This is the first post in my series “Understanding Cancer”. For a complete list of the available posts, please click here.
In 2000, two scientists by the names of Hanahan and Weinberg published an exceptional piece of work entitled “The Hallmarks Of Cancer”. This paper was to become a cornerstone of how we view cancer today and it radically changed how we approach the problem of cancerous cells overall. It is now taught as an essential to undergraduates in medicine and the life sciences throughout the world and it is therefore a great way to understand how scientists think about cancer.
The idea behind it is that cancer is a multi-step disease. Healthy cells are driven in their day-to-day lives by the blueprint laid out by their DNA. DNA is subject to mutation – as a result of exposure to radiation (like UV rays), toxic substances (such as nicotine) or simply randomly. Each mutation is like an ink stain on a spot of a blueprint – it makes that specific portion of the blueprint illegible. As a consequence, a cell that has undergone mutation can no longer perform whatever functions were specified in the part of the blueprint that was “spoilt” by mutation. This example is actually a huge over-simplification as some types of mutation actually make parts of the blueprint more powerful or simply activate them at the wrong time.
Nevertheless, the key idea that Hanahan and Weinberg (and many others!) brought forward was that cells need to accumulate a certain numbers of mutations in different parts of their blueprint in order to become cancerous. In particular, mutations need to fall into six key categories: escaping cell death (apoptosis), driving their own renewal, resisting anti-growth signals, sustaining the growth of new blood vessels (angiogenesis), unblock their replicative potential and invading the rest of the body. These categories are known as the “Hallmarks of Cancer”. During this short series of posts titled “Understanding Cancer” we will be reviewing the basics of each one of these and their importance in modern cancer science.
Image credit: Hanahan and Weinberg, 2000
A decade after the publication of this seminal paper, the authors revisited their list of Hallmarks to include two extra – escaping detection from the immune system and altering the energy balance of cancer cells. They also identified two “enabling characteristics” that have to be true in order for the set of mutations to accumulate correctly – genomic instability (i.e. the unstable state when mutations easily occur and accumulate in cells) and the presence of cancer-promoting inflammation.
This is the first post in the series Understanding Cancer. I am going to get into an in-depth discussion about each and every Hallmark identified by these two seminal publications, giving a bird-eye view of most of the most exciting cancer research that is happening all over the world right now. Go check out all the posts here.