A cancer query

[EHLO]

A member of the family was diagnosed with cancer recently, the particular variety isn't important but it got me thinking about the disease in general.

Now as I understand it, cancer is caused by a mutation of the DNA within a cell that causes it to grow/multiply uncontrollably. Disregarding specific causes of these mutations, there is presumably some background rate of random mutation that causes (potentially) cancerous cells.

So this leads me to the disturbing realization that there are potentially cancerous cells occurring in our bodies all the time?

Is this true? And if so, what is the normal background rate of these mutations and how does the body normally deal with the cancerous cells - is there a natural immune response to these mutated cells? Are the common cancers we hear about (leukemia, skin, breast, bowel etc) just particularly successful mutations that evade the bodies natural defences?

This probably requires more investigation than I first thought but any info that may enlighten would be helpful. Know thy enemy etc...

Cheers,
EHLO

 

[fuelair]

This might help:
http://www.genetics.org/cgi/content/full/148/4/1483


This might also: http:/www.dogpile.com
In search (FETCH) window : mutations cancer cells human (hit FETCH)

From reading your item to return with info was e.t of app. 37 seconds.

Best,

 

[blutoski]

Two things:

1. Some cells have the mutation to begin with, but the gene in question may be dormant for years. What activates them is an area of study.

2. The immune system does ongoing tumour surveillance - we don't understand how. This is why people with a neutralized immune system develop cancerous lesions. How tumour surveillance works is an area of study.

 

[EHLO]

This might help:
http://www.genetics.org/cgi/content/full/148/4/1483

This might also: http:/www.dogpile.com
In search (FETCH) window : mutations cancer cells human (hit FETCH)

From reading your item to return with info was e.t of app. 37 seconds.

Best,

Play nice now - my grasp of biology and genetics is next to zero but I do understand the function of a search engine.

Your link is sort of helpful although is mostly over my head. It seems to be focussed on the elevated mutation rate of cancer cells and not the general prevalence of potential cancer cells in a healthy person - let alone if/why these potential cancer cells develop into the disease.

The top result from your search tip yielded this gem; www.cancerfightingstrategies.com/index.html which I doubt is of much use to anyone and indicative of my plight to find helpful information.

 

[EHLO]

Two things:

1. Some cells have the mutation to begin with, but the gene in question may be dormant for years. What activates them is an area of study.

2. The immune system does ongoing tumour surveillance - we don't understand how. This is why people with a neutralized immune system develop cancerous lesions. How tumour surveillance works is an area of study.

Thanks - lots of study to be done then eh?

So is it right to say that cancer cells are a normal part of the body, and that cancer as a disease only occurs when these cells get out of control?

Or do we just not know enough about it yet?

 

[Capsid]

Thanks - lots of study to be done then eh?

So is it right to say that cancer cells are a normal part of the body, and that cancer as a disease only occurs when these cells get out of control?

Or do we just not know enough about it yet?

Cancer cells don't exist until the mutation occurs, so it is not correct to say that cancer cells are a normal part of the body, however, all (?) cells have the potential to become cancerous given the right conditions. For example, melanoma occurs by transformation of normal skin cells through DNA mutation after exposure to UV radiation. Many viruses cause cancer too by transforming the DNA of the cells they infect.

 

[EHLO]

Cancer cells don't exist until the mutation occurs, so it is not correct to say that cancer cells are a normal part of the body, however, all (?) cells have the potential to become cancerous given the right conditions. For example, melanoma occurs by transformation of normal skin cells through DNA mutation after exposure to UV radiation. Many viruses cause cancer too by transforming the DNA of the cells they infect.

Ok, so what I'm trying to get at is if a skin cell mutates to a melanoma cell, does it always develop into full blown melanoma skin cancer, or is there a natural background of such mutations that the immune system fights off normally?

 

[Complexity]

I've been under following impressions, and can't back (some of) them up with any evidence:

1. That not all cancers are the result of mutation during the organism's lifetime.
2. That some organisms have a genetic predisposition to cancer development.
3. That cancers can arise many times in our lifetimes without our becoming aware of them. Most of these cancers are put down by our immune systems.
4. That our immune systems are generally very good at recognizing and killing off cancers, but that they can be flawed or become compromised and become less effective at these activities.

Corrections most welcome.

