YY1 regulated transcription-based stratification of gastric tumors and identification of potential therapeutic candidates

YY1: a key regulator inhibits gastric cancer ferroptosis and mediating apatinib-resistance

OBJECTIVE

Gastric cancer (GC) stands as a prevalent and deadly global malignancy. Despite its role as a preoperative neoadjuvant therapy, Apatinib's effectiveness is curtailed among GC patients exhibiting elevated YY1 expression. YY1's connection to adverse prognosis, drug resistance, and GC metastasis is established, yet the precise underlying mechanisms remain elusive. This study aims to unravel potential pathogenic pathways attributed to YY1.

DESIGN

Utilizing bioinformatics analysis, we conducted differentially expressed genes, functional annotation, and pathway enrichment analyses, and further validation through cellular and animal experiments.

RESULTS

Higher YY1 expression correlated with diminished postoperative progression-free survival (PFS) and disease-specific survival (DSS) rates in TCGA analysis, identifying YY1 as an independent DSS indicator in gastric cancer (GC) patients. Notably, YY1 exhibited significantly elevated expression in tumor tissues compared to adjacent normal tissues. Bioinformatics analysis revealed noteworthy differentially expressed genes (DEGs), transcriptional targets, factors, and co-expressed genes associated with YY1. LASSO Cox analysis unveiled Transferrin as a prospective pivotal protein regulated by YY1, with heightened expression linked to adverse DSS and PFS outcomes. YY1's role in governing the p53 signaling pathway and ferroptosis in GC cells was further elucidated. Moreover, YY1 overexpression dampened immune cell infiltration within GC tumors. Additionally, YY1 overexpression hindered GC cell ferroptosis and mediated Apatinib resistance via the p53 pathway. Remarkably, IFN-a demonstrated efficacy in reversing Apatinib resistance and immune suppression in GC tissues.

CONCLUSIONS

Our findings underscore the pivotal role of YY1 in driving GC progression and influencing prognosis, thus pinpointing it as a promising therapeutic target to enhance patient outcomes.

BRD4-binding enhancer promotes CRC progression by interacting with YY1 to activate the Wnt pathway through upregulation of TCF7L2

Colorectal carcinoma (CRC), one of the most life-threatening cancer types, is associated with aberrant expression of epigenetic modifiers and activation of the Wnt pathway. However, the role of epigenetic regulators in driving cancer cell proliferation and their potential as therapeutic targets affecting the Wnt pathway remain unclear. In this study, BRD4 was found to promote the progression of CRC both in vitro and in vivo. The expression of BRD4 correlated with shortened CRC patient survival. In addition, BRD4 function was strongly correlated with the Wnt pathway, but rather through regulation of TCF7L2 at transcriptional levels. BRD4 and H3K27ac have overlapping occupancies in the cis-regulatory elements of TCF7L2, suggesting enhancer-based epigenetic regulation. Numerous YY1 binding sites were found in the abovementioned region. YY1 recruited BRD4 to bind to cis-regulatory elements of TCF7L2, thereby regulating the expression of TCF7L2. Altogether, this study validates that BRD4 performs a canonical epigenetic regulatory function in CRC and can be used in the treatment of Wnt pathway-dependent CRC or other malignancies with clinically available bromodomain inhibitors.

Genetic analysis of fundic gland‑type gastric adenocarcinoma

This study aimed to analyze the molecular characteristics of gastric adenocarcinoma of the fundic-gland type (GAFG) and explore the possible mechanism of tumor development. Samples from 10 Chinese patients with GAFG were collected at the Peking University International Hospital and Liaocheng People's Hospital between January 2015 and March 2022. The nucleic acid sequence of Epstein Barr virus-encoded RNA (EBV-EBER) was detected by in situ hybridization. Genetic mutation information for GNAS, KRAS, NRAS, BRAF, PIK3CA, TP53, APC, CTNNB1, HER2, MLH1, MSH2, MSH6, and PMS2 was obtained by Next-Generation Sequencing, and the relevant literature was reviewed. A total of eight instances of missense mutations were detected, consisting of seven cases with GNAS mutations, two cases with KRAS mutations, and one case with a TP53 mutation. Additionally, two patients had simultaneous missense mutations in GNAS and KRAS. Nonsynonymous mutations in APC, CTNNB1, NRAS, BRAF, PIK3CA, HER2, MLH1, MSH2, MSH6, or PMS2 were not observed in any cases. In addition, all tumors were EBER-negative. GAFG exhibits diversity at the molecular level, and GNAS mutations are more common than KRAS mutations, TP53 mutations, and microsatellite instability. To date, no association between EBV/HER2 and GAFG has been found.

