26 replies to this topic

[Lazarus Long]

While this only relates to a few human cancers but the model described may be applicable for an alternative way of inserting a transcripted sequence while supressing an immune response because the result is nonfatal.

Contagious Canine Cancer Spread by Parasites

By Charles Q. Choi, Special to LiveScience
posted: 10 August 2006 10:34 am ET

Dogs have a form of sexually transmitted cancer that for 200 to 2,500 years has apparently spread via contagious tumor cells that escaped from their original body and now travel around the world as parasites.

These cells are the oldest cancers known to science thus far, and could shed light on how cancers survive and evade the immune system.

The researchers investigated canine transmissible venereal tumor, a cancer found in the domestic dog and potentially in relatives such as the gray wolf and coyote. It is spread through sex and licking, biting and sniffing cancerous areas. The tumors usually regress three to nine months after their appearance, leaving the dogs immune to reinfection, although providing enough time for dogs to pass the disease on.

Some human cancers, such as cervical cancer, are caused by viruses.

What is unique about this dog cancer is that, for 30 years, scientists have suggested it was caused by spreading the tumor cells themselves rather than a virus or other contagious agent. Prior research showed, for instance, the disease could not spread from tumor cell extracts or dead tumor cells, but only via living tumor cells. Still, virus-like particles seen in the tumor cells clouded the issue.

Cancer researcher Robin Weiss at University College London and his colleagues analyzed genetic markers in recently collected and archived tissue from dogs spanning five continents, from locales in Italy, India, Kenya, Brazil, the United States, Turkey and Spain. They found the tumor cells did not actually belong to the dogs they were in. Rather, the cells were all genetically nearly identical, apparently stemming from a wolf or a closely related ancient dog breed from China or Siberia.

The tumor cells themselves act as parasites, the new study concludes.

The researchers found the cancer secretes compounds that inhibit facets of the immune systems of their hosts, allowing them to avoid detection. At the same time, the immune inhibition they cause rarely results in death of the infected animal, to help guarantee the host passes the disease on.

Judging by the number of mutations the cancer's DNA accumulated, the researchers estimate it emerged 200 to 2,500 years ago. Instead of becoming progressively more genetically unstable over time, as scientists widely supposed happens to cancer, these cancer cells "do not go on getting more and more genetically unstable," Weiss told LiveScience.

The study is detailed in the Aug. 11 issue of the journal Cell.

[olaf.larsson]

Fantastic!!!!!!!! This is the first example I hear of where cells from a mature animal have become a living organism of their own.
#################################################

Now here is something so bizarr, and scary that one would hope that is some kind of bad science fiction:

http://www.livescien...ii_culture.html

Study: Cat Parasite Affects Human Culture

A parasitic microbe commonly found in cats might have helped shape entire human cultures by manipulating the personalities of infected individuals, according to a new study.
Infection by a Toxoplasma gondii could make some individuals more prone to some forms of neuroticism and could lead to differences among cultures if enough people are infected, says Kevin Lafferty, a U.S. Geological Survey scientist at the University of California, Santa Barbara.

In a survey of different countries, Lafferty found that people living in those with higher rates of T. gondii infection scored higher on average for neuroticism, defined as an emotional or mental disorder characterized by high levels of anxiety, insecurity or depression.His finding is detailed in the Aug. 2 issue of the journal for Proceedings of the Royal Society, Biology. Manipulating behavior T. gondii infects both wild and domestic cats, but it is carried by many warm-blooded mammals. One recent study showed that the parasite makes normally cautious rats outgoing and more prone to engage in reckless behavior, such as hanging around areas frequently marked by cat urine, making the rats easy targets.

Scientists estimate that the parasite has infected about 3 billion people, or about half of the human population. Studies by researchers in the Czech Republic have suggested T. gondii might have subtle but long-term effects on its human hosts. The parasite is thought to have different, and often opposite effects in men versus women, but both genders appear to develop a form of neuroticism called "guilt proneness." Other studies have also found links between the parasite and schizophrenia. T. gondii infection is known to damage astrocytes, support cells in the brain that are also affected during schizophrenia. Pregnant women with high levels of antibodies to the parasite are also more likely to give birth to children who will develop the disorder.

In light of such studies, Lafferty wondered whether high rates of T. gondii infection in a culture could shift the average personality of its individuals.
"In populations where this parasite is very common, mass personality modification could result in cultural change," Lafferty said.
The distribution of T. gondii could explain differences in cultural aspects that relate to ego, money, material possessions, work and rules, Lafferty added. In some countries, infections by the cat parasite are very rare, while in others nearly all adults are infected.

