A question about cancer

[Zero]

In another thread, somebody said that one reason a doctor may be worse off due to religious beliefs is because cancer evolves. I may have misheard him, but this made no sense to me. Bacterial infections may have evolved to be resistant to pennicyllin, but I don't quite see how cancer could evolve to be less resistant to chemotherapy. I may be very wrong about all of this, but I was under the impression that cancer was usually something caused when a cell divided wrong, or something like that. I was under the impression that it was something that went wrong inside of you, not something that was ever outside of your body. Bacterial infections result from contact with something outside of your body, so I can see how such bateria can evolve, but cancer isn't something you catch, so why would it become resistant to our efforts against it? If anything, cancer that's more resistant to chemo would be more likely to kill off the person who had cancer, so shouldn't it evolve to actually be LESS resistant to cancer? Are my notions of what the hell cancer is complete bullshit? Was the claim that cancer evolves to become resistant to chemo bullshit?

[AMX]

Cancer cells reproduce rapidly.
Rapid reproduction means lots of errors that don't get corrected.
Lots of errors mean the cells are changing.
Just because the original cell was a part of your own body doesn't mean it's descendants have to be identical to it, and thus be susceptible to the same treatments.

The argument about killing the host is moot, since cancer is typically non-contagious, so no matter how long the host lives, the cells are eliminated anyway. And "right now", resistant cells have an advantage.

[Trytostaydead]

Actually, if anything, cancer cells de-evolve. They become primordial, undifferentiated, lose their abilities to receive signals and only know to replicate and consume.

[Lord of the Abyss]

I'm the the guy who said it, so let me explain what I meant.

Unlike normal cell, cancer cells have large genetic variations; they also reproduce quickly. Since they are no longer genetically identical, they are now in a genetic competition. The cancer cells that reproduce the fastest and evades the bodys defenses the best leaves the most offspring - evolution in action.

Suppose you add a poison like chemotherapy. Since cancer cells have genetic variation, some will be more resistant than other to the therapy. If you get them all, it does't matter - some just die a little slower. However, if some can survive, they will be the most resistant ones. They will reproduce, filling the void left by their less resistant relatives. Again, evolution in action.

Actually, if anything, cancer cells de-evolve. They become primordial, undifferentiated, lose their abilities to receive signals and only know to replicate and consume.

More accurately, they evolve in a new direction. Normal cells are clones. They act as one, with no self- interest or competition because they are identical. Once cells vary, they become individuals; if they continue mutating and reproducing they will evolve like any other organism. Normal cells don't evolve because they are copies; evolution requires variation.

Note on this; I'm a well read layman, NOT a doctor or biologist.

[tharkûn]

Cancer cells develop resistance just like bacterial cells do. Chemo drugs have to be delivered to the target cell, taken up, and then bound/metabolized in the appropriate manner to the target species (protein, DNA, RNA, etc.) and then proceed to block some vital function. All of these same steps occur with anti-biotics.

Take, for example, NTP analogues. In order for them to work they have to be delivered to the target cell, taken up, and bound to growing DNA strands. If a mutation in the cancer line causes the cell membrane to be less permeable than surrounding tissue to uptake then you get some resistence. If the DNA polymerase mutates to exclude NTP analogues and prevent them from binding growing DNA strands then you have resistence. Mutations in key genes alter the structure/function of key species and the drug no longer works. This is more or less the same process in developing bacterial resistence to anti-biotics.

More accurately, they evolve in a new direction. Normal cells are clones. They act as one, with no self- interest or competition because they are identical. Once cells vary, they become individuals;

Completely wrong.

First females. In human females there is a superflous X chromosome and after a short time one shuts down becoming a bar body. Which X shuts down is close enough to random it makes a good model to say it is random. Thus to neighboring cells will have different active genotypes and different phenotypes. As development continues after this event you end up with patches of cells with the same bar body bording patches of different cells with the other bar body. In a female heterozygous for color blindness this entials that some of the receptors in the back of the eye are going to be color blind and some aren't. This leads to diminished ability to see and differentiate color. The most classic trait is calico cats. Only females can be calico as the pigments are encoded on the X chromosome and the patches of color result from the differing bar bodies.

