Oxygen Sensing by T Cells Establishes an Immunologically Tolerant Metastatic Niche.

Cancer cells must evade immune responses at distant sites to establish metastases. The lung is a frequent site for metastasis. We hypothesized that lung-specific immunoregulatory mechanisms create an immunologically permissive environment for tumor colonization. We found that T-cell-intrinsic expression of the oxygen-sensing prolyl-hydroxylase (PHD) proteins is required to maintain local tolerance against innocuous antigens in the lung but powerfully licenses colonization by circulating tumor cells. PHD proteins limit pulmonary type helper (Th)-1 responses, promote CD4(+)-regulatory T (Treg) cell induction, and restrain CD8(+) T cell effector function. Tumor colonization is accompanied by PHD-protein-dependent induction of pulmonary Treg cells and suppression of IFN-γ-dependent tumor clearance. T-cell-intrinsic deletion or pharmacological inhibition of PHD proteins limits tumor colonization of the lung and improves the efficacy of adoptive cell transfer immunotherapy. Collectively, PHD proteins function in T cells to coordinate distinct immunoregulatory programs within the lung that are permissive to cancer metastasis. PAPERCLIP.

BACH2 regulates CD8(+) T cell differentiation by controlling access of AP-1 factors to enhancers.

T cell antigen receptor (TCR) signaling drives distinct responses depending on the differentiation state and context of CD8(+) T cells. We hypothesized that access of signal-dependent transcription factors (TFs) to enhancers is dynamically regulated to shape transcriptional responses to TCR signaling. We found that the TF BACH2 restrains terminal differentiation to enable generation of long-lived memory cells and protective immunity after viral infection. BACH2 was recruited to enhancers, where it limited expression of TCR-driven genes by attenuating the availability of activator protein-1 (AP-1) sites to Jun family signal-dependent TFs. In naive cells, this prevented TCR-driven induction of genes associated with terminal differentiation. Upon effector differentiation, reduced expression of BACH2 and its phosphorylation enabled unrestrained induction of TCR-driven effector programs.

The utility of intraoperative marrow margin frozen section in extremity bone sarcoma resection.

BACKGROUND AND OBJECTIVES: Intraoperative frozen section analysis is commonly used to evaluate marrow margins during extremity bone sarcoma resections, but its efficacy in the era of magnetic resonance imaging is debated. This study aimed to compare the accuracy of intraoperative frozen section assessment with final pathology, assess its correlation with gross intraoperative margin assessment, and evaluate its impact on surgical decision making. METHODS: Consecutive patients undergoing extremity bone sarcoma resections from 2010 to 2022 at a single sarcoma center were included. Intraoperative frozen section and gross margin assessments were compared to final pathology using positive predictive values (PPV) and negative predictive values (NPV). Changes in surgical decisions due to positive intraoperative margins were recorded. RESULTS: Of 166 intraoperative frozen section marrow margins, four were indeterminant/positive, with two false positive/indeterminant findings and two false negatives compared to final pathology. Gross intraoperative assessment had no false positives and two false negatives. Frozen section analysis yielded a PPV of 50% (95% confidence interval [CI]: 16%-84%) and NPV of 98.8% (95% CI: 97%-100%), while gross assessment had a PPV of 100% (95% CI: 16%-100%) and NPV of 98.8% (95% CI: 97%-100%). Positive frozen section margins led to additional resections in three of four cases. CONCLUSIONS: Intraoperative frozen section analysis did not offer added clinical value beyond gross margin assessment in extremity bone sarcoma resections. It exhibited a low PPV and led to unnecessary additional resections. Gross intraoperative assessment proved adequate for margin evaluation, potentially saving time and resources.

The Role of Routine Pathologic Assessment After Pediatric Osteochondroma Excision.

