In February 1951, Henrietta Lacks, a thirty-year-old mother of five, went for an examination at the John Hopkins hospital after noticing blood stains on her underwear. Doctors were quick to conclude that she had most likely contracted cervical cancer. To confirm their diagnosis they took a sample of her tissue and had it analyzed. The news was anything but encouraging: the tumor contaminating the cervix turned out to be malignant. In October the same year, after only a few months’ struggle with the disease, Henrietta Lacks died.
Immortal cells of a dying patient
Even though Henrietta and her family could not have realized this fifty years ago, her body’s life had not ended yet. Some of Henrietta’s cells are alive even to this very day, more than half a century after their owner’s death. They are being carefully grown in numerous laboratories across the world and have even reached outer space after being sent into the orbit on a satellite, enabling researchers to observe the effect of zero gravity on cell growth. In fact, if we were to weigh all Henrietta’s surviving cells together, they would probably largely exceed the weight of her entire body fifty years ago.
The fascinating journey of Henrietta’s cells began in 1951 when a part of her tumor’s tissue was sent to the laboratory of Otto Gey, a researcher at John Hopkins University who had been striving for decades to find a solution to growing human cells in a laboratory in order to facilitate cancer research. He struggled for a long time to find a solution, but cells simply refused to grow and divide in an artificially created environment. That was until he came across the cells from Henrietta’s tumor and decided to try using them.
Miraculous HeLa cells
Even after several days in an artificial culture medium, Henrietta’s tumor cells continued to divide successfully and there was no indication of them ageing and dying as samples had in all previous experiments. Gey named them after his patient: HeLa cells. He concealed the identity of his donor with great care and it was only revealed after his death.
However, as rapidly as HeLa cells multiplied in Gey’s laboratory in 1951, they also spread inside Henrietta’s body. Even though the patient died only half a year after her first visit to the hospital, the very cells that did her so much harm were soon helping to save many other lives.
In the 1950s a vaccine for polio was developed with the help of HeLa cells. They have gone on enabling an abundance of research up to the present and have led to the discovery of many important facts about life and the workings of the human body.
Immortal cell lines
Henrietta’s cells were the first to be successfully grown in laboratory conditions and later used to create an “immortal cell line,” the term used for cells which can – in an appropriate environment – continue to divide outside the body without aging. In normal circumstances, cells may only divide for a limited number of times (ten or more) before losing this ability and slowly dying.
Cell death after a certain number of divisions was in fact what stopped Gey from creating an immortal cell line from normal cells in the human body. It was only Henrietta’s cells that displayed an ability to divide indefinitely. That was because they lacked the mechanism responsible for ceasing uncontrolled multiplication. Its inactivity failed to trigger cell death when HeLa cells had reached the normal threshold for duplication.
Cell aggression beats the competition
As HeLa cells turned to be very useful in numerous researches, Gey simply mailed them to colleagues all across the world so they too could grow them and use them in their work. Soon, other scientists reported that they too had created their own immortal lines of human cells. However, it soon turned out that these so-called new lines were really just a form of Henrietta’s cells. They were found to be highly aggressive, capable of infecting other cell cultures and eventually eliminating the competition even when applied in extremely small doses.
In 1972, for example, Russian scientists sent their American colleagues six different lines grown in various parts of the former Soviet Union, but it was discovered that all of them were actually HeLa cells. Americans did not prove any more successful either: in 1968 34 lines were tested of which 24 were identified as Henrietta’s cells.
Growing patient cells
As scientists perfected the methods of growing human cells and cells of other mammals in laboratories, they quickly began to wonder whether it was possible to create immortal lines for specific individuals as well. Organ transplantation always entails a risk that the immune system will reject a transplanted heart or liver. Doctors try to overcome this by prescribing special medications which transplant patients must take regularly for the rest of their lives and by seeking genetically compatible donors for organ recipients. A transplant is performed only if this match is close enough, since only then can drugs be of any use should the patient’s system reject the organ.
Transplants using donated organs always entail large problems and high risks, so researchers started to think how they might grow healthy cells from a failing organ in a laboratory and reinsert them into the patient later on. This would prevent the risk of a rejection of foreign tissue, as the artificially grown cells would not differ in any way from those already in the patient.
Today, skin and bone marrow-growing therapies are already available. A sample of cells is taken from the patient and multiplied in sufficient amounts in a laboratory only to be transferred back into the patient later. However skin-growing can prove to be particularly difficult, taking several weeks to produce enough for transplantation, which might already be too late for those with heavily injuries.
Cells adapt to specific tasks
Another problem in growing cells from various tissues of the adult human body is that cells can only divide a limited number of times. Sooner or later the process comes to an end or the cells produced do not respond to our needs.
Even though the genetic code of every cell contains all the information it requires for development, most of the cells that make up an adult body have already lost the ability to use the entire code. In the environment of a specific organ, cells adapt to perform a specific task and this adaptation is usually irreversible.
When a cell takes on a function within a blood vessel, or in the heart, the skin or the nervous system of an individual it cannot “change its mind” and take on a different role. Scientists have not yet figured out what exactly happens within a cell when it adapts to a specific task, but the fact remains: a part of its genetic code is shut off for good.
The mother of all cells
However, not all the cells within the human body have this one-way limitation in terms of their function. Those that have the ability to develop into other types are called stem cells. Their main characteristic is the capacity they have of developing into more specialized cells. Bone marrow, for example, contains special stem cells which are capable of producing red blood cells to transport oxygen throughout our bodies. Similar stem cells that can produce other specific cells have also been found in various organs.
The capability to develop into any of several hundred cell types within the human body is possessed only by the very young stem cells that can be found in the first days following fertilization, in embryos made up of only some ten cells. These are called embryonic stem cells and only they have the rare property of developing into any cell type in different environments.
Immortal stem cell lines
Another important feature of embryonic stem cells is that they can be used to create a cell line. If grown correctly, they can multiply indefinitely without growing old and dying after some ten divisions, as is usually the case with already differentiated cells such as skin or bone marrow cells. The first line of human embryonic stem cells was created in 1998 in the US.
Today, several hundred exist in the world. In the US, however, following President George W. Bush’s decree, public research funds can only be used on the 22 lines created before the beginning of his mandate in 2001. This issue is once again gaining in importance since the president vetoed the Act of Congress that would have approved the continuation of federal funding for this important and vital scientific field.