Isotypes and Heath
March 18, 2011 4:39 AM Subscribe
Cancer Knowledge: With the recent radiation fears in Japan, how does radiation cause cancer? Also, looking for an expert here - given the huge investments towards cancer research, how far away are we from a cure? Or is it not so simple?
I'd like to chime in and say that a "cure for cancer" is like a "cure for pollution." There are many kinds of cancers and many kinds of pollution.
posted by sciencegeek at 4:44 AM on March 18, 2011 [3 favorites]
posted by sciencegeek at 4:44 AM on March 18, 2011 [3 favorites]
This blog post by a surgical oncologist is a great starting point to understanding the nature of cancer.
posted by neushoorn at 4:47 AM on March 18, 2011 [2 favorites]
posted by neushoorn at 4:47 AM on March 18, 2011 [2 favorites]
Radiation is highly energetic particles or electromagnetic waves. This energy allows reactions to happen that otherwise would not be possible. For example some atoms can be knocked out of molecules in the body.
If the radiation cause major damage the cell dies immediately, this is what causes acute radiation sickness. But if it only cause minor damage in the DNA sequence, or damage in molecules that in turn cause minor mutations the cell might survive and eventually start multiplying causing a tumour.
posted by furisto at 4:57 AM on March 18, 2011 [4 favorites]
If the radiation cause major damage the cell dies immediately, this is what causes acute radiation sickness. But if it only cause minor damage in the DNA sequence, or damage in molecules that in turn cause minor mutations the cell might survive and eventually start multiplying causing a tumour.
posted by furisto at 4:57 AM on March 18, 2011 [4 favorites]
Basically, all cells are programmed to die eventually. If something goes wrong in this process, the cell can lose control of the cell cycle. Radiation can cause a mutation in the cell cycle, causing it to become essential "immortal" and keep multiplying forever - which is cancer. (Mutations in the cell cycle actually occur all the time btw, but they are usually fixed by error checking mechanisms. But it only needs one important one to get through and you're in trouble. Reassuring huh?)
There are various other ways cancer occurs too, and because all the mutations are different, there can't be one cure for them all. Most treatments we have at the moment are tissue specific - so the treatment for lung cancer isnt the same as the treatment for stomach cancer, for example. This is why when cancer has spread throughout the body its more difficult to treat, because you usually have to figure out the "original" tissue source.
So there won't be one single cure, we'll need lots of treatments for each type of cancer. And it's probably still a way off, unfortunately
posted by stillnocturnal at 5:08 AM on March 18, 2011 [4 favorites]
There are various other ways cancer occurs too, and because all the mutations are different, there can't be one cure for them all. Most treatments we have at the moment are tissue specific - so the treatment for lung cancer isnt the same as the treatment for stomach cancer, for example. This is why when cancer has spread throughout the body its more difficult to treat, because you usually have to figure out the "original" tissue source.
So there won't be one single cure, we'll need lots of treatments for each type of cancer. And it's probably still a way off, unfortunately
posted by stillnocturnal at 5:08 AM on March 18, 2011 [4 favorites]
Also, looking for an expert here - given the huge investments towards cancer research, how far away are we from a cure?
A major complication is that there is no one, single cure. What consists of a loosely-defined tumor can be made up of many subtypes of cancerous cells, not all of which are guaranteed to respond to one therapy. Killing off a few of the cell subtypes within the cancerous population gives other, more therapy-resistant cancerous cells within the tumor room to grow, which can narrow the remaining options for downstream treatment.
Further, the boundary between host tissue cell types within an organ is not cleanly and identically distributed. An individual organ (liver, heart, etc.) is like a sandwich of various cell subtypes. As a result, there are fewer options for "silver bullets" that can hit the target while leaving the surrounding tissue intact. This, too, complicates treatment.
posted by Blazecock Pileon at 5:26 AM on March 18, 2011 [1 favorite]
A major complication is that there is no one, single cure. What consists of a loosely-defined tumor can be made up of many subtypes of cancerous cells, not all of which are guaranteed to respond to one therapy. Killing off a few of the cell subtypes within the cancerous population gives other, more therapy-resistant cancerous cells within the tumor room to grow, which can narrow the remaining options for downstream treatment.
