HeLa cells, derived from a cervical cancer biopsy taken from Henrietta Lacks in 1951, have become the most widely used human cell line in biomedical research, touching virtually every corner of modern medicine from vaccine development to gene editing. Their influence is so pervasive that researchers have published tens of thousands of studies using them, and the cells have been shipped to laboratories on every continent. But the story of HeLa is not just one of scientific triumph; it is tangled with questions about genomic instability, laboratory contamination, and a decades-long ethical reckoning over the rights of the woman whose body produced them.
Why These Cells Refuse to Die
Most human cells have a built-in expiration date. Each time a cell divides, the protective caps on the ends of its chromosomes get a little shorter, and eventually the cell stops dividing or self-destructs. HeLa cells sidestep this limit by producing high levels of telomerase, the enzyme that rebuilds those caps. What makes this possible traces back to an aggressive strain of human papillomavirus (HPV 18) that integrated into the DNA of Henrietta Lacks’ tumor. The virus’s E6 protein disables p53, a key tumor suppressor, which in turn allows the cells to keep dividing indefinitely. Research has shown that even when scientists artificially boost telomerase activity in HeLa cells, repressing the E6 gene alone is enough to trigger aging and cell death, underscoring just how central the viral hijacking is to the cells’ immortality.1PubMed Central. Repression of the human papillomavirus E6 gene initiates p53-dependent, telomerase-independent senescence and apoptosis in HeLa cervical carcinoma cells
Telomerase activity in HeLa cells is not as straightforward as “enzyme on, immortality guaranteed.” When researchers separated HeLa cells into fast-dividing and slow-dividing populations, they found that the slowest-dividing cells actually had several times higher telomerase activity than the fastest dividers.2PubMed. Telomerase activity in HeLa cervical carcinoma cell line proliferation That counterintuitive finding hints at a more complex relationship between telomerase and cell behavior than the popular narrative of “immortal cells that never stop growing” suggests.
A Genome Unlike Any Normal Human Cell
HeLa cells are not a faithful copy of a human genome. Decades of uncontrolled division, combined with the genomic havoc wrought by HPV integration, have left these cells profoundly rearranged. They are near-triploid, meaning they carry roughly three copies of many chromosomes instead of the usual two. Depending on which sub-line a lab is working with, individual cells can contain anywhere from 56 to 79 chromosomes, compared to the 46 in a typical human cell.3Scientific Reports. High variability of genomic instability and gene expression profiling in different HeLa clones Different HeLa stocks held in different labs have drifted apart over the years, accumulating their own unique mutations and chromosomal rearrangements.
This genomic chaos has made fully mapping the HeLa genome a serious technical challenge. The extensive aneuploidy, or abnormal chromosome numbers, renders standard sequencing and assembly methods far less reliable than they would be for a normal diploid genome.4PubMed Central. The haplotype-resolved genome and epigenome of the aneuploid HeLa cancer cell line For researchers, this is a double-edged sword. The instability makes HeLa a useful model for studying how cancer genomes evolve, but it also means that results from one lab’s HeLa stock may not perfectly replicate in another’s, a source of quiet frustration across the field.
The Polio Vaccine and the First Mass-Produced Human Cells
The earliest and arguably most dramatic contribution of HeLa cells to public health came in the 1950s, when Jonas Salk needed a reliable way to grow and test poliovirus at scale. Before HeLa, researchers struggled to produce enough virus in culture to manufacture a vaccine. Tuskegee University played a pivotal role here, serving as the primary facility for mass-producing and distributing HeLa cells to laboratories and pharmaceutical manufacturers working on the Salk polio vaccine.5PubMed Central. Development of the polio vaccine: a historical perspective of Tuskegee University’s role in mass production and distribution of HeLa cells The cells grew quickly, were easy to ship, and could be infected with poliovirus in a predictable way. This made large-scale vaccine testing feasible for the first time.
