Upadacitinib Achieves Clinical and Endoscopic Outcomes in Crohn's Disease Regardless of Prior Biologic Exposure

BACKGROUND & AIMS

Upadacitinib, an oral Janus kinase inhibitor, achieved significantly higher rates of clinical remission and endoscopic response vs placebo during induction (U-EXCEL [NCT03345849], U-EXCEED [NCT03345836]) and maintenance (U-ENDURE [NCT03345823]) treatment in patients with moderate-to-severe Crohn's disease. Prior biologic failure is often associated with reduced responses to subsequent therapies. This post hoc analysis assessed upadacitinib efficacy by prior biologic failure status.

METHODS

Patients were randomized to placebo or upadacitinib 45 mg (UPA45) for 12 weeks (induction). UPA45 clinical responders were enrolled in U-ENDURE and rerandomized to placebo, upadacitinib 15 mg, or upadacitinib 30 mg (UPA30) for 52 weeks. Assessments were by prior biologic failure.

RESULTS

Of 1021 patients, 733 (71.8%) had prior biologic failure. Across outcomes and subgroups, upadacitinib-treated patients achieved higher rates vs placebo. During induction, upadacitinib had higher rates vs placebo for clinical remission based on stool frequency/abdominal pain score (without failure: 54.0% vs 28.3%; with failure: 42.2% vs 14.1%) and endoscopic response (without failure: 52.0% vs 16.2%; with failure: 35.7% vs 5.3%). In maintenance, the greatest treatment effect (upadacitinib vs placebo) was among patients with prior biologic failure treated with UPA30 (clinical remission without failure: 58.5% vs 32.7%; with failure: 42.5% vs 8.7%; endoscopic response without failure: 43.9% vs 17.9%; with failure: 38.9% vs 4.0%). Patients without vs with prior biologic failure had fewer adverse events.

CONCLUSIONS

Upadacitinib led to higher absolutes rates of clinical and endoscopic outcomes in patients without vs with prior biologic failure. Patients treated with upadacitinib achieved greater rates of clinical and endoscopic improvements vs placebo, regardless of prior biologic exposure.

CLINICALTRIALS

gov: NCT03345849, NCT03345836, NCT03345823.

An Unusual Hiccup: Severe Singultus as a Symptom in Ulcerative Colitis

Inflammatory bowel disease encompasses a group of chronic inflammatory conditions associated with both intestinal and extraintestinal manifestations. We present a 26-year-old man with a history of ulcerative colitis who presented with a disease exacerbation associated with severe intractable hiccups. We report a unique clinical symptom associated with severe ulcerative colitis and the diagnostic dilemma associated with this presentation. This case highlights the importance of recognizing unusual symptoms that can be associated with inflammatory bowel disease exacerbations and demonstrates the therapeutic potential of effective therapy of the underlying inflammatory disease.

Freeing Time and Reducing Costs: The Value of a Specialized Nursing Service in IBD

This invited editorial provides commentary on the manuscript by Yu et al regarding outcomes of a dedicated IBD nursing service. We highlight financial, time, and care quality benefits identified by the authors and contextualize the results for journal readership.

Mycobacterium avium subspecies paratuberculosis (MAP) and Crohn's disease: the debate continues

Crohn's disease (CD) in humans and Johne's disease (JD) in ruminants share numerous clinical and pathologic similarities. As Mycobacteria avium subspecies paratuberculosis (MAP) is known to fulfill Koch's postulates as the cause of JD, there has been considerable debate over the past century about whether MAP also plays a role in CD. With recent advances in MAP identification techniques, we can now demonstrate a higher presence of MAP in CD patients compared to the general population. However, it remains unclear if MAP is playing a bystander role or is directly pathogenic in these patients. Studies have shown that there may be an immune response targeting MAP in these patients, which may underlie a pathologic role in CD. Clinical studies have yielded conflicting results as to whether anti-MAP therapy improves clinical outcomes in CD, leading to the lack of its inclusion within evidence-based clinical guidelines. Additionally, many of these studies have been small case series, with only a few randomized controlled trials published to date. In this article, we will discuss the historical context of MAP in CD, review clinical and laboratory data surrounding detection of MAP and possible pathogenesis in human disease, and suggest future directions which may finally provide some clarity to this debate.

