HeLa cells comprise an immortalized, continuously cultured cell line of human cancer cells. Unlike normal body (somatic) cells, HeLa cells thrive indefinitely in laboratory tissue cultures, a trait that has allowed them to assume tremendous importance in biomedical research. Since the mid-twentieth century, the cells have been distributed around the world and used in innumerable medical endeavors, including investigations into the nature of cancer, the development of vaccines, the mapping of genes, the treatment of diseases, and the mechanisms involved with programmed cell death (apoptosis). See also: Apoptosis; Cancer (medicine); Cell (biology); Cell biology; Disease; Genetic mapping; Oncology; Somatic cell genetics; Tissue culture; Vaccination
The cell line arose in 1951 from samples collected during a biopsy on Henrietta Lacks, a poor 31-year-old African-American patient suffering from a cervical tumor. The designation HeLa, derived from the first two letters of her first and last names, was used to keep her identity anonymous. (Henrietta Lacks, who died later in 1951, was not publicly identified as the source of the cells for another two decades.) During subsequent investigations, the sample cells were found to behave abnormally. Unlike typical somatic cells, which undergo cell aging (senescence) and lose the ability to divide and replicate after a few dozen generations (the so-called Hayflick limit), the cells from Henrietta Lacks never stop dividing. Being tumor cells, HeLa cells also do not die from apoptosis, the mechanism that normally causes abnormal or unneeded cells to self-destruct. HeLa cells thus became the first line of human cells to survive indefinitely in vitro (under proper culture-growing conditions). The hardiness of these cells was noted early in the medical literature, resulting in numerous requests by other laboratories and research institutions for samples that could be cultured. As such, HeLa cells were disseminated around the world and became the basis for numerous medical studies that have benefited humankind. For example, Jonas Salk used HeLa cells in the work leading up to his creation of a vaccine for polio. In addition, HeLa cells were the first human cells to be cloned. See also: Cancer cell metabolism; Cell senescence; Cloning; Cloning research; Human papillomavirus: impact of cervical cancer vaccine; Polio eradication; Poliomyelitis
HeLa cells grow in vitro so aggressively that they have become problematic. If laboratory workers are not extremely careful to avoid cross-contamination, HeLa cells can invade other cultures and quietly replace the original cells, with the result that investigators may be mistaken about the cells on which they are experimenting. Estimates in the 1970s suggested that 10–20% of all cultured lines may have been contaminated by HeLa cells.
Controversy also surrounded the control and ownership of the HeLa cells. In 1951, Henrietta Lacks had not given consent for her biopsied cells to be used for any purpose other than diagnosis of her disease. Nor was her family ever informed about the continuing scientific use of these unique cells and the immense value that they provided to medicine as remarkable research tools. Those failures constituted violations of bioethical standards. Fortunately, the family and the National Institutes of Health came to a mutual understanding about future procedures involving HeLa cells, ensuring their continued utility for medical and biotechnological research. See also: Bioethics; Biotechnology; Public health