Laparoscopic surgery for adrenocortical carcinoma: Estimating the risk of margin-positive resection

BACKGROUND

Over recent years, there has been increasing adoption of minimally invasive surgery (MIS) in the treatment of adrenocortical carcinoma (ACC). However, MIS has been associated with noncurative resection and locoregional recurrence. We aimed to identify risk factors for margin-positivity among patients who undergo MIS resection for ACC. We hypothesized that a simple nomogram can accurately identify patients most suitable for curative MIS resection.

METHODS

Curative-intent resections for ACC were identified through the National Cancer Database spanning 2010-2018. Trends in MIS utilization were reported using Pearson correlation coefficients. Factors associated with margin-positive resection were identified among preoperatively available variables using multivariable logistic regression, then incorporated into a predictive model. Model quality was cross validated using an 80% training data set and 20% test data set.

RESULTS

Among 1260 ACC cases, 38.6% (486) underwent MIS resection. MIS utilization increased over time at nonacademic centers (R = 0.818, p = 0.007), but not at academic centers (R = 0.009, p = 0.982). Factors associated with margin-positive MIS resection were increasing age, nonacademic center (odds ratio [OR]: 1.8, p = 0.006), cT3 (OR: 4.7, p < 0.001) or cT4 tumors (OR: 14.6, p < 0.001), and right-sided tumors (OR: 2.0, p = 0.006). A predictive model incorporating these four factors produced favorable c-statistics of 0.75 in the training data set and 0.72 in the test data set. A pragmatic nomogram was created to enable bedside risk stratification.

CONCLUSIONS

An increasing proportion of ACC are resected via minimally invasive operations, particularly at nonacademic centers. Patient selection based on a few key factors can minimize the risk of noncurative surgery.

Circular RNA Cdr1as inhibits proliferation and delays injury-induced regeneration of the intestinal epithelium

Circular RNAs (circRNAs) are highly expressed in the mammalian intestinal epithelium, but their functions remain largely unknown. Here, we identified the circRNA Cdr1as as a repressor of intestinal epithelial regeneration and defense. Cdr1as levels increased in mouse intestinal mucosa after colitis and septic stress, as well as in human intestinal mucosa from patients with inflammatory bowel disease and sepsis. Ablation of the Cdr1as locus from the mouse genome enhanced renewal of the intestinal mucosa, promoted injury-induced epithelial regeneration, and protected the mucosa against colitis. We found approximately 40 microRNAs, including miR-195, differentially expressed between intestinal mucosa of Cdr1as-knockout (Cdr1as-/-) versus littermate mice. Increasing the levels of Cdr1as inhibited intestinal epithelial repair after wounding in cultured cells and repressed growth of intestinal organoids cultured ex vivo, but this inhibition was abolished by miR-195 silencing. The reduction in miR-195 levels in the Cdr1as-/- intestinal epithelium was the result of reduced stability and processing of the precursor miR-195. These findings indicate that Cdr1as reduces proliferation and repair of the intestinal epithelium at least in part via interaction with miR-195 and highlight a role for induced Cdr1as in the pathogenesis of unhealed wounds and disrupted renewal of the intestinal mucosa.

Age-stratified comparison of active surveillance versus radiofrequency ablation for papillary thyroid microcarcinoma using decision analysis

BACKGROUND

Papillary thyroid microcarcinomas may be treated with radiofrequency ablation, active surveillance, or surgery. The objective of this study was to use mathematical modeling to compare treatment alternatives for papillary thyroid microcarcinomas among those who decline surgery. We hypothesized that radiofrequency ablation would outperform active surveillance in avoiding progression and surgery but that the effect size would be small for older patients.

METHODS

We engaged stakeholders to identify meaningful long-term endpoints for papillary thyroid microcarcinoma treatment-(1) cancer progression/surgery, (2) need for thyroid replacement therapy, and (3) permanent treatment complication. A Markov decision analysis model was created to compare the probability of these endpoints after radiofrequency ablation or active surveillance for papillary thyroid microcarcinomas and overall cost. Transition probabilities were extracted from published literature. Model outcomes were estimated to have a 10-year time horizon.

RESULTS

The primary outcome yielded a number needed to treat of 18.1 for the avoidance of progression and 27.4 for the avoidance of lifelong thyroid replacement therapy for radiofrequency ablation compared to active surveillance. However, as patient age increased, the number needed to treat to avoid progression increased from 5.2 (age 20-29) to 39.1 (age 60+). The number needed to treat to avoid lifelong thyroid replacement therapy increased with age from 7.8 (age 20-29) to 59.3 (age 60+). The average 10-year cost/treatment for active surveillance and radiofrequency ablation were $6,400 and $11,700, respectively, translating to a cost per progression-avoided of $106,500.

CONCLUSION

As an alternative to active surveillance, radiofrequency ablation may have a greater therapeutic impact in younger patients. However, routine implementation may be cost-prohibitive for most patients with papillary thyroid microcarcinomas.

Growing Deficit in New Cancer Diagnoses 2 Years Into the COVID-19 Pandemic: A National Multicenter Study

BACKGROUND

Large decreases in cancer diagnoses were seen early in the COVID-19 pandemic. However, the evolution of these deficits since the end of 2020 and the advent of widespread vaccination is unknown.

METHODS

This study examined data from the Veterans Health Administration (VA) from 1 January 2018 through 28 February 2022 and identified patients with screening or diagnostic procedures or new cancer diagnoses for the four most common cancers in the VA health system: prostate, lung, colorectal, and bladder cancers. Monthly procedures and new diagnoses were calculated, and the pre-COVID era (January 2018 to February 2020) was compared with the COVID era (March 2020 to February 2022).

RESULTS

The study identified 2.5 million patients who underwent a diagnostic or screening procedure related to the four cancers. A new cancer was diagnosed for 317,833 patients. During the first 2 years of the pandemic, VA medical centers performed 13,022 fewer prostate biopsies, 32,348 fewer cystoscopies, and 200,710 fewer colonoscopies than in 2018-2019. These persistent deficits added a cumulative deficit of nearly 19,000 undiagnosed prostate cancers and 3300 to 3700 undiagnosed cancers each for lung, colon, and bladder. Decreased diagnostic and screening procedures correlated with decreased new diagnoses of cancer, particularly cancer of the prostate (R = 0.44) and bladder (R = 0.27).

CONCLUSION

Disruptions in new diagnoses of four common cancers (prostate, lung, bladder, and colorectal) seen early in the COVID-19 pandemic have persisted for 2 years. Although reductions improved from the early pandemic, new reductions during the Delta and Omicron waves demonstrate the continued impact of the COVID-19 pandemic on cancer care.

Control of Paneth cell function by HuR regulates gut mucosal growth by altering stem cell activity

Rapid self-renewal of the intestinal epithelium requires the activity of intestinal stem cells (ISCs) that are intermingled with Paneth cells (PCs) at the crypt base. PCs provide multiple secreted and surface-bound niche signals and play an important role in the regulation of ISC proliferation. Here, we show that control of PC function by RNA-binding protein HuR via mitochondria affects intestinal mucosal growth by altering ISC activity. Targeted deletion of HuR in mice disrupted PC gene expression profiles, reduced PC-derived niche factors, and impaired ISC function, leading to inhibited renewal of the intestinal epithelium. Human intestinal mucosa from patients with critical surgical disorders exhibited decreased levels of tissue HuR and PC/ISC niche dysfunction, along with disrupted mucosal growth. HuR deletion led to mitochondrial impairment by decreasing the levels of several mitochondrial-associated proteins including prohibitin 1 (PHB1) in the intestinal epithelium, whereas HuR enhanced PHB1 expression by preventing microRNA-195 binding to the Phb1 mRNA. These results indicate that HuR is essential for maintaining the integrity of the PC/ISC niche and highlight a novel role for a defective PC/ISC niche in the pathogenesis of intestinal mucosa atrophy.

Mid-term Surgery Outcomes in Patients With COVID-19: Results From a Nationwide Analysis

OBJECTIVE

Determine mid-term postoperative outcomes among coronavirus disease 2019 (COVID-19)-positive (+) patients compared with those who never tested positive before surgery.

BACKGROUND

COVID-19 is thought to be associated with prohibitively high rates of postoperative complications. However, prior studies have only evaluated 30-day outcomes, and most did not adjust for demographic, clinical, or procedural characteristics.

METHODS

We analyzed data from surgeries performed at all Veterans Affairs hospitals between March 2020 and 2021. Kaplan-Meier curves compared trends in mortality and Cox proportional hazards models estimated rates of mortality and pulmonary, thrombotic, and septic postoperative complications between patients with a positive preoperative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test [COVID (+)] and propensity score-matched COVID-negative (-) patients.