Predicting inpatient mortality in patients with inflammatory bowel disease: A machine learning approach

BACKGROUND AND AIM

Data are lacking on predicting inpatient mortality (IM) in patients admitted for inflammatory bowel disease (IBD). IM is a critical outcome; however, difficulty in its prediction exists due to infrequent occurrence. We assessed IM predictors and developed a predictive model for IM using machine-learning (ML).

METHODS

Using the National Inpatient Sample (NIS) database (2005-2017), we extracted adults admitted for IBD. After ML-guided predictor selection, we trained and internally validated multiple algorithms, targeting minimum sensitivity and positive likelihood ratio (+LR) ≥ 80% and ≥ 3, respectively. Diagnostic odds ratio (DOR) compared algorithm performance. The best performing algorithm was additionally trained and validated for an IBD-related surgery sub-cohort. External validation was done using NIS 2018.

RESULTS

In 398 426 adult IBD admissions, IM was 0.32% overall, and 0.87% among the surgical cohort (n = 40 784). Increasing age, ulcerative colitis, IBD-related surgery, pneumonia, chronic lung disease, acute kidney injury, malnutrition, frailty, heart failure, blood transfusion, sepsis/septic shock and thromboembolism were associated with increased IM. The QLattice algorithm, provided the highest performance model (+LR: 3.2, 95% CI 3.0-3.3; area-under-curve [AUC]:0.87, 85% sensitivity, 73% specificity), distinguishing IM patients by 15.6-fold when comparing high to low-risk patients. The surgical cohort model (+LR: 8.5, AUC: 0.94, 85% sensitivity, 90% specificity), distinguished IM patients by 49-fold. Both models performed excellently in external validation. An online calculator (https://clinicalc.ai/im-ibd/) was developed allowing bedside model predictions.

CONCLUSIONS

An online prediction-model calculator captured > 80% IM cases during IBD-related admissions, with high discriminatory effectiveness. This allows for risk stratification and provides a basis for assessing interventions to reduce mortality in high-risk patients.

Article Topic: Positioning Ulcerative Colitis Therapies in 2022 and Beyond

PURPOSE OF REVIEW

Ulcerative colitis (UC) is a chronic disease with an increasing incidence. Recent guidelines emphasize treating toward objective targets, requiring the use of effective, steroid-sparing therapies. This review summarizes the safety and efficacy data of available therapies as well comparative effectiveness studies in order to help the reader make rational treatment decisions.

RECENT FINDINGS

Following the approval of tumor necrosis factor alpha antagonists, we have seen recent regulatory approval of several additional biologic and small molecule agents from several therapeutic classes (integrin antagonists, interleukin 12/23 antagonists, Janus kinase inhibitors, and sphingosine-1-phosphate receptor antagonists) for UC. Randomized, controlled trials, real-world analyses, and network meta-analyses have investigated the comparative safety and efficacy of these therapies in order to help clinicians better position these therapies in clinical practice. Numerous agents are now approved for the treatment of UC. This evidence-based review will help the reader understand the important factors weighing into treatment decisions for patients with UC and enable patient education and discussion with a focus on a shared decision-making approach.

COVID-19 is not associated with worse long-term inflammatory bowel disease outcomes: a multicenter case-control study

BACKGROUND

Inflammatory bowel disease (IBD) is not associated with worse coronavirus disease 2019 (COVID-19) outcomes. However, data are lacking regarding the long-term impact of severe acute respiratory syndrome coronavirus 2 infection on the disease course of IBD.

OBJECTIVES

We aimed to investigate the effect of COVID-19 on long-term outcomes of IBD.

