What are cancer stem cells?

Normally, stem cells dispersed throughout the human body remain dormant until they are needed for repair and replacement of damaged tissue. These special primitive cells can reproduce, creating more stem cells.

But stem cells are not like most body cells precisely because they have not differentiated into certain types of cells, such as heart cells, brain cells, skin cells or any other type of cell. another cell.

In fact, stem cells can become any type of body cells once activated.

When tissues are damaged, the stem cells of the region activate and start to generate cells – called progenitor cells or daughter cells – which are more mature but not fully developed cells.

These, in turn, can develop into any type of cell needed – muscle cells, skin cells, liver cells, and so on.

Stem cells can form any type of tissue cell in the body, making them very useful, for example, to replace heart cells damaged by a heart attack or liver cells damaged by injury.

In the past, it was thought that cancers developed from normal cells whose DNA was damaged by free radicals. The theory was that the cells mutated and became "immortal".

Because such (cancerous) cells do not control their reproduction, they continue to grow and invade other tissues to the point of killing a person.

It made sense – but there were things that did not fit that idea.

For example, we have seen cells that have so much damage to DNA, but never become cancers. It is also known that 50% of women who enjoy long-term survival after the disease have live cancer cells floating in their blood. But their cancer never comes back.

We can use powerful chemotherapy drugs and radiation to destroy cancer cells, but in most cases, the cancer recurs and often becomes faster and more aggressive than it was before.

In other cases, a person seems to be totally free of cancer, but the cancer reappears decades later. None of this makes sense if the old cancer theory was true.

An innovative theory of cancer, which was virtually ignored, involved the trapping of primitive embryonic cells (called trophoblasts) in some tissues and the formation of cancers over time.

It was before we knew about stem cells. The new theory is that chronic inflammation generates storms of free radicals that damage stem cell DNA, prompting them to start producing a massive number of new daughter cells.

Imagine the cancer stem cell as a bubble blower and the huge number of cells it generates in the form of millions of bubbles coming out of its ring.

As long as you blow on the soapy ring, it will continue to produce bubbles (daughter cells). These bubbles represent the major part of the tumor.

It is estimated that stem cells do not represent more than 1% to 10% of the mass of a tumor, the rest being daughter cells.

What has been discovered is that chemotherapy and radiotherapy can kill daughter cells, but cancer stem cells are totally resistant to these treatments.

If you remove or destroy most of the tumor (the daughter cells) with chemotherapy and / or radiation, while leaving some of the cancer stem cells, the tumor will reappear.

This explains why tumors recur in 90 to 95% of cases of metastatic cancer treated with traditional therapies, because the cancer stem cells are not damaged.

But cancer stem cells have their own control systems, so the tumor may not return for months, years, or even decades.

Some have suggested that the daughter cells that make up the bulk of a tumor may not be malignant and not spread to other parts of the body – which kills cancer patients.

On the other hand, when cancer stem cells spread throughout the body, new tumors can be generated, just like the cells of origin, and are just as deadly.

The idea that girls tumor cells are not really cancer is not resolved yet, but it is clear that they are not the main culprits in cancer cases.