Sumi Sinha

A Diverse Array of Cancer-Associated MTOR Mutations Are Hyperactivating and Can Predict Rapamycin Sensitivity

Genes encoding components of the PI3K-AKT-mTOR signaling axis are frequently mutated in cancer, but few mutations have been characterized in MTOR, the gene encoding the mTOR kinase. Using publicly available tumor genome sequencing data, we generated a comprehensive catalog of mTOR pathway mutations in cancer, identifying 33 MTOR mutations that confer pathway hyperactivation. The mutations cluster in six distinct regions in the C-terminal half of mTOR and occur in multiple cancer types, with one cluster particularly prominent in kidney cancer. The activating mutations do not affect mTOR complex assembly, but a subset reduces binding to the mTOR inhibitor DEPTOR. mTOR complex 1 (mTORC1) signaling in cells expressing various activating mutations remains sensitive to pharmacologic mTOR inhibition, but is partially resistant to nutrient deprivation. Finally, cancer cell lines with hyperactivating MTOR mutations display heightened sensitivity to rapamycin both in culture and in vivo xenografts, suggesting that such mutations confer mTOR pathway dependency.

Effect of dietary sodium on vasoconstriction and eNOS-mediated vascular relaxation in caveolin-1-deficient mice

Changes in dietary sodium intake are associated with changes in vascular volume and reactivity that may be mediated, in part, by alterations in endothelial nitric oxide synthase (eNOS) activity. Caveolin-1 (Cav-1), a transmembrane anchoring protein in the plasma membrane caveolae, binds eNOS and limits its translocation and activation. To test the hypothesis that endothelial Cav-1 participates in the dietary sodium-mediated effects on vascular function, we assessed vascular responses and nitric oxide (NO)-mediated mechanisms of vascular relaxation in Cav-1 knockout mice (Cav-1-/-) and wild-type control mice (WT; Cav-1+/+) placed on a high-salt (HS; 4% NaCl) or low-salt (LS; 0.08% NaCl) diet for 16 days. After the systolic blood pressure was measured, the thoracic aorta was isolated for measurement of vascular reactivity and NO production, and the heart was used for measurement of eNOS expression and/or activity. The blood pressure was elevated in HS mice treated with NG-nitro-l-arginine methyl ester and more so in Cav-1-/- than WT mice and was significantly reduced during the LS diet. Phenylephrine caused vascular contraction that was significantly reduced in Cav-1-/- (maximum 0.25 +/- 0.06 g/mg) compared with WT (0.75 +/- 0.22 g/mg) on the HS diet, and the differences were eliminated with the LS diet. Also, vascular contraction in response to membrane depolarization by high KCl (96 mM) was reduced in Cav-1-/- (0.27 +/- 0.05 g/mg) compared with WT mice (0.53 +/- 0.12 g/mg) on the HS diet, suggesting that the reduced vascular contraction is not limited to a particular receptor. Acetylcholine (10(-5) M) caused aortic relaxation in WT mice on HS (23.6 +/- 3.5%) and LS (23.7 +/- 5.5%) that was enhanced in Cav-1-/- HS (72.6 +/- 6.1%) and more so in Cav-1-/- LS mice (93.6 +/- 3.5%). RT-PCR analysis indicated increased eNOS mRNA expression in the aorta and heart, and Western blots indicated increased total eNOS and phosphorylated eNOS in the heart of Cav-1-/- compared with WT mice on the HS diet, and the genotypic differences were less apparent during the LS diet. Thus Cav-1 deficiency during the HS diet is associated with decreased vasoconstriction, increased vascular relaxation, and increased eNOS expression and activity, and these effects are altered during the LS diet. The data support the hypothesis that endothelial Cav-1, likely through an effect on eNOS activity, plays a prominent role in the regulation of vascular function during substantial changes in dietary sodium intake.

Roles of Major Facilitator Superfamily Transporters in Phosphate Response in Drosophila

The major facilitator superfamily (MFS) transporter Pho84 and the type III transporter Pho89 are responsible for metabolic effects of inorganic phosphate in yeast. While the Pho89 ortholog Pit1 was also shown to be involved in phosphate-activated MAPK in mammalian cells, it is currently unknown, whether orthologs of Pho84 have a role in phosphate-sensing in metazoan species. We show here that the activation of MAPK by phosphate observed in mammals is conserved in Drosophila cells, and used this assay to characterize the roles of putative phosphate transporters. Surprisingly, while we found that RNAi-mediated knockdown of the fly Pho89 ortholog dPit had little effect on the activation of MAPK in Drosophila S2R+ cells by phosphate, two Pho84/SLC17A1–9 MFS orthologs (MFS10 and MFS13) specifically inhibited this response. Further, using a Xenopus oocyte assay, we show that MSF13 mediates uptake of [33P]-orthophosphate in a sodium-dependent fashion. Consistent with a role in phosphate physiology, MSF13 is expressed highest in the Drosophila crop, midgut, Malpighian tubule, and hindgut. Altogether, our findings provide the first evidence that Pho84 orthologs mediate cellular effects of phosphate in metazoan cells. Finally, while phosphate is essential for Drosophila larval development, loss of MFS13 activity is compatible with viability indicating redundancy at the levels of the transporters.

