Apoptotic mechanisms of gastric cancer cells induced by isolated Erinacine S through epigenetic histone H3 methylation of FasL and TRAIL

Erinacine S, the new bioactive diterpenoid compound isolated from the ethanol extract of the mycelia of Hericium erinaceus, displays great health-promoting properties. However, the effects of erinacine S on inductive...

KMT2A/C mutations function as a potential predictive biomarker for immunotherapy in solid tumors

Epigenetic factors play important roles in tumor immunology. Histone-lysine N-methyltransferase 2 (KMT2) family genes exert histone H3 methylation, but its role in immunotherapy remains unclear. Our study is the first to investigate the correlation between KMT2 gene mutations and the clinical benefit of immune checkpoint inhibitors (ICI) treatment. We firstly collected a primary ICI-treated cohort (n = 546) and found that patients with KMT2A/C mutations yielded better prognosis in terms of progression-free survival (PFS, Hazard ratio [HR] = 0.66, P = 0.002), objective response rate (ORR, 40.9% vs 20.3%, P < 0.001), durable clinical benefit (DCB, 48.3% vs 29.8%, P = 0.001) and overall survival (OS, HR = 0.70, P = 0.033). Furthermore, we validated the predictive potential of KMT2A/C mutations in an expanded ICI-treated cohort (n = 1395). KMT2A/C-mutant patients achieved better OS compared with KMT2A/C-wildtype patients (HR = 0.68, P = 0.003); and the survival advantages appeared in the majority of cancer subtypes. Our study suggests that KMT2A/C mutations function as a novel and potential predictive biomarker for ICI treatment in multiple solid tumors and the underlying mechanism is worth investigating.

Estrogen Induces Selective Transcription of Caveolin1 Variants in Human Breast Cancer through Estrogen Responsive Element-Dependent Mechanisms

The estrogen receptor (ER) signaling regulates numerous physiological processes mainly through activation of gene transcription (genomic pathways). Caveolin1 (CAV1) is a membrane-resident protein that behaves as platform to enable different signaling molecules and receptors for membrane-initiated pathways. CAV1 directly interacts with ERs and allows their localization on membrane with consequent activation of ER-non-genomic pathways. Loss of CAV1 function is a common feature of different types of cancers, including breast cancer. Two protein isoforms, CAV1α and CAV1β, derived from two alternative translation initiation sites, are commonly described for this gene. However, the exact transcriptional regulation underlying CAV1 expression pattern is poorly elucidated. In this study, we dissect the molecular mechanism involved in selective expression of CAV1β isoform, induced by estrogens and downregulated in breast cancer. Luciferase assays and Chromatin immunoprecipitation demonstrate that transcriptional activation is triggered by estrogen-responsive elements embedded in CAV1 intragenic regions and DNA-binding of estrogen-ER complexes. This regulatory control is dynamically established by local chromatin changes, as proved by the occurrence of histone H3 methylation/demethylation events and association of modifier proteins as well as modification of H3 acetylation status. Thus, we demonstrate for the first time, an estrogen-ERs-dependent regulatory circuit sustaining selective CAV1β expression.

MNGI-07. TRIMETHYLATED H3K27 AND EZH2 EXPRESSION IN MENINGIOMA: CORRELATION WITH TENDENCY TO RECUR

Meningiomas are the most frequent primary CNS tumors, usually benign (WHO grade I), but in the 25–30% more aggressive tumors (grade II-III). Histopathological criteria (WHO 2016) are unsatisfactory to recognize meningiomas with tendency to recur. Recent studies have identified some mutations associated with histological features and location (i.e. BAP1 mutation in rhabdoid subtype), while risk stratification schemes based on DNA methylation subgroups have been proposed. Epigenetic modifications of histones play a pivotal role in tumorigenesis, the methylation of lysine 27 (K27) of histone H3 controlled by EZH2 subunit of PRC2 complex. BAP1 could be also involved in epigenetic regulation of PRC2 complex. The deregulation of H3K27 methylation has been found associated with recurrence risk in grade II meningiomas. Aim of the present study was to evaluate histone H3 methylation profile in a group of meningiomas of different grade with follow-up longer than 10 years, comparing non-recurrent to recurrent ones. We performed an immunohistochemical study on 145 meningiomas (50 grade I, 80 grade II and 15 grade III), investigating the expression of trimethylated H3K27 (H3K27me3), EZH2 and BAP1. The results were related to clinical data obtained from our Institutional Tumor Registry and evaluation of clinical reports. We observed a loss of H3K27me3 expression only in grade II and III meningiomas in 18% of cases, without correlation with tendency to recur. EZH2 showed increased percentage of positive nuclei related to the grade. In the group of grade I meningioma EZH2 expression was associated to recurrences. We didn’t observe loss of BAP1 expression. In conclusion, our data suggest that immunohistochemical evaluation of H3K27me3 and EZH2 could be a useful tool to better stratify meningioma with high risk of recurrence. Moreover, EZH2 could be of interest as therapeutic target. Molecular investigations in a larger cohort are needed to confirm these results.

Structural basis of recognition and destabilization of histone H2B ubiquitinated nucleosome by DOT1L histone H3 Lys79 methyltransferase

DOT1L is a histone H3 Lys79 methyltransferase whose activity is stimulated by histone H2B Lys120 ubiquitination, suggesting cross-talk between histone H3 methylation and H2B-ubiquitination. Here, we present cryo-EM structures of DOT1L complex with unmodified and H2B-ubiquitinated nucleosomes, showing that DOT1L recognizes H2B-ubiquitin and the H2A/H2B acidic patch through a C-terminal hydrophobic helix and an arginine anchor in DOT1L respectively. Furthermore, the structures combined with single-molecule FRET experiment show that H2B-ubiquitination enhances a non-catalytic function of DOT1L destabilizing nucleosome. These results establish the molecular basis of the cross-talk between H2B ubiquitination and H3 Lys79 methylation as well as nucleosome destabilization by DOT1L.