Global gene expression changes including drug metabolism and disposition induced by three-dimensional culture of HepG2 cells-Involvement of microtubules

The Regulation Pathway of VEGF Gene Expression Is Different between 2D Cells and 3D Spheroids in Human Lung Cancer Cells

Angiogenesis is involved in the malignant transformation of cancers. Vascular endothelial growth factor (VEGF) is important in inducing angiogenesis. Cultured cells play an important role in analyzing the regulation of VEGF expression, and it is revealed that VEGF expression is induced under hypoxia. However, it has been shown that there are differences in the pathway for gene expression between two-dimensional (2D) cells and in vivo cells. Three-dimensional (3D) spheroids constructed in 3D culture with a gene expression pattern more similar to that of in vivo cells than 2D cells have been used to solve this problem. This study analyzed the VEGF gene expression pathway in 3D spheroids of human lung cancer cells, A549 and H1703. Hypoxia-inducible factor-1α (HIF-1α) and aryl hydrocarbon receptor nuclear translocator (ARNT) regulated VEGF gene expression in 3D spheroids. However, VEGF gene expression was not regulated by HIF-1α in 2D cells. To conclude, we found that the regulatory pathway of VEGF gene expression is different between 2D cells and 3D spheroids in human lung cancer cells. These results suggest the possibility of a new VEGF gene expression regulation pathway in vivo. In addition, they show useful knowledge for the analysis of angiogenesis induction mechanisms and also demonstrate the usefulness of 3D spheroids.

[Modulation of Expression of Drug Metabolizing Enzymes and Augmentation of Anti-cancer Drug Effects: Through Epigenetics and Three-dimensional Cancer Cell Culture Systems]

Since commencing my role as a professor in a newly established Department of Pharmacodynamics and Molecular Genetics at the School of Pharmacy, Iwate Medical University, on April 1, 2007, my research has focused on modifying gene expression of cytochrome P-450 (CYP) in established human colon cancer cells. Additionally, I have been investigating methods to enhance the anti-tumor effects of irinotecan (CPT-11) and 5-fluorouracil (5-FU) using epigenetic modifying inhibitors of DNA methyltransferase and histone deacetylase. Treating colon cancer cells with a DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (DAC), led to elevated expression levels of CYP1B1 and CYP3A4 through demethylation of the promoter regions of related genes. Furthermore, the administration of DAC and the histone deacetylase inhibitor depsipeptide [(DEP), an anti-cancer drug romidepsin] significantly increased the cellular sensitivities of human colon cancer cells to CPT-11 and 5-FU, respectively. Remarkably, DAC treatment also increased colon cancer cell sensitivity to SN-38, an active metabolite of CPT-11, through the suppression of the anti-apoptotic protein Bcl-2. DEP increased colon cancer cell sensitivity to 5-FU in association with increased expressions of tumor-suppressor p21 and major histocompatibility complex class II genes. Another facet of my research is centered around understanding the gene regulatory mechanisms of the CYP1 family through aryl hydrocarbon receptors (AhR)s under glucose-deprivation stress and in three-dimensional (3D) culture systems of human solid tumor cells. In the 3D culture of human liver cancer cells, I found Pregnane X Receptor being implicated in the regulation of CYP1A2, which aligns with the in vivo mode of CYP1A2 expression.

Transcriptional and Epigenetic Consequences of DMSO Treatment on HepaRG Cells

Dimethyl sulfoxide (DMSO) is used to sustain or favor hepatocyte differentiation in vitro. Thus, DMSO is used in the differentiation protocol of the HepaRG cells that present the closest drug-metabolizing enzyme activities to primary human hepatocytes in culture. The aim of our study is to clarify its influence on liver-specific gene expression. For that purpose, we performed a large-scale analysis (gene expression and histone modification) to determine the global role of DMSO exposure during the differentiation process of the HepaRG cells. The addition of DMSO drives the upregulation of genes mainly regulated by PXR and PPARα whereas genes not affected by this addition are regulated by HNF1α, HNF4α, and PPARα. DMSO-differentiated-HepaRG cells show a differential expression for genes regulated by histone acetylation, while differentiated-HepaRG cells without DMSO show gene signatures associated with histone deacetylases. In addition, we observed an interplay between cytoskeleton organization and EMC remodeling with hepatocyte maturation.

Sexual Dimorphism in Drug Metabolism and Pharmacokinetics

Background:

Sex and gender-based differences are observed well beyond the sex organs and affect several physiological and biochemical processes involved in the metabolism of drug molecules. It is essential to understand not only the sex and gender-based differences in the metabolism of the drug but also the molecular mechanisms involved in the regulation of drug metabolism for avoiding sex-related adverse effects of drugs in the human.

Method:

The articles on the sex and gender-based differences in the metabolism of drug molecules were retrieved from the Pub Med database. The articles were classified into the metabolism of the drug molecule, gene expression regulation of drug-metabolizing enzymes, the effect of sex hormones on the metabolism of drug, expression of drugmetabolizing enzymes, etc.

