SPEAKER_04

They're called major histocompatibility complex proteins.

So for instance, if I were to try to just randomly do a tissue transplant from me to you,

it's very likely that it would be rejected.

And it's because of those MHC proteins that it's rejected.

What's happening is that your cells are presenting your internal cell biology to the immune system, and it's saying, okay, you're a friend, not a foe.

So when cancer usually initiates, there are disruptions that happen and proteins are made incorrectly, et cetera.

And so what these MHC proteins are doing in some cases is they're presenting the internal damage to the body and the body is saying, oh, there's something wrong with this cell.

We better wipe it out.

We kill it.

These same proteins are what the immune system uses, for instance, to go after viruses.

So when you get a virus infection inside of the cell, the body has a way of chopping those proteins up inside of the cell, presenting it via MHC, and then the immune system attacks it.

So one of the first things that actually tumors do is they learn to turn off the MHC proteins inside of themselves.

So the ability to show that I'm damaged is shut down.

And so the immune system doesn't go on full alert for that.

But then there are other mutations like divide when you're not supposed to.

Avoid this kind of induced cell death called apoptosis and not others.

And so cancer doesn't just like start and then the next day you've got it.

It's a progression of events.

You have these precancerous lesions.

You have like a benign tumor, which eventually becomes a metastatic tumor.