Cancer Is a Failure of Apoptosis (How Cancer Develops)

Updated on September 30, 2017
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Rhys Baker teaches science at Arthur Mellows Village College in Peterborough, UK.

What Is Cancer?

The average adult human body creates around 60 billion new cells each day by somatic cell division (mitosis). Therefore, an equal number must also die to maintain the cell number - this is known as cell homeostasis. There are several ways a cell can die (each will be explained in depth in an upcoming hub):

  1. Necrosis: Uncontrolled cell death. Basically, the cells burst, spewing their contents into the surrounding tissue fluid. This causes inflammation, pain and swelling. Necrosis is usually the result of cellular injury or infection.
  2. Apoptosis (Programmed Cell Death 1): Apoptosis is a tightly regulated, multi-step pathway responsible for cell death during development and tissue homeostasis. Enzyme action is required for this (unlike necrosis) - Genetic control is maintained right to the end.
  3. Programmed Cell Death (Non-Apoptotic): Cell death is still controlled, but lacks some of the key characteristics of apoptosis. Protein synthesis and genetic activity seen until the cell is engulfed.

Disruption of the cell division-cell death balance can be catastrophic. Where mitosis outstrips apoptosis, cancer can develop; Apoptosis outstripping mitosis can lead to degenerative diseases such as certain forms of dementia

A fake-colour image of a blebbing cancer cell. The jagged edges show the cell is cancerous. Blebbing can be seen in purple. Each bleb will fall away (hence 'apoptosis') and be consumed by white blood cells
A fake-colour image of a blebbing cancer cell. The jagged edges show the cell is cancerous. Blebbing can be seen in purple. Each bleb will fall away (hence 'apoptosis') and be consumed by white blood cells | Source

Apoptosis - Our Defence Against Cancer

Apoptosis is the major mechanism by which misplaced, unnecessary or irreparably damaged cells are removed from the organism. As such, cellular escape from apoptosis is a critical requirement for tumorigenesis. As can be seen from the diagram "Acquired Capabilities of Cancer" below, tumorigenesis is a multi-step process.

When Does a Tumour Become Cancer?

Cancer cells are cells that have become immortal. They have escaped the Hayflick limit, which states that a single normal body cell can only divide between 40 and 60 times before being permanently destroyed. A single immortal cell does not a cancer make, however: the acquisition of the 'tissue invasion' trait that marks out a cell as an invasive, malignant cancer

It can be argued that tumour development is a process similar to that of Darwinian evolution. The cancer cells undergo a series of genetic changes. If this change confers a type of growth advantage over the surrounding cells (a favourable process in evolution, not so favourable in a multi-cellular organism where the cells are supposed to be working in perfect synchrony), then the cell has taken another step towards become cancerous.

It must be noted that cancer cells require several new traits in order to survive. Without sustained angiogenesis (blood vessel formation), self sufficiency in growth signals (because they are not coming from the body), and insensitivity to anti-growth signals (which WILL be coming from the body in an effort to quell this uprising), the 'proto-cancer' cells can still die by other means, even if they have escaped Apoptotic Programmed Cell Death

The Acquired Capabilities of Cancer

It is suggested that all the types of cancer have acquired the same set of functional capabilities during their development, albeit through different pathways
It is suggested that all the types of cancer have acquired the same set of functional capabilities during their development, albeit through different pathways | Source

All Cancers are not Created Equal

The order in which a cell attains the different of capabilities typical of a cancer phenotype can differ, as highlighted in the two six step pathways. The number of mutations required for a cancer phenotype can also differ. In some tumours, a particular genetic mutation may confer several capabilities simultaneously: the five step pathway illustrates a loss of function mutation in p53, which confers both resistance to apoptosis and sustained angiogenesis. In other tumours, it may take several mutations to acquire a certain capability: the eight step pathway requires two steps to acquire tissue invasion/metastasis and evasion of apoptosis.

Cancer is caused by cells escaping, via one means or another, the growth control mechanisms in the body. It does take time to develop, which is why early diagnosis is vital to survival.
Cancer is caused by cells escaping, via one means or another, the growth control mechanisms in the body. It does take time to develop, which is why early diagnosis is vital to survival. | Source

No, Apoptosis.

It is easy to think that once a tumour has developed, all apoptotic mechanisms have been shut off in the vicinity. As proven by Kerr, Wyllie and Currie (1972), the observed growth rate of tumours is lower than it should be. This is due to a surprisingly high level of endogenous tumour cell apoptosis. The uncontrolled proliferation of cells that is characteristic of cancer can be due to:

  • Increased Mitosis
  • Decreased Apoptosis
  • A combination of the two

Indeed, the defensive apoptotic machinery is usually intact in cancer cells (with the exception of one or two key bcl-2 or p53 mutations- but its activation threshold is much higher. Due to this, reactivating apoptosis in tumour cells is a tangible possibility.