Adding to cultural diversity

To test his hypothesis, Lafferty looked at published data on cultural dimensions and average personalities for different countries. The countries examined also kept records of the prevalence of T. gondii antibodies in women of childbearing age. Countries with high prevalence of T. gondii infection also had higher average neuroticism scores
"There could be a lot more to this story," Lafferty said. "Different responses to the parasite by men and women could lead to many additional cultural effects that are, as yet, difficult to analyze.".

Lafferty thinks that climate could be an important factor in determining which human populations are infected by T. gondii. The parasite's eggs can survive longer in humid, low-altitude regions, especially at mid latitudes that have infrequent freezing and thawing. Other factors could also influence infection rates, including how a culture's attitudes about having cats as pets and the hygiene practices of its people.

!!!!!!!!!!!!!!!!!!
Despite its association with neuroticism, Lafferty doesn't think all of the cat parasite's effects on human culture are bad.
"After all, they add to our cultural diversity," he said.
!!!!!!!!!!!!!!!!!!

Edited by wolfram, 11 August 2006 - 11:49 AM.

[olaf.larsson]

More about this intressting subject which I want to puke when I think about...

http://www.livescien...echnovelgy.html

[Lazarus Long]

I did see that article on the feline parasite influencing human behavior and even more importantly culture. I find it interesting as well but did not have the time to post it, however it is not the same thing as a virus that mimics parasitic behavior to enhance its transmission potential.

It is important though to understand that we are still finding modes of disease that are ubiquitous and due to their *non fatal* characteristics can result in more subtle impacts, like large scale behavioral change in this case.

I am reminded of the Rye Ergot hysterias of the Middle ages.

However the question I am posing Wolfram is: does this offer a new way of creating a model for gene insertion that can suppress immunity in a less catastrophic manner for the patient while accomplishing the genetic modification throughout the body?

Apparently this canine virus has that ability as well so a close study of its genome will reveal a mechanism that can suppress human immunity in a reversible non lethal manner that is not dependent on drugs.

[jaydfox]

Check this out!
http://www.washingto...6081001535.html

Scientists in England have gathered definitive evidence that a kind of cancer in dogs is contagious -- a peculiar exception to the age-old medical wisdom that you can't "catch" cancer.

...

But the dog cancer, known as Sticker's sarcoma, is spread by tumor cells getting passed from dog to dog through sex or from animals biting or licking each other.

...

Weiss and his colleagues did genetic studies on the tumor cells from 40 dogs with Sticker's sarcoma, collected from five continents. The researchers showed that the cells are not genetically related to the dogs they are in -- proof that they did not arise from the dogs' own cells.

They also showed that all the tumor cells, no matter where they were collected, are clones of each other. That is, they are all progeny of the same parent cell.

Further genetic studies by Weiss's team suggested that the parent cell probably arose in a domesticated dog of Asian origin -- perhaps a husky -- hundreds of years ago, and perhaps more than 1,000 years ago. Since then, the cancer has perpetuated itself by jumping from one dog to another.

Studies suggest that, unlike most tumor cells, which contribute to their own demise by becoming increasingly genetically fragile, Sticker's tumor cells are remarkably genetically stable, perhaps explaining in part their evolutionary success.

...

You should read the whole thing, and maybe even look for more info on the web, or even the study itself. But I've extracted interesting tidbits.

[jaydfox]

Hmm, before other people bring up things like cervical cancer in humans, spread by a virus... From the article:

A cancer cell is usually an animal's or person's own cell that -- because of exposure to a virus or other environmental agent -- has broken free of normal growth controls. Cancer-causing viruses may spread from person to person, but the cancer does not.

The cancers reported in this study are not spreading by a secondary agent like a virus: the cancer cells themselves are the infectious agent.

[Lazarus Long]

When I used the subtext of an infectious cancer in the title of the same topic and article here:
http://www.imminst.o...&t=11939&hl=&s=

My point was to outline the mechanism of transmission and to some extent, while I agree that the specific *cancer* is not being transmitted, the *causal agent*, that is viral, is contagious. In fact the tumors could not be spread by dead tumor cells but according to the article they can be spread by live tumor cells.

It is not only contagious but the mechanism of its contagion is interesting in itself, and the added factor that it is able to insert an immunosuppressant gene into the host for the duration of its infection BUT it is temporary and apparently nonlethal.

