Upregulation of histone acetylation reverses organic anion transporter 2 repression and enhances 5-fluorouracil sensitivity in hepatocellular carcinoma

Strategies to enhance the response of liver cancer to pharmacological treatments

In contrast to other types of cancers, there is no available efficient pharmacological treatment to improve the outcomes of patients suffering from major primary liver cancers, i.e., hepatocellular carcinoma and cholangiocarcinoma. This dismal situation is partly due to the existence in these tumors of many different and synergistic mechanisms of resistance, accounting for the lack of response of these patients, not only to classical chemotherapy but also to more modern pharmacological agents based on the inhibition of tyrosine kinase receptors (TKIs) and the stimulation of the immune response against the tumor using immune checkpoint inhibitors (ICIs). This review summarizes the efforts to develop strategies to overcome this severe limitation, including searching for novel drugs derived from synthetic, semisynthetic, or natural products with vectorial properties against therapeutic targets to increase drug uptake or reduce drug export from cancer cells. Besides, immunotherapy is a promising line of research that is already starting to be implemented in clinical practice. Although less successful than in other cancers, the foreseen future for this strategy in treating liver cancers is considerable. Similarly, the pharmacological inhibition of epigenetic targets is highly promising. Many novel "epidrugs," able to act on "writer," "reader," and "eraser" epigenetic players, are currently being evaluated in preclinical and clinical studies. Finally, gene therapy is a broad field of research in the fight against liver cancer chemoresistance, based on the impressive advances recently achieved in gene manipulation. In sum, although the present is still dismal, there is reason for hope in the non-too-distant future.

HDAC7: a promising target in cancer

Histones have a vital function as components of nucleosomes, which serve as the fundamental building blocks of chromatin. Histone deacetylases (HDACs), which target histones, suppress gene transcription by compacting chromatin. This implies that HDACs have a strong connection to the suppression of gene transcription. Histone deacetylase 7 (HDAC7), a member of the histone deacetylase family, may participate in multiple cellular pathophysiological processes and activate relevant signaling pathways to facilitate the progression of different tumors by exerting deacetylation. In recent years, HDAC7 has been increasingly studied in the pathogenesis of tumors. Studies that are pertinent have indicated that it has a significant impact on the growth and metastasis of tumors, the formation of the vascular microenvironment, and the emergence of resistance to drugs. Therefore, HDAC7 could potentially function as a potent predictor for tumor prognosis and a promising target for mitigating drug resistance in tumors. This review primarily concentrates on elucidating the structure and function of HDAC7, its involvement in the development of various tumors, and its interplay with relevant signaling pathways. Meanwhile, we briefly discuss the research direction and prospect of HDAC7.

Effect of changes in metabolic enzymes and transporters on drug metabolism in the context of liver disease: Impact on pharmacokinetics and drug-drug interactions

Changes in the pharmacokinetic and resulting pharmacodynamic properties of drugs are common in many chronic liver diseases, leading to adverse effects, drug interactions and increased risk of over- or underdosing of medications. Structural and functional hepatic impairment can have major effects on drug metabolism and transport. This review summarizes research on the functional changes in phase I and II metabolic enzymes and in transport proteins in patients with metabolic diseases such as type 2 diabetes, metabolic dysfunction-associated steatotic liver disease, metabolic dysfunction-associated steatohepatitis and cirrhosis, providing a clinical perspective on how these changes affect drug uptake and metabolism. Generally, a decrease in expression and/or activity of many enzymes of the cytochrome P450 family (e.g. CYP2E1 and CYP3A4), and of influx and efflux transporters (e.g. organic anion-transporting polypeptide [OATP]1B1, OATP2B1, OAT2 and bile salt export pump), has been recently documented in patients with liver disease. Decreased enzyme levels often correlate with increased severity of chronic liver disease. In subjects with hepatic impairment, there is potential for strong alterations of drug pharmacokinetics due to reduced absorption, increased volume of distribution, metabolism and extraction. Due to the altered pharmacokinetics, specific drug-drug interactions are also a potential issue to consider in patients with liver disease. Given the huge burden of liver disease in western societies, there is a need to improve awareness among all healthcare professionals and patients with liver disease to ensure appropriate drug prescriptions.

