOR pathway activation in cholangiocarcinoma, although its biological significance in initiating and promoting tumor progression remains ambiguous. This review provides an overview of the complex biochemistry behind the mTOR pathway and its role in carcinogenesis, especially as it pertains to hepatic malignancies. (HEPATOLOGY 2013;58:810–818)

Phenotypic and Genotypic Characteristics of Inflammatory Bowel Disease in French Canadians: Comparison With a Large North American Repository

OBJECTIVES:Phenotype characteristics of inflammatory bowel disease (IBD) may differ significantly among ethnic subpopulations. The aim of this study was to characterize the IBD phenotype in French Canadians, the most prominent founder population in North America.METHODS:Using well-characterized phenotype data in the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)-IBD Genetics Consortium repository on patients with IBD, we compared phenotypic characteristics of 202 French Canadians with those of 1,287 other Caucasian patients. These included diagnosis, anatomical location, disease behavior, extraintestinal manifestations, surgical history, and family history of IBD.RESULTS:French-Canadian patients with Crohns disease (CD) were less likely to have stricturing disease (11 vs. 21%, P=0.005; odds ratio (OR): 0.45, 95% confidence interval (95% CI): 0.24–0.85). Using a stringent definition of ethnicity (three out of four grandparents being French Canadians, as opposed to self-report, n=148), French Canadians had a tendency toward developing fistulizing CD (37 vs. 28%, P=0.07), and there was an increased prevalence of sacroiliitis among those with IBD (4 vs. 2%, P=0.045). Among French Canadians, the numbers of current smokers in CD (40 vs. 25%, P=0.006) and former smokers in ulcerative colitis (UC) (35 vs. 20%, P=0.03) were significantly higher. The prevalence of one of the three main variants of nucleotide-binding oligomerization domain containing 2 (NOD2) single-nucleotide polymorphisms (SNPs) among French-Canadian CD patients was 43.2%. The 3020insC SNP correlated with small bowel disease in French Canadians (75 vs. 0%, P=0.006).CONCLUSIONS:French Canadians show an IBD phenotype profile distinct from other Caucasian IBD populations, with an accentuated association between smoking status and IBD. This unique profile may have implications regarding the need for a different approach to the management of IBD in this population.

Antioxidant Therapy in Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) affects up to 3% of the North American population. It occurs as a manifestation of the insulin-resistant state and oxidative stress is thought to be a key component of its pathophysiology. Exercise and diet, which are the mainstay of therapy, are difficult to achieve and maintain with a disappointing long-term compliance record. There is growing literature on the potential for antioxidant therapy. The recent literature strongly suggests that vitamin E supplementation and other putative free radical scavengers and/or antioxidants are beneficial in improving biochemical and histological parameters in NASH.

Effectiveness of disseminating consensus management recommendations for ulcer bleeding: a cluster randomized trial

Background: International guidelines for the management of nonvariceal upper gastrointestinal bleeding have not been widely adopted in clinical practice. We sought to determine whether a national, multifaceted intervention could improve adherence to guidelines, especially for patients at high risk of nonvariceal upper gastrointestinal bleeding. Methods: In this randomized trial, we stratified hospitals by region and size and allocated sites to either the control or experimental group. Health care workers in the experimental group were given published guidelines, generic algorithms, stratification scoring systems and written reminders and attended multidisciplinary guideline education groups and case-based workshops. These interventions were implemented over a 12-month period after randomization, with performance feedback and benchmarking. The primary outcome of adherence rates to key guidelines in endoscopic and pharmacologic management, determined by chart review, was adjusted according to site characteristics and possible within-site dependencies. We also report the rates of adherence to other recommendations. Results: Forty-three sites were randomized to the experimental (n = 21) or control (n = 22) groups. In our primary analysis, we compared patients before (experimental group: n = 402 patients; control group: n = 424 patients) and after (experimental group: n = 361 patients; control group: n = 389 patients) intervention. Patient-level analysis revealed no significant difference in adherence rates to the guidelines after the intervention (experimental group: 9.8%; control group: 4.8%; p = 0.99) after adjustment for the rate of adherence before the intervention (experimental group: 13.2%; control group: 7.1%). The adherence rates to other guidelines were similar and decreased over time, varying between 5% and 93%. Interpretation: This national knowledge translation–based trial suggests poor adherence to guidelines on nonvariceal upper gastrointestinal bleeding. Adherence was not improved by an educational intervention, which highlights both the complexity and poor predictability of attempting to alter the behaviour of health care providers (Trial registration: ClinicalTrials.gov, no. MCT-88113).

Randomised clinical trial: MRCP-first vs. ERCP-first approach in patients with suspected biliary obstruction due to bile duct stones

The preferred initial investigation with either magnetic resonance (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP) in patients with suspected biliary obstruction remains controversial in many clinical settings.

Hepatitis B and the infected health care worker: public safety at what cost?

Public safety and the right of the health care worker to practise without prejudice based on underlying illness may be at odds for those affected by the hepatitis B virus (HBV). Nevertheless, HBV does not preclude entry into a health care profession, and the risk of transmission from health care worker to patient is not uniform across the spectrum of health care fields. In the present article, the authors present an overview of the literature regarding transmission of HBV from the health care worker to the patient, and the current recommendations that vary from province to province within Canada. The establishment of national guidelines to standardize monitoring of HBV infection among health care workers would improve health care workplace safety and patient care.

