What is HPV? Why does it cause cancer?

I am lucky, in some ways, that I have an honours degree from a really good university in molecular biology where I specialised in cancer research, and that I  am now doing a PhD in cell biology as it means I can understand some jargon – although I’ll admit that sometimes it can make things seem a little more scary. But the truth is, I’m just a girl, like you, who was thrust into a world that freaks me out, and that I needed to try and work my way through understanding it.

In this blog post, I basically want to try to make it clear what HPV is and why it is linked to cervical cancer. I think the best place to start is by discussing what is on the NHS website “http://www.nhs.uk/Conditions/Cancer-of-the-cervix/Pages/Introduction.aspx” where there is an introduction to HPV. In their article it reads..

“Almost all cases of cervical cancer are caused by the human papilloma virus (HPV). HPV is a very common virus that can be passed on through any type of sexual contact with a man or a woman. 

There are more than 100 different types of HPV, many of which are harmless. However, some types of HPV can cause abnormal changes to the cells of the cervix, which can eventually lead to cervical cancer.

Two strains of the HPV virus (HPV 16 and HPV 18) are known to be responsible for 70% of all cases of cervical cancer. These types of HPV infection don’t have any symptoms, so many women won’t realise they have the infection. 

However, it’s important to be aware that these infections are relatively common and most women who have them don’t develop cervical cancer.”

I suppose my first issue with what they’re saying is that it is they say that most people who have HPV don’t have any symptoms, and yes that’s true. However, you’ve probably been told you have a patch of abnormal cells on your cervix, and that’s a symptom…My second issue is that they say most people who have the infection don’t get cervical cancer. Again, this is true, but the nature of the statement is kind of cold, right? And then you think well “why me?”. At that point, they leave us on a cliffhanger, wondering why we’re the black sheep. Why do we have cancer-causing HPV when others don’t? … Along comes anger/confusion/tears/hurt.

I found this website “http://www.biology-pages.info/T/TumorSuppressorGenes.html#hpv” during my degree as I  was studying for finals and I think that it’s good at explaining the molecular biology behind why HPV can cause cancer. It’s not easy to understand though, so I’m going to attempt to explain it as I did to my mum when she asked me about it..

It’s important here to understand first of all that, when you have a tumour (I prefer saying this to “have cancer”), you have a bunch of cells that are dividing too much. Excessive cell division = tumour causing. Secondly, like bacteria, viruses infect cells and can literally push their DNA and proteins into your cells. When HPV infects your cells, it pushes proteins into your cervical cells that bind to good “anti-cancer” proteins that belong to your cells. When this binding happens, the HPV proteins essentially mask your “good” proteins and stop them from acting to stop excessive cell cycling. So, the HPV makes some people’s cells cycle excessively to give cancer-like characteristics. The knock on effect of this is that your cells start behaving more like cancerous cells than non-cancerous cells. What happens? Well, their nucleus expands, they get bigger, and they are more ready to divide (the nucleus swells before cell division). This is actually how they discover we have abnormal cells – after a smear or biopsy, “cytology” is used to look at your cells and HPV infected cells have different structure and larger nuclei compared to  healthy cells, and so they are coined “precancerous”.

After receiving biopsy or smear results, you will be told what grade of Cervical Intraepithelial Neoplasia (CIN) you have – i.e. how abnormal do your cells look when the cytologist in the lab looks at them down a microscope. The larger the nucleus and the more abnormal the cell looks, the higher your grade of dysplasia. Grade 1 dysplasia is low, 2 is moderate, and 3 is high. Normally, treatment will be offered to you if you have grade 3, but for some people like me, you will spend a lot of time drifting between grade 1 and grade 2. This is happening because your cells are remaining infected with HPV and still appear to have a large, nuclei meaning they’re ready to divide. This is happening because your immune system and some good parts of your cell remain, stopping them from turning fully cancerous and dividing like mad. However, the fact that the abnormal cells are there means that you’re fighting it, but not quite eradicating/getting rid of the HPV.

You might now wonder why your cells are HPV infected and “weird”, when other people have HPV and their cells are just fine. This is a misfortune we need to accept for now – their immune systems are better at destroying the virus and any of their cells that were infected with it. Our immune systems aren’t coping quite so well, but if you read on, I will touch on ways I think you can boost your immune system and support it as it tries to win this battle for you.

 

 

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