They also showed that all the tumor cells, no matter where they were collected, are clones of each other. That is, they are all progeny of the same parent cell.

I also find it amazing that we are dealing with one virus that has spread itself globally through what amounts to a cloning mechanism and is not in itself mutating significantly.

[advancedatheist]

I recall hearing of a case where someone acquired melanoma from a transplanted organ. Apparently the donor didn't know he or she had this cancer. Makes you wonder if melanomas can also hitch rides in blood tranfusions.

[bgwowk]

I also find it amazing that we are dealing with one virus that has spread itself globally  through what amounts to a cloning mechanism and is not in itself mutating significantly.

You of course mean cell, not virus. Also, "clone" in this context means same cell division lineage, not cloning as in nuclear transfer. It's just ordinary cell division.

Also, Mark, don't forget that transplant recipients are on immunosuppressive drugs so they don't reject foreign cells.

[Lazarus Long]

Correct on my slip Brian, I did mean to quote tumor cell and not virus. None the less we are talking about a global spread, a few thousand years and they are still considered progeny of the original cell by a mechanism that relies on keeping the host alive for contagion.

Second, it is the ability to act as an auto-immune suppressant that I personally find most interesting about the issue. Here we have a tumor cell that not only usurps the host's genome for spreading the tumors but does not mutate over thousands of years, has a secondary mechanism that acts to suppress immunity in the host without killing them, and apparently is reversible after a given period of infection.

What is unique about this dog cancer is that, for 30 years, scientists have suggested it was caused by spreading the tumor cells themselves rather than a virus or other contagious agent. Prior research showed, for instance, the disease could not spread from tumor cell extracts or dead tumor cells, but only via living tumor cells. Still, virus-like particles seen in the tumor cells clouded the issue.

Cancer researcher Robin Weiss at University College London and his colleagues analyzed genetic markers in recently collected and archived tissue from dogs spanning five continents, from locales in Italy, India, Kenya, Brazil, the United States, Turkey and Spain. They found the tumor cells did not actually belong to the dogs they were in. Rather, the cells were all genetically nearly identical, apparently stemming from a wolf or a closely related ancient dog breed from China or Siberia.

The tumor cells themselves act as parasites, the new study concludes.

The researchers found the cancer secretes compounds that inhibit facets of the immune systems of their hosts, allowing them to avoid detection. At the same time, the immune inhibition they cause rarely results in death of the infected animal, to help guarantee the host passes the disease on.

Judging by the number of mutations the cancer's DNA accumulated, the researchers estimate it emerged 200 to 2,500 years ago. Instead of becoming progressively more genetically unstable over time, as scientists widely supposed happens to cancer, these cancer cells "do not go on getting more and more genetically unstable," Weiss told LiveScience.

The study is detailed in the Aug. 11 issue of the journal Cell.

Edited by Lazarus Long, 11 August 2006 - 10:57 PM.

[chubtoad]

So can we think of this cancer as being alive to the same extent a virus is alive? Or perhaps moreso since the tumor cells are themselves alive?

[jaydfox]

Heh, oops, I missed this. I posted a duplicate of sorts, here:
http://www.imminst.o...ST&f=44&t=11951

[Lazarus Long]

Actually what is important is that the original tissue of the first tumor cells continues to replicate after hundreds to thousands of years. What they are saying is that the tumor cells do not have the genome of the current host but the *original* host.

This is an example of what is seen in the lab where cancerous tumor cells can violate Hayflick's limit on the number of reproductions. The individual tumor cells die but the genes continue to survive and reproduce. In this case moving from one host to another and using them to reproduce as a form of parasitic behavior.

It might be very interesting to study this mechanism to see how it is recycling the mtDNA and why telomere shortening is not fatal to the original germline.

These are not the original cells but the tumor still contains the original genotype, that is why it is considered a form of *clone* reproduction.

Werewolf bite transmission? [wis]

)

[manofsan]

Las, but what if you compare to bacteria, which also replicate in a stable way. Any unstable offspring might just die by the wayside anyhow.

[Lazarus Long]

But bacteria are daughter cells and would not be considered exact clones of the original cells as much as buds. The point here is that the tumor cells show the DNA signature of the *ORIGINAL HOST* not the presently infected one so they are hitching a ride the way viruses do and that is why it is parasitic. However they are not like a virus in the way they simply hijack the host DNA and replicate a tumor cell using the primary DNA of the current host modified with only the mutation to produce tumor cells inserted in by the virus.

