Chlamydomonas reinhardtii, which is a unicellular photosynthetic eukaryote, has long served as a model microalga for fundamental biological research and biotechnological applications. Recently, it has attracted attention as a promising biological resource for the sustainable production of bio-oils and high-value biomolecules. To enhance the biotechnological utility of this species, various genetic engineering tools have been developed in recent years. In this study, the tetracycline repressor (TetR)-based transactivation system, which is widely used in mammalian and other eukaryotic cells, was repurposed to establish a synthetic transcriptional activation system for exogenous gene expression in Chlamydomonas. We first constructed a transient expression-based evaluation platform to screen for transcriptional activation domains (TADs) that are functional in Chlamydomonas. Among the analyzed TADs, VP192 (tandem repeat of 12 copies of the core VP16 domain) had the highest transcriptional activity when fused to either TetR or Gal4 DNA-binding domains. Furthermore, fusion proteins comprising VP192 and either TetR or reverse TetR enabled doxycycline-dependent regulation of transgene expression in a dose-dependent manner. Notably, transcriptional inducibility was maintained even when the tetracycline-responsive element (TRE) was fused to the HSP70A promoter. Combining TetR-VP192 and this synthetic chimeric promoter (TRE-PHSP) yielded transgene expression levels that exceeded those resulting from the strong HSP70A/RbcS2 hybrid promoter by more than 14-fold. These findings suggest that artificial transcription factors and engineered promoters provide a versatile molecular toolkit for regulating exogenous gene expression in Chlamydomonas.

Chitin, the second most abundant biomaterial after cellulose, has attracted attention because of its biocompatibility and environmental friendliness, making it suitable for biomedical applications. This study explores the use of chitin monoliths, which are fabricated via thermally induced phase separation (TIPS), for protein separation in a flow system. The chitin monoliths were prepared by modifying chitin into butyryl chitin (BC) and hydrolyzing it to restore its properties. The monoliths were characterized using various techniques, including FE–SEM, ATR FT–IR, and mercury intrusion porosimetry, which revealed pore structures that were tunable on the basis of the quenching temperature. The monoliths exhibited permeability in a flow system and affinity for lysozyme. The monolith efficiently separated lysozyme from ovalbumin in the flow system, and it was able to separate a mixture of artificial sample and diluted hen egg white. The system’s stability was shown through numerous adsorption/desorption cycles, indicating very effective recovery with negligible capacity loss. This flow system was not prone to leakage and was properly dispersed, representing an improvement over a previous system. This study highlights the potential of chitin monoliths as efficient and sustainable tools for protein separation in continuous flow systems, offering improvements over traditional batch methods. Chitin monoliths were developed as sustainable separation media for continuous-flow protein purification by thermally induced phase separation (TIPS). FE-SEM, ATR-FTIR, and mercury intrusion porosimetry confirmed adjustable pore structures controlled by quenching temperature. The monoliths showed good permeability and selective affinity toward lysozyme, enabling efficient separation of lysozyme from ovalbumin under flow conditions. Reusability was demonstrated through multiple adsorption–desorption cycles with high recovery and negligible capacity loss, highlighting the potential of chitin monoliths for efficient and robust protein purification in continuous systems.

Chicken primordial germ cells (cPGCs) hold great potential for genetic modification and germ cell research in chickens. In this study, we evaluated the cellular characteristics of three cPGC lines: cPGC-1, cPGC-2, and cPGC-3. cPGC-1 and cPGC-2 were derived from male chickens, whereas cPGC-3 was derived from a female chicken. We analyzed and compared cell proliferation rates, marker gene expression, and gonadal colonization abilities. Three different cell culture temperatures were assessed (37 °C, 39 °C, and 41 °C) and proliferation rates were highest for all cPGC lines at 39 °C. Additionally, cPGC-1 demonstrated a higher proliferation rate than cPGC-2. No significant differences were observed between cPGC-1 and cPGC-2 with regard to the expression of germ cell and pluripotency marker genes (Cvh, Dazl, Pou5f3, and Nanog). To assess changes in cellular characteristics before and after genetic modification, we performed a green fluorescent protein (GFP) gene knock-in using the CRISPR/Cas9 system, followed by site-specific integration of the scFv-Fc gene using the Cre-loxP system. Transplantation experiments revealed that cPGC-2/GFP exhibited higher gonadal colonization efficiency than cPGC-1/GFP. This study demonstrates differences in cellular characteristics among established cPGC lines and highlights the impact of genetic modification on cPGC function. Our findings emphasize the importance of selecting appropriate cell lines and optimizing culture conditions based on cPGC traits to achieve efficient and reproducible production of transgenic chickens. These insights will aid in the conservation of poultry genetic resources and the advancement of transgenic chicken production for both research and industrial applications.

