Belinostat, at Its Clinically Relevant Concentrations, Inhibits Rifampicin-Induced CYP3A4 and MDR1 Gene Expression

Histone deacetylase inhibitor belinostat regulates metabolic reprogramming in killing KRAS-mutant human lung cancer cells

Kirsten rat sarcoma virus (KRAS) oncogene, found in 20%-25% of lung cancer patients, potentially regulates metabolic reprogramming and redox status during tumorigenesis. Histone deacetylase (HDAC) inhibitors have been investigated for treating KRAS-mutant lung cancer. In the current study, we investigate the effect of HDAC inhibitor (HDACi) belinostat at clinically relevant concentration on nuclear factor erythroid 2-related factor 2 (NRF2) and mitochondrial metabolism for the treatment of KRAS-mutant human lung cancer. LC-MS metabolomic study of belinostat on mitochondrial metabolism was performed in G12C KRAS-mutant H358 non-small cell lung cancer cells. Furthermore, l-methionine (methyl-13 C) isotope tracer was used to explore the effect of belinostat on one-carbon metabolism. Bioinformatic analyses of metabolomic data were performed to identify the pattern of significantly regulated metabolites. To study the effect of belinostat on redox signaling ARE-NRF2 pathway, luciferase reporter activity assay was done in stably transfected HepG2-C8 cells (containing pARE-TI-luciferase construct), followed by qPCR analysis of NRF2 and its target gene in H358 cells, which was further confirmed in G12S KRAS-mutant A549 cells. Metabolomic study reveals significantly altered metabolites related to redox homeostasis, including tricarboxylic acid (TCA) cycle metabolites (citrate, aconitate, fumarate, malate, and α-ketoglutarate); urea cycle metabolites (Arginine, ornithine, argino-succinate, aspartate, and fumarate); and antioxidative glutathione metabolism pathway (GSH/GSSG and NAD/NADH ratio) after belinostat treatment. 13 C stable isotope labeling data indicates potential role of belinostat in creatine biosynthesis via methylation of guanidinoacetate. Moreover, belinostat downregulated the expression of NRF2 and its target gene NAD(P)H:quinone oxidoreductase 1 (NQO1), indicating anticancer effect of belinostat is mediated, potentially via Nrf2-regulated glutathione pathway. Another HDACi panobinostat also showed potential anticancer effect in both H358 and A549 cells via Nrf2 pathway. In summary, belinostat is effective in killing KRAS-mutant human lung cancer cells by regulating mitochondrial metabolism which could be used as biomarkers for preclinical and clinical studies.

Gefitinib Inhibits Rifampicin-Induced CYP3A4 Gene Expression in Human Hepatocytes

During multidrug combination chemotherapy, activation of the nuclear receptor and the transcription factor human pregnane xenobiotic receptor (hPXR) has been shown to play a role in the development of chemoresistance. Mechanistically, this could occur due to the cancer drug activation of hPXR and the subsequent upregulation of hPXR target genes such as the drug metabolism enzyme, cytochrome P450 3A4 (CYP3A4). In the context of hPXR-mediated drug resistance, hPXR antagonists would be useful adjuncts to PXR-activating chemotherapy. However, there are currently no clinically approved hPXR antagonists in the market. Gefitinib (GEF), a tyrosine kinase inhibitor used for the treatment of advanced non-small-cell lung cancer and effectively used in combinational chemotherapy treatments, is a promising candidate owing to its hPXR ligand-like features. We, therefore, investigated whether GEF would act as an hPXR antagonist when combined with a known hPXR agonist, rifampicin (RIF). At therapeutically relevant concentrations, GEF successfully inhibited the RIF-induced upregulation of endogenous CYP3A4 gene expression in human primary hepatocytes and human hepatocells. Additionally, GEF inhibited the RIF induction of hPXR-mediated CYP3A4 promoter activity in HepG2 human liver carcinoma cells. The computational modeling of molecular docking predicted that GEF could bind to multiple sites on hPXR including the ligand-binding pocket, allowing for potential as a direct antagonist as well as an allosteric inhibitor. Indeed, GEF bound to the ligand-binding domain of the hPXR in cell-free assays, suggesting that GEF directly interacts with the hPXR. Taken together, our results suggest that GEF, at its clinically relevant therapeutic concentration, can antagonize the hPXR agonist-induced CYP3A4 gene expression in human hepatocytes. Thus, GEF could be a potential candidate for use in combinational chemotherapies to combat hPXR agonist-induced chemoresistance. Further studies are warranted to determine whether GEF has sufficient hPXR inhibitor abilities to overcome the hPXR agonist-induced chemoresistance.

