Thanks to Brilliant for  supporting this SciShow video!

As a SciShow viewer, you can keep  building your STEM skills with a 30 day free trial and 20% off an annual premium  subscription at Brilliant.org/SciShow. If you’ve had the vaccine  for human papillomavirus, you might know that it dramatically  reduces your risk of certain cancers.

What you might not know is how efficiently HPV has both our immune system and  our cancer defenses figured out. While many versions of this  virus are mostly harmless, some are actual biological supervillains. And like the best supervillains, they  know how to hit the heroes where it hurts.

It’s an almost perfect model of how badly  our cells need their anti-cancer toolkit… and what happens when that toolkit is taken away. So let’s talk about what makes HPV such a unique entry in our  biological rogues’ gallery. [♪ INTRO] Cancer is when a person’s cells begin  to multiply rapidly and uncontrollably, like a rebellion of certain  cells against the body itself. But our cells have a whole host of  checks to that rebellion, though.

If cancer is uncontrolled cell division, it follows that cell division  is normally controlled. We have many of these so-called tumor suppressors, genes that keep normal, healthy  cell division chugging along. The most notable of these heroes are p53  and the retinoblastoma protein, or RB. p53 is basically the guardian of your genes.

Its job is to patrol the nucleus of the  cell, looking for any suspicious activity. This includes searching for damaged  DNA, which can turn a cell cancerous. If p53 finds damaged DNA, it  offers the cell a harsh ultimatum: either you get well again fast,  or I’ll send you to the gallows!

That is, p53 figures out which cells can  be repaired, and which should be killed. It has the ability to  temporarily suspend cell division and let the cell attempt to repair its DNA. If the repair is successful,  p53 allows division to go ahead, but if not, p53 sends for proteins that  will initiate programmed cell death instead.

The other key tumor suppressor we  mentioned, the retinoblastoma protein, functions more like a general. That’s because RB is in charge  of keeping the cell cycle chugging along at the perfect pace. The cell cycle is simply the multi-phase  process by which cells divide, often represented sort of like a clock.

RB prevents the cell from duplicating its DNA, which is the point of no  return for the cell cycle. But once it receives enough signals from  its lieutenants that everything is ok to go ahead, RB will allow other proteins to  deactivate it, and cell division can go ahead. So when RB dishes out  tight-fisted orders to its troops, it’s only to make sure the  cells don’t replicate too fast and spin out of control,  thereby becoming cancerous.

And much like p53, if the cells don’t  listen, RB can order them to be executed. It’s hard to overstate how important  these two microscopic heroes are to human beings, because over 50  percent of all human cancers feature a glitch in one or both of these proteins. Almost like Batman in Gotham  and Superman in Metropolis, these tumor suppressors use different methods to watch over their domains  and keep everyone safe.

So, if you were trying to engineer a  cancer, you’d have to find a way to get p53 and RB out of the way, right? Well, that brings us back to that villain HPV. While there are many varieties of HPV,  and many clear up quickly without causing serious problems, types 16  and 18 are the main cause of most cervical and certain  throat cancers worldwide.

HPV infiltrates the body through  a tiny wound or abrasion. It then dives deep into the skin, and hijacks  the nucleus of a stem cell living there. And then, like the worst AirBNB renter,  it starts using the cell’s own equipment to replicate and spread copies  of itself to neighboring cells.

Now, normally, your immune system  would be the first line of defense against a virus, but that’s where  this virus gets especially nasty. See, HPV has developed a way  to avoid the immune system that just so happens to also turn cells cancerous. Now, I know what you’re thinking:  shouldn’t our tumor suppressors come to rescue the cell from this hijacking?

Unfortunately, it’s not that simple. Because like all movie villains,  HPV has a secret weapon. The virus starts to make two proteins, E6 and E7.

These goons loiter around the  nucleus and the cytoplasm, looking to cause trouble by binding  to certain healthy cellular proteins. They’re especially good at  sticking to our tumor suppressors, p53 and RB, and inactivating them. So when they meet, our heroes are as powerless against these proteins as  Superman facing kryptonite.

To add insult to injury, E6  then turns on telomerase. This little enzyme keeps  the ends of our chromosomes stocked with enough genetic  material to constantly replicate. So, with the body’s caped crusaders neutralized, and cells able to ignore all  damage and divide without limit, the result is an astonishingly  efficient route to cancer!

And the only thing that’s necessary  is an extremely common virus. But if that sounds terrifying to you,  there’s still reason to be optimistic. The CDC recommends that most young  people get vaccinated in their preteen years, before they’re likely to be exposed to sexually transmitted infections.

And even if you never got the shot as a child, scientists are working on another tool  to give our bodies’ hard-working defenses a hand: it’s an mRNA vaccine,  like many of us got for COVID-19. Instead of injecting a weakened version of HPV, this type of shot actually provides the  immune system with the instructions for how to recognise E6 and E7, so the immune cells can fight HPV-tumor cells directly. Shutting down the virus’s key weapons  gives your body the ability to fight back against the malignant cells, so it’s kind of like a cure  for cancer in a handy shot.

Which is exactly the kind of strategy we  need to fight a supervillain like HPV. This SciShow video was supported by Brilliant. Brilliant offers online courses in  math, science, and computer science, like their Programming with Python course.

After just 19 lessons, you’ll know how to give instructions to a computer  in a whole new language! Kind of like how the HPV shot  gives your body instructions for how to fight E6 and E7 proteins. And after taking this Brilliant course,  you’ll have the tools to do so much more, from coding video games to visualizing data.

To get started, head to Brilliant.org/SciShow or hit the link in the description down below. You’ll get a free 30-day trial and 20% off an annual premium Brilliant  subscription by using that link! And thank you for watching this SciShow video! [♪ OUTRO]