By the time Henrietta Lacks, a Black mother of five, died of cervical cancer in 1951 at the age of 31, she had already achieved a sort of immortality.

Without her knowledge, Lacks’s doctor at Johns Hopkins Hospital, George Gey, had harvested cells from a tumor on her cervix, where her cancer proliferated, and was attempting to keep them alive outside her body. Gey figured he could cure cancer if only he had a line of cells that could reproduce indefinitely. Typically, human cells do not survive long once they have been severed from the organism they belong to: they will divide no more than about 50 times, then die through a process called apoptosis. For some reason, her cells, later labeled HeLa, just kept dividing. In the decades after this breakthrough discovery, HeLa cells have become a staple in scientific research. Biotech companies have reaped profits, all without consulting or compensating the Lacks family. Her descendants have been in a protracted fight to right a historical wrong all too common in the harsh reality of medical racism.

This week, the Lacks family won one battle. Thermo Fischer Scientific reached a confidential settlement with the Lacks family on Tuesday. The family had filed a lawsuit in October 2021, accusing the company of unjust enrichment or illegally commercializing Lacks’ genetic material.

Here’s what you need to know about Henrietta Lacks’ cells or HeLa cells and why they remain crucial for medical research today.

What makes HeLa cells so special?

The answer has to do with particular mutations in her cells caused by the human papillomavirus that had infected them. HPV inserts its own DNA into that of the host, resulting in a genetic hybrid. Not all HPV infections lead to cancer, and not all cancer has the potential to be an immortal cell line, but Lacks’s specific mutations had at least two characteristics that made her cervical cells special.

For one, HeLa cells are prolific dividers. Gey was surprised at just how quickly his cultures doubled in number. Even among cancers, these cells were reproductive superstars.

Secondly, they have an enzyme called telomerase that is activated during cell division. Normally, it is the gradual depletion of telomeres — a repetitive strand of DNA on the ends of the chromosomes — that stops cells from dividing indefinitely. But active telomerase rebuilds telomeres cut during division, allowing for indefinite proliferation.

HeLa cells are not the only immortal cell line from human cells, but they were the first. Today new immortal cell lines can either be discovered by chance, as Lacks’s were, or produced through genetic engineering.

HeLa cells are not the only immortal cell line from human cells, but they were the first. Today new immortal cell lines can either be discovered by chance, as Lacks’s were, or produced through genetic engineering.

Genetically, HeLa cells contain parts of Henrietta Lacks’s own DNA, mutations introduced by the strain or strains of HPV that infected her, as well as uncounted numbers of new mutations introduced organically through cellular division after the original cells were harvested from her body. A normal human cell has 46 chromosomes — HeLa cells tends to have between 70 and 90.

According to some scientists, the HeLa cell line should properly be considered its own species. It is a sort of single-cellular organism that reproduces asexually through division and evolves through mutations that compound over time. It is a domesticated species, though, dependent on humans for food and shelter.

From cancer to space

The cells have been a boon to biomedical science. They give researchers a way to conduct repeatable experiments on human cells without testing directly on humans, although the cells are arguably no longer human at all.

The contributions have been innumerable. Since the 1950s, HeLa cells have made strides in cancer research and treatments, notably in uncovering the connection between the human papillomavirus (HPV) and cervical cancer. (This connection earned its discoverer, Harald zur Hausen, a Nobel Prize in 2008.)

In the 1960s, HeLa cells were used to test the efficacy of a new drug for sickle cell anemia, hydroxyurea, which is still used to this day.

HeLa cells have been pivotal in vaccine development against viruses like HPV and polio. In 1953, Johns Hopkins researchers discovered they could use these cells like factories to grow large amounts of the polio virus to better understand how it infects cells and causes disease. This eventually laid the groundwork for polio vaccines, a marvel of modern medicine that has prevented roughly 1.5 million childhood deaths around the world since 1988, according to the Centers for Disease Control and Prevention.

Speaking of viruses, our understanding of how the human immunodeficiency virus (or HIV) infects its host — and subsequent anti-viral therapies — is thanks to HeLa cells.

HeLa cells have even been to a frontier most of us have yet to visit: space. During the 1960s, these immortal cells piggybacked on space missions to see how human cells react to radiation and zero gravity.

The story of the woman who non-consensually gifted HeLa to the world was largely unknown for decades after her death, even as the cells themselves contributed to significant advances in medicine. That changed thanks to The Immortal Life of Henrietta Lacks, a book that chronicles the efforts of author Rebecca Skloot to find Lacks’s family and tell her story. The HBO movie starring Oprah Winfrey is based on that account.

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