DESIGN

We performed a multicenter case-control study of patients with IBD and COVID-19 between February 2020 and December 2020.

METHODS

Cases and controls were individuals with IBD with presence or absence, respectively, of COVID-19-related symptoms and confirmatory testing. The primary composite outcome was IBD-related hospitalization or surgery.

RESULTS

We identified 251 cases [ulcerative colitis (n = 111, 45%), Crohn's disease (n = 139, 55%)] and 251 controls, with a median follow-up of 394 days. The primary composite outcome of IBD-related hospitalization or surgery occurred in 29 (12%) cases versus 38 (15%) controls (p = 0.24) and on multivariate Cox regression, COVID-19 was not associated with increased risk of adverse IBD outcomes [adjusted hazard ratio (aHR): 0.84, 95% confidence interval [CI]: 0.44-1.42]. When stratified by infection severity, severe COVID-19 was associated with a numerically increased risk of adverse IBD outcomes (aHR: 2.43, 95% CI: 1.00-5.86), whereas mild-to-moderate COVID-19 was not (aHR: 0.68, 95% CI: 0.38-1.23).

CONCLUSION

In this case-control study, COVID-19 did not have a long-term impact on the disease course of IBD. However, severe COVID-19 was numerically associated with worse IBD outcomes, underscoring the continued importance of risk mitigation and prevention strategies for patients with IBD during the ongoing COVID-19 pandemic.

Impact of Inflammatory Bowel Disease Therapies on Durability of Humoral Response to SARS-CoV-2 Vaccination

Immunization against the spike protein of SARS-CoV-2 reduces transmission1,2 and severe outcomes. However, little is known regarding the impact of immune-mediated diseases and immunosuppressive medications on the efficacy of vaccination. Vaccination immunity is transient, with breakthrough cases increasing at longer time intervals since the last dose.3,4 Although there are data on SARS-CoV-2 vaccine on early seroconversion in patients with inflammatory bowel disease (IBD),5 no data in the same cohort exist describing the durability of these antibodies over time. We sought to investigate the impact of IBD and its therapies on postvaccination antibody response and kinetics of immunogenicity decline, because these findings may better inform clinical guidelines and recommendations on precautions and booster vaccination.

Dual Biologic or Small Molecule Therapy for Treatment of Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

We conducted a systematic review and meta-analysis to summarize emerging data on the safety and effectiveness of dual biologic therapy in combination or with tofacitinib in patients with refractory inflammatory bowel disease (IBD).

METHODS

Through a systematic search of multiple electronic databases through November 9, 2020, we identified cohort studies or case series (>10 patients) reporting the safety and effectiveness of simultaneous use of biologic agents in combination or with tofacitinib in patients with IBD. Rates of adverse events, clinical remission, and endoscopic remission were synthesized using pooled data, and we identified factors associated with successful dual therapy.

RESULTS

We identified 30 studies reporting 288 trials of dual biologic or small molecule therapy in 279 patients (76% Crohn's disease; median duration of treatment 24 weeks (IQR₂₅-IQR₇₅ 1332)). The main indications for dual therapy included medically refractory IBD (81%) and concurrent extra-intestinal manifestations or rheumatologic disease (12%). The most common combinations of dual therapy included tumor necrosis factor-α antagonists & anti-integrins (48%), ustekinumab & anti-integrins (19%); 61% of patients had previously failed at least one of the two therapies used in combination. Over a median follow-up of 32 weeks (IQR₂₅-IQR₇₅ 24-52), pooled rates of adverse and serious adverse events were 31% (95% CI, 13%-54%) and 6.5% (95% CI, 2.1%-13.1%); pooled rates of clinical and endoscopic remission were 59% (95% CI, 42%-74%), and 34% (95% CI, 23%-46%), respectively. 12% (95% CI, 4%-24%) of patients required surgery. Rates of success were higher in patients on dual therapy due to EIM. Heterogeneity was not significant for endoscopic response (P = .88, I² = 0%), endoscopic remission (P = .44, I² = 0%), and malignancy (P = .87, I² = 0%). However, significant heterogeneity existed for other outcomes.