Diagnostic and Prognostic Value of Protein Post-translational Modifications in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common malignant tumor with high incidence and cancer mortality worldwide. Post-translational modifications (PTMs) of proteins have a great impact on protein function. Almost all proteins can undergo PTMs, including phosphorylation, acetylation, methylation, glycosylation, ubiquitination, and so on. Many studies have shown that PTMs are related to the occurrence and development of cancers. The findings provide novel therapeutic targets for cancers, such as glypican-3 and mucin-1. Other clinical implications are also found in the studies of PTMs. Diagnostic or prognostic value, and response to therapy have been identified. In HCC, it has been shown that glycosylated alpha-fetoprotein (AFP) has a higher detection rate for early liver cancer than conventional AFP. In this review, we mainly focused on the diagnostic and prognostic value of PTM, in order to provide new insights into the clinical implication of PTM in HCC.

Chromatin factors: Ready to roll as biomarkers in metastatic colorectal cancer?

Colorectal cancer (CRC) ranks as the third most prevalent cancer globally and stands as the fourth leading cause of cancer-related fatalities in 2020. Survival rates for metastatic disease have slightly improved in recent decades, with clinical trials showing median overall survival of approximately 24-30 months. This progress can be attributed to the integration of chemotherapeutic treatments alongside targeted therapies and immunotherapy. Despite these modest improvements, the primary obstacle to successful treatment for advanced CRC lies in the development of chemoresistance, whether inherent or acquired, which remains the major cause of treatment failure. Epigenetics has emerged as a hallmark of cancer, contributing to master transcription regulation and genome stability maintenance. As a result, epigenetic factors are starting to appear as potential clinical biomarkers for diagnosis, prognosis, and prediction of treatment response in CRC.In recent years, numerous studies have investigated the influence of DNA methylation, histone modifications, and chromatin remodelers on responses to chemotherapeutic treatments. While there is accumulating evidence indicating their significant involvement in various types of cancers, the exact relationship between chromatin landscapes and treatment modulation in CRC remains elusive. This review aims to provide a comprehensive summary of the most pertinent and extensively researched epigenetic-associated mechanisms described between 2015 and 2022 and their potential usefulness as predictive biomarkers in the metastatic disease.

Role of sirtuins in hepatocellular carcinoma progression and multidrug resistance: Mechanistical and pharmacological perspectives

Hepatocellular carcinoma (HCC) is the third most common cause of death from cancer worldwide. Therapeutic strategies are still challenging due to the high relapse rate after surgery and multidrug resistance (MDR). It is essential to better understand the mechanisms for HCC progression and MDR for the development of new therapeutic strategies. Mammalian sirtuins (SIRTs), a family of seven members, are related to tumor progression, MDR and prognosis and were proposed as potential prognostic markers, as well as therapeutic targets for treating cancer. SIRT1 is the most studied member and is overexpressed in HCC, playing an oncogenic role and predicting poor prognosis. Several manuscripts describe the role of SIRTs2-7 in HCC; most of them report an oncogenic role for SIRT2 and -7 and a suppressive role for SIRT3 and -4. The scenario is more confusing for SIRT5 and -6, since information is contradictory and scarce. For SIRT1 many inhibitors are available and they seem to hold therapeutic promise in HCC. For the other members the development of specific modulators has just started. This review is aimed to describe the features of SIRTs1-7 in HCC, and the role they play in the onset and progression of the disease. Also, when possible, we will depict the information related to the SIRTs modulators that have been tested in HCC and their possible implication in MDR. With this, we hope to clarify the role of each member in HCC and to shed some light on the most successful strategies to overcome MDR.

The Role of Solute Carrier Transporters in Efficient Anticancer Drug Delivery and Therapy

Transporter-mediated drug resistance is a major obstacle in anticancer drug delivery and a key reason for cancer drug therapy failure. Membrane solute carrier (SLC) transporters play a crucial role in the cellular uptake of drugs. The expression and function of the SLC transporters can be down-regulated in cancer cells, which limits the uptake of drugs into the tumor cells, resulting in the inefficiency of the drug therapy. In this review, we summarize the current understanding of low-SLC-transporter-expression-mediated drug resistance in different types of cancers. Recent advances in SLC-transporter-targeting strategies include the development of transporter-utilizing prodrugs and nanocarriers and the modulation of SLC transporter expression in cancer cells. These strategies will play an important role in the future development of anticancer drug therapies by enabling the efficient delivery of drugs into cancer cells.

