EPOP Functionally Links Elongin and Polycomb in Pluripotent Stem Cells.

The cellular plasticity of pluripotent stem cells is thought to be sustained by genomic regions that display both active and repressive chromatin properties. These regions exhibit low levels of gene expression, yet the mechanisms controlling these levels remain unknown. Here, we describe Elongin BC as a binding factor at the promoters of bivalent sites. Biochemical and genome-wide analyses show that Elongin BC is associated with Polycomb Repressive Complex 2 (PRC2) in pluripotent stem cells. Elongin BC is recruited to chromatin by the PRC2-associated factor EPOP (Elongin BC and Polycomb Repressive Complex 2 Associated Protein, also termed C17orf96, esPRC2p48, E130012A19Rik), a protein expressed in the inner cell mass of the mouse blastocyst. Both EPOP and Elongin BC are required to maintain low levels of expression at PRC2 genomic targets. Our results indicate that keeping the balance between activating and repressive cues is a more general feature of chromatin in pluripotent stem cells than previously appreciated.

FUS stimulates microRNA biogenesis by facilitating co-transcriptional Drosha recruitment.

microRNA abundance has been shown to depend on the amount of the microprocessor components or, in some cases, on specific auxiliary co-factors. In this paper, we show that the FUS/TLS (fused in sarcoma/translocated in liposarcoma) protein, associated with familial forms of Amyotrophic Lateral Sclerosis (ALS), contributes to the biogenesis of a specific subset of microRNAs. Among them, species with roles in neuronal function, differentiation and synaptogenesis were identified. We also show that FUS/TLS is recruited to chromatin at sites of their transcription and binds the corresponding pri-microRNAs. Moreover, FUS/TLS depletion leads to decreased Drosha level at the same chromatin loci. Limited FUS/TLS depletion leads to a reduced microRNA biogenesis and we suggest a possible link between FUS mutations affecting nuclear/cytoplasmic partitioning of the protein and altered neuronal microRNA biogenesis in ALS pathogenesis.

Identification of linc-NeD125, a novel long non coding RNA that hosts miR-125b-1 and negatively controls proliferation of human neuroblastoma cells.

The human genome contains some thousands of long non coding RNAs (lncRNAs). Many of these transcripts are presently considered crucial regulators of gene expression and functionally implicated in developmental processes in Eukaryotes. Notably, despite a huge number of lncRNAs are expressed in the Central Nervous System (CNS), only a few of them have been characterized in terms of molecular structure, gene expression regulation and function. In the present study, we identify linc-NeD125 as a novel cytoplasmic, neuronal-induced long intergenic non coding RNA (lincRNA). Linc-NeD125 represents the host gene for miR-125b-1, a microRNA with an established role as negative regulator of human neuroblastoma cell proliferation. Here, we demonstrate that these two overlapping non coding RNAs are coordinately induced during in vitro neuronal differentiation, and that their expression is regulated by different mechanisms. While the production of miR-125b-1 relies on transcriptional regulation, linc-NeD125 is controlled at the post-transcriptional level, through modulation of its stability. We also demonstrate that linc-NeD125 functions independently of the hosted microRNA, by reducing cell proliferation and activating the antiapoptotic factor BCL-2.

Mir-23a and mir-125b regulate neural stem/progenitor cell proliferation by targeting Musashi1.

Musashi1 is an RNA binding protein that controls the neural cell fate, being involved in maintaining neural progenitors in their proliferative state. In particular, its downregulation is needed for triggering early neural differentiation programs. In this study, we profiled microRNA expression during the transition from neural progenitors to differentiated astrocytes and underscored 2 upregulated microRNAs, miR-23a and miR-125b, that sinergically act to restrain Musashi1 expression, thus creating a regulatory module controlling neural progenitor proliferation.

Catalase-Powered Nanobots for Overcoming the Mucus Barrier.

Biological barriers present a significant obstacle to treatment, especially when drugs are administered locally to increase their concentrations at the target site while minimizing unintended off-target effects. Among these barriers, mucus presents a challenge, as it serves as a protective layer in the respiratory, urogenital, and gastrointestinal tracts. Its role is to shield the underlying epithelial cells from pathogens and toxic compounds but also impedes the efficient delivery of drugs. Despite the exploration of mucolytic agents to improve drug delivery, overcoming this protective barrier remains a significant hurdle. In our study, we investigate an alternative approach involving the use of catalase-powered nanobots. We use an in vitro model that simulates intestinal mucus secretion to demonstrate the dual functionality of our nanobots. This includes their ability to disrupt mucus, which we confirmed through in vitro and ex vivo validation, as well as their self-propulsion to overcome the mucus barrier, resulting in a 60-fold increase compared with passive nanoparticles. Therefore, our findings highlight the potential utility of catalase-powered nanobots as carriers for therapeutic agents since they could enhance drug delivery efficiency by penetrating the mucus barrier.

