Immune checkpoint inhibitors (ICIs) have obtained durable responses in many cancers, making it possible to foresee their potential in improving the health of cancer patients. However, immunotherapies are currently limited to a minority of patients and there is a need to develop a better understanding of the basic molecular mechanisms and functions of pivotal immune regulatory molecules. Immune checkpoint cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and regulatory T (Treg) cells play pivotal roles in hindering the anticancer immunity. Treg cells suppress antigen-presenting cells (APCs) by depleting immune stimulating cytokines, producing immunosuppressive cytokines and constitutively expressing CTLA-4. CTLA-4 molecules bind to CD80 and CD86 with a higher affinity than CD28 and act as competitive inhibitors of CD28 in APCs. The purpose of this review is to summarize state-of-the-art understanding of the molecular mechanisms underlining CTLA-4 immune regulation and the correlation of the ICI response with CTLA-4 expression in Treg cells from preclinical and clinical studies for possibly improving CTLA-4-based immunotherapies, while highlighting the knowledge gap.

Background. Glucocorticoids (GCs) have been shown to reduce mortality and the need for invasive mechanical ventilation (IMV) in SARS-CoV-2-induced acute respiratory distress syndrome (ARDS). It has been suggested that serum cytokines levels are markers of disease severity in ARDS, although there is only limited evidence of a relationship between the longitudinal cytokine profile and clinical outcomes in patients with SARS-CoV-2-induced ARDS treated with GC. Methods. We conducted a single-center observational study to investigate serial plasma cytokine levels in 17 patients supported with non-invasive ventilation (NIV) in order to compare the response in five patients who progressed to IMV versus 12 patients who continued with NIV alone. All patients received methylprednisolone 80 mg/day continuous infusion until clinical improvement. Results. The study groups were comparable at baseline. All patients survived. Although IL-6 was higher in the NIV group at baseline, several cytokines were significantly higher in the IMV group on day 7 (IL-6, IL-8, IL-9, G-CSF, IP-10, MCP-1, MIP-1α) and 14 (IL-6, IL-8, IL-17, G-CSF, MIP-1α, RANTES). No significant differences were observed between groups on day 28. Conclusions. Patients in the IMV group had higher inflammation levels at intubation than the NIV group, which may indicate a higher resistance to glucocorticoids. Higher GC doses or a longer treatment duration in these patients might have allowed for a better control of inflammation and a better outcome. Further studies are required to define the prognostic value of cytokine patterns, in terms of both GC treatment tailoring and timely initiation of IMV.

Background: There is uncertainty as to the contribution of cancer patients' features on severity and mortality from Covid-19 and little guidance as to the role of anticancer and anti-Covid-19 therapy in this population.Methods: OnCovid is a retrospective observational study conducted across 19 European centers that recruited cancer patients aged >18 and diagnosed with Covid-19 between 26/02 and 01/04/2020. Uni-and multivariable regression models were used to evaluate predictors of Covid-19 severity and mortality.Results: We identified 890 patients from UK (n¼218, 24%), Italy (n¼343, 37%), Spain (n¼323, 36%) and Germany (n¼6, 1%). Most patients were male (n¼503, 56%) had a diagnosis of solid malignancy (n¼753, 84%) and 556 (62%) had active disease. Mean (AESD) patient age was 68AE13 years, and 670 (75%) had >1 co-morbidity, most commonly hypertension (n¼386, 43%). Commonest presenting symptoms were fever (n¼569, 63%) and cough (n¼448, 50%), beginning 6.3 (AE9.5 SD) days before diagnosis. Most patients (n¼565, 63%) had >1 complication from Covid-19, including respiratory failure (n¼527, 59%) and acute respiratory distress syndrome (n¼127, 22%). In total, 110 patients (14%) were escalated to high-dependency or intensive care. At time of analysis, 299 patients had died (33%). Multi-variate logistic regression identified male gender, age>65 (p<0.0001) presence of >2 comorbidities (p¼0.001) active malignancy (p¼0.07) as predictors of complicated Covid-19. Mortality was associated with active malignancy (p<0.0001), age>65 and co-morbid burden (p¼0.002). Provision of chemotherapy, targeted therapy or immunotherapy was not associated with higher mortality. Exposure to anti-malarials alone (chloroquine/ hydroxychloroquine, n¼182, p<0.001) or in combination with anti-virals (n¼195, p<0.001) or tocilizumab (n¼51, p¼0.004) was associated with improved mortality compared to patients who did not receive any of these therapies (n¼446) independent of patients' gender, age, tumour stage and severity of Covid-19.Conclusions: This study highlights the clinical utility of demographic factors for individualized risk-stratification of patients and supports further research into emerging anti Covid-19 therapeutics in SARS-Cov-2 infected cancer patients. Clinical trial identification: NCT04393974.Legal entity responsible for the study: Imperial College London.

