What does "cancer research" mean?
- Cancer research is studying the many different features and processes that define a cancer.
- The goal of cancer research is to understand how cancer cells differ from healthy cells. Knowing this allows us to exploit these differences to kill cancer cells without harming the healthy cells around them.
- In order to do this, we need to find what molecules cause cancer cells to behave differently and then find out what leads to the changes in these cancer-causing molecules in the first place.
- If we can do that, these molecules become potential new therapeutic targets.
- Making a drug that binds these molecules and stops them from misbehaving could restore normal behaviour to the cancer cells.
- Making a drug that binds only the misbehaving form of the molecules could also allow us to deliver the drug only to the cancer cells since they are the only cells that will have the misbehaving molecules.
What are the steps of cancer research?
What has cancer research already taught us about cancer?
- Cancers are clusters of cells that grow out of control, stop responding to the body's signals to stop dividing, and gain the ability to spread throughout the body to form metastases.
- Cancer cells accumulate mutations in their DNA that cause the molecules encoded by this DNA to misbehave and encourage the cells to keep dividing.
- Each tumour contains many mutations. This means that targeting just one of these with a drug is almost never sufficient to treat a cancer.
- Tumours contain a mixture of different cell types that promote each others' growth.
- This mixture includes different types of tumour cells as well as other structural cells (ie. blood vessels) that are commandeered by the cancer cells to help the tumour grow.
- The different types of tumour cells all arise from the same tissue but contain a different group of mutations and so behave differently from each other. For example, a lung cancer tumour will contain several different types of lung cancer cells.
- It's necessary for cancer treatments to target all cells in a tumour in order to be effective at controlling a tumour.
- The best way to do this is to treat patients with different combinations of therapies, such as chemotherapy and radiotherapy, because each treatment will kill only some of the cell types in the tumour.
- Each patient's cancer is unique.
- This is because every cancer contains a different set of specific mutations and different group of misbehaving molecules.
- Even though the specific mutations are different, the end result of these mutations in all cancers is abnormal and out of control cell growth.
- Some mutations occur commonly in cancers that grow in a specific location. For example, many breast cancers share mutations in a gene called EGFR.
- These shared mutations are called "dominant" and usually occur in genes that promote cell growth in the specific tissue location.
- But the end result that these mutations have on any one cancer depends on the many other mutations that that cancer also has.
- This is because every molecule in the body cooperates with other molecules to get their job done.
- These dominant mutations make very good drug targets because a single drug can be used to treat many patients. But the effect of the same drug on each patient will differ a bit depending on what other mutations their cancer has.
- This is because every cancer contains a different set of specific mutations and different group of misbehaving molecules.
- Each cancer changes over time.
- All cells in the body, including cancer cells, continuously respond to signals from their environment.
- If a new mutation or molecular disruption occurs that helps a cancer cell divide or survive better than its neighbouring cells, the cancer cells with this change will overgrow the other cells and spread throughout the tumour.
- In this way, a cancer evolves to be optimally suited to live in its environment.
- One of the strongest signals a cancer can receive comes from therapies that are given to treat the cancers.
- Chemotherapy and radiotherapy are strong environmental signals that are designed to kill as many cells as possible in the tumours.
- Any cells in the tumours that have molecular changes allowing them to survive the drug will eventually be the only ones left surviving and will take over the tumour.
- This is likely a major cause of the resistance that patients develop during treatment and can explain why a tumour may seem to go away and then come back very rapidly.
- Our best strategy to combat this is to use combinations of therapies that make it less likely any one cancer cell can adapt to the multiple drug signals in their environment.
What don't we know about cancer?
- There is a lot we still don't know.
- We understand a lot about what has to go wrong in a cancer cell to make it misbehave, but we don't yet understand what controls these abnormal processes.
- This is like knowing that your car will turn on when you put the key in the ignition but not knowing what happens in the engine to allow the car to come to life.
- Some of the key things we need to learn are:
- How do cancer control how and when mutated DNA is corrected (or not) in the cell.
- How do cancers avoid signals that stop healthy cells from dividing.
- How do cancers control the other cells in their environment to promote the tumour growth.
- How do cancers control when they begin to spread throughout the body and how do they manage to survive this process.
- How does the overall physiology of the patient change a cancer's growth.
- Identifying the molecules that control abnormal behaviour in cancer cells is critical for showing us where we need to intervene to regain control over the cancer.
- New medicines that target these molecules could then be developed that would allow doctors to regain control over the cancer with their treatments.