CONCLUSIONS

Dual biologic or small molecule therapy may be a possible option in highly selected, refractory IBD patients at specialized centers. Higher quality combination of therapies with a significant improvement in the quality of data is required prior to more widespread use.

Bacterial Swarmers Enriched During Intestinal Stress Ameliorate Damage

BACKGROUND AND AIMS

Bacterial swarming, a collective movement on a surface, has rarely been associated with human pathophysiology. This study aims to define a role for bacterial swarmers in amelioration of intestinal stress.

METHODS

We developed a polymicrobial plate agar assay to detect swarming and screened mice and humans with intestinal stress and inflammation. From chemically induced colitis in mice, as well as humans with inflammatory bowel disease, we developed techniques to isolate the dominant swarmers. We developed swarm-deficient but growth and swim-competent mutant bacteria as isogenic controls. We performed bacterial reinoculation studies in mice with colitis, fecal 16S, and meta-transcriptomic analyses, as well as in vitro microbial interaction studies.

RESULTS

We show that bacterial swarmers are highly predictive of intestinal stress in mice and humans. We isolated a novel Enterobacter swarming strain, SM3, from mouse feces. SM3 and other known commensal swarmers, in contrast to their mutant strains, abrogated intestinal inflammation in mice. Treatment of colitic mice with SM3, but not its mutants, enriched beneficial fecal anaerobes belonging to the family of Bacteroidales S24-7. We observed SM3 swarming associated pathways in the in vivo fecal meta-transcriptomes. In vitro growth of S24-7 was enriched in presence of SM3 or its mutants; however, because SM3, but not mutants, induced S24-7 in vivo, we concluded that swarming plays an essential role in disseminating SM3 in vivo.

CONCLUSIONS

Overall, our work identified a new but counterintuitive paradigm in which intestinal stress allows for the emergence of swarming bacteria; however, these bacteria act to heal intestinal inflammation.

Deciphering structural bases of intestinal and hepatic selectivity in targeting pregnane X receptor with indole-based microbial mimics

Microbial metabolite mimicry is a new concept that promises to deliver compounds that have minimal liabilities and enhanced therapeutic effects in a host. In a previous publication, we have shown that microbial metabolites of L-tryptophan, indoles, when chemically altered, yielded potent anti-inflammatory pregnane X Receptor (PXR)-targeting lead compounds, FKK5 and FKK6, targeting intestinal inflammation. Our aim in this study was to further define structure-activity relationships between indole analogs and PXR, we removed the phenyl-sulfonyl group or replaced the pyridyl residue with imidazolopyridyl of FKK6. Our results showed that while removal of the phenyl-sulfonyl group from FKK6 (now called CVK003) shifts agonist activity away from PXR towards the aryl hydrocarbon receptor (AhR), the imidazolopyridyl addition preserves PXR activity in vitro. However, when these compounds are administered to mice, that unlike the parent molecule, FKK6, they exhibit poor induction of PXR target genes in the intestines and the liver. These data suggest that modifications of FKK6 specifically in the pyridyl moiety can result in compounds with weak PXR activity in vivo. These observations are a significant step forward for understanding the structure-activity relationships (SAR) between indole mimics and receptors, PXR and AhR.

Patient-Preferences Favoring Treatment Discontinuation Are Reduced With Vedolizumab and Ustekinumab Compared With TNF Antagonists in Inflammatory Bowel Disease

Background

Nonadherence to biologic therapy in inflammatory bowel disease (IBD) is associated with risk of relapse, immunogenicity, and disease complications. Significant nonadherence prevalence is reported with tumor necrosis factor (TNF) antagonists but the risk of nonadherence with newer biologics with better safety profiles is unknown. This study aimed to investigate if IBD patient-preferences favoring biologic discontinuation vary by biologic class and analyze factors associated with such preferences.

