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Background and Aims: Colon cancer can occur sporadically or in the setting of chronic inflammation, such as in patients with inflammatory bowel disease. We previously showed that A20, a critical negative regulator of tumor necrosis factor signal transduction, could regulate sporadic colon cancer development. In this report, we investigate whether A20 also acts as a tumor suppressor in a model of colitis-associated cancer. Methods: Colitis and colitis-associated tumors were induced in wild-type and A20 intestinal epithelial cell-specific knockout (A20dIEC) mice using dextran sodium sulfate and azoxymethane. Clinicopathologic markers of inflammation were assessed in conjunction with colonic tumor burden. Gene expression analyses and immunohistochemistry were performed on colonic tissue and intestinal enteroids. Nitric oxide (NO) production and activity were assessed in whole colonic lysates and mouse embryonic fibroblasts. Results: A20dIEC mice develop larger tumors after treatment with dextran sodium sulfate and azoxymethane than wild-type mice. In addition to elevated markers of inflammation, A20dIEC mice have significantly enhanced expression of inducible nitric oxide synthase (iNOS), a well-known driver of neoplasia. Enhanced iNOS expression is associated with the formation of reactive nitrogen species and DNA damage. Loss of A20 also enhances NO-dependent cell death directly. Conclusion: Mechanistically, we propose that A20 normally restricts tumor necrosis factor–induced nuclear factor kappa B–dependent production of iNOS in intestinal epithelial cells, thereby protecting against colitis-associated tumorigenesis. We also propose that A20 plays a direct role in regulating NO-dependent cell death.

Abstract Cryptococcuria is a rare manifestation of localized cryptococcal disease. We present a case of Cryptococcus neoformans urinary tract infection in an immunocompromised host missed by routine laboratory workup. The patient had negative blood cultures, a negative serum cryptococcal antigen (CrAg), and “non-Candida yeast” growing in urine culture that was initially dismissed as non-pathogenic. The diagnosis was ultimately made by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) from a repeat urine culture after transfer to a tertiary care center. Cryptococcus should be considered in the differential of refractory urinary tract infections growing non-Candida yeast.

AbstractIntroduction:While previous studies have described career outcomes of physician-scientist trainees after graduation, trainee perceptions of research-intensive career pathways remain unclear. This study sought to identify the perceived interests, factors, and challenges associated with academic and research careers among predoctoral MD trainees, MD trainees with research-intense (>50%) career intentions (MD-RI), and MD-PhD trainees.Methods:A 70-question survey was administered to 16,418 trainees at 32 academic medical centers from September 2012 to December 2014. MD vs. MD-RI (>50% research intentions) vs. MD-PhD trainee responses were compared by chi-square tests. Multivariate logistic regression analyses were performed to identify variables associated with academic and research career intentions.Results:There were 4433 respondents (27% response rate), including 2625 MD (64%), 653 MD-RI (15%), and 856 MD-PhD (21%) trainees. MD-PhDs were most interested in pursuing academia (85.8%), followed by MD-RIs (57.3%) and MDs (31.2%). Translational research was the primary career intention for MD-PhD trainees (42.9%). Clinical duties were the primary career intention for MD-RIs (51.9%) and MDs (84.2%). While 39.8% of MD-PhD respondents identified opportunities for research as the most important career selection factor, only 12.9% of MD-RI and 0.5% of MD respondents shared this perspective. Interest in basic research, translational research, clinical research, education, and the ability to identify a mentor were each independently associated with academic career intentions by multivariate regression.Conclusions:Predoctoral MD, MD-RI, and MD-PhD trainees are unique cohorts with different perceptions and interests toward academic and research careers. Understanding these differences may help to guide efforts to mentor the next generation of physician-scientists.

ABSTRACT Microbial growth arrest can be triggered by diverse factors, one of which is energy limitation due to scarcity of electron donors or acceptors. Genes that govern fitness during energy-limited growth arrest and the extent to which they overlap between different types of energy limitation are poorly defined. In this study, we exploited the fact that Pseudomonas aeruginosa can remain viable over several weeks when limited for organic carbon (pyruvate) as an electron donor or oxygen as an electron acceptor. ATP values were reduced under both types of limitation, yet more severely in the absence of oxygen. Using transposon-insertion sequencing (Tn-seq), we identified fitness determinants in these two energy-limited states. Multiple genes encoding general functions like transcriptional regulation and energy generation were required for fitness during carbon or oxygen limitation, yet many specific genes, and thus specific activities, differed in their relevance between these states. For instance, the global regulator RpoS was required during both types of energy limitation, while other global regulators such as DksA and LasR were required only during carbon or oxygen limitation, respectively. Similarly, certain ribosomal and tRNA modifications were specifically required during oxygen limitation. We validated fitness defects during energy limitation using independently generated mutants of genes detected in our screen. Mutants in distinct functional categories exhibited different fitness dynamics: regulatory genes generally manifested a phenotype early, whereas genes involved in cell wall metabolism were required later. Together, these results provide a new window into how P. aeruginosa survives growth arrest. IMPORTANCE Growth-arrested bacteria are ubiquitous in nature and disease yet understudied at the molecular level. For example, growth-arrested cells constitute a major subpopulation of mature biofilms, serving as an antibiotic-tolerant reservoir in chronic infections. Identification of the genes required for survival of growth arrest (encompassing entry, maintenance, and exit) is an important first step toward understanding the physiology of bacteria in this state. Using Tn-seq, we identified and validated genes required for fitness of Pseudomonas aeruginosa when energy limited for organic carbon or oxygen, which represent two common causes of growth arrest for P. aeruginosa in diverse habitats. This unbiased, genome-wide survey is the first to reveal essential activities for a pathogen experiencing different types of energy limitation, finding both shared and divergent activities that are relevant at different survival stages. Future efforts can now be directed toward understanding how the biomolecules responsible for these activities contribute to fitness under these conditions.