Targeted cancer therapies work in a very different way to most other cancer treatments. But what actually are targeted cancer therapies, and how exactly do they work? More importantly, how is our research helping to make targeted therapy a reality for thousands of patients?
What are targeted therapies for cancer?
Targeted cancer therapies are treatments that aim to disrupt the specific cell processes that help cancer cells grow, divide, and spread. These treatments are only possible because discovery research keeps uncovering new information about the genetic and molecular make up of cancer, and how it starts and grows. Thanks to international cancer research, more and more targeted therapies are becoming available.
Targeted therapies all work differently, but they also all have one thing in common: each is designed to kill or slow the growth of cancer cells, while sparing healthy cells. Cancer cells develop unique changes as they grow and divide, some of which are beneficial to the cancer cell - like helping it divide more quickly.
But these changes can also be a potential weak spot too. The cancer may start to rely heavily on a certain type of protein, for example, that healthy cells do not need so much. Or the changes might lead to the production of abnormal proteins not present in healthy cells.
How do targeted therapies for cancer work?
Targeted therapies are designed to work by exploiting these differences between cancer cells and healthy cells. They often target the molecules, proteins, and chemical signals that cancer cells have come to rely on, and that healthy cells do not need so much.
Sometimes cancer cells can learn to overcome a targeted therapy - they develop ‘resistance’ to the treatment. So to maximise effectiveness, targeted therapies are sometimes given alongside other cancer treatments. These might include chemotherapy, radiotherapy, surgery, immunotherapy, or other targeted therapies.
How is targeted therapy different from chemotherapy?
Chemotherapy and targeted therapies are both types of cancer treatment but they work in different ways. Chemotherapy works by targeting rapidly dividing cells which include cancer cells but also other healthy cells such as hair cells which is why hair loss is a common side effect. Targeted treatments more specifically act on cancer cells, mostly leaving healthy cells alone.
When is targeted therapy recommended?
Targeted therapies are not yet suitable for all cancer types, or all patients. If you or a loved one is needing treatment for cancer your oncologist will be able to advise which treatment is most appropriate for you. This will depend on the cancer type and the stage of the cancer. Sometimes targeted therapy is used alongside other treatments to have the best chance of curing the cancer.
There are four main types of targeted cancer therapy:
PARP inhibitors
PARP inhibitors are quite a new type of targeted therapy that work by stopping cancer cells from carrying out essential DNA repairs. All cells gather DNA damage as they divide and grow but cancer cells often accumulate more than healthy cells, and they can find it harder to repair that damage too.
This is a recognised weak spot for cancer, one way to exploit this important vulnerability is to target a group of proteins that are heavily involved in DNA repair, called PARP proteins. Cancer cells can become very reliant on PARP proteins, and so are especially vulnerable to drugs that are designed to block these proteins from working (called PARP inhibitors).
When PARP protein activity is blocked, cancer cells find it very hard to repair damaged DNA, and become more likely to die. PARP inhibitors have only been available to patients for the last ten years, but our research helped to bring the first PARP inhibitor, called olaparib, to patients.
Monoclonal antibodies
Monoclonal antibodies are special proteins that are engineered in a lab, that can recognise and stick to other proteins, including those that coat cancer cells . Monoclonal antibodies work in many different ways, but they all aim to stop the cancer cell from growing and surviving.
Some work by stopping the cancer cell from receiving the signals it needs to divide and grow, by binding to and blocking special receptor proteins on the cancer cell surface. Other types work by stopping the cancer cell from hiding from our immune system. Some even behave like tiny delivery vans, carrying active drug molecules directly to the cancer cell.
Worldwide Cancer Research scientist Dr Jo Perry in New Zealand used your donations to explore a new type of monoclonal antibody to block growth hormone receptors on cancer cells, and stop them from receiving signals to grow. The researchers believe that using this type of antibody in combination with radiotherapy could help to make it work better, and reduce the development of treatment resistance for some types of cancer.
Antiangiogenic therapies
Antiangiogenic therapies block the proteins and signals that cancer cells use to grow blood vessels (angiogenesis). All tumours need a good blood supply as they grow, and killing off the blood vessels that feed a tumour can be one way to slow the speed of its growth, and reduce the chance of it spreading.
Some types of monoclonal antibody can work as antiangiogenic therapies. Bevacizumab, which is used to treat various cancers, is an example of an antiangiogenic monoclonal antibody. It works by blocking VEGF, a molecule that is important for cancer blood vessel growth.
