Cancer stem cells 101: introducing a not-so-friendly tumour player

by Vanesa Cepas-López

The following Blog has been developed by one of the participant of the recent MCAA ECS Satellite event on Science Communication.
During the workshop, participants were invited to work on a scientific blog and submit their final piece to be published on the MCAA Blog.

The piece has been revised by a task-force of the MCAA Communication Working Group. Members of the team included: Maria Montefinese, Luisa Merz, Ashish Avasthi, Pradeep Eranti, Nicoleta Spînu, and Ruben Riosa.

Enjoy the piece!

Stem cells are a trending topic. We often hear this word in the news or even in TV shows. But do we really know what stem cells are?

Stem cells are not like normal cells. They are cells that have the ability to divide infinitely and to differentiate (specialise) into other cell types with particular functions. For example, there are stem cells in the blood that can divide to give rise to more stem cells, or they can differentiate into the wide variety of cells that are present in our bloodstream.

But, did you know that we can also find stem cells in tumours? They are the so-called “cancer stem cells” and are very relevant because, in many cases they are responsible for the development of metastases and tumour relapses.

Cancer stem cells, as all stem cells, have two main functions: they can divide to maintain their numbers unaltered, or they can differentiate into the various cells that form the tumour.

This would be too easy, so let’s make it a bit more complex now. There are not only one but two different kinds of cancer stem cells in tumours.

On the one hand we have the lazy mesenchymal cancer stem cells. They are mostly dormant and hardly ever divide, and they provide a cell “reservoir” for the tumour.

On the other hand, we find energetic epithelial cancer stem cells. They are really active and divide rapidly, providing the tumour with an army of fresh specialised cells.

Very likely, you’ve heard of radiotherapy or chemotherapy. They are conventional cancer treatments, and they target cells that are rapidly dividing, like the majority of tumour cells. But, as we have just learned, there is one kind of cancer stem cells that, in fact, rarely divides.

So, what could happen after conventional therapy? The sleeping beauty population of mesenchymal cancer stem cells might wake up and realise that the other cells have disappeared. In that case, they activate their emergency plan, get really active, and start reproducing to again start the tumour, which is what we call a tumour relapse. Sometimes, these cells exit the defined region where they used to live and transfer through the bloodstream to other unexplored parts of the human body, which is what we call metastasis.

As you can see, these cancer stem cells are a big deal and should not be underestimated. Indeed, the new treatment strategies are focused towards the target and elimination of these cells. Now you know why!