Binding of YY1/CREB to an Enhancer Region Triggers Claudin 6 Expression in H. pylori LPS-Stimulated AGS Cells

Aberrant expression of the tight junction protein claudin 6 (CLDN6) is a hallmark of gastric cancer progression. Its expression is regulated by the cAMP response element-binding protein (CREB). In gastric cancer induced by Helicobacter pylori (H. pylori) there is no information regarding what transcription factors induce/upregulate the expression of CLDN6. We aimed to identify whether CREB and Yin Yang1 (YY1) regulate the expression of CLDN6 and the site where they bind to the promoter sequence. Bioinformatics analysis, H. pylori lipopolysaccharide (LPS), YY1 and CREB silencing, Western blot, luciferase assays, and chromatin immunoprecipitation experiments were performed using the stomach gastric adenocarcinoma cell line AGS. A gen reporter assay suggested that the initial 2000 bp contains the regulatory sequence associated with CLDN6 transcription; the luciferase assay demonstrated three different regions with transcriptional activity, but the -901 to -1421 bp region displayed the maximal transcriptional activity in response to LPS. Fragment 1279-1421 showed CREB and, surprisingly, YY1 occupancy. Sequential Chromatin Immunoprecipitation (ChIP) experiments confirmed that YY1 and CREB interact in the 1279-1421 region. Our results suggest that CLDN6 expression is regulated by the binding of YY1 and CREB in the 901-1421 enhancer, in which a non-described interaction of YY1 with CREB was established in the 1279-1421 region.

SETD7 promotes metastasis of triple-negative breast cancer by YY1 lysine methylation

Breast cancer has gradually become the predominant cause for cancer-associated death in women. The metastatic dissemination and underlying mechanisms of triple-negative breast cancer (TNBC) are not sufficiently understood. (Su(var)3-9, enhancer of zeste, Trithorax) domain-containing protein 7 (SETD7) is vital for promoting the metastasis of TNBC, as demonstrated in this study. Clinical outcomes were significantly worse in primary metastatic TNBC with upregulated SETD7. Overexpression of SETD7 in vitro and in vivo promotes migration of TNBC cells. Two highly conserved lysine (K) residues K173 and K411 of Yin Yang 1 (YY1) are methylated by SETD7. Further, we found that SETD7-mediated K173 residue methylation protects YY1 from the ubiquitin-proteasome degradation. Mechanistically, it was found that the SETD7/YY1 axis regulates epithelial-mesenchymal transition (EMT) and tumor cell migration via the ERK/MAPK pathway in TNBC. The findings indicated that TNBC metastasis is driven by a novel pathway, which may be a promising target for advanced TNBC treatment.

Chromatin and noncoding RNA-mediated mechanisms of gastric tumorigenesis

Gastric cancer (GC) is one of the most common and deadly cancers in the world. It is a multifactorial disease highly influenced by environmental factors, which include radiation, smoking, diet, and infectious pathogens. Accumulating evidence suggests that epigenetic regulators are frequently altered in GC, playing critical roles in gastric tumorigenesis. Epigenetic regulation involves DNA methylation, histone modification, and noncoding RNAs. While it is known that environmental factors cause widespread alterations in DNA methylation, promoting carcinogenesis, the chromatin- and noncoding RNA-mediated mechanisms of gastric tumorigenesis are still poorly understood. In this review, we focus on discussing recent discoveries addressing the roles of histone modifiers and noncoding RNAs and the mechanisms of their interactions in gastric tumorigenesis. A better understanding of epigenetic regulation would likely facilitate the development of novel therapeutic approaches targeting specific epigenetic regulators in GC.

LINC00858 stabilizes RAN expression and promotes metastasis of gastric cancer

Metastasis constitutes one of the major causes of tumor-related death in gastric cancer (GC), and understanding key events in the initiation of this phenotypic switch may provide therapeutic opportunities. Long noncoding RNAs (lncRNAs) are emerging as molecules that play vital roles in tumorigenesis and metastasis. In this study, we aimed to identify metastasis-related lncRNAs in the context of GC. The lncRNAs overexpressed in tumor tissues and positively associated with overall survival were screened out using the TCGA database. qPCR assays in clinical samples showed that LINC00858 was significantly upregulated in GC tissues compared with normal counterparts. Functional analysis suggested that LINC00858 depletion attenuated the migration, and invasion of cancer cells in vitro and suppressed the metastasis of xenografted tumors in vivo. Mechanistically, LINC00858 could interact with the metastasis-associated RAN and stabilize its protein expression by decreasing posttranslational ubiquitination. The transcription factor YY1 could bind to the promoter of LINC00858 to upregulate its expression in GC cells. Moreover, overexpression of YY1 and RAN was positively associated with upregulation of LINC00858 in GC tissues. Our results suggest that LINC00858 might play a role in GC metastasis, and be a diagnostic biomarker and potential therapeutic target.