RESULTS

Of 153,741 surgical patients, 4778 COVID (+) were matched to 14,101 COVID (-). COVID (+) status was associated with higher postoperative mortality ( P <0.0001) with a 6-month survival of 94.2% (95% confidence interval: 93.2-95.2) versus 96.0% (95% confidence interval: 95.7.0-96.4) in COVID (-). The highest mortality was in the first 30 postoperative days. Hazards for mortality and postoperative complications in COVID (+) decreased with increasing time between testing COVID (+) and date of surgery. COVID (+) patients undergoing elective surgery had similar rates of mortality, thrombotic and septic complications, but higher rates of pulmonary complications than COVID (-) patients.

CONCLUSIONS

This is the first report of mid-term outcomes among COVID-19 patients undergoing surgery. COVID-19 is associated with decreased overall and complication-free survival primarily in the early postoperative period, delaying surgery by 5 weeks or more reduces risk of complications. Case urgency has a multiplicative effect on short-term and long-term risk of postoperative mortality and complications.

miR-542-5p targets c-myc and negates the cell proliferation effect of SphK1 in intestinal epithelial cells

Intestinal epithelial barrier defects occur commonly during a variety of pathological conditions, though their underlying mechanisms are not completely understood. Sphingosine-1-phosphate (S1P) has been shown to be a critical regulator of proliferation and of maintenance of an intact intestinal epithelial barrier, as is also sphingosine kinase 1 (SphK1), the rate-limiting enzyme for S1P synthesis. SphK1 has been shown to modulate its effect on intestinal epithelial proliferation through increased levels of c-myc. We conducted genome-wide profile analysis to search for differential microRNA expression related to overexpressed SphK1 demonstrating adjusted expression of microRNA 542-5p (miR-542-5p). Here, we show that miR-542-5p is regulated by SphK1 activity and is an effector of c-myc translation that ultimately serves as a critical regulator of the intestinal epithelial barrier. miR-542-5p directly regulates c-myc translation through direct binding to the c-myc mRNA. Exogenous S1P analogs administered in vivo protect murine intestinal barrier from damage due to mesenteric ischemia reperfusion, and damaged intestinal tissue had increased levels of miR-542-5p. These results indicate that miR-542-5p plays a critical role in the regulation of S1P-mediated intestinal barrier function, and may highlight a novel role in potential therapies.

Partial COVID-19 vaccination associated with reduction in postoperative mortality and SARS-CoV-2 infection

BACKGROUND

There are currently no data to guide decisions about delaying surgery to achieve full vaccination.

METHODS

We analyzed data from patients undergoing surgery at any of the 1,283 VA medical facilities nationwide and compared postoperative complication rates by vaccination status.

RESULTS

Of 87,073 surgical patients, 20% were fully vaccinated, 15% partially vaccinated, and 65% unvaccinated. Mortality was reduced in full vaccination vs. unvaccinated (Incidence Rate Ratio 0.77, 95% CI [0.62, 0.94]) and partially vaccinated vs. unvaccinated (0.75 [0.60, 0.94]). Postoperative COVID-19 infection was reduced in fully (0.18 [0.12, 0.26]) and partially vaccinated patients (0.34 [0.24, 0.48]). Fully vaccinated compared to partially vaccinated patients, had similar postoperative mortality (1.02, [0.78, 1.33]), but had decreased COVID-19 infection (0.53 [0.32, 0.87]), pneumonia (0.75 [0.62, 0.93]), and pulmonary failure (0.79 [0.68, 0.93]).

CONCLUSIONS

Full and partial vaccination reduces postoperative complications indicating the importance of any degree of vaccination prior to surgery.

miR-195 Regulates Intestinal Epithelial Restitution after Wounding by altering Actin-Related Protein-2 Translation

Early gut epithelial restitution reseals superficial wounds after acute injury, but the exact mechanism underlying this rapid mucosal repair remains largely unknown. MicroRNA-195 (miR-195) is highly expressed in the gut epithelium and involved in many aspects of mucosal pathobiology. Actin-related proteins (ARPs) are key components essential for stimulation of actin polymerization and regulate cell motility. Here we reported that miR-195 modulates early intestinal epithelial restitution by altering ARP-2 expression at the translation level. MiR-195 directly interacted with the ARP-2 mRNA, and ectopically overexpressed miR-195 decreased ARP-2 protein without effect on its mRNA content. In contrast, miR-195 silencing by transfection with the anti-miR-195 increased ARP-2 protein expression. Decreased ARP-2 levels by miR-195 were associated with an inhibition of early epithelial restitution, as indicated by a decrease in cell migration over the wounded area. Elevation of cellular ARP-2 levels by transfection with its transgene restored cell migration after wounding in cells overexpressing miR-195. Polyamines were found to decrease miR-195 abundance and enhanced ARP-2 translation, thus promoting epithelial restitution after wounding. Moreover, increasing the levels of miR-195 disrupted F-actin cytoskeleton organization, which was prevented by ARP2 overexpression. These results indicate that miR-195 inhibits early epithelial restitution by decreasing ARP-2 translation and that miR-195 expression is negatively regulated by cellular polyamines.

Impact of the COVID-19 pandemic on diagnosis of new cancers: A national multicenter study of the Veterans Affairs Healthcare System

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic caused disruptions in treatment for cancer. Less is known about its impact on new cancer diagnoses, where delays could cause worsening long-term outcomes. This study quantifies decreases in encounters related to prostate, lung, bladder and colorectal cancers, procedures that facilitate their diagnosis, and new diagnoses of those cancers in the COVID era compared to pre-COVID era.

METHODS

All encounters at Veterans' Affairs facilities nationwide from 2016 through 2020 were reviewed. The authors quantified trends in new diagnoses of cancer and in procedures facilitating their diagnosis, from January 1, 2018 onward. Using 2018 to 2019 as baseline, reductions in procedures and new cancer diagnoses in 2020 were estimated. Calculated absolute and percentage differences in annual volume and observed-to-expected volume ratios were calculated. Heat maps and funnel plots of volume changes were generated.

RESULTS

From 2018 through 2020, there were 4.1 million cancer-related encounters, 3.9 million relevant procedures, and 251,647 new cancers diagnosed. Compared to the annual averages in 2018 through 2019, colonoscopies in 2020 decreased by 45% whereas prostate biopsies, chest computed tomography scans, and cystoscopies decreased by 29%, 10%, and 21%, respectively. New cancer diagnoses decreased by 13% to 23%. These drops varied by state and continued to accumulate despite reductions in pandemic-related restrictions.

CONCLUSION

The authors identified substantial reductions in procedures used to diagnose cancer and subsequent reductions in new diagnoses of cancer across the United States because of the COVID-19 pandemic. A nomogram is provided to identify and resolve these unmet health care needs and avoid worse long-term cancer outcomes.

LAY SUMMARY

The disruptions due to the COVID-19 pandemic have led to substantial reductions in new cancers being diagnosed. This study quantifies those reductions in a national health care system and offers a method for understanding the backlog of cases and the resources needed to resolve them.

COVID-19 Vaccination Associated With Reduced Postoperative SARS-CoV-2 Infection and Morbidity

OBJECTIVE

The purpose of this study was to determine the effect of COVID-19 vaccination on postoperative mortality, pulmonary and thrombotic complications, readmissions and hospital lengths of stay among patients undergoing surgery in the United States.

BACKGROUND

While vaccination prevents COVID-19, little is known about its impact on postoperative complications.

METHODS

This is a nationwide observational cohort study of all 1,255 Veterans Affairs facilities nationwide. We compared patients undergoing surgery at least 2 weeks after their second dose of the Pfizer BioNTech or Moderna vaccines, to contemporary propensity score matched controls. Primary endpoints were 30-day mortality and postoperative COVID-19 infection. Secondary endpoints were pulmonary or thrombotic complications, readmissions, and hospital lengths of stay.

RESULTS

30,681 patients met inclusion criteria. After matching, there were 3,104 in the vaccination group (1,903 received the Pfizer BioNTech, and 1,201 received the Moderna vaccine) and 7,438 controls. Full COVID-19 vaccination was associated with lower rates of postoperative 30-day COVID-19 infection (Incidence Rate Ratio and 95% confidence intervals, 0.09 [0.01,0.44]), pulmonary complications (0.54 [0.39, 0.72]), thrombotic complications (0.68 [0.46, 0.99]) and decreased hospital lengths of stay (0.78 [0.69, 0.89]). Complications were also low in vaccinated patients who tested COVID-19 positive before surgery but events were too few to detect a significant difference compared to controls.

CONCLUSION

COVID-19 vaccination is associated with lower rates of postoperative morbidity. The benefit is most pronounced among individuals who have never had a COVID-19 infection before surgery.

A Nation-Wide Review of Elective Surgery and COVID-Surge Capacity

BACKGROUND

The COVID-19 pandemic has resulted in over 225,000 excess deaths in the United States. A moratorium on elective surgery was placed early in the pandemic to reduce risk to patients and staff and preserve critical care resources. This report evaluates the impact of the elective surgical moratorium on case volumes and intensive care unit (ICU) bed utilization.