Abstract Internal ribosome entry sites (IRESs) enable cap-independent translation but often exhibit low and variable efficiency, limiting their use in synthetic gene circuits. Here, we present a programmable strategy to enhance IRES-dependent translation by recruiting a truncated eIF4G scaffold via engineered RNA-binding protein fusions. A λN–eIF4G fusion selectively increased EMCV IRES-mediated translation without affecting cap-dependent expression, achieving up to 7.7-fold enhancement. Translation output was tunable over a broad dynamic range through effector dosage and linker design, revealing key design parameters for controlling activity. The system functioned across multiple mammalian cell lines and in tricistronic constructs, enabling coordinated regulation of polycistronic expression. Computational modeling was consistent with preferential interaction between λN and the EMCV IRES. These results establish a modular framework for the programmable control of translation, define design principles for RNA-guided translational control, and expand the synthetic biology toolkit for post-transcriptional gene regulation.

Monoclonal antibodies are widely used to treat cancer and autoimmune diseases, and Chinese hamster ovary (CHO) cells are the primary host for their production. Antibodies comprise multiple polypeptide chains and precise and coordinated gene expression is essential to optimize productivity and product quality. Here, we developed a regulated expression system based on artificial transcription factors (aTFs) and applied it to full-length IgG production. Heavy- and light-chain genes were placed under unidirectional or bidirectional TRE promoters, enabling inducible, coordinated expression through aTF coregulation. The optimal vector configuration was identified, and a stable CHO clone (CHO/B-HL) was established and adapted to serum-free suspension culture. In batch culture, temperature downshift from 37°C significantly enhanced antibody production. Deep hypothermic cultivation at 30°C increased specific productivity (>8-fold) compared with standard conditions, reaching 81.3 pg cell−1 d−1. In semi-continuous high-density culture, antibody titers were maintained above 4 g/L for over 30 days in the absence of antibiotic selection, with sustained specific productivity up to 71.4 pg cell−1 d−1. SDS-PAGE analysis supported correct H2L2 assembly of the secreted antibodies. In summary, aTF-driven regulated expression provides a robust, process-compatible strategy for sustained, high-level monoclonal antibody production in CHO cells, offering a viable alternative to conventional constitutive expression systems.

Scalable production of functional hepatocytes remains a major challenge for the development of in vitro liver models. Hepatoma-derived cells are attractive due to their proliferative capacity, but their typically low liver-specific functions limit both clinical and industrial applications. Here, we describe a heat-inducible hepatic cell line (hi-Hep), generated by overexpressing BRCA1-associated protein-1 (BAP1) in the human hepatoma-derived cell line HepG2/8F_HS. A transient heat stimulus (43 °C, 30 min) induced growth arrest and markedly enhanced liver-specific functions, including albumin secretion, ammonia clearance, and cytochrome P450 activity, surpassing those of both HepG2 and HepG2/8F_HS. Exploratory transcriptomic profiling revealed coordinated upregulation of DNA replication and biosynthetic pathways, consistent with a shift toward a metabolically active hepatic phenotype. In three-dimensional culture, hi-Hep organoids embedded in alginate-collagen hydrogels exhibited further enhanced detoxification capacity. These findings suggest that BAP1 overexpression may contribute to the enhancement of hepatic metabolic and detoxification functions in hepatoma-derived cells, supporting the potential utility of hi-Hep as a platform for bioartificial liver systems and drug testing models.

Precise spatial restriction of transgene expression is essential for safe in vivo production of bioactive proteins; however, regulatory elements that confer tissue specificity often span large genomic regions and are incompatible with size-limited viral vectors. Here, we report a compact synthetic promoter-feedback circuit that enables enhanced, oviduct-restricted transgene expression in chickens. By combining a minimal ovalbumin promoter (<200 bp) with a tetracycline-responsive element (TRE)-tTA positive feedback loop, we established a viral vector-compatible expression module that achieves enhanced transcriptional output while preserving tissue specificity. This system was validated in vitro and in genetically modified chickens. As a functional demonstration, chickens expressing transforming growth factor beta 1 (TGF-β1) specifically in egg white were generated. TGF-β1 accumulated predominantly as a presumptive latent/pro-form consisting of the latency-associated peptide (LAP)/pro-domain and the mature TGF-β1 dimer, at a semi-quantitatively estimated level of approximately 110 µg/mL, and remained detectable for over 2 years. Oral administration of TGF-β1-containing egg white significantly attenuated inflammation in a murine DSS-induced colitis model. Together, these findings establish a modular, size-efficient transcriptional enhancement platform that enables robust tissue-restricted expression in vivo. This strategy provides a generalizable framework for overcoming regulatory size constraints in viral vector-mediated gene delivery and expands the potential for producing edible biopharmaceuticals in transgenic livestock.