Allosteric Antagonism of the Pregnane X Receptor (PXR): Current-State-of-the-Art and Prediction of Novel Allosteric Sites

The pregnane X receptor (PXR, NR1I2) is a xenobiotic-activated transcription factor with high levels of expression in the liver. It not only plays a key role in drug metabolism and elimination, but also promotes tumor growth, drug resistance, and metabolic diseases. It has been proposed as a therapeutic target for type II diabetes, metabolic syndrome, and inflammatory bowel disease, and PXR antagonists have recently been considered as a therapy for colon cancer. There are currently no PXR antagonists that can be used in a clinical setting. Nevertheless, due to the large and complex ligand-binding pocket (LBP) of the PXR, it is challenging to discover PXR antagonists at the orthosteric site. Alternative ligand binding sites of the PXR have also been proposed and are currently being studied. Recently, the AF-2 allosteric binding site of the PXR has been identified, with several compounds modulating the site discovered. Herein, we aimed to summarize our current knowledge of allosteric modulation of the PXR as well as our attempt to unlock novel allosteric sites. We describe the novel binding function 3 (BF-3) site of PXR, which is also common for other nuclear receptors. In addition, we also mention a novel allosteric site III based on in silico prediction. The identified allosteric sites of the PXR provide new insights into the development of safe and efficient allosteric modulators of the PXR receptor. We therefore propose that novel PXR allosteric sites might be promising targets for treating chronic metabolic diseases and some cancers.

Imatinib-induced hepatotoxicity via oxidative stress and activation of NLRP3 inflammasome: an in vitro and in vivo study

Imatinib (IM), a milestone drug used in the field of molecular targeted therapy, has been reported to cause serious adverse liver effects, including liver failure and even death. Immune-mediated injury and mitochondrial dysfunction are involved in drug-induced liver injury. However, the mechanism of IM-induced hepatotoxicity remains unclear and warrants further study. In our study, Sprague Dawley rats were administered IM by gavage with 50 mg/kg body weight (BW) once daily for 10 days. Drug-induced liver injury accompanied by inflammatory infiltration was observed in rats following IM exposure, and the expression of NOD-like receptor protein 3 (NLRP3) inflammasome-related proteins was significantly increased compared with that of the control. HepG2 cells were exposed to 0-100 μM IM for 24 h. The results showed that IM decreased cell viability in a dose-dependent manner. Moreover, IM induced a state of obvious oxidative stress and activation of nuclear factor kappa B (NF-κB) in cells, which resulted in the activation of NLRP3 inflammasomes, including caspase 1 cleavage and IL-1β release. These results were significantly reduced after the use of the antioxidants N-acetyl-l-cysteine or the NF-κB inhibitor pyrrolidine di-thio-carbamate. Furthermore, NLRP3 knockdown significantly reduced the release of inflammatory cytokines and improved cell viability. In summary, our data demonstrated that oxidative stress and NLRP3 inflammasome activation are involved in the process of IM-induced hepatotoxicity. The results of this study provide a reference for the prevention and treatment of IM-induced hepatotoxicity.

Tumor Microenvironment Alters Chemoresistance of Hepatocellular Carcinoma Through CYP3A4 Metabolic Activity