METHODS

This retrospective review used a national convenience sample to correlate trends in the weekly rates of surgical cases at 170 Veterans Affairs Hospitals around the United States from January 1 to September 30, 2020 to national trends in the COVID-19 pandemic. We reviewed data on weekly number of procedures performed and ICU bed usage, stratified by level of urgency (elective, urgent, emergency), and whether an ICU bed was required within 24 hours of surgery. National data on the proportion of COVID-19 positive test results and mortality rates were obtained from the Center for Disease Control website.

RESULTS

198,911 unique surgical procedures performed during the study period. The total number of cases performed from January 1 to March 16 was 86,004 compared with 15,699 from March 17 to May 17. The reduction in volume occurred before an increase in the percentage of COVID-19 positive test results and deaths nationally. There was a 91% reduction from baseline in the number of elective surgeries performed allowing 78% of surgical ICU beds to be available for COVID-19 positive patients.

CONCLUSION

The moratorium on elective surgical cases was timely and effective in creating bed capacity for critically ill COVID-19 patients. Further analyses will allow targeted resource allocation for future pandemic planning.

Periprocedural complications in patients with SARS-CoV-2 infection compared to those without infection: A nationwide propensity-matched analysis

BACKGROUND

Reports on emergency surgery performed soon after a COVID-19 infection that are not controlled for premorbid risk-factors show increased 30-day mortality and pulmonary complications. This contributed to a virtual cessation of elective surgery during the pandemic surge. To inform evidence-based guidance on the decisions for surgery during the recovery phase of the pandemic, we compare 30-day outcomes in patients testing positive for COVID-19 before their operation, to contemporary propensity-matched COVID-19 negative patients undergoing the same procedures.

METHODS

This prospective multicentre study included all patients undergoing surgery at 170 Veterans Health Administration (VA) hospitals across the United States. COVID-19 positive patients were propensity matched to COVID-19 negative patients on demographic and procedural factors. We compared 30-day outcomes between COVID-19 positive and negative patients, and the effect of time from testing positive to the date of procedure (≤10 days, 11-30 days and >30 days) on outcomes.

RESULTS

Between March 1 and August 15, 2020, 449 COVID-19 positive and 51,238 negative patients met inclusion criteria. Propensity matching yielded 432 COVID-19 positive and 1256 negative patients among whom half underwent elective surgery. Infected patients had longer hospital stays (median seven days), higher rates of pneumonia (20.6%), ventilator requirement (7.6%), acute respiratory distress syndrome (ARDS, 17.1%), septic shock (13.7%), and ischemic stroke (5.8%), while mortality, reoperations and readmissions were not significantly different. Higher odds for ventilation and stroke persisted even when surgery was delayed 11-30 days, and for pneumonia, ARDS, and septic shock >30 days after a positive test.

DISCUSSION

30-day pulmonary, septic, and ischaemic complications are increased in COVID-19 positive, compared to propensity score matched negative patients. Odds for several complications persist despite a delay beyond ten days after testing positive. Individualized risk-stratification by pulmonary and atherosclerotic comorbidities should be considered when making decisions for delaying surgery in infected patients.

Increased complications in patients who test COVID-19 positive after elective surgery and implications for pre and postoperative screening

Background

The COVID-19 pandemic has necessitated the adoption of protocols to minimize risk of periprocedural complications associated with SARS-CoV-2 infection. This typically involves a preoperative symptom screen and nasal swab RT-PCR test for viral RNA. Asymptomatic patients with a negative COVID-19 test are cleared for surgery. However, little is known about the rate of postoperative COVID-19 positivity among elective surgical patients, risk factors for this group and rate of complications.

Methods

This prospective multicenter study included all patients undergoing elective surgery at 170 Veterans Health Administration (VA) hospitals across the United States. Patients were divided into groups based on first positive COVID-19 test within 30 days after surgery (COVID[-/+]), before surgery (COVID[+/−]) or negative throughout (COVID[−/−]). The cumulative incidence, risk factors for and complications of COVID[-/+], were estimated using univariate analysis, exact matching, and multivariable regression.

Results

Between March 1 and December 1, 2020 90,093 patients underwent elective surgery. Of these, 60,853 met inclusion criteria, of which 310 (0.5%) were in the COVID[-/+] group. Adjusted multivariable logistic regression identified female sex, end stage renal disease, chronic obstructive pulmonary disease, congestive heart failure, cancer, cirrhosis, and undergoing neurosurgical procedures as risk factors for being in the COVID[-/+] group. After matching on current procedural terminology code and month of procedure, multivariable Poisson regression estimated the complication rate ratio for the COVID[-/+] group vs. COVID[−/−] to be 8.4 (C.I. 4.9–14.4) for pulmonary complications, 3.0 (2.2, 4.1) for major complications, and 2.6 (1.9, 3.4) for any complication.

Discussion

Despite preoperative COVID-19 screening, there remains a risk of COVID infection within 30 days after elective surgery. This risk is increased for patients with a high comorbidity burden and those undergoing neurosurgical procedures. Higher intensity preoperative screening and closer postoperative monitoring is warranted in such patients because they have a significantly elevated risk of postoperative complications.

Long Noncoding RNA H19 Impairs the Intestinal Barrier by Suppressing Autophagy and Lowering Paneth and Goblet Cell Function

BACKGROUND & AIMS

The protective intestinal mucosal barrier consists of multiple elements including mucus and epithelial layers and immune defense; nonetheless, barrier dysfunction is common in various disorders. The imprinted and developmentally regulated long noncoding RNA H19 is involved in many cell processes and diseases. Here, we investigated the role of H19 in regulating Paneth and goblet cells and autophagy, and its impact on intestinal barrier dysfunction induced by septic stress.

METHODS

Studies were conducted in H19-deficient (H19^-/-) mice, mucosal tissues from patients with sepsis, primary enterocytes, and Caco-2 cells. Septic stress was induced by cecal ligation and puncture (CLP), and gut permeability was detected by tracer fluorescein isothiocyanate-dextran assays. The function of Paneth and goblet cells was examined by immunostaining for lysozyme and mucin 2, respectively, and autophagy was examined by microtubule-associated proteins 1A/1B light chain 3 II immunostaining and Western blot analysis. Intestinal organoids were isolated from H19^-/- and control littermate mice and treated with lipopolysaccharide (LPS).

RESULTS

Intestinal mucosal tissues in mice 24 hours after exposure to CLP and in patients with sepsis showed high H19 levels, associated with intestinal barrier dysfunction. Targeted deletion of the H19 gene in mice enhanced the function of Paneth and goblet cells and promoted autophagy in the small intestinal mucosa. Knockout of H19 protected Paneth and goblet cells against septic stress, preserved autophagy activation, and promoted gut barrier function after exposure to CLP. Compared with organoids from control littermate mice, intestinal organoids isolated from H19^-/- mice had increased numbers of lysozyme- and mucin 2-positive cells and showed increased tolerance to LPS. Conversely, ectopic overexpression of H19 in cultured intestinal epithelial cells prevented rapamycin-induced autophagy and abolished the rapamycin-induced protection of the epithelial barrier against LPS.

CONCLUSIONS

In investigations of mice, human tissues, primary organoids, and intestinal epithelial cells, we found that increased H19 inhibited the function of Paneth and goblet cells and suppressed autophagy, thus potentially contributing to barrier dysfunction in intestinal pathologies.

MiR-199a-3p decreases esophageal cancer cell proliferation by targeting p21 activated kinase 4

Although microRNA (miR) 199a-3p functions as a tumor suppressor in multiple malignancies, its expression and role in esophageal cancer have not been studied. Based on our previous observation that miR-199a-3p is markedly downregulated in esophageal cancer cell lines relative to esophageal epithelial cells, we examined the function of miR-199a-3p in these cells. MiR-199a-3p is predicted to bind with high affinity to the mRNA of p21 activated kinase 4 (PAK4). This kinase has been shown to be overexpressed in several malignancies and to modulate proliferation and motility. The current study is designed to determine whether miR-199a-3p regulates the expression of PAK4 in esophageal cancer cells and to understand the functional consequences of this interaction. Herein, we demonstrate reduced expression of miR-199a-3p in human esophageal cancer specimens and cell lines compared to esophageal epithelial cells, with associated increased expression of PAK4. Forced expression of miR-199a-3p decreases expression of PAK4 in esophageal cancer cell lines. Mechanistic studies reveal that miR-199a-3p binds to the 3'UTR of PAK4 mRNA. This interaction results in reduced levels of PAK4 mRNA due to decreased mRNA stability. Downregulation of PAK4 leads to decreased cyclin D1 (CD1) transcription and protein expression, resulting in markedly impaired cellular proliferation. When PAK4 expression is rescued, both CD1 transcription and protein return to baseline levels. Our results show that miR-199a-3p functions as a tumor suppressor in esophageal cancer cells through repression of PAK4. These findings suggest that both miR-199a-3p and PAK4 may be novel therapeutic targets in the treatment of esophageal cancer.

