Scientists regularly cultivate human cells as in-vitro cultures to study how they function, understand how diseases affect us and test new possible cures and vaccines without jeopardizing the patient’s life.
However, it is an undeniably tedious and complex process and requires the results obtained to be capable of replication in order to ensure that the results are constant, correct and verified. For this, scientists needed a huge population of identical cells derived from humans, which have the ability to divide indefinitely and stay immortal.
But this was impossible – or so was the assumption established initially, and with plentiful legitimacy.
The Hayflick Limit was the empirical evidence that after each time a cell undergoes division, the telomeres in the DNA gets slightly shorter until it reaches a critically minute length and has lost the ability to divide. This was scientific evidence that no cell line could ever go on dividing forever!
To add to the hurdles tagged along the discovery of Apoptosis- proving that all cells have a definite life time and limit on how much they can divide-after which the cell will have to die. Since apoptosis cannot stop once it has begun, it is a highly regulated process. Apoptosis can be initiated through one of two pathways. In the intrinsic pathway the cell kills itself because it senses cell stress, while in the extrinsic pathway the cell kills itself because of signals from other cells. This helps prevent genetic errors that occur after repeated rounds of division. A usual human cells has the ability to divide up to about 50 impressive times before it self-destructs. But this is not the case with cancer cells. They overrule the signals from other cells and keep dividing indefinitely. Even so, they fail to make an exception in the cause since they do eventually die, especially under insufficient or inappropriate in-vitro care.
But we would not be talking about hurdles if they didn’t have a solution.
In the funny year of 1951, Dr Gey of Pennsylvania received a sample of tumor cells from a patient suffering from Cervical Cancer, Henrietta Lacks. It was unprecedented. Henrietta Lacks’ tumor cells divided indefinitely and seemed immortal! He sent these samples to all over the world, shocking scientists and paving the way for ground breaking medical researches and breakthroughs.
The questions as though answered themselves with another. The golden ‘how’ remained.
Before I begin to decode the answer, let’s stroll through the basics and establish some ground facts. ‘HeLa’ cells – as they were named – were derived from the tumor mass characterising the cervical cancer of Henrietta. HPV (Human Papillomavirus) is responsible for causing it. Apoptosis in HeLa cells is inhibited by 2 inhibitory proteins produced by the cell; these inhibitory proteins target retinoblastoma tumor-suppressing proteins (The retinoblastoma protein (pRb) is a tumor suppressor protein that is dysfunctional in several major cancers. One function of pRb is to prevent excessive cell growth by inhibiting cell cycle progression until a cell is ready to divide). These tumor-suppressing proteins regulate the cell cycle, but are rendered inactive when bound to an inhibitory protein. HPV E6 causes p53, a gene that codes for a protein that regulates the cell cycle and hence functions as a tumor suppression, to become inactive. HPV E7 binds to retinoblastoma tumor suppressing proteins and limits its ability to control cell division. These two inhibitory proteins are partially responsible for HeLa cells’ immortality by inhibiting apoptosis to occur.
Telomerase, a protein that keeps repairing the telomeres in the DNA and help cancer cells prevent destruction was first discovered in HeLa cells.
This cell line empowered scientists to develop cures and vaccines to diseases that were established invincible, a century ago. The world’s first cell production facility began rapid production of 6 trillion HeLa cells a week and scientists put them to work in an ethnically problematic way, building careers and fortunes off of Henrietta’s cells, without her family’s consent or even knowledge, until decades later. Soon they found application in anti-cancer, flu and Parkinson’s disease cure development.
Before the eyes could believe the pace of application and investment, HeLa cells became the first to ever be cloned.
In fact, the polio epidemic was at its very peak in the 1950s, but with the discovery of HeLa cells, scientist Jonas Salk was able to test a vaccine that revolutionarily prevented polio by replication the virus with the HeLa samples.
I’ll answer this ‘how’ quicker than before.
When Jonas Salk developed a vaccine, he needed to test it on a huge scale to ensure its safety. These tests involved the inoculation of 2 million children. Afterwards blood samples from the children were mixed with cultured cells and the poliovirus. Prior to HeLa, Salk used monkey cells in his tests. However, the cells died in the process, making the tests extremely expensive. These tests, directed by the National Foundation for Infantile Paralysis, required a more economical cell line. Gey donated Henrietta’s cells, which could grow very rapidly at a low cost. It was discovered, too, that HeLa cells were easily affected by the poliovirus, making them all the more suitable for testing (Skloot 93-95). Because of HeLa cells, large samples of the polio vaccine could be tested and countless lives were saved.
Ironically, HeLa cells have also helped develop a vaccine for cervical cancer, and are still used today for researches on diseases like AIDS. Kinda like your karmic cycle, innit?