Genetic Determinants of Phosphate Response in Drosophila

Phosphate is required for many important cellular processes and having too little phosphate or too much can cause disease and reduce life span in humans. However, the mechanisms underlying homeostatic control of extracellular phosphate levels and cellular effects of phosphate are poorly understood. Here, we establish Drosophila melanogaster as a model system for the study of phosphate effects. We found that Drosophila larval development depends on the availability of phosphate in the medium. Conversely, life span is reduced when adult flies are cultured on high phosphate medium or when hemolymph phosphate is increased in flies with impaired Malpighian tubules. In addition, RNAi-mediated inhibition of MAPK-signaling by knockdown of Ras85D, phl/D-Raf or Dsor1/MEK affects larval development, adult life span and hemolymph phosphate, suggesting that some in vivo effects involve activation of this signaling pathway by phosphate. To identify novel genetic determinants of phosphate responses, we used Drosophila hemocyte-like cultured cells (S2R+) to perform a genome-wide RNAi screen using MAPK activation as the readout. We identified a number of candidate genes potentially important for the cellular response to phosphate. Evaluation of 51 genes in live flies revealed some that affect larval development, adult life span and hemolymph phosphate levels.

Androgen deprivation therapy for prostate cancer and dementia risk: a systematic review and meta-analysis

Background:Androgen deprivation therapy (ADT) to treat prostate cancer may be associated with an increased risk of dementia, but existing studies have shown conflicting results. Here we synthesize the literature on the association of ADT for the treatment of prostate cancer with dementia risk.Methods:We conducted a systematic review of articles reporting the outcome of dementia among individuals with prostate cancer in those exposed to ADT versus a lesser-exposed comparison group (for example, ADT versus no-ADT; continuous versus intermittent ADT) using PubMed (1966–present), Web of Science (1945–present), Embase (1966–present) and PsycINFO (1806–present). The search was undertaken on 4 December 2016 by two authors. We meta-analyzed studies reporting an effect estimate and controlling for confounding. Random- or fixed-effects meta-analytic models were used in the presence or absence of heterogeneity per the I2 statistic, respectively. Small study effects were evaluated using Egger and Begg’s tests.Results:Nine studies were included in the systematic review. Seven studies reported an adjusted effect estimate for dementia risk. A random-effects meta-analysis of studies reporting any dementia outcome, which included 50 541 individuals, showed an increased risk of dementia among ADT users (hazard ratio (HR), 1.47; 95% confidence interval (CI), 1.08–2.00; P=0.02). We separately meta-analyzed studies reporting all-cause dementia (HR, 1.46; 95% CI, 1.05–2.02; P<0.001) and Alzheimer’s disease (HR, 1.25; 95% CI, 0.99–1.57; P=0.06). There was no evidence of bias from small study effects (Egger, P=0.19; Begg, P=1.00).Conclusion:The currently available combined evidence suggests that ADT in the treatment of prostate cancer may be associated with an increased dementia risk. The potential for neurocognitive deficits secondary to ADT should be discussed with patients and evaluated prospectively.

Simultaneous Bilateral Knee Arthroplasty in Octogenarians: Can It Be Safe and Effective?

Simultaneous bilateral knee arthroplasty (SBTKA) in octogenarians is controversial. Our purpose was to review the outcomes of octogenarians undergoing SBTKA. All patients greater than 80 years of age who underwent SBTKA by a single surgeon were retrospectively evaluated. Fifty-six patients with an average age of 82.5 years were identified. Twelve postoperative complications occurred. Three were serious; two non-fatal PEs and one wound debridement. Minor complications included UTI, decubitus ulcer, DVT, confusion, transfusion reaction and ileus. Average postoperative survival was 7.4 years. No deaths occurred within 30 days postoperatively. Simultaneous bilateral total knee arthroplasty can be a safe and effective option for octogenarians. Complications and mortality are not higher for SBTKA compared to UTKA in this population.