Methods

A convenience sample of 200 adults with IBD on biologic therapy treated at an academic outpatient center was surveyed using a 22-point questionnaire. Patient-preference favoring treatment discontinuation between TNF-antagonist and non-TNF-antagonist biologics [vedolizumab (VDZ)/ustekinumab (UST)] was compared using χ ² test. Risk factors associated with a preference to discontinue biologic therapy were evaluated using univariable and multivariable logistic regression, and Spearman rank correlation analyses.

Results

A total of 190 questionnaires were analyzed that contained data on preferences regarding biologic discontinuation (median age 36 years, 62% were females; 63% had Crohn disease; 56% were receiving a TNF antagonist, 31% VDZ, and 14% UST). Overall, 32% patients reported a preference to discontinue biologic treatment with a higher proportion among those receiving a TNF antagonist compared with VDZ/UST (39.6% vs 21.4%; P < 0.01). Current VDZ/UST use was independently associated with a reduced odds of patient-preference favoring biologic discontinuation [adjusted odds ratio: 2.67 (1.42-5.01); P < 0.01]. The most concerning factor to patients was the perceived risk of side effects. Patients on VDZ/UST perceived their therapy to be safer than those receiving a TNF antagonist (r = 0.2, P = 0.04).

Conclusions

Patient-preference favoring treatment discontinuation is improved with VDZ/UST compared with TNF-antagonist biologic therapy.

Vaccination in the Elderly and IBD

PURPOSE OF REVIEW

Significant gaps in knowledge and utilization of vaccinations exist among practitioners providing care for patients with IBD. This review is intended to update the reader on best practices for vaccination within the IBD population with a specific focus on the elderly.

RECENT FINDINGS

Advances in IBD therapeutics have recently increased the number of immunosuppressive therapies available to practitioners. Differences in mechanisms of action of these medications have led to differential implications pertaining to vaccination strategies. Additionally, new vaccines, including the recombinant zoster vaccine, have recently become available for the use in the IBD population. Given the prominent role the IBD provider plays in the management of patients with IBD, a clear understanding of best practices is essential. This review provides a framework for the integration of optimal vaccination strategies for practitioners caring for adult and elderly patients with IBD.

Escalation of Immunosuppressive Therapy for Inflammatory Bowel Disease Is Not Associated With Adverse Outcomes After Infection With Clostridium difficile

BACKGROUND

Clostridium difficile infection (CDI) is common in patients with inflammatory bowel disease (IBD), often leading to diagnostic confusion and delays in IBD therapy escalation. This study sought to assess outcomes after CDI in IBD patients exposed to new or escalated immunosuppressive therapy.

METHODS

This multicenter retrospective cohort study included IBD patients with documented CDI at 4 academic medical centers. Data were abstracted from clinical databases at each institution. Outcomes at 30 and 90 days were compared between patients undergoing new or intensified immunosuppressive therapy and those without therapy escalation. Continuous variables were compared using t tests, and proportions using chi-square tests. Multivariable logistic regression was used to determine the association of individual variables with severe outcomes (including death, sepsis, and/or colectomy) within 90 days. Secondary outcomes included CDI recurrence, rehospitalization, worsening of IBD, and severe outcomes within 30 days.

RESULTS

A total of 207 adult patients with IBD and CDI were included, of whom 62 underwent escalation to biologic or corticosteroid therapy (median time to escalation, 13 days). Severe outcomes within 90 days occurred in 21 (15.6%) nonescalated and 1 (1.8%) therapy-escalated patients. Serum albumin <2.5 mg/dL, lactate >2.2 mg/dL, intensive care unit admission, hypotension, and comorbid disease were associated with severe outcomes. Likelihood of severe outcomes was decreased in patients undergoing escalation of IBD therapy after CDI (adjusted odds ratio [aOR], 0.12) and increased among patients aged >65 years (aOR, 4.55).