The issue is relevant for longevity because technically speaking cells carrying DNA of the original host, from possibly thousands of years ago are still alive and reproducing. Also all instances of this disease trace back to the same single donor from all over the world.

In essence the original wolf (canine) DNA could even possibly be extracted from the tumor cells and cloned into a copy of the very same wolf in which the disease originally formed. This tumor cell hijacks current host cell reproduction but inserts an immunosuppressant that allows it to keep the DNA of the original host during reproduction and not get rejected. So it must be replacing the entire nucleus of the current host in those cells.

BTW, the mechanism that is accomplishing this could be a significantly better method of immunosuppression than current drugs for tissue and organ transplants.

It is also probable that the tumor cells are stealing mtDNA from the host during cell replication but if not then the tumor cells have not only overcome the Hayflick limit for telomere shortening but also can reset many of the mtDNA cumulative mutations. I would be very curious if the mtDNA of the tumor cells reflects the current host or the original one?

I think this is a study that should get shared here and more closely scrutinized.

Edited by Lazarus Long, 13 August 2006 - 12:20 AM.

[manofsan]

I'd like to know if these tumor cells have to maintain a certain minimum rate of profligacy in order to maintain the chain of immortality.

In other words, if one of these cancer cells was not able to clone itself, how long would it be able to survive as an individual?

[Lazarus Long]

In other words, if one of these cancer cells was not able to clone itself, how long would it be able to survive as an individual?

Good question but I suspect from the description that the individual tumor cells have a *normal* lifespan. After all the disease is non lethal and the current victim eventually builds an immunity so they can eventually kill off the invading genome.

So in all likelihood these cells are replicating like *normal* (mortal) cancer cells. They likely have a standard life cycle and that is why I suspect they reflect what we see of cancer cells in the lab that can overcome the Hayflick and replicate ad infinitum in the lab. The individual cells are not immortal but the *germ line* technically is.

[manofsan]

Good question but I suspect from the description that the individual tumor cells have a *normal* lifespan.  After all the disease is non lethal and the current victim eventually builds an immunity so they can eventually kill off the invading genome.

So in all likelihood these cells are replicating like *normal* (mortal) cancer cells.  They likely have a standard life cycle and that is why I suspect they reflect what we see of cancer cells in the lab that can overcome the Hayflick and replicate ad infinitum in the lab.  The individual cells are not immortal but the *germ line* technically is.

But are they immortal even if they're unaffected by the Hayflick limit? I mean, are their mitochondria okay?
You'd have to compare a cell and its 200th-generation-removed daughter, and see if the daughter is just as good as the original progenitor.

Furthermore, the human body can't sustain some rapidly-reproducing cancerous rate of proliferation. I'd like to know if it's possible to overcome the Hayflick limit with cells that have a more leisurely rate of reproduction. The faster your cells are duplicating, the more likely it is that something will go wrong. You guys have said that one of the reasons a youthful growing body is so healthy is that its rapidly reproducing cells are multiplying faster than the rate of accumulation of metabolic junk.

Either we find a way to do the immortality without the high rate of multiplication, or else we come up with a rapid rate of apoptosis to keep even with a high rate of multiplication.

[bgwowk]

Given this discovery one must wonder how many other tumors could be similarly parasitic and if it is possible that some derivative of this process (which could infiltrate the stem cell pool of the host including the germline) enables a type of non-sexual genetic exchange and/or propagation.

The human genome is full of code for endogenous retroviruses, although most of it is left over junk code for viruses that lost replicative capacity eons ago because of point mutations.

http://en.wikipedia....nous_retrovirus

We are living repositories of a history of viral infections in our species and its predecessors going back millions of years.

[Lazarus Long]

But are they immortal even if they're unaffected by the Hayflick limit? I mean, are their mitochondria okay?
You'd have to compare a cell and its 200th-generation-removed daughter, and see if the daughter is just as good as the original progenitor.

I agree and said as much above. I think this study raises a lot of questions and that is why I felt it worth looking more closely at.

Personally I suspect that the nDNA of the original cell line is hijacking cytoplasm in the cells of the current host and thus stealing its mtDNA. If so that would conform to calling this a form of cloning as the tumor accomplishes its survival by inserting its whole genome into the current host and replacing the hosts nDNA in the affected cells.

