HeLa



A HeLa cell (also Hela or hela cell) is a cell type in an immortal cell line used in scientific research. It is the oldest and most commonly used human cell line. The line was derived from cervical cancer cells taken on February 8, 1951 from Henrietta Lacks, a patient who eventually died of her cancer on October 4, 1951. The cell line was found to be remarkably durable and prolific as illustrated by its contamination of many other cell lines used in research.

George Otto Gey and Henrietta Lacks
The cells were propagated by George Otto Gey shortly before Lacks died in 1951. This was the first human cell line to prove successful in vitro, which was a scientific achievement with profound future benefit to medical research. Gey freely donated both the cells and the tools and processes his lab developed to any scientist requesting them, simply for the benefit of science. Neither Lacks nor her family gave Gey permission to harvest the cells, but, at that time, permission was neither required nor customarily sought. The cells were later commercialized, although never patented in their original form. Then, as now, there was 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 Mrs. Lacks' situation was brought up in the Supreme Court of California case of Moore v. 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.

At first, the cell line was said to be named after a "Helen Lane" or "Helen Larson", in order to preserve Lacks' 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 Mrs. 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 Mrs. Lacks. It has been estimated that the total number of HeLa cells that have been propagated in cell culture far exceeds the total number of cells that were in Henrietta Lacks' body.

Use in research
HeLa cells were used by Jonas Salk to test the first polio vaccine in the 1950s. Since that time, HeLa cells have been used for "research into cancer, AIDS, the effects of radiation and toxic substances, gene mapping, and many other scientific pursuits". According to author Rebecca Skloot, by 2009, "more than 60,000 scientific articles had been published about research done on HeLa, and that number was increasing steadily at a rate of more than 300 papers each month."

Telomerase
The HeLa cell line was derived for use in cancer research. These cells proliferate abnormally rapidly, even compared to other cancer cells. In Rebecca Skloot's The Immortal Life of Henrietta Lacks, she explains that HeLa cells have an active version of 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 later 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.

Contamination
Because of their adaptation to growth in tissue culture plates, HeLa cells are sometimes difficult to control. They have proven to be a persistent laboratory "weed" that contaminates other cell cultures in the same laboratory, interfering with biological research and forcing researchers to declare many results invalid. 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 contaminated with HeLa 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.

Science writer Michael Gold wrote about the HeLa cell contamination problem in his book A Conspiracy of Cells. He describes Nelson-Rees's identification of this pervasive worldwide problem — affecting even the laboratories of the best physicians, scientists, and researchers, including Jonas Salk — and many, possibly career-ending, efforts to address it. According to Gold, the HeLa contamination problem almost led to a Cold War incident: The USSR and the USA had begun to cooperate in the war on cancer launched by President Richard Nixon only to find that the exchanged cells were contaminated by HeLa. Gold contends that the HeLa problem was amplified by emotions, egos, and a reluctance to admit mistakes. Nelson-Rees explains: It's all human - an unwillingness to throw away hours and hours of what was thought to be good research...worries about jeopardizing another grant that's being applied for, the hurrying to come out with a paper first. And it isn't limited to biology and cancer research. Scientists in many endeavors all make mistakes, and they all have the same problems.

Rather than focus on how to resolve the problem of HeLa cell contamination, many scientists and science writers continue to document this problem as simply a contamination issue — caused not by human error or shortcomings but by the hardiness, proliferating, or overpowering nature of HeLa. Recent data suggest that cross-contaminations are still a major ongoing problem with modern cell cultures.

Helacyton gartleri
Due to their ability to replicate indefinitely, and their non-human number of chromosomes, HeLa was described by Leigh Van Valen as an example of the contemporary creation of a new species, Helacyton gartleri. The species was named after Stanley M. Gartler, whom Van Valen credits with discovering "the remarkable success of this species." His argument for speciation depends on three points: This definition has not been followed by others in the scientific community, nor, indeed, has it been widely noted.
 * 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.

As well as proposing a new species for HeLa cells, Van Valen proposed in the same paper the new family Helacytidae and the genus Helacyton. Recognition of Van Valen and Maiorana's names, however, renders Homo and Hominidae paraphyletic because Helacyton gartleri is most closely related to Homo sapiens.