CONCLUSIONS

Therapy escalation for IBD within 90 days of CDI was not associated with worse clinical outcomes. Initiation of immunosuppression for active IBD may therefore be appropriate in carefully selected patients after treatment of CDI.

Helicobacter pylori is associated with increased risk of serrated colonic polyps: Analysis of serrated polyp risk factors

BACKGROUND

Sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA) are recognized precursors of colorectal cancer, but their risk factors are not well established. We investigated the association between Helicobacter pylori infection (HPI) and the development of SSA and TSA.

METHODS

Retrospective data were collected on patients aged ≥ 18 years that underwent colonoscopy with biopsy between 2006 and 2016. Based on histology, patients were classified into three groups: those with SSA and/or TSA, (serrated neoplasia group, SN); conventional adenomas only (CA); and with no polyps (NP). Gastric HPI status, demographic, and clinical risk factors were compared between groups using bivariate and multivariable analysis.

RESULTS

HPI was significantly associated with increased risk of SN (SN vs. NP: OR 1.71 [95% CI 1.29-2.27]; SN vs. CA: 1.49 [1.14-1.96]). Additional factors associated with increased risk of SN included the following: age 50-75 years, compared to younger age (SN vs. NP: 2.83 [1.69-4.74]), female gender (SN vs. CA: 1.28 [0.99-1.64]), White race, compared to Blacks (SN vs. CA: 1.52 [1.07-2.15)], overweight and obese body mass index [SN vs. NP: p < 0.001) and current smoking status (SN vs. CA: 2.09 [1.55-2.82)]. Among SN, higher HPI prevalence was associated with dysplasia (p = 0.05) and proximal location (p = 0.01).

CONCLUSIONS

Our data suggest that gastric HPI is associated with increased risk of SN and CA, with a stronger association with SN as compared to CA. Age 50-75 years, female gender, White race, obesity, and smoking were also predictors of SN. A positive correlation of HPI with proximal and dysplastic SN suggests a possible role in serrated pathway carcinogenesis. Prospective studies with large patient population are needed to further investigate this association.

Abstract 4092: Long-lived Dclk1+ cells serve as colon cancer initiating cells

Introduction: In the rapidly proliferating gastrointestinal epithelium, long-lived tissue stem cells, characterized by multipotentiality and self-renewing ability, remain the most likely cellular origin for cancer. Previous studies have suggested actively cycling Lgr5+ stem cells are one cellular origin for intestinal adenomas. However, it has also recently been suggested that non-Lgr5+ cells may also contribute to the cellular origin of colorectal cancer. Doublecortin-like kinase 1 (Dclk1) protein is a gastrointestinal tuft cell marker that has been proposed to identify quiescent stem cells and cancer stem cells that sustain tumor growth. The role of Dclk1+ tuft cells within the gastrointestinal epithelium and their potential to function as cancer-initiating cells, however, remain poorly understood. Here, we used Dclk1(BAC)-CreERT;ROSA26rLacZ mice crossed to APCff mice to examine whether Dclk1+ cells contribute to colonic tumor formation.

Methods: To recapitulate the endogenous expression pattern of Dclk1, we used a BAC strategy and generated a transgenic mouse with a Tamoxifen inducible Cre under the control of the Dclk1 promoter (Dclk1-BAC-Cre-ERT). Dclk1-CreERT mice were crossed to both ROSA26rLacZ and APCff mice and treated with tamoxifen (6 mg p.o.). Dclk1+ lineage tracing was assessed by X-gal staining. To examine the contribution of the Dclk1+ cells to colonic tumorigenesis, we treated Dclk1(BAC)-CreERT;ROSA26rLacZ; APCff mice with DSS (3% in drinking water) to induce colitis. Mice were sacrificed 3-4 months after DSS weeks to assess for tumor formation and X-gal staining performed to stain for the Dclk1+ cell lineage.

