Transcriptional changes associated with reduced spontaneous liver tumor incidence in mice chronically exposed to high dose arsenic

Lipid Metabolism as a Potential Target of Liver Cancer

Hepatocellular carcinoma (HCC) stands as a severe malignant tumor with a profound impact on overall health, often accompanied by an unfavorable prognosis. Despite some advancements in the diagnosis and treatment of this disease, improving the prognosis of HCC remains a formidable challenge. It is noteworthy that lipid metabolism plays a pivotal role in the onset, development, and progression of tumor cells. Existing research indicates the potential application of targeting lipid metabolism in the treatment of HCC. This review aims to thoroughly explore the alterations in lipid metabolism in HCC, offering a detailed account of the potential advantages associated with innovative therapeutic strategies targeting lipid metabolism. Targeting lipid metabolism holds promise for potentially enhancing the prognosis of HCC.

Current therapeutic modalities and chemopreventive role of natural products in liver cancer: Progress and promise

Liver cancer is a severe concern for public health officials since the clinical cases are increasing each year, with an estimated 5-year survival rate of 30%–35% after diagnosis. Hepatocellular carcinoma (HCC) constitutes a significant subtype of liver cancer (approximate75%) and is considered primary liver cancer. Treatment for liver cancer mainly depends on the stage of its progression, where surgery including, hepatectomy and liver transplantation, and ablation and radiotherapy are the prime choice. For advanced liver cancer, various drugs and immunotherapy are used as first-line treatment, whereas second-line treatment includes chemotherapeutic drugs from natural and synthetic origins. Sorafenib and lenvatinib are first-line therapies, while regorafenib and ramucirumab are second-line therapy. Various metabolic and signaling pathways such as Notch, JAK/ STAT, Hippo, TGF-β, and Wnt have played a critical role during HCC progression. Dysbiosis has also been implicated in liver cancer. Drug-induced toxicity is a key obstacle in the treatment of liver cancer, necessitating the development of effective and safe medications, with natural compounds such as resveratrol, curcumin, diallyl sulfide, and others emerging as promising anticancer agents. This review highlights the current status of liver cancer research, signaling pathways, therapeutic targets, current treatment strategies and the chemopreventive role of various natural products in managing liver cancer.

Stearoyl-CoA desaturase 1 as a therapeutic target for cancer: a focus on hepatocellular carcinoma

One of the main characteristics of cancer cells is the alteration in lipid composition, which is associated with a significant monounsaturated fatty acids (MUFAs) enrichment. In addition to their structural functions in newly synthesized membranes in proliferating cancer cells, these fatty acids are involved in tumorigenic signaling. Increased expression and activity of stearoyl CoA desaturase (SCD1), i.e., an enzyme converting saturated fatty acids to Δ9-monounsaturated fatty acids, has been observed in various cancer cells. This increase in expression and activity has also been associated with cancer aggressiveness and poor patient outcome. Previous studies have also indicated the SCD1 involvement in increased cancer cells proliferation, growth, migration, epithelial to mesenchymal transition, metastasis, chemoresistance, and maintenance of cancer stem cells properties. Hence, SCD1 seems to be a player in malignancy development and may be considered a novel therapeutic target in cancers, including hepatocellular carcinoma (HCC). This review study aims to discuss the impact of SCD1 as a major component in lipid signaling in HCC.

Overcoming the cytoplasmic retention of GDOWN1 modulates global transcription and facilitates stress adaptation