Urease-powered nanobots for radionuclide bladder cancer therapy.

Bladder cancer treatment via intravesical drug administration achieves reasonable survival rates but suffers from low therapeutic efficacy. To address the latter, self-propelled nanoparticles or nanobots have been proposed, taking advantage of their enhanced diffusion and mixing capabilities in urine when compared with conventional drugs or passive nanoparticles. However, the translational capabilities of nanobots in treating bladder cancer are underexplored. Here, we tested radiolabelled mesoporous silica-based urease-powered nanobots in an orthotopic mouse model of bladder cancer. In vivo and ex vivo results demonstrated enhanced nanobot accumulation at the tumour site, with an eightfold increase revealed by positron emission tomography in vivo. Label-free optical contrast based on polarization-dependent scattered light-sheet microscopy of cleared bladders confirmed tumour penetration by nanobots ex vivo. Treating tumour-bearing mice with intravesically administered radio-iodinated nanobots for radionuclide therapy resulted in a tumour size reduction of about 90%, positioning nanobots as efficient delivery nanosystems for bladder cancer therapy.

Complex CDKL5 translational regulation and its potential role in CDKL5 deficiency disorder.

CDKL5 is a kinase with relevant functions in correct neuronal development and in the shaping of synapses. A decrease in its expression or activity leads to a severe neurodevelopmental condition known as CDKL5 deficiency disorder (CDD). CDD arises from CDKL5 mutations that lie in the coding region of the gene. However, the identification of a SNP in the CDKL5 5'UTR in a patient with symptoms consistent with CDD, together with the complexity of the CDKL5 transcript leader, points toward a relevant translational regulation of CDKL5 expression with important consequences in physiological processes as well as in the pathogenesis of CDD. We performed a bioinformatics and molecular analysis of the 5'UTR of CDKL5 to identify translational regulatory features. We propose an important role for structural cis-acting elements, with the involvement of the eukaryotic translational initiation factor eIF4B. By evaluating both cap-dependent and cap-independent translation initiation, we suggest the presence of an IRES supporting the translation of CDKL5 mRNA and propose a pathogenic effect of the C>T -189 SNP in decreasing the translation of the downstream protein.

LINE-1 regulates cortical development by acting as long non-coding RNAs.

Long Interspersed Nuclear Elements-1s (L1s) are transposable elements that constitute most of the genome's transcriptional output yet have still largely unknown functions. Here we show that L1s are required for proper mouse brain corticogenesis operating as regulatory long non-coding RNAs. They contribute to the regulation of the balance between neuronal progenitors and differentiation, the migration of post-mitotic neurons and the proportions of different cell types. In cortical cultured neurons, L1 RNAs are mainly associated to chromatin and interact with the Polycomb Repressive Complex 2 (PRC2) protein subunits enhancer of Zeste homolog 2 (Ezh2) and suppressor of zeste 12 (Suz12). L1 RNA silencing influences PRC2's ability to bind a portion of its targets and the deposition of tri-methylated histone H3 (H3K27me3) marks. Our results position L1 RNAs as crucial signalling hubs for genome-wide chromatin remodelling, enabling the fine-tuning of gene expression during brain development and evolution.

Adjuvant PEFG (cisplatin, epirubicin, 5-fluorouracil, gemcitabine) or gemcitabine followed by chemoradiation in pancreatic cancer: a randomized phase II trial.

BACKGROUND: Information from randomized trials on the role of combination chemotherapy in the adjuvant treatment of pancreatic adenocarcinoma is limited. This randomized phase II trial aimed to identify the most promising regimen warranting phase III evaluation. METHODS: Therapy-naive patients, age 18-75 years, Karnofsky Performance Status (KPS)>60, gross total resection of stage IB-III pancreatic adenocarcinoma, stratified for center and surgical margins, were randomly assigned to receive either gemcitabine 1 g/m2 weekly on days 1, 8, and 15 (arm A) or the PEFG regimen (cisplatin and epirubicin 40 mg/m2, day 1; gemcitabine 600 mg/m2, days 1, 8; 5-fluorouracil 200 mg/m2 daily, days 1-28) (arm B). Chemotherapy was administered every 4 weeks for 3 months and followed by irradiation concurrent to continuous infusion of 5-fluorouracil 250 mg/m2 daily. Primary endpoint was the probability of being disease-free at 1 year from surgery. Assuming P0=35% and P1=55%, α=.05 and ß=.10, the study was to enroll 51 patients per arm. RESULTS: A total of 102 patients were randomized; 100 were eligible (arm A: 51; arm B: 49). Baseline characteristic (A/B) were: Median age was 61/60 years; 75% had KPS>80 75/76%; 36% grade 3 tumor 29/43%, 79% stage IIB/III 75/84%, 31% R1 resection 35/29%. Survival figures (A/B) were: Median disease-free survival was 11.7 and 15.2 months; 1-year disease-free survival 49.0% (95% confidence interval [95% CI] 35-63%) and 69.4% (95% CI 56-83%); median survival 24.8 and 28.9 months. Combination chemotherapy produced more hematological toxicity without relevant differences in nonhematological toxicities. CONCLUSIONS: The 4-drug regimen deserves further assessment in resectable pancreatic cancer.

A prognostic score to predict major complications after pancreaticoduodenectomy.

OBJECTIVE: To develop and validate a simple prognostic score to predict major postoperative complications after pancreaticoduodenectomy (PD). BACKGROUND: PD still carries a high rate of severe postoperative complications. No specific score is currently available to stratify the patient's risk of major morbidity. METHODS: Between 2002 and 2010, preoperative, intraoperative, and outcome data from 700 consecutive patients undergoing PD in our institution were prospectively collected in an electronic database. Major complications were defined as levels III to V of Clavien-Dindo classification. On the basis of a multivariate regression model, the score was developed using a random two-thirds of the population (n = 469) and was validated on the remaining 231 patients. RESULTS: Major complication rate was 16.7% (117/700). Significant predictors included in the scoring system were: pancreas texture, pancreatic duct diameter, operative blood loss, and ASA score. The mean risk of developing major postoperative complications was 7% in patients with score 0 to 3, 13% in patients with score 4 to 7, 23% in patients with score 8 to 11, and 36% in patients with score 12 to 15. In the validation population, the predicted risk of major complications was 15.2% versus a 16.9% observed risk (C-statistic index = 0.743). CONCLUSION: This new score may accurately predict a patient's postoperative outcome. Early identification of high-risk patients could help the surgeon to adopt intraoperative and postoperative strategies tailored on individual basis.

Epigenomic profiling of primate lymphoblastoid cell lines reveals the evolutionary patterns of epigenetic activities in gene regulatory architectures.

Changes in the epigenetic regulation of gene expression have a central role in evolution. Here, we extensively profiled a panel of human, chimpanzee, gorilla, orangutan, and macaque lymphoblastoid cell lines (LCLs), using ChIP-seq for five histone marks, ATAC-seq and RNA-seq, further complemented with whole genome sequencing (WGS) and whole genome bisulfite sequencing (WGBS). We annotated regulatory elements (RE) and integrated chromatin contact maps to define gene regulatory architectures, creating the largest catalog of RE in primates to date. We report that epigenetic conservation and its correlation with sequence conservation in primates depends on the activity state of the regulatory element. Our gene regulatory architectures reveal the coordination of different types of components and highlight the role of promoters and intragenic enhancers (gE) in the regulation of gene expression. We observe that most regulatory changes occur in weakly active gE. Remarkably, novel human-specific gE with weak activities are enriched in human-specific nucleotide changes. These elements appear in genes with signals of positive selection and human acceleration, tissue-specific expression, and particular functional enrichments, suggesting that the regulatory evolution of these genes may have contributed to human adaptation.

Clinicopathological features of pancreatic endocrine tumors: a prospective multicenter study in Italy of 297 sporadic cases.

OBJECTIVES: Information on pancreatic endocrine tumors (PETs) comes mostly from small, retrospective, uncontrolled studies conducted on highly selected patients. The aim of the study was to describe the clinical and pathological features of PETs in a prospective, multicenter study. METHODS: Newly diagnosed, histologically proven, sporadic PETs observed from June 2004 to March 2007 in 24 Italian centers were included in a specific data set. RESULTS: Two hundred ninety-seven patients (mean age 58.6+/-14.7 years, females 51.2%, males 48.8%) were analyzed. In 73 cases (24.6%), the tumor was functioning (F) (53 insulinomas, 15 gastrinomas, 5 other syndromes) and in 232 (75.4%) it was non-functioning (NF); in 115 cases (38.7%), the diagnosis was incidental. The median tumor size was 20 mm (range 2-150). NF-PETs were significantly more represented among carcinomas (P<0.001). Nodal and liver metastases were detected in 84 (28.3%) and 85 (28.6%) cases, respectively. The presence of liver metastases was significantly higher in the NF-PETs than in the F-PETs (32.1% vs. 17.8%; P<0.05), and in the symptomatic than in the asymptomatic patients (34.6% vs. 19.1%; P<0.005). At the time of recruitment, the majority of patients (251, 84.5%) had undergone surgery, with complete resection in 209 cases (83.3%). CONCLUSIONS: This study points out the high number of new cases of PETs observed in Italy, with a high prevalence of NF and incidentally discovered forms. The size of the tumor was smaller and the rate of metastasis was lower than usually reported, suggesting a trend toward an earlier diagnosis.

Parenchyma-preserving resections for small nonfunctioning pancreatic endocrine tumors.

BACKGROUND: Parenchyma-preserving resections (PPRs), including enucleation and middle pancreatectomy (MP), are accepted procedures for insulinomas, but their role in the treatment of nonfunctioning pancreatic endocrine tumors (NF-PETs) is debated. The aim of this study was to evaluate perioperative and long-term outcomes after PPRs for NF-PETs. METHODS: All patients who underwent PPRs for NF-PETs between 1990 and 2005 were included. Patients with multiple endocrine neoplasia type 1 were excluded. RESULTS: Overall, 50 patients (23 men, 27 women, median age 59 years) underwent 26 enucleations and 24 MP. A total of 58% of NF-PETs were incidentally discovered. Median size of the tumors was 13.5 mm with no preoperative suspicion of malignancy in all patients. Overall morbidity and pancreatic fistula rates were 58 and 50%, respectively. Reoperation rate was 4%, with no mortality. Postoperative complications were higher in the MP group. At pathology, there were 34 (68%) benign lesions, 13 (26%) neoplasms of uncertain behavior, and 3 (6%) well-differentiated carcinomas. Forty-one patients (82%) had tumors < or =2 cm in size. Only eight patients (16%) had at least one lymph node removed. After a median follow-up of 58 months, no patient died of disease. Overall, four patients (8%) experienced tumor recurrence after a mean of 68 months. The incidence of exocrine/endocrine insufficiency was 8%. CONCLUSIONS: PPRs are generally safe and effective procedures for treating small NF-PETs. However, better selection criteria must be identified, and lymph node sampling should be performed routinely to avoid understaging. Long-term follow-up evaluation (>5 years) is of paramount importance given the possible risk of late recurrence.

Carcinoembryonic antigen-specific but not antiviral CD4+ T cell immunity is impaired in pancreatic carcinoma patients.

Pancreatic carcinoma is a very aggressive disease with dismal prognosis. Although evidences for tumor-specific T cell immunity exist, factors related to tumor microenvironment and the presence of immunosuppressive cytokines in patients' sera have been related to its aggressive behavior. Carcinoembryonic Ag (CEA) is overexpressed in 80-90% of pancreatic carcinomas and contains epitopes recognized by CD4(+) T cells. The aim of this study was to evaluate the extent of cancer-immune surveillance and immune suppression in pancreatic carcinoma patients by comparing the anti-CEA and antiviral CD4(+) T cell immunity. CD4(+) T cells from 23 normal donors and 44 patients undergoing surgical resection were tested for recognition of peptides corresponding to CEA and viral naturally processed promiscuous epitopes by proliferation and cytokine release assays. Anti-CEA CD4(+) T cell immunity was present in a significantly higher number of normal donors than pancreatic cancer patients. Importantly, whereas CD4(+) T cells from normal donors produced mainly GM-CSF and IFN-gamma, CD4(+) T cells from the patients produced mainly IL-5, demonstrating a skew toward a Th2 type. On the contrary, the extent of antiviral CD4(+) T cell immunity was comparable between the two groups and showed a Th1 type. The immunohistochemical analysis of tumor-infiltrating lymphocytes showed a significantly higher number of GATA-3(+) compared with T-bet(+) lymphoid cells, supporting a Th2 skew also at the tumor site. Collectively, these results demonstrate that Th2-immune deviation in pancreatic cancer is not generalized but tumor related and suggests that the skew might be possibly due to factor(s) present at the tumor site.

Surgical management of acute pancreatitis in Italy: lessons from a prospective multicentre study.

OBJECTIVE: This study aimed to evaluate the surgical treatment of acute pancreatitis in Italy and to assess compliance with international guidelines. METHODS: A series of 1173 patients in 56 hospitals were prospectively enrolled and their data analysed. RESULTS: Twenty-nine patients with severe pancreatitis underwent surgical intervention. Necrosectomy was performed in 26 patients, associated with postoperative lavage in 70% of cases. A feeding jejunostomy was added in 37% of cases. Mortality was 21%. Of the patients with mild pancreatitis, 714 patients with a biliary aetiology were evaluated. Prophylactic treatment of relapses was carried out in 212 patients (36%) by cholecystectomy and in 161 using a laparoscopic approach. Preoperative endoscopic retrograde cholangiopancreatography was associated with cholecystectomy in 83 patients (39%). Forty-seven patients (22%) were treated at a second admission, with a median delay of 31 days from the onset of pancreatitis. Eighteen patients with severe pancreatitis underwent cholecystectomy 37.9 days after the first admission. There were no deaths. DISCUSSION: The results indicate poor compliance with published guidelines. In severe pancreatitis, early surgical intervention is frequently performed and enteral feeding is seldom used. Only a small number of patients with mild biliary pancreatitis undergo definitive treatment (i.e. cholecystectomy) within 4 weeks of the onset of pancreatitis.

MECP2 mutations affect ciliogenesis: a novel perspective for Rett syndrome and related disorders.

Mutations in MECP2 cause several neurological disorders of which Rett syndrome (RTT) represents the best-defined condition. Although mainly working as a transcriptional repressor, MeCP2 is a multifunctional protein revealing several activities, the involvement of which in RTT remains obscure. Besides being mainly localized in the nucleus, MeCP2 associates with the centrosome, an organelle from which primary cilia originate. Primary cilia function as "sensory antennae" protruding from most cells, and a link between primary cilia and mental illness has recently been reported. We herein demonstrate that MeCP2 deficiency affects ciliogenesis in cultured cells, including neurons and RTT fibroblasts, and in the mouse brain. Consequently, the cilium-related Sonic Hedgehog pathway, which is essential for brain development and functioning, is impaired. Microtubule instability participates in these phenotypes that can be rescued by HDAC6 inhibition together with the recovery of RTT-related neuronal defects. Our data indicate defects of primary cilium as a novel pathogenic mechanism that by contributing to the clinical features of RTT might impact on proper cerebellum/brain development and functioning, thus providing a novel therapeutic target.

Trans-generational epigenetic regulation associated with the amelioration of Duchenne Muscular Dystrophy.

Exon skipping is an effective strategy for the treatment of many Duchenne Muscular Dystrophy (DMD) mutations. Natural exon skipping observed in several DMD cases can help in identifying novel therapeutic tools. Here, we show a DMD study case where the lack of a splicing factor (Celf2a), which results in exon skipping and dystrophin rescue, is due to a maternally inherited trans-generational epigenetic silencing. We found that the study case and his mother express a repressive long non-coding RNA, DUXAP8, whose presence correlates with silencing of the Celf2a coding region. We also demonstrate that DUXAP8 expression is lost upon cell reprogramming and that, upon induction of iPSCs into myoblasts, Celf2a expression is recovered leading to the loss of exon skipping and loss of dystrophin synthesis. Finally, CRISPR/Cas9 inactivation of the splicing factor Celf2a was proven to ameliorate the pathological state in other DMD backgrounds establishing Celf2a ablation or inactivation as a novel therapeutic approach for the treatment of Duchenne Muscular Dystrophy.

Intra-operative radiotherapy (IORT) in pancreatic cancer: joint analysis of the ISIORT-Europe experience.

