[music] [a young girl rides her bike around a suburban cul-de-sac.] [narrator:] sandra stahl seems to be a normal healthy young girl. she can do everything her playmates do. [sandra's mother calling out:] sandra! [narrator:] but sandra is a child apart. she has leukemia. cancer of the blood. sandra's leukemia has been brought under control by continuous doctor care. [sandra and her mother walk into a hospital.] at regular intervals she and her mother go to the hospital where a sample of her blood is taken.
the white cells in the sample of blood are counted to make sure that the disease is still under control. [sandra's finger is pricked and blood taken.] some scientists believe that tiny particles called viruses, possibly hidden deep inside the blood cells, are involved in the onset of the disease. but can scientists prove that viruses are a cause of cancer? [machine sounds] and with that knowledge, develop a cure? [image of microscopic cells.]
thousands of scientists all over the world have been conducting research on the role of viruses in cancer. [scientists are shown working in their labs.] two of those scientists have been asked if it is now possible to prove that viruses cause cancer. dr. james grace, assistant director of the roswell park memorial institute in buffalo, new york, and dr. sarah stewart of the national cancer institute, discoverer of the polyomavirus. before these two scientists answer the question, it's important to understand something about viruses and about cancer. [close-up image of a cell.] cancer is a disease of the cells, the building blocks of which all living things are made. the rose, the robin, the rhinoceros.
the microscope reveals different kinds of cells that make up the root of a plant, or the muscle of a man, or the skin of an animal, but cells are more than building blocks; they're the very fabric of life. each cell is a biological machine designed to ensure its own survival and the survival of the organism of which it is a part. to study living cells, researchers grow them in bottles. [laboratory beakers and other equipment with cell material are shown.] each bottle is planted with healthy cells from normal tissue, making the bottle in effect a substitute for the man or animal from which the cells were taken.
to the bottle are added life-supporting chemicals and blood serum for food. these colonies of living cells are called tissue cultures. some colonies developed for research in the tissue culture section of the national cancer institute have survived in bottles for 25 years. the life processes of these cells can be recorded with time-lapse photography. [a scientist prepares a culture to be photograped, setting up equipment.] a motion picture camera takes a series of still photographs through a microscope at long intervals of time. events in a tissue culture bottle that normally take hours can be compressed into minutes. in time-lapse films, we see that cells, like higher animals, reach out for food, digest it, and eliminate waste. [cell division activity is shown.]
and they reproduce; they divide, producing exact duplicates of themselves. a simple yet wondrous process, by which the essence of the cell can be sustained for millions of generations, is a definition of life. but sometimes the life process is interrupted by agents of disease. for example, bacteria, which can be seen easily with the light microscope. it takes the electron microscope to reveal the smallest agents of disease known to man -- viruses. [a scientist peers into an electron microscope.] viruses are so small they can be measured in millionths of an inch. they are so elemental, they cannot reproduce without the help of a host cell,
yet they are potent agents of disease. [successive close-ups of virus cells are shown and described.] these viruses cause smallpox. other viruses cause tobacco mosaic disease in plants. these poliomyelitis viruses attack and destroy nerve cells in animals and humans. these viruses infect and destroy bacteria. is there a virus that causes cancer? what is cancer? time-lapse photography can show the effects of cancer on one living cell. a cancer cell, instead of producing normal daughter cells exactly like the parent cell, produces cells that are sometimes too large, too many, and in other ways irregular.
in other time-lapse films, by dividing the screen into two parts, normal and cancerous growths can be compared. on the right, normal cells are reproducing normally and in sufficient numbers to maintain normal growth. [a split-screen shows normal versus cancerous cells.] on the left, the cancerous cells are reproducing wildly, out of control. the cancerous cells are overlapping and piling up on each other, producing abnormal tissue. the result of cancerous growth is shown in these two still photographs of human skin. [a split-screen shows damaged versus healthy tissue.] in the photograph on the right, the cells near the surface of the normal skin are arranged in a normal functional pattern.