The role of HER4 in breast cancer is controversial and its role in relation to trastuzumab resistance remains unclear. We showed that trastuzumab treatment and its acquired resistance induced HER4 upregulation, cleavage and nuclear translocation. However, knockdown of HER4 by specific siRNAs increased trastuzumab sensitivity and reversed its resistance in HER2 positive breast cancer cells. Preventing HER4 cleavage by a γ-secretase inhibitor and inhibiting HER4 tyrosine kinase activity by neratinib decreased trastuzumab-induced HER4 nuclear translocation and enhanced trastuzumab response. There was also increased nuclear HER4 staining in the tumours from BT474 xenograft mice and human patients treated with trastuzumab. Furthermore, nuclear HER4 predicted poor clinical response to trastuzumab monotherapy in patients undergoing a window study and was shown to be an independent poor prognostic factor in HER2 positive breast cancer. Our data suggest that HER4 plays a key role in relation to trastuzumab resistance in HER2 positive breast cancer. Therefore, our study provides novel findings that HER4 activation, cleavage and nuclear translocation influence trastuzumab sensitivity and resistance in HER2 positive breast cancer. Nuclear HER4 could be a potential prognostic and predictive biomarker and understanding the role of HER4 may provide strategies to overcome trastuzumab resistance in HER2 positive breast cancer.

IMPORTANCEThe cyclin-dependent kinase 4 and 6 inhibitor palbociclib in combination with letrozole has become a standard first-line treatment for patients with endocrine-sensitive, hormone receptor-positive, ERBB2-negative advanced breast cancer. Meanwhile, the antiestrogen fulvestrant was shown to be superior to anastrozole in the absence of cyclin-dependent kinase 4 and 6 inhibition for this patient population. OBJECTIVE To assess whether fulvestrant is superior to letrozole when combined with palbociclib in the first-line scenario. DESIGN, SETTING, AND PARTICIPANTSIn this international, randomized, open-label, phase 2 clinical study conducted from July 30, 2015, to January 8, 2018, patients with hormone receptor-positive, ERBB2-negative advanced breast cancer with no prior therapy in the metastatic setting and endocrine-sensitive criteria were recruited from 47 centers in 7 countries. Data were analyzed from February 11 to May 15, 2020.INTERVENTIONS Patients were randomly assigned (1:1 ratio) to receive palbociclib with either fulvestrant or letrozole. Stratification factors were type of disease presentation (de novo vs recurrent) and the presence of visceral involvement (yes vs no). MAIN OUTCOMES AND MEASURESThe primary end point was investigator-assessed progression-free survival determined by Response Evaluation Criteria in Solid Tumors, version 1.1.RESULTS A total of 486 women (median age, 63 years [range, 25-90 years]; 3 Asian women [0.6%]; 4 Black women [0.8%]; 461 White women [94.9%]; 18 women of unknown race [3.7%]) were randomized (243 to fulvestrant-palbociclib and 243 to letrozole-palbociclib). Median investigator-assessed progression-free survival was 27.9 months (95% CI, 24.2-33.1 months) in the fulvestrant-palbociclib group vs 32.8 months (95% CI, 25.8-35.9 months) in the letrozole-palbociclib group (hazard ratio, 1.13; 95% CI, 0.89-1.45; P = .32). This result was consistent across the stratification factors. No significant differences were observed in objective response rate (46.5% vs 50.2%) and 3-year overall survival rate (79.4% vs 77.1%) for fulvestrant-palbociclib and letrozole-palbociclib, respectively. Grade 3-4 adverse events were comparable among treatment groups, and no new safety signals were identified. No treatment-related deaths were reported. CONCLUSIONS AND RELEVANCEAlthough fulvestrant-palbociclib demonstrated significant antitumor activity, this randomized clinical trial failed to identify an improvement in progression-free survival with this regimen over letrozole-palbociclib in patients with endocrine-sensitive, hormone receptor-positive, ERBB2-negative advanced breast cancer.