--and colds, and warts, and flu, and measles, and..............
The best-known tumor virus in man is the virus that causes warts. This was first demonstrated to be infectious in 1894, and was clearly shown to be due to a virus in 1907, and there is still neither a cure nor a vaccine for it. More recent work has shown that it is a DNA virus; the virus itself is made up of the same type of material as our genes. Warts generally go away by themselves, and are also known to respond to almost any treatment.
S.L.Clemens describes several treatments for verruca vulgaris(warts). I have abstracted his 1875 paper as follows:
1. Aqua spunkae (spunk water): This reagent is collected in the forest and is an eluent of rotten stump. For the most effective therapeutic use it is necessary to apply it at midnight with the following injunction: "Barley-corn, barley-corn, Injunmeal shorts, Spunk water, spunk water, swaller these warts." Following the injunction it is necessary to leave the locale by taking eleven steps with your eyes shut and then turning around three times and walking home without speaking to anybody. "Because if you speak the charm's busted."
2. The Bean Method: "You take and split the bean, and cut the wart so as to get some blood, and then you put the blood on one piece of the bean and take and dig a hole and bury it, 'bout midnight at the crossroads in the dark of the moon, and then you burn up the rest of the bean. You see, that piece that's got the blood on it will keep drawing and drawing, trying to fetch the other piece to it, and so that helps the blood to draw the wart, and pretty soon off she comes."
3. Dead Cat in Graveyard Method: "why, you take your cat and go and get in the graveyard 'long about midnight when somebody that was wicked has been buried; and when it's midnight a devil will come, or maybe two or three, but you can't see 'em, you can only hear something like the wind, or maybe hear 'em talk; and when they're taking that feller away you heave your cat after 'em and say, "Devil follow corpse, cat follow devil, warts follow cat, I'm done with ye!" (This method has been attributed to H. Finn.)
Modern authorities feel that the Aqua spunkae should be applied two drops at a time for five days after meals. The injunction should be repeated at each application. With regard to the split bean method, only the bean Phaseolus vulgaris will do, and cross incisions should be used on the wart. With regard to the cat in the graveyard method, there is considerable disagreement as to whether the cat must be black, or whether it should be a male or a female. There is little question about the efficacy of the above treatments provided, of course, that the patient has confidence in both the physician and the treatment.
So cancer can be caused by viruses --big deal! That statement is true, but it is only the first step in understanding what is happening. We know that colds, cold sores, influenza, measles, and so on, are all "caused by viruses," but such a statement really asks more questions than it answers. The problem of virus-animal interaction is the problem of life itself, and is immensely intricate, Volumes have been written about it, and the field is still in its infancy. To hear some virologists talk it's "Plug virus into cell; wait 3.25 days, harvest virus, immunize mouse with virus, add virus-induced cancer cells and voila! immunity, cure, Nobel Prize!"
The way that cancer viruses act is somewhat different from the way that disease viruses act. In virus disease, the virus attacks cells and either destroys or incapacitates them. When viruses cause cancer, they appear to do the opposite. Instead of destroying the cells, they stimulate their continued survival.
Almost everyone is familiar with the lack of predictability of virus infections. The very same influenza virus can have no effect on one member of a family, make another member just slightly out of sorts, and make a third member of the family seriously ill.
Most of us harbor the virus of a cold sore (Herpes simplex), but when the disease erupts depends on many factors. Some people break out in cold sores under certain types of emotional stress and some break out in sores when they develop a fever. My particular bete noir is a spot on my chin that breaks out every time my face gets exposed to a lot of sunlight.
The same complex picture exists with the so-called oncogenic (cancer causing) viruses. There is a leukemia virus in some strains of mice that breaks out and causes leukemia in response to x-ray; another oncogenic virus, polyoma, doesn't ordinarily seem to do too much in most mice; but when it is souped-up in tissue culture it can cause large numbers of tumors in mice that were injected with it at birth (if the mice are injected with it as adults, they develop a typical immunity and do not develop tumors).
There is a good deal of difference between different strains of mice as to whether they will grow or pass on a virus. Whether a particular virus that causes breast cancer in mice will grow depends upon the genetics of the animal it is injected into. If what is true between strains of mice also applies to man, then we can expect a wide individual variability in susceptibility to tumor viruses.