Metformin does not improve survival in patients with hepatocellular carcinoma

AIM To assess whether metformin, which has a chemopreventive effect in chronic liver disease, has any chemotherapeutic effect in hepatocellular carcinoma. METHODS This was a retrospective study of 701 patients with newly diagnosed hepatocellular carcinoma (HCC) seen between January 2005 and June 2011 at Mayo Clinic, Rochester, Minnesota. This patient cohort was a part of the global HCC BRIDGE study, which is a large longitudinal study of HCC determining the real-world experience of HCC characteristics, management and patient outcomes. We defined significant metformin exposure as continuation of this agent at least 90 d beyond diagnosis of HCC, and compared survival of diabetic patients on metformin to diabetic patients not on metformin and non-diabetics. RESULTS Our cohort was 72.9% male, with a mean ± SD age of 62.6 ± 12.3 years. The most common etiologies of liver disease were hepatitis C (34%), alcoholic liver disease (29%), fatty liver disease (15%) and hepatitis B (9%). By univariate analysis, using diabetics not on metformin as the reference group, diabetic patients with HCC on metformin had no survival advantage, with a HR (95%CI) of 1.0 (0.8-1.3). Non-diabetic HCC patients also did not appear to have a survival advantage as compared to diabetic HCC patients not on metformin, as demonstrated by a HR (95%CI) of 1.1 (0.7-1.7). Diabetics on metformin beyond 90 d after HCC diagnosis had a longer median survival at 34.2 mo, as compared to 25.5 mo among diabetic patients who were not on metformin or had discontinued metformin within 90 d after HCC diagnosis. This finding was likely due to potential survival bias among those who lived long enough to receive metformin. CONCLUSION Although the literature suggests a chemotherapeutic effect in other malignancies, our study demonstrates no survival benefit to the use of metformin in diabetic patients with HCC.

Prediction and prevention of upper gastrointestinal bleeding after cardiac surgery: a case control study.

BACKGROUND Gastrointestinal (GI) complications of cardiovascular surgery, particularly bleeding, occur frequently. OBJECTIVE To determine factors that predict upper GI bleeding (UGIB) after cardiac surgery to improve prognostication and, thus, outcomes. METHODS The present case-control study reviewed institutional records spanning 2002 to 2005 for consecutive patients who developed in-hospital UGIB following cardiovascular surgery. Each case was matched to two to three controls for age, sex and date of hospital admission. Demographics, pharmacotherapy (including use of in-hospital acid suppression), endoscopic findings and outcomes were recorded. After adjustment for possible confounders, including Parsonnet score and demographic parameters, conditional logistic regression analysis identified independent significant predictors of the subsequent development of UGIB. RESULTS The study population consisted of 131 cases (mean [± SD] age 68.8±10.2 years, 69.5% male, mean Parsonnet score 24.6±14.2) and 387 matched controls (mean age 68.8±10.8 years, 70.0% male, mean Parsonnet score 20.9±14.2). UGIB events occurred a mean of 10.3±7.7 days after cardiac surgery. Duration of mechanical ventilation (OR 3.01 [95% CI 1.44 to 6.28]), elevation of international normalized ratio (OR 1.91 [95% CI 1.31 to 2.78]) and occurrence of Clostridium difficile colitis before bleeding (OR 3.15 [95% CI 1.19 to 8.36]) were independent risk factors. Use of histamine type 2 receptor antagonists (H2RAs) (OR 0.65 [95% CI 0.38 to 1.12]) or proton pump inhibitors (PPIs) (OR 0.60 [95% CI 0.27 to 1.32]) demonstrated trends toward protecting against UGIB after cardiac surgery. CONCLUSIONS GI bleeding events occurred approximately 10 days after cardiac surgery in patients with a complicated postoperative course. Significant predictors of subsequent bleeding included increased duration of mechanical ventilation and elevation of international normalized ratio; routine acid suppression with PPIs should be considered in such patients. C difficile colitis also significantly predicted UGIB, and H2RAs should be considered for acid suppression. Neither H2RAs nor PPIs were effective in preventing UGIB, although the small number of patients limits definitive conclusions regarding the role of acid suppression.

Metformin requires 4E-BPs to induce apoptosis and repress translation of Mcl-1 in hepatocellular carcinoma cells

Metformin inhibits the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, which is frequently upregulated in hepatocellular carcinoma (HCC). Metformin has also been shown to induce apoptosis in this cancer. Here, we investigate whether metformin-induced apoptosis in HCC is mediated by the downstream mTORC1 effectors eukaryotic initiation factor 4E and (eIF4E)-binding proteins (4E-BPs). Further, we ask whether changes in 4E-BPs activity during metformin treatment negatively regulate translation of the anti-apoptotic myeloid cell leukemia 1 (Mcl-1) mRNA. A genetic HCC mouse model was employed to assess the ability of metformin to reduce tumor formation, induce apoptosis, and control 4E-BP1 activation and Mcl-1 protein expression. In parallel, the HCC cell line Huh7 was transduced with scrambled shRNA (control) or shRNAs targeting 4E-BP1 and 4E-BP2 (4E-BP knock-down (KD)) to measure differences in mRNA translation, apoptosis, and Mcl-1 protein expression after metformin treatment. In addition, immunohistochemical staining of eIF4E and 4E-BP1 protein levels was addressed in a HCC patient tissue microarray. We found that metformin decreased HCC tumor burden, and tumor tissues showed elevated apoptosis with reduced Mcl-1 and phosphorylated 4E-BP1 protein levels. In control but not 4E-BP KD Huh7 cells, metformin induced apoptosis and repressed Mcl-1 mRNA translation and protein levels. Immunostaining of HCC patient tumor tissues revealed a varying ratio of eIF4E/4E-BP1 expression. Our results propose that metformin induces apoptosis in mouse and cellular models of HCC through activation of 4E-BPs, thus tumors with elevated expression of 4E-BPs may display improved clinical chemopreventive benefit of metformin.