The success of that effort established a model that the biomedical industry would follow for decades. Once it became clear that a standardized human cell line could be grown in bulk and shipped anywhere, the door opened to using HeLa cells for everything from basic virology to drug screening. The polio vaccine campaign essentially proved the concept of industrial-scale cell culture, and HeLa was the product that made the proof possible.
Screening Cancer Drugs Before They Reach Patients
One of the most routine uses of HeLa cells today is as a first-pass screening tool for potential cancer treatments. Because the cells grow aggressively and predictably, they provide a convenient platform for measuring whether a compound can kill cancer cells and at what concentration. Researchers have used HeLa to evaluate a wide range of anticancer drugs, including newer agents that target drug-resistant cancers. One systematic comparison tested 27 anticancer drugs on standard HeLa cells and on HeLa-derived lines that had been made resistant to vinblastine, offering a way to study how tumors evade treatment.6Biological and Pharmaceutical Bulletin. Cytotoxic Effects of 27 Anticancer Drugs in HeLa and MDR1-Overexpressing Derivative Cell Lines
HeLa cells have also been used to refine the methods by which drug potency is measured. A study comparing two common cytotoxicity assays found that a real-time cell monitoring approach and a traditional endpoint assay produced closely matched results when testing doxorubicin on HeLa cells, helping to validate newer, continuous-measurement techniques for drug screening.7ACS Omega. Comparison of Cytotoxicity Evaluation of Anticancer Drugs between Real-Time Cell Analysis and CCK-8 Method Meanwhile, nanoparticle-based drug delivery systems have been tested on HeLa cells to see whether encapsulating a compound improves its cancer-killing ability. In one case, nanoparticle delivery roughly halved the concentration needed to kill half the cells compared to the free drug alone.8PubMed Central. Cytotoxicity of ICD-85 NPs on Human Cervical Carcinoma HeLa Cells through Caspase-8 Mediated Pathway
It is worth keeping a sense of proportion about what these early-stage experiments mean. Killing cells in a dish is a necessary first step, but it is a long way from curing a patient. Many compounds that look promising against HeLa cells fail in animal models or clinical trials. HeLa’s value in drug screening is not that it predicts clinical success; it is that it efficiently weeds out compounds that cannot even clear the lowest bar.
Virology Beyond Polio
HeLa cells have remained a workhorse in virology well beyond their polio-era debut. Researchers studying human coronavirus 229E, a common-cold virus in the same family as the virus that causes COVID-19, used HeLa cells to demonstrate that the virus enters cells through an enzyme-mediated pathway involving the endosome. The study showed that HeLa cells infected with 229E formed characteristic fused cell clusters when treated with proteases, a pattern consistent with what had been observed in SARS coronavirus entry.9PubMed Central. Protease-mediated entry via the endosome of human coronavirus 229E
During the COVID-19 pandemic, HeLa cells found a new role. Because HeLa naturally produce very low levels of ACE2, the receptor SARS-CoV-2 typically uses to enter human cells, researchers realized they could use HeLa as a kind of blank slate. By engineering a library of gene-activating tools into HeLa cells and then exposing them to the virus, a team identified several alternative receptors the virus might exploit, including a protein called ASGR1 found on liver cells. That discovery helped explain why some patients develop liver complications from COVID-19.10Signal Transduction and Targeted Therapy. Asialoglycoprotein receptor 1 promotes SARS-CoV-2 infection of human normal hepatocytes The approach was clever: because HeLa resists infection through the main viral door, any cells that survived infection must have opened an alternative one, making those alternatives easy to find.
