Cell Death

2025 April 1st

So, it’s day 8. The post chemo week’s not been a comfortable one this cycle - quite a lot of flaking out and hiding for a nap in the day, avoiding driving albeit getting some work done but concentration pretty poor. Only the last two days have I really felt like any exercise. However, I’ve got through it; last night I had the first full and uninterrupted night’s sleep in a week, and this afternoon after what resembled a full day’s work I enjoyed a pleasant half hour walk through the woods. I’m on recovery track now, thank goodness. And thank all available deities that this is the penultimate cycle of chemo, so hopefully I’ll only have to go through this once more.

Ever.

Anyhow, in the meantime, with what mental capacity I’ve had this week I’ve been trying to understand a few things. Most especially, I’ve been trying to understand both how chemotherapy works, and how cancer works. I wasn’t totally surprised that the two are very closely linked. So, let’s see how well I can explain both in around twelve hundred words.

We’re made up of cells, which each contain the DNA that defines the form of all life. A debate can be had about whether cells exist to support the human body, the human body to support cells, or we’re all there to support DNA. It’s all a bit academic really, as we’re all in this together - but we do know that those cells multiply and divide from time to time. The rate will depend upon the nature and location of the cell: stomach lining cells reproduce very fast at around every 4-5 days, followed by skin cells at around fortnight, liver cells around twice a year, and brain cells hardly ever after birth. Each time the cells divide they also reproduce their controlling DNA, which usually goes fine but occasionally happens with errors.

It’s a bit like photocopying a page from a book, then photocopying the photocopy, then doing the same again. At first the photocopies look absolutely fine, but with multiple copies they get steadily worse, until eventually the copies are unreadable and useless. At that point the only sensible thing to do is throw the bad copies away and go back and copy from the original book again.

This, fundamentally is what the body does too. When the DNA (think of the words on the page) gets too damaged (unreadable), this is detected by adjacent cells which force it to destroy itself. This is called “cell death” specifically a mechanism called “apoptosis”. It’s how DNA maintains its own purity within the body, and the body prevents itself from mutating uncontrollably.

A cancerous cell has two particular properties. Firstly it is more rapidly reproducing than healthy cells: taking my prostate for example they’ve probably been reproducing around every 2-4 months, compared to every 1-2 years in a healthy prostate. Secondly they have learned to disable the mechanism for apoptosis - whilst the surrounding cells may well detect the damaged DNA and try to trigger cell death, they get ignored. And that’s how a tumour grows: too rapidly reproducing cells, which ignore the self destruct signals. And of course, unchecked, it’ll keep growing until it destroys the surrounding body, and the host dies of cancer. This, speaking personally, I am trying hard not to do.

So what’s this got to do with chemotherapy? Well chemotherapy, in my case a drug extracted from yew tree bark called Docetaxel (the picture above is of its molecule, and below is of the pacific yew it was originally extracted from) acts on rapidly dividing cells and does two things. Firstly it prevents cell division, secondly it tells those cells that originally wanted to divide rapidly, to self destruct. A very sophisticated poison in other words. One that’s fairly bad for me, but much much worse for the cancer cells in me. So the plan, with its regular injections into the body, is that the poison kills the tumours in a cancer faster than either it, or the cancer, can kill the host.

This brings us to side effects though. As I mentioned earlier, cancer cells aren’t the only ones in the body that are trying to reproduce rapidly. Skin cells do (that’s how we don’t end up with horrible scars every time we get a bruise or cut), and so for example do the cells in the bone marrow that create both white and red blood cells, and hair follicles. Those last two can reproduce more than once a day, which makes even cancer cells seem slow to reproduce. So, hardly very surprisingly, those get affected by the chemotherapy too.

In my case, I’ve got off pretty lightly. Whilst my hair has thinned, it’s not fallen out - in fact my hair has mostly gone from grey to white which I think looks rather distinguished, even if there’s not much of it. I’ve been taking care, mostly successfully, to avoid sources of any infection, and whilst the skin in a few spots (hands, feet, inside my nose) has got a bit dry and sensitive, it’s all been manageable with moisturisers and Vaseline. I’m not saying for a moment that chemotherapy has been a walk in the park: I’m hating it, but I’m managing it. And it does help, for me, to try and understand what’s going on in my body.

Let’s skip back a bit to another question. What makes these cancer cells proliferate in the first place? Well it’s to some extent bad luck - the whole multiple photocopies thing. Sometimes though it’s down to self inflicted damage. If we put bad things in our body: pollutants in contaminated drinking water, tar from cigarette smoke, too many preservative containing bacon sandwiches, you get the idea: then we create hostile environments in particular parts of the body. In those hostile environments, relatively healthy cells, if their DNA gets damaged, are likely to be forced to self destruct. But mutant cells with a faulty self-destruct mechanism have an evolutionary advantage and are more likely to survive and reproduce. And there everybody is fundamentally why so called “unhealthy” lifestyles make you more likely to get cancer. Frightening isn’t it, but at least it’s something we can try to do something about if we care enough to make those adjustments to our lifestyles.

One last question I was looking into. Why can’t we use chemotherapy alone to kill the cancer? Why do we need to use other methods, such as other drugs, or radiotherapy? Well it’s down to the mutation, and tendency to mutate, of the cancer cells again. Basically the bloody things keep mutating and some of them: not many, maybe one in a billion, but enough to be a problem, will find a mutation that lets them survive the chemotherapy. So we need to send in radiotherapy, or other drugs, as a clean-up crew to deal with the survivors. No mercy!

More simply also, it’s really obvious that the chemotherapy is very bad for the person it’s being injected into - and you can’t just keep going with it every three weeks indefinitely without doing permanent damage to them too. You have to stop at some point or you just kill the patient a different way. No thanks, I’ll skip that.

Well that’s my best attempt at understanding it anyhow. If anybody with an actual medical degree can explain it better, I’m all ears.