Targeting Histone Modifications in Bone and Lung Metastatic Cancers

Bioinformatic analysis of differentially expressed genes in lung cancer bone metastasis and their implications for disease progression in lung cancer patients

Background

Lung cancer is the most commonly diagnosed cancer and the leading cause of cancer-related death worldwide. Moreover, it is highly susceptible to distant metastasis, which is the main cause of pain in advanced lung cancer, and frequently occurs in the bone. This study aimed to identify the differentially expressed genes (DEGs) related to metastatic bone disease in lung cancer using bioinformatics methods and to analyze the risk factors influencing the incidence of secondary bone metastasis in lung cancer.

Methods

Gene expression profiles from the GSE175601 and GSE10799 datasets in the Gene Expression Omnibus (GEO) database were analyzed to screen for the DEGs associated with lung cancer bone metastasis. The STRING database was used to construct a protein-protein interaction (PPI) network, and the MCODE plugin was used to identify the key genes. The expression of these important genes in lung tumor tissues and their correlation with prognosis were validated in The Cancer Genome Atlas (TCGA) database. An examination of clinical data from patients diagnosed with stage IV lung adenocarcinoma treated at the Anhui No. 2 Provincial People's Hospital was conducted. Immunohistochemistry was used to examine the expression of key genes in lung cancer tumor tissues. A binary logistic regression analysis was conducted to examine the interactions in the expression of critical genes associated with bone metastasis in lung carcinoma patients.

Results

In total, 59 DEGs were identified in the GSE175601 and GSE10799 datasets through Venn diagram construction. The PPI network analysis revealed two significant modules and eight candidate genes (LAPTM5, LCP2, CD53, ARHGAP25, C1QA, DES, MYH11, and VIM). According to TCGA database analysis, in carcinogenic tissues of the lung, the expression of these eight critical genes is downregulated. Further, only the lung cancer patients who had high expressions of ARHGAP25 had an improved progress-free interval (PFI) (P<0.05), disease-specific survival (DSS), and overall survival (OS). Of the 49 with stage IV lung adenocarcinoma patients included in the study, 27 (55.10%) developed bone metastasis. The immunohistochemical (IHC) results indicated that the expression score of ARHGAP25 was significantly lower in the group with bone metastasis (3.93±2.95) than the group without bone metastasis (6.64±3.62) (P=0.006). The proportion of patients with low ARHGAP25 expression was significantly higher in the group with bone metastasis (70.37%, 19/27) than the group without bone metastasis (31.82%, 7/22) (P=0.007). The binary logistic regression analysis identified serum alkaline phosphatase (ALP) and ARHGAP25 expression levels as independent risk factors for the occurrence of secondary bone metastatic disease in lung carcinoma patients.

Conclusions

The key gene ARHGAP25 identified through bioinformatics for lung cancer bone metastasis was significantly downregulated. Its low expression constitutes an independent risk factor for secondary bone metastatic disease in patients with lung carcinoma.

A comprehensive epigenetic network can influence the occurrence of thyroid-associated ophthalmopathy by affecting immune and inflammatory response

The primary objective of this study is to understand the regulatory role of epigenetics in thyroid-associated ophthalmopathy (TAO) using multi-omics sequencing data. We utilized tRFs sequencing data, DNA methylation sequencing data, and lncRNA/circRNA/mRNA sequencing data, as well as several RNA methylation target prediction websites, to analyze the regulatory effect of DNA methylation, non-coding RNA, and RNA methylation on TAO-associated genes. Through differential expression analysis, we identified 1019 differentially expressed genes, 985 differentially methylated genes, and 2601 non-coding RNA. Functional analysis showed that differentially expressed genes were mostly associated with the PI3K signaling pathway and the IL17 signaling pathway. Genes regulated by DNA epigenetic regulatory networks were mainly related to the Cytokine-cytokine receptor interaction pathway, whereas genes regulated by RNA epigenetic regulatory networks were primarily related to the T cell receptor signaling pathway. Finally, our integrated regulatory network analysis revealed that epigenetics mainly impacts the occurrence of TAO through its effects on key pathways such as cell killing, cytokine production, and immune response. In summary, this study is the first to reveal a new mechanism underlying the development of TAO and provides new directions for future TAO research.