in the photograph on the left, the cancer cells have broken down the tissues and destroyed it. several factors have been frequently associated with the onset of cancer, like polluted air. city dwellers who inhale polluted air, and cigarette smokers, suffer a very high incidence of lung cancer, but why not all? [bomb sounds are heard and a mushroom cloud shown.] x-rays and gamma radiation can produce cancer. when atomic bombs were dropped on hiroshima and nagasaki, some survivors of the bombs were stricken with leukemia, but why not all? there must be another factor involved in leukemia and other cancers. perhaps the virus.
how do scientists prove that a virus causes disease? in plants, as in all living things, the traditional proof of the causation of disease follows three logical steps. [a man is shown in a laboratory filled with plants.] first, recovery of the suspected agent of disease from a sick host. this leaf has been infected by tobacco mosaic disease. [close-up of infected leaf.] the leaf, along with other infected leaves, is broken down in a laboratory solution, filtered to remove large materials, then centrifuged at precisely the speed which will bring down the leaf cells,
but leave the suspected agent of the disease suspended in the liquid above. over a period of days the liquid goes through many similar purification steps, [a centrifuge spins the plant material.] until only the concentrated suspected agents remain. in the second step, the researcher inoculates a healthy leaf with the suspected agent of the disease by rubbing it into the surface. if the new host gets the disease and the suspected agent is again recovered, the three steps of the cycle have been completed and we have proved that the disease is caused by the suspected agent, the tobacco mosaic virus.
[white mice are shown scrambling over one another.] in the same way, can we prove that viruses cause leukemia in mice? dr. sarah stewart will answer the question. [dr. stewart is shown in her lab.] [dr. sarah stewart:] following the traditional three step recovery-reinfection cycle, we take a mouse with spontaneous leukemia: large glands, a big spleen, and big liver. remove these cancerous organs, cut them into bits, and break them up in a standard solution. we know heat will affect viruses, so we keep our sample cold. to remove heavy cellular material, we spin the sample in a refrigerated centrifuge.
[dr. stewart carries out the steps as she describes them.] spinning at 4,000 revolutions per minute for 20 minutes breaks down the solid material and leaves the viruses, if there are any, in the apparently clear liquid. we filter the liquid to make doubly sure that we have removed all cells. with our cell-free tissue extract, we inoculate newborn mice. one of the reasons why we use mice for research is that they mature very rapidly and can be inbred to produce special characteristics. after 90 days, some of the mice which we inoculated show symptoms of leukemia. large gland, big spleen and big liver, the same symptoms of the disease in the original mouse.
finally, we try to recover the suspected particle and sometimes we try to substantiate our proof by photographing the virus in a sample of the tissue. to prepare our sample for electron microscopy, technicians fix it in a chemical, wash it, embed it in plastic, and bake the plastic for 24 hours. the specimen is then sliced to within a few millionths of an inch. [dr. stewart continues to demonstrate each step as she describes it.] the slices fall into a water bath, are teased apart by a brush with one or two bristles. [sound of heavy door sliding open.] the electron microscope is buried deep in the sub-basement away from all vibrations.
a tiny copper grid holding the slice specimen is placed in a special airtight holder, then slipped into an airlock. the barrel of the electron microscope is at a near-vacuum. inside, a gun shoots a beam of electrons through the specimen, painting a picture of it on a television tube where it can be viewed or photographed by the electron microscopist. after thousands of fruitless searches, the electron microscopists have finally found and photographed the very particle that we now know causes leukemia in mice. the photographs which magnify the particles hundreds of thousands of times show that the particles bud from the cell wall.
the center is made up of nucleic acid like the genetic material found in the cell. [cell images from the electron microscope are shown.] the coat is similar to the wall of the cell from which this made. the virus pinches itself off and slips into the spaces between the cells where it joins other virus particles which are ready to infect other cells, perhaps causing disease. we know that two or three particles sometimes join like siamese twins, but we don't know why, and there are other mysteries of the life and evolution of these virus particles, but we have proved that they can cause leukemia in mice.
