Cancer cells and genetic alteration

A normal cell becomes a cancer cell when there is a genetic alteration. The behaviour of the cell comes from the information in the nucleus: the chromosomes, the DNA. In a cancer cell, what we have is an alteration of the information of the cell’s “decisions”. When this alteration happens, it’s possible that the pathway that makes the cell proliferate becomes active without any signalling. There should be an external signal that orders the cell to start proliferating, but a cancer cell proliferates without this external signal.

Cancer cells also have inhibition of apoptosis. The definition of apoptosis is “the controlled death of the cell”. Cells have a mechanism that decides when they’ve lived long enough and it’s time for them to die. Cells also apoptose if they detect that something’s wrong with themselves. If the cell detects a big mutation, it increases a specific protein, named p53, which makes the cell disappear, because it knows that it can be dangerous.

This also happens, for example, when we go to the beach and spend a long time exposed to UV light. The cells in our epidermis exposed to UV light start to apoptose because they detect big changes in their DNA.

There are at least three events that can explain why cancer cells carry genetic alterations. One is the atmosphere, or external signals: smoking is dangerous, food that has been washed with chemicals can also be dangerous. Why can external signals – smoking, chemicals, UV light – turn a normal cell into a cancer cell? What we know is that they modify the DNA, the information that is inside the cells: the methionine, adenine and cytosine. So, when the cell divides, this information is no longer kept and is altered by the daughter cell. The daughter cell carries something that can be dangerous for the cell; and if this “something” is a protein or a gene that facilitates proliferation, it will become a tumour.

One of the main causes of cancer is pollution – chemicals – but there is another source that turns normal cells into tumour cells: viral infections like papillomavirus and hepatitis B or C. In those cases, the virus infects the cells by carrying proteins with this information. The cells that carry the virus alter the DNA, and this alteration can make the daughter cells become more proliferative and less sensitive to apoptosis, which inevitably leads to a tumour.

There could also be an inherited predisposition to cancer. We heard about Angelina Jolie, who had a mutation of a protein named BRCA that makes carriers of this mutation more sensitive to breast cancer.