Further, the boundary between host tissue cell types within an organ is not cleanly and identically distributed. An individual organ (liver, heart, etc.) is like a sandwich of various cell subtypes. As a result, there are fewer options for "silver bullets" that can hit the target while leaving the surrounding tissue intact. This, too, complicates treatment.
posted by Blazecock Pileon at 5:26 AM on March 18, 2011 [1 favorite]
This Gladwell piece gives some insight into the complexities of developing treatments for specific types of cancer.
posted by crocomancer at 5:49 AM on March 18, 2011
posted by crocomancer at 5:49 AM on March 18, 2011
Also, looking for an expert here - given the huge investments towards cancer research, how far away are we from a cure? Or is it not so simple?
Not only are the cancers that occur in different tissues different kinds of cancer (e.g., colon or breast cancer), but each tumor is different from all other tumors. Those that occur in the same tissue have similarities, but they are not the same. This is because the cells in tumors evolve from normal cells by acquiring mutations (like from radiation) that cause their disregulation.
There's a podcast from RadioLab on Famous Tumors that is pretty informative and entertaining. The whole thing is fascinating, but you can listen for a few minutes around 12:15 if you are short on time to get at how cancer develops and why each tumor is different.
posted by ms.kathleen at 6:03 AM on March 18, 2011
Not only are the cancers that occur in different tissues different kinds of cancer (e.g., colon or breast cancer), but each tumor is different from all other tumors. Those that occur in the same tissue have similarities, but they are not the same. This is because the cells in tumors evolve from normal cells by acquiring mutations (like from radiation) that cause their disregulation.
There's a podcast from RadioLab on Famous Tumors that is pretty informative and entertaining. The whole thing is fascinating, but you can listen for a few minutes around 12:15 if you are short on time to get at how cancer develops and why each tumor is different.
posted by ms.kathleen at 6:03 AM on March 18, 2011
how does radiation cause cancer?
Ionizing radiation is so-called because it contains enough energy to cause molecular changes within the cells of the body. Radioisotopes, like Strontium90, replace calcium in the bones. Or Iodine131 which is taken up by the thyroid can deliver pretty high local doses of ionizing radiation directly to the body.
All it takes is a few wacky cells to start reproducing and pretty soon you have a cancerous tumor.
posted by three blind mice at 6:07 AM on March 18, 2011
Ionizing radiation is so-called because it contains enough energy to cause molecular changes within the cells of the body. Radioisotopes, like Strontium90, replace calcium in the bones. Or Iodine131 which is taken up by the thyroid can deliver pretty high local doses of ionizing radiation directly to the body.
All it takes is a few wacky cells to start reproducing and pretty soon you have a cancerous tumor.
posted by three blind mice at 6:07 AM on March 18, 2011
Radiation from say a nuclear meltdown causes cancer also by the atoms passing through a cells dna and damaging it. this causes this cell to become abnormal and then when it reproduces will be cancerous.
posted by majortom1981 at 6:34 AM on March 18, 2011
posted by majortom1981 at 6:34 AM on March 18, 2011
This bestseller was very informative on the subject of cancer.
posted by tamitang at 6:41 AM on March 18, 2011
posted by tamitang at 6:41 AM on March 18, 2011
Another thing that hasn't been mentioned yet is the idea that just about everyone has a few of these cells floating around their body--cells that have the genetic ability to grow out of control. Other conditions in the body prevent them from doing so. But if those normal conditions get messed with--say, by killing off the
neighboring healthy cells by blasting them with high energy radiation--conditions can become more favorable for the delinquent cell to gain a foothold.
We're finding that asking for a cure for cancer is almost like asking for a cure for all bacterial infection--not only do different treatments work differently, but the damned stuff is everywhere, much more common than originally thought. So another line of inquiry lies in figuring out what sort of conditions are favorable for those cells and preventing that--if you can delay the inevitable for 60 years, that might be close enough to a cure for most folks. From the talks I've been to (I'm not a cancer biologist but I'm doing some really indirect work that means I talk to them a lot), people in the field use the phrase "cure for cancer" almost like a joke, the way an IT person might talk about inventing the Internet.
posted by tchemgrrl at 6:48 AM on March 18, 2011
neighboring healthy cells by blasting them with high energy radiation--conditions can become more favorable for the delinquent cell to gain a foothold.
