Ever wondered where human embryonic kidney (HEK) cells originated from? Or why they are such a commonly used cell culture model? In this blog we will spill the beans on all things HEK, from the first experiments isolating the cell line all the way to modern applications.
What the HEK is it?
HEK cells were first isolated in the 1970s by Alex van der Eb in the Netherlands. Transformation of HEK cells with adenovirus 5 DNA was postdoc Frank Graham’s 293rd experiment, hence the nomenclature we use today: HEK-293. The exact origin of the fetal tissue which HEKs were isolated from is still a mystery, but it’s currently assumed that the cells came from an aborted fetus.
HEKs have an unusual ploidy and are considered hypotriploid: most chromosomes are represented by two to three copies, but several have four. No Y chromosome is present in this line, making it genetically female. HEKs are generally cultured as an adherent monolayer, though derivatives have been adapted for growth in suspension. Of the many derivatives of HEK-293, the most commonly used line expresses SV40 large T antigen and is thus dubbed HEK-293T.
Given that the modern-day cell line is far removed from the initial isolate, it is difficult to determine its true tissue origin. Originally, it was assumed HEKs were a common cell type within the kidney—either endothelial, epithelial, or fibroblast. However, Frank Graham showed HEKs display many immature neuron-like qualities, which is inconsistent with kidney cells (Shaw et al.). Since then, transcriptome studies of the cell line have determined it is most likely adrenal in origin. (Anatomy refresher: the adrenal gland is next to the kidney and is known to have some neuronal qualities.) While HEKs probably aren’t a great model of kidney cell biology, there are thankfully many other applications that they are useful for!
What the HEK is it good for?
As one of the older cell lines in the research community, many cellular research tools have been optimized specifically for and in HEKs. These systems built around HEKs offer an advantage to use the cell line and we will highlight some of those applications here.
Virus production
HEKs are the go-to ‘packaging cells’ for viral production because they express the SV40 large T-antigen. This allows them to replicate viral plasmids with the SV40 origin of replication. To generate a virus, you need only transfect the ‘helper’ plasmids (viral packaging machinery) along with the viral plasmid containing the cargo of interest, and HEKs will produce and package viral particles. The viral particles are then filtered to remove any unwanted material (HEK cells, etc.) and are ready to use on another cell or organism. This pipeline is utilized to transduce cell lines for basic science research all the way up to the production of clinical viral therapies.
Protein production
HEKs are extremely easy to transfect in bulk and produce recombinant proteins at high levels. In a case where clinical applications of recombinant proteins are necessary, HEKs are human in origin, so they eliminate non-human PTMs which is a concern with other protein production systems, such as yeast. HEKs can also grow in suspension, which allows for large scalability, and can also be adapted for serum-free growth, which significantly reduces the cost of production.
Research applications
There are two areas of research where HEK cells may be particularly useful due to their intrinsic properties.
- HEK-293 cells are tumorigenic, which makes them a candidate cell line model for cancer-specific research.
- Membrane receptors and ion channels are often exogenously expressed and studied in HEKs due to the cell line’s ability to faithfully produce these proteins and its relatively low expression of native channels.
No matter what your research question, HEK-293 is known for reproducible results. It’s also widely available, which can make for a seamless transition of biological tools to other researchers using the cell line.
What the HEK is wrong with it?
All cultured human cell lines are susceptible to contamination by mycoplasma and bacteria, but HEKs are also particularly vulnerable to viral infection. Yes, your cells can catch a cold—or worse!
HEK-293T and its derivatives are immortalized, but cell health can degrade over time in culture. This can affect factors that could skew research results (gene expression, growth rates, etc.). Thus, it’s important to maintain short culture periods (less than 20 passages) to prevent these issues from popping up, and if your research doesn’t allow for that, HEK might be the cell line for you.
Are HEKs for you?
If you are looking for a human cell line model, HEKs might be a great option! Especially if your research interests include receptor biology, ion channels, or involve human protein preparations with PTMs. Why the HEK not?
References and Resources
References
Shaw G., et al., Preferential transformation of human neuronal cells by human adenoviruses and the origin of HEK 293 cells. FASEB J. (2002) (8):869-71. DOI: 10.1096/fj.01-0995fje
Tan, E., et al., HEK293 Cell Line as a Platform to Produce Recombinant Proteins and Viral Vectors. Front Bioeng Biotechnol. (2021) (9):796991. DOI: 10.3389/fbioe.2021.796991
Additional resources on the Addgene blog
- Five Popular Model Organisms
- 10 Tips for Mammalian Cell Culture
- Adenoviral Vector Production and Troubleshooting
Additional resources on Addgene.org
Topics: Miscellaneous
Leave a Comment