Results: Dclk1-BAC-CreERT genetic lineage tracing demonstrated that a subpopulation of Dclk1+ cells is extremely long-lived and shows rare stem cell abilities. Moreover, genetic ablation reveals a pivotal role for Dclk1+ tuft cells in the response to intestinal and colonic injury. Surprisingly, conditional loss of APC in Dclk1+ cells is not sufficient to drive colonic carcinogenesis, whereas induction of DSS colitis in Dclk1-CreERT; APCflox/flox mice leads to the development of poorly differentiated colonic adenocarcinoma. Importantly, colonic tumor formation occurs even when the onset of colitis is delayed for up to 3 months after APC loss in Dclk1+ cells.

Conclusions. Thus, our data define a novel intestinal Dclk1+ tuft cell population that is long-lived, quiescent and important for intestinal homeostasis and regeneration. Long-lived Dclk1+ cells maintain quiescence even following oncogenic mutation, but are activated by tissue injury and can serve as a potent cellular origin of colon cancer.

Citation Format: Samuel Asfaha, Christoph Benedikt Westphalen, Yoku Hayakawa, Yoshihiro Takemoto, Dana J. Lukin, Wanda Setlik, Helen Remotti, Ashlesha Muley, Xiaowei Chen, Randal May, Courtney W. Houchen, James G. Fox, Michael D. Gershon, Michael Quante, Timothy Wang. Long-lived Dclk1+ cells serve as colon cancer initiating cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4092. doi:10.1158/1538-7445.AM2014-4092

p53 Promotes cell survival due to the reversibility of its cell-cycle checkpoints

The tumor suppressor p53 (TP53) has a well-studied role in triggering cell-cycle checkpoint in response to DNA damage. Previous studies have suggested that functional p53 enhances chemosensitivity. In contrast, data are presented to show that p53 can be required for cell survival following DNA damage due to activation of reversible cell-cycle checkpoints. The cellular outcome to DNA damage is determined by the duration and extent of the stimulus in a p53-dependent manner. In response to transient or low levels of DNA damage, p53 triggers a reversible G2 arrest, whereas a sustained p53-dependent cell-cycle arrest and senescence follows prolonged or high levels of DNA damage. Regardless of the length of treatment, p53-null cells arrest in G2, but ultimately adapt and proceed into mitosis. Interestingly, they fail to undergo cytokinesis, become multinucleated, and then die from apoptosis. Upon transient treatment with DNA-damaging agents, wild-type p53 cells reversibly arrest and repair the damage, whereas p53-null cells fail to do so and die. These data indicate that p53 can promote cell survival by inducing reversible cell-cycle arrest, thereby allowing for DNA repair. Thus, transient treatments may exploit differences between wild-type p53 and p53-null cells.

IMPLICATIONS

Although p53 status has been suggested as a clinical predictor of chemotherapeutic efficacy, studies to date have not always supported this. This study demonstrates that p53 is still an important determinant of cell fate in response to chemotherapy, under the appropriate treatment conditions.

Long-lived intestinal tuft cells serve as colon cancer-initiating cells

Doublecortin-like kinase 1 protein (DCLK1) is a gastrointestinal tuft cell marker that has been proposed to identify quiescent and tumor growth-sustaining stem cells. DCLK1⁺ tuft cells are increased in inflammation-induced carcinogenesis; however, the role of these cells within the gastrointestinal epithelium and their potential as cancer-initiating cells are poorly understood. Here, using a BAC-CreERT-dependent genetic lineage-tracing strategy, we determined that a subpopulation of DCLK1⁺ cells is extremely long lived and possesses rare stem cell abilities. Moreover, genetic ablation of Dclk1 revealed that DCLK1⁺ tuft cells contribute to recovery following intestinal and colonic injury. Surprisingly, conditional knockdown of the Wnt regulator APC in DCLK1⁺ cells was not sufficient to drive colonic carcinogenesis under normal conditions; however, dextran sodium sulfate-induced (DSS-induced) colitis promoted the development of poorly differentiated colonic adenocarcinoma in mice lacking APC in DCLK1⁺ cells. Importantly, colonic tumor formation occurred even when colitis onset was delayed for up to 3 months after induced APC loss in DCLK1⁺ cells. Thus, our data define an intestinal DCLK1⁺ tuft cell population that is long lived, quiescent, and important for intestinal homeostasis and regeneration. Long-lived DCLK1⁺ cells maintain quiescence even following oncogenic mutation, but are activated by tissue injury and can serve to initiate colon cancer.