We're finding that asking for a cure for cancer is almost like asking for a cure for all bacterial infection--not only do different treatments work differently, but the damned stuff is everywhere, much more common than originally thought. So another line of inquiry lies in figuring out what sort of conditions are favorable for those cells and preventing that--if you can delay the inevitable for 60 years, that might be close enough to a cure for most folks. From the talks I've been to (I'm not a cancer biologist but I'm doing some really indirect work that means I talk to them a lot), people in the field use the phrase "cure for cancer" almost like a joke, the way an IT person might talk about inventing the Internet.
posted by tchemgrrl at 6:48 AM on March 18, 2011
Basically, all cells are programmed to die eventually. If something goes wrong in this process, the cell can lose control of the cell cycle.
That's close, but not precisely it.
What's really going on is that most cells have the capacity to create copies of themselves by cell division. For example, this is how your skin completely replaces itself over the period of about a month. Some cells do this incredibly quickly (e.g. the pancreas) others incredibly slowly (e.g. nerves and bone). But all of them, when healthy, "know" when to stop dividing, both in terms of the number and frequency of divisions. This is why your organs stay pretty much the same size while constantly producing new cells. It's pretty amazing, when you think about it.
But here's the catch: every time a cell divides, it's possible that there will be an error in the process. DNA molecules are billions of atoms long, and while we don't think that most of that actually does anything, the odds of a problem happening somewhere along the way are pretty decent. Sometimes the error is harmless, as it occurs in one of those places which doesn't seem to do anything. Other times, an error results in the death of the new cell, either because it isn't viable or because the immune system recognizes that something is wrong and kills it. But very infrequently, a cell is damaged in such a way that the body does not recognize as being foreign. When the damage has to do with cell reproduction, you've got a tumor. Sometimes the tumor just sort of slowly grows in a distinct mass. These aren't necessarily life threatening and are classified as "benign," though they can be uncomfortable and even dangerous depending on where they're located. "Malignant" tumors are an immediate health risk and have a tendency to metastisize, i.e. spread to other areas of the body.
So how does radiation cause cancer? Two ways, really. First, it can cause errors in the reproduction process. Cell division is basically a chemical reaction, and adding extra energy to any chemical reaction can change the result. Second, it can damage existing cells so that even if they reproduce perfectly, they propagate that error through all succeeding generations. But radiation is only one cause of cancer. Environmental toxins and plain old bad luck can be causes as well. It's possible to get cancer even if you have no identifiable risk factors.
Just about any type of tissue can become cancerous, though some kinds are more common than others for a variety of reasons, and certain kinds are more aggressive than others. Skin cancer is reasonably common because the skin is exposed to a lot of radiation and toxins which can damage cells. That's kind of why it's there, so this shouldn't be terribly surprising. Some skin cancers, i.e. melanoma, can be incredibly dangerous, because the skin normally reproduces so quickly that the cancer can spread very, very fast. Pancreatic cancer is one of the most lethal forms--five-year survival rate is about 5%--because pancreatic cells reproduce unbelievably rapidly, making it quite likely that the cancer will not be detected until it is far too late to do anything about it. On the other hand, bone tumors are one of the more treatable types of cancer, because bone cells don't reproduce all that rapidly. And heart cancer is extremely rare, as cardiac cells don't tend to divide at all.
posted by valkyryn at 6:50 AM on March 18, 2011 [4 favorites]
That's close, but not precisely it.
What's really going on is that most cells have the capacity to create copies of themselves by cell division. For example, this is how your skin completely replaces itself over the period of about a month. Some cells do this incredibly quickly (e.g. the pancreas) others incredibly slowly (e.g. nerves and bone). But all of them, when healthy, "know" when to stop dividing, both in terms of the number and frequency of divisions. This is why your organs stay pretty much the same size while constantly producing new cells. It's pretty amazing, when you think about it.