Genome-modifying enzymes, such as recombinases and CRISPR-associated nucleases, enable targeted gene insertion when delivered transiently to minimize off-target effects. Precise genome engineering requires controlled enzyme activity, as well as efficient donor DNA transfer. Integrase-defective lentiviral vectors (IDLVs) provide a promising platform for transient episomal DNA transfer; however, their integration efficiency depends on complementary genome-targeting strategies. Here, we engineered Cre-loaded IDLVs (Cre-IDLVs) that co-package lentiviral vector genomes together with bioactive Cre recombinase. Cre was inserted into the Gag region of an integrase-defective gag-pol construct, allowing for efficient encapsidation and protease-mediated release during virion maturation without compromising the viral titer. The resulting particles carried donor cassettes flanked by heterospecific loxP sites. When applied to CHO founder cells harboring compatible genomic loxP landing pads, Cre-IDLVs efficiently mediated recombination-mediated cassette exchange, producing the highest number of G418-resistant colonies among the plasmid ratios tested. Genomic PCR and sequencing confirmed precise locus-specific insertion without detectable random integration in the analyzed clones. These findings establish Cre-IDLVs as a streamlined dual-delivery platform that couples transient recombinase activity with episomal donor DNA transfer. This hybrid lentiviral strategy provides a programmable approach for controlled and site-specific genome modification in mammalian cells.

Genomics-based safety and quality evaluation studies are advancing the bioindustry by enhancing various aspects, including viral safety, host cell protein (HCP) control, product heterogeneity control, cellular heterogeneity control, and process reproducibility. High-throughput instruments and genome-scale databases are essential in genomics, with the reference genome sequence being the most critical database. The completeness and accuracy of these genome sequences depend on DNA quality, sequencing instruments, read coverage, and assembly strategies. Significant efforts are being made to perfect genome assembly and continuously improve it. However, the quantitative impact of reference genome sequence accuracy on the safety of biologics is not yet fully understood. In this study, we compared and benchmarked six Chinese hamster genomes, including four newly sequenced genomes derived from Chinese hamster cell lines, from an industrial perspective. We also developed database assembly techniques to enhance the safety of biologics. We recommend using two or more independent reference genomes for viral safety studies. For HCP control, we suggest using protein sequences in which trypsin degradation peptides that overlap with high-risk proteins should be masked and unified. Additionally, we can predict microenvironments using single-cell transcriptome data. In bioengineering processes, any nucleotide samples have potential commercial benefits. ### Competing Interest Statement The authors have patents PCT/JP2024/013385 & PCT/JP2024/017548.

Minicircle DNA vectors (MCs) are gene carriers with favorable characteristics for gene therapy and the production of recombinant cells using animal cells as hosts. Typically, MCs are prepared by inserting target gene fragments as an expression unit into a standard plasmid vector, followed by the removal of bacterial sequences. In this study, we report a method for MC preparation utilizing the Cre-loxP recombination system. By inserting the target gene fragments between two loxP sites introduced into the plasmid vector, the plasmid backbone can be removed through the action of Cre recombinase. We explored optimal reaction conditions for MC generation using Cre. Furthermore, site-specific knock-ins into the CHO cell genome were performed using the remaining loxP sequence in the generated MCs via the Cre-loxP reaction. When MCs were used as gene donors, significant improvements in gene integration efficiency and enhanced gene expression in CHO cells were observed compared with conventional plasmids. The MC preparation and gene knock-in techniques developed in this study are highly useful for CHO cell engineering.