Result:

Several drug molecules are known, which are metabolized differently in males and females. These differences in metabolism may be due to the genomic and non-genomic action of sex hormones. Several other drug molecules still require further evaluation at the molecular level regarding the sex and gender-based differences in their metabolism. Attention is also required at the effect of signaling cascades associated with the metabolism of drug molecules.

Conclusion:

Sex and gender-based differences in the metabolism of drugs exist at various levels and it may be due to the genomic and non-genomic action of sex hormones. Detailed understanding of the effect of sex and related condition on the metabolism of drug molecules will help clinicians to determine the effective therapeutic doses of drugs dependingon the condition of patient and disease.

Indirect activation of constitutive androstane receptor in three-dimensionally cultured HepG2 cells

Constitutive androstane receptor (CAR), a member of the nuclear receptor superfamily, is retained as an inactive form phosphorylated at threonine in the cytoplasm of hepatocytes. Upon activation, CAR is dephosphorylated to move into the nucleus and induces the transcription of genes. Thus, nuclear translocation is a key step for CAR activation in hepatocytes. However, this nuclear translocation has not been demonstrated in conventional two-dimensionally-cultured immortalized cell lines such as HepG2, in which CAR spontaneously accumulates in the nucleus. In this study, we showed that treatment with the indirect CAR activator phenobarbital activated transcription of the CYP3A4 gene in three-dimensionally (3D)-cultured HepG2 cells. CAR was retained as its phosphorylated form in the cytoplasm and was translocated to the nucleus in 3D-cultured HepG2 cells in response to treatment with phenobarbital. Moreover, okadaic acid and epidermal growth factor, were found to repress phenobarbital-induced CAR nuclear translocation and subsequent activation of the CYP3A4 gene promoter. These results suggested that 3D-cultured HepG2 cells properly regulated CAR activation as has been observed in hepatocytes.

Modes of Cell Death Induced by Photodynamic Therapy Using Zinc Phthalocyanine in Lung Cancer Cells Grown as a Monolayer and Three-Dimensional Multicellular Spheroids

Photodynamic therapy (PDT) involves interaction of a photosensitizer, light, and molecular oxygen which produces singlet oxygen and subsequent tumour eradication. The development of second generation photosensitizers, such as phthalocyanines, has improved this technology. Customary monolayer cell culture techniques are, unfortunately, too simple to replicate treatment effects in vivo. Multicellular tumour spheroids may provide a better alternative since they mimic aspects of the human tumour environment. This study aimed to profile 84 genes involved in apoptosis following treatment with PDT on lung cancer cells (A549) grown in a monolayer versus three-dimensional multicellular tumour spheroids (250 and 500 μm). Gene expression profiling was performed 24 h post irradiation (680 nm; 5 J/cm²) with zinc sulfophthalocyanine (ZnPcSmix) to determine the genes involved in apoptotic cell death. In the monolayer cells, eight pro-apoptotic genes were upregulated, and two were downregulated. In the multicellular tumour spheroids (250 µm) there was upregulation of only 1 gene while there was downregulation of 56 genes. Apoptosis in the monolayer cultured cells was induced via both the intrinsic and extrinsic apoptotic pathways. However, in the multicellular tumour spheroids (250 and 500 µm) the apoptotic pathway that was followed was not conclusive.

Upregulations of metallothionein gene expressions and tolerance to heavy metal toxicity by three dimensional cultivation of HepG2 cells on VECELL 3-D inserts

The VECELL 3-D insert is a new culture scaffold consisting of collagen-coated ePTFE (expanded polytetrafluoroethylene) mesh. We analyzed the effects of VECELL 3-D inserts on the functionality of HepG2, a human hepatocellular carcinoma cell line. HepG2 cells cultured on VECELL 3-D inserts maintained a round shape, while those cultured on a standard culture plate or collagen-coated cell culture plate showed a flattened and cubic epithelial-like shape. HepG2 cells cultured on VECELL 3-D inserts had showed upregulated expression of metallothionein genes and in turn a higher tolerance to toxicity induced by heavy metals. These results suggest that HepG2 cell functions were changed by the cell morphology that is induced by culturing on a VECELL 3-D insert.