Dynamic regulation of transcription is crucial for the cellular responses to various environmental or developmental cues. Gdown1 is a ubiquitously expressed, RNA polymerase II (Pol II) interacting protein, essential for the embryonic development of metazoan. It tightly binds Pol II in vitro and competitively blocks the binding of TFIIF and possibly other transcriptional regulatory factors, yet its cellular functions and regulatory circuits remain unclear. Here, we show that human GDOWN1 strictly localizes in the cytoplasm of various types of somatic cells and exhibits a potent resistance to the imposed driving force for its nuclear localization. Combined with the genetic and microscope-based approaches, two types of the functionally coupled and evolutionally conserved localization regulatory motifs are identified, including the CRM1-dependent nucleus export signal (NES) and a novel Cytoplasmic Anchoring Signal (CAS) that mediates its retention outside of the nuclear pore complexes (NPC). Mutagenesis of CAS alleviates GDOWN1's cytoplasmic retention, thus unlocks its nucleocytoplasmic shuttling properties, and the increased nuclear import and accumulation of GDOWN1 results in a drastic reduction of both Pol II and its associated global transcription levels. Importantly, the nuclear translocation of GDOWN1 occurs in response to the oxidative stresses, and the ablation of GDOWN1 significantly weakens the cellular tolerance. Collectively, our work uncovers the molecular basis of GDOWN1's subcellular localization and a novel cellular strategy of modulating global transcription and stress-adaptation via controlling the nuclear translocation of GDOWN1.

Aberrant lipid metabolism as a therapeutic target in liver cancer

INTRODUCTION

Hepatocellular carcinoma (HCC) is one of the most common and lethal cancers. Progress has been made in treatment of HCC; however, improved outcomes are much needed. The increased metabolic needs of cancer cells underscore the importance of metabolic pathways in cancer cell survival. Lipid metabolism has a role in HCC development; aberrant overexpression of several key enzymes is seen in many solid human tumors. Areas covered: We discuss aberrant lipid metabolism and the promise of multiple targets, in particular related to HCC treatment. We searched PubMed and clinicaltrials.gov for published and unpublished studies from 2000 to 2019. These terms were used: lipids, fatty acid metabolism, lipid metabolism, liver cancer, HCC, de novo fatty acid synthesis, ATP citrate lyase, stearoyl CoA denaturase, fatty acid synthase, acetyl coenzyme A carboxylase, CD147, KLF4, monoglyceride lipase, AMP activated protein kinase. Expert opinion: The importance of dysregulation of fatty acid synthesis in cancer is a growing area of research. HCC demonstrates significant alteration in lipid metabolism, representing great potential as a target for novel therapeutics. Various agents have demonstrated promising anti-neoplastic activity. This strategy deserves further development for improved outcomes.

In utero arsenic exposure in mice and early life susceptibility to cancer

In its review of the U.S. Environmental Protection Agency's toxicological review of inorganic arsenic (iAs), the National Academy of Sciences identified carcinogenic endpoints among the highest priority health effects of concern and stated the need to consider evidence that early life exposures may increase the risk of adverse health effects. Recent studies in mice suggest that in utero exposure to arsenic increases susceptibility to cancer later in life. These data are striking in light of the general lack of evidence for carcinogenicity in rodents exposed to iAs. To evaluate the transplacental carcinogenic potential of iAs, a detailed analysis of the toxicology literature evaluating the role of in utero arsenic exposure in carcinogenesis was conducted. Bladder, lung, and skin tumors, which are the tumor types most consistently reported in humans exposed to high arsenic levels, were not consistently increased in mouse studies. There was also a lack of concordance across studies for other tumor types not typically reported in humans. Therefore, we considered methodological and other critical issues that may have contributed to variable results and we suggest additional studies to address these issues. It was concluded that the available data do not provide evidence of a causal link between in utero arsenic exposure and cancer or indicate early life-stage susceptibility to arsenic-induced cancer, particularly at environmentally relevant doses.

