CancerCancer Cancer is one of the most common diseases in Cancer is one of the most common diseases in

the developed world:the developed world: 1 in 4 deaths are due to cancer1 in 4 deaths are due to cancer 1 in 17 deaths are due to 1 in 17 deaths are due to lung cancerlung cancer Lung cancer is the most common cancer in Lung cancer is the most common cancer in

menmen Breast cancer is the most common cancer in Breast cancer is the most common cancer in

womenwomen There are over 100 different forms of cancerThere are over 100 different forms of cancer

CancerCancer The division of normal cells is precisely The division of normal cells is precisely

controlled. New cells are only formed for controlled. New cells are only formed for growth or to replace dead ones.growth or to replace dead ones.

Cancerous cells divide repeatedly out of Cancerous cells divide repeatedly out of control even though they are not needed, control even though they are not needed, they crowd out other normal cells and they crowd out other normal cells and function abnormally. They can also destroy function abnormally. They can also destroy the correct functioning of major organs.the correct functioning of major organs.

What causes cancer?What causes cancer? Cancer arises from the Cancer arises from the mutationmutation of a of a

normal gene.normal gene. Mutated genes that cause cancer are Mutated genes that cause cancer are

called called oncogenesoncogenes.. It is thought that several mutations need It is thought that several mutations need

to occur to give rise to cancerto occur to give rise to cancer Cells that are old or not functioning Cells that are old or not functioning

properly normally self destruct and are properly normally self destruct and are replaced by new cells.replaced by new cells.

However, cancerous cells do not self However, cancerous cells do not self destruct and continue to divide rapidly destruct and continue to divide rapidly producing millions of new cancerous producing millions of new cancerous cells.cells.

A factor which brings about a A factor which brings about a mutation is called a mutation is called a mutagen.mutagen.

A mutagen is A mutagen is mutagenic.mutagenic.

Any agent that causes cancer is Any agent that causes cancer is called a called a carcinogencarcinogen and is described and is described as as carcinogeniccarcinogenic..

So some mutagens are carcinogenic.So some mutagens are carcinogenic.

CarcinogensCarcinogens Ionising radiationIonising radiation – X Rays, UV light – X Rays, UV light

ChemicalsChemicals – tar from cigarettes – tar from cigarettes

Virus infectionVirus infection – papilloma virus can be – papilloma virus can be responsible for cervical cancer.responsible for cervical cancer.

Hereditary predispositionHereditary predisposition – Some families – Some families are are more susceptiblemore susceptible to getting certain to getting certain cancers. Remember cancers. Remember you can’t inherit you can’t inherit cancercancer its just that you maybe more its just that you maybe more susceptible to getting it.susceptible to getting it.

Benign or malignant?Benign or malignant? Benign tumoursBenign tumours do not spread from their site of do not spread from their site of

origin, but can crowd out (squash) surrounding origin, but can crowd out (squash) surrounding cells eg brain tumour, warts.cells eg brain tumour, warts.

Malignant tumoursMalignant tumours can spread from the original can spread from the original site and cause site and cause secondary tumourssecondary tumours. This is called . This is called metastasismetastasis. They interfere with neighbouring . They interfere with neighbouring cells and can block blood vessels, the gut, cells and can block blood vessels, the gut, glands, lungs etc.glands, lungs etc.

Why are secondary tumours so bad?Why are secondary tumours so bad?

Both types of tumour can tire the body out as Both types of tumour can tire the body out as they both need a huge amount of nutrients to they both need a huge amount of nutrients to sustain the rapid growth and division of the cells.sustain the rapid growth and division of the cells.

The Development of CancerThe Development of Cancer Within every nucleus of every one of Within every nucleus of every one of

the human body's 30 trillion cells the human body's 30 trillion cells exists DNA, the substance that exists DNA, the substance that contains the information needed to contains the information needed to make and control every cell within make and control every cell within the body. Here is a close-up view of a the body. Here is a close-up view of a tiny fragment of DNA. tiny fragment of DNA.

1. DNA of a normal cell1. DNA of a normal cell

This piece of DNA is an exact copy of the DNA This piece of DNA is an exact copy of the DNA from which it came. When the parent cell divided from which it came. When the parent cell divided to create two cells, the cell's DNA also divided, to create two cells, the cell's DNA also divided, creating two identical copies of the original DNA. creating two identical copies of the original DNA.

2. Mutation of DNA2. Mutation of DNA

Here is the same section of DNA but from another cell. If Here is the same section of DNA but from another cell. If you can imagine that DNA is a twisted ladder, then each you can imagine that DNA is a twisted ladder, then each rung of the ladder is a pair of joined molecules, or a base rung of the ladder is a pair of joined molecules, or a base pair. With this section of DNA, one of the base pairs is pair. With this section of DNA, one of the base pairs is different from the original. different from the original.

This DNA has suffered a This DNA has suffered a mutationmutation, either through mis-, either through mis-copying (when its parent cell divided), or through the copying (when its parent cell divided), or through the damaging effects of exposure to damaging effects of exposure to radiation or a chemical radiation or a chemical carcinogen.carcinogen.

3. Genetically altered cell3. Genetically altered cell

Body cells replicate through mitosis, they respond Body cells replicate through mitosis, they respond to their surrounding cells and replicate only to to their surrounding cells and replicate only to replace other cells. Sometimes a replace other cells. Sometimes a genetic mutationgenetic mutation will cause a cell and its descendants to reproduce will cause a cell and its descendants to reproduce even though replacement cells are not needed.even though replacement cells are not needed.The DNA of the cell highlighted above has a The DNA of the cell highlighted above has a mutationmutation that causes the cell to replicate even that causes the cell to replicate even though this tissue doesn't need replacement cells though this tissue doesn't need replacement cells at this time or at this place.at this time or at this place.