Association of androgen deprivation therapy and depression in the treatment of prostate cancer: A systematic review and meta-analysis

BACKGROUND There is increasing evidence that androgen deprivation therapy (ADT) may be associated with depression. Existing studies have shown conflicting results. METHODS PubMed, Web of Science, Embase, and PsycINFO were queried on April 5, 2017. Eligible studies were in English and reported depression among individuals with prostate cancer exposed to a course of ADT vs. a lesser-exposed group (e.g., any-ADT vs. no ADT and continuous ADT vs. intermittent ADT). We used the MOOSE statement guidelines and the Cochrane Review Groups data extraction template. Study quality was evaluated by Newcastle-Ottawa Scale criteria. We conducted a random-effects meta-analysis to calculate summary statistic risk ratios (RRs) and 95% CIs. Heterogeneity was quantified using the I2 statistic and prespecified subgroup analysis. Small study effects were evaluated using Begg and Egger statistics. RESULTS A total of 1,128 studies were initially identified and evaluated. A meta-analysis of 18 studies among 168,756 individuals found that ADT use conferred a 41% increased risk of depression (RR = 1.41; 95% CI: 1.18-1.70; P<0.001). We found a consistent strong statistically significant association when limiting our analysis to studies in localized disease (RR = 1.85; 95% CI: 1.20-2.85; P = 0.005) and those using a clinical diagnosis of depression (RR = 1.19; 95% CI: 1.08-1.32; P = 0.001). We did not find an association for continuous ADT with depression risk compared to intermittent ADT (RR = 1.00; 95% CI: 0.50-1.99; P = 0.992). There was no statistically significant evidence of small study effects. Statistically significant heterogeneity in the full analysis (I2 = 80%; 95% CI: 69-87; P<0.001) resolved when examining studies using a clinical diagnosis of depression (I2 = 16%; 95% CI: 0-60; P = 0.310). CONCLUSION The currently available evidence suggests that ADT in the treatment of prostate cancer is associated with an increased risk of depression.

Perioperative Deep Vein Thrombosis Risk Stratification: A Comparative Analysis of Free and Pedicled Flap Patients.

Patients with head and neck cancer who undergo reconstructive surgery are at risk for deep venous thrombosis (DVT), but the risk profile for patients undergoing major flap reconstruction is highly variable. Herein, we report our findings from a retrospective analysis of head and neck cancer patients (n = 517) who underwent free (n = 384) or pedicled (n = 133) flap reconstructive operations at a major tertiary care center from 2011 to 2014. DVTs developed perioperatively in 9 (1.7%) patients. Compared with pedicled flap patients, free flap patients had a longer mean operative time (421.4 ± 4.4 vs 332.7 ± 10.7 min, P < .0001), but the DVT incidence did not differ significantly between free and pedicled flap patients (1.6% vs 2.2%, respectively, P = .28). These data suggest that perioperative DVT risk in head and neck oncology patients may be largely similar regardless of the reconstructive strategy pursued.

Update on Surgical Outcomes of Lateral Temporal Bone Resection for Ear and Temporal Bone Malignancies

Objectives Review outcomes of lateral temporal bone resections for ear and temporal bone malignancy. Design, Setting, and Participants Retrospective review of all lateral temporal bone resections performed from 2008 to 2015 at a single tertiary care center. Main Outcome Measures Patient demographics, perioperative variables, overall survival, disease‐free survival (DFS), and comparison of Kaplan‐Meier curves. Results Overall, 56 patients were identified with a mean follow‐up period of 2.3 ± 1.8 years. The predominant histopathologic diagnosis was squamous cell carcinoma (SCC, 54%), followed by salivary gland tumors (18%), and basal cell carcinoma (9%). Tumor stages were T1‐T2 in 23%, T3‐T4 in 73%, and two unknown primary lesions. Mean overall survival was 4.6 ± 0.4 years. Comparison of tumors with and without lymph node involvement or perineural invasion approached statistical significance for overall survival (p = 0.07 and 0.06, respectively). DFS was 2.5 ± 0.3 years. Stratification by lymph node status had a statistically significant difference in DFS (p = 0.03). Subgroup analysis of SCC patients did not reveal significant differences. Conclusions Based on our cohort, most patients with temporal bone malignancies present with advanced disease, making it difficult to achieve negative margins. Overall, lymph node status was the strongest predictor of survival in this group.

Chiari malformations: An important cause of pediatric aspiration

Chronic aspiration poses a major health risk to the pediatric population. We describe four cases in which work up for chronic aspiration with a brain MRI revealed a Chiari I malformation, a poorly described etiology of pediatric aspiration. All patients had at least one non-specific neurologic symptom but had swallow studies more characteristic of an anatomic than a neurologic etiology. Patients were referred to neurosurgery and underwent posterior fossa decompression with symptom improvement. A high index of suspicion for Chiari malformation should be maintained when the standard work up for aspiration is non-diagnostic, particularly when non-specific neurologic symptoms are present.