Cancer growth inhibitors
Cancer growth inhibitors are a broad group of targeted therapies which all work to stop cancer cells receiving and acting on growth signals. These signals are usually delivered in the form of specialised molecules, and some cancer growth inhibitors work by stopping these molecules from activating special receptors on the surface of the cancer cell.
Other types of growth inhibitors work inside the cell, targeting proteins which are involved in cancer cell division and growth. Various types of drugs and monoclonal antibodies can act as cancer growth inhibitors.
BRAF inhibitors and MEK inhibitors, which are sometimes used to treat some forms of melanoma, are both cancer growth inhibitors. They work to block BRAF and MEK proteins in the cancer cell. Both of these proteins are part of a network of molecules that cause cancer growth, and that sometimes become overactive in cancer cells as a result of DNA changes.
Our research impact:
Professor Sir Steve Jackson
Thanks to early support from Curestarters way back in the 1990s, Professor Sir Steve Jackson was able to study the processes involved in repairing damaged DNA in cancer cells, and investigate ‘faults’ in the process that could potentially be used as a new way to target cancer cells. This kick-started the very first PARP inhibitor, olaparib, which has since been used to treat over 140,000 people worldwide.
Dr Carla Lucia Esposito
Thanks to Curestarter funding, Dr Carla Lucia Esposito and her team are working to improve a type of targeted therapy that aims to block DNMT enzymes - a group of proteins that can cause cancer-driving DNA changes in cells. They have developed a new drug that they think can target and neutralise specific DNMT enzymes and are investigating how well these drugs might work in cancer, using nanomedicine technology to develop a safer way to deliver them to cancer cells.
Dr Laura Soucek
With support from our Curestarters, Dr Laura Soucek has spent years developing a new drug, Omomyc, that is able to stop a protein called Myc from functioning. Myc, which drives cell growth, and is overproduced in 70% of cancers, has long been thought to be 'undruggable'. In fact, Omomyc has been found to work so well in the lab that it has now entered clinical trials for testing in patients.
What are the side effects of targeted therapy?
The side effects of targeted therapy for cancer vary since all targeted therapies work differently. Side effects of PARP inhibitors include digestive system issues, fatigue, dizziness and impact on blood pressure or blood cell count. Sometimes the dosage of targeted therapies can be altered to help manage side effects. If you have any questions about side effects of your own treatment please talk to your doctor.
What could the future hold for targeted therapies?
Targeted therapies are still a relatively new form of treatment, but it is already clear that their importance as a cancer therapy will continue to grow, and increasing numbers of patients will benefit every year.
One way that targeted therapies could help more people in the future is through the concept of ‘personalised medicine’.
This works on the idea that cancers can carry very distinctive molecular characteristics- even between people with the same ‘type’ of cancer.
In fact, research suggests that each person’s cancer may have some individual characteristics - a unique pattern of genetic and molecular codes. As research begins to break those codes, then cancer treatment will likely become increasingly more tailored for each specific cancer.
But cancer cells can also learn to fight back. Unfortunately they may eventually find a way to ‘work around’ the targeted therapy. When this happens, the cancer cell develops resistance and the treatment will become less effective.
This is why targeted therapies are usually given alongside other treatments. Doing this can help to prolong the effectiveness of targeted therapy, and delay the development of treatment resistance.
So as well as investigating brand-new targeted therapy approaches, researchers are also working hard to find ways to prevent resistance from developing, and prolong the effectiveness of targeted therapies.
But it is not just scientists who are making this happen. As a cancer research charity, we can fund more vital research like this - but not without the support of Curestarters like you.
Your targeted therapy FAQs:
What is targeted therapy for cancer?
There are lots of different types of targeted therapies but they are all drugs that find and attack cancer cells. They target particular changes in cancer cells that make them different to healthy cells, and which are helping the cancer cells to grow out of control.
What cancers are treated with targeted therapies?
Can targeted therapies be used with other treatments?
Yes, targeted therapies are often combined with other cancer treatments. Combination therapies sometimes add up to more than a sum of their parts, giving the best possible outcome for patients. Research shows that giving breast cancer patients the PARP inhibitor olaparib after each chemotherapy dose could be the best way to help patients with particular mutations.
Can targeted therapy cure cancer completely?
Yes in some cases targeted therapies can cure the cancer – destroying it so it doesn’t come back. In other cases it can help to shrink or stabilise a cancer
Can targeted therapy be used for advanced-stage cancers?
Yes targeted therapies can be used for advanced-stage cancers. Curestarter Fiona was diagnosed with advanced ovarian cancer and olaparib has helped her reach a stage where most of the time she can put cancer to the back of her mind.
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