 

[aggle-rithm]

Ok, so what I'm trying to get at is if a skin cell mutates to a melanoma cell, does it always develop into full blown melanoma skin cancer, or is there a natural background of such mutations that the immune system fights off normally?

I get skin cancer a lot (basal cell carcinoma, relatively mild, not melanoma), and in most cases the cells are precancerous for years before becoming cancerous. When they're at this stage, they can be treated with topical cream.

The way these creams work, as I understand, is that they turn off the mechanism in the cells that tells the immune system "hey, I'm a healthy cell". The problem with skin cancer is that they are able to mimic healthy cells in this respect, so the immune system leaves it alone.

Anyway, the effect of the cream is to cause the area to become inflamed, especially where the precancerous cells are. The inflamed cells die, nipping the cancer in the bud.

I'm not sure if this answers your question. I know there are doctors that believe that cancer cells exist in your body all the time, and that the immune system is usually able to keep them under control. However, it depends on how well your genetic "error checking" system is working. Those with poor error-checking are especially prone to cell mutations/cancer, putting an extra strain on your immune system.

 

[aggle-rithm]

I've been under following impressions, and can't back (some of) them up with any evidence:

1. That not all cancers are the result of mutation during the organism's lifetime.

True -- childhood cancers are thought to be caused by leftover embryonic cells that don't know they are supposed to stop their explosive growth. Brian Piccolo of the Chicago Bears had this type of cancer, so apparently they can stay dormant in the body of an adult for years before causing a problem.

2. That some organisms have a genetic predisposition to cancer development.

That's the "error checking" mentioned above. There's a genetic disorder that causes children to start developing skin cancers almost immediately upon being exposed to the sun, which is caused by a deficiency in error-checking. I don't remember the name of the disorder, but it causes sufferers to become disfigured early in life.

Caveat: These are likewise just impressions that are not backed up with immediate evidence, just more detailed. I could look it up if necessary.

 

[aggle-rithm]

Thought I should mention this, as it's a annoying bit of woo that makes the rounds occasionally:

It's said that cancer can be cured by "mind over matter", since all the cells in the body (except some neurons) replace themselves over a few years, so there's no reason for cancer to be a problem. We can simply wish it away.

Unfortunately, although it's true that cells are continually replacing themselves, if it were always a "fresh start" with vibrant, new cells, we would never get old. The new cells are copies of the old cells, with previous copying errors intact.

Slightly off-topic: There's also decrementation of the "suicide gene", which loses part of its information with each cell division. After a preset number of divisions, the cells can no longer copy themselves. Interestingly, deactivating this gene seems to cause cancer for some reason.

 

[casebro]

Yes, cancer is happening all the time within our bodies. That leads to the downside of 'full body scans'. Seems the scans find small nodules that have no effect on us, and that the body has under control. These innocuous nodules are called 'incidentalomas'. Of no consequence, except to cause panics in the patients.

 

[Tumbleweed]

My predisposition at this time is that cancer does indeed pop up all the time, whether from rest or just all of a sudden. Its growth depends on its ability to fool the immune system and get the blood steam to provide it with nutrients, just like any other cell. So it's growth is a function of an individual's immune systems smarts. A sort of cat and mouse game is being played
Another very odd theory is that there are two kinds of cancer cells: selfish and magnanimous. Cancer cells are supposed to commit suicide for the benefit of the whole. If they have a self preservation attitude instead, they trick the body, get nutrient channels established and tumors therefore grow. And the weirdness grows because it is theorized that the cancer cells attitude mirrors your own

 

[Tumbleweed]

I am very angry with my government because they apparently are suppressing cancer research for political reasons
My sister develpoed and died from aggressive breast cancer after going through the mill with treatment: chemotherapy, surgery and radation. Now I learn 2 years after the fact that seemingly reliable medical experiments have been conducted that show an ingredient in marijuana not only prevents at least several tpes of cancer from metastisizing, but also shrinks tumors, specifically lung and breast tumors. These studies were recently done in Europe and were reported by various medical journals. Then I learned that the US had done the same tests decades ago, the results apparently repressed during the War on Drugs
If we had known about it, we might have at least attempted to use marijuana as a therapy for my sister. It never crossed our minds to go that route. Sure we had heard stories about how pot helps the appetite of people on chemotherapy, but new types of medicine now do the same, so we never considered it for that either
Given her outcome, what did we have to lose by trying it?