β-PIX plays an important role in regulation of intestinal epithelial restitution by interacting with GIT1 and Rac1 after wounding

Early gut mucosal restitution is a process by which intestinal epithelial cells (IECs) migrate over the wounded area, and its defective regulation occurs commonly in various critical pathological conditions. This rapid reepithelialization is mediated by different activating small GTP-binding proteins, but the exact mechanism underlying this process remains largely unknown. Recently, it has been reported that interaction between p21-activated kinase-interacting exchange factor (β-PIX) and G protein-coupled receptor kinase-interacting protein 1 (GIT1) activates small GTPases and plays an important role in the regulation of cell motility. Here, we show that induced association of β-PIX with GIT1 is essential for the stimulation of IEC migration after wounding by activating Rac1. Levels of β-PIX and GIT1 proteins and their association in differentiated IECs (line of IEC-Cdx2L1) were much higher than those observed in undifferentiated IECs (line of IEC-6), which was associated with an increase in IEC migration after wounding. Decreased levels of endogenous β-PIX by its gene-silencing destabilized β-PIX/GIT1 complexes, repressed Rac1 activity and inhibited cell migration over the wounded area. In contrast, ectopic overexpression of β-PIX increased the levels of β-PIX/GIT1 complexes, stimulated Rac1 activity, and enhanced intestinal epithelial restitution. Increased levels of cellular polyamines also stimulated β-PIX/GIT1 association, increased Rac1 activity, and promoted the epithelial restitution. Moreover, polyamine depletion decreased cellular abundances of β-PIX/GIT1 complex and repressed IEC migration after wounding, which was rescued by ectopic overexpression of β-PIX or GIT1. These results indicate that β-PIX/GIT1/Rac1 association is necessary for stimulation of IEC migration after wounding and that this signaling pathway is tightly regulated by cellular polyamines. NEW & NOTEWORTHY Our current study demonstrates that induced association of β-PIX with GIT1 is essential for the stimulation of intestinal epithelial restitution by activating Rac1, and this signaling pathway is tightly regulated by cellular polyamines.

Abstract B089: MicroRNA (miR) 214-3p targets ras-related protein14 (RAB14) to inhibit cell migration and invasion in esophageal cancer cells

Objectives: MiR-214-3p acts as a tumor suppressor in various malignancies. We have previously shown that miR-214-3p is markedly downregulated in esophageal cancer cell lines compared to esophageal epithelial cells and its downregulation contributes to chemoresistance in esophageal cancer cells. In several miR-target sequence analysis programs, miR-214-3p is predicted to bind RAB14 mRNA with high affinity. RAB14 is a member of the ras-associated binding protein family of low molecular mass GTPases that are involved in membrane trafficking. Its role in cancer is not well known. The objective of this study was to determine expression of RAB14 in esophageal cancer cells as well as to investigate the interaction between miR-214-3p and RAB14 in these cells and to characterize the functional implications of this interaction. Methods: Studies were performed in human esophageal epithelial (hESO) cells and in FLO1, SKGT4, and TE7 human esophageal cancer cells. Expression of miR-214-3p and RAB14 mRNA in these cell lines was measured by real-time PCR. RAB14 protein expression levels were examined by Western blot. Function of miR-214-3p was tested through its overexpression and silencing. Association of miR-214-3p with RAB14 mRNA was established using a biotinylated RNA pull-down assay and was confirmed by luciferase reporter assay. Cellular proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. xCELLigence RTCA system was used to access cell migration and invasion in real time. Results: Levels of miR-214-3p in FLO1, SKGT4, and TE7 esophageal cancer cells are markedly reduced compared to hESO cells. RAB14 mRNA and protein expression are correspondingly elevated in these cells compared to hESO cells. RAB14 mRNA and protein expression levels decreased in a time-dependent manner following miR-214-3p overexpression in FLO1, SKGT4, and TE7 cells. In reciprocal experiments, silencing miR-214-3p in hESO cells resulted in increased RAB14 mRNA and protein levels. Direct interaction of miR-214-3p and RAB14 mRNA was confirmed by biotinylated RNA-pull down assay and luciferase reporter construct. The stability of RAB14 mRNA is decreased following ectopic expression of miR-214-3p in FLO1 cells. Forced expression of miR-214-3p in FLO1 and SKGT4 cells led to a marked decrease in cellular proliferation, migration, and invasion. Conclusions: MiR-214-3p expression is significantly reduced in FLO1, SKGT4, and TE7 esophageal cancer cells relative to hESO cells. MiR-214-3p directly binds and destabilizes RAB14 mRNA. Forced expression of miR-214-3p results in significantly decreased RAB14 mRNA and protein expression, leading to decreased cellular proliferation, migration, and invasion in esophageal cancer cells. These results add to the roles by which miR-214-3p functions as a tumor suppressor in esophageal cancer cells.

Citation Format: Pornima Phatak, Jaladanki N. Rao, Carol B. Fowler, Douglas J. Turner, Jian-Ying Wang, James M. Donahue. MicroRNA (miR) 214-3p targets ras-related protein14 (RAB14) to inhibit cell migration and invasion in esophageal cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B089.

Posttranscriptional regulation of 14-3-3ζ by RNA-binding protein HuR modulating intestinal epithelial restitution after wounding

The 14‐3‐3ζ is a member of the family of 14‐3‐3 proteins and participates in many aspects of cellular processes, but its regulation and involvement in gut mucosal homeostasis remain unknown. Here, we report that 14‐3‐3ζ expression is tightly regulated at the posttranscription level by RNA‐binding protein HuR and plays an important role in early intestinal epithelial restitution after wounding. The 14‐3‐3ζ was highly expressed in the mucosa of gastrointestinal tract and in cultured intestinal epithelial cells (IECs). The 3′ untranslated region (UTR) of the 14‐3‐3ζ mRNA was bound to HuR, and this association enhanced 14‐3‐3ζ translation without effect on its mRNA content. Conditional target deletion of HuR in IECs decreased the level of 14‐3‐3ζ protein in the intestinal mucosa. Silencing 14‐3‐3ζ by transfection with specific siRNA targeting the 14‐3‐3ζ mRNA suppressed intestinal epithelial restitution as indicated by a decrease in IEC migration after wounding, whereas ectopic overexpression of the wild‐type 14‐3‐3ζ promoted cell migration. These results indicate that HuR induces 14‐3‐3ζ translation via interaction with its 3′ UTR and that 14‐3‐3ζ is necessary for stimulation of IEC migration after wounding.

Abstract A37: Overexpression of microRNA (miR) 199a-3p reduces proliferation through the induction of G2/M arrest in esophageal cancer cells by targeting cyclin D1

Objectives: Downregulation of miR-199a-3p has been demonstrated in several malignancies. A potential role of miR-199a-3p as a tumor suppressor has been postulated based on its ability to regulate targets involved in proliferation, apoptosis, and migration. Using miR array analysis, we have previously shown that miR-199a-3p is one of the most markedly downregulated miRs in esophageal cancer cell lines compared to esophageal epithelial cells. To date, no information exists on the role of miR-199a-3p in esophageal cancer cells. In several miR-target sequence analysis programs, miR-199a-3p is predicted to bind cyclin D1 mRNA with high affinity. The objective of this study was to determine expression of cyclin D1 in esophageal cancer cells and to investigate the interaction between miR-199a-3p and cyclin D1 in these cells and to characterize the functional implications of this interaction.

Methods: Studies were conducted in human esophageal epithelial (hESO) cells and in TE7 human squamous esophageal cancer cells. Levels of cyclin D1 protein expression were assessed by Western blot. Expression of miR-199a-3p and cyclin D1 mRNA in these cell lines was measured by real-time PCR. MiR-199a-3p function was tested through its overexpression and silencing. Binding of miR-199a-3p to cyclin D1 mRNA was examined using a biotinylated RNA pull-down assay. Cellular proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell cycle progression was determined by FACS analysis.

Results: Levels of miR-199a-3p in TE7 esophageal cancer cells are reduced by more than 3 log-fold, as compared to hESO cells. Cyclin D1 protein expression is markedly elevated in TE7 cells compared to hESO cells. Cyclin D1 mRNA and protein expression levels decreased in a time-dependent manner following miR-199a-3p overexpression in TE7 cells. In reciprocal experiments, silencing miR-199a-3p in hESO cells resulted in increased cyclin D1 mRNA and protein levels. Binding of miR-199a-3p to cyclin D1 mRNA was confirmed by biotinylated RNA-pull down assay. Forced expression of miR-199a-3p in TE7 cells led to a marked decrease in cellular proliferation resulting from the induction of G2/M arrest.

