AMP-activated protein kinase is necessary for Treg cell functional adaptation to microenvironmental stress.

CD4+FOXP3+ regulatory T (Treg) cells maintain self-tolerance, suppress the immune response to cancer, and protect against tissue injury in the lung and other organs. Treg cells require mitochondrial metabolism to exert their function, but how Treg cells adapt their metabolic programs to sustain and optimize their function during an immune response occurring in a metabolically stressed microenvironment remains unclear. Here, we tested whether Treg cells require the energy homeostasis-maintaining enzyme AMP-activated protein kinase (AMPK) to adapt to metabolically aberrant microenvironments caused by malignancy or lung injury, finding that AMPK is dispensable for Treg cell immune-homeostatic function but is necessary for full Treg cell function in B16 melanoma tumors and during acute lung injury caused by influenza virus pneumonia. AMPK-deficient Treg cells had lower mitochondrial mass and exhibited an impaired ability to maximize aerobic respiration. Mechanistically, we found that AMPK regulates DNA methyltransferase 1 to promote transcriptional programs associated with mitochondrial function in the tumor microenvironment. In the lung during viral pneumonia, we found that AMPK sustains metabolic homeostasis and mitochondrial activity. Induction of DNA hypomethylation was sufficient to rescue mitochondrial mass in AMPK-deficient Treg cells, linking DNA methylation with AMPK function and mitochondrial metabolism. These results define AMPK as a determinant of Treg cell adaptation to metabolic stress and offer potential therapeutic targets in cancer and tissue injury.

Epigenetic Control of Regulatory T Cell Stability and Function: Implications for Translation.

FoxP3+ regulatory T (Treg) cells maintain immune homeostasis, promote self-tolerance, and have an emerging role in resolving acute inflammation, providing tissue protection, and repairing tissue damage. Some data suggest that FoxP3+ T cells are plastic, exhibiting susceptibility to losing their function in inflammatory cytokine-rich microenvironments and paradoxically contributing to inflammatory pathology. As a result, plasticity may represent a barrier to Treg cell immunotherapy. Here, we discuss controversies surrounding Treg cell plasticity and explore determinants of Treg cell stability in inflammatory microenvironments, focusing on epigenetic mechanisms that clinical protocols could leverage to enhance efficacy and limit toxicity of Treg cell-based therapeutics.

Aging imparts cell-autonomous dysfunction to regulatory T cells during recovery from influenza pneumonia.

Regulatory T (Treg) cells orchestrate resolution and repair of acute lung inflammation and injury after viral pneumonia. Compared with younger patients, older individuals experience impaired recovery and worse clinical outcomes after severe viral infections, including influenza and SARS coronavirus 2 (SARS-CoV-2). Whether age is a key determinant of Treg cell prorepair function after lung injury remains unknown. Here, we showed that aging results in a cell-autonomous impairment of reparative Treg cell function after experimental influenza pneumonia. Transcriptional and DNA methylation profiling of sorted Treg cells provided insight into the mechanisms underlying their age-related dysfunction, with Treg cells from aged mice demonstrating both loss of reparative programs and gain of maladaptive programs. Strategies to restore youthful Treg cell functional programs could be leveraged as therapies to improve outcomes among older individuals with severe viral pneumonia.

The positive predictive value of "suspicious for high-grade urothelial carcinoma" in urinary tract cytology specimens: A single-institution study of 665 cases.

BACKGROUND: "The Paris System" proposes a 7-tier classification system for urine cytology. Establishing the risk of malignancy (ROM) associated with these diagnostic categories is essential to determine the appropriate management of patients. The objective of this study was to determine the ROM associated with the "positive" and "suspicious" categories. METHODS: The authors searched their electronic records for urine cytology specimens that had been diagnosed as "positive" or "suspicious" for high-grade urothelial carcinoma within an 11-year time frame. Then, the ROM was determined for these specimens within a 6-month follow-up interval. The cytologic diagnoses were correlated with surgical biopsy results, follow-up cytology results, and/or fluorescence in situ hybridization (FISH) results. RESULTS: In total, 662 specimens (487 "positive" and 175 "suspicious"), corresponding to 387 patients (295 men and 92 women), were included. The majority of specimens were collected by bladder washing (568 of 662 specimens; 85.4%) and for the indication of surveillance (601 of 662 specimens; 82%). On follow-up, bladder washing specimens were positive more often positive than voided urine specimens (466 of 570 [81.8%] vs 60 of 92 [65.2%]; P = .0005), and surveillance specimens were more often positive than specimens collected for other indications (82% vs 54.1%). The overall positive predictive value was higher for positive specimens than for suspicious specimens (365 of 461 [79.2%] vs 83 of 150 [55.3%]; P < .0001). CONCLUSIONS: Diagnoses of suspicious for high-grade urothelial carcinoma, as used at the authors' institution, have an ROM that is high but is lower than that for the "positive" category. Therefore, the authors suggest keeping the 2 categories separate, although management should be aggressive in both groups. Cancer Cytopathol 2016;124:811-9. © 2016 American Cancer Society.