Characterization of JOK-1, a human gastric epithelial cell line

Establishment and characterization of an immortalized epithelial cell line from human gallbladder

Background

Although a plethora of studies have employed multiple gallbladder cancer (GBC) cell lines, it is surprisingly noted that there is still lack of a normal gallbladder epithelial cell line as a normal counterpart, thus impeding substantially the progress of mechanistic studies on the transformation of normal epithelial cells to cancer. Here, we created a normal gallbladder epithelial cell line named L-2F7 from human gallbladder tissue.

Methods

Gallbladder tissues from a diagnosed cholecystitis female patient were collected, and epithelial cells were enriched by magnetic cell sorting. Then, the cells were immortalized by co-introduction of human telomerase reverse transcriptase (hTERT) and Simian virus 40 large T antigen (LT-SV40) via a lentivirus infection system. After clonal selection and isolation, L-2F7 cells were tested for epithelial markers CK7, CK19, CK20, and CD326, genomic feature, cell proliferation, and migration using Western blot, immunofluorescence, whole genome sequencing, karyotyping, and RNA sequencing. L-2F7 cells were also transplanted to Nude (nu/nu) mice to determine tumorigenicity.

Results

We successfully identified one single-cell clone named L-2F7 which highly expressed epithelial markers CD326, CK7, CK19, and CK20. This cell line proliferated with a doubling time of 23 h and the epithelial morphology sustained over 30 passages following immortalization. Transient gene transduction of L-2F7 cells led to expression of exogenous GFP and FLAG protein. L-2F7 cells exhibited both distinct non-synonymous mutations from those of gallbladder cancer tissues and differential non-cancerous gene expression patterns similar to normal tissue. Although they displayed unexpected mobility, L-2F7 cells still lacked the ability to develop tumors.

Conclusion

We developed a non-cancerous gallbladder epithelial cell line, offering a valuable system for the study of gallbladder cancer and other gallbladder-related disorders.

Mucus-producing 3D cell culture models

In vitro cell-based models have been used for a long time since they are normally easily obtained and have an advantageous cost-benefit. Besides, they can serve a variety of ends, from studying drug absorption and metabolism to disease modeling. However, some in vitro models are too simplistic, not accurately representing the living tissues. It has been shown, mainly in the last years, that fully mimicking a tissue composition and architecture can be paramount for cellular behavior and, consequently, for the outcomes of the studies using such models. Because of this, 3D in vitro cell models have been gaining much attention, since they are able to better replicate the in vivo environment. In this review we focus on 3D models that contain mucus-producing cells, as mucus can play a pivotal role in drug absorption. Being frequently overlooked, this viscous fluid can have an impact on drug delivery. Thus, the aim of this review is to understand to which extent can mucus affect mucosal drug delivery and to provide a state-of-the-art report on the existing 3D cell-based mucus models.

The role of mucus in cell-based models used to screen mucosal drug delivery

The increasing interest in developing tools to predict drug absorption through mucosal surfaces is fostering the establishment of epithelial cell-based models. Cell-based in vitro techniques for drug permeability assessment are less laborious, cheaper and address the concerns of using laboratory animals. Simultaneously, in vitro barrier models that thoroughly simulate human epithelia or mucosae may provide useful data to speed up the entrance of new drugs and new drug products into the clinics. Nevertheless, standard cell-based in vitro models that intend to reproduce epithelial surfaces often discard the role of mucus in influencing drug permeation/absorption. Biomimetic models of mucosae in which mucus production has been considered may not be able to fully reproduce the amount and architecture of mucus, resulting in biased characterization of permeability/absorption. In these cases, artificial mucus may be used to supplement cell-based models but still proper identification and quantification are required. In this review, considerations regarding the relevance of mucus in the development of cell-based epithelial and mucosal models mimicking the gastro-intestinal tract, the cervico-vaginal tract and the respiratory tract, and the impact of mucus on the permeability mechanisms are addressed. From simple epithelial monolayers to more complex 3D structures, the impact of the presence of mucus for the extrapolation to the in vivo scenario is critically analyzed. Finally, an overview is provided on several techniques and methods to characterize the mucus layer over cell-based barriers, in order to intimately reproduce human mucosal layer and thereby, improve in vitro/in vivo correlation.

The NCI-N87 cell line as a gastric epithelial barrier model for drug permeability assay

The objective of this study was to evaluate the human NCI-N87 cell line as a model for gastric permeability drug studies under pH conditions of the stomach. The optimal conditions that led NCI-N87 cells to form a typical differentiated gastric epithelial barrier were a seeding density of 2.5 × 10⁵ cells/cm² on porous inserts and growth in serum-complemented RPMI-1640 medium until 18-27 days post-confluency. The resulting cell monolayers showed moderately high transepithelial electrical resistance (TEER) values of about 500 Ω cm², cells of polygonal morphology expressing E-cadherin and ZO-1 proteins at their contact surfaces, and production of mucus clusters. The monolayers withstood apical pH of 7.4 down to 3.0 with the basal pH fixed at 7.4. The apparent permeability coefficients (P(app)) of model compounds were evaluated in the apical-to-basolateral and basolateral-to-apical directions under different pH gradients. The monolayers were impermeable to the integrity marker Lucifer Yellow (low P(app) of 0.3-1.1 × 10⁻⁶ cm/s). The furosemide P(app) (0.4-1.5 × 10⁻⁵ cm/s) were slightly dependent on pH but remained moderate. The caffeine P(app) (4.2-5.0 × 10⁻⁵ cm/s) were higher and insensitive to pH changes. The NCI-N87 cell line provides a useful in vitro tool to assess gastric drug permeability and absorption under physiologic conditions prevailing in the human stomach.

Roles of neuraminidase in the initial stage of influenza virus infection

We propose a concept that neuraminidase (NA) promotes virus entry into target cells during the initial stage of viral infection, in addition to the generally accepted concept that influenza virus NA promotes the release of progeny virus from a host cell at the final stage of viral replication. When NA activity was inhibited with specific inhibitors such as zanamivir and oseltamivir carboxylate, infection efficiency of the virus to MDCK and A549 cells was reduced to approximately 1/4 and 1/8, respectively. NA inhibitors did not significantly affect virus binding and envelope fusion activities, when assessed using an erythrocyte and virus system. Since the initial stage of viral infection involves binding of the virus to the target cell, virus entry into an endosome and envelope fusion with the endosomal membrane, our results indicated that NA inhibitors interfered with the virus entry step. Thus, NA is thought to promote virus entry, and thereby enhances infection efficiency.

The intermediate filament protein vimentin is a new target for epigallocatechin gallate

Epigallocatechin gallate (EGCG) is the major active polyphenol in green tea. Protein interaction with EGCG is a critical step in the effects of EGCG on the regulation of various key proteins involved in signal transduction. We have identified a novel molecular target of EGCG using affinity chromatography, two-dimensional electrophoresis, and mass spectrometry for protein identification. Spots of interest were identified as the intermediate filament, vimentin. The identification was confirmed by Western blot analysis using an anti-vimentin antibody. Experiments using a pull-down assay with [3H]EGCG demonstrate binding of EGCG to vimentin with a Kd of 3.3 nm. EGCG inhibited phosphorylation of vimentin at serines 50 and 55 and phosphorylation of vimentin by cyclin-dependent kinase 2 and cAMP-dependent protein kinase. EGCG specifically inhibits cell proliferation by binding to vimentin. Because vimentin is important for maintaining cellular functions and is essential in maintaining the structure and mechanical integration of the cellular space, the inhibitory effect of EGCG on vimentin may further explain its anti-tumor-promoting effect.