HeLa cells have also been adapted to grow in completely protein-free, chemically defined media, which matters for virology because it removes the confounding effects of animal serum. In this protein-free system, poliovirus and adenovirus grew to comparable levels as in standard serum-containing cultures, though herpes simplex virus produced lower yields, suggesting that the growth environment can influence which viruses HeLa supports well.11Karger. HeLa Cells Grown Continuously in Protein-Free Medium: A Novel Model for the Study of Virus Replication
Gene Editing and the CRISPR Era
HeLa cells have become a popular testing ground for CRISPR-based gene editing. Because the cells grow quickly and their biology is well characterized, they offer a convenient system for knocking out specific genes and observing what happens. Researchers used CRISPR to delete the NF-κB subunit c-REL in HeLa cells as a model for cervical cancer, and found that losing this gene caused severe disruptions to the cell cycle.12PLOS ONE. CRISPR/Cas9-mediated knockout of c-REL in HeLa cells results in profound defects of the cell cycle In another study, knocking out the NOX4 gene in HeLa cells reduced both cell proliferation and the cells’ ability to invade surrounding tissue, pointing to NOX4 as a potential target for cervical cancer therapy.13PLOS ONE. CRISPR-Cas9 Mediated NOX4 Knockout Inhibits Cell Proliferation and Invasion in HeLa Cells
These gene-editing experiments illustrate a broader pattern in how HeLa cells get used. They are rarely the end point of a study. Instead, they serve as the proving ground where a technique is tested and validated before being applied to more complex systems like animal models or patient-derived tumor samples. The logic is practical: if a gene knockout does not produce a clear effect in a fast-growing, well-understood cell line, it probably is not worth pursuing in more expensive and time-consuming models.
Radiation Biology and Understanding DNA Repair
Understanding how radiation damages cells and how cells attempt to repair that damage has been another major application. HeLa cells exposed to increasing doses of X-ray irradiation show a predictable cascade of effects: rising levels of reactive oxygen species, accumulating DNA double-strand breaks, increased cell death, and cells piling up in a particular phase of the cell cycle as they attempt to fix the damage before dividing.14PubMed Central. Effects of different doses of X-ray irradiation on cell apoptosis, cell cycle, DNA damage repair and glycolysis in HeLa cells This dose-response information is directly relevant to radiation oncology, where clinicians need to choose doses that kill tumor cells without annihilating surrounding healthy tissue.
HeLa cells have also been useful in comparing different types of radiation. Because HeLa tends to be relatively resistant to standard X-rays, researchers have used it to assess whether heavier particle beams, like carbon ions, can overcome that resistance. A proteomic study comparing X-ray and carbon-beam irradiation at the same dose found distinct patterns of protein changes, offering molecular-level insight into why particle therapy can sometimes succeed where conventional radiation falls short.15PubMed Central. Proteomic analysis of effects by x-rays and heavy ion in HeLa cells
The Contamination Problem That Will Not Go Away
HeLa’s greatest strength, its aggressive, unstoppable growth, is also the source of one of cell biology’s most embarrassing ongoing problems. HeLa cells are the most frequent source of cross-contamination among laboratory cell lines.16PubMed Central. Discovery of HeLa Cell Contamination in HES Cells: Call for Cell Line Authentication in Reproductive Biology Research If even a few HeLa cells drift into a flask of supposedly different cells, they tend to outcompete and replace the original culture entirely. The researcher then spends months or years studying what they believe is, say, a liver cancer cell line when they are actually studying cervical cancer cells in disguise.
The scale of the problem is staggering. One investigation of 278 commonly used tumor cell lines found that about 47 percent of all cross-contamination cases were caused by HeLa, affecting cell lines supposedly representing ten different tumor types and three types of normal tissue. Among all identified contaminants in that study, HeLa accounted for roughly two-thirds.17PLOS ONE. Investigation of Cross-Contamination and Misidentification of 278 Widely Used Tumor Cell Lines The contamination debate first surfaced in the 1970s, but resistance from researchers who did not want to accept that their work might be compromised meant the problem was never fully resolved. It continues today.18Archives of Pathology and Laboratory Medicine. Henrietta Lacks, HeLa cells, and cell culture contamination
Modern authentication methods based on short tandem repeat (STR) profiling have given labs a reliable tool for catching contamination. Analysis of roughly 400 human cell lines in one major repository found that more than ten lines were in fact identical to a different deposited line, revealing misidentifications that would otherwise have gone unnoticed.19PubMed. Essential role for gene profiling analysis in the authentication of human cell lines A particularly striking case involved KU7, a bladder cancer cell line used in published research for decades, which genetic profiling ultimately revealed to be HeLa cells.20PubMed Central. Hiding in plain view: genetic profiling reveals decades old cross contamination of bladder cancer cell line KU7 with HeLa Every paper that drew conclusions about bladder cancer biology using KU7 was really drawing conclusions about a cervical cancer cell line. Many journals now require STR authentication before accepting studies that rely on cell lines, but enforcement remains uneven.
