While this is rather technical, just looking at the image above will tell you most of what you need to know. This image shows how we've improved our ability to use electron microscope imaging of molecules over time (with protein β-galactosidase used above as an example), from the blobby outline on the left to almost being able to image actual atoms on the right. Determining the 3 dimensional structure of proteins is literally the key to understanding how they function. Knowing a protein's shape is a critical part of the process by which we can custom design molecules that will interact with them to change cellular processes and hence cure diseases including cancer:
On a somewhat related matter, Folding@home has been using the unused computing capacity of home computers for 15 years now, working out how proteins fold. Folding is the critical process by which proteins reach their final three-dimensional structure which determines how they function. Several diseases are caused by misfolding of proteins and examining the causes of protein misfolding should help with the development of better drugs for these diseases as well as some cancers. While the technology involved is rather hard to understand, that's not necessary for you to join the project, which you can simply do by downloading some software and running it on your computer.
Note the section on cancer and in particular the research into the mutations of p53, a tumour suppressor protein, which is behind more than half of all cancers. p53 may be familiar to you as mutations in p53 (17p del) are a very unfavourable prognostic marker in CLL:
More Folding@home references: