The histone methyltransferase Setd8 acts in concert with c-Myc and is required to maintain skin

Keratinocyte-specific ablation of the histone H4K20 methyltransferase Setd8 reveals its essential role in embryonic and postnatal skin homeostasis. Molecularly, the c-myc target gene Setd8 regulates proliferation/differentiation by controlling p63 function

PR-Set7 and H4K20me1: at the crossroads of genome integrity, cell cycle, chromosome condensation, and transcription.

Histone post-translational modifications impact many aspects of chromatin and nuclear function. Histone H4 Lys 20 methylation (H4K20me) has been implicated in regulating diverse processes ranging from the DNA damage response, mitotic condensation, and DNA replication to gene regulation. PR-Set7/Set8/KMT5a is the sole enzyme that catalyzes monomethylation of H4K20 (H4K20me1). It is required for maintenance of all levels of H4K20me, and, importantly, loss of PR-Set7 is catastrophic for the earliest stages of mouse embryonic development. These findings have placed PR-Set7, H4K20me, and proteins that recognize this modification as central nodes of many important pathways. In this review, we discuss the mechanisms required for regulation of PR-Set7 and H4K20me1 levels and attempt to unravel the many functions attributed to these proteins

Spontaneous development of hepatocellular carcinoma with cancer stem cell properties in PR‐SET7‐deficient livers

PR-SET7-mediated histone 4 lysine 20 methylation has been implicated in mitotic condensation, DNA damage response and replication licensing. Here, we show that PR-SET7 function in the liver is pivotal for maintaining genome integrity. Hepatocyte-specific deletion of PR-SET7 in mouse embryos resulted in G2 phase arrest followed by massive cell death and defect in liver organogenesis. Inactivation at postnatal stages caused cell duplication-dependent hepatocyte necrosis, accompanied by inflammation, fibrosis and compensatory growth induction of neighboring hepatocytes and resident ductal progenitor cells. Prolonged necrotic regenerative cycles coupled with oncogenic STAT3 activation led to the spontaneous development of hepatic tumors composed of cells with cancer stem cell characteristics. These include a capacity to self-renew in culture or in xenografts and the ability to differentiate to phenotypically distinct hepatic cells. Hepatocellular carcinoma in PR-SET7-deficient mice displays a cancer stem cell gene signature specified by the co-expression of ductal progenitor markers and oncofetal genes

SET7/9 Enzyme Regulates Cytokine-induced Expression of Inducible Nitric-oxide Synthase through Methylation of Lysine 4 at Histone 3 in the Islet β Cell

SET7/9 is an enzyme that methylates histone 3 at lysine 4 (H3K4) to maintain euchromatin architecture. Although SET7/9 is enriched in islets and contributes to the transactivation of β cell-specific genes, including Ins1 and Slc2a, SET7/9 has also been reported to bind the p65 subunit of nuclear factor κB in non-β cells and modify its transcriptional activity. Given that inflammation is a central component of β cell dysfunction in Type 1 and Type 2 diabetes, the aim of this study was to elucidate the role of SET7/9 in proinflammatory cytokine signaling in β cells. To induce inflammation, βTC3 insulinoma cells were treated with IL-1β, TNF-α, and IFN-γ. Cytokine treatment led to increased expression of inducible nitric-oxide synthase, which was attenuated by the diminution of SET7/9 using RNA interference. Consistent with previous reports, SET7/9 was co-immunoprecipitated with p65 and underwent cytosolic to nuclear translocation in response to cytokines. ChIP analysis demonstrated augmented H3K4 mono- and dimethylation of the proximal Nos2 promoter with cytokine exposure. SET7/9 was found to occupy this same region, whereas SET7/9 knockdown attenuated cytokine-induced histone methylation of the Nos2 gene. To test this relationship further, islets were isolated from SET7/9-deficient and wild-type mice and treated with IL-1β, TNF-α, and IFN-γ. Cytokine-induced Nos2 expression was reduced in the islets from SET7/9 knock-out mice. Together, our findings suggest that SET7/9 contributes to Nos2 transcription and proinflammatory cytokine signaling in the pancreatic β cell through activating histone modifications

Phase I study of the safety and tolerability of LJM716 in Japanese patients with advanced solid tumors

Background: Human epidermal growth factor receptor 3 (HER3) is implicated in tumor growth, proliferation, drug resistance, and metastasis. LJM716 is a fully humanized anti-HER3 IgG1 monoclonal antibody with single-agent and combination anti-tumor activity in HER2-amplified and neuregulin-expressing xenografts. This open-label dose escalation Phase I study evaluated the safety and tolerability of single-agent LJM716 in Japanese patients (pts) with HER2+ advanced/metastatic breast (BC) or gastric cancer (GC), and recurrent/metastatic esophageal squamous cell carcinoma (ESCC) or squamous cell carcinoma of the head and neck (SCCHN) regardless of HER2 status. Methods: Pts (aged ≥18 years, ECOG PS 0-2) received intravenous (IV) once-weekly (QW) LJM716 in 28 day cycles. The primary objective was to determine the maximum tolerated dose (MTD) and/or recommended dose (RD). Secondary objectives included safety and tolerability, preliminary anti-tumor activity, and pharmacokinetics. Dose escalation decisions were made based on a synthesis of all relevant data, guided by an adaptive Bayesian logistic regression model (BLRM) on dose limiting toxicities (DLTs). Results: At the data cutoff date of Jun 3, 2015, 12 pts (SCCHN [n = 2], ESCC [n = 2], and HER2+ BC [n = 6] or GC [n = 2]) were enrolled (median age 58 years, 50% male, 58% ECOG PS 0). Pts were treated in 3 dose cohorts of 10-40 mg/kg QW; the median duration of exposure to LJM716 was 14.0 weeks (range 4.0-48.1). No DLT was reported during Cycle 1; at 40 mg/kg QW 1 pt experienced a DLT of Grade (Gr) 3 pneumonia aspiration during Cycle 2. The BLRM with overdose control supported the tolerability of LJM716 up to 40 mg/kg QW based on DLTs occurring during Cycle 1. However, DLTs occurring after Cycle 1 were also clinically considered, and 40 mg/kg QW was declared as the RD in Japanese pts; the MTD was not reached. One or more adverse event (AE) suspected as drug related were experienced by 10 (83%) pts; most commonly (≥25%) diarrhea (6 pts [50%]), stomatitis, paronychia, fatigue, and pyrexia (3 pts [25%] each). Four pts (33%) experienced ≥1 Gr 3/4 drug-related AEs (all at 40 mg/kg QW): pneumonia aspiration and neutropenia (1 pt [8%] each) and lymphocyte count decreased (2 pts [17%]). Serious AEs were experienced by 2 pts (17%); Gr 2 nausea and Gr 1 vomiting (not suspected as drug related) and Gr 3 pneumonia aspiration (suspected as drug related). One pt died within the follow up period after the last dose of study drug due to disease progression. LJM716 plasma concentration increased with dose, and mean AUClast and Cmax were similar to those found in Western pts. There were no complete or partial responses; stable disease was reported in 6 (50%) pts. Conclusion: LJM716 was well tolerated with a manageable safety profile, and the RD of LJM716 was established at 40 mg/kg QW IV in Japanese pts - the same RD as determined in Western pts in a separate clinical trial. Clinical trials identifier: NCT01911936

Monomethylation of Histone H4-Lysine 20 Is Involved in Chromosome Structure and Stability and Is Essential for Mouse Development▿

PR-Set7/Set8/KMT5A is the sole enzyme known to catalyze monomethylation of histone H4 lysine 20 (H4K20) and is present only in multicellular organisms that compact a large fraction of their DNA. We found that mouse embryos that are homozygous null mutants for the gene PR-Set7 display early embryonic lethality prior to the eight-cell stage. Death was due to the absence of PR-Set7 catalytic activity, since microinjection of the wild type, but not a catalytically inactive version, into two-cell embryos rescued the phenotype. A lack of PR-Set7 activity resulted not only in depletion of H4K20me1 but also in reduced levels of the H4K20me2/3 marks catalyzed by the Suv4-20h1/h2 enzymes, implying that H4K20me1 may be essential for the function of these enzymes to ensure the dimethylated and trimethylated states. Embryonic stem cells that were inducibly deleted for PR-Set7 passed through an initial G2/M phase, but the progeny were defective at the subsequent S and G2/M phases, exhibiting a delay in their cell cycle, accumulation at G2/M, massive DNA damage, and improper mitotic chromosome condensation. Cell cycle analysis after synchronization indicated that the defects were a consequence of decreased H4K20me1 due to the absence of PR-Set7. Most importantly, the lack of H4K20me1 also resulted in defects in chromosome condensation in interphase nuclei. These results demonstrate the critical role of H4K20 monomethylation in mammals in a developmental context

Phase I study of LJM716 in Japanese patients

Purpose: Human epidermal growth factor receptor 3 (HER3) has been identified as an important component of many receptor tyrosine kinase-driven cancers. LJM716 is a human IgG monoclonal antibody that binds HER3, trapping it in an inactive conformation. In this study, a phase I dose escalation was performed with a primary objective to establish the maximum tolerated dose and/or the recommended dose of LJM716 in Japanese patients with selected advanced solid tumors. Secondary objectives included the evaluation of the safety and tolerability, preliminary antitumor activity, and pharmacokinetics of LJM716 in Japanese patients. Methods: LJM716 was administered intravenously at doses of 10, 20, or 40 mg/kg once weekly, in 28-day cycles, to 12 patients with HER2-amplified breast cancer or gastric cancer, or with esophageal squamous cell carcinoma or squamous cell carcinoma of the head and neck, regardless of HER2 status. Results: The maximum tolerated dose was not reached and the recommended dose was established at 40 mg/kg. No dose-limiting toxicities were observed in the first cycle. The most frequently reported adverse events were diarrhea, fatigue, stomatitis, pyrexia, and paronychia. One unconfirmed partial response was observed in a patient with breast cancer and 50 % of the patients achieved stable disease as the best overall response. Exposure increased with ascending dose, and half-life was estimated to be 11–14 days. No anti-LJM716 antibodies were detected. Conclusions: LJM716 was well tolerated in Japanese patients, and a degree of tumor shrinkage was observed. Keywords: HER3; HER2; LJM716; monoclonal antibody; phase I Clinical trial information: ClinicalTrials.gov NCT0191193

Chromatin in the nuclear landscape.

Chromatin affects many, if not all aspects, of nuclear organization and function. For this reason, we have focused our attention on elucidating some of the basic mechanisms regulating the formation and maintenance of chromatin, specifically concerning Polycomb repressive complex 2 (PRC2) and PR-Set7. PRC2 is responsible for catalyzing trimethylation of lysine 27 of histone H3 and thus has a critical role in the formation of facultative heterochromatin. PR-Set7 is responsible for catalyzing monomethylation of lysine 20 of histone H4 and is required for proper cell cycle progression and DNA damage response. We have also expanded our work to establish novel techniques and approaches to determine how chromatin is spatially regulated within the nuclear landscape