Henrietta Lacks and the Ethics of Biospecimens
Henrietta Lacks’ cells were taken without her knowledge or consent in 1951, a practice that was standard at the time but has since become a flashpoint in bioethics. Her family learned about the existence of HeLa cells only in the 1970s, and for decades they received no compensation or recognition while the cells were used in research that generated enormous scientific and commercial value. The story became widely known after Rebecca Skloot’s 2010 book, and a media analysis found that informed consent dominated public discussion, appearing as a major theme in about 39 percent and a minor theme in about 45 percent of media coverage. Donor compensation and the welfare of vulnerable populations were also prominent concerns.21PubMed Central. Bioethics in popular science: evaluating the media impact of The Immortal Life of Henrietta Lacks on the biobank debate
The ethical tensions flared again in 2013 when researchers published the HeLa genome without consulting the Lacks family, raising concerns about genetic privacy. The family pointed out that the genomic data could reveal hereditary information about living relatives. After the family’s objections, the NIH negotiated an agreement giving the Lacks family a role in reviewing applications to access HeLa genomic data.22PubMed Central. The Henrietta Lacks legacy grows The HeLa case has served as a catalyst for broader policy changes, including proposed regulatory reforms in the United States around informed consent for biospecimens.23PubMed Central. Lessons from HeLa Cells: The Ethics and Policy of Biospecimens
More recently, the Lacks estate has pursued litigation against companies that have profited from the cells, including Thermo Fisher Scientific and pharmaceutical companies Ultragenyx and Novartis. The legal strategy centers on unjust enrichment, an approach designed to sidestep the property-law and consent doctrines that have defeated similar lawsuits in the past. The case raises novel questions about whether benefit-sharing can be enforced as a legal duty rather than treated as a voluntary ethical gesture.24PubMed. The Henrietta Lacks Case: Ongoing Litigation Seeks Closure Whatever the courts ultimately decide, the litigation has already shifted the conversation: the idea that tissues taken from a patient can generate billions in commercial value without any obligation flowing back to the source is harder to defend publicly than it once was.
When HeLa Is the Wrong Model
For all their utility, HeLa cells are a poor stand-in for normal human biology. Their near-triploid genome, HPV-driven immortality, and decades of genetic drift mean they behave differently from the healthy cells in your body and even from many primary tumor samples. When researchers fused HeLa cells with normal human fibroblasts, the resulting hybrid cells mostly lost their immortality and could not form tumors in mice, even at doses twenty times higher than what it took for pure HeLa cells to generate tumors.25European Journal of Cancer and Clinical Oncology. Expression of transformation markers and suppression of tumorigenicity in human cell hybrids That experiment neatly demonstrated that normal cells carry tumor-suppressing mechanisms strong enough to override HeLa’s cancerous traits, but it also highlighted how abnormal HeLa really is.
Researchers increasingly recognize that relying too heavily on any single cell line, including HeLa, can produce findings that do not generalize well. Many labs now validate key results in multiple cell lines or in patient-derived organoids. HeLa remains a useful first-pass tool, a cheap and fast way to test a hypothesis before investing in more complex systems. But treating HeLa results as definitive evidence about human biology without further validation is a mistake the field has made before and is still learning to avoid.