In 1951, the first human immortal cell line, HeLa, was established and successfully grown in vitro (1). The cells had been isolated from the cervical cancer of a patient called Henrietta Lacks. Up until that point, cells could be maintained in in vitro culture only temporarily. An immortal cell line allowed scientists to perform experiments that had not been possible before and could be shared between labs. In fact, fewer than two years after their initial isolation, HeLa cells were being used to grow poliomyelitis viruses (2), and played an important role in the development of the poliomyelitis vaccine. Over the last 50 years, HeLa cells have become the most commonly used cells in biological research and have been used as a model for the characterisation of various biological processes. (3)
The publication of the HeLa cell genome (4) has recently sparked discussion surrounding privacy concerns of genomic data (5).

References

1. Gey GO, Coffman WD & Kubicek MT. Tissue culture studies of the proliferative capacity of cervical carcinoma and normal epithelium. Cancer Res 1952; 12:264-265.
2. Scherer WF, Syverton JT, Gey GO. Studies on the propagation in vitro of poliomyelitis viruses. IV. Viral multiplication in a stable strain of human malignant epithelial cells (strain HeLa) derived from an epidermoid carcinoma of the cervix. J Exp Med 1953; 97(5):695-710. (Link)
3. Collins, F. (2013). HeLa Cells: A New Chapter in An Enduring Story.

[NHI Director’s Blog, 7 August 2013]. Available at: http://directorsblog.nih.gov/2013/08/07/hela-cells-a-new-chapter-in-an-enduring-story/
4. Landry JJ, Pyl PT, Rausch T, Zichner T, Tekkedil MM, Stütz AM, Jauch A, Aiyar RS, Pau G, Delhomme N, Gagneur J, Korbel JO, Huber W & Steinmetz LM. The genomic and transcriptomic landscape of a HeLa cell line. G3 (Bethesda) 2013; 3(8):1213-24. (Link)
5. Greely HT & Cho MK. The Henrietta Lacks legacy grows. EMBO Rep 2013; 14(10):849. (Link)