but leukemia is only one form of cancer. many cancers are solid tumors. can we prove that viruses are involved in the causation of this parotid tumor? in order to demonstrate viruses in this particular tumor, we must increase the amount of the virus by packaging the tumor cells in tissue culture. we inoculate these flasks with extract from the tumor of our sick brown mouse, [dr. stewart use a long syringe-like instrument to inject the extract.] exposing the healthy normal cells in the tissue culture to the cancerous cells. we allow them to incubate for five to seven days...
again, at body temperature to simulate living conditions in a real animal. with the culture fluid, we can infect and cause disease in another healthy brown mouse which develops tumors of the salivary glands like those of the original mouse. when we look at the sections of these organs which have been placed on carefully prepared slides under another optical microscope, we see the typical evidence of cancer. sick cells with irregular shapes and big nuclei. biological proof; there is no longer any question that viruses cause cancer. not only leukemia but solid tumors in four-legged animals.
[narrator:] but what about the higher animals? the two-legged kind that plays in the sun? [doctor:] how have you been feeling? [sandra:] good. [doctor:] good. do you get tired very easily? [sandra:] yeah. [doctor:] her appetite has been fine? no troubles? [sandra's mother:] no. [doctor:] can i feel your tummy? i promise not to tickle. [narrator:] dr. james grace will answer the question:
can scientists prove that viruses cause human leukemia and other human cancers? [dr. james grace:] at roswell park memorial institute, part of our research program is devoted to the growth of human cancer cells and tissue culture. this one here is the granddaddy of them all. this is the first human leukemic cell line to survive in long-term culture. this was started in our laboratory in february of 1964. [dr. grace shows the vessel containing the cell line in a laboratory.] since then we have grown many other leukemic cell lines and we grow these in order to supply our own researchers,
as well as researchers in other laboratories around the world. we like to think that we are helping patients like sandra by treating her disease, but in a very real sense they are also helping us. when they first come to the hospital, we take samples of their blood, which is full of leukemic cells. these blood samples are then handled in sterile rooms to keep them as free as possible from other diseases such as that caused by bacteria. [the blood samples are handled and prepared for a centrifuge.] the blood samples are then processed by centrifuging them. this brings down the heavier red cells and leaves the leukemic cells in the liquid above.
one of the biggest problems has been to find the best chemical medium in which to grow the leukemic cells. we tried literally hundreds of different combinations of medium over the past three years. this one, the sixteen-hundred-and-fortieth one which we tried, finally worked. it contains 52 ingredients all carefully weighed, measured, and filtered. the medium is then bottled for distribution to the various tissue-culture labs in the institute. [the medium is handled and placed in vessels for distribution.] several flasks of medium are inoculated with small amounts of blood from patients like sandra. and a human leukemic cell line is then started, and hopefully it will grow long-term. quite a bit like a doctor making rounds of his own patients in a hospital,
i go around frequently and look at our leukemic cell cultures and see how they are doing. in the spinner lab, we try to increase the growth rate of the new cell line. [doctors pull vessel from spinner and examine it.] the spinner keeps the cells rolling through the medium by exposing them to the chemicals and oxygen in the same way that the bloodstream might expose them to natural nutrients. new cultures show only a few clumps of cells, but when they are a few days old they show larger clumps. to get even higher concentrations of white blood cells, we use a semiautomatic device which we have termed a [tropa cell?].
this solidly packed white culture that you see here, produced by the tropa cell, is almost pure leukemic cells. we can harvest as many as ten million leukemic cells per cubic centimeter of medium. we will soon have much larger tropa cells, which instead of the one quart flask, we will use 50-gallon drums for growing the cells. six of these large drums will be placed on this huge platform so that enormous quantities of human leukemic cells can be fed, kept in chemical balance, and harvested automatically. in the future, these vast quantities of cells might be used for vaccine.
