What is cancer?

A DEFINITION

Cancer is a disease mainly characterized by an abnormal multiplication of cells in one part of our body: our lungs, our liver, breasts, colon, brain…

There are many types of cancer. Each type of cancer is unique, and though two different people may both suffer from liver cancer, for example, the cells that compose their tumours are not identical, especially at the molecular level.

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CELLS THAT MULTIPLY...

A tumour is composed of billions of cancer cells.

Cancer cells come from an initial cell which became cancerous following an accumulation of mutations, and as a result began to multiply indefinitely.

The mass of cells resulting from such an abnormal multiplication of cells forms a tumour.

After each division, cancer cells can acquire yet other mutations. As a consequence, the cells belonging to one same tumour are not all identical.

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ODD BEHAVIOUR

Cancer cells have all kinds of peculiar behaviour:

 they do not repair their DNA well and, as a result, accumulate mutations

they do not react to signals that regulate cell division and, as a result, divide incessantly

they need a lot of oxygen and nutrients that are found in blood. Cancerous cells that have acquired the capacity to induce blood vessels are even more active than usual.

 they have acquired the capacity to invade tissues surrounding the tumour. They can also depart from the tumour to form metastases that will invade yet other tissues in our body.

 they are unable to commit suicide and thus become immortal

they are able to shun the immune system

A QUESTION OF MUTATIONS AND ALTERED PROTEINS

The unusual behaviour of tumour cells is due to an accumulation of mutations in their DNA.

As a consequence, tumour cells are full of proteins whose function has been altered – in particular those involved in cell division and survival.

Yet other mutations modify the expression rate of certain proteins – in particular those involved in regulating our immune system or in making blood vessels. As a consequence, the biological processes involved are faulty.

Several hundred proteins, when altered, are thought to be involved in cancer.

This altered protein does not control cell division anymore.

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CHARACTERIZING CANCER TODAY

Today, cancers are characterized according to three features:

1. the type of organ that is affected (lung, liver, breast, colon, brain…)

2. the type of tissue and the type of cells which initiate the cancer

3. the tumour’s DNA profile, i.e. the list of mutations and altered proteins present in the cancer cells.

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LINK BETWEEN DNA PROFILING AND PERSONALIZED TREATMENT

DNA profiling gives the list of mutations present in the DNA of tumour cells. As a result:

1. researchers can find the altered proteins responsible for the cancer’s progression (support for diagnosis)

2. researchers can identify the mutations that could modulate a given treatment (choice of treatment).

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HOPE...

PERSONALIZED TREATMENT

By targeting only the altered proteins found in cancer cells, personalized treatment specifically attacks only cancer cells thereby doing the least possible damage to normal cells and limiting side effects.

By using drugs that have been chosen according to a patient’s history and the genetic data of his/her tumour, targeted cancer therapy has a greater chance of success.

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