PURPOSE: A joint analysis of data from five contributing centers within the ISIORT-Europe program was performed to investigate the main contributions of intra-operative radiotherapy (IORT) to the multidisciplinary treatment of pancreatic cancer. MATERIALS AND METHODS: Patients with a histologic diagnosis of carcinoma of the pancreas, with an absence of distant metastases, undergoing surgery with radical intent and IORT were considered eligible for participation in this study. RESULTS: From 1985 to 2006, a total of 270 patients were enrolled in the study from five European institutions. Surgery was performed in 91.5% of cases and complicated by adverse events in 59 cases. External radiotherapy (ERT) preceded surgery in 23.9% of cases. One-hundred and six patients received further ERT. After surgery + IORT, median follow-up was 96 months (range 3-180). Median local control was 15 months, 5-year local control was 23.3%. Median overall survival was 19 months, while 5-year survival was 17.7%. A significantly greater local control and survival were observed in patients undergoing preoperative radiotherapy (LC: median not reached; OS: median 30 months) compared to patients treated with postoperative ERT alone (LC: median 28 months; OS: median 22 months), and to patients submitted to IORT exclusively (LC: median 8 months; OS: median 13 months) (p < 0.0001). CONCLUSION: From this joint analysis emerges the fact that preoperative radiotherapy increases the effects of IORT in terms of local control and overall survival. The 5-year local control of 23.3% confirms the beneficial "sterilizing" effect of IORT on the tumor bed.

[Diverticular disease of the colon: diagnosis and treatment. Consensus Conference, 5th National Congress of the Italian Society of Academic Surgeons]. / La malattia diverticolare del colon: quando e come trattarla. Consensus Conference- del quinto Congresso Nazionale della Società Italiana dei Chirurghi Universitari (S.I.C.U.).

Diverticular disease (DD) is one of the most common disorders of the colon with an increased prevalence in Western populations. There are still many unsolved issues about indications, timing of surgery and modality of surgical treatment. These topics were discussed during the Consensus Conference (CC). There is still common agreement indicating surgery after the second acute episode of diverticular disease; however, patients younger than 50 years should undergo surgery after the first acute episode, because of a higher risk of recurrence compared to older patients. It is not clear though how to uniformly classify an acute episode (severe, moderate or mild): an accurate clinical and instrumental valuation (based on CT scan) is recommended to establish the real severity of the acute episode before recommending a surgical procedure. In presence of septic complications (abscess or peritonitis) of DD, colonic resection is indicated, but a primary anastomosis could be at risk of failure due to sepsis. Therefore a Hartmann's procedure or protective stoma could be preferable. However, instead of a staged procedure, an appropriate strategy should be to resolve sepsis and perform resection and anastomosis in election. Abscesses smaller than 5 cm intra-meso-colic or para-colic can be successfully treated medically; vice versa larger or pelvic abscesses should undergo percutaneous or laparoscopic drainage, postponing colonic resection in elective conditions. Limited purulent peritonitis can be favourably treated by means of laparoscopic approach and simple lavage and drainage of peritoneal cavity. Diffuse purulent or faecal peritonitis is the most dramatic complication which still has a high risk of mortality and morbidity. Surgical risk is related to clinical conditions, duration of peritonitis, age of patient and comorbidities. Thus it is not possible to state a univocal approach, although Hartmann's procedure keeps being the first choice. On this matter farther randomized studies are required to compare Hartmann's procedure with other techniques (such as primary anastomosis with or without diverting colostomy). A wide left colonic resection (with splenic flexure mobilization) extended beneath sigmoid-rectal junction is recommended to avoid immediate or late complications. Laparoscopic approach is feasible, even for management of complicated diverticular disease, if strict patient selection criteria are followed, duration of the procedure is comparable to open surgery and conversion rate is under 10%.

Polycomb complexes in normal and malignant hematopoiesis.

Epigenetic mechanisms are crucial for sustaining cell type-specific transcription programs. Among the distinct factors, Polycomb group (PcG) proteins are major negative regulators of gene expression in mammals. These proteins play key roles in regulating the proliferation, self-renewal, and differentiation of stem cells. During hematopoietic differentiation, many PcG proteins are fundamental for proper lineage commitment, as highlighted by the fact that a lack of distinct PcG proteins results in embryonic lethality accompanied by differentiation biases. Correspondingly, proteins of these complexes are frequently dysregulated in hematological diseases. In this review, we present an overview of the role of PcG proteins in normal and malignant hematopoiesis, focusing on the compositional complexity of PcG complexes, and we briefly discuss the ongoing clinical trials for drugs targeting these factors.