How Is Cancer Treated?

By now you should have a more in depth knowledge of the molecular causes of cancer. It is this understanding of how cancer develops, proliferates, and survives where it shouldn't, that has allowed ever-more effective therapies to be developed. In the war against cancer, knowledge is our greatest weapon.

Questions & Answers

    © 2011 Rhys Baker

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      • TFScientist profile imageAUTHOR

        Rhys Baker 

        4 years ago from Peterborough, UK

        I can't help with specific seminar or term-paper topics.

        I suggest you start with a molecular biology textbook and then look at some of the scientific papers available on the subject. Apoptosis is a vital process in cancer, degenerative diseases, the healing process, learning and growth and development. I'm sure there is plenty out there.

        I have been plaigarised in requests before, so I don't do them anymore.

      • profile image

        israel 

        4 years ago

        nice hubs..i find it some how difficult to comprehend. but trust me it's a nice work and i was able to gain some things. i need your assist on my seminar topic 'the role of apoptosis in medicine". i will be glad if i can see something on that.thanks

      • profile image

        honey 

        5 years ago

        This information is hard to understand.

      • TFScientist profile imageAUTHOR

        Rhys Baker 

        5 years ago from Peterborough, UK

        Thanks for the comment, Paddy. It's good to see that people with experience in the field still see the validity in this, even several years after finishing my degree!

      • PaddyMac1984 profile image

        Patrick McCormack 

        5 years ago from Nottingham, England

        This is a good informative Hub. I have worked in histology for a fair few years and its good to find pages which cut to the bare essentials. Its also good to see that you follow up when people ask for explanations too. I like the Hub. Voted useful and Up. Thanks.

      • TFScientist profile imageAUTHOR

        Rhys Baker 

        5 years ago from Peterborough, UK

        Antioxidant supplements are not proven to even be absorbed in a meaningful way by the body, let alone prevent cancer. As to the narrow focus of the hub, that is the point. The previous hub deals with how cancer develops. This is not as simplistic as you have made it sound though.

        Thanks for the comment

      • conradofontanilla profile image

        conradofontanilla 

        5 years ago from Philippines

        Only three kinds of cells do not undergo apoptosis: nerve cells, brain cells and cardiovascular cells. Blood cells replace themselves every 140 days, for example. But when a cell is mutated enough it does not undergo apoptosis. For example, a polyp must undergo 5 to 7 mutations to reach cancer stage, colon cancer.

        This Hub shows the development of cancer but does not mention what starts it. Free radicals and their derivatives start tumor or cancer. Their neutralization to the point that they are balanced by built in and supplement antioxidants will prevent cancer.

      • Kathryn L Hill profile image

        Kathryn L Hill 

        6 years ago from LA

        Oh I see. Then problems occur during mitosis? My Doctor said there is no way to prevent cancer and no "natural" way to cure it. Do you agree? Most people will tell you that there are things we can do to Avoid problems with mitosis. What are those things based on. I mean is there a general way to be proactive? Or is it the luck of the genetic draw? Thanks for answering up there. I am so baffled by Cancer and I figure there must be Something we are doing wrong.

      • TFScientist profile imageAUTHOR

        Rhys Baker 

        6 years ago from Peterborough, UK

        It sounds horrible but it is happening every second of every day and is needed to keep you healthy. You make lots of new cells every day and if other cells didn't die then you would get bigger and bigger! Apoptosis is just the method that these old cells that are past their best use to commit suicide. If they don't commit suicide then cancer is one of the diseases that can develop. You don't notice it happening. It happens in almost every part of your body.

      • Kathryn L Hill profile image

        Kathryn L Hill 

        6 years ago from LA

        What the heck is Apoptosis? I read the definition but am still puzzled. Programed cell death. That sounds horrible. Sometimes I wonder if some people just can't become "old." I remember thinking as a young kid that I would rather stab myself with a knife than get "old." (I wanted to die so that I could be a young angel... not an old one.) Sure enough around age 54 I had to have a hysterectomy for endometrial cancer. I would be up in heaven as a 54 year old angel at this point (following my ten year old reasoning,) were it not for modern methods of "cure".

      • TFScientist profile imageAUTHOR

        Rhys Baker 

        6 years ago from Peterborough, UK

        Nobody said tha molecular oncology was easy! How can I clear up your understanding?

      • Kathryn L Hill profile image

        Kathryn L Hill 

        6 years ago from LA

        Well without really studying this, your hub is is clear as mud to me. I wish it was easier to comprehend. I can't believe it is so complicated. Is cancer preventable ? I have heard that every single case of cancer is unique to the individual, like a fingerprint.

      • rasta1 profile image

        Marvin Parke 

        6 years ago from Jamaica

        I have been researching cancer for a long time and I find your information very in depth and meticulous. I have to bookmark this series

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