Variations in tumor biology from patient to patient combined with the low overall survival rate of hepatocellular carcinoma (HCC) present significant clinical challenges. During the progression of chronic liver diseases from inflammation to the development of HCC, microenvironmental properties, including tissue stiffness and oxygen concentration, change over time. This can potentially impact drug metabolism and subsequent therapy response to commonly utilized therapeutics, such as doxorubicin, multi-kinase inhibitors (e.g., sorafenib), and other drugs, including immunotherapies. In this study, we utilized four common HCC cell lines embedded in 3D collagen type-I gels of varying stiffnesses to mimic normal and cirrhotic livers with environmental oxygen regulation to quantify the impact of these microenvironmental factors on HCC chemoresistance. In general, we found that HCC cells with higher baseline levels of cytochrome p450-3A4 (CYP3A4) enzyme expression, HepG2 and C3Asub28, exhibited a cirrhosis-dependent increase in doxorubicin chemoresistance. Under the same conditions, HCC cell lines with lower CYP3A4 expression, HuH-7 and Hep3B2, showed a decrease in doxorubicin chemoresistance in response to an increase in microenvironmental stiffness. This differential therapeutic response was correlated with the regulation of CYP3A4 expression levels under the influence of stiffness and oxygen variation. In all tested HCC cell lines, the addition of sorafenib lowered the required doxorubicin dose to induce significant levels of cell death, demonstrating its potential to help reduce systemic doxorubicin toxicity when used in combination. These results suggest that patient-specific tumor microenvironmental factors, including tissue stiffness, hypoxia, and CYP3A4 activity levels, may need to be considered for more effective use of chemotherapeutics in HCC patients.

Extrahepatic cytochrome P450 epoxygenases: pathophysiology and clinical significance in human gastrointestinal cancers

Cytochrome P450 (CYP) epoxygenases, a multi-gene superfamily of heme-containing enzymes, are commonly known to metabolize endogenous arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs). The role of CYPs is mostly studied in liver drugs metabolism, cardiac pathophysiology, and hypertension fields. Particularly, the biological functions of these enzymes have increasingly attracted a growing interest in cancer biology. Most published studies on CYPs in cancer have been limited to their role as drug metabolizing systems. The activity of these enzymes may affect drug pharmacokinetics and bioavailability as well as exogenous compounds turnover. Some CYP isoforms are selectively highly expressed in tumors, suggesting a potential mechanistic role in promoting resistance to chemotherapy. Majority of drugs elicit their effects in extrahepatic tissues whereby their metabolism can significantly determine treatment outcome. Nonetheless, the role of extrahepatic CYPs is not fully understood and targeting these enzymes as effective anti-cancer therapies are yet to be developed. This review article summarizes an up-to-date body of information from published studies on CYP enzymes expression levels and pathophysiological functions in human normal and malignant gastrointestinal (GI) tract tissues. Specifically, we reviewed and discussed the current research initiatives by emphasizing on the clinical significance and the pathological implication of CYPs in GI malignancies of esophagus, stomach, and colon.

Correlation of PPM1A Downregulation with CYP3A4 Repression in the Tumor Liver Tissue of Hepatocellular Carcinoma Patients

BACKGROUND AND OBJECTIVE

In many patients with hepatocellular carcinoma (HCC), cytochrome P450 3A4 (CYP3A4) expression has been reported to be significantly reduced in the tumor liver tissue. Moreover, this CYP3A4 repression is associated with decreased CYP3A4-mediated drug metabolism in the tumor liver tissue. However, the underlying mechanisms of CYP3A4 repression are not fully understood. We have previously shown that Mg²⁺/Mn²⁺-dependent phosphatase 1A (PPM1A) positively regulates human pregnane X receptor (hPXR)-mediated CYP3A4 expression in a PPM1A expression-dependent manner. We sought to determine whether PPM1A expression is downregulated and whether PPM1A downregulation is correlated with CYP3A4 repression in the tumor liver tissue of HCC patients.

METHODS

Quantitative RT-PCR and western blot analyses were performed to study mRNA and protein expression, respectively. Cell-based reporter gene assays were conducted to examine the hPXR transactivation of CYP3A4 promoter activity.

RESULTS

Arginase-1 and glypican-3 gene expression studies confirmed that the tumor samples used in our study originate from HCC livers but not non-hepatocellular tumors. mRNA and protein expression of PPM1A and CYP3A4 was found to be significantly repressed in the tumor liver tissues compared to the matched non-tumor liver tissues. In the reporter gene assays, elevated PPM1A levels counteracted the inhibition of hPXR-mediated CYP3A4 promoter activity by signaling pathways that are upregulated in HCC, suggesting that decreased PPM1A levels in HCC could not fully counteract the hPXR-inhibiting signaling pathways.