Conclusions: MiR-199a-3p expression is significantly reduced in TE7 esophageal cancer cells relative to hESO cells. MiR-199a-3p directly binds cyclin D1 mRNA, leading to its destabilization and a marked decreased in cyclin D1 protein expression. This interaction results in decreased cellular proliferation through the induction of G2/M arrest. These results suggest that the loss of miR-199a-3p in esophageal epithelial cells may be an important event in esophageal carcinogenesis.

Citation Format: Pornima Phatak, Kimberly Byrnes, Jaladanki N. Rao, Douglas J. Turner, Jian Y. Wang, James M. Donahue. Overexpression of microRNA (miR) 199a-3p reduces proliferation through the induction of G2/M arrest in esophageal cancer cells by targeting cyclin D1. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr A37.

Overexpression of miR-199a-5p decreases esophageal cancer cell proliferation through repression of mitogen-activated protein kinase kinase kinase-11 (MAP3K11)

Studies examining the oncogenic or tumor suppressive functions of dysregulated microRNAs (miRs) in cancer cells may also identify novel miR targets, which can themselves serve as therapeutic targets. Using array analysis, we have previously determined that miR-199a-5p was the most downregulated miR in two esophageal cancer cell lines compared to esophageal epithelial cells. MiR-199a-5p is predicted to bind mitogen-activated protein kinase kinase kinase 11 (MAP3K11) mRNA with high affinity. In this study, we observed that MAP3K11 is markedly overexpressed in esophageal cancer cell lines. Forced expression of miR-199a-5p in these cells leads to a decrease in the mRNA and protein levels of MAP3K11, due to decreased MAP3K11 mRNA stability. A direct binding interaction between miR-199a-5p and MAP3K11 mRNA is demonstrated using biotin pull-down assays and heterologous luciferase reporter constructs and confirmed by mutational analysis. Finally, forced expression of miR-199a-5p decreases proliferation of esophageal cancer cells by inducing G2/M arrest. This effect is mediated, in part, by decreased transcription of cyclin D1, due to reduced MAP3K11-mediated phosphorylation of c-Jun. These findings suggest that miR-199a-5p acts as a tumor suppressor in esophageal cancer cells and that its downregulation contributes to enhanced cellular proliferation by targeting MAP3K11.

Transgenic Expression of miR-222 Disrupts Intestinal Epithelial Regeneration by Targeting Multiple Genes Including Frizzled-7

Defects in intestinal epithelial integrity occur commonly in various pathologies. miR-222 is implicated in many aspects of cellular function and plays an important role in several diseases, but its exact biological function in the intestinal epithelium is underexplored. We generated mice with intestinal epithelial tissue-specific overexpression of miR-222 to investigate the function of miR-222 in intestinal physiology and diseases in vivo. Transgenic expression of miR-222 inhibited mucosal growth and increased susceptibility to apoptosis in the small intestine, thus leading to mucosal atrophy. The miR-222-elevated intestinal epithelium was vulnerable to pathological stress, since local overexpression of miR-222 not only delayed mucosal repair after ischemia/reperfusion-induced injury, but also exacerbated gut barrier dysfunction induced by exposure to cecal ligation and puncture. miR-222 overexpression also decreased expression of the Wnt receptor Frizzled-7 (FZD7), cyclin-dependent kinase 4 and tight junctions in the mucosal tissue. Mechanistically, we identified the Fzd7 messenger ribonucleic acid (mRNA) as a novel target of miR-222 and found that [miR-222/Fzd7 mRNA] association repressed Fzd7 mRNA translation. These results implicate miR-222 as a negative regulator of normal intestinal epithelial regeneration and protection by downregulating expression of multiple genes including the Fzd7. Our findings also suggest a novel role of increased miR-222 in the pathogenesis of mucosal growth inhibition, delayed healing and barrier dysfunction.

Caveolin-1 enhances rapid mucosal restitution by activating TRPC1-mediated Ca2+ signaling

Early rapid mucosal restitution occurs as a consequence of epithelial cell migration to reseal superficial wounds, a process independent of cell proliferation. Our previous studies revealed that the canonical transient receptor potential-1 (TRPC1) functions as a store-operated Ca(2+) channel (SOCs) in intestinal epithelial cells (IECs) and regulates epithelial restitution after wounding, but the exact mechanism underlying TRPC1 activation remains elusive. Caveolin-1 (Cav1) is a major component protein that is associated with caveolar lipid rafts in the plasma membrane and was recently identified as a regulator of store-operated Ca(2+) entry (SOCE). Here, we showed that Cav1 plays an important role in the regulation of mucosal restitution by activating TRPC1-mediated Ca(2+) signaling. Target deletion of Cav1 delayed gastric mucosal repair after exposure to hypertonic NaCl in mice, although it did not affect total levels of TRPC1 protein. In cultured IECs, Cav1 directly interacted with TRPC1 and formed Cav1/TRPC1 complex as measured by immunoprecipitation assays. Cav1 silencing in stable TRPC1-transfected cells by transfection with siCav1 reduced SOCE without effect on the level of resting [Ca(2+)]cyt. Inhibition of Cav1 expression by siCav1 and subsequent decrease in Ca(2+) influx repressed epithelial restitution, as indicated by a decrease in cell migration over the wounded area, whereas stable ectopic overexpression of Cav1 increased Cav1/TRPC1 complex, induced SOCE, and enhanced cell migration after wounding. These results indicate that Cav1 physically interacts with and activates TRPC1, thus stimulating TRPC1-mediated Ca(2+) signaling and rapid mucosal restitution after injury.

Jnk2 deletion disrupts intestinal mucosal homeostasis and maturation by differentially modulating RNA-binding proteins HuR and CUGBP1

Homeostasis and maturation of the mammalian intestinal epithelium are preserved through strict regulation of cell proliferation, apoptosis, and differentiation, but the exact mechanism underlying this process remains largely unknown. c-Jun NH2-terminal kinase 2 (JNK2) is highly expressed in the intestinal mucosa, and its activation plays an important role in proliferation and also mediates apoptosis in cultured intestinal epithelial cells (IECs). Here, we investigated the in vivo function of JNK2 in the regulation of intestinal epithelial homeostasis and maturation by using a targeted gene deletion approach. Targeted deletion of the jnk2 gene increased cell proliferation within the crypts in the small intestine and disrupted mucosal maturation as indicated by decreases in the height of villi and the villus-to-crypt ratio. JNK2 deletion also decreased susceptibility of the intestinal epithelium to apoptosis. JNK2-deficient intestinal epithelium was associated with an increase in the level of the RNA-binding protein HuR and with a decrease in the abundance of CUG-binding protein 1 (CUGBP1). In studies in vitro, JNK2 silencing protected intestinal epithelial cell-6 (IEC-6) cells against apoptosis and this protection was prevented by inhibiting HuR. Ectopic overexpression of CUGBP1 repressed IEC-6 cell proliferation, whereas CUGBP1 silencing enhanced cell growth. These results indicate that JNK2 is essential for maintenance of normal intestinal epithelial homeostasis and maturation under biological conditions by differentially modulating HuR and CUGBP1.

Src-mediated caveolin-1 phosphorylation regulates intestinal epithelial restitution by altering Ca(2+) influx after wounding

Early mucosal restitution occurs as a consequence of intestinal epithelial cell (IEC) migration to reseal superficial wounds, but its exact mechanism remains largely unknown. Caveolin-1 (Cav1), a major component associated with caveolar lipid rafts in the plasma membrane, is implicated in many aspects of cellular functions. This study determined if c-Src kinase (Src)-induced Cav1 phosphorylation promotes intestinal epithelial restitution after wounding by activating Cav1-mediated Ca(2+) signaling. Src directly interacted with Cav1, formed Cav1-Src complexes, and phosphorylated Cav1 in IECs. Inhibition of Src activity by its chemical inhibitor PP2 or suppression of the functional caveolin scaffolding domain by caveolin-scaffolding domain peptides prevented Cav1-Src interaction, reduced Cav1 phosphorylation, decreased Ca(2+) influx, and inhibited cell migration after wounding. Disruption of caveolar lipid raft microdomains by methyl-β-cyclodextrin reduced Cav1-mediated Ca(2+) influx and repressed epithelial restitution. Moreover, Src silencing prevented subcellular redistribution of phosphorylated Cav1 in migrating IECs. These results indicate that Src-induced Cav1 phosphorylation stimulates epithelial restitution by increasing Cav1-mediated Ca(2+) signaling after wounding, thus contributing to the maintenance of gut mucosal integrity under various pathological conditions.

Inhibition of Smurf2 translation by miR-322/503 modulates TGF-β/Smad2 signaling and intestinal epithelial homeostasis

Smurf2 is an E3 ubiquitin ligase that regulates TGF-β/Smad signaling and is implicated in a wide variety of cellular responses. miR-322 and miR-503 repress Smurf2 translation and thus modulate TGF-β/Smad2 signaling and intestinal epithelial homeostasis.

