Over the course of this blog, I’ve tried to explain lots of stuff. I’ve covered subjects such as risk factors, what causes cancers to start growing, how different treatments work, what causes side effects and the decision-making processes that doctors use to plan a patient’s treatment. And I hope I’ve managed to do it in a way that makes sense to readers without a scientific or medical background.
But the main aim of this blog has been to try and highlight the differences between the commonly held perceptions of cancer and the reality of this disease. And if this blog has done its job, then you will have spotted the deliberate mistake in that sentence. If you have, well done! Give yourself a Gold Star! And if you didn’t spot it, the answer is at the end**, (although if you read through the rest of this post, rather than skipping straight to the end, it might give you a big clue!)
But I digress. The aim of this post is to discuss another common misconception. I’ve mentioned before that cancer patients often describe their tumour as a strange, alien “thing” that has invaded them. Now, as I discussed in No Cure For Cancer…?, this is inaccurate. The patient’s tumour isn’t an alien invasion, it is part of them. But there is a second inaccuracy in this notion that a tumour is an alien “thing” that I want to cover in this post – and it is the idea that the tumour is a single “thing”.
It’s an easy mistake to make. As a tumour forms, it grows as a single mass. Even if the cancer is malignant and spreads, the patient ends up with two (or more) tumour masses, in separate locations. And the most important word in the last paragraph is “mass”. I used that word deliberately. What is a “mass”? If you look up “mass” in the dictionary, you’ll find several definitions, but the one we are interested in is this one: “a large number of people or objects crowded together”. This is what we mean by a tumour mass. And this is the point I want to get across in this post. A tumour is not one single, big thing. Instead, it is made up of a huge collection of little things, namely cancer cells.
Look at the picture to the left. Image A is how most people visualise a tumour – as one big lump. Now look at Image B. This one is closer to the truth. A tumour is made up of lots and lots of little things – cells – all grouped together. And, of course, it’s not just the tumour that is put together like this, your whole body is made the same way. Every organ is made up of millions of cells, organised just right.
So, time for another of my Tortured Analogies (I know you love ’em!) Think of your body like a huge crowd, say a crowd of football supporters. Now, most of the time, in most grounds, the crowd obeys the rules. The crowd goes through the right turnstiles. The crowd uses the right stairwells. The crowd goes to the correct sections of the ground. The crowd sits in the right seats. The crowd cheers in the right places, boos in the right places and sings the right songs.
But, of course, it is not the crowd that is doing all these things, because “the crowd” is not one single thing. Instead, it is made up of a huge number of individuals. And it is the individual supporters who are doing all of these things. Certainly, the individual members of the crowd talk to one another, but it is the individual who makes the decision to stick by the rules.
Now imagine that, in among the crowd, there is a hooligan element. The hooligan element barges its way through the wrong turnstiles. The hooligan element runs up the wrong stairwells, into the wrong sections of the ground. The hooligan element rips up the seats. The hooligan element sings offensive songs. The hooligan element invades other sections and starts fighting. The hooligan element refuses to leave at the end….
But, again, it’s not the hooligan element that is doing all this, because “the hooligan element” isn’t one thing either. It is also made up of individuals and it is the actions of individual eejits that ruin it for everybody. And, granted, all of those individual numpties may behave in a similar way, but that doesn’t mean that they will always behave the same….
Much the same situation happens in cancer. A tumour is not a single big lump, as in Image A above, it is a collection of individual cells, like in Image B. And, like the hooligan crowd, all of those individual cancer cells may behave in a similar way, but that doesn’t mean that they all will, all the time. This can help explain how a malignant tumour spreads. You may remember that I said, back in No Bootees, that a tumour turns malignant because it starts producing growth factors (Go! signals) that encourage bits to break off and start floating round the bloodstream. But that is slightly wrong, because it assumes the tumour is a single thing, rather than a collection of individual cells. And it is the behaviour of the individual cells that is important.
So, going back to our hooligan analogy, imagine a situation where all of them are ripping up seats. But then, some of them decide it’d be a good idea to invade another section and start a riot in there. Now, the ones who have this idea don’t bother checking with everybody else before they do it, they make the decision themselves, they just go. Likewise, in the tumour, the Go! signals that encourage malignant cells to detach & spread won’t be produced by the entire tumour, but by a small number of individual cells, which then detach & float away.
But! It gets worse! Going back to our hooligans, imagine that once some of them have invaded another area, they then turn back and shout out to the ones they left behind, urging them to do the same. And some of them think, “Hey, that’s a good idea, I think I’ll do it too!” And then this second bunch jump into other sections too.
Well, recent research suggests that cancer cells can do the same. So, while, initially, it will only be the tumour cells which produce the malignant Go! signals which detach and float away as in Image C on the left, they can communicate with the tumour cells left behind, by releasing factors which cause the non-invasive cells to turn invasive, as shown in Image D.
So, in future, keep an eye on your crowd. And if you think some of them are misbehaving, do something about it ….. before your stadium gets trashed.
** Did you spot the deliberate mistake? I described cancer as “this disease”. But, of course, as I’ve said before, cancer isn’t a single disease! It is a large collection of different diseases!
Zomer, A., Maynard, C., Verweij, F., Kamermans, A., Schäfer, R., Beerling, E., Schiffelers, R., de Wit, E., Berenguer, J., Ellenbroek, S., Wurdinger, T., Pegtel, D., & van Rheenen, J. (2015). In Vivo Imaging Reveals Extracellular Vesicle-Mediated Phenocopying of Metastatic Behavior Cell, 161 (5), 1046-1057 DOI: 10.1016/j.cell.2015.04.042
AG McCluskey (2015). One Of The Crowd Zongo’s Cancer Diaries