The quantity of tumor-infiltrating lymphocytes (TILs) in breast cancer (BC) is a robust prognostic factor for improved patient survival, particularly in triple-negative and HER2-overexpressing BC subtypes. Although T cells are the predominant TIL population, the relationship between quantitative and qualitative differences in T cell subpopulations and patient prognosis remains unknown. We performed single-cell RNA sequencing (scRNA-seq) of 6,311 T cells isolated from human BCs and show that significant heterogeneity exists in the infiltrating T cell population. We demonstrate that BCs with a high number of TILs contained CD8 T cells with features of tissue-resident memory T (T) cell differentiation and that these CD8 T cells expressed high levels of immune checkpoint molecules and effector proteins. A CD8 T gene signature developed from the scRNA-seq data was significantly associated with improved patient survival in early-stage triple-negative breast cancer (TNBC) and provided better prognostication than CD8 expression alone. Our data suggest that CD8 T cells contribute to BC immunosurveillance and are the key targets of modulation by immune checkpoint inhibition. Further understanding of the development, maintenance and regulation of T cells will be crucial for successful immunotherapeutic development in BC.

Background Anthracycline chemotherapy may be associated with decreased cardiac function and functional capacity measured as the peak oxygen uptake during exercise ([Formula: see text] peak). We sought to determine (a) whether a structured exercise training program would attenuate reductions in [Formula: see text] peak and (b) whether exercise cardiac imaging is a more sensitive marker of cardiac injury than the current standard of care resting left ventricular ejection fraction (LVEF). Methods Twenty-eight patients with early stage breast cancer undergoing anthracycline chemotherapy were able to choose between exercise training (mean ± SD age 47 ± 9 years, n = 14) or usual care (mean ± SD age 53 ± 9 years, n = 14). Measurements performed before and after anthracycline chemotherapy included cardiopulmonary exercise testing to determine [Formula: see text] peak and functional disability ([Formula: see text] peak < 18 ml/min/kg), resting echocardiography (LVEF and global longitudinal strain), cardiac biomarkers (troponin and B-type natriuretic peptide) and exercise cardiac magnetic resonance imaging to determine stroke volume and peak cardiac output. The exercise training group completed 2 × 60 minute supervised exercise sessions per week. Results Decreases in [Formula: see text] peak during chemotherapy were attenuated with exercise training (15 vs. 4% reduction, P = 0.010) and fewer participants in the exercise training group met the functional disability criteria after anthracycline chemotherapy compared with those in the usual care group (7 vs. 50%, P = 0.01). Compared with the baseline, the peak exercise heart rate was higher and the stroke volume was lower after chemotherapy ( P = 0.003 and P = 0.06, respectively). There was a reduction in resting LVEF (from 63 ± 5 to 60 ± 5%, P = 0.002) and an increase in troponin (from 2.9 ± 1.3 to 28.5 ± 22.4 ng/mL, P < 0.0001), but no difference was observed between the usual care and exercise training group. The baseline peak cardiac output was the strongest predictor of functional capacity after anthracycline chemotherapy in a model containing age and resting cardiac function (LVEF and global longitudinal strain). Conclusions The peak exercise cardiac output can identify patients at risk of chemotherapy-induced functional disability, whereas current clinical standards are unhelpful. Functional disability can be prevented with exercise training.

The majority of deaths from breast cancer occur following the development of metastatic disease, a process inhibited by b-blockers in preclinical studies. This phase II randomized controlled trial evaluated the effect of preoperative b-blockade with propranolol on biomarkers of metastatic potential and the immune cell profile within the primary tumor of patients with breast cancer.Patients and Methods: In this triple-blind placebo-controlled clinical trial, 60 patients were randomly assigned to receive an escalating dose of oral propranolol (n ¼ 30; 80-160 mg daily) or placebo (n ¼ 30) for 7 days prior to surgery. The primary endpoint investigated the effect of propranolol on prometastatic and proinflammatory gene expression within the primary tumor.Results: Propranolol downregulated primary tumor expression of mesenchymal genes (P ¼ 0.002) without affecting epithelial gene expression (P ¼ 0.21). Bioinformatic analyses implicated downregulation of Snail/Slug (P ¼ 0.03), NF-kB/Rel (P < 0.01), and AP-1 (P < 0.01) transcription factors in structuring the observed transcriptome alterations, and identified changes in intratumoral neutrophil, natural killer cell, and dendritic cell recruitment (all P < 0.01). Patients with clinical evidence of drug response (lowered heart rate and blood pressure) demonstrated elevated tumor infiltration of CD68 þ macrophages and CD8 þ T cells.Conclusions: One week of b-blockade with propranolol reduced intratumoral mesenchymal polarization and promoted immune cell infiltration in early-stage surgically-resectable breast cancer. These results show that b-blockade reduces biomarkers associated with metastatic potential, and support the need for larger phase III clinical trials powered to detect the impact of b-blockade on cancer recurrence and survival.See related commentary by Blaes et al., p. 1781

Background: Breast cancer (BC) survivors treated with anthracycline-based chemotherapy (AC) have increased risk of functional limitation and cardiac dysfunction. We conducted a 12-month randomized controlled trial in 104 early-stage BC patients scheduled for AC to determine if 12-months of exercise training (ExT) could attenuate functional disability (primary endpoint), improve cardiorespiratory fitness (VO 2 peak) and prevent cardiac dysfunction. Methods: Women aged 40-75 years with stage I-III BC scheduled for AC were randomized to 3-4 days/wk of aerobic and resistance ExT for 12-months (n = 52) or usual care ([ UC ], n = 52). Functional measures were performed at baseline, 4-weeks following AC (4-months) and at 12-months comprising: 1) cardiopulmonary exercise testing to quantify VO 2 peak and functional disability (VO 2 peak ≤18.0mL/kg/min), 2) cardiac reserve (response from rest to peak exercise) quantified using exercise cardiac magnetic resonance measures to determine changes in left- and right-ventricular ejection fraction [ LVEF, RVEF ], cardiac output [ CO ], and stroke volume [ SV ]), 3) standard-of-care echocardiography-derived resting LVEF and global longitudinal strain [ GLS ], and 4) biochemistry (troponin and B-type natriuretic peptide [ BNP ]). Results: Among 104 participants randomized, greater study attrition was observed among UC participants (P=0.031) with 93 women assessed at 4-months (ExT: n=49, UC: n=44) and 87 at 12-months (ExT: n=49, UC: n=38). ExT attenuated functional disability at 4-months (OR: 0.32 [95% CI 0.11, 0.94], P=0.03), but not at 12-months (OR: 0.27, [95% CI 0.06, 1.12], P=0.07). In a per-protocol analysis, functional disability was entirely prevented at 12-months among participants adherent to ExT (ExT: 0% vs. UC: 20%, P=0.005). As compared with UC at 12-months, ExT was associated with a net +3.5 mL/kg/min improvement in VO 2 peak that coincided with greater CO, SV, LVEF and RVEF reserve (P<0.001 for all). There was no effect of ExT on resting measures of LV function. Post-chemotherapy troponin increased less in ExT than UC (8-fold vs. 16-fold increase, P=0.002). There were no changes in BNP in either group. Conclusions: In women with early-stage BC undergoing AC, 12-months of ExT did not attenuate functional disability but provided large and clinically meaningful benefits on VO2peak and cardiac reserve. Clinical Trial Registration: URL: https://www.anzctr.org.au/ Unique Identifier: ACTRN12617001408370