HEK 293 cells

[1][2] The HEK 293 cell line has been widely used in research for decades due to its reliable and fast growth and propensity for transfection.

The cell line is used by the biotechnology industry to produce therapeutic proteins and viruses for gene therapy as well as safety testing for a vast array of chemicals.

Graham performed the transfection a total of eight times, obtaining just one clone of cells that were cultured for several months.

Subsequent analysis has shown that the transformation was brought about by inserting ~4.5 kilobases from the left arm of the adenoviral genome, which became incorporated into human chromosome 19.

However, the original adenovirus transformation was inefficient, suggesting that the cell that finally produced the HEK 293 line may have been unusual in some fashion.

The widespread use of this cell line is due to its transfectability by the various techniques, including calcium phosphate method, achieving efficiencies approaching 100%.

Examples of such experiments include: HEK 293 cells were adapted to grow in suspension culture, as opposed to proliferation on plastic plates, in 1985.

[23] Viruses offer an efficient means of delivering genes into cells, which they evolved to do, and are thus of great use as experimental tools.

This danger can be avoided by the use of viruses which lack key genes, and which are thus unable to replicate after entering a cell.

In order to propagate such viral vectors, a cell line that expresses the missing genes is required.

[31][32][33][34] On 21 December 2020, the Roman Catholic Congregation for the Doctrine of the Faith stated that the moral duty to avoid vaccines made from cell lines derived from fetuses is, "not obligatory if there is grave danger, such as the otherwise uncontainable spread of a serious pathological event -- in this case, the pandemic spread of SARS-CoV-2 virus that causes Covid-19".

[37][32] In response to ethical concerns of vaccine production, several strategies for clinicians to discuss with their patients have been suggested.