Viruses can cause and cure cancer?

Our ever advancing understanding of viruses and their complexity, occasionally tips in our favour. 

We know that many viruses can cause cancer (oncoviruses), but we are discovering that there are also viruses that can kill cancerous cells leaving healthy cells untouched (oncolytic virus). 

A small percentage of people  infected with an oncovirus or ‘tumour virus’ will actually go on to develop cancer, there are many factors involved in determining the patient’s fate. 

Both viruses with RNA and DNA genomes can cause cancer. This requires the insertion or addition of oncogenes (cancer causing genes) from the viral genome to the host (human) cell. Alternatively, they might enhance oncogenes that already exist in the human genome. 

Human papillomavirus virus for example, combines DNA with the host DNA disrupting normal regulatory function and turning the cells cancerous. HPV is responsible for causing the majority of cervical cancer in women. 

Several viruses including Hepatitis C and HIV disrupt the normal functioning  of the immune system and leave them vulnerable to other cancer-causing viruses. HIV positive patients are 500 times more likely to develop some types of cancers than the average person. 

So what about the viruses that are “curing” cancer? 

Well they’re called oncolytic viruses. I.e. viruses that lyse cancer cancer cells. Lysis refers to the breakdown of a cell. 

Some naturally occurring viruses only enter and lyse cancerous cells because they are already engineered to recognise tumour cells. 

Tumorous cells have modified cellular pathways as they replicate in an unregulated cell cycle. Because of the way the cells replicate, they exist in a unique microenvironment that the virus cells are able to recognise. 

Scientists have begun to genetically modify viruses so that they can behave in this way if they don’t naturally recognise cancer cells.

By engineering viral cells to target cancerous ones, you can develop very specific therapies. It is miles more efficient than the typical chemo and radiotherapy that cannot distinguish between a healthy and cancerous cell. 

These are called cancer immunotherapies. A few viruses have already been approved for this type of treatment, it’s the latest and fastest growing type of cancer therapy. 

T-VEC, which has been modified from the naturally occurring HSV virus , is one example. The viral cells attach onto the cancer cell, interrupting its genome to replicate itself rapidly, so much so that the cancer cell basically erupts and dies, releasing and spreading the viral cells further.

In the current climate, there’s never been more money and more resources available for the field of virology, it is certain these remarkable cells will continue to surprise us, hopefully in our favour.