Yes, HeLa cells are cancer cells. They originated from an aggressive cervical tumor removed from a 31-year-old woman named Henrietta Lacks in 1951 at Johns Hopkins Hospital. More specifically, they came from a cervical adenocarcinoma, a type of cancer that forms in the glandular tissue of the cervix. What makes HeLa cells remarkable, and different from most cancer cells taken from patients, is that they never stopped dividing. Over seven decades later, they are still alive and growing in laboratories around the world.
Where HeLa Cells Came From
During Henrietta Lacks’ cancer treatment, a sample of her tumor was taken and given to a researcher at Johns Hopkins. At the time, scientists had been trying for years to keep human cells alive outside the body, but cells from healthy tissue and even most tumors would die within days. Lacks’ cancer cells were different. They survived, multiplied aggressively, and showed no signs of slowing down. The cell line was named “HeLa” from the first two letters of her first and last name.
Lacks did not consent to having her cells used for research, and her family was not informed for decades. Her story has since raised important questions about medical ethics, patient consent, and the exploitation of Black patients in American medicine.
Why These Cancer Cells Never Die
Normal human cells have a built-in limit on how many times they can divide. Each time a cell copies itself, the protective caps on the ends of its chromosomes (called telomeres) get a little shorter. Eventually they become too short, and the cell stops dividing or dies. Cancer cells often find ways around this, but HeLa cells are especially effective at it.
HeLa cells carry DNA from human papillomavirus type 18 (HPV 18), which integrated directly into the cell’s own genome on chromosome 8. The virus brought along genes that produce two proteins, E6 and E7, which disable the cell’s two most important brakes on uncontrolled growth. E6 targets a protein called p53, which normally detects DNA damage and forces the cell to stop dividing or self-destruct. In HeLa cells, E6 promotes the destruction of p53, effectively removing that safety net. E7, meanwhile, disables a second checkpoint protein that controls when a cell is allowed to copy its DNA.
With both major tumor-suppressing systems knocked out, HeLa cells divide without restraint. They also produce high levels of an enzyme that rebuilds their telomeres after each division, so the chromosome caps never shorten. The result is a cell that can, in theory, divide forever. Their average doubling time is roughly 46 hours, meaning a single cell becomes two in under two days.
How HeLa Cells Differ From Normal Human Cells
HeLa cells don’t just behave differently from normal cells. They look different at the genetic level too. A healthy human cell contains 46 chromosomes. HeLa cells carry between 60 and 80 chromosomes in most samples, a condition called aneuploidy. This chaotic chromosome count is a hallmark of aggressive cancers, where the machinery that divides chromosomes evenly between daughter cells has broken down.
The viral genes from HPV 18 are amplified on chromosome 8, sitting near a gene called myc that promotes cell growth. The E6 and E7 genes are amplified about 5-fold, while other parts of the viral DNA and nearby cellular sequences are amplified as much as 15-fold. This amplification, combined with the constant activation of growth-promoting genes, helps explain why HeLa cells are so extraordinarily aggressive compared to other cancer cell lines.
After more than 70 years in laboratories, HeLa cells have also drifted genetically. Different labs maintain different strains, and these strains no longer look the same at the molecular level. A 2019 study found substantial genetic differences between HeLa variants, particularly between the CCL2 and Kyoto strains, with progressive divergence occurring over as few as 50 rounds of cell division. These genetic differences translate into real functional differences: different HeLa strains respond differently to the same infections and drug treatments.
What HeLa Cells Have Made Possible
Because HeLa cells grow reliably and quickly, they became the first human cell line that could be mass-produced and shipped to laboratories everywhere. They were instrumental in developing the polio vaccine in the 1950s, when researchers needed large quantities of human cells to grow the virus. Since then, they have been used in research on cancer, HIV, gene mapping, radiation effects, and countless drug-testing experiments. They were central to early work on how the enzyme telomerase keeps cells dividing, research that eventually won a Nobel Prize.
Their impact on science is difficult to overstate. They are referenced in tens of thousands of published studies and remain one of the most commonly used cell lines in biomedical research today.
The Contamination Problem
The same aggressive growth that makes HeLa cells useful also makes them a problem. HeLa cells are the most frequent source of cross-contamination in cell culture laboratories. If even a few HeLa cells accidentally get into a dish of other cells, they can outcompete and replace the original culture entirely. Researchers have discovered, sometimes decades later, that cell lines they thought came from other tissues were actually HeLa cells all along.
This issue was first flagged in the 1960s and 1970s, but it has persisted. An analysis of cell lines evaluated by international cell banks found that about 16% of lines were misidentified in 1977, and the rate was still 18% in 1988. The problem continues today. In one documented case, a cell line supposedly derived from human endometrial tissue and another from amnion tissue were both found to be HeLa cells when tested with modern genetic fingerprinting. Morphological examination alone, looking at cells under a microscope, was not enough to tell them apart.
This means some published research attributed to other cell types was actually conducted on cervical cancer cells. While the fundamental biology observed in those studies often still holds, the contamination issue is a reminder that HeLa cells are uniquely tenacious, behaving in the lab much the way an aggressive cancer behaves in the body: invading, outcompeting, and taking over.