IMPORTANCEApproximately 25% of patients with early-stage breast cancer who receive (neo)adjuvant chemotherapy experience a recurrence within 5 years. Improvements in therapy are greatly needed.OBJECTIVE To determine if pembrolizumab plus neoadjuvant chemotherapy (NACT) in early-stage breast cancer is likely to be successful in a 300-patient, confirmatory randomized phase 3 neoadjuvant clinical trial. DESIGN, SETTING, AND PARTICIPANTSThe I-SPY2 study is an ongoing open-label, multicenter, adaptively randomized phase 2 platform trial for high-risk, stage II/III breast cancer, evaluating multiple investigational arms in parallel. Standard NACT serves as the common control arm; investigational agent(s) are added to this backbone. Patients with ERBB2 (formerly HER2)-negative breast cancer were eligible for randomization to pembrolizumab between November 2015 and November 2016.INTERVENTIONS Participants were randomized to receive taxane-and anthracycline-based NACT with or without pembrolizumab, followed by definitive surgery. MAIN OUTCOMES AND MEASURESThe primary end point was pathologic complete response (pCR). Secondary end points were residual cancer burden (RCB) and 3-year event-free and distant recurrence-free survival. Investigational arms graduated when demonstrating an 85% predictive probability of success in a hypothetical confirmatory phase 3 trial. RESULTSOf the 250 women included in the final analysis, 181 were randomized to the standard NACT control group (median [range] age, 47 [24.77] years). Sixty-nine women (median [range] age, 50 [27-71] years) were randomized to 4 cycles of pembrolizumab in combination with weekly paclitaxel followed by AC; 40 hormone receptor (HR)-positive and 29 triple-negative. Pembrolizumab graduated in all 3 biomarker signatures studied. Final estimated pCR rates, evaluated in March 2017, were 44% vs 17%, 30% vs 13%, and 60% vs 22% for pembrolizumab vs control in the ERBB2-negative, HR-positive/ERBB2-negative, and triple-negative cohorts, respectively. Pembrolizumab shifted the RCB distribution to a lower disease burden for each cohort evaluated. Adverse events included immune-related endocrinopathies, notably thyroid abnormalities (13.0%) and adrenal insufficiency (8.7%). Achieving a pCR appeared predictive of long-term outcome, where patients with pCR following pembrolizumab plus chemotherapy had high event-free survival rates (93% at 3 years with 2.8 years' median follow-up).CONCLUSIONS AND RELEVANCE When added to standard neoadjuvant chemotherapy, pembrolizumab more than doubled the estimated pCR rates for both HR-positive/ERBB2negative and triple-negative breast cancer, indicating that checkpoint blockade in women with early-stage, high-risk, ERBB2-negative breast cancer is highly likely to succeed in a phase 3 trial. Pembrolizumab was the first of 10 agents to graduate in the HR-positive/ERBB2-negative signature.

No abstract

The peroxisome proliferator-activated receptor ␥ (PPAR␥) is a central regulator of adipogenesis and recruits coactivator proteins in response to ligand. However, the role of another class of nuclear cofactors, the nuclear receptor corepressors, in modulating PPAR␥ transcriptional activity is less clear. Such corepressors include the nuclear receptor corepressor (NCoR) and the silencing mediator of retinoid and thyroid hormone receptors (SMRT). Our data suggest that PPAR␥ recruits SMRT and NCoR in the absence of ligand and that these corepressors are capable of down-regulating PPAR␥-mediated transcriptional activity. The addition of the PPAR␥ ligand pioglitazone results in dissociation of the PPAR␥-corepressor complex. To define the role of SMRT and NCoR in PPAR␥ action, 3T3-L1 cells deficient in SMRT or NCoR were generated by RNA interference. When these cells are exposed to differentiation media, they exhibit increased expression of adipocyte-specific genes and increased production of lipid droplets, as compared with control cells. These data suggest that the nuclear receptor corepressors decrease PPAR␥ transcriptional activity and repress the adipogenic program in 3T3-L1 cells. The thyroid hormone receptors (TRs)1 and retinoic acid receptors (RARs) are nuclear receptors that repress gene transcription in the absence of their respective ligands. This ligandindependent repression is mediated by nuclear receptor corepressors, such as the nuclear receptor corepressor protein (NCoR) and the silencing mediator of retinoid and thyroid hormone receptors (SMRT) (1, 2). NCoR and SMRT are recruited by TR and RAR isoforms in the absence of ligand and are released upon ligand binding. NCoR and SMRT, in turn, recruit a complex with histone deacetylase activity to repress transcription of target genes. More recently, NCoR and SMRT have been shown to be recruited by other nuclear receptors, some of which bind nuclear receptor corepressors in the presence of antagonists. However, it has been controversial whether NCoR and SMRT play a significant role in gene regulation by the peroxisome proliferator-activated receptor ␥ (PPAR␥) isoforms (3).Two types of PPAR␥ isoforms exist, PPAR␥1 and PPAR␥2. These receptors differ only in their amino-terminal A/B domain, such that PPAR␥2 contains an extra 30 amino acids (4). The function of PPAR␥2 has attracted considerable interest because it is specifically expressed in adipocytes and is an essential regulator of adipogenesis. In addition, many important adipocyte-specific genes contain response elements for PPAR␥ in their promoter regions. Although PPAR␥ clearly recruits coactivators in response to exogenous ligands, its ability to recruit corepressors is less certain. In contrast to the TR, PPAR␥ does not appear to be a strong repressor in the absence of its ligand. Such experiments, however, have been limited by the lack of information concerning physiologic endogenous ligands. Early work into PPAR␥ and corepressor recruitment suggested that PPAR␥ might not recruit NCoR or SMRT in the p...

Congenital hypothyroidism and the thyroid hormone (T3) resistance syndrome are associated with severe central nervous system (CNS) dysfunction. Because thyroid hormones are thought to act principally by binding to their nuclear receptors (TRs), it is unexplained why TR knock-out animals are reported to have normal CNS structure and function. To investigate this discrepancy further, a T3 binding mutation was introduced into the mouse TR-␤ locus by homologous recombination. Because of this T3 binding defect, the mutant TR constitutively interacts with corepressor proteins and mimics the hypothyroid state, regardless of the circulating thyroid hormone concentrations. Severe abnormalities in cerebellar development and function and abnormal hippocampal gene expression and learning were found. These findings demonstrate the specific and deleterious action of unliganded TR in the brain and suggest the importance of corepressors bound to TR in the pathogenesis of hypothyroidism.