Shedding some real light on lung cancer
Paul Cowling, PhD student at the University of Edinburgh, received a commendation prize in our 2016 Max Perutz Science Writing competition. In his article, he explains how fluorescent molecules could help with early, and faster, diagnosis of lung cancer.
It is June, and twilight sets in over the bustling beer garden. I take a drink from my pint before returning my attention to my friend Chris who is ranting about the state of affairs at Newcastle Football Club. He finishes venting his anger over the team’s lacklustre performances and proceeds to light a cigarette.
I watch the embers glow at the tip as he inhales over 4000 chemicals into his lungs, 43 of which cause cancer. I look around the beer garden to see dozens of other people doing the same thing. With every cigarette they smoke, they typically lose eight minutes off their lifespan.
For smokers, those 43 chemicals significantly increase the risk of developing lung cancer. This lethal cocktail reacts with your DNA and causes mutations on the molecular level. Over time, the numbers of these mutations grow, until your cells morph into out-of-control growth machines – cancerous tumours. Cancer is such a deadly disease because bits of these tumours often break away, travel around the body to other organs, and establish new growths.
Statistically, one in two UK citizens born after 1960 will get some form of cancer – that’s three out of my six friends at the pub. Of every diagnosis, one in five will be lung cancer, which is predominantly caused by tobacco smoking. Lung cancer survival rates are equally daunting: for every 100 diagnoses, only 15 patients will survive to five years following diagnosis. This could be improved through earlier detection; if patients are diagnosed in the earlier stages of the disease, their survival rate can be as high as 50 per cent after five years.
My research is about finding a faster and more reliable way to diagnose lung cancer. Unfortunately, it’s not always easy to diagnose lung cancer early enough. The most common symptoms – persistent cough, tiredness and shortness of breath – might seem trivial and are commonly associated with many other lung diseases. Additionally, more serious symptoms don’t present themselves until it is too late. Another problem is that our current diagnosis methods are ‘one-size-fits-all’.
So I am trying to find out what is cancerous and what is healthy with a targeting agent. I use proteins, called antibodies, which are produced by the immune system to help fight off infections. Once made, antibodies are designed to have a single, specific target; they are essentially the ‘homing missiles’ of the body. Nowadays, we can make and select an antibody that will only target lung cancer cells.
Next, I attach the metal palladium to the antibodies. Palladium acts like a light switch, essentially ‘switching on’ the properties of certain chemicals. Finally, I introduce one of these certain chemicals into the lung to be switched on by palladium: a fluorescent molecule, which absorbs light and then spits it back out again as a different colour. And there you have it: a big, glowing sign marking the location of cancerous cells.
What you may not know about the human lung is that it has its own fluorescent glow, which is caused by the same proteins that make the tissue stretchy so that your lungs expand when you inhale. This means that when I use fluorescent molecules to distinguish between healthy and cancerous cells, they need to glow differently from the lung itself so that I can generate some contrast. Think of it like trying to see the stars when the moon is out: the moonlight swamps the light from the stars, obscuring them.
It’s the same with using fluorescent molecules in the lung. My solution for this is to use a series of fluorescent molecules, like a firecracker or a chain of fairy lights. The palladium ‘light switch’ will cause these molecules to glow simultaneously and more brightly than the lung’s own fluorescence. It’s essentially like having 10 stars glowing in the exact same place so that you can see them.
When my research comes to fruition, I hope to provide a new method for earlier diagnosis of lung cancer, which means that treatments will be more effective. So, the five-year survival rate has the potential to increase from 15 to 50 people out of 100. However, what it really means is that my friend Chris has a chance at a longer life and may one day be sitting in that same beer garden boasting about the triumphs of Newcastle Football Club.