RNA expression analyses can be used to obtain various information from inside cells, such as physical conditions, the chemical environment, and endogenous signals. For detecting RNA, the system regulating intracellular gene expression has the potential for monitoring RNA expression levels in real time within living cells. Synthetic biology provides powerful tools for detecting and analyzing RNA inside cells. Here, we devised an RNA aptamer-mediated gene activation system, RAMGA, to induce RNA-triggered gene expression activation by employing an inducible complex formation strategy grounded in synthetic biology. This methodology connects DNA-binding domains and transactivators through target RNA using RNA-binding domains, including phage coat proteins. MS2 bacteriophage coat protein fused with a transcriptional activator and PP7 bacteriophage coat protein fused with the tetracycline repressor (tetR) can be bridged by target RNA encoding MS2 and PP7 stem-loops, resulting in transcriptional activation. We generated recombinant CHO cells containing an inducible GFP expression module governed by a minimal promoter with a tetR-responsive element. Cells carrying the trigger RNA exhibited robust reporter gene expression, whereas cells lacking it exhibited no expression. GFP expression was upregulated over 200-fold compared with that in cells without a target RNA expression vector. Moreover, this system can detect the expression of mRNA tagged with aptamer tags and modulate reporter gene expression based on the target mRNA level without affecting the expression of the original mRNA-encoding gene. The RNA-triggered gene expression systems developed in this study have potential as a new platform for establishing gene circuits, evaluating endogenous gene expression, and developing novel RNA detectors.

Antibody drugs play a vital role in diagnostics and therapy. However, producing antibodies from mammalian cells is challenging owing to cellular heterogeneity, which can be addressed by applying droplet-based microfluidic platforms for high-throughput screening (HTS). Here, we designed an integrated system based on disulfide-bonded redox-responsive hydrogel beads (redox-HBs), which were prepared through enzymatic hydrogelation, to compartmentalize, screen, select, retrieve, and recover selected Chinese hamster ovary (CHO) cells secreting high levels of antibodies. Moreover, redox-HBs were functionalized with protein G as an antibody-binding module to capture antibodies secreted from encapsulated cells. As proof-of-concept, cells co-producing immunoglobulin G (IgG) as the antibody and green fluorescent protein (GFP) as the reporter molecule, denoted as CHO(IgG/GFP), were encapsulated into functionalized redox-HBs. Additionally, antibody-secreting cells were labeled with protein L-conjugated horseradish peroxidase using a tyramide amplification system, enabling fluorescence staining of the antibody captured inside the beads. Redox-HBs were then applied to fluorescence-activated droplet sorting, and selected redox-HBs were degraded by reducing the disulfide bonds to recover the target cells. The results indicated the potential of the developed HTS platform for selecting a single cell viable for biopharmaceutical production.

Group 4 Dictyostelia, like Dictyostelium discoideum, self-organize into aggregates and fruiting bodies using propagating waves of the chemoattractant cAMP, which are produced by a network containing the adenylate cyclase AcaA, cAMP receptors (Cars) and the extracellular cAMP phosphodiesterase PdsA. Additionally, AcaA and the adenylate cyclases AcrA and AcgA produce secreted cAMP for induction of aggregative and prespore gene expression and intracellular cAMP for PKA activation, with PKA triggering initiation of development and spore and stalk maturation. Non-group 4 species also use secreted cAMP to coordinate post-aggregative morphogenesis and prespore induction but use other attractants to aggregate. To understand how cAMP's role in aggregation evolved, we deleted the acaA, carA and pdsA genes of Polysphondylium violaceum, a sister species to group 4. acaA- fruiting bodies had thinner stalks but otherwise developed normally. Deletion of acrA, which was similarly expressed as acaA, reduced aggregation centre initiation and, as also occurred after D. discoideum acrA deletion, caused spore instability. Double acaA-acrA- mutants failed to form stable aggregates, a defect that was overcome by exposure to the PKA agonist 8Br-cAMP, and therefore likely due to reduced intracellular cAMP. The carA- and pdsA- mutants showed normal aggregation and fruiting body development. Together, the data showed that P. violaceum development does not critically require secreted cAMP, while roles of intracellular cAMP in initiation of development and spore maturation are conserved. Apparently, cell-cell communication underwent major taxon-group specific innovation in Dictyostelia.

