Mechanism of ERBB2 gene overexpression by the formation of super-enhancer with genomic structural abnormalities in lung adenocarcinoma without clinically actionable genetic alterations.

BACKGROUND: In an extensive genomic analysis of lung adenocarcinomas (LUADs), driver mutations have been recognized as potential targets for molecular therapy. However, there remain cases where target genes are not identified. Super-enhancers and structural variants are frequently identified in several hundred loci per case. Despite this, most cancer research has approached the analysis of these data sets separately, without merging and comparing the data, and there are no examples of integrated analysis in LUAD. METHODS: We performed an integrated analysis of super-enhancers and structural variants in a cohort of 174 LUAD cases that lacked clinically actionable genetic alterations. To achieve this, we conducted both WGS and H3K27Ac ChIP-seq analyses using samples with driver gene mutations and those without, allowing for a comprehensive investigation of the potential roles of super-enhancer in LUAD cases. RESULTS: We demonstrate that most genes situated in these overlapped regions were associated with known and previously unknown driver genes and aberrant expression resulting from the formation of super-enhancers accompanied by genomic structural abnormalities. Hi-C and long-read sequencing data further corroborated this insight. When we employed CRISPR-Cas9 to induce structural abnormalities that mimicked cases with outlier ERBB2 gene expression, we observed an elevation in ERBB2 expression. These abnormalities are associated with a higher risk of recurrence after surgery, irrespective of the presence or absence of driver mutations. CONCLUSIONS: Our findings suggest that aberrant gene expression linked to structural polymorphisms can significantly impact personalized cancer treatment by facilitating the identification of driver mutations and prognostic factors, contributing to a more comprehensive understanding of LUAD pathogenesis.

Integrative analysis reveals early epigenetic alterations in high-grade serous ovarian carcinomas.

High-grade serous ovarian carcinoma (HGSOC) is the most lethal gynecological malignancy. To date, the profiles of gene mutations and copy number alterations in HGSOC have been well characterized. However, the patterns of epigenetic alterations and transcription factor dysregulation in HGSOC have not yet been fully elucidated. In this study, we performed integrative omics analyses of a series of stepwise HGSOC model cells originating from human fallopian tube secretory epithelial cells (HFTSECs) to investigate early epigenetic alterations in HGSOC tumorigenesis. Assay for transposase-accessible chromatin using sequencing (ATAC-seq), chromatin immunoprecipitation sequencing (ChIP-seq), and RNA sequencing (RNA-seq) methods were used to analyze HGSOC samples. Additionally, protein expression changes in target genes were confirmed using normal HFTSECs, serous tubal intraepithelial carcinomas (STICs), and HGSOC tissues. Transcription factor motif analysis revealed that the DNA-binding activity of the AP-1 complex and GATA family proteins was dysregulated during early tumorigenesis. The protein expression levels of JUN and FOSL2 were increased, and those of GATA6 and DAB2 were decreased in STIC lesions, which were associated with epithelial-mesenchymal transition (EMT) and proteasome downregulation. The genomic region around the FRA16D site, containing a cadherin cluster region, was epigenetically suppressed by oncogenic signaling. Proteasome inhibition caused the upregulation of chemokine genes, which may facilitate immune evasion during HGSOC tumorigenesis. Importantly, MEK inhibitor treatment reversed these oncogenic alterations, indicating its clinical effectiveness in a subgroup of patients with HGSOC. This result suggests that MEK inhibitor therapy may be an effective treatment option for chemotherapy-resistant HGSOC.

The JmjC domain-containing histone demethylase KDM3A is a positive regulator of the G1/S transition in cancer cells via transcriptional regulation of the HOXA1 gene.

A number of histone demethylases have been identified and biochemically characterized, yet their biological functions largely remain uncharacterized, particularly in the context of human diseases such as cancer. In this study, we describe important roles for the histone demethylase KDM3A, also known as JMJD1A, in human carcinogenesis. Expression levels of KDM3A were significantly elevated in human bladder carcinomas compared with nonneoplastic bladder tissues (p < 0.0001), when assessed by real-time PCR. We confirmed that some other cancers including lung cancer also overexpressed KDM3A, using cDNA microarray analysis. Treatment of cancer cell lines with small interfering RNA targeting KDM3A significantly knocked down its expression and resulted in the suppression of proliferation. Importantly, we found that KDM3A activates transcription of the HOXA1 gene through demethylating histone H3 at lysine 9 di-methylation by binding to its promoter region. Indeed, expression levels of KDM3A and HOXA1 in several types of cancer cell lines and bladder cancer samples were statistically correlated. We observed the down-regulation of HOXA1 as well as CCND1 after treatment with KDM3A siRNA, indicating G(1) arrest of cancer cells. Together, our results suggest that elevated expression of KDM3A plays a critical role in the growth of cancer cells, and further studies may reveal a cancer therapeutic potential in KDM3A inhibition.