But here's the catch: every time a cell divides, it's possible that there will be an error in the process. DNA molecules are billions of atoms long, and while we don't think that most of that actually does anything, the odds of a problem happening somewhere along the way are pretty decent. Sometimes the error is harmless, as it occurs in one of those places which doesn't seem to do anything. Other times, an error results in the death of the new cell, either because it isn't viable or because the immune system recognizes that something is wrong and kills it. But very infrequently, a cell is damaged in such a way that the body does not recognize as being foreign. When the damage has to do with cell reproduction, you've got a tumor. Sometimes the tumor just sort of slowly grows in a distinct mass. These aren't necessarily life threatening and are classified as "benign," though they can be uncomfortable and even dangerous depending on where they're located. "Malignant" tumors are an immediate health risk and have a tendency to metastisize, i.e. spread to other areas of the body.
So how does radiation cause cancer? Two ways, really. First, it can cause errors in the reproduction process. Cell division is basically a chemical reaction, and adding extra energy to any chemical reaction can change the result. Second, it can damage existing cells so that even if they reproduce perfectly, they propagate that error through all succeeding generations. But radiation is only one cause of cancer. Environmental toxins and plain old bad luck can be causes as well. It's possible to get cancer even if you have no identifiable risk factors.
Just about any type of tissue can become cancerous, though some kinds are more common than others for a variety of reasons, and certain kinds are more aggressive than others. Skin cancer is reasonably common because the skin is exposed to a lot of radiation and toxins which can damage cells. That's kind of why it's there, so this shouldn't be terribly surprising. Some skin cancers, i.e. melanoma, can be incredibly dangerous, because the skin normally reproduces so quickly that the cancer can spread very, very fast. Pancreatic cancer is one of the most lethal forms--five-year survival rate is about 5%--because pancreatic cells reproduce unbelievably rapidly, making it quite likely that the cancer will not be detected until it is far too late to do anything about it. On the other hand, bone tumors are one of the more treatable types of cancer, because bone cells don't reproduce all that rapidly. And heart cancer is extremely rare, as cardiac cells don't tend to divide at all.
posted by valkyryn at 6:50 AM on March 18, 2011 [4 favorites]
This is my favorite explanation of why "a cure for cancer" is not only unachievable, it's not even the right way to think about it.
posted by Mayor West at 6:53 AM on March 18, 2011
posted by Mayor West at 6:53 AM on March 18, 2011
If you think about bacteria, yeast and other single-celled organisms, what is it they do best? Divide and reproduce exponentially as long as they have enough available nutrition. This process is the very essence of what in means to be alive; the definition of life itself.
The cells in your body have the same essential imperative, but obviously they have to restrain themselves in order to keep you alive. To do this, they have a complex network of signals that tell them when they may or may not grow and divide. More signals police this behaviour, and cause the cells to commit suicide if they fell themselves getting control.
If there is a failure in the systems that cause this self restraint, as well as a failure to police the growth of cells, certain groups of cells might start behaving a bit more like their single-celled ancestors and start growing and dividing unchecked. This is cancer.
The complex system of checks and balance I was talking about is, of course, controlled by genes, which are made of DNA. Radiation damages (or mutates) DNA, which can inactivate genes. Even worse, mutation can cause genes to malfunction, causing them to be switched on or off in the wrong places, or making them overactive, making them do the opposite of their normal function, or even do something entirely different from normal.
So in summary, radiation can cause damage to DNA, which can result in failure of the systems that control the growth and death of cells, leading to cancer.
As to "a cure for cancer", did I mention that the systems that control growth and death are complex? They are really very, very complex. They could go wrong in millions of ways. And there are many many different types of cells in the human body in which this could happen. This is why they say no two cancers are the same. There will be no single "cure for cancer".
On the up side, I'm sure you know many people who have survived cancer, who maybe 50 years ago would certainly have died? Maybe you're old enough to remember when childhood leukaemia was a certain death sentence? Things are getting better all the time.
I disagree with much of this famous comic but it's worth reading all the same.
posted by nowonmai at 7:05 AM on March 18, 2011
The cells in your body have the same essential imperative, but obviously they have to restrain themselves in order to keep you alive. To do this, they have a complex network of signals that tell them when they may or may not grow and divide. More signals police this behaviour, and cause the cells to commit suicide if they fell themselves getting control.