With the increasing demand for therapeutic antibodies, CHO cells have become the de facto standard as producer host cells for biopharmaceutical production. High production yields are required for antibody production, and developing a high-titer production system is increasingly crucial. This study was established to develop a high-production system using a synthetic biology approach by designing a gene expression system based on an artificial transcription factor that can strongly induce the high expression of target genes in CHO cells. To demonstrate the functionality of this artificial gene expression system and its ability to induce the high expression of target genes in CHO cells, a model antibody (scFv-Fc) was produced using this system. Excellent results were obtained with the plate scale, and when attempting continuous production in semi-continuous cultures using bioreactor tubes with high-cell-density suspension culture using a serum-free medium, high-titer antibody production at the gram-per-liter level was achieved. Shifting the culture temperature to a low temperature of 33 °C achieved scFv-Fc concentrations of up to 5.5 g/L with a specific production rate of 262 pg/(cell∙day). This artificial gene expression system should be a powerful tool for CHO cell engineering aimed at constructing high-yield production systems.

Background Cyclic di-guanylate (c-di-GMP), synthesized by diguanylate cyclase, is a major second messenger in prokaryotes, where it triggers biofilm formation. The dictyostelid social amoebas acquired diguanylate cyclase (dgcA) by horizontal gene transfer. Dictyostelium discoideum (Ddis) in taxon group 4 uses c-di-GMP as a secreted signal to induce differentiation of stalk cells, the ancestral somatic cell type that supports the propagating spores. We here investigated how this role for c-di-GMP evolved in Dictyostelia by exploring dgcA function in the group 2 species Polysphondylium pallidum (Ppal) and in Polysphondylium violaceum (Pvio), which resides in a small sister clade to group 4. Results Similar to Ddis, dgcA is upregulated after aggregation in Ppal and Pvio and predominantly expressed in the anterior region and stalks of emerging fruiting bodies. DgcA null mutants in Ppal and Pvio made fruiting bodies with very long and thin stalks and only few spores and showed delayed aggregation and larger aggregates, respectively. Ddis dgcA(-) cells cannot form stalks at all, but showed no aggregation defects. The long, thin stalks of Ppal and Pvio dgcA(-) mutants were also observed in acaA(-) mutants in these species. AcaA encodes adenylate cyclase A, which mediates the effects of c-di-GMP on stalk induction in Ddis. Other factors that promote stalk formation in Ddis are DIF-1, produced by the polyketide synthase StlB, low ammonia, facilitated by the ammonia transporter AmtC, and high oxygen, detected by the oxygen sensor PhyA (prolyl 4-hydroxylase). We deleted the single stlB, amtC and phyA genes in Pvio wild-type and dgcA(-) cells. Neither of these interventions affected stalk formation in Pvio wild-type and not or very mildly exacerbated the long thin stalk phenotype of Pvio dgcA(-) cells. Conclusions The study reveals a novel role for c-di-GMP in aggregation, while the reduced spore number in Pvio and Ppal dgcA(-) is likely an indirect effect, due to depletion of the cell pool by the extended stalk formation. The results indicate that in addition to c-di-GMP, Dictyostelia ancestrally used an as yet unknown factor for induction of stalk formation. The activation of AcaA by c-di-GMP is likely conserved throughout Dictyostelia.

Biopharmaceuticals, including therapeutic antibodies, are rapidly growing products in the pharmaceutical market. Mammalian cells, such as Chinese hamster ovary (CHO) cells, are widely used as production hosts because recombinant antibodies require complex three-dimensional structures modified with sugar chains. Recombinant protein production using mammalian cells is generally performed in conjunction with cell growth. In this study, we developed a technology that controls cell growth and recombinant protein production to induce recombinant protein production with arbitrary timing. Expression of green fluorescent protein (GFP) gene and a single-chain antibody fused with the Fc-region of the human IgG1 (scFv-Fc) gene can be induced and mediated by the estrogen receptor-based artificial transcription factor Gal4-ERT2-VP16 and corresponding inducer drugs. We generated CHO cells using an artificial gene expression system. The addition of various concentrations of inducer drugs to the culture medium allowed control of proliferation and transgene expression of the engineered CHO cells. Use of 4-hydroxytamoxifen, an antagonist of estrogen, as an inducing agent yielded high gene expression at a concentration more than 10-fold lower than that of β-estradiol. When scFv-Fc was continuously produced under inducing conditions, stable production was possible for more than 2 weeks while maintaining high specific productivity (57 pg cell day). This artificial gene expression control system that utilizes the estrogen response of estrogen receptors can be an effective method for inducible production of biopharmaceuticals.