Smad ubiquitin regulatory factor 2 (Smurf2) is an E3 ubiquitin ligase that regulates transforming growth factor β (TGF-β)/Smad signaling and is implicated in a wide variety of cellular responses, but the exact mechanisms that control Smurf2 abundance are largely unknown. Here we identify microRNA-322 (miR-322) and miR-503 as novel factors that regulate Smurf2 expression posttranscriptionally. Both miR-322 and miR-503 interact with Smurf2 mRNA via its 3′-untranslated region (UTR) and repress Smurf2 translation but do not affect total Smurf2 mRNA levels. Studies using heterologous reporter constructs reveal a greater repressive effect of miR-322/503 through a single binding site in the Smurf2 3′-UTR, whereas point mutation of this site prevents miR-322/503–induced repression of Smurf2 translation. Increased levels of endogenous Smurf2 via antagonism of miR-322/503 inhibits TGF-β–induced Smad2 activation by increasing degradation of phosphorylated Smad2. Furthermore, the increase in Smurf2 in intestinal epithelial cells (IECs) expressing lower levels of miR-322/503 is associated with increased resistance to apoptosis, which is abolished by Smurf2 silencing. These findings indicate that miR-322/503 represses Smurf2 translation, in turn affecting intestinal epithelial homeostasis by altering TGF-β/Smad2 signaling and IEC apoptosis.

Custom Mentholation of Commercial Cigarettes for Research Purposes

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We developed a simple and repeatable technique to create research cigarettes that differ only in menthol content.

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We qualified a method by which the menthol and nicotine content of a cigarette can be quantified.

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We investigated the rate of loss of menthol from our custom-mentholated cigarettes over time during storage.

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We are currently using these custom-mentholated cigarettes in human exposure studies.

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Our custom-mentholated cigarettes will help to elucidate the effects of menthol on the toxicity of tobacco smoke.

In the U.S. menthol remains the sole permitted characterizing cigarette flavor additive in part because efforts to link menthol cigarette use to increased tobacco-related disease risk have been inconclusive. To perform definitive studies, cigarettes that differ only in menthol content are required, yet these are not commercially available. We prepared research cigarettes differing only in menthol content by deposition of l-menthol vapor directly onto commercial nonmenthol cigarettes, and developed a method to measure a cigarette's menthol and nicotine content. With our custom-mentholation technique we achieved the desired moderately high menthol content (as compared to commercial brands) of 6.7 ± 1.0 mg/g (n = 25) without perturbing the cigarettes’ nicotine content (17.7 ± 0.7 mg/g [n = 25]). We also characterized other pertinent attributes of our custom-mentholated cigarettes, including percent transmission of menthol and nicotine to mainstream smoke and the rate of loss of menthol over time during storage at room temperature. We are currently using this simple mentholation technique to investigate the differences in human exposure to selected chemicals in cigarette smoke due only to the presence of the added menthol. Our cigarettes will also aid in the elucidation of the effects of menthol on the toxicity of tobacco smoke.

CANDIDATE GENES FOR LIMITING CHOLESTATIC INTESTINAL INJURY IDENTIFIED BY GENE EXPRESSION PROFILING

The lack of bile flow from the liver into the intestine can have devastating complications including hepatic failure, sepsis and even death. This pathologic condition known as cholestasis can result from etiologies as diverse as total parenteral nutrition (TPN), hepatitis and pancreatic cancer. The intestinal injury associated with cholestasis has been shown to result in decreased intestinal resistance, increased bacterial translocation and increased endotoxemia. Anecdotal clinical evidence suggests a genetic predisposition to exaggerated injury. Recent animal research on two different strains of inbred mice demonstrating different rates of bacterial translocation with different mortality rates supports this premise. In this study, a microarray analysis of intestinal tissue following common bile duct ligation (CBDL) performed under general anesthesia on these same two strains of inbred mice was done with the goal of identifying the potential molecular mechanistic pathways responsible. Over 500 genes were increased more than 2.0 fold following CBDL. The most promising candidate genes included MUPs, Serpina1a and LCN-2. RT-PCR validated the microarray results for these candidate genes. In an in vitro experiment using differentiated intestinal epithelial cells, inhibition of MUP-1 by siRNA resulted in increased intestinal epithelial cell permeability. Diverse novel mechanisms involving the growth hormone pathway, the acute phase response and the innate immune response are thus potential avenues for limiting cholestatic intestinal injury. Changes in gene expression were at times found to be not only due to the CBDL but also due to the murine strain. Should further studies in cholestatic patients demonstrate inter-individual variability similar to what we have shown in mice, then a "personalized medicine" approach to cholestatic patients may become possible.

Air concentrations of PBDEs on in-flight airplanes and assessment of flight crew inhalation exposure

To address the knowledge gaps regarding inhalation exposure of flight crew to polybrominated diphenyl ethers (PBDEs) on airplanes, we measured PBDE concentrations in air samples collected in the cabin air at cruising altitudes and used Bayesian Decision Analysis (BDA) to evaluate the likelihood of inhalation exposure to result in the average daily dose (ADD) of a member of the flight crew to exceed EPA Reference Doses (RfDs), accounting for all other aircraft and non-aircraft exposures. A total of 59 air samples were collected from different aircraft and analyzed for four PBDE congeners-BDE 47, 99, 100 and 209 (a subset were also analyzed for BDE 183). For congeners with a published RfD, high estimates of ADD were calculated for all non-aircraft exposure pathways and non-inhalation exposure onboard aircraft; inhalation exposure limits were then derived based on the difference between the RfD and ADDs for all other exposure pathways. The 95th percentile measured concentrations of PBDEs in aircraft air were <1% of the derived inhalation exposure limits. Likelihood probabilities of 95th percentile exposure concentrations >1% of the defined exposure limit were zero for all congeners with published RfDs.

Pneumatosis and portal venous gas: do CT findings reassure?

BACKGROUND

Small, single-institution studies have suggested risk factors for bowel ischemia/necrosis (I/N) in patients with computed tomography (CT) findings of pneumatosis (PN) and portal venous gas (PVG). Here, analysis has been expanded in a large, multicenter study.

MATERIALS & METHODS

Logistic regression models and receiver operating characteristic curves were used to construct a scoring system for I/N in cases of PN/PVG.

RESULTS

Of 265 patients with PN/PVG identified, 209 had adequate data. In unadjusted analyses the following variables were significantly associated with I/N: age, peritoneal signs, ascites, the presence of both PVG and PN, blood urea nitrogen (BUN), CO2, albumin, and a history of hypertension, myocardial infarction, or stroke. In contrast, the CT findings of mesenteric stranding, bowel-wall thickening, and type of PN were not associated with I/N. In adjusted analyses, three variables were significantly associated with I/N: age ≥60 y (odds ratio = 2.51, 95% confidence interval: 1.26-4.97), peritoneal signs (10.58, 4.23-26.4), and BUN >25 mg/dL (3.08, 1.54-6.17), whereas presence of both PN and PVG (versus only one) was associated with an increase (but not statistically significant increase) in odds (2.01, 0.94-4.36). Although several ad hoc models were used to maximize diagnostic ability, with maximal odds ratio = 174, the areas of receiver operating characteristic curves were all below 0.80, revealing suboptimal accuracy to diagnose I/N.

CONCLUSIONS

Older age, peritoneal signs, and high BUN are associated with I/N, suggesting an ability to predict which patients need operation. CT findings traditionally suggestive of ischemic PN/PVG, however, do not diagnose I/N accurately enough to reliably identify patients needing operation.

Sphingosine kinase 1 overexpression stimulates intestinal epithelial cell proliferation through increased c-Myc translation

Sphingosine-1-phosphate (S1P), through mechanisms that are not completely understood, is shown to modulate cellular proliferation, which is critically important for maintaining the integrity of intestinal epithelium. Here, we show that increased S1P promotes proliferation in intestinal epithelial cells. We found that overexpression of sphingosine kinase 1 (SphK1), the rate-limiting enzyme for S1P synthesis, significantly increased cell proliferation and that this occurred through enhanced expression of c-Myc. Further, we found that the increased pattern of expression of c-Myc occurred predominantly due to its increased translation. The overexpressed SphK1 led to increased checkpoint kinase 2 and enhanced HuR phosphorylation which allowed for increased translation of c-Myc mRNA through HuR binding at the 3'-untranslated regions. Our findings demonstrate that S1P modulates intestinal cell proliferation and provides new insights as to the mechanistic actions of SphK1 and S1P in maintaining intestinal epithelial homeostasis.

