Using the human CYP26A1 gene promoter as a suitable tool for the determination of RAR-mediated retinoid activity

Zolfaghari, Reza; Mattie, Floyd J.; Wei, Cheng; Chisholm, David; Whiting, Andrew; Ross, A. Catharine

doi:10.1016/bs.mie.2020.03.013

Cited by 2 publications

(4 citation statements)

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“…Cyp26a1 is a hydrolase of atRA, and an increase in atRA levels results in a positive feedback loop that enhances Cyp26a1 expression 67–69 . In the liver and other tissues, atRA‐induced CYP26A1 enzyme metabolism atRA to 4‐hydroxyl‐RA 70 .…”

Section: Resultsmentioning

confidence: 99%

“…Cyp26a1 is a hydrolase of atRA, and an increase in atRA levels results in a positive feedback loop that enhances Cyp26a1 expression. [67][68][69] In the liver and other tissues, atRA-induced CYP26A1 enzyme metabolism atRA to 4hydroxyl-RA. 70 To determine whether Cyp26a1 expression was induced or prevented through the changes caused by atRA during hepatocarcinogenesis in Fah −/− mice, we analysed Cyp26a1 in the livers of Fah −/− mice after the induction of CLI for up to 12 weeks (named C12) or after induction of CLI plus atRA treatment for up to 12 weeks (named atRA 12).…”

Section: 5mentioning

confidence: 99%

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Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8⁺ T cells

He,

Wang,

Chen

et al. 2023

Clinical & Translational Med

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BackgroundHepatocellular carcinoma (HCC) is a highly heterogeneous cancer with major challenges in both prevention and therapy. Metformin, adenosine monophosphate‐activated protein kinase (AMPK) activator, has been suggested to reduce the incidence of HCC when used for patients with diabetes in preclinical and clinical studies. However, the possible effects of metformin and their mechanisms of action in non‐diabetic HCC have not been adequately investigated.MethodsFah−/− mice were used to construct a liver‐injury‐induced non‐diabetic HCC model for exploring hepatocarcinogenesis and therapeutic potential of metformin. Changes in relevant tumour and biochemical indicators were measured. Bulk and single‐cell RNA‐sequencing analyses were performed to validate the crucial role of proinflammatory/pro‐tumour CD8+ T cells. In vitro and in vivo experiments were performed to confirm Cyp26a1‐related antitumour mechanisms of metformin.ResultsRNA‐sequencing analysis showed that chronic liver injury led to significant changes in AMPK‐, glucose‐ and retinol metabolism‐related pathways in Fah−/− mice. Metformin prevented the formation of non‐diabetic HCC in Fah−/− mice with chronic liver injury. Cyp26a1 ddexpression in hepatocytes was significantly suppressed after metformin treatment. Moreover, downregulation of Cyp26a1 occurred in conjunction with increased levels of all‐trans‐retinoic acid (atRA), which is involved in the activation of metformin‐suppressed hepatocarcinogenesis in Fah−/− mice. In contrast, both CD8+ T‐cell infiltration and proinflammatory/pro‐tumour cytokines in the liver were significantly upregulated in Fah−/− mice during chronic liver injury, which was notably reversed by either metformin or atRA treatment. Regarding mechanisms, metformin regulated the decrease in Cyp26a1 enzyme expression and increased atRA expression via the AMPK/STAT3/Gadd45β/JNK/c‐Jun pathway.ConclusionsMetformin inhibits non‐diabetic HCC by upregulating atRA levels and downregulating CD8+ T cells. This is the first reporting that the traditional drug metformin regulates the metabolite atRA via the Cyp26a1‐involved pathway. The present study provides a potential application of metformin and atRA in non‐diabetic HCC.

