Early phase trials targeting the T-cell inhibitory molecule PD-L1 have shown clinical efficacy in cancer. This study was undertaken to determine whether PD-L1 is overexpressed in triple-negative breast cancer (TNBC) and to investigate the loss of the phosphatase and tensin homolog (PTEN) as a mechanism of PD-L1 regulation. The Cancer Genome Atlas (TCGA) RNA sequencing data showed significantly greater expression of the PD-L1 gene in TNBC (n=120) compared to non-TNBC (n=716) (P<0.001). Breast tumor tissue microarrays were evaluated for PD-L1 expression which was present in 19% (20 of 105) TNBC specimens. PD-L1+ tumors had greater CD8+ T-cell infiltrate than PD-L1− tumors (688 cells/mm versus 263 cells/mm; P<0.0001). To determine the effect of PTEN loss on PD-L1 expression, stable cell lines were generated using PTEN shRNA. PTEN knockdown led to significantly higher cell-surface PD-L1 expression and PD-L1 transcripts, suggesting transcriptional regulation. Moreover, PI3K pathway inhibition using the AKT inhibitor MK-2206 or rapamycin resulted in decreased PD-L1 expression, further linking PTEN and PI3K signaling to PD-L1 regulation. Co-culture experiments were performed to determine the functional effect of altered PD-L1 expression. Increased PD-L1 cell surface expression by tumor cells induced by PTEN loss led to decreased T cell proliferation and increased apoptosis. PD-L1 is expressed in 20% of TNBC, suggesting PD-L1 as a therapeutic target in TNBC. Since PTEN loss is one mechanism regulating PD-L1 expression, agents targeting the PI3K pathway may increase the antitumor adaptive immune responses.

IMPORTANCEThe role of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor blockers (ARB) in the setting of the coronavirus disease 2019 (COVID-19) pandemic is hotly debated. There have been recommendations to discontinue these medications, which are essential in the treatment of several chronic disease conditions, while, in the absence of clinical evidence, professional societies have advocated their continued use. OBJECTIVE To study the association between use of ACEIs/ARBs with the likelihood of testing positive for COVID-19 and to study outcome data in subsets of patients taking ACEIs/ARBs who tested positive with severity of clinical outcomes of COVID-19 (eg, hospitalization, intensive care unit admission, and requirement for mechanical ventilation). DESIGN, SETTING, AND PARTICIPANTS Retrospective cohort study with overlap propensity score weighting was conducted at the Cleveland Clinic Health System in Ohio and Florida. All patients tested for COVID-19 between March 8 and April 12, 2020, were included. EXPOSURES History of taking ACEIs or ARBs at the time of COVID-19 testing. MAIN OUTCOMES AND MEASURES Results of COVID-19 testing in the entire cohort, number of patients requiring hospitalizations, intensive care unit admissions, and mechanical ventilation among those who tested positive.RESULTS A total of 18 472 patients tested for COVID-19. The mean (SD) age was 49 (21) years, 7384 (40%) were male, and 12 725 (69%) were white. Of 18 472 patients who underwent COVID-19 testing, 2285 (12.4%) were taking either ACEIs or ARBs. A positive COVID-19 test result was observed in 1735 of 18 472 patients (9.4%). Among patients who tested positive, 421 (24.3%) were admitted to the hospital, 161 (9.3%) were admitted to an intensive care unit, and 111 (6.4%) required mechanical ventilation. Overlap propensity score weighting showed no significant association of ACEI and/or ARB use with COVID-19 test positivity (overlap propensity score-weighted odds ratio, 0.97; 95% CI, 0.81-1.15). CONCLUSIONS AND RELEVANCEThis study found no association between ACEI or ARB use and COVID-19 test positivity. These clinical data support current professional society guidelines to not discontinue ACEIs or ARBs in the setting of the COVID-19 pandemic. However, further study in larger numbers of hospitalized patients receiving ACEI and ARB therapy is needed to determine the association with clinical measures of COVID-19 severity.