Downregulation of METTL6 mitigates cell progression, migration, invasion and adhesion in hepatocellular carcinoma by inhibiting cell adhesion molecules.

RNA modifications have attracted increasing interest in recent years because they have been frequently implicated in various human diseases, including cancer, highlighting the importance of dynamic post­transcriptional modifications. Methyltransferase­like 6 (METTL6) is a member of the RNA methyltransferase family that has been identified in many cancers; however, little is known about its specific role or mechanism of action. In the present study, we aimed to study the expression levels and functional role of METTL6 in hepatocellular carcinoma (HCC), and further investigate the relevant pathways. To this end, we systematically conducted bioinformatics analysis of METTL6 in HCC using gene expression data and clinical information from a publicly available dataset. The mRNA expression levels of METTL6 were significantly upregulated in HCC tumor tissues compared to that in adjacent non­tumor tissues and strongly associated with poorer survival outcomes in patients with HCC. CRISPR/Cas9­mediated knockout of METTL6 in HCC cell lines remarkably inhibited colony formation, cell proliferation, cell migration, cell invasion and cell attachment ability. RNA sequencing analysis demonstrated that knockout of METTL6 significantly suppressed the expression of cell adhesion­related genes. However, chromatin immunoprecipitation sequencing results revealed no significant differences in enhancer activities between cells, which suggests that METTL6 may regulate genes of interest post­transcriptionally. In addition, it was demonstrated for the first time that METTL6 was localized in the cytosol as detected by immunofluorescence analysis, which indicates the plausible location of RNA modification mediated by METTL6. Our findings provide further insight into the function of RNA modifications in cancer and suggest a possible role of METTL6 as a therapeutic target in HCC.

Tumor Suppressive Role of the PRELP Gene in Ovarian Clear Cell Carcinoma.

Ovarian clear cell carcinoma (OCCC) has a poor prognosis, and its therapeutic strategy has not been established. PRELP is a leucine-rich repeat protein in the extracellular matrix of connective tissues. Although PRELP anchors the basement membrane to the connective tissue and is absent in most epithelial cancers, much remains unknown regarding its function as a regulator of ligand-mediated signaling pathways. Here, we obtained sets of differentially expressed genes by PRELP expression using OCCC cell lines. We found that more than 1000 genes were significantly altered by PRELP expression, particularly affecting the expression of a group of genes involved in the PI3K-AKT signaling pathway. Furthermore, we revealed the loss of active histone marks on the loci of the PRELP gene in patients with OCCC and how its forced expression inhibited cell proliferation. These findings suggest that PRELP is not only a molecule anchored in connective tissues but is also a signaling molecule acting in a tumor-suppressive manner. It can serve as the basis for early detection and novel therapeutic approaches for OCCC toward precision medicine.

The metabolic stress-activated checkpoint LKB1-MARK3 axis acts as a tumor suppressor in high-grade serous ovarian carcinoma.

High-grade serous ovarian carcinoma (HGSOC) is the most aggressive gynecological malignancy, resulting in approximately 70% of ovarian cancer deaths. However, it is still unclear how genetic dysregulations and biological processes generate the malignant subtype of HGSOC. Here we show that expression levels of microtubule affinity-regulating kinase 3 (MARK3) are downregulated in HGSOC, and that its downregulation significantly correlates with poor prognosis in HGSOC patients. MARK3 overexpression suppresses cell proliferation and angiogenesis of ovarian cancer cells. The LKB1-MARK3 axis is activated by metabolic stress, which leads to the phosphorylation of CDC25B and CDC25C, followed by induction of G2/M phase arrest. RNA-seq and ATAC-seq analyses indicate that MARK3 attenuates cell cycle progression and angiogenesis partly through downregulation of AP-1 and Hippo signaling target genes. The synthetic lethal therapy using metabolic stress inducers may be a promising therapeutic choice to treat the LKB1-MARK3 axis-dysregulated HGSOCs.

Genome-Wide Chromatin Analysis of FFPE Tissues Using a Dual-Arm Robot with Clinical Potential.