Polyamines regulate intestinal epithelial restitution through TRPC1-mediated Ca²+ signaling by differentially modulating STIM1 and STIM2

Early epithelial restitution occurs as a consequence of intestinal epithelial cell (IEC) migration after wounding, and its defective regulation is implicated in various critical pathological conditions. Polyamines stimulate intestinal epithelial restitution, but their exact mechanism remains unclear. Canonical transient receptor potential-1 (TRPC1)-mediated Ca(2+) signaling is crucial for stimulation of IEC migration after wounding, and induced translocation of stromal interaction molecule 1 (STIM1) to the plasma membrane activates TRPC1-mediated Ca(2+) influx and thus enhanced restitution. Here, we show that polyamines regulate intestinal epithelial restitution through TRPC1-mediated Ca(2+) signaling by altering the ratio of STIM1 to STIM2. Increasing cellular polyamines by ectopic overexpression of the ornithine decarboxylase (ODC) gene stimulated STIM1 but inhibited STIM2 expression, whereas depletion of cellular polyamines by inhibiting ODC activity decreased STIM1 but increased STIM2 levels. Induced STIM1/TRPC1 association by increasing polyamines enhanced Ca(2+) influx and stimulated epithelial restitution, while decreased formation of the STIM1/TRPC1 complex by polyamine depletion decreased Ca(2+) influx and repressed cell migration. Induced STIM1/STIM2 heteromers by polyamine depletion or STIM2 overexpression suppressed STIM1 membrane translocation and inhibited Ca(2+) influx and epithelial restitution. These results indicate that polyamines differentially modulate cellular STIM1 and STIM2 levels in IECs, in turn controlling TRPC1-mediated Ca(2+) signaling and influencing cell migration after wounding.

Induced expression of STIM1 sensitizes intestinal epithelial cells to apoptosis by modulating store-operated Ca2+ influx

INTRODUCTION

Apoptosis plays a critical role in the maintenance of gut mucosal epithelial homeostasis and is tightly regulated by numerous factors including intracellular Ca(2+). Canonical transient receptor potential channel-1 (TRPC1) is expressed in intestinal epithelial cells (IECs) and functions as a store-operated Ca(2+) channel. We have recently demonstrated that increased TRPC1 activity sensitizes IECs to apoptosis, but the upstream signaling initiating TRPC1 activation remains elusive. The novel protein, stromal interaction molecule 1 (STIM1), is shown to act as a store Ca(2+) sensor, and it can rapidly translocate to the plasma membrane where it directly interacts with TRPC1. The current study determined whether STIM1 plays an important role in the regulation of IEC apoptosis by activating TRPC1 channel activity.

METHODS

Studies were conducted in IEC-6 cells (derived from rat intestinal crypts) and stable TRPC1-transfected IECs (IEC-TRPC1). Apoptosis was induced by tumor necrosis factor-α (TNF-α)/cycloheximide (CHX), and intracellular free Ca(2+) concentration ([Ca(2+)](cyt)) was measured by fluorescence digital imaging analysis. Functions of STIM1 were investigated by specific siRNA (siSTIM1) and ectopic overexpression of the constitutively active STIM1 EF-hand mutants.

RESULTS

Stable STIM1-transfected IEC-6 cells (IEC-STIM1) showed increased STIM1 protein expression (~5 fold) and displayed a sustained increase in Ca(2+) influx after Ca(2+) store depletion (~2 fold). Susceptibility of IEC-STIM1 cells to TNF-α/CHX-induced apoptosis increased significantly as measured by changes in morphological features, DNA fragmentation, and caspase-3 activity. Apoptotic cells were increased from ~20% in parental IEC-6 cells to ~40% in stable IEC-STIM1 cells 4 h after exposure to TNF-α/CHX (p<0.05). In addition, stable IEC-TRPC1 cells also exhibited an increased sensitivity to TNF-α/CHX-induced apoptosis, which was prevented by STIM1 silencing through siSTIM1 transfection. STIM1 silencing by siSTIM1 also decreased Ca(2+) influx after store depletion in cells overexpressing TRPC1. Levels of Ca(2+) influx due to store depletion were decreased by ~70% in STIM1-silenced populations. Similarly, exposure of IEC-STIM1 cells to Ca(2+)-free medium also blocked increased sensitivity to apoptosis.

CONCLUSIONS

These results indicate that (1) STIM1 plays an important role in the regulation of IEC apoptosis by altering TRPC1 activity and (2) ectopic STIM1 expression sensitizes IECs to apoptosis through induction in TRPC1-mediated Ca(2+) influx.

Bile salts increase epithelial cell proliferation through HuR-induced c-Myc expression

BACKGROUND

Bile salts increase intestinal mucosal proliferation through an increase in c-Myc, a transcription factor that controls the expression of numerous translation regulatory proteins. HuR is an RNA-binding protein that regulates translation of target mRNAs. RNA-binding proteins can control mRNA stability by binding to AU- and U-rich elements located in the 3'-untranslated regions (3'-UTRs) of target mRNAs.

AIM

To determine how bile salt-induced c-Myc stimulates enterocyte proliferation.

METHODS

Enterocyte proliferation was measured both in vivo using C57Bl6 mice and in vitro using IEC-6 cells after taurodeoxycholate (TDCA) supplementation. HuR and c-Myc protein expression was determined by immunoblot. c-Myc mRNA expression was determined by PCR. HuR expression was inhibited using specific small interfering RNA. HuR binding to c-Myc mRNA was determined by immunoprecipitation.

RESULTS

TDCA increased enterocyte proliferation in vivo and in vitro. TDCA stimulates translocation of HuR from the nucleus to the cytoplasm. Cytoplasmic HuR regulates c-Myc translation by HuR binding to the 3'-UTR of c-Myc mRNA. Increased TDCA-induced c-Myc increases enterocyte proliferation.

CONCLUSIONS

Bile salts have beneficial effects on the intestinal epithelial mucosa, which are important in maintaining intestinal mucosal integrity and function. These data further support an important beneficial role of bile salts in regulation of mucosal growth and repair. Decreased enterocyte exposure to luminal bile salts, as occurs during critical illness, liver failure, starvation, and intestinal injury, may have a detrimental effect on mucosal integrity.

miR-503 represses CUG-binding protein 1 translation by recruiting CUGBP1 mRNA to processing bodies

This study shows that microRNA-503 interacts with the CUG-binding protein 1 (CUGBP1) mRNA and represses its translation by recruiting the CUGBP1 mRNA to processing bodies.

microRNAs (miRNAs) and RNA-binding proteins (RBPs) jointly regulate gene expression at the posttranscriptional level and are involved in many aspects of cellular functions. The RBP CUG-binding protein 1 (CUGBP1) destabilizes and represses the translation of several target mRNAs, but the exact mechanism that regulates CUGBP1 abundance remains elusive. In this paper, we show that miR-503, computationally predicted to associate with three sites of the CUGBP1 mRNA, represses CUGBP1 expression. Overexpression of an miR-503 precursor (pre-miR-503) reduced the de novo synthesis of CUGBP1 protein, whereas inhibiting miR-503 by using an antisense RNA (antagomir) enhanced CUGBP1 biosynthesis and elevated its abundance; neither intervention changed total CUGBP1 mRNA levels. Studies using heterologous reporter constructs revealed a greater repressive effect of miR-503 through the CUGBP1 coding region sites than through the single CUGBP1 3′-untranslated region target site. CUGBP1 mRNA levels in processing bodies (P-bodies) increased in cells transfected with pre-miR-503, while silencing P-body resident proteins Ago2, RCK, or LSm4 decreased miR-503–mediated repression of CUGBP1 expression. Decreasing the levels of cellular polyamines reduced endogenous miR-503 levels and promoted CUGBP1 expression, an effect that was prevented by ectopic miR-503 overexpression. Repression of CUGBP1 by miR-503 in turn altered the expression of CUGBP1 target mRNAs and thus increased the sensitivity of intestinal epithelial cells to apoptosis. These findings identify miR-503 as both a novel regulator of CUGBP1 expression and a modulator of intestinal epithelial homoeostasis.

Activation of Wnt3a signaling stimulates intestinal epithelial repair by promoting c-Myc-regulated gene expression

In response to mucosal injury, epithelial cells modify the patterns of expressed genes to repair damaged tissue rapidly. Our previous studies have demonstrated that the transcription factor c-Myc is necessary for stimulation of epithelial cell renewal during mucosal healing, but the up-stream signaling initiating c-Myc gene expression after injury remains unknown. Wnts are cysteine-rich glycoproteins that act as short-range ligands to locally activate receptor-mediated signaling pathways and correlate with the increased expression of the c-Myc gene. The current study tested the hypothesis that Wnt3a signaling is implicated in intestinal epithelial repair after wounding by stimulating c-Myc expression. Elevated Wnt3a signaling in intestinal epithelial cells (IEC-6 line) by coculturing with stable Wnt3a-transfected fibroblasts or ectopic overexpression of the Wnt3a gene enhanced intestinal epithelial repair after wounding. This stimulatory effect on epithelial repair was prevented by silencing the Wnt coreceptor LRP6 or by c-Myc silencing. Activation of the Wnt3a signaling pathway increased β-catenin nuclear translocation by decreasing its phosphorylation and stimulated c-Myc expression during epithelial repair after wounding. In stable Wnt3a-transfected IEC-6 cells, increased levels of c-Myc were associated with an increase in expression of c-Myc-regulated genes cyclcin D1 and cyclin E, whereas c-Myc silencing inhibited expression of cyclin D1 and cyclin E and delayed epithelial repair. These results indicate that elevated Wnt3a signaling in intestinal epithelial cells after wounding stimulates epithelial repair by promoting c-Myc-regulated gene expression.