 

[quarky]

sharks don't get cancer.

 

[fuelair]

I've been under following impressions, and can't back (some of) them up with any evidence:

1. That not all cancers are the result of mutation during the organism's lifetime.
2. That some organisms have a genetic predisposition to cancer development.
3. That cancers can arise many times in our lifetimes without our becoming aware of them. Most of these cancers are put down by our immune systems.
4. That our immune systems are generally very good at recognizing and killing off cancers, but that they can be flawed or become compromised and become less effective at these activities.

Corrections most welcome.

Your list looks fine to me (prostate cancer survivor!!)

 

[Capsid]

sharks don't get cancer.

You were being sarcastic?

http://www.internationalskeptics.com/forums/showthread.php?t=83879&highlight=shark+cancer

 

[fuelair]

Play nice now - my grasp of biology and genetics is next to zero but I do understand the function of a search engine.

Your link is sort of helpful although is mostly over my head. It seems to be focussed on the elevated mutation rate of cancer cells and not the general prevalence of potential cancer cells in a healthy person - let alone if/why these potential cancer cells develop into the disease.

The top result from your search tip yielded this gem; www.cancerfightingstrategies.com/index.html which I doubt is of much use to anyone and indicative of my plight to find helpful information.

Actually, when I am not playing nice I don't use smileys! But although the overall article was about the cancer cells, several of the points were about normal cells chance of becoming cancerous. This is the biggie of those (part of third para after the summary):
Assuming that a similar fraction of cells in other tissues is stem cells, and that the average stem cell undergoes 100 divisions during a human lifespan, then the cellular target size for mutagenesis is approximately (2 x 1014 cells per adult) (0.002%) or 4 x 109 cells. Thus, there is present in individuals more than enough stem cells that contain a sufficient number of mutations to account for the two-hit mechanism proposed by KNUDSEN, in which both alleles of a cancer-causing gene must be inactivated. Based on a Poisson probability distribution in which mutations are independent events, the average stem cell would accumulate 1 to 2 mutations. As many as 2 x 106 cells could contain as many as 6 mutations, and a few cells (3) could contain as many as 12 mutations (Table 1). If each of the cells with multiple mutations were able to proliferate continuously and form a tumor, then spontaneous mutation rates could account for the 6 to 10 events (mutations) that are predicted to be rate-limiting for tumor formation, based on the increase of cancer incidence with age (ARMITAGE and DOLL 1954 ). In this analysis, we assume that any mutation in any gene is on the pathway toward malignancy, that any stem cell has the potential to become a tumor, and that each of the mutations are rate-limiting for the development of a malignancy. If we restrict the analysis to mutations in cancer-associated genes, then the spontaneous mutation rate can account for as many as 8 x 103 stem cells containing as many as 2 mutations, and only a few cells (5) containing as many as 3 mutations.
This is definitely about amount of cells that may mutate (statistically) and therefore may lead to cancer during a normal lifetime. It is not tissue specific and an implication of it is there are not that level of estimates available (not certain, not my field) for specific tissues/cancer types.
NOTE: The sentence that begins "In this analysis" notes a very important assumption - that Every mutation is on the path to malignancy. That is, of course, possible but.....

 

[EHLO]

Actually, when I am not playing nice I don't use smileys! But although the overall article was about the cancer cells, several of the points were about normal cells chance of becoming cancerous. This is the biggie of those (part of third para after the summary) ...

Thanks for clarifying - perhaps I should have used a smiley myself but I was getting frustrated with searching and either getting buried in academic terminology or alternative nonsense.

The paper taught me a lot, but I couldn't quite relate the bit on stem cells to what I was looking for. My poor biology knowledge is letting me down, so I couldn't see the relationship between the stem cells they base their assumptions/calculations on and, say, skin cells which presumably divide much more than 100 times in a lifetime and thus have a far higher mutation rate.

Also, I couldn't tell if the "6 to 10 events (mutations)" correlated with cancer rates in the general population - which would answer the question as to the number of background "potential" cancerous mutations versus the number that actually develop into cancer.

 

[EHLO]

I get skin cancer a lot (basal cell carcinoma, relatively mild, not melanoma), and in most cases the cells are precancerous for years before becoming cancerous. When they're at this stage, they can be treated with topical cream...

Sorry to hear that - doesn't sound too pleasant! Thanks for all your information.