Second natural mutations. While most mitotic divisions result in clones the extremely small error rate in replication does give rise to differing cell lines. By the time you are born you have many different genetic lines running through the body. Likewise when you contract a retrovirus you cells are no longer clones, but still perform more or less in concert. The only difference in cancer is that certain control mechanisms have been obliterated; cancerous cells can have closer genetics to a healthy cell line than that line has to another healthy cell line.

[Trytostaydead]

Well, what you're stating is the Red Queen hypothesis applied to cancer. This is of course assuming that you have multiple cancer all over your body. It is interesting to note that one cancer can supress another.

Chemotherapy is the treatment of putting you to near death hoping it will kill the cancer cells.

Cancer cells become more undifferentiated than anything more resembling their progenitator state than what they were before. Cancer cells do not evolve, they're a dead end, they die with the person. The genetic "variation" is actually damage and error in a really bad spot to have it. It cannot progress in the evolution sense since ultimately it destroys itself.

[tharkûn]

Cancerous cells can be taken from the body and cultured indefinately. Some really wacky cancer cells taken from Henrietta Lacks in the early 50's are actually known to contaminate and overpower other cell cultures. These were given the name Helacyton gartleri but there is some disagreement upon this designation.

[Lord of the Abyss]

Completely wrong.

Fine, I oversimplified. Yes, the body has control mechanisms beyond genetic identity; normal cells lack the right kind/ level of genetic variation to overcome them. "Completely wrong" is an overstatement.

Cancer cells become more undifferentiated than anything more resembling their progenitator state than what they were before. Cancer cells do not evolve, they're a dead end, they die with the person. The genetic "variation" is actually damage and error in a really bad spot to have it. It cannot progress in the evolution sense since ultimately it destroys itself.

Just because cancer cell destroy themselves doen't mean they don't evolve. Evolution has no foresight; cancer cells simply overrun and destroy the body without realizing what they are doing.

Have you heard of HeLa cells ? They are a line of cancer cells that are sometimes considered to have become a new species; they actually adapted to life in a culture medium and spread wildly, ruining many scientific studies because the cells being studied had been replaced with HeLa.

Most cancer cell kill the body long before they can adapt to independent existence; that doesn't mean what they do is any less evolution.

[Lord of the Abyss]

Cancerous cells can be taken from the body and cultured indefinately. Some really wacky cancer cells taken from Henrietta Lacks in the early 50's are actually known to contaminate and overpower other cell cultures. These were given the name Helacyton gartleri but there is some disagreement upon this designation.

Arrgh ! Stop reading my mind !

[Trytostaydead]

Most cancer cell kill the body long before they can adapt to independent existence; that doesn't mean what they do is any less evolution.

But it's not a species undergoing mutations through generations. Its cells in your body that are really misbehaving that will most likely kill the host and is not passed down generationally except for certain inherited predisposition to certain cancers, all of which are not good for the host.

[Lord of the Abyss]

But it's not a species undergoing mutations through generations. Its cells in your body that are really misbehaving that will most likely kill the host and is not passed down generationally except for certain inherited predisposition to certain cancers, all of which are not good for the host.

Of course the changes are passed down, I'm talking about cancer cells, not the person. The mutations are passed down from each cancer cell to it's offspring.

The fact that it kills the host is irrelevant; most evolution results in destruction anyway. That's how it works; the well adapted survive, the less adapted perish. Cancer cells almost always end up dying because the leap from body cell to independent life is just to big.

[Trytostaydead]

I secede the point that it is microevolution but I do not know if it is evolution, does that make sense?

[Lord of the Abyss]

I secede the point that it is microevolution but I do not know if it is evolution, does that make sense?

No. "Microevolution" is a creationest buzzword. Evolution is evolution.

Besides, there isn't anything "micro" about cancer cells evolving; many have greater differences between them and normal cells than many species have. The HeLa cells I and tharkûn mentioned are a perfect example.

All something needs to qualify as evolution is a selection process between genetic variations; it doesn't matter if it happens inside a single body or not.

