Trying to develop new ways to treat cancer is a very tricky thing. All cancers are unique and even a single tumor is a mixture of a bunch of cells with different varying mutations meaning that there will be different responses to a given drug treatment. The mutations keep coming too, therapeutic cancer drugs may not have a strong effect over a long period of time – the length of time needed to clear the cancer.
Cancer drugs need to be really, really specific in the cellular machinery they affect too. Targeting things like cells that are growing too rapidly or specific cellular protein regulators cell growth. One of the biggest problems to overcome is that cancer cells originate from our cells, they’re still human cells with the same basic machinery as the rest of our cells. How do you target something so subtly different but dangerous without harming the healthy cells?
Radiation therapies are making big gains with techniques that can focus and target radiation to specific sites of the tumor(s). But that can’t handle every cancer or clear the cancer entirely because it’s based on how much we effectively see of what we interpret to be cancerous tissue. Chemotherapies have also made improvements but are still a brutal assault on the body. Trying to find highly specific and targeted approaches to destroy just the cancer while also not putting people through even more hell has been a big aim by medical practitioners and researchers.
Enter the viral infection. It seems almost counter intuitive to cure cancer is to make someone sick with a virus. But it’s actually a really sensible approach to use a viral infection to kill cancer cells. The majority of viruses are actually very, very particular about which cells they infect. It’s called its tropism to describe the specific cell type that a virus preferentially infects. Viral tropisms are why common colds only infect your sinuses and throat, the flu only infects your lungs, norovirus your gut, shingles your nerves, etc. Another really neat feature of viruses is that the majority of them don’t actually cause any noticeable effect or disease when they infect us. It’s actually in a virus’ best interest to not kill its host but just happily and quietly go along for the ride. This is why viruses are a good idea to use against cancer, surely there’s a magic bullet out there that can be made to be highly specific for specific cancer cells yet overall be of little risk for causing disease.
There has been a push for a long time now and we’re finally getting there now that biotech. firms are starting to roll out development of oncolytic viral therapies. That word “oncolytic” describes what the mission of the virus is. “Onco” is just medical jargon for cancer and “lytic” means effectively bursting, so “oncolytic virus” is a cancer bursting virus. This is specifically referring to single cells being popped like little microscopic water balloons, not the whole cancer tumor bursting within someone – that’s just a horrific thought.
Cancer cells do have distinct differences from normal healthy cells. All cells are little bags of life and that outer life encapsulating bag is the cell’s membrane. There’s a lot of proteins that exist on that membrane that are used for an array of purposes that allow cells to sense their environment; cling to other cells and surfaces; and, in this instance, communicate with other cells pretty much being badges and i.d. tags. Viruses exploit these badges and sensors by adhering to them and then invade a cell. In the case of oncolytic viruses there’s certain badges that only cancer cells end up displaying in significant numbers which a virus can be made specific to in a lab. So, it’s of highest probability that the virus gets within cancer cells and then also exploit the unique rapid growth pace and cranked up machinery of a cancer cell the virus can then exploit that as well to produce more of itself and fill that cancerous bag so full of new virus that it rips it open spreading a whole bunch more virus to neighbouring cancer cells.
In theory, the use of oncolytic viruses could clear all the cancer and once there’s no more cancerous cells the remaining virus just degrades or is eaten by healthy cells as food. With everything in medical science this isn’t meant to be a cure-all for cancer or replace every other therapy but the use of oncolytic viruses has a great potential to be a very powerful new tool to improve our chances against cancer.
Here’s a couple recent scientific articles reviewing the current state of oncolytic viruses if your interested in really diving into more of the details and science: