The capacity for a cancer to escape the control system of the human body (immune system), and create metastases in other parts of the body.
 

Further information :

Our organism possesses mechanisms that are activated at cellular and molecular level to combat the onset and development of a cancer. However, these mechanisms are sometimes diverted by cancerous cells.

The organism is monitored by the immune system

The cells of our organism are under constant surveillance by the immune system.

It is like an anti-missile defence system with homing devices, radar systems and drones. The immune system is responsible for checking whether our organisms is infected by an aggressor (pathogenic agent) or invaded by abnormal cells as in the case of cancer. It is the defence system that acts to protect us against diseases, poisons, and pathogenic agents like viruses, bacteria and parasites.

This surveillance is ensured by the presence of molecules on the surface of the cells: these fragments are called antigens.

A healthy cell has antigens on its surface that are recognised as belonging to our organism: the self. This recognition can be performed by the effector lymphocytes of the immune system which have a receiver on their surface.

The antigens on the surface of a cancer cell have been modified. These foreign antigens are recognised by the effector lymphocytes as alien to our organism. Thus they are activated against the cancer cells and eliminate them.

The mechanisms of escape from the immune system

The cancerous cells can escape the surveillance of the immune system in different ways:

• The cancer cells may no longer present antigens on their surface. These cancer cells therefore become “invisible” and can no longer be eliminated by the immune system.
• Certain cancer cells may be slightly immunogenic, which means that their capacity to activate the immune system is weak. They present few or no foreign antigens on their surface and above all present self-antigens. Consequently, these cells are well equipped to escape the surveillance of the immune system and can develop and circulate more easily.
• The cancer cells can also escape the surveillance of the immune system by impeding its action against the cancer. In this case, the cancer generates an immunosuppressive microenvironment that prevents its infiltration by the cells of the immune system.
• The cancer can also promote the recruitment of the cells of the immune system that inhibit the anticancer immune response such as macrophages and regulatory lymphocytes.

These strategies for bypassing the immune system allow the cancer to develop beyond any control.

See also :

Tumor escape, interview of Pr Alain Puisieux