The more we know about viruses, the more complex the picture becomes. We now know that the breast cancer virus in mice is actually two agents; with one agent being passed in the egg, and the other in the mother's milk. The story about the discovery of the breast cancer virus (mammary tumor virus) in mice is an interesting one and bears repeating:
In the 1920s C.C. Little examined the pedigrees of mice reared and studied by Maude Slye. He found that the inheritance of breast cancer did not obey the usual laws of heredity. He and William Murray made crosses between mice of high cancer strains and low cancer strains. If the mother was of a high breast cancer strain and the father from a low .breast cancer strain, the offspring developed a large amount of breast cancer; while if the father was of the high cancer strain and the mother from a low breast cancer strain, the offspring did not develop breast cancer. They theorized that there must he something that is passed to the young through the mother, but not through the father, and that it could not be a gene. This so-called extra-chromosomal factor could only be passed in one of three ways: through the egg, through the placenta, or through the mother's milk. The problem was too large for one person to solve, so it was split, and two possibilities were explored. Elizabeth Fekete explored the possibility of transmission through the egg, and in doing so, invented ways of transplanting eggs from one mouse to another, and John Bittner tested the possible transmission through the milk. Bittner lucked out: The virus was transmitted through the milk of the mother. What makes this even more phenomenal, is that the virus is, to date, the only one that we know of that is transmitted through the milk of the mother. Bittner received the credit and the applause, and the other workers went back to the drawing boards. It is interesting that what is now called the "Bittner virus" could very easily have been the Fekete virus. Another sidelight to this work is that, based on the discovery of this virus, many people came out against breast feeding; stating that breast cancer could be wiped out if we could have one generation of bottle-fed babies. Unfortunately, there is no real evidence that a breast cancer virus is transmitted in human milk, and there is some evidence that early pregnancy and nursing might help to prevent breast cancer in the mother. It is a classic example of the danger of drawing conclusions before all of the information is in.
This "Bittner Virus" is one of the tumor viruses about which we have a good deal of information (perhaps more than any other tumor virus). An index of how complex the problem is can be gained from the following well established information: The virus enters the mouse through the milk at the time that it is nursing. There is no apparent effect of this virus until the animal is about three months old, when a rare mouse will develop detectable changes in its mammary glands, and rarely a tumor. The changes are related to the hormones in the animal and can be induced by injecting hormones. The mouse has ten breasts, if you can call them that, and it's a matter of chance as to which breast will develop the first breast cancer. If the nipples are blocked on one side of the animal (an old experiment performed by Elizabeth Fekete at the Jackson Laboratory in Bar Harbor, Maine), more breast cancers develop on that side. Most of these tumors look about the same through the microscope, but the growth rate of each one is different. The tendency to metastasize to the lung is also different from one tumor to another. The age at which the tumors appear in the animals is different from one animal to another. The rate at which the tumors appear in the animals increases with the age of the animal. The transplantability of each tumor is different. If anyone can explain all of these things with a simple model, he will deserve the Nobel Prize, but no one has yet, and it seems unlikely that anyone ever will. If life were that simple, it would not have taken billions of years for it to evolve to its present state.
When a virus enters a cell and produces a tumor, it places its signature on the cell surface. Every cell of a virus-produced tumor has on its surface, and in its nucleus, a detectable protein characteristic for that particular virus. Tumors produced by chemicals are all individuals, and appear to have no such signature in common, indicating that they are not induced by one, or even two viruses. This doesn't bother me, but it is somewhat disconcerting to those who seek a single viral cause for cancer.
So, to say that "viruses cause cancer" is about as enlightening as saying that the ocean has fish in it. We are still little more than guessing about how viruses do what they do. There is lots left to understand. As for a cancer virus vaccine, we have to first find the cancer virus that we are going to vaccinate against, or else what is being done is little more than witchcraft.
So far, only one virus has been clearly implicated as causing a form of human cancer. This is the virus which causes Burkitt's lymphoma. Another virus reported as being related to a rare form of cancer is the virus of mumps. A high percentage of men who have developed tumors of the testicle were found to have had a history of mumps infection of the testicle. A prospective study has never been done. In fact, these findings have all but been ignored by the people working with viruses and tumors.
I scratch my wart while pondering the virus problem; with a cold sore on my lip and a running nose. All three of these viruses have been my intermittent companions for at least twenty years. Someday, one of the viruses may make friends with some of my cells; and then who knows what will happen?