HeLa

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(Redirected from Hela cell)

for other meanings, see also the disambiguation page Hela

A HeLa cell (also Hela or hela cell) is both an immortal cell line (it does not age) used in medical research and a proposed new single cell species (Helacyton gartleri) created via horizontal gene transfer. The cell line was derived from cervical cancer cells taken from Henrietta Lacks, who died from her cancer in 1951.

1 George Otto Gey and Henrietta Lacks
2 Telomerase
3 Chromosome number
4 Contamination
5 Helacyton gartleri
6 References
7 External links

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George Otto Gey and Henrietta Lacks

The cells were propagated without Lacks' knowledge or permission by George Otto Gey. Initially, the cell line was said to be named after a "Helen Lane" or "Helen Larson", in order to preserve Lacks' anonymity. These cells are treated as cancer cells, as they are believed to have stemmed from Ms. Lacks' cervical cancer, but a debate still continues on the classification of the cells.

HeLa are considered "immortal": they do not die of old age and can divide an unlimited number of times as long as basic cell survival conditions are met (i.e. being maintained and sustained in a suitable environment). There are many strains of HeLa cells as they continue to evolve by being grown in cell cultures, but all HeLa cells are derived from the same tumour cells removed from Lacks. It has been estimated that the total mass of HeLa cells today far exceeds that of the rest of Henrietta Lacks' body.

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Telomerase

This cell line was propagated for use in cancer research. The cells proliferate abnormally rapidly, even compared to other cancers. They have active telomerase during cell division, preventing the incremental shortening of telomeres that leads to aging and eventual cell death. In this way, HeLa cells circumvent the Hayflick Limit.

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Chromosome number

Horizontal gene transfer from human papillomavirus 18 (HPV18) to human cervical cells created the HeLa genome which is different from either parent genome in various ways including its number of chromosomes. HeLa cells have a modal chromosome number of 82, with 4 copies of chromosome 12 and 3 copies of chromosomes 6, 8, and 17.

Human papillomaviruses (HPVs) are frequently integrated into the cellular DNA in cervical cancers. We mapped by FISH five HPV18 integration sites: three on normal chromosomes 8 at 8q24 and two on derivative chromosomes, der(5)t(5;22;8)(q11;q11q13;q24) and der(22)t(8;22)(q24;q13), which have chromosome 8q24 material. An 8q24 copy number increase was detected by CGH. Dual-color FISH with a c-MYC probe mapping to 8q24 revealed colocalization with HPV18 at all integration sites, indicating that dispersion and amplification of the c-MYC gene sequences occurred after and was most likely triggered by the viral insertion at a single integration site. Numerical and structural chromosomal aberrations identified by SKY, genomic imbalances detected by CGH, as well as FISH localization of HPV18 integration at the c-MYC locus in HeLa cells are common and representative for advanced stage cervical cell carcinomas. The HeLa genome has been remarkably stable after years of continuous cultivation; therefore, the genetic alterations detected may have been present in the primary tumor and reflect events that are relevant to the development of cervical cancer.[1]

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Contamination

HeLa cells are difficult to control. They may contaminate other cell cultures in the same laboratory, interfering with biological research. The degree of contamination is unknown, because few researchers test the identity or purity of already-established cell lines. It has been claimed that a substantial fraction of in vitro cell lines are actually HeLa, their original cells having been overwhelmed by a rapidly growing population derived from HeLa contaminant cells. Stanley Gartler in 1967, and Walter Nelson-Rees in 1975 were the first to publish on the contamination of cell lines by HeLa.

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Helacyton gartleri

Due to their ability to replicate indefinitely, and their non-human chromosome number, Leigh Van Valen controversially described them as an example of the comtemporary creation of a new species, Helacyton gartleri (Van Valen & Maiorana 1991).

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References

Masters, John R. (2002): HeLa cells 50 years on: the good,the bad and the ugly. Nature Reviews Cancer 2:315-319
Landecker, Hannah (2000): Immortality, In Vitro: A History of the HeLa Cell Line. Biotechnology and Culture: Bodies, Anxieties, Ethics, ed. Paul Brodwin, Indiana University Press: 53-74.
Van Valen, Leigh M. & Maiorana, Virginia C. (1991): HeLa, a new microbial species. Evolutionary Theory 10:71-74.

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