Roles and regulation of histone acetylation in hepatocellular carcinoma

Hepatocellular Carcinoma (HCC) is the most frequent malignant tumor of the liver, but its prognosis is poor. Histone acetylation is an important epigenetic regulatory mode that modulates chromatin structure and transcriptional status to control gene expression in eukaryotic cells. Generally, histone acetylation and deacetylation processes are controlled by the opposing activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Dysregulation of histone modification is reported to drive aberrant transcriptional programmes that facilitate liver cancer onset and progression. Emerging studies have demonstrated that several HDAC inhibitors exert tumor-suppressive properties via activation of various cell death molecular pathways in HCC. However, the complexity involved in the epigenetic transcription modifications and non-epigenetic cellular signaling processes limit their potential clinical applications. This review brings an in-depth view of the oncogenic mechanisms reported to be related to aberrant HCC-associated histone acetylation, which might provide new insights into the effective therapeutic strategies to prevent and treat HCC.

SIRT7 in the aging process

Aging is the result of the accumulation of a wide variety of molecular and cellular damage over time. This has been associated with a number of features termed hallmarks of aging, including genomic instability, loss of proteostasis, telomere attrition, dysregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and impaired intercellular communication. On the other hand, sirtuins are enzymes with an important role in aging and life extension, of which humans have seven paralogs (SIRT1 to SIRT7). SIRT7 is the least studied sirtuin to date, but it has been reported to serve important functions, such as promoting ribosomal RNA expression, aiding in DNA damage repair, and regulating chromatin compaction. Several studies have established a close relationship between SIRT7 and age-related processes, but knowledge in this area is still scarce. Therefore, the purpose of this review was to analyze how SIRT7 is associated with each of the hallmarks of aging, as well as with some of age-associated diseases, such as cardiovascular diseases, obesity, osteoporosis, and cancer.

VARIDT 2.0: structural variability of drug transporter

The structural variability data of drug transporter (DT) are key for research on precision medicine and rational drug use. However, these valuable data are not sufficiently covered by the available databases. In this study, a major update of VARIDT (a database previously constructed to provide DTs' variability data) was thus described. First, the experimentally resolved structures of all DTs reported in the original VARIDT were discovered from PubMed and Protein Data Bank. Second, the structural variability data of each DT were collected by literature review, which included: (a) mutation-induced spatial variations in folded state, (b) difference among DT structures of human and model organisms, (c) outward/inward-facing DT conformations and (d) xenobiotics-driven alterations in the 3D complexes. Third, for those DTs without experimentally resolved structural variabilities, homology modeling was further applied as well-established protocol to enrich such valuable data. As a result, 145 mutation-induced spatial variations of 42 DTs, 1622 inter-species structures originating from 292 DTs, 118 outward/inward-facing conformations belonging to 59 DTs, and 822 xenobiotics-regulated structures in complex with 57 DTs were updated to VARIDT (https://idrblab.org/varidt/ and http://varidt.idrblab.net/). All in all, the newly collected structural variabilities will be indispensable for explaining drug sensitivity/selectivity, bridging preclinical research with clinical trial, revealing the mechanism underlying drug-drug interaction, and so on.

Feature, Function, and Information of Drug Transporter Related Databases

With the rapid progress in pharmaceutical experiments and clinical investigations, extensive knowledge of drug transporters (DTs) has accumulated, which is valuable data for the understanding of drug metabolism and disposition. However, such data is largely dispersed in the literature, which hampers its utility and significantly limits its possibility for comprehensive analysis. A variety of databases have, therefore, been constructed to provide DT-related data, and they were reviewed in this study. First, several knowledge bases providing data regarding clinically important drugs and their corresponding transporters were discussed, which constituted the most important resources of DT-centered data. Second, some databases describing the general transporters and their functional families were reviewed. Third, various databases offering transporter information as part of their entire data collection were described. Finally, customized database functions that are available to facilitate DT-related research were discussed. This review provided an overview of the whole collection of DT-related databases, which might facilitate research on precision medicine and rational drug use. Significance Statement A collection of well-established databases related to DTs were comprehensively reviewed, which were organized according to their importance in drug ADME research. These databases could collectively contribute to the research on rational drug use.