CONCLUSIONS

Together, these results are consistent with the conclusion that PPM1A downregulation in the tumor liver tissue of HCC patients correlates with CYP3A4 repression. Downregulation of PPM1A levels in the tumor liver tissue may contribute to reduced hPXR-mediated CYP3A4 expression, and provide a novel mechanism of CYP3A4 repression in the tumor liver tissue of HCC patients.

Adverse pharmacokinetic interactions between illicit substances and clinical drugs

Adverse pharmacokinetic interactions between illicit substances and clinical drugs are of a significant health concern. Illicit substances are taken by healthy individuals as well as by patients with medical conditions such as mental illnesses, acquired immunodeficiency syndrome, diabetes mellitus and cancer. Many individuals that use illicit substances simultaneously take clinical drugs meant for targeted treatment. This concomitant usage can lead to life-threatening pharmacokinetic interactions between illicit substances and clinical drugs. Optimal levels and activity of drug-metabolizing enzymes and drug-transporters are crucial for metabolism and disposition of illicit substances as well as clinical drugs. However, both illicit substances and clinical drugs can induce changes in the expression and/or activity of drug-metabolizing enzymes and drug-transporters. Consequently, with concomitant usage, illicit substances can adversely influence the therapeutic outcome of coadministered clinical drugs. Likewise, clinical drugs can adversely affect the response of coadministered illicit substances. While the interactions between illicit substances and clinical drugs pose a tremendous health and financial burden, they lack a similar level of attention as drug-drug, food-drug, supplement-drug, herb-drug, disease-drug, or other substance-drug interactions such as alcohol-drug and tobacco-drug interactions. This review highlights the clinical pharmacokinetic interactions between clinical drugs and commonly used illicit substances such as cannabis, cocaine and 3, 4-Methylenedioxymethamphetamine (MDMA). Rigorous efforts are warranted to further understand the underlying mechanisms responsible for these clinical pharmacokinetic interactions. It is also critical to extend the awareness of the life-threatening adverse interactions to both health care professionals and patients.

Screening for CYP3A4 inhibition and induction coupled to parallel artificial membrane permeability assay (PAMPA) for prediction of botanical-drug interactions: The case of açaí and maca

BACKGROUND

The consumption of botanical dietary supplements (BDS) is a common practice among the US population. However, the potential for botanical-drug interactions exists, and their mechanisms have not been thoroughly studied. CYP3A4 is an important enzyme that contributes to the metabolism of about 60% of clinically used drugs.

PURPOSE

To investigate the potential for botanical-drug interactions of Lepidium meyenii Walpers (maca) root and Euterpe oleracea Mart. (açaí) berries, two commonly used BDS, when co-administered with CYP3A4-metabolized drugs.

METHODS

In an attempt to decrease the general discrepancy between in vivo and in vitro studies, the absorption profiles, particularly for passive diffusion, of plant extracts were investigated. Specifically, the parallel artificial membrane permeability assay (PAMPA) model was utilized to simulate intestinal filtration of passively diffused constituents of açaí and maca extracts. These were subsequently screened for in vitro liver CYP3A4 inhibition and induction. In the inhibition assay, midazolam was used as the probe substrate on genotyped human liver microsomes (CYP3A5 null), and the production of its 1'-substituted metabolite when co-cultured with extract treatments was monitored. In the induction assay, extract treatments were applied to human primary hepatocytes, and quantitative PCR analysis was performed to determine CYP3A4 mRNA expression.

RESULTS

Passively diffused constituents of the methanol açaí extract (IC₅₀ of 28.03 µg/µl) demonstrated the highest inhibition potential, and, at 1.5 µg/µl, induced significant changes in CYP3A4 gene expression. The composition of this extract was further investigated using the chemometric tool Mass Profiler Professional (MPP) on liquid chromatography-mass spectroscopy (LC-MS) data. Subsequently, five compounds of interest characterized by high abundance or high permeability were extracted for further study. This included efforts in effective passive permeability determination and structural elucidation by tandem mass spectrometry (MS/MS).

CONCLUSION

The passively absorbable portion of a methanol açaí extract exhibited inhibition and induction effects on CYP3A4 suggesting the potential to produce botanical-drug interactions.