[Trytostaydead]

I secede the point that it is microevolution but I do not know if it is evolution, does that make sense?

No. "Microevolution" is a creationest buzzword. Evolution is evolution.

Besides, there isn't anything "micro" about cancer cells evolving; many have greater differences between them and normal cells than many species have. The HeLa cells I and tharkûn mentioned are a perfect example.

All something needs to qualify as evolution is a selection process between genetic variations; it doesn't matter if it happens inside a single body or not.

Actually, I was just quoting straight from Harrison's Internal Medicine

[Zero]

Thanks for clarification, Lord of the Abyss. Much appreciated.

[Lord of the Abyss]

Actually, I was just quoting straight from Harrison's Internal Medicine

How old a copy is it ? I've never heard the term used out of the "Creationism vrs Evolution" context.

If it's recent, they may have been contaminated. It's like the phrase "Survival of the fittest". Darwin never used it, and it's inaccurate; but the Social Darwinists used it so much it seeped into the language of scientists who should have known better. On the other hand, it could be left over from a more Christian dominated era in medicine.

Then again, as I said earlier I'm a well read layman, not a doctor or biologist. I could easily be wrong about a detail of jargon.

[Trytostaydead]

Actually, I was just quoting straight from Harrison's Internal Medicine

How old a copy is it ? I've never heard the term used out of the "Creationism vrs Evolution" context.

If it's recent, they may have been contaminated. It's like the phrase "Survival of the fittest". Darwin never used it, and it's inaccurate; but the Social Darwinists used it so much it seeped into the language of scientists who should have known better. On the other hand, it could be left over from a more Christian dominated era in medicine.

Then again, as I said earlier I'm a well read layman, not a doctor or biologist. I could easily be wrong about a detail of jargon.

Actually, microevolution is a common term in use in the sciences. My copy is the 16th edition, very new.

A lot of the cancers arise from multiple "hits." Meaning a somatic cell is hit multiple times in succession by mutations that alter specific mechanisms that puts the cells out of control and hence the description of "darwinian microevolution." Does the lack of controls make it more "fit" than its neighbors? Yes, in a sense meaning it can do whatever it wants for its own sake and some have the ability for angiogenesis (creation of new blood vessels to feed itself). Perhaps this is how the Borg 'evolved'?

[tharkûn]

Fine, I oversimplified. Yes, the body has control mechanisms beyond genetic identity; normal cells lack the right kind/ level of genetic variation to overcome them. "Completely wrong" is an overstatement.

Completely wrong is entirely correct. You stated:

Normal cells are clones.

They are not. Normal (non-cancerous) cells include ones with different bar bodies, the statisticly expected mutations under mitotic reproduction, retroviral genome changes, etc. Normal cells are ones with intact control mechanisms, clones are a completely different concept the while mostly true has no bearing upon cancer survival. Hell developmental abnormalities can result in fusion where COMPLETELY different genomes end up in the same organism and they still work togethor.

They act as one, with no self- interest or competition because they are identical.

More BS. Cells "act as one" because they have working control mechanisms. Being identical, which most cells in the female body aren't, has nothing to do with it. Further cells DO compete, for instance when there is insufficient oxygen in the blood cells show competive uptake, this is why the CNS tries to regulate blood flow at the systemic level under such conditions.

Once cells vary, they become individuals

They were ALREADY individual and many of them ALREADY varied yet still worked in concert. Quit anthrapomorphizing them, the only thing that makes a cell cancerous is the rate at which it divides, how "individual" it is happens to be irrelevent.

Cancer cells do replicate, mutate, and respond to selective pressure; however it isn't because they are individual nor because they stopped being clones. Frankly most cells replicate, mutate, and respond to selective pressure, cancer cells just do the first two so much faster and more often that it becomes easily noticeable.

[Darth Wong]

Actually, microevolution is a common term in use in the sciences. My copy is the 16th edition, very new.

It is and it isn't. It's used in the same sense that "micro-abrasion" is used in industry: as a term to describe small-scale instances of a particular mechanism. It is not, however, used in the creationist sense, since they believe that microevolution and macroevolution are totally different phenomena.