How do targeted therapies for cancer work?

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?

Targeted cancer therapies are a group of treatments that aim to disrupt the specific cell processes that help cancer cells grow, divide, and spread. These treatments are only possible because discovery science keeps uncovering new information about the genetic and molecular make up of cancer, and how cancer starts and grows. Thanks to this research, more and more targeted therapies are becoming available.

Targeted therapies all work differently, but they also all have one thing in common: each therapy 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 these changes are beneficial to the cancer cell- they could help the cell divide more quickly, or ignore signals to stop growing.

But these changes can also be a potential ‘weak spot’ for the cell 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 in the cancer cell, that are not present in a healthy cell.

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.

The four main types of targeted cancer therapies:

PARP inhibitors

PARP inhibitors are quite a new type of targeted therapy. They work by stopping cancer cells from carrying out essential DNA repairs.

All cells gather DNA damage as they divide and grow. However, cancer cells often accumulate more DNA damage than healthy cells, and they can also find it harder to repair that damage too. This is a recognised ‘weak spot’ for cancer, and researchers are working hard to find ways to exploit this important vulnerability.

One way 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 10 years, but research funded by our supporters for many years before that helped to bring the first PARP inhibitor, called olaparib, to patients.

Monoclonal antibodies

Monoclonal antibodies are special proteins that are engineered in a lab. These proteins can recognise and stick to other proteins, including proteins 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 monoclonal antibodies work by stopping the cancer cell from receiving the signals it needs to divide and grow. They bind to and block special receptor proteins on the cancer cell surface that are used to receive these signals, and prevent important messages from getting through.
Other types of monoclonal antibody work by stopping the cancer cell from hiding from our immune system. One way they might do this is by sticking to the cancer cell so that our immune system can easily spot it and attack. Because these monoclonal antibodies are essentially helping our immune system to find and target cancer cells, they are also classed as a type of
Some types of monoclonal antibody 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 is currently using your donations to try and develop a new type of monoclonal antibody. Dr Perry and her team are designing the antibody to block growth hormone receptors on the cancer cell, and stop the cancer cell from receiving signals to grow. The researchers believe that using this type of antibody in combination with radiotherapy could help to make radiotherapy 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:

Thanks to our Curestarters, we are able to support many new cancer discoveries every year, and just one of these discoveries might lead to the next big targeted therapy breakthrough.

Making PARP inhibitors possible

Early support from Curestarters way back in the 1990s helped do some of the vital discovery work needed to kick-start the very beginning of the first PARP inhibitor. Thanks to your support, 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.

Additional funding from Curestarters and then helped Professor Jackson and others begin to carry out early lab testing of a new drug, that we now call olaparib. Data produced from this work ultimately helped researchers move olaparib towards first tests in patients. In 2014, olaparib was approved for use, and it has already been used to treat at least 75,000 people worldwide.

PARP inhibitors work particularly well against cancers with mutations in the BRCA genes. They are currently mainly used to treat ovarian cancer, fallopian tube cancer, and peritoneal cancer, and have also recently been approved for some prostate and breast cancers. And this has already changed the lives of people like Fiona, who received olaparib treatment for her advanced ovarian cancer, giving her more hope for the future.

The 'undruggable' target

Dr Laura Soucek and her team in Spain are working to target what has been described as an ‘undruggable’ protein in cancer. Myc proteins drive cell growth, and are overproduced in 70% of all cancers. Researchers have long thought that blocking Myc activity in cancer cells could be a highly effective way to treat cancer. But many also thought that because Myc is so important for all cells, anything that targets Myc may also have catastrophic side-effects.

Nevertheless, Dr Laura Soucek tried anyway, and has spent years developing a new drug, called Omomyc, that is able to stop Myc proteins from functioning. The team found that Omomyc works well. It works so well in the lab in fact, that it has just entered clinical trials for first testing in patients.

This is incredible progress, and it was Curestarter funding that helped Dr Soucek to get to this point, allowing the team to gather enough early data to convince other funders that Omomyc has real potential, and give their support to patient trials.

A new therapy from an old idea

In Italy, 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.

Drugs that block DNMT enzymes have already been tried, but they are not as effective as expected, and they can also be damaging to healthy cells.

Now Dr Esposito and her team have developed a new type of drug that they think can target and neutralise specific DNMT enzymes. Thanks to Curestarter funding, the team are investigating how well these drugs might work in cancer, and are using nanomedicine technology to develop a safer way to deliver them to cancer cells.

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 the scientists who are making this happen. We cannot fund vital research like this without the support of Curestarters like you. Together we can save lives by discovering the next cure for cancer. Will you join us today?