BACKGROUND: Osteochondromas are benign osseous lesions often excised for pain, growth abnormalities, and aesthetic concerns. While characteristic clinical and radiographic features leave little diagnostic ambiguity in most cases of osteochondroma, pathologic analysis to confirm the diagnosis and screen for malignancy is routinely performed following surgical excision. The purpose of this study was to determine the clinical and economic value of routine pathologic analysis after osteochondroma excision in a pediatric population. METHODS: A retrospective review of clinical records from 2 pediatric orthopaedic hospitals (St. Louis Children's Hospital and Shriner's Hospital for Children, St. Louis) identified 426 osteochondroma lesions surgically resected from 201 patients. Patients with solitary and multiple lesions were included. Clinical, radiographic, and surgical data were recorded for each resection surgery. Pathologic reports were evaluated. Costs incurred for routine pathologic assessment was also noted. RESULTS: Totally, 132 patients were treated with surgical resection of a solitary osteochondroma lesion, while an additional 291 lesions were resected from 69 patients with multiple lesions. Average age at the time of surgical resection was 13.0 years (2.1 to 17.9). The most common anatomic locations of excised lesions included the distal femur (110, 25.8%), proximal tibia/fibula (95, 22.3%), and distal radius/ulna (58, 13.6%). All resected specimens were sent for pathologic analysis. The average size of the resected lesions was 19.9 mm 3 (0.02 to 385.0 mm 3 ). In all cases, the histologic diagnosis confirmed benign osteochondroma. The total charges of pathologic analysis including processing and interpretation fees was ∼$755.00 for each lesion assessed, for a total cohort charge of $321,630. CONCLUSION: We propose that in most cases of pediatric osteochondroma excision procedures, postoperative histologic analysis is not strictly indicated as it rarely, if ever, alters diagnosis or management. We suggest using a "gross only" analysis in these cases. However, we do believe that with preoperative diagnostic ambiguity, or if patients present with concerning features such as rapidly expansile lesions or cortical destruction, have axial skeleton or pelvic involvement, or enlarged cartilaginous caps, full histologic evaluation of the excised lesions will continue to be prudent. LEVEL OF EVIDENCE: Level IV-case series.

Ionic immune suppression within the tumour microenvironment limits T cell effector function.

Tumours progress despite being infiltrated by tumour-specific effector T cells. Tumours contain areas of cellular necrosis, which are associated with poor survival in a variety of cancers. Here, we show that necrosis releases intracellular potassium ions into the extracellular fluid of mouse and human tumours, causing profound suppression of T cell effector function. Elevation of the extracellular potassium concentration ([K+]e) impairs T cell receptor (TCR)-driven Akt-mTOR phosphorylation and effector programmes. Potassium-mediated suppression of Akt-mTOR signalling and T cell function is dependent upon the activity of the serine/threonine phosphatase PP2A. Although the suppressive effect mediated by elevated [K+]e is independent of changes in plasma membrane potential (Vm), it requires an increase in intracellular potassium ([K+]i). Accordingly, augmenting potassium efflux in tumour-specific T cells by overexpressing the potassium channel Kv1.3 lowers [K+]i and improves effector functions in vitro and in vivo and enhances tumour clearance and survival in melanoma-bearing mice. These results uncover an ionic checkpoint that blocks T cell function in tumours and identify potential new strategies for cancer immunotherapy.

Pilot Study Analysis of Serum Cytokines to Differentiate Pediatric Septic Arthritis and Transient Synovitis.

BACKGROUND: In pediatric patients, the presentation of the nontraumatic acutely painful joint/limb poses a diagnostic dilemma due to the similarity of presentations of the most likely diagnoses [septic arthritis (SA), transient synovitis (TS), osteomyelitis]. Current tools employed to differentiate these diagnoses rely on nonspecific inflammatory markers, radiologic imaging, and arthrocentesis. Diagnostic algorithms utilizing these clinical, radiographic, and biochemical parameters have produced conflicting results. The purpose of this study was to identify a serum-based inflammatory signature which can differentiate SA from TS in pediatric patients. METHODS: Serum samples were collected from 22 pediatric patients presenting with joint/extremity pain whose working diagnosis included SA or TS. Each sample was analyzed for serum abundance of 72 distinct biomarkers and cytokines using enzyme linked immunosorbent assay based arrays. Linear discriminant analysis was performed to identify a combinatorial biomarker panel to predict a diagnosis of SA or TS. Efficacy of the biomarker panel was compared with definitive diagnoses as based on laboratory tests, arthrocentesis results, and clinical scenario. RESULTS: At the time of presentation: (1) mean erythrocyte sedimentation rate in the SA group was 56.6 mm/h and 12.4 mm/h in the TS group (P<0.001), (2) mean C-reactive protein was 55.9 mg/dL in the SA group and 13.7 mg/dL in the TS group (P=0.12), and (3) mean white blood cell was 10.9 k/mm3 in the SA group and 11.0 k/mm3 in the TS group (P=0.95). A combined panel of 72 biomarkers was examined using discriminant analysis to identify a limited set of predictors which could accurately predict whether a patient was diagnosed with SA or TS. A diagnostic algorithm consisting of transforming growth factor alpha, interleukin (IL)-7, IL-33, and IL-28A serum concentration correctly classified 20 of the 22 cases with a sensitivity and specificity of 90.9% (95% confidence interval: 73.9%-100.0%). CONCLUSION: This study identifies a novel serum-based 4-cytokine panel that accurately differentiates SA from TS in pediatric patients with joint/limb pain. LEVEL OF EVIDENCE: Level II-diagnostic study.