Epigenetic control of the vicious cycle

Epigenetic alterations, including DNA methylation and post translational modifications to histones, drive tumorigenesis and metastatic progression. In the context of bone metastasis, epigenetic modifications in tumor cells can modulate dissemination of cancer cells to the bone, tumor progression in the bone marrow, and may be associated with patient survival rates. Bone disseminated tumor cells may enter a dormant state or stimulate osteolysis through the "vicious cycle" of bone metastasis where bone disseminated tumor cells disrupt the bone microenvironment, which fuels tumor progression. Epigenetic alterations may either exacerbate or abrogate the vicious cycle by regulating tumor suppressors and oncogenes, which alter proliferation of bone-metastatic cancer cells. This review focuses on the specific epigenetic alterations that regulate bone metastasis, including DNA methylation, histone methylation, and histone acetylation. Here, we summarize key findings from researchers identifying epigenetic changes that drive tumor progression in the bone, along with pre-clinical and clinical studies investigating the utility of targeting aberrant epigenetic alterations to treat bone metastatic cancer.

Epigenetic modifications of inflammation in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common cause of joint-related chronic disability in elderly individuals worldwide. It seriously impacts the quality of life and inflicts a substantial social and economic burden. The pathological mechanisms underlying IDD have not been fully revealed, leading to less satisfactory clinical treatment outcomes. More studies are urgently needed to reveal its precise pathological mechanisms. Numerous studies have revealed that inflammation is closely related to various pathological processes of IDD, including the continuous loss of extracellular matrix, cell apoptosis, and senescence, indicating the important role of inflammation in the pathological mechanism of IDD. Epigenetic modifications affect the functions and characteristics of genes mainly through DNA methylation, histone modification, non-coding RNA regulation, and other mechanisms, thus having a major effect on the survival state of the body. Recently, the role of epigenetic modifications in inflammation during IDD has been attracting research interest. In this review, we summarize the roles of different types of epigenetic modifications in inflammation during IDD in recent years, to improve our understanding of the etiology of IDD and to transform basic research strategy into a clinically effective treatment for joint-related chronic disability in elderly individuals.

HDAC inhibitors stimulate LIFR when it is repressed by hypoxia or PTHrP in breast cancer

Breast cancer cells frequently disseminate to the bone marrow, where they either induce osteolysis or enter a dormant state. Downregulation of leukemia inhibitory factor receptor (LIFR), a known breast tumor suppressor, enables otherwise dormant MCF7 human breast cancer cells to become aggressively osteolytic. Hypoxia (low oxygen tensions), which may develop in tumors as a pathological response to the metabolic demands of the proliferating cells and as a physiological state in the bone, downregulates LIFR in breast cancer cells independent of hypoxia-inducible factor (HIF) signaling. However, the mechanism by which LIFR is repressed in hypoxia is unknown. Histone deacetylase (HDAC) inhibitors stimulate LIFR by increasing histone acetylation in the proximal promoter and induce a dormancy phenotype in breast cancer cells inoculated into the mammary fat pad. We therefore aimed to determine whether hypoxia alters histone acetylation in the LIFR promoter, and whether HDAC inhibitors effectively stimulate LIFR in breast cancer cells residing in hypoxic microenvironments. Herein, we confirmed that disseminated MCF7 cells became hypoxic in the bone and that hypoxia increased the epigenetic transcriptional repressor H3K9me3 in the distal LIFR promoter while H3K9ac, which promotes transcription, was significantly reduced. Furthermore, HDAC inhibitor treatment rescued hypoxic repression and dramatically increased expression of LIFR, p38β, and p21, which regulate tumor dormancy. In a second model of LIFR repression, in which parathyroid hormone-related protein (PTHrP) suppresses LIFR expression, we found that PTHrP binds to the distal LIFR promoter, and that PTHrP suppression of LIFR protein is similarly reversed by HDAC inhibitor treatment. Together, these data suggest that HDAC inhibitors stimulate LIFR regardless of the way it is repressed by the microenvironment.

Deacetylation of Transcription Factors in Carcinogenesis

Reversible Nε-lysine acetylation/deacetylation is one of the most common post-translational modifications (PTM) of histones and non-histone proteins that is regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs). This epigenetic process is highly involved in carcinogenesis, affecting histone and non-histone proteins' properties and their biological functions. Some of the transcription factors, including tumor suppressors and oncoproteins, undergo this modification altering different cell signaling pathways. HDACs deacetylate their targets, which leads to either the upregulation or downregulation of proteins involved in the regulation of cell cycle and apoptosis, ultimately influencing tumor growth, invasion, and drug resistance. Therefore, epigenetic modifications are of great clinical importance and may constitute a new therapeutic target in cancer treatment. This review is aimed to present the significance of HDACs in carcinogenesis through their influence on functions of transcription factors, and therefore regulation of different signaling pathways, cancer progression, and metastasis.