This is the essay I submitted to the Max Perutz Writing Award 2016.
Look at yourself in the nearest mirror and, if you aren’t too squeamish, visualise the inside of your body. It’s obvious that not all your cells are the same. We are made of many different tissues that perform different tasks: skin cells protect us from the environment, white blood cells defend us against infections, nerve cells allow us to move and think. Cancer – the uncontrolled growth of cells – can arise from virtually any type of tissue. We hear about new treatments for skin cancers, about raising money for childhood leukaemias, about inoperable brain tumours. We know that there are different types of cancer.
But an individual tumour in a tissue is also complex. Researchers realised decades ago that, like our healthy bodies, tumours aren’t simply lumps of identical cells; that within each tumour there are different cell types. For instance, some tumour cells divide indefinitely to keep the cancer alive, others invade into surrounding tissue and spread to other sites of the body, while yet others stimulate blood vessels to grow. Some cancer cells even combine several of these properties.
In our laboratory we study the pancreas, an organ of the digestive system, which aids digestion and controls metabolism throughout the body by secreting hormones such as insulin. In particular, we investigate variations among cell types in the most common kind of pancreatic cancer called pancreatic ductal adenocarcinoma (PDAC for short). PDACs are among the most deadly cancers with only about three per cent of patients diagnosed with PDAC in the UK surviving for longer than five years. One of the reasons for this gruelling statistic is that PDACs are often diagnosed late, when the cancer cells have already spread to and wreaked havoc in other internal organs. Previously, several labs, including ours, noticed that some PDAC cells are more aggressive than others, more capable of re-growing new tumours from scratch. Now, we aim to understand what makes the more aggressive PDAC cells different from the rest of the cancer cells and how they contribute to the deadliness of this cancer. With that knowledge in hand, the broader aim will be to find anti-cancer drugs to target and kill the most dangerous cells that lie at the heart of PDAC.
A previous PhD student in our lab discovered that the more aggressive PDAC cells make and display large amounts of a certain protein – let’s call it protein X – on their cell surfaces. We say that the more aggressive cells are “marked” by protein X. This realisation was my gateway into finding out exactly how these two cell types, the more and less aggressive cells, differ.
First, I wanted to know whether protein X not only marks the more aggressive cells but whether it is directly responsible for making those cells more dangerous. Therefore I experimentally reduced or elevated the levels of protein X in PDAC cells we grow in the lab. Then I assessed whether the PDAC cells grew more or fewer, larger or smaller “organoids”, miniature replicas of pancreatic tumours. Astonishingly, the cancer cells actually grew less well when I removed most of protein X, or they divided and proliferated much more when they had more of protein X. This is a good indication that, in future, drugs might be delivered directly to protein X to eliminate the aggressive cells or convert them into tamer cells.
In the meantime, I am on the lookout for other characteristics that might distinguish between the more and less aggressive cells. From one of my experiments I have data hinting that the two cell types might in fact have different physical properties. However, until I’ve repeated these experiments I can’t be certain that this difference in appearance contributes to the more aggressive cells’ behaviour. But it is thinkable, for example, that the more aggressive cells can attach to other cells or blood vessels more easily, aiding their movement to the lungs or liver. These secondary tumours, also known as metastases, are the tumours that PDAC patients usually die from. Next, I need to determine whether there is a direct connection between protein X and the variations among the physical properties of the PDAC cells.
We really want to pin down the differences between the more and less aggressive cells so that hopefully researchers and pharmaceutical companies will be able to design and develop more effective drugs to tackle PDAC. In a few years, once we know more precisely what protein X is doing in the more aggressive cells, our findings might matter a great deal to patients. For the moment I am simply trying to find out more about how PDAC cells work and I know that can sound theoretical. However, I am certain that knowing why and how some cancer cells, clearly, are more equal than others will help patients in the future.