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Go to Brilliant.orgSciShow to learn how you can give the gift of learning to someone you love! [ intro ]. People often wonder why there isn't a cure for cancer yet.

And the answer is usually because “cancer” isn't one thing. It's this big umbrella term for a ton of different conditions where cells grow out of control. While there are treatments for some types of cancer, different cancers are, well, different enough that there's nothing that works for all of them — no universal cure.

But, uh, it turns out there might be? Researchers from Cardiff University in Wales may have found a way to treat all cancers, or at least a whole lot of them. And they just kind of stumbled onto it.

The researchers weren't searching for cancer therapies. They were looking for ways to fight bacteria with immune cells called killer T cells. As the name implies, these cells kill things.

Specifically, things that aren't good for your body. But unlike other immune cells, they don't target bacteria or viruses directly. Instead, they go around interrogating the body's own cells, trying to sniff out ones that might be hiding pathogens inside them.

And when they find an infected cell, they kill it. But not all killer T cells are the same. There are different types that use slightly different proteins, called receptors, to check out cells.

Often, these receptors are somewhat specific to the invader they're hunting for. But the researchers were looking for a kind of T cell that can detect lots of different bacteria. So, they pulled a bunch of killer T cells from blood samples and tested their infection-spotting abilities.

The test the team was using just so happens to employ a kind of cancer cell that's easy to infect with bacteria. And a number of different T cells showed promise when the scientists set them loose on these infected cancer cells. But one was especially ruthless.

Unfortunately, in further experiments, it killed all of the cancer cells, not just the ones with bacteria inside them — so it wasn't what they were looking for. But it did pique their curiosity. Now, it's not that weird for a T cell to kill cancer cells, because T cells don't just hunt for infections.

They are also in charge of keeping cancers in check. And over the past several years, scientists have started harnessing the power of these cells to fight cancer. In CAR-T immunotherapy, for example,.

T cells are removed from a person's body, genetically programmed with a receptor which can spot the person's cancer, and then injected back in to seek and destroy. But we can't do this for all cancer patients yet because we don't have good receptor targets for every type or even subtype of cancer. You know, that whole “cancers aren't all the same” bit.

But I digress. Point is, it wasn't super surprising that the researchers had found a T cell that killed this particular type of cancer. But, before just discarding or shelving them to continue the hunt for bacteria-killing T cells, they decided to see what happened with some other cancer types, too.

And they worked. Against all of them. Lung cancer, colon cancer, bone cancer, breast cancer, blood cancer, skin cancer... these T cells killed every kind of cancer the researchers tried.

Not only that, but they left healthy cells alone. Which is, like, WHOAH. Needless to say, this sparked a new investigation into how these T cells were doing this.

To figure that out, the researchers deleted proteins from the cancer cells one by one using CRISPR-Cas 9 gene editing. The idea being that, if deleting a protein made the T cells ineffective, then that protein must be involved in how the cells are spotting cancer. And that led them to a protein called MR1.

Now, what's interesting about that, is MR1 can be found on all your cells, not just cancerous ones. See, it's thought to be an informant of sorts for the immune system. It samples molecules from inside the cell and presents them on the outside, where immune cells can take a look.

And that's exactly what these killer T cells seem to be doing. They have a special receptor that allows them to interact with MR1 proteins and read those samples. They're not the only T cells that interact with MR1, but they seem to be the only ones we've found so far that can spot all sorts of cancers by doing so.

The researchers were even able to take this receptor and stick it into T cells from actual cancer patients. So basically, the same idea as CAR-T therapy, but using this one protein instead of tailoring the T cells to each patient's specific cancer. And not only did those engineered T cells kill samples of the patients' tumors, they killed cancers from multiple patients.

That's probably because MR1 proteins don't really differ much between people, so the same receptor can recognize all of them. this means that instead of having to design individual therapies for each cancer, doctors might be able to use this one receptor to make T cells that work for everyone. But we shouldn't pop open the champagne quite yet. There are still some big unknowns here.

Like, the researchers don't actually know how the T cells are recognizing MR1. Seriously, the actual wording in the paper is that this receptor quote “does not recognize MR1 by known mechanisms”. And they don't know what MR1 is showing the T cells to alert them that the cell is cancerous — though, presumably it's unique to cancers and, if not universal, then at least super common.

Most importantly, though: they have yet to try these T cells in actual human patients. They did test them in mice given human cancers, and the results were promising. But it's still possible they won't work well in a real, live person.

We should know fairly soon. The researchers' current plan is to proceed cautiously, and if safety tests go well, they're hopeful human trials could start in the next few years. On the upside, even if this doesn't lead to a quote “cure for cancer”, studying these T cells could help scientists discover new ways to treat a lot of different cancers.

And the team is already on the hunt for other, similar T cells that can kill multiple cancers. And to think — this discovery would never have happened if the researchers didn't have the good sense to investigate further when some cells did something funny. Thanks for watching this episode of SciShow News!

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