Researchers have long awaited the technology to develop an in vitro kidney model. Here, we establish a rapid fabricating technique for kidney-like tissues (cysts) using a combination of an organ-derived extracellular matrix (ECM) gel format culture system and a renal stem cell line (CHK-Q cells). CHK-Q cells, which are spontaneously immortalized from the renal stem cells of the Chinese hamster, formed renal cyst-like structures in a type-I collagen gel sandwich culture on day 1 of culture. The cysts fused together and expanded while maintaining three-dimensional structures. The expression of genes related to kidney development and maturation was increased compared with that in a traditional monolayer. Under the kidney-derived ECM (K-ECM) gel format culture system, cyst formation and maturation were induced rapidly. Gene expressions involved in cell polarities, especially for important material transporters (typical markers Slc5a1 and Kcnj1), were restored. K-ECM composition was an important trigger for CHK-Q cells to promote kidney-like tissue formation and maturation. We have established a renal cyst model which rapidly expressed mature kidney features via the combination of K-ECM gel format culture system and CHK-Q cells.

Immortalized kidney cell lines are widely used in basic and applied research such as cell permeability tests and drug screening. Although many cell lines have been established from kidney tissues, the immortalization process has not been clarified in these cell lines. In this study, we analyzed the phenotypic changes that occurred during the immortalization of kidney cells derived from Chinese hamster tissue in terms of karyotype and gene expression profiles. In the newly established cell line, designated as CHK-Q, gene expression profiles at each stage of the immortalization process and during the adaptation to serum-free conditions were analyzed by DNA microarray. Renal stem cell markers CD24 and CD133 were expressed in CHK-Q cells, suggesting that CHK-Q cells were transformed from renal stem cells. Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis to identify the pathways of upregulated and downregulated genes revealed that the immortalization of CHK-Q cells was associated with increased fluctuations in the expression of specific proto-oncogenes. Karyotype analysis of spontaneously immortalized CHK-Q cells indicated that CHK-Q chromosomes had a typical modal number of 23 but possessed slight chromosomal abnormalities. In this study, we investigated the mechanism of cell environmental adaptation by analyzing gene expression behavior during the immortalization process and serum-free adaptation. CHK-Q cells are applicable to the fields of biotechnology and biomedical science by utilizing their characteristics as kidney-derived cells.

The industrial use of living organisms for bioproduction of valued substances has been accomplished mostly using microorganisms. To produce high-value bioproducts such as antibodies that require glycosylation modification for better performance, animal cells have been recently gaining attention in bioengineering because microorganisms are unsuitable for producing such substances. Furthermore, animal cells are now classified as products because a large number of cells are required for use in regenerative medicine. In this article, we review animal cell technologies and the use of animal cells, focusing on useable cell generation and large-scale production of animal cells. We review recent advance in mammalian cell line development because this is the first step in the production of recombinant proteins, and it largely affects the efficacy of the production. We next review genetic engineering technology focusing on CRISPR-Cas system as well as surrounding technologies as these methods have been gaining increasing attention in areas that use animal cells. We further review technologies relating to bioreactors used in the context of animal cells because they are essential for the mass production of target products. We also review tissue engineering technology because tissue engineering is one of the main exits for mass-produced cells; in combination with genetic engineering technology, it can prove to be a promising treatment for patients with genetic diseases after the establishment of induced pluripotent stem cell technology. The technologies highlighted in this review cover brief outline of the recent animal cell technologies related to industrial and medical applications.

Functional human hepatocytes have been a pivotal tool in pharmacological studies such as those investigating drug metabolism and hepatotoxicity. However, primary human hepatocytes are difficult to obtain in large quantities and may cause ethical problems, necessitating the development of a new cell source to replace human primary hepatocytes. We previously developed genetically modified murine hepatoma cell lines with inducible enhanced liver functions, in which eight liver-enriched transcription factor (LETF) genes were introduced into hepatoma cells as inducible transgene expression cassettes. Here, we establish a human hepatoma cell line with heat-inducible liver functions using HepG2 cells. The genetically modified hepatoma cells, designated HepG2/8F_HS, actively proliferated under normal culture conditions and, therefore, can be easily prepared in large quantities. When the expression of LETFs was induced by heat treatment at 43 °C for 30 min, cells ceased proliferation and demonstrated enhanced liver functions. Furthermore, three-dimensional spheroid cultures of HepG2/8F_HS cells showed a further increase in liver functions upon heat treatment. Comprehensive transcriptome analysis using DNA microarrays revealed that HepG2/8F_HS cells had enhanced overall expression of many liver function-related genes following heat treatment. HepG2/8F_HS cells could be useful as a new cell source for pharmacological studies and for constructing bioartificial liver systems.