If there is a failure in the systems that cause this self restraint, as well as a failure to police the growth of cells, certain groups of cells might start behaving a bit more like their single-celled ancestors and start growing and dividing unchecked. This is cancer.
The complex system of checks and balance I was talking about is, of course, controlled by genes, which are made of DNA. Radiation damages (or mutates) DNA, which can inactivate genes. Even worse, mutation can cause genes to malfunction, causing them to be switched on or off in the wrong places, or making them overactive, making them do the opposite of their normal function, or even do something entirely different from normal.
So in summary, radiation can cause damage to DNA, which can result in failure of the systems that control the growth and death of cells, leading to cancer.
As to "a cure for cancer", did I mention that the systems that control growth and death are complex? They are really very, very complex. They could go wrong in millions of ways. And there are many many different types of cells in the human body in which this could happen. This is why they say no two cancers are the same. There will be no single "cure for cancer".
On the up side, I'm sure you know many people who have survived cancer, who maybe 50 years ago would certainly have died? Maybe you're old enough to remember when childhood leukaemia was a certain death sentence? Things are getting better all the time.
I disagree with much of this famous comic but it's worth reading all the same.
posted by nowonmai at 7:05 AM on March 18, 2011
Response by poster: Thanks everyone for the answers. I didn't realise how little actual knowledge I had about cancer in general nor radiation and the effects on cells.
posted by Funmonkey1 at 7:21 AM on March 18, 2011
posted by Funmonkey1 at 7:21 AM on March 18, 2011
Like tamitang, I'd recommend reading The Emperor of All Maladies: A Biography of Cancer. It's easy to read, informative, and very engaging.
posted by k8lin at 7:24 AM on March 18, 2011
posted by k8lin at 7:24 AM on March 18, 2011
As had already been stated, cancer is typically due to a mutation causing irregular cell growth. Another example is the well known BRCA1 1 gene giving a predisposition to cancer. The reason is that BRCA1 helps regulate cell growth and repair DNA damage (question 3). While BRCA1 is typically a genetic trait, the same effect of dna mutations occur from radiation.
As another example, take a look at this wikipedia article on Cell Cycles (all wiki negatives aside, I find their hard science articles to be a decent starting point). I linked specifically to the Inhibitors subsection- they are called this for a reason. A mutation to any of the genes mentioned can cause irregular cell growth and tumors.
For an introduction to cancer itself: It might be outdated now as it's from 2000, but this article was a good introduction for my non-science major friends on an introduction to cancer that might help you understand what cancer is in the first place and why it sucks.
posted by jmd82 at 7:28 AM on March 18, 2011
As another example, take a look at this wikipedia article on Cell Cycles (all wiki negatives aside, I find their hard science articles to be a decent starting point). I linked specifically to the Inhibitors subsection- they are called this for a reason. A mutation to any of the genes mentioned can cause irregular cell growth and tumors.
For an introduction to cancer itself: It might be outdated now as it's from 2000, but this article was a good introduction for my non-science major friends on an introduction to cancer that might help you understand what cancer is in the first place and why it sucks.
posted by jmd82 at 7:28 AM on March 18, 2011
To elaborate on valkyryn's nice summary:
Cells have multiple checkpoints in their reproduction/self-destruction process that help prevent the growth of a tumor even in the case of a mutation. It's only in circumstances in which a single cell acquires multiple mutations in genes that regulate several different cell survival steps that a tumor starts to grow.
As we grow older, these random mutations start to build up and propagate through cell lines. One cell that develops a mutation in, say, a gene that controls the rate of cell division might propagate still harmlessly through its daughter cells, held in check by the other genes that limit cell growth and division. Then as time goes on, one of these daughter cells acquires another mutation in a different gene that, say, enables the cell to self-destruct (result being that the cell can't kill itself anymore and becomes "immortal"). Over time, these mutations start adding up, until eventually the checkpoints are simply insufficient to hold back uncontrolled cell division and growth.