A three-dimensional collagen-sponge-based culture system coated with simplified recombinant fibronectin improves the function of a hepatocyte cell line

Hepatocytes are widely used in pharmaceutical drug discovery tests, but their hepatic functions decrease rapidly during in vitro culture. Many culture systems have been devised to address this problem. We here report that a three-dimensional (3D) collagen-based scaffold coated with simplified recombinant fibronectin (FN) enhanced the function of a hepatocyte cell line. The developed culture system uses a honeycomb collagen sponge coated with collagen-binding domain (CBD)-cell attachment site (CAS), a chimeric protein comprising the CBD and CAS of FN. The function of HepG2 cells grown on honeycomb collagen sponge coated with CBD-CAS was investigated by determining the messenger RNA (mRNA) expression levels of several genes. The mRNA expression level of albumin increased 3.25 times in cells grown on CBD-CAS-coated honeycomb collagen sponge for 3 days; the expression level of CCAAT/enhancer binding protein (C/EBPα) increased 40-fold after 1 d and up to 150-fold after 3 d. These results suggested that CBD-CAS-coated honeycomb collagen sponge could improve the functions of hepatocytes by inducing C/EBPα expression. The activation of cytochrome P450 (CYP) enzymes in HepG2 cells grown on CBD-CAS-coated honeycomb collagen sponge was measured at the mRNA level and was found to increase between two and six times compared to cells grown without the CBD-CAS coating, showing that this culture system induced CYP gene expression and thus may be useful in drug metabolism assays.

Poly(vinyl alcohol)/gelatin Hydrogels Cultured with HepG2 Cells as a 3D Model of Hepatocellular Carcinoma: A Morphological Study

It has been demonstrated that three-dimensional (3D) cell culture models represent fundamental tools for the comprehension of cellular phenomena both for normal and cancerous tissues. Indeed, the microenvironment affects the cellular behavior as well as the response to drugs. In this study, we performed a morphological analysis on a hepatocarcinoma cell line, HepG2, grown for 24 days inside a bioartificial hydrogel composed of poly(vinyl alcohol) (PVA) and gelatin (G) to model a hepatocellular carcinoma (HCC) in 3D. Morphological features of PVA/G hydrogels were investigated, resulting to mimic the trabecular structure of liver parenchyma. A histologic analysis comparing the 3D models with HepG2 cell monolayers and tumor specimens was performed. In the 3D setting, HepG2 cells were viable and formed large cellular aggregates showing different morphotypes with zonal distribution. Furthermore, β-actin and α5β1 integrin revealed a morphotype-related expression; in particular, the frontline cells were characterized by a strong immunopositivity on a side border of their membrane, thus suggesting the formation of lamellipodia-like structures apt for migration. Based on these results, we propose PVA/G hydrogels as valuable substrates to develop a long term 3D HCC model that can be used to investigate important aspects of tumor biology related to migration phenomena.

Cellular signalling pathways in immune aging and regeneration

The thymus is one of the cornerstones of an effective immune system. It produces new T-cells for the naïve T-cell pool, thus refreshing the peripheral repertoire. As we age, the thymus atrophies and there is a decrease in the area of active T-cell production. A decline in the output of the thymus eventually leads to changes in the peripheral T-cell pool which includes increases in the number of cells at or near their replicative limit and contraction of the repertoire. Debate about the age-associated changes in the thymus leading to functional decline centres on whether this is due to problems with the environment provided by the thymus or with defects in the progenitor cell compartment. In mice, the evidence points towards problems in the epithelial component of the thymus and the production of IL-7 (interleukin 7). But there are discussions about how appropriate mouse models are for human aging. We have developed a simple system that utilizes both human keratinocyte and fibroblast cell lines arrayed on a synthetic tantalum-coated matrix to provide a permissive environment for the maturation of human CD34+ haemopoietic progenitor cells into mature CD4+ or CD8+ T-lymphocytes. We have characterized the requirements for differentiation within these cultures and used this system to compare the ability of CD34+ cells derived from different sources to produce mature thymocytes. The TREC (T-cell receptor excision circle) assay was used as a means of identifying newly produced thymocytes.

Influence of a three-dimensional, microarray environment on human cell culture in drug screening systems

We have used a modified 3D cellular microarray platform for the high-throughput analysis of growth, cytotoxicity, and protein expression profile of a human hepatocellular carcinoma cell line, HepG2, in alginate. The results obtained were compared to analogous studies in 2D and 3D environments at the microtiter scale. The antiproliferative effects of four drugs, tamoxifen, 5-fluorouracil, doxorubicin, and amitriptyline, were studied as a function of seeding density in the three different culture platforms. The chemosensitivity of HepG2 cells to all four compounds decreased substantially with increasing cell number in the 2D and 3D microtiter-based cultures, while no seeding density dependence was observed in the IC(50) values obtained in the 3D microarray culture platform. These results can be rationalized based on the development of confluence-dependent resistance in cultures where proliferation is restricted by cell-cell contacts and nutrient availability, as is the case for both of the microtiter-based cultures. Additionally, further development of an on-chip, in-cell immunofluorescence assay provided quantitative data on the levels of specific target proteins involved in proliferation, adhesion, angiogenesis and drug metabolism, and was used to compare expression profiles between 2D and 3D environments. The up-regulation of several CYP450 enzymes, β1-integrin and vascular endothelial growth factor (VEGF) in the 3D microarray cultures suggests that this platform provides a more in vivo-like environment allowing cells to approach their natural phenotype.