by Noel Jackson
figures by Daniel Utter
Have you ever wondered how scientists study human tissue in the lab? They do so with the help of authentic human cells. Normal cells in the human body have a finite number of replications, which limits their lifespan. Immortal cancer cells escape this limit and replicate indefinitely, making them ideal for research that requires a constant supply of quickly growing cells. Today, thousands of distinct proliferative human cell cultures called “cell lines” are used as biospecimens in medical research. The discovery of naturally occurring immortal cells occurred 70 years ago with the identification of a cell line called HeLa. The HeLa cell line still lives today and is serving as a tool to uncover crucial information about the novel coronavirus.
HeLa cells were the first human cells to survive and thrive outside the body in a test tube. Ever since then, HeLa cell lines have been used in more than 100,000 scientific PubMed publications on a range of topics including cancer, cell biology, genetics, and infectious diseases. Plus, studies in this cell line have led to pioneering discoveries that have merited three Nobel prizes to date!
But where do these cells come from? As it turns out, they originate from the uterus of a 31-year-old African American mother who was diagnosed with an unusually aggressive form of cervical cancer in 1951. The young woman’s name was Henrietta Lacks.
Henrietta Lacks and her special cells
Henrietta Lacks grew up with extended relatives in a poor community in Clover, Virginia. As a child, she worked on the family farm growing tobacco. Ten years after moving to Baltimore, Maryland with her husband and children, she entrusted Dr. Howard Jones at Johns Hopkins Hospital to treat the pain she began to experience in her abdomen. Dr. Jones diagnosed her with cervical cancer. While Lacks succumbed to the cancer a few months later, an extension of her lives on as a crucial tool in science. Her immortal cells remain circulating among scientists in laboratories all over the world today.
Without her knowledge or permission, pieces of the tumor from her cervix were taken and given to Dr. George Otto Gey for cancer research. Like many other scientists, Dr. Gey was working to model human cancer in a test tube to develop therapeutics against the disease. While many cancer cells grow and replicate uncontrollably, those that grew as such outside the body were not known until Henrietta Lacks’s cells were discovered. Cells from her tumor grew indefinitely in flasks in Dr. Gey’s lab. The HeLa cell line, coined after the letters of her first and last names, was born.
HeLa cells revolutionized biomedical research
After their discovery, scientists were able to directly perform tests on human tissue outside the body for the first time. The excitement about HeLa cells crossed industrial and geographical boundaries (Figure 1). They were sent to space during the Space Race to uncover the impact of zero gravity on human cells. They were studied to determine the effects of radiation after nuclear bomb explosions. They were even used by the beauty industry to test potential side-effects of new cosmetic products. The cells were used by biomedical researchers all over the world to study genetic mutations as cells divide, discover potential cancer therapeutics, and develop treatments for infectious diseases.
HeLa cells and virus research: then and now
HeLa cells were first used to study the growth and spread of poliomyelitis virus, the pathogen that causes polio. This research eventually led scientists to develop a vaccine for polio in the U.S. All children born in the U.S. now receive four doses of the inactivated poliovirus (IPV) vaccine to prepare their immune system to fend off polio infections. Now, the worldwide incidence of wild polio has dropped 99% and is completely eradicated in the Americas, Europe, South East Asia, the Western Pacific, and, most recently, Africa. The Center for Disease Control (CDC) projected that, in the absence of a vaccine, more than 17 million people would have been infected and paralyzed by the virus. Without HeLa cells, this projection may have become a globally morbid reality.
When initially discovered, HeLa cells were the human cell line of choice to study the viral pathogenesis of polio. Now, they are paving the way for COVID-19 research breakthroughs. The groundbreaking study that identified the infectivity of the virus SARS-CoV-2 in humans did so using the cells that were isolated from Henrietta Lacks. Scientists began studying COVID-19 using HeLa cells, but soon found that the virus did not infect these cells well. This curiosity led the researchers to search for the key to viral entry that was apparently missing on the HeLa cells. Other forms of the coronavirus used a molecule, called ACE2, to enter the cells. ACE2 particles surround the surface of some human cells. Maybe the novel coronavirus also enters cells through the same molecule. After engineering HeLa cells to display the ACE2 molecule, the authors observed that the novel coronavirus could then enter and infect the cells (Figure 2). ACE2 acts as an entryway for any SARS-CoV-2019 particles to recognize and bind. After entry, it can use the cell’s machinery to replicate and spread, causing the novel coronavirus disease – COVID-19. Using HeLa cells, then, the researchers discovered an important aspect of SARS-CoV-2 infectivity and thus of viral spread.
Another study used HeLa cells as a tool to uncover the machinery required and process used for invasion of human cells. Researchers have also investigated the stability of the virus’s genomic material in HeLa cells by comparing its genomic material with that of many other viruses. The use of HeLa cells in COVID-19 research has provided insights on the molecular mechanics of SARS-CoV-2019 and the components required for infection. These data are pieces of information that come together to build a greater understanding of the virus, which is essential for developing future treatment.
A lasting contribution to the world
When Henrietta Lacks and her cells alerted the world to the existence of immortal human cells, opportunities arose for research and medical treatment development. Today, her cells continue to serve academic and industrial institutions. So much so that she has been described as the Mother of Modern Medicine in a painting by artist Kadir Nelson in 2017. The use of HeLa cells in COVID-19 research is a testament to Henrietta Lacks’s lasting contribution to provide microscopic tools for scientific discoveries that billions have benefitted from thus far and will benefit from in the future to come.
Noel Jackson is a second-year Ph.D. student in the Biological and Biomedical Sciences Program.
Daniel Utter is a 6th year Ph.D. student in Organismic and Evolutionary Biology at Harvard.
For more information:
- Stay up-to-date on the use of HeLa cells in biomedical research by visiting here
- Check out original research publications that use HeLa cells for COVID-19 discoveries here and here
- The Henrietta Lacks Family Foundation