This is conjecture however and without reading the original study I can only assume that someone will if they haven't already be seeking the mechanism for how mitochondria are utilized. However in the tumor tissues sustained in the laboratory for decades there does appear to be a mechanism that cancers can employ to overcome the limitation.

The mitochondria remain functional for tumor metabolism though I do not know if the mutation rate is stopped or ignored in these cells.

Furthermore, the human body can't sustain some rapidly-reproducing cancerous rate of proliferation. I'd like to know if it's possible to overcome the Hayflick limit with cells that have a more leisurely rate of reproduction. The faster your cells are duplicating, the more likely it is that something will go wrong. You guys have said that one of the reasons a youthful growing body is so healthy is that its rapidly reproducing cells are multiplying faster than the rate of accumulation of metabolic junk.

There are many questions to ask here. I am not suggesting this is a form of *immortality* at all, what I am saying is here is a disease that mimics some of the characteristics we are interested by a heretofore unknown mechanism and does so by targeting systems and genes that we are also interested in manipulating.

This cancer helps locate genes we need to know about, demonstrates they can be manipulated, and offers a mechanism to study as to how. Altering how they are to be manipulated is another matter but one step at a time.

Also I have not been convinced all along that we need to be so fanatic about keeping fidelity to the mtDNA we are born with. I think this offers an alternative where a host cells mtDNA can be adapted. Isn't that what happens in an organ transplant now?

The donor tissue cells never lose their original DNA signature for either their cell nuclei or their mtDNA correct?

Yet the organ functions as long as it is not rejected. In addition to the other aspects of this disease it appears to be able to target immune suppression in such a manner so as to intentionally NOT disable it completely thus ensuring its own transmission to another host.

[judas1969]

If cancerous cells can replicate themselves without number, why then can we not find a way to control the "idea" of Cancer and control it. Our cells can replicate only about 45 times. Cancer cells are similar in nature to stems cells. Would it not be suprising to find one day that the key to simple physical immortality or regeneration of dying cells to be found in our worst enemy? Could cancer be the thing that leads us to life everlasting (in the current physical sense?)
Judas1969

[stephen]

But the dog cancer, known as Sticker's sarcoma, is spread by tumor cells getting passed from dog to dog through sex or from animals biting or licking each other.

This is kind of scary. Doing the singles scene might be more dangerous than I thought... You and your partner can be tested for STDs, but who knows how many latent cancer cells are floating around.

Now, where did I put my plastic bubble?

[judas1969]

Papilloma virus, is a human STD known to cause cancer. Thankfully, there is now a vaccine. It is possible that some other forms of cancer ARE contagious, AND easily transmitted, and take a long time to show themselves. There are no vaccines for many contagious diseases, a prime example being HIV. Yes, we could be spreading cancer to one another, somehow.
My earlier question, concerning cancer cells being immortal is on a different tack. Each time a cell replicates, it loses a piece of Telomerase, ultimately leading to cell death, and the dead cell sort of floats around (the junk). Cancer cells replicate themselves rapidly, and with no limit, and no Telomerase chain attached WHAT MAKES THEM DIFFERENT? If we (humanity) could learn to control this wild growth and use it to our advantage, we really could reverse the aging process (provided there is also a way to rid ourselves of the old dead junk left behind).

[judas1969]

In reply to the comment by Lazarus Long (Read a little Heinlen perhaps?), yes one step at a time. Question- If cancer is a disease that starts out without its own cells, and is simply hijacking a healthy cell, replacing its genetic information, and then cloning itself over and over- again, maybe this is a process by which we could (instead of cloning Dolly the human sheep), clone little bits of ourselves, within our own bodies to replace the already damaged cells (to be fresh and shiny and new). Kurzweil suggested that nanomachines could go in and create strings of amino acids and make DNA/RNA, but I don't see any around yet. I am a Californian, and not a particularly right wing one, I wish sometimes my government was more open to medical advance instead of religious political advance. If you are correct, then stem cells are just that- cells, not a hijacking, cloning predator virus (cancer) that just wants to replicate itself as many times as possible. I wonder if I will live to an age where reason prevails, and life can succeed and survive.

[judas1969]

To Prometheus- If retroviruses (HIV for instance) are able to radically alter the structure of DNA, once again, couldn't we use that same weapon for the good? We already change genetic codes using viruses. We remove the destructive instructions in the virus and add productive good ones. Could we not do the same with retroviruses? Is cancer a retrovirus in disguise? We know it can be transmitted.