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Section: Resultsmentioning

confidence: 99%

Section: 5mentioning

confidence: 99%

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8⁺ T cells

He,

Wang,

Chen

et al. 2023

Clinical & Translational Med

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“…Having shown that HepG2 cells could be an appropriate model to analyze the function of hepatic RAR genes in response to RA, we tested whether HNF4α could act on the promoter of the RARB gene. For this, we used a cloned fragment of the human RARβ gene spanning from −1.7 kbp from TSS to +0.217 kpb of the 5'UTR region [33,34] as the driving promoter on a pGL3-Basic-luc vector used as the reporter gene. HepG2 cells were co-transfected with the RARβ promoter construct and the pRLTK plasmid together with either human HNF4α, the combination of RARα and RXRα (referred to below as RARα/RXRα), or all three transcription factors, for 24 h, after which the cells were treated further with either the vehicle or RA for 1 to 24 h prior to measurement of the luciferase activity.…”

Section: Hnf4α Response Element(s) May Reside Within the Rare Sites I...mentioning

confidence: 99%

“…Construction of the plasmid vectors including pGL3-Basic-hCYP26A1-E4-luc (submitted to addgene.org), pGL3-Basic-hRARβp-luc (human RARβ2 promoter), pGL3-Basic-hCYP2C9p-luc, pcDNNA3.1-hRARα.hRXRα (submitted to addgene.org), and pcDNA3.1-hHNF4α were reported previously [18,20,33,34,43]. The full-length HNF4α mutants were constructed by PCR-mediated mutagenesis, using appropriate primers (Table 2) and the WT human HNF4α cDNA as the template.…”

Section: Cloning and Preparation Of Vector Constructsmentioning

confidence: 99%

Hepatocyte Nuclear Factor 4α (HNF4α) Plays a Controlling Role in Expression of the Retinoic Acid Receptor β (RARβ) Gene in Hepatocytes

Zolfaghari

Bonzo

Gonzalez

et al. 2023

IJMS

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HNF4α, a member of the nuclear receptor superfamily, regulates the genes involved in lipid and glucose metabolism. The expression of the RARβ gene in the liver of HNF4α knock-out mice was higher versus wildtype controls, whereas oppositely, RARβ promoter activity was 50% reduced by the overexpression of HNF4α in HepG2 cells, and treatment with retinoic acid (RA), a major metabolite of vitamin A, increased RARβ promoter activity 15-fold. The human RARβ2 promoter contains two DR5 and one DR8 binding motifs, as RA response elements (RARE) proximal to the transcription start site. While DR5 RARE1 was previously reported to be responsive to RARs but not to other nuclear receptors, we show here that mutation in DR5 RARE2 suppresses the promoter response to HNF4α and RARα/RXRα. Mutational analysis of ligand-binding pocket amino acids shown to be critical for fatty acid (FA) binding indicated that RA may interfere with interactions of FA carboxylic acid headgroups with side chains of S190 and R235, and the aliphatic group with I355. These results could explain the partial suppression of HNF4α transcriptional activation toward gene promoters that lack RARE, including APOC3 and CYP2C9, while conversely, HNF4α may bind to RARE sequences in the promoter of the genes such as CYP26A1 and RARα, activating these genes in the presence of RA. Thus, RA could act as either an antagonist towards HNF4α in genes lacking RAREs, or as an agonist for RARE-containing genes. Overall, RA may interfere with the function of HNF4α and deregulate HNF4α targets genes, including the genes important for lipid and glucose metabolism.

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Using the human CYP26A1 gene promoter as a suitable tool for the determination of RAR-mediated retinoid activity

Cited by 2 publications

References 17 publications

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8⁺ T cells

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8⁺ T cells

Hepatocyte Nuclear Factor 4α (HNF4α) Plays a Controlling Role in Expression of the Retinoic Acid Receptor β (RARβ) Gene in Hepatocytes

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Using the human CYP26A1 gene promoter as a suitable tool for the determination of RAR-mediated retinoid activity

Cited by 2 publications

References 17 publications

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8+ T cells

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8+ T cells

Hepatocyte Nuclear Factor 4α (HNF4α) Plays a Controlling Role in Expression of the Retinoic Acid Receptor β (RARβ) Gene in Hepatocytes

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Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8⁺ T cells

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8⁺ T cells