In life, we're actually constantly being exposed to radiation, whether through sunlight/UV, soil, etc. Increased radiation caused by the nuclear fallout merely speeds up the process of mutation build-up. This is the reason that cancer becomes more common as we grow older; the mutations in our DNA simply add up until by chance, a certain cell acquires enough mutations to become cancerous. This also explains why cancer is so difficult, if not impossible, to prevent, because it's a process that occurs as part of the natural wear-and-tear of DNA.
posted by qxrt at 8:30 AM on March 18, 2011
Cells have multiple checkpoints in their reproduction/self-destruction process that help prevent the growth of a tumor even in the case of a mutation. It's only in circumstances in which a single cell acquires multiple mutations in genes that regulate several different cell survival steps that a tumor starts to grow.
As we grow older, these random mutations start to build up and propagate through cell lines. One cell that develops a mutation in, say, a gene that controls the rate of cell division might propagate still harmlessly through its daughter cells, held in check by the other genes that limit cell growth and division. Then as time goes on, one of these daughter cells acquires another mutation in a different gene that, say, enables the cell to self-destruct (result being that the cell can't kill itself anymore and becomes "immortal"). Over time, these mutations start adding up, until eventually the checkpoints are simply insufficient to hold back uncontrolled cell division and growth.
In life, we're actually constantly being exposed to radiation, whether through sunlight/UV, soil, etc. Increased radiation caused by the nuclear fallout merely speeds up the process of mutation build-up. This is the reason that cancer becomes more common as we grow older; the mutations in our DNA simply add up until by chance, a certain cell acquires enough mutations to become cancerous. This also explains why cancer is so difficult, if not impossible, to prevent, because it's a process that occurs as part of the natural wear-and-tear of DNA.
posted by qxrt at 8:30 AM on March 18, 2011
Was involved with cancer research at the bench level for over 10 years, and continue to have an active interest in the subject.
All good comments above, regarding the molecular basis of cancer being a 'disease of DNA'.
Of interest is that low-level cumulative amounts of radiation is much worse in terms of cancer risk than a single large dose; retrospective studies of atomic bomb survivors (of course from Japan in WWII) bear this out.
Also there have been very good strides made against cancer in terms of progress. Here's a useful American Cancer Society page with useful presentations. Of note is that the US Death Rate from cancer dropped some 17% from 1991 to 2007 (slide 4 of the 'Cancer Statistics 2010' slide presentation).
While not as good on a percentage-lowered basis to heart disease, c-v disease or infectious diseases (flu and pneumonia), still progress nonetheless.
Something to take note of is the remarkable advances in DNA whole-genome sequencing, where the costs are dropping some 3-fold on a yearly basis. Much of the focus of the application of this technology is tackling cancer, comparing tumor with normal tissues from the same individual.
posted by scooterdog at 6:42 PM on March 20, 2011
All good comments above, regarding the molecular basis of cancer being a 'disease of DNA'.
Of interest is that low-level cumulative amounts of radiation is much worse in terms of cancer risk than a single large dose; retrospective studies of atomic bomb survivors (of course from Japan in WWII) bear this out.
Also there have been very good strides made against cancer in terms of progress. Here's a useful American Cancer Society page with useful presentations. Of note is that the US Death Rate from cancer dropped some 17% from 1991 to 2007 (slide 4 of the 'Cancer Statistics 2010' slide presentation).
While not as good on a percentage-lowered basis to heart disease, c-v disease or infectious diseases (flu and pneumonia), still progress nonetheless.
Something to take note of is the remarkable advances in DNA whole-genome sequencing, where the costs are dropping some 3-fold on a yearly basis. Much of the focus of the application of this technology is tackling cancer, comparing tumor with normal tissues from the same individual.
posted by scooterdog at 6:42 PM on March 20, 2011
Just nthing the recommendation for The Emperor of All Maladies. It's a spectacular book on many levels; in addition to getting an engaging history of cancer and how the treatments have evolved, you'll get a much stronger understanding of how cancer works and several beautifully written, empathetic passages about how it effects people.
posted by Nattie at 7:47 AM on April 3, 2011
posted by Nattie at 7:47 AM on April 3, 2011
This thread is closed to new comments.
posted by lollusc at 4:40 AM on March 18, 2011 [5 favorites]