at this time, the cells are kept in cold storage as much as 300 degrees below zero, for use by laboratories around the world interested in leukemia research. one of the samples of leukemic blood such as sandra's might finally help to resolve the question: do viruses cause cancer in human beings? we obviously cannot inject material from her blood into another child to find the answer, but we can and, in fact, do, send material in special cold storage containers to a research laboratory where this material is injected into animals which are very similar to humans--the monkey. [a monkey is shown in an animal research lab.] one of the largest animal programs ever devoted to the search for the cause of a disease is now being conducted
with national cancer institute funds at the biomedics research laboratory. [several incubators in a lab contain monkeys.] monkeys come to this nursery within minutes after they are born, before they develop either immunity to disease or any diseases themselves. like the human infant, they are weighed after birth, but unlike most human infants, they are rushed into a sterile environment. [monkeys chatter as a baby monkey is enclosed in a plastic bag and dipped into a vat of solution.] they enter this environment through a special lock that washes and decontaminates everything that must be passed into the isolator.
as quickly as possible, they are inoculated with cancerous cells from patients like sandra. they rapidly become the healthiest monkeys in the world. healthy because they live in a controlled environment with purified air at a constant temperature and humidity, and they get plenty of tender loving care. the nurses treat them as if they were their own children. and they also take a formula that any pediatrician would approve. [monkeys are fed with a bottle, held, and burped.] any hint of illness brings the vet running.
their temperature, pulse, blood pressure, and heartbeat are checked at regular intervals for any signs of abnormality. they are treated with kid gloves in the truest meaning of the word. for these monkeys may provide the answer to the question about human leukemia and viruses. from the sterile nursery, the young monkeys are then transferred to a sterile holding room. some of the monkeys inoculated two years ago are so far happy and apparently healthy, but if their disease follows a schedule like we would expect in human beings, like we have observed with other experimental animals, and if the materials with which they were inoculated, in fact, contained a cancer virus, then they should develop cancer at some point in their life.
if they do, we will then have completed the infection cycle in primates. the next step in the traditional proof would then be recovery of the viruses from the monkeys with malignant disease. this, however, is only one of many approaches. there are other bits of circumstantial evidence that viruses cause human leukemia. this evidence is found in studies in such fields as immunology and electronmicroscopy. at roswell park memorial institute, the electron microscope has demonstrated the presence of suspected viruses in human leukemic cells. [close-up image of a cell, rotating.]
[narrator:] but what about the questions raised today by people like sandra's mother, mrs. stahl? [mrs.stahl:] what progress has been made in taking care of it? i know a cure they say is impossible right now. they hope it will come someday. [doctor:] i think this has been one of the really bright spots in the management of malignant disease; for example, about 1949 when the first leukemic drug, anti-leukemic drug, was developed, the average time from diagnosis to death was about three months. in 1960, this has risen to about one year. now, at latest count just a few months ago,
the average was in excess of 28 months and climbing quite rapidly. [mrs. stahl:] i hear a lot of people wonder if it was contagious, or hereditary. [doctor:] based on our present knowledge, and this has been studied quite extensively, there is no evidence that leukemia has ever been contracted by contact. in other words, there's no evidence of contagion like one has, for example, mumps, measles, chicken pox. [mrs. stahl:] what is being done about it now? [doctor:] there's been a great deal of research into the cause of leukemia. now much of this has been based on animal studies, and one of the most exciting fields of leukemia research at present
is the possible role of viruses in the causation of leukemia. we know now that throughout the animal kingdom, many different animal species ranging all the way from the chicken upward, including cattle, dogs, mice, rats and so forth, that viruses can cause leukemia. more importantly, one can get these viruses and grow them in a laboratory. these, for example, that cause mouse leukemia, it is possible to prevent the leukemia by means of an immunization procedure. so this is very important from a practical standpoint in that if viruses can be shown to cause human leukemia,
it is wholly within the realm of possibility that one could develop a vaccine which would both prevent and possibly assist in the treatment of it. so the animal models are there. we're now waiting for the real breakthrough in human studies. if, in fact, viruses do cause human leukemia and since the human is a member of the animal kingdom, it would be very surprising to me personally, if he out of all the animals that we know were immune to viral causation of leukemia. [sandra stahl is shown pulling another child in a red wagon.] [narrator:] in the long struggle for final proof,
many scientists like dr. stewart and dr. grace believe that if viruses cause cancer in mice, they almost certainly cause it in monkeys and men. the proof will be an important step toward the development of preventive vaccines and possibly the long-awaited cure for cancer.
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