Regulation of cyclin-dependent kinase 4 translation through CUG-binding protein 1 and microRNA-222 by polyamines

The amino acid-derived polyamines are organic cations that are essential for growth in all mammalian cells, but their exact roles at the molecular level remain largely unknown. Here we provide evidence that polyamines promote the translation of cyclin-dependent kinase 4 (CDK4) by the action of CUG-binding protein 1 (CUGBP1) and microRNA-222 (miR-222) in intestinal epithelial cells. Both CUGBP1 and miR-222 were found to bind the CDK4 mRNA coding region and 3'-untranslated region and repressed CDK4 translation synergistically. Depletion of cellular polyamines increased cytoplasmic CUGBP1 abundance and miR-222 levels, induced their associations with the CDK4 mRNA, and inhibited CDK4 translation, whereas increasing the levels of cellular polyamines decreased CDK4 mRNA interaction with CUGBP1 and miR-222, in turn inducing CDK4 expression. Polyamine-deficient cells exhibited an increased colocalization of tagged CDK4 mRNA with processing bodies; this colocalization was abolished by silencing CUGBP1 and miR-222. Together, our findings indicate that polyamine-regulated CUGBP1 and miR-222 modulate CDK4 translation at least in part by altering the recruitment of CDK4 mRNA to processing bodies.

Sphingosine-1-phosphate regulates the expression of adherens junction protein E-cadherin and enhances intestinal epithelial cell barrier function

BACKGROUND

The regulation of intestinal barrier permeability is important in the maintenance of normal intestinal physiology. Sphingosine-1-phosphate (S1P) has been shown to play a pivotal role in enhancing barrier function in several non-intestinal tissues. The current study determined whether S1P regulated function of the intestinal epithelial barrier by altering expression of E-cadherin, an important protein in adherens junctions.

METHODS

Studies were performed upon cultured differentiated IECs (IEC-Cdx2L1 line) using standard techniques.

RESULTS

S1P treatment significantly increased levels of E-cadherin protein and mRNA in intestinal epithelial cells (IECs) and also led to E-cadherin localizing strongly to the cell-cell border. S1P also improved the barrier function as indicated by a decrease in 14C-mannitol paracellular permeability and an increase in transepithelial electrical resistance (TEER) in vitro.

CONCLUSIONS

These results indicate that S1P increases levels of E-cadherin, both in cellular amounts and at the cell-cell junctions, and leads to improved barrier integrity in cultured intestinal epithelial cells.

Polyamines regulate c-Myc translation through Chk2-dependent HuR phosphorylation

All mammalian cells depend on polyamines for normal growth and proliferation, but the exact roles of polyamines at the molecular level remain largely unknown. The RNA-binding protein HuR modulates the stability and translation of many target mRNAs. Here, we show that in rat intestinal epithelial cells (IECs), polyamines enhanced HuR association with the 3'-untranslated region of the c-Myc mRNA by increasing HuR phosphorylation by Chk2, in turn promoting c-Myc translation. Depletion of cellular polyamines inhibited Chk2 and reduced the affinity of HuR for c-Myc mRNA; these effects were completely reversed by addition of the polyamine putrescine or by Chk2 overexpression. In cells with high content of cellular polyamines, HuR silencing or Chk2 silencing reduced c-Myc translation and c-Myc expression levels. Our findings demonstrate that polyamines regulate c-Myc translation in IECs through HuR phosphorylation by Chk2 and provide new insight into the molecular functions of cellular polyamines.

Polyamines regulate E-cadherin transcription through c-Myc modulating intestinal epithelial barrier function

The integrity of the intestinal epithelial barrier depends on intercellular junctions that are highly regulated by numerous extracellular and intracellular factors. E-cadherin is found primarily at the adherens junctions in the intestinal mucosa and mediates strong cell-cell contacts that have a functional role in forming and regulating the epithelial barrier. Polyamines are necessary for E-cadherin expression, but the exact mechanism underlying polyamines remains elusive. The current study was performed to determine whether polyamines induce E-cadherin expression through the transcription factor c-Myc and whether polyamine-regulated E-cadherin plays a role in maintenance of the epithelial barrier integrity. Decreasing cellular polyamines reduced c-Myc and repressed E-cadherin transcription as indicated by a decrease in levels of E-cadherin promoter activity and its mRNA. Forced expression of the c-myc gene by infection with adenoviral vector containing c-Myc cDNA stimulated E-cadherin promoter activity and increased E-cadherin mRNA and protein levels in polyamine-deficient cells. Experiments using different E-cadherin promoter mutants revealed that induction of E-cadherin transcription by c-Myc was mediated through the E-Pal box located at the proximal region of the E-cadherin promoter. Decreased levels of E-cadherin in polyamine-deficient cells marginally increased basal levels of paracellular permeability but, remarkably, potentiated H(2)O(2)-induced epithelial barrier dysfunction. E-cadherin silencing by transfection with its specific small interfering RNA also increased vulnerability of the epithelial barrier to H(2)O(2). These results indicate that polyamines enhance E-cadherin transcription by activating c-Myc, thus promoting function of the epithelial barrier.

Acute Influenza A infection induces bronchial hyper-responsiveness in mice

This study aimed to determine whether the route of administration of methacholine (MCh) influenced the pattern of airway hyper-responsiveness (AHR) in mice. BALB/c mice were inoculated with a 50-microL volume containing 10(4.5)-pfu Influenza virus A/Mem/1/71(H3N1) or media. MCh responsiveness in vivo [inhaled (0.01-30 mg/mL), i.v. MCh (6-48 microg/min/kg)] and in vitro were measured at day 4 post-infection (D4) during acute lower respiratory infection (LRI) and following resolution of infection at day 20 (D20) using a low-frequency, forced oscillation technique. Inflammation was assessed in bronchoalveolar lavage fluid. Infected mice had pulmonary inflammation and heightened responsiveness to both inhaled (p<0.03) and intravenous (p<0.02) MCh on D4, but not on D20. In vitro responsiveness was not altered at either time point. Influenza A LRI results in AHR during acute infection associated with a marked inflammatory response and increased permeability of the alveolar-capillary barrier. These data suggest that intrinsic muscle properties are not altered but MCh has greater access to airway smooth muscle during acute infection.

Induced TRPC1 expression increases protein phosphatase 2A sensitizing intestinal epithelial cells to apoptosis through inhibition of NF-kappaB activation

Transient receptor potential canonical-1 (TRPC1) functions as a store-operated Ca2+ channel in intestinal epithelial cells (IECs), and induced TRPC1 expression sensitizes IECs to apoptosis by inhibiting NF-kappaB activation. However, the exact mechanism by which increased TRPC1 results in NF-kappaB inactivation remains elusive. Protein phosphatase 2A (PP2A) is a widely conserved protein serine/threonine phosphatase that is implicated in the regulation of a wide array of cellular functions including apoptosis. The present study tests the hypothesis that induced TRPC1 expression inhibits NF-kappaB activation by increasing PP2A activity through Ca2+ influx in IECs. The expression of TRPC1 induced by stable transfection with the wild-type TRPC1 gene increased PP2A activity as indicated by increases in levels of PP2A proteins and their phosphatase activity. Increased levels of PP2A activity in stable TRPC1-transfected IEC-6 cells (IEC-TRPC1) were associated with decreased nuclear levels of NF-kappaB proteins and a reduction in NF-kappaB-dependent transcriptional activity, although there were no changes in total NF-kappaB protein levels. Inhibition of PP2A activity by treatment with okadaic acid or PP2A silencing with small interfering RNA not only enhanced NF-kappaB transactivation but also prevented the increased susceptibility of IEC-TRPC1 cells to apoptosis induced by treatment with tumor necrosis factor-alpha (TNF-alpha)/cycloheximide (CHX). Decreasing Ca2+ influx by exposure to the Ca2+-free medium reduced PP2A mRNA levels, destabilized PP2A proteins, and induced NF-kappaB activation, thus blocking the increased sensitivity of IEC-TRPC1 cells to TNF-alpha/CHX-induced apoptosis. These results indicate that induced TRPC1 expression increases PP2A activity through Ca2+ influx and that increased PP2A sensitizes IECs to apoptosis as a result of NF-kappaB inactivation.