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We investigated the influence of PD-1 expression on the systemic antitumor response (abscopal effect) induced by stereotactic ablative radiotherapy (SABR) in preclinical melanoma and renal cell carcinoma models. We compared the SABRinduced antitumor response in PD-1-expressing wild-type (WT) and PD-1-deficient knockout (KO) mice and found that PD-1 expression compromises the survival of tumor-bearing mice treated with SABR. None of the PD-1 WT mice survived beyond 25 days, whereas 20% of the PD-1 KO mice survived beyond 40 days. Similarly, PD-1-blocking antibody in WT mice was able to recapitulate SABR-induced antitumor responses observed in PD-1 KO mice and led to increased survival. The combination of SABR plus PD-1 blockade induced near complete regression of the irradiated primary tumor (synergistic effect), as opposed to SABR alone or SABR plus control antibody. The combination of SABR plus PD-1 blockade therapy elicited a 66% reduction in size of nonirradiated, secondary tumors outside the SABR radiation field (abscopal effect). The observed abscopal effect was tumor specific and was not dependent on tumor histology or host genetic background. The CD11a high CD8 þ T-cell phenotype identifies a tumor-reactive population, which was associated in frequency and function with a SABR-induced antitumor immune response in PD-1 KO mice. We conclude that SABR induces an abscopal tumorspecific immune response in both the irradiated and nonirradiated tumors, which is potentiated by PD-1 blockade. The combination of SABR and PD-1 blockade has the potential to translate into a potent immunotherapy strategy in the management of patients with metastatic cancer.

Enteroaggregative Escherichia coli (EAEC) is emerging as a significant diarrheal pathogen in multiple population groups. Although most commonly associated with pediatric diarrhea in developing countries, EAEC is also linked to diarrhea in adults including HIV-positive patients and travelers and has been a cause of food-borne outbreaks in the industrialized world. Current data suggest that one set of virulence elements is not associated with all EAEC strains, but that combinations of multiple factors prevail. Pathogenesis is believed to be initiated with adherence to the terminal ileum and colon in an aggregative, stacked-brick-type pattern by means of one of several different hydrophobic aggregative adherence fimbriae. Some strains of EAEC may then elaborate cytotoxins including the plasmid-encoded toxin and the enterotoxins, EAST1 and ShET1. An AraC homolog termed AggR regulates several genes contributing to fimbrial biogenesis in 'typical EAEC strains'. AggR has now also been shown to regulate genes on a chromosomal island. Sequencing of the EAEC type strain 042 completed at the Sanger Center has revealed two other chromosomal islands that are being explored for their pathogenetic potential. This article reviews these virulence elements and presents on-going areas of research in EAEC pathogenesis.

The tumor microenvironments of paired primary lung cancers and brain metastases are significantly different, such that many of the metastases lose PD-L1 expression, lymphocyte infiltration or both with greater discrepancies over time. The spatial and temporal heterogeneity of PD-L1 expression may limit its use as a tissue-based predictive biomarker in lung cancer.

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Introduction B7 homolog 1 [B7-H1; aka programmed cell death 1 ligand 1 (PD-L1)] is a negative costimulatory molecule that is associated with poor prognosis in many tumor types. Given the poor prognosis and the limited treatments available for mesothelioma, we decided to examine B7-H1 expression and its association with survival in patients with mesothelioma. Methods Expression of B7-H1 was determined in 106 patients using a mouse monoclonal anti-human B7-H1 (clone 5H1-A3) antibody with immunohistochemistry. Positive expression was defined as ≥5% positively-stained cells. Clinicopathologic features and survival were compared between B7-H1 positive and negative groups. Results Malignant mesotheliomas of 42 patients (40%) expressed B7-H1. Patients with B7-H1-postive tumors were less likely to be offered or undergo therapeutic surgery (p=0.03). All sarcomatoid mesotheliomas except one desmoplastic subtype expressed B7-H1. Survival was significantly decreased for patients whose tumors expressed B7-H1 (5 months median, 2-9.5 months interquartile range) compared to those whose tumors did not (14.5 months, 9.25-19 months; p<0.0001). In a multivariate model, B7-H1 expression and sarcomatoid mesothelioma remained significantly associated with worse survival [risk ratio 1.71, 95% CI 1.03-2.78 (p=0.04) and risk ratio 2.18, 1.08-4.23 (p=0.03) respectively]. Conclusions B7-H1 is expressed in a substantial proportion of malignant pleural mesotheliomas and is associated with poor survival. Almost all malignant pleural mesotheliomas with sarcomatoid differentiation expressed B7-H1. The expression of B7-H1 may have important therapeutic implications for the management of malignant pleural mesothelioma.