Developmental exposure to 50 parts-per-billion arsenic influences histone modifications and associated epigenetic machinery in a region- and sex-specific manner in the adult mouse brain

Epidemiological studies report that arsenic exposure via drinking water adversely impacts cognitive development in children and, in adults, can lead to greater psychiatric disease susceptibility, among other conditions. While it is known that arsenic toxicity has a profound effect on the epigenetic landscape, very few studies have investigated its effects on chromatin architecture in the brain. We have previously demonstrated that exposure to a low level of arsenic (50ppb) during all three trimesters of fetal/neonatal development induces deficits in adult hippocampal neurogenesis in the dentate gyrus (DG), depressive-like symptoms, and alterations in gene expression in the adult mouse brain. As epigenetic processes control these outcomes, here we assess the impact of our developmental arsenic exposure (DAE) paradigm on global histone posttranslational modifications and associated chromatin-modifying proteins in the dentate gyrus and frontal cortex (FC) of adult male and female mice. DAE influenced histone 3K4 trimethylation with increased levels in the male DG and FC and decreased levels in the female DG (no change in female FC). The histone methyltransferase MLL exhibited a similar sex- and region-specific expression profile as H3K4me3 levels, while histone demethylase KDM5B expression trended in the opposite direction. DAE increased histone 3K9 acetylation levels in the male DG along with histone acetyltransferase (HAT) expression of GCN5 and decreased H3K9ac levels in the male FC along with decreased HAT expression of GCN5 and PCAF. DAE decreased expression of histone deacetylase enzymes HDAC1 and HDAC2, which were concurrent with increased H3K9ac levels but only in the female DG. Levels of H3 and H3K9me3 were not influenced by DAE in either brain region of either sex. These findings suggest that exposure to a low, environmentally relevant level of arsenic during development leads to long-lasting changes in histone methylation and acetylation in the adult brain due to aberrant expression of epigenetic machinery based on region and sex.

Carcinogenic effects of "whole-life" exposure to inorganic arsenic in CD1 mice

In a previously developed mouse model, arsenic exposure in utero induces tumors at multiple sites in the offspring as adults, often duplicating human targets. However, human environmental inorganic arsenic exposure occurs during the entire life span, not just part of gestation. Thus, "whole-life" inorganic arsenic carcinogenesis in mice was studied. CD1 mice were exposed to 0, 6, 12, or 24 ppm arsenic in the drinking water 2 weeks prior to breeding, during pregnancy, lactation, and after weaning through adulthood. Tumors were assessed in offspring until 2 years of age. Arsenic induced dose-related increases in lung adenocarcinoma (both sexes), hepatocellular carcinoma (both sexes), gallbladder tumors (males), and uterine carcinomas. Arsenic induced dose-related increases in ovarian tumors (including carcinomas) starting with the lowest dose. Adrenal tumors increased at all doses (both sexes). Arsenic-induced lung and liver cancers were highly enriched for cancer stem cells, consistent with prior work with skin cancers stimulated by prenatal arsenic. Reproductive tract tumors overexpressed cyclooxygenase-2 and estrogen receptor-α. Arsenic target sites were remarkably similar to prior transplacental studies, although tumors from whole-life exposure were generally more aggressive and frequent. This may indicate that arsenic-induced events in utero dictate target site in some tissues, whereas other exposure periods of arsenic enhance incidence or progression, though other factors could be at play, like cumulative dose. Whole-life arsenic exposure induced tumors at dramatically lower external doses than in utero arsenic only while more realistically duplicating human exposure.

Oxygenomics in environmental stress

Environmental stressors such as chemicals and physical agents induce various oxidative stresses and affect human health. To elucidate their underlying mechanisms, etiology and risk, analyses of gene expression signatures in environmental stress-induced human diseases, including neuronal disorders, cancer and diabetes, are crucially important. Recent studies have clarified oxidative stress-induced signaling pathways in human and experimental animals. These pathways are classifiable into several categories: reactive oxygen species (ROS) metabolism and antioxidant defenses, p53 pathway signaling, nitric oxide (NO) signaling pathway, hypoxia signaling, transforming growth factor (TGF)-beta bone morphogenetic protein (BMP) signaling, tumor necrosis factor (TNF) ligand-receptor signaling, and mitochondrial function. This review describes the gene expression signatures through which environmental stressors induce oxidative stress and regulate signal transduction pathways in rodent and human tissues.