BACH2 represses effector programs to stabilize T(reg)-mediated immune homeostasis.

Through their functional diversification, distinct lineages of CD4(+) T cells can act to either drive or constrain immune-mediated pathology. Transcription factors are critical in the generation of cellular diversity, and negative regulators antagonistic to alternate fates often act in conjunction with positive regulators to stabilize lineage commitment. Genetic polymorphisms within a single locus encoding the transcription factor BACH2 are associated with numerous autoimmune and allergic diseases including asthma, Crohn's disease, coeliac disease, vitiligo, multiple sclerosis and type 1 diabetes. Although these associations point to a shared mechanism underlying susceptibility to diverse immune-mediated diseases, a function for BACH2 in the maintenance of immune homeostasis has not been established. Here, by studying mice in which the Bach2 gene is disrupted, we define BACH2 as a broad regulator of immune activation that stabilizes immunoregulatory capacity while repressing the differentiation programs of multiple effector lineages in CD4(+) T cells. BACH2 was required for efficient formation of regulatory (Treg) cells and consequently for suppression of lethal inflammation in a manner that was Treg-cell-dependent. Assessment of the genome-wide function of BACH2, however, revealed that it represses genes associated with effector cell differentiation. Consequently, its absence during Treg polarization resulted in inappropriate diversion to effector lineages. In addition, BACH2 constrained full effector differentiation within TH1, TH2 and TH17 cell lineages. These findings identify BACH2 as a key regulator of CD4(+) T-cell differentiation that prevents inflammatory disease by controlling the balance between tolerance and immunity.

miR-155 augments CD8+ T-cell antitumor activity in lymphoreplete hosts by enhancing responsiveness to homeostatic γc cytokines.

Lymphodepleting regimens are used before adoptive immunotherapy to augment the antitumor efficacy of transferred T cells by removing endogenous homeostatic "cytokine sinks." These conditioning modalities, however, are often associated with severe toxicities. We found that microRNA-155 (miR-155) enabled tumor-specific CD8(+) T cells to mediate profound antitumor responses in lymphoreplete hosts that were not potentiated by immune-ablation. miR-155 enhanced T-cell responsiveness to limited amounts of homeostatic γc cytokines, resulting in delayed cellular contraction and sustained cytokine production. miR-155 restrained the expression of the inositol 5-phosphatase Ship1, an inhibitor of the serine-threonine protein kinase Akt, and multiple negative regulators of signal transducer and activator of transcription 5 (Stat5), including suppressor of cytokine signaling 1 (Socs1) and the protein tyrosine phosphatase Ptpn2. Expression of constitutively active Stat5a recapitulated the survival advantages conferred by miR-155, whereas constitutive Akt activation promoted sustained effector functions. Our results indicate that overexpression of miR-155 in tumor-specific T cells can be used to increase the effectiveness of adoptive immunotherapies in a cell-intrinsic manner without the need for life-threatening, lymphodepleting maneuvers.

Reprogramming antitumor immunity.

Regenerative medicine holds great promise in replacing tissues and organs lost to degenerative disease and injury. Application of the principles of cellular reprogramming for the treatment of cancer, however, is not well established. Here, we present an overview of cellular reprogramming techniques used in regenerative medicine, and within this context, envision how the scope of regenerative medicine may be expanded to treat metastatic cancer by revitalizing an exhausted and senescent immune system.

Cancer-associated fibroblast-derived Dickkopf-1 suppresses NK cell cytotoxicity in breast cancer.

Breast cancer is poorly immunogenic, hence able to evade T cell recognition and respond poorly to immune checkpoint blockade. Breast cancer cells can also evade NK cell-mediated immune surveillance, but the mechanism remains enigmatic. Dickkopf-1 (DKK1) is a Wnt/b-catenin inhibitor, whose levels are increased in breast cancer patients and correlate with reduced overall survival. DKK1 is expressed by cancer-associated fibroblasts (CAFs) in orthotopic breast tumors and patient samples, and at higher levels by bone cells. While bone-derived DKK1 contributes to the systemic elevation of DKK1 in tumor-bearing mice, CAFs represent the primary source of DKK1 at the tumor site. Systemic or bone-specific DKK1 targeting reduces primary tumor growth. Intriguingly, specific deletion of CAF-derived DKK1 also limits breast cancer progression, regardless of its elevated levels in circulation and in the bone. DKK1 does not support tumor proliferation directly but rather suppresses the activation and tumoricidal activity of NK cells. Importantly, increased DKK1 levels and reduced number of cytotoxic NK cells are detected in breast cancer patients with progressive bone metastases compared to those with stable disease. Our findings indicate that DKK1 creates a tumor-supporting environment through the suppression of NK cells in breast cancer.