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Sporadic Alzheimer’s disease (AD) is the most common cause of dementia. However, representative experimental models of AD have remained difficult to produce because of the disease’s uncertain origin. The Polycomb group protein BMI1 regulates chromatin compaction and gene silencing. BMI1 expression is abundant in adult brain neurons but down-regulated in AD brains. We show here that mice lacking one allele of Bmi1 (Bmi1+/−) develop normally but present with age cognitive deficits and neurodegeneration sharing similarities with AD. Bmi1+/− mice also transgenic for the amyloid beta precursor protein died prematurely and present aggravated disease. Loss of heterochromatin and DNA damage response (DDR) at repetitive DNA sequences were predominant in Bmi1+/− mouse neurons and inhibition of the DDR mitigated the amyloid and Tau phenotype. Heterochromatin anomalies and DDR at repetitive DNA sequences were also found in AD brains. Aging Bmi1+/− mice may thus represent an interesting model to identify and study novel pathogenic mechanisms related to AD.

Late-onset sporadic Alzheimer's disease (AD) is the most prevalent form of dementia, but its origin remains poorly understood. The Bmi1/Ring1 protein complex maintains transcriptional repression of developmental genes through histone H2A mono-ubiquitination, and Bmi1 deficiency in mice results in growth retardation, progeria, and neurodegeneration. Here, we demonstrate that BMI1 is silenced in AD brains, but not in those with early-onset familial AD, frontotemporal dementia, or Lewy body dementia. BMI1 expression was also reduced in cortical neurons from AD patient-derived induced pluripotent stem cells but not in neurons overexpressing mutant APP and PSEN1. BMI1 knockout in human post-mitotic neurons resulted in amyloid beta peptide secretion and deposition, p-Tau accumulation, and neurodegeneration. Mechanistically, BMI1 was required to repress microtubule associated protein tau (MAPT) transcription and prevent GSK3beta and p53 stabilization, which otherwise resulted in neurodegeneration. Restoration of BMI1 activity through genetic or pharmaceutical approaches could represent a therapeutic strategy against AD.

Background Checkpoint blockade with ipilimumab provides long-term survival to a significant proportion of patients with metastatic melanoma. New approaches to increase survival and to predict which patients will benefit from treatment are needed. This phase II trial combined ipilimumab with carboplatin/paclitaxel (CP) to assess its safety, efficacy, and to search for peripheral and tumor-based predictive biomarkers. Methods Thirty patients with untreated unresectable/metastatic melanoma were treated with ipilimumab and CP. Adverse events (AEs) were monitored and response to treatment was evaluated. Tumor tissue and peripheral blood were collected at specified time points to characterize tumor immune markers by immunohistochemistry and systemic immune activity by multiplex assays and flow cytometry. Results Eighty three percent of patients received all 5 cycles of CP and 93% completed ipilimumab induction. Serious AEs occurred in 13% of patients, and no treatment-related deaths were observed. Best Overall Response Rate (BORR) and Disease Control Rate (DCR) were 27 and 57%, respectively. Median overall survival was 16.2 months. Response to treatment was positively correlated with a higher tumor CD3+ infiltrate (immune score) at baseline. NRAS and BRAF mutations were less frequent in patients who experienced clinical benefit. Assessment of peripheral blood revealed that non-responders had elevated baseline levels of CXCL8 and CCL4, and a higher proportion of circulating late differentiated B cells. Pre-existing high levels of chemokines (CCL3, CCL4 and CXCL8) and advanced B cell differentiation were strongly associated with worse patient overall survival. Elevated proportions of circulating CD8+/PD-1+ T cells during treatment were associated with worse survival. Conclusions The combination of ipilimumab and CP was well tolerated and revealed novel characteristics associated with patients likely to benefit from treatment. A pre-existing systemic inflammatory state characterized by elevation of selected chemokines and advanced B cell differentiation, was strongly associated with poor patient outcomes, revealing potential predictive circulating biomarkers. Trial registration Clinicaltrials.gov, NCT01676649, registered on August 29, 2012. Electronic supplementary material The online version of this article (10.1186/s40425-017-0290-x) contains supplementary material, which is available to authorized users.

185 Background: Only a subset of MM patients benefit from treatment with IPI. In an effort to increase response and identify predictive immune biomarkers, we combined IPI with CP. We here report a significant correlation between overall survival (OS) and biomarkers of a pre-existing inflammatory state. Methods: 30 patients were treated with C (AUC = 6) and P (175mg/m2) every 3 weeks x 5 and IPI (3mg/kg) every 3 weeks x 4. Blood was collected throughout. OS Kaplan–Meier curves were compared by the log-rank test. Cutoff thresholds defining high or low levels of chemokines, B cell populations and PD-1+CD8+ T cell populations were established from the mean value of a given variable from all patients. Neutrophil to Lymphocyte Ratio (NLR) and Systemic Immune Inflammation Index defined as Platelet x Neutrophil to Lymphocyte Ratio (SII) were calculated at baseline and tested for association with OS. SII ≥ 1375 and NLR ≥ 5 were considered as high risk groups. Results: Median OS was 16.2 months, with a 3-year OS of 36.7% for all patients. High levels of CCL3 (HR = 2.79, p = 0.0159), CCL4 (HR = 8.36, p < 0.0001) and CXCL8 (HR = 3.52, p = 0.0037) were associated with worse OS. Advanced B cell differentiation before treatment was associated with worse patient outcomes. High levels of early differentiated Bm2 ( > 57%) were strongly associated with better OS: HR = 0.26 p = 0.004 whereas high eBm5+Bm5 ( > 14%) levels were strongly associated with worse OS: HR = 2.65, p = 0.029. Patients with higher proportions of PD-1+CD8+ T cells in circulation during treatment had poorer OS (HR = 3.84, p = 0.004) at week 10; (HR = 3.53, p = 0.005) at week 13 and (HR = 2.84, p = 0.040) at week 24. High risk SII (HR = 3.30, p = 0.0192) and NLR (HR = 2.367, p = 0.0486) were associated with worse OS. Conclusions: We have identified a significant correlation between pre-existing systemic inflammatory state and a poor response to IPI and CP. Specifically elevated CCL3, CCL4 and CXCL8, baseline B lymphocyte subset skewing, increased CD8+PD-1+ T lymphocytes, increased NLR and SII were all strongly associated to worse OS. Comprehensive immune monitoring provides evidence for new circulating biomarkers predicting outcome in MM patients treated with IPI and CP. Clinical trial information: NCT01676649.

The polycomb repressive complex 1 (PRC1), containing the core BMI1 and RING1A/B proteins, mono-ubiquitinylates histone H2A (H2A(ub)) and is associated with silenced developmental genes at facultative heterochromatin. It is, however, assumed that the PRC1 is excluded from constitutive heterochromatin in somatic cells based on work performed on mouse embryonic stem cells and oocytes. We show here that BMI1 is required for constitutive heterochromatin formation and silencing in human and mouse somatic cells. BMI1 was highly enriched at intergenic and pericentric heterochromatin, co-immunoprecipitated with the architectural heterochromatin proteins HP1, DEK1, and ATRx, and was required for their localization. In contrast, BRCA1 localization was BMI1-independent and partially redundant with that of BMI1 for H2A(ub) deposition, constitutive heterochromatin formation, and silencing. These observations suggest a dynamic and developmentally regulated model of PRC1 occupancy at constitutive heterochromatin, and where BMI1 function in somatic cells is to stabilize the repetitive genome.