Promoter hypermethylation of early B cell factor 1 (EBF1) is associated with cholangiocarcinoma progression

The roles of epigenetic regulation in cholangiocarcinogenesis

Cholangiocarcinoma (CCA), a heterogeneous malignancy of bile duct epithelial cells, is characterized by aggressiveness, difficult diagnosis, and poor prognosis due to limited understanding and lack of effective therapeutic strategies. Genetic and epigenetic alterations accumulated in CCA cells can cause the aberrant regulation of oncogenes and tumor suppressors. Epigenetic alterations with histone modification, DNA methylation, and noncoding RNA modulation are associated with the carcinogenesis of CCA. Mutation or silencing of genes by various mechanisms can be a frequent event during CCA development. Alterations in histone acetylation/deacetylation at the posttranslational level, DNA methylation at promoters, and noncoding RNA regulation contribute to the heterogeneity of CCA and drive tumor development. In this review article, we mainly focus on the roles of epigenetic regulation in cholangiocarcinogenesis. Alterations in epigenetic modification can be potential targets for the therapeutic management of CCA, and epigenetic targets may become diagnostic biomarkers of CCA.

Overexpression of Insulin Receptor Substrate 1 (IRS1) Relates to Poor Prognosis and Promotes Proliferation, Stemness, Migration, and Oxidative Stress Resistance in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is one of the oxidative stress-driven carcinogenesis through chronic inflammation. Insulin receptor substrate 1 (IRS1), an adaptor protein of insulin signaling pathways, is associated with the progression of many inflammation-related cancers. This study hypothesized that oxidative stress regulates IRS1 expression and that up-regulation of IRS1 induces CCA progression. The localizations of IRS1 and an oxidative stress marker (8-oxodG) were detected in CCA tissues using immunohistochemistry (IHC). The presence of IRS1 in CCA tissues was confirmed using immortal cholangiocyte cells (MMNK1), a long-term oxidative-stress-induced cell line (ox-MMNK1-L), and five CCA cell lines as cell culture models. IRS1 was overexpressed in tumor cells and this was associated with a shorter patient survival time and an increase in 8-oxodG. IRS1 expression was higher in ox-MMNK1-L cells than in MMNK1 cells. Knockdown of IRS1 by siRNA in two CCA cell lines led to inhibition of proliferation, cell cycle progression, migration, invasion, stemness, and oxidative stress resistance properties. Moreover, a transcriptomics study demonstrated that suppressing IRS1 in the KKU-213B CCA cell line reduced the expression levels of several genes and pathways involved in the cellular functions. The findings indicate that IRS1 is a key molecule in the connection between oxidative stress and CCA progression. Therefore, IRS1 and its related genes can be used as prognostic markers and therapeutic targets for CCA therapy.

DNA methylation in cell plasticity and malignant transformation in liver diseases

The liver possesses extraordinary regenerative capacity mainly attributable to the ability of hepatocytes (HCs) and biliary epithelial cells (BECs) to self-replicate. This ability is left over from their bipotent parent cell, the hepatoblast, during development. When this innate regeneration is compromised due to the absence of proliferative parenchymal cells, such as during cirrhosis, HCs and BEC can transdifferentiate; thus, adding another layer of complexity to the process of liver repair. In addition, dysregulated lineage maintenance in these two cell populations has been shown to promote malignant growth in experimental conditions. Here, malignant transformation, driven in part by insufficient maintenance of lineage reprogramming, contributes to end-stage liver disease. Epigenetic changes are key drivers for cell fate decisions as well as transformation by finetuning overall transcription and gene expression. In this review, we address how altered DNA methylation contributes to the initiation and progression of hepatic cell fate conversion and cancer formation. We also discussed the diagnostic and therapeutic potential of targeting DNA methylation in liver cancer, its current limitations, and what future research is necessary to facilitate its contribution to clinical translation.

The molecular mechanisms and targeting strategies of transcription factors in cholangiocarcinoma

INTRODUCTION

Cholangiocarcinoma consists of a cluster of malignant biliary tumors that tend to have a poor prognosis, ranking as the second most prevalent type of liver cancer, and their incidence rate has increased globally recently. The high-frequency driving mutations of cholangiocarcinoma, such as KRAS/IDH1/ARID1A/P53, imply the epigenetic instability of cholangiocarcinoma, leading to the dysregulation of various related transcription factors, thus affecting the occurrence and development of cholangiocarcinoma. Increasingly evidence indicates that the high heterogeneity and malignancy of cholangiocarcinoma are closely related to the dysregulation of transcription factors which promote cell proliferation, invasion, migration, angiogenesis, and drug resistance through reprogrammed transcriptional networks. It is of great significance to further explore and summarize the role of transcription factors in cholangiocarcinoma.

AREAS COVERED

This review summarizes the oncogenic or tumor suppressive roles of key transcription factors in regulating cholangiocarcinoma progression and the potential targeting strategies of transcription factors in cholangiocarcinoma.

EXPERT OPINION

Cholangiocarcinoma is a type of cancer highly influenced by transcriptional regulation, specifically transcription factors and epigenetic regulatory factors. Targeting transcription factors could be a potential and important strategy that is likely to impact future cholangiocarcinoma treatment.