“Today it's possible for scientists to immortalize cells by exposing them to certain viruses or chemical, but very few cells have become immortal on their own as Henrietta's did.” – Rebecca Skloot

It’s time for my lab’s annual Secret Santa galore! For a week everyone plays pranks on their designated victim – ahem, I mean – Santee. The flurry of shenanigans culminates at the final lab meeting of the year where everyone receives gifts from their Secret Santa and guesses who had harassed them the weeks leading up to Christmas. Last year my Secret Santa (whom I correctly identified) gifted me the New York Times Bestseller The Immortal Life of Henrietta Lacks, written by Rebecca Skloot, a freelance science writer. 

Although Henrietta Lacks was not a scientist, she unknowingly contributed significantly to the biomedical world. Born into an African American family in Virginia in 1920, Lacks was raised on a tobacco farm and lived in impoverished conditions. 31 years later, she felt a lump inside her cervix and went to Johns Hopkins Hospital to get it checked out. Henrietta thought she was pregnant; however, her doctor dismissed such assumptions after performing a biopsy that confirmed she had stage I cervical cancer. She was treated with radium tube inserts sewn into her cervix (sounds dreadful!), a standard practice at that time. Unfortunately, the cancer had metastasized (spread) throughout her body, and on October 4, 1951, Henrietta Lacks passed away at the age of thirty-one. 

Interestingly, during one of Henrietta’s visits to Johns Hopkins, a hospital resident had taken a separate sample of Henrietta’s tumor to give to George Gey, a researcher at Hopkins. Gey was on a mission. He had been experimenting endlessly to create an immortal human cell line - a group of cells that could divide forever under normal lab conditions. 

To Gey’s amazement, Henrietta’s cells could live indefinitely outside the body and multiply like crazy. The cells adhered to the sides of test tubes, voraciously consumed the medium around them, and in just a few days, layers of cells formed in the petri dishes (plastic cylindrical dishes used to culture cells). After two decades of failed attempts at making an immortalized human cell line that could be used to study the mechanisms of cancer, George had finally struck gold. He decided to give away vials of these cells for free with other researchers (they later became commercialized by companies), and soon many labs around the world had vials of HeLa (Henrietta Lacks) cells stocked in their freezers. Currently, no one knows exactly how many of Henrietta’s cells are circulating – a scientist has estimated that there are a whopping 50 million metric tons of them!

Cells growing in petri dishes filled with media. The cells grow in an incubator kept at 37 degrees.

Ok, let’s pause here. I just want you all understand where and how cells used in research are handled and maintained. For long-term storage, cells are frozen down along with special liquid in cryogenic plastic vials and kept in liquid nitrogen freezers (around -125°C to -196°C). When a researcher wants to use them for experiments, they will thaw the vial for a few minutes in a warm water bath and then grow them on petri dishes containing liquid media (= cell food). Scientists must ensure that these cells remain uncontaminated and healthy. This is achieved by carefully working with the cells inside tissue culture hoods, as shown below, which have a special ventilation system known as laminar flow that blows out dirty air, leaving clean air circulating inside the hood.  

Before and after use, the hood must be wiped down with ethanol, which "denatures" or alters the molecular structure of bacterial proteins, to maintain a sterile environment. Having bacteria float around in your precious cell samples is every scientist’s worst nightmare! Also, every few days one must take some cells out from one dish and transfer them to a new dish with new media. This dilution is necessary so that cells in the older dish don’t overcrowd and start competing with each other for the cell food. This is pretty much what I do every day in my lab! Ok, now back to the HeLa story.

Left: Exterior of 37⁰C incubator where cells are grown in petri dishes. Right: Tissue culture hood, where experiments on cells are performed in order to prevent contamination from the outside environment.

In addition to HeLa cells, other immortalized cell lines do exist. To this day, it is not really known why HeLa cells keep growing. HeLa cells have an overactive telomerase (an enzyme that adds DNA sequence repeats to the ends of telomeres, which protects the end of the chromosome from destabilizing or fusing with neighboring chromosomes during cell division). This hyperactivity prevents the shortening of telomeres that is inherent of aging  and eventual cell death. As such, HeLa cells circumvent the Hayflick Limit, the limited number of cell divisions that most normal cells can undergo before senescence (biological aging). 

Additionally, scientists know that Henrietta’s cervical cancer was caused by Human Papilloma Virus (HPV), so some think that the multiple copies of HPV DNA combined with a region in Henrietta’s DNA to cause the cells to grow out of control (HeLa cells have a whopping 82 chromosomes! Humans normally have 46). Also, Henrietta had syphilis, which can suppress the immune system and cause cancer cells to grow even more rapidly. But many people have had HPV and syphilis and their cells weren’t able to grow at a crazy rate like the HeLa cells. Henrietta continues to perplex us!

Research using HeLa cells was crucial to the development of the polio vaccine, as well as drugs for treating herpes, leukemia, influenza, hemophilia, and Parkinson's disease. It has also helped understand the mechanisms of cancer and the effects of the atom bomb, and led to important advances like cloning, in vitro fertilization, and gene mapping. Additionally, in the past ten years, research involving HeLa cells has garnered five Nobel Prizes. Check out the timeline of HeLa research below (Click the link in the caption for a magnified view).

Image from Wired magazine. http://www.wired.com/magazine/wp-content/images/18-02/st_henrietta_f.jpg

A few weeks ago, the Graduate Student Book Club discussed The Immortal Life of Henrietta Lacks. It had been a while since I had read the book, so I skimmed it to prepare myself for talking about literature and history from a scientist’s viewpoint over some tea and cookies.

A number of issues were discussed at the Book Club, which were more ethical than scientific. I could go on and on about everything that deals with these topics, and that’s why I’ll stop here to spare you guys from reading a super long post. Stay tuned for part II of the HeLa saga!