Effect of comorbid conditions on adherence to colorectal cancer screening

Potential barriers to colorectal cancer (CRC) screening include preexisting medical conditions (comorbidities), physician recommendation, psychosocial factors, and screening preparedness. This study's purpose was to investigate the impact of comorbid conditions on CRC screening among African Americans. A stage-matched randomized clinical trial was performed. Asymptomatic African Americans over age 50, with a primary care physician, and eligible for CRC screening were recruited at The Mount Sinai Hospital from 2005 to 2008. One hundred sixty-one patients were assessed for referral for, and completion of, CRC screening, comorbid conditions, "readiness to change," and number of physician visits within the observation period. Data was compared to a pretrial index to predict the likely effect of comorbid conditions on CRC screening. One hundred fifty-nine patients completed the study; 108 (68.9%) were referred for and 34 (21.2%) completed CRC screening. No demographic characteristics were associated with CRC screening completion. CRC screening referrals were similar for all patients, regardless of comorbidities or clinical visits. Comorbidities rated as having extreme influence on CRC screening showed a trend toward lower screening rates. There was a significant increase in screening rates among participants in advanced stages of readiness at enrollment. These data suggest that while comorbidities did not predict colonoscopy completion, they may play a role in concert with other factors. This is the only study to assess the effect of screening colonoscopy in an African American primary care setting. We must continue to explore interventions to narrow the disparate gap in screening and mortality rates.

p53 basic C terminus regulates p53 functions through DNA binding modulation of subset of target genes

The p53 gene encodes a transcription factor that is composed of several functional domains: the N-terminal transactivation domain, the central sequence-specific DNA binding domain, the tetramerization domain, and the highly basic C-terminal regulatory domain (CTD). The p53 CTD is a nonspecific DNA binding domain that is subject to extensive post-translational modifications. However, the functional significance of the p53 CTD remains unclear. The role of this domain in the regulation of p53 functions is explored by comparing the activity of ectopically expressed wild-type (WT) p53 protein to that of a truncated mutant lacking the 24 terminal amino acids (Δ24). Using quantitative real time PCR and chromatin Immuno-Precipitation experiments, a p53 CTD deletion is shown to alter the p53-dependent induction of a subset of its target genes due to impaired specific DNA binding. Moreover, p53-induced growth arrest and apoptosis both require an intact p53 CTD. These data indicate that the p53 CTD is a positive regulator of p53 tumor suppressor functions.

Glutathione synthesis is essential for mouse development but not for cell growth in culture

Glutathione (GSH) is a major source of reducing equivalents in mammalian cells. To examine the role of GSH synthesis in development and cell growth, we generated mice deficient in GSH by a targeted disruption of the heavy subunit of gamma-glutamylcysteine synthetase (gammaGCS-HS(tm1)), an essential enzyme in GSH synthesis. Embryos homozygous for gammaGCS-HS(tm1) fail to gastrulate, do not form mesoderm, develop distal apoptosis, and die before day 8.5. Lethality results from apoptotic cell death rather than reduced cell proliferation. We also isolated cell lines from homozygous mutant blastocysts in medium containing GSH. These cells also grow indefinitely in GSH-free medium supplemented with N-acetylcysteine and have undetectable levels of GSH; further, they show no changes in mitochondrial morphology as judged by electron microscopy. These data demonstrate that GSH is required for mammalian development but dispensable in cell culture and that the functions of GSH, not GSH itself, are essential for cell growth.