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HeLa



 

for other meanings, see also the disambiguation page Hela

A HeLa cell (also Hela or hela cell) is an immortal cell line used in medical research. The cell line was derived from cervical cancer cells taken from Henrietta Lacks, who died from her cancer in 1951.

Additional recommended knowledge

Contents

George Otto Gey and Henrietta Lacks

  The cells were propagated by George Otto Gey without Lacks' knowledge or permission and later commercialized, although never patented in their original form. There was then, as now, no requirement to inform a patient, or their relatives, about such matters because discarded material, or material obtained during surgery, diagnosis or therapy was the property of the physician and/or medical institution. This issue and Ms. Lacks' situation was brought up in the Supreme Court of California case of John Moore v. the Regents of the University of California. The court ruled that a person's discarded tissue and cells are not their property and can be commercialized.

Initially, the cell line was said to be named after a "Helen Lane" or "Helen Larson", in order to preserve Lacks's anonymity. Despite this attempt, her real name was used by the press within a few years of her death. These cells are treated as cancer cells, as they are descended from a biopsy taken from a visible lesion on the cervix as part of Ms. Lacks' diagnosis of cancer. A debate still continues on the classification of the cells.

HeLa cells are termed "immortal" in that they can divide an unlimited number of times in a laboratory cell culture plate as long as fundamental 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 descended from the same tumor cells removed from Ms. Lacks. It has been estimated that the total number of HeLa cells that have been propagated in cell culture far exceeds the number of cells in Henrietta Lacks' body.[1]

Telomerase

The HeLa cell line was derived for use in cancer research. These cells proliferate abnormally rapidly, even compared to other cancer cells. HeLa cells have an active version of the enzyme telomerase during cell division, which prevents the incremental shortening of telomeres that is implicated in aging and eventual cell death. In this way, HeLa cells circumvent the Hayflick Limit, which is the limited number of cell divisions that most normal cells can undergo before dying out in cell culture.

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 four copies of chromosome 12 and three 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]

Contamination

Because of their avid adaptation to growth in tissue culture plates, HeLa cells are sometimes difficult to control. For example, they have proven to be a persistent laboratory "weed" and they can contaminate other cell cultures in the same laboratory, interfering with biological research, and forcing researchers to declare many research results invalid because the cells used were found afterwards to be contaminated. The degree of HeLa cell contamination among other cell types is unknown, because few researchers test the identity or purity of already-established cell lines. It has been demonstrated that a substantial fraction of in vitro cell lines - approximately 10%, maybe 20%, are actually HeLa cells, because the original cells in the cell culture have 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 various cell lines by HeLa. [2]

Science writer, Michael Gold, in the Conspiracy of the Cells, describes Gartler's identification of this problem and Rees' many, and probably career-ending, efforts to identify this problem which Gold felt was occurring both in the best medical and research institutions in the USA and abroad, and in the laboratories of the best physicians, scientists, and researchers, including Jonas Salk.The HeLa contamination problem however was not found in the laboratories run by either Rees or Gey and his wife, Margaret Gey. Gold also states that this problem almost led to a cold war incident. Russia and the USA had started to cooperate in the war on cancer launched by President Nixon and then it was found the cells exchanged were contaminated by HeLa. Gold asks how much time, money and energy was wasted in the war against cancer because of HeLa contamination, or of what he called the HeLa problem.

Other authors have also examined issues surrounding the widespread HeLa contamination of cell lines used in research from the 1950s through at least the early 1980s,[3] and recent data suggest that cross contaminations are still a major ongoing problem with modern cell cultures.[4]

Helacyton gartleri

Due to their ability to replicate indefinitely, and their non-human number of chromosomes, Leigh Van Valen described HeLa as an example of the contemporary creation of a new species, Helacyton gartleri, named after Stanley M. Gartler, who Van Valen credits with discovering "the remarkable success of this species". His argument for speciation depends on three points:

  • The chromosomal incompatibility of HeLa cells with humans.
  • The ecological niche of HeLa cells.
  • Their ability to persist and expand well beyond the desires of human cultivators.

It should be noted that this definition has not been followed by others in the scientific community, nor, indeed, has it been widely noted. With near unanimity, evolutionary scientists and biologists hold that a chimeric human cell line is not a distinct species, and that tumorigenesis is not an evolutionary process.[citation needed]

As well as proposing a new species for HeLa cells, Van Valen proposes in the same paper the new family Helacytidae and the genus Helacyton. [5]

References

  1. ^ Terry Sharrer (2006): "HeLa" Herself. The Scientist 20:7 22
  2. ^ John R. Masters (2002): HeLa cells 50 years on: the good, the bad and the ugly. Nature Reviews Cancer 2:315-319
  3. ^ Louis Pascal (1991) "What happens when science goes bad" in Science and Technology Analysis Working Paper #9 University of Wollongong online
  4. ^ Roland M. Nardone (2006) "Eradication of Cross-Contaminated Cell Lines" white paper, Society for In-Vitro Biology online
  5. ^ Leigh Van Valen and Virginia C. Maiorana (1991). HeLa, a new microbial species. Evolutionary Theory, 10:71-74
  • Discussion about the taxonomic effect of creating the new taxon Helacyton.

Further reading

  • Hannah Landecker (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.

See also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "HeLa". A list of authors is available in Wikipedia.
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