Although chromatin immunoprecipitation and next-generation sequencing (ChIP-seq) using formalin-fixed paraffin-embedded tissue (FFPE) has been reported, it remained elusive whether they retained accurate transcription factor binding. Here, we developed a method to identify the binding sites of the insulator transcription factor CTCF and the genome-wide distribution of histone modifications involved in transcriptional activation. Importantly, we provide evidence that the ChIP-seq datasets obtained from FFPE samples are similar to or even better than the data for corresponding fresh-frozen samples, indicating that FFPE samples are compatible with ChIP-seq analysis. H3K27ac ChIP-seq analyses of 69 FFPE samples using a dual-arm robot revealed that driver mutations in EGFR were distinguishable from pan-negative cases and were relatively homogeneous as a group in lung adenocarcinomas. Thus, our results demonstrate that FFPE samples are an important source for epigenomic research, enabling the study of histone modifications, nuclear chromatin structure, and clinical data.

Deregulation of the Histone Lysine-Specific Demethylase 1 Is Involved in Human Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and is a leading cause of cancer-related death worldwide. Given that the standard-of-care for advanced liver cancer is limited, there is an urgent need to develop a novel molecular targeted therapy to improve therapeutic outcomes for HCC. In order to tackle this issue, we conducted functional analysis of the histone lysine-specific demethylase (LSD1) to explore the possibility that this enzyme acts as a therapeutic target in HCC. According to immunohistochemical analysis, 232 of 303 (77%) HCC cases showed positive staining of LSD1 protein, and its expression was correlated with several clinicopathological characteristics, such as female gender, AFP (alpha-fetoprotein) levels, and HCV (hepatitis C virus) infectious. The survival curves for HCC using the Kaplan-Meier method and the log-rank test indicate that positive LSD1 protein expression was significantly associated with decreased rates of overall survival (OS) and disease-free survival (DFS); the multivariate analysis indicates that LSD1 expression was an independent prognostic factor for both OS and DFS in patients with HCC. In addition, knockout of LSD1 using the CRISPR/Cas9 system showed a significantly lower number of colony formation units (CFUs) and growth rate in both SNU-423 and SNU-475 HCC cell lines compared to the corresponding control cells. Moreover, LSD1 knockout decreased cells in S phase of SNU-423 and SNU-475 cells with increased levels of H3K4me1/2 and H3K9me1/2. Finally, we identified the signaling pathways regulated by LSD1 in HCC, including the retinoic acid (RA) pathway. Our findings imply that deregulation of LSD1 can be involved in HCC; further studies may explore the usefulness of LSD1 as a therapeutic target of HCC.

Enhanced HSP70 lysine methylation promotes proliferation of cancer cells through activation of Aurora kinase B.

Although heat-shock protein 70 (HSP70), an evolutionarily highly conserved molecular chaperone, is known to be post-translationally modified in various ways such as phosphorylation, ubiquitination and glycosylation, physiological significance of lysine methylation has never been elucidated. Here we identify dimethylation of HSP70 at Lys-561 by SETD1A. Enhanced HSP70 methylation was detected in various types of human cancer by immunohistochemical analysis, although the methylation was barely detectable in corresponding non-neoplastic tissues. Interestingly, methylated HSP70 predominantly localizes to the nucleus of cancer cells, whereas most of the HSP70 protein locates to the cytoplasm. Nuclear HSP70 directly interacts with Aurora kinase B (AURKB) in a methylation-dependent manner and promotes AURKB activity in vitro and in vivo. We also find that methylated HSP70 has a growth-promoting effect in cancer cells. Our findings demonstrate a crucial role of HSP70 methylation in human carcinogenesis.

Determination of splice-site mutations in Lynch syndrome (hereditary non-polyposis colorectal cancer) patients using functional splicing assay.

Lynch syndrome (hereditary non-polyposis colorectal cancer) is an inherited disease caused by germ-line mutation in mismatch repair genes such as MLH1, MSH2, and MSH6. The mutations include missense and nonsense mutations, small insertions and deletions, and gross genetic alterations including large deletions and duplications. In addition to these genetic changes, mutations in introns are also involved in the pathogenesis. However, it is sometimes difficult to interpret correctly the pathogenicity of variants in exons as well as introns. To evaluate the effect of splice-site mutations in two Lynch syndrome patients, we carried out a functional splicing assay using minigenes. Consequently, this assay showed that the mutation of c.1731+5G>A in MLH1 led to exon15 skipping, and that the mutation of c.211+1G>C in MSH2 created an activated cryptic splice-site 17-nucleotides upstream in exon1. These aberrant splicing patterns were not observed when wild type sequence was used for the assay. We also obtained concordant results by RT-PCR experiments with transcripts from the patients. Furthermore, additional functional splicing assays using two different intronic mutations described in earlier studies revealed splicing alterations that were in complete agreement with the reports. Therefore, functional splicing assay is helpful for evaluating the effects of genetic variants on splicing.