Normal Cells vs. Cancer Cells 1

The characteristics of normal cellsNormal body cells have a number of important characteristics.  They can:1- Reproduce themselves exactly 2- Stop reproducing at the right time 3- Stick together in the right place 4- Self destruct if they are damaged 5- Become specialized or 'mature'

1- Reproduce themselves exactly Body tissuesBody tissues grow by increasing the number of cells that make them up.  The cells reproduce themselves exactly.  One cell doubles by dividing into two (mitosis.) Two cells become four and so on.

How cells reproduceWhen more cells are needed by the body, some cells double up to increase their numbers.  They do this very precisely so that the new cells are exactly the same as the old ones.  Each cell makes copies of all its genes.  Then it splits into two with one set of genes in each new cell.  The diagram below shows a cell dividing into two.Can all cells reproduce?Not all cells carry on being able to reproduce.  Most cells mature and become specialized for their particular job in the body.  Mature cells may lose the ability to reproduce as they develop.  But there will always be enough immature cells around (called stem cells) to replace cells that are damaged or killed. If even more cells are needed, these new cells will rest for a while and then reproduce again.  The cells will carry on doing this until enough cells have been made.

2- Stop reproducing at the right time This happens very fast between conception and adulthood.  But once we are grown up, most cells only reproduce in order to replace others that have died, for example through injury or illness.  Some cells carry on reproducing.  These include sperm cells, hair cells, cells in the gut and cells that make blood in the bone marrow.

How do the cells know when to stop growing?Normal growth and healing is very orderly and precise.  The cells somehow know when there are enough new cells to mend a cut or stop a finger growing for ever.  The diagram below shows this happening. Scientists are still finding out how the cells do this.  It seems that the cells send chemical messages to each other.  The messages come from the genes inside the cells.  Just to make sure, there are some genes that become activated and tell cells to reproduce and other genes that tell them not

How do new cells end up in the right place?Why does a growing finger end up finger shaped?  It seems the cells have a natural ability to stick together in the right place.  Scientists call this cell adhesion.There are molecules on the surface of the cell which match those on its neighbors.  It is a bit like having a post code.  The code makes it very difficult for the cell to move to the wrong place.  But if it does find itself in a place where its post code is different from its neighbors, it will die.

3- Stick together in the right place

4- Self destruct if they are damaged 5- Become specialised or 'mature'

Most cells mature and become specialized for their particular job in the body.  Mature cells may lose the ability to reproduce as they develop.

How cancer cells are different

Cancer cells are different to normal cells in several ways.  These are some features of cancer cells1.They carry on reproducing  2.They don't obey signals from other neighbouring cells  3.They don't stick together   4.They don't become specialised, but stay immature   5.They don't die if they move to another part of the body

Cancer cells don't stop reproducingUnlike normal cells, cancer cells do not stop reproducing after they have doubled 50 or 60 times.  This means that a cancer cell will go on and on and on doubling. So one cell becomes 2, then 4, then 8, then 16.... The cancer cells may be able to stop themselves self destructing.  Or they may self destruct more slowly than they reproduce, so that their numbers continue to increase.  Eventually a tumour is formed that is made up of billions of copies of the original cancerous cell.  Scientists describe cancer cells as being 'immortal'.

1. They carry on reproducing  2. They don't obey signals from other neighboring cells 

Cancer cells do not obey signalsSomething in the cancer cells overrides the normal signalling system.  This may be because the genes that tell the cell to reproduce keep on and on firing.  Or because the genes that normally tell the cell to stop reproducing have been damaged or lost.  So the cancer cell keeps on doubling, regardless of the damage the extra cells cause to the part of the body where the cancer is growing

3- They don't stick together

Cancer cells do not stick togetherCancer cells can lose the molecules on their surface that keep normal cells in the right place.  So they can become detached from their neighbours. This partly explains how cancer cells spread to other parts of the body.

4- They don't die if they move to another part of the body

Cancer happens when cells that are not normal grow and spread very fast. Normal body cells grow and divide and know to stop growing. Over time, they also die. Unlike these normal cells, cancer cells just continue to grow and divide out of control and don't die.Cancer cells usually group or clump together to form tumors (say: too-mers). A growing tumor becomes a lump of cancer cells that can destroy the normal cells around the tumor and damage the body's healthy tissues. This can make someone very sick.Sometimes cancer cells break away from the original tumor and travel to other areas of the body, where they keep growing and can go on to form new tumors. This is how cancer spreads. The spread of a tumor to a new place in the body is called metastasis (say: meh-tas-tuh-sis).

5- They don't become specialized, but stay immature

Unlike normal cells, cancer cells do not carry on maturing once they have been made. In fact, the cells in a cancer can become even less mature over time. With all the reproducing, it is not surprising that more of the genetic information in the cell can become lost. So the cells become more and more primitive and tend to reproduce more quickly and even more haphazardly.