4. Spread and second mutation4. Spread and second mutation

The genetically altered cells have, over time, The genetically altered cells have, over time, reproduced reproduced uncheckedunchecked, crowding out the surrounding normal cells. The , crowding out the surrounding normal cells. The growth may contain one million cells and be the size of a growth may contain one million cells and be the size of a pinhead. At this point the cells continue to look the same as pinhead. At this point the cells continue to look the same as the surrounding healthy cells. the surrounding healthy cells. After about a million divisions, there's a good chance that After about a million divisions, there's a good chance that one of the new cells will have one of the new cells will have mutated furthermutated further. This cell, now . This cell, now carrying two carrying two mutant genesmutant genes, could have an , could have an altered altered appearanceappearance and be even more prone to reproduce and be even more prone to reproduce unchecked.unchecked.

5. Third mutation5. Third mutation

Not all mutations that lead to cancerous cells result in the Not all mutations that lead to cancerous cells result in the cells reproducing at a faster, more uncontrolled rate. For cells reproducing at a faster, more uncontrolled rate. For example, a mutation may simply cause a cell to keep from example, a mutation may simply cause a cell to keep from self-destructing. All normal cells have surveillance self-destructing. All normal cells have surveillance mechanisms that look for damage or for problems with their mechanisms that look for damage or for problems with their own control systems. If such problems are found, the cell own control systems. If such problems are found, the cell destroys itself.destroys itself.Over time and after many cell divisions, a Over time and after many cell divisions, a third mutationthird mutation may may arise. If the mutation gives the cell some further advantage, arise. If the mutation gives the cell some further advantage, that cell will grow more vigorously than its predecessors and that cell will grow more vigorously than its predecessors and thus speed up the thus speed up the growth of the tumourgrowth of the tumour..

6. Fourth mutation6. Fourth mutation

The new type of cells grow rapidly, allowing The new type of cells grow rapidly, allowing for more opportunities for mutations. The next for more opportunities for mutations. The next mutation paves the way for the development mutation paves the way for the development of an even more of an even more aggressive canceraggressive cancer. .

At this point the tumour is still containedAt this point the tumour is still contained..

7. Breaking through the 7. Breaking through the membranemembrane

The newer, wilder cells created by another mutation The newer, wilder cells created by another mutation are able to are able to push their way through the epithelial push their way through the epithelial tissue's basement membranetissue's basement membrane, which is a meshwork , which is a meshwork of protein that normally creates a barrier. The of protein that normally creates a barrier. The invasive cells in this tumour are invasive cells in this tumour are no longer containedno longer contained. .

At this point the cancer is still At this point the cancer is still too small to be too small to be detecteddetected..

8. Angiogenesis8. Angiogenesis

Often during the development of earlier stages of the Often during the development of earlier stages of the tumour, or perhaps by the time the tumour has broken tumour, or perhaps by the time the tumour has broken through the basement membrane (as pictured above), through the basement membrane (as pictured above), angiogenesis angiogenesis takes place. takes place. Angiogenesis is the recruitment Angiogenesis is the recruitment of blood vessels from the network of neighbouring of blood vessels from the network of neighbouring vessels. vessels.

Without blood and the nutrients it carries, a tumour would Without blood and the nutrients it carries, a tumour would be unable to continue growing. With the new blood be unable to continue growing. With the new blood supply, however, the supply, however, the growth of the tumour acceleratesgrowth of the tumour accelerates; it ; it soon contains soon contains thousand million cellsthousand million cells and, now the size of and, now the size of a small grape, is large enough to be detected as a lump a small grape, is large enough to be detected as a lump

9.Invasion and dispersal9.Invasion and dispersal

The tumour has now The tumour has now invaded the tissueinvaded the tissue beyond the beyond the basement membrane.basement membrane.

Individual cells from the tumour enter into the Individual cells from the tumour enter into the network of newly formed blood vesselsnetwork of newly formed blood vessels, using these , using these vessels as highways by which they can move to other vessels as highways by which they can move to other parts of the body. A tumour as small as a gram can parts of the body. A tumour as small as a gram can send out a million tumour cells into blood vessels a send out a million tumour cells into blood vessels a day.day.

10. Tumour 10. Tumour cells travel - cells travel - metastasismetastasis

What makes most What makes most tumours so lethal is tumours so lethal is their ability to their ability to metastasize metastasize -- that is, -- that is, establish new tumour establish new tumour sites at other sites at other locations throughout locations throughout the body.the body.Secondary tumoursSecondary tumours..

Metastasis is now Metastasis is now underway, as tumour underway, as tumour cells from the original cells from the original cancer growth travel cancer growth travel throughout the body. throughout the body. Most of these cells Most of these cells will die soon after will die soon after entering the blood or entering the blood or lymph circulation.lymph circulation.

11. Metastasis11. Metastasis

To form a To form a secondary tumoursecondary tumour, a tumour cell needs to , a tumour cell needs to leave the vessel system and invade tissue. The cell leave the vessel system and invade tissue. The cell must must attach itselfattach itself to a vessel's wall. Once this is to a vessel's wall. Once this is done, it can work its way through the vessel and done, it can work its way through the vessel and enter the tissue. enter the tissue. Although perhaps less than one in 10,000 tumour Although perhaps less than one in 10,000 tumour cells will survive long enough to establish a new cells will survive long enough to establish a new tumour site, a few survivors can escape and initiate tumour site, a few survivors can escape and initiate new coloniesnew colonies of the cancer. of the cancer.

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