If we had to talk about the one disease which is the bane of all hospitals, the one disease which strikes fear into every doctor's heart, the one disease which no one can be fully assured of a complete recovery, it would definitely be cancer. Cancer is one of the biggest killers of the 21st century, right up there with heart disease. The difference is that we cannot be assured of a cure for it.
However, what many people don't know is how cancer kills, and why it is so difficult to cure. To understand this, we must first understand what cancer actually is.
Simply put, cancer is uncontrolled growth. Normally, to restrict growth, cells undergo what we call contact inhibition. Contact inhibition is when cells stop dividing once they come into contact with one another- that is to say, they stop dividing when there is no more space left for them to divide. What is more, cells are also anchorage-dependent; which means that they may only divide when they are anchored to some sort of surface.
Cancer cells, however, are not anchorage-dependent, nor do they follow the rules of contact inhibition. They divide uncontrollably and clump up, eventually forming what we call a tumour. A simple demonstration of cancer growth is given below:
As you can see in the bottom picture, cancer cells ignore contact inhibition and keep on growing and piling on top of one another, leading to tumour growth.
Now, one would possibly think that there would be a limit for cell division and it could also apply to cancer cells, which would eventually stop tumour growth. Well, one would be right about there existing a limit for cell division- it is called Hayflick's limit. As most of you probably know, DNA exists as special segments in the nucleus of a cell called chromosomes, and at the end of each chromosome is an extension called a telomere. This telomere is what defines Hayflick's limit- the longer it is, the more a cell shall divide.
However, cancer cells have acclimated so many mutations, due to which they have an abnormal number of chromosomes, that Hayflick's limit simply doesn't apply to them any longer. They may bypass it and continue to divide even while sustaining damage. Normally, if a cell reaches Hayflick's limit, it would go into a 'quiescent' phase and stop dividing, but cancer cells continue to do so, due to their several mutations leading to certain kinds of genes (which are segments of chromosomes) called oncogenes becoming overexpressed. When oncogenes become overexpressed, cell division happens at an extremely high rate, and tumours come about.
Now, you might be thinking- cell division takes energy. When cancer cells divide abnormally, where do they get enough energy to do so? Again, due to their several mutations, cancer cells have an altered metabolism, which allows them to anaerobically (which means without using oxygen) convert glucose to lactate, which releases energy. It's what your muscles do when you're exercising too quickly, and you can't take in enough oxygen to produce energy normally! What's more, they induce a process called angiogenesis, which means that new blood vessels are made so that nutrients may be carried over to the tumour and feed it so that it may grow.
However, there must be a limit to how much of the body's nutrition may go towards a single area. That is why the tumour starts spreading after some time, going via the blood vessels and ending up in different sites in order to divide further. This is called metastasis. Now, it must be no surprise as to why cancer is such a massive killer- if there are so many cells dividing abnormally around the body, its life processes shall be interfered with and therefore, it shall cease.
However, work is being done to figure out where cancer spreads, and already a hypothesis has been conceived to rationalize why certain cancers spread to certain areas. According to the hypothesis, tumours that are generated in certain organs may only thrive in some other specific areas. For example, if a patient has a certain kind of cancer X, it will only spread to areas Y and Z. As this has been compared to a seed spreading from its fruit and germinating in a certain soil, this has been called the seed-and-soil hypothesis and was established by Stephen Paget when he examined post-mortem data from over 700 cases of breast cancer.
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For more math and science-focused articles that will be uploaded frequently, please follow my blog on Blogger.com! It's easy- just create your own account on Blogger, click on 'Reading list', 'edit', then 'add'. Thank you so much for reading!
However, what many people don't know is how cancer kills, and why it is so difficult to cure. To understand this, we must first understand what cancer actually is.
Simply put, cancer is uncontrolled growth. Normally, to restrict growth, cells undergo what we call contact inhibition. Contact inhibition is when cells stop dividing once they come into contact with one another- that is to say, they stop dividing when there is no more space left for them to divide. What is more, cells are also anchorage-dependent; which means that they may only divide when they are anchored to some sort of surface.
Cancer cells, however, are not anchorage-dependent, nor do they follow the rules of contact inhibition. They divide uncontrollably and clump up, eventually forming what we call a tumour. A simple demonstration of cancer growth is given below:
As you can see in the bottom picture, cancer cells ignore contact inhibition and keep on growing and piling on top of one another, leading to tumour growth.
Now, one would possibly think that there would be a limit for cell division and it could also apply to cancer cells, which would eventually stop tumour growth. Well, one would be right about there existing a limit for cell division- it is called Hayflick's limit. As most of you probably know, DNA exists as special segments in the nucleus of a cell called chromosomes, and at the end of each chromosome is an extension called a telomere. This telomere is what defines Hayflick's limit- the longer it is, the more a cell shall divide.
However, cancer cells have acclimated so many mutations, due to which they have an abnormal number of chromosomes, that Hayflick's limit simply doesn't apply to them any longer. They may bypass it and continue to divide even while sustaining damage. Normally, if a cell reaches Hayflick's limit, it would go into a 'quiescent' phase and stop dividing, but cancer cells continue to do so, due to their several mutations leading to certain kinds of genes (which are segments of chromosomes) called oncogenes becoming overexpressed. When oncogenes become overexpressed, cell division happens at an extremely high rate, and tumours come about.
Now, you might be thinking- cell division takes energy. When cancer cells divide abnormally, where do they get enough energy to do so? Again, due to their several mutations, cancer cells have an altered metabolism, which allows them to anaerobically (which means without using oxygen) convert glucose to lactate, which releases energy. It's what your muscles do when you're exercising too quickly, and you can't take in enough oxygen to produce energy normally! What's more, they induce a process called angiogenesis, which means that new blood vessels are made so that nutrients may be carried over to the tumour and feed it so that it may grow.
However, there must be a limit to how much of the body's nutrition may go towards a single area. That is why the tumour starts spreading after some time, going via the blood vessels and ending up in different sites in order to divide further. This is called metastasis. Now, it must be no surprise as to why cancer is such a massive killer- if there are so many cells dividing abnormally around the body, its life processes shall be interfered with and therefore, it shall cease.
However, work is being done to figure out where cancer spreads, and already a hypothesis has been conceived to rationalize why certain cancers spread to certain areas. According to the hypothesis, tumours that are generated in certain organs may only thrive in some other specific areas. For example, if a patient has a certain kind of cancer X, it will only spread to areas Y and Z. As this has been compared to a seed spreading from its fruit and germinating in a certain soil, this has been called the seed-and-soil hypothesis and was established by Stephen Paget when he examined post-mortem data from over 700 cases of breast cancer.
-----------------------------------------------------------------------------------------------------------------------
For more math and science-focused articles that will be uploaded frequently, please follow my blog on Blogger.com! It's easy- just create your own account on Blogger, click on 'Reading list', 'edit', then 'add'. Thank you so much for reading!
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