A DCS-related lncRNA signature predicts the prognosis and chemotherapeutic response of patients with gastric cancer

The combination of docetaxel, cisplatin, and S-1 (DCS) is a common chemotherapy regimen for patients with gastric cancer (GC). However, studies on long noncoding RNAs (lncRNAs) associated with the chemotherapeutic response to and prognosis after DCS remain lacking. The aim of the present study was to identify DCS mRNAs-lncRNAs associated with chemotherapy response and prognosis in GC patients. In the present study, we identified 548 lncRNAs associated with these 16 mRNAs in the TCGA and GSE31811 datasets. Eleven lncRNAs were used to construct a prognostic signature by least absolute shrinkage and selection operator (LASSO) regression. A model including the 11 lncRNAs (LINC02532, AC007277.1, AC005324.4, AL512506.1, AC068790.7, AC022509.2, AC113139.1, LINC00106, AC005165.1, MIR100HG, and UBE2R2-AS1) associated with the prognosis of GC was constructed. The signature was validated in the TCGA database, model comparison, and qRT-PCR experiments. The results showed that the risk signature was a more effective prognostic factor for GC patients. Furthermore, the results showed that this model can well predicting chemotherapy drug response and immune infiltration of GC patients. In addition, our experimental results indicated that lower expression levels of LINC00106 and UBE2R2-AS1 predicted worse drug resistance in AGS/DDP cells. The experimental results agreed with the predictions. Furthermore, knockdown of LINC00106 or UBE2R2-AS1 can significantly enhanced the proliferation and migration of GC AGS cells in vitro. In conclusion, a novel DCS therapy-related lncRNA signature may become a new strategy to predict chemotherapy response and prognosis in GC patients. LINC00106 and UBE2R2-AS1 may exhibit a tumor suppressive function in GC.

Transcriptional Regulation of ING5 and its Suppressive Effects on Gastric Cancer

ING5 targets histone acetyltransferase or histone deacetylase complexes for local chromatin remodeling. Its transcriptional regulation and suppressive effects on gastric cancer remain elusive. Luciferase assay, EMSA, and ChIP were used to identify the cis-acting elements and trans-acting factors of the ING5 gene. We analyzed the effects of SAHA on the aggressive phenotypes of ING5 transfectants, and the effects of different ING5 mutants on aggressive phenotypes in SGC-7901 cells. Finally, we observed the effects of ING5 abrogation on gastric carcinogenesis. EMSA and ChIP showed that both SRF (−717 to −678 bp) and YY1 (−48 to 25bp) interacted with the promoter of ING5 and up-regulated ING5 expression in gastric cancer via SRF-YY1-ING5-p53 complex formation. ING5, SRF, and YY1 were overexpressed in gastric cancer, (P<0.05), and associated with worse prognosis of gastric cancer patients (P<0.05). ING5 had positive relationships with SRF and YY1 expression in gastric cancer (P<0.05). SAHA treatment caused early arrest at S phase in ING5 transfectants of SGC-7901 (P<0.05), and either 0.5 or 1.0 μM SAHA enhanced their migration and invasion (P<0.05). The wild-type and mutant ING5 transfectants showed lower viability and invasion than the control (P<0.05) with low CDC25, VEGF, and MMP-9 expression. Gastric spontaneous adenocarcinoma was observed in Atp4b-cre; ING5^f/f, Pdx1-cre; ING5^f/f, and K19-cre; ING5^f/f mice. ING5 deletion increased the sensitivity of MNU-induced gastric carcinogenesis. ING5 mRNA might be a good marker of gastric carcinogenesis, and poor prognosis. ING5 expression was positively regulated by the interaction of SRF-YY1-ING5-p53 complex within the ING5 promoter from −50 bp upstream to the transcription start site. ING5 deletion might contribute to the tumorigenesis and histogenesis of gastric cancer.

MiR-98-3p regulates ovarian granulosa cell proliferation and apoptosis in polycystic ovary syndrome by targeting YY1

Polycystic ovary syndrome (PCOS) is a common endocrinopathy related to female infertility. We investigated the function of the microRNA-98-3p (miR-98-3p)/Yin-Yang-1 (YY1) axis to the pathophysiological processes in PCOS mice. A mouse model of PCOS was established using dehydroepiandrosterone (DHEA). Hematoxylin and eosin (HE) staining was used to assess morphologic changes of the ovaries. Hormonal serum levels were measured by ELISA. Estrogen synthesis in OGCs was measured using chemiluminescence immunoassay. The viability, cell cycle, and apoptosis of ovarian granulosa cells (OGCs) were assessed by CCK-8, flow cytometry, and western blot. Luciferase reporter assays were conducted to examine the binding of miR-98-3p to YY1. YY1 was upregulated, while miR-98-3p was downregulated both in the ovarian tissues of PCOS mice and OGCs separated from PCOS mice and patients. YY1 Knockdown promoted OGC proliferation and inhibited apoptosis as well as increased estrogen production in OGCs. YY1 was verified to be targeted by miR-98-3p. Additionally, YY1 overexpression prevented the effects of miR-98-3p overexpression on the proliferation and apoptosis of OGCs. Importantly, miR-98-3p attenuated ovarian injury in PCOS mice. MiR-98-3p targets and downregulates YY1 expression, thereby affecting the proliferation and apoptosis of OGCs in PCOS.