Lay-pitched articles

Searching for new drugs to prevent recurrence of breast cancer

It takes a long and winding road for a newly discovered drug to reach a patient.  Pharmaceutical companies have traditionally taken on this challenging task; however, it has become increasingly important for other public and private ventures to contribute to the discovery and development of new drugs. Here we discuss our research within two such ventures: the EMPathy Breast Cancer Network¹ and the Cancer Therapeutics Cooperative Research Centre², both aiming to translate innovative cancer research into potential drugs.

Discovering new therapies to prevent and treat metastatic breast is absolutely necessary.

In contrast to early detection of breast cancer, which has the best effect on treatment outcome among all cancers, advanced or metastatic disease has far less optimistic treatment response. Recently discovered targeted therapies targeting specific cancer drivers, like the anti-oestrogen therapies, have the capacity to prevent many, but not all types of breast cancers from spreading in the body. Therefore the need for new therapies that could prevent the onset of metastatic breast cancer and effectively treat the disease remains crucial.

There is accumulating evidence that the spread of cancer cells to other parts of the body, leading to secondary tumours, is facilitated by a dynamic cellular process called “Epithelial Mesenchymal Plasticity” (EMP). It is also believed that cells undergoing EMP become resilient to conventional therapies. The core work of the EMPathy Breast Cancer Network thus aims to investigate how EMP promotes breast cancer metastasis. Taking a step forward, we use two approaches to identify new drugs that can potentially target and disrupt EMP in breast cancer.

• The fast-track approach relies on the idea that some existing drugs, including those that have previously failed in clinical testing of other diseases, could have an effect on EMP that has been overlooked. We have assembled a library of 3,500 known drugs, which we have tested with EMP models of cultured breast cancer cells. Any promising drugs acting against EMP are currently being tested further before they can be considered for clinical trials.
• The second approach is to develop new EMP-targeting drugs. When an EMP target is identified, we aim to develop tests that can help us sieve through hundreds of thousands of chemical compounds to find molecules that can specifically prevent the activity of that “target”. The active molecules or “hits” from each screen will then be further tested with EMP models of cultured cancer cells and in pre-clinical models. Once their activity against EMP is confirmed, they will be chemically modified for improved performance, and be repeatedly tested before being taken into clinical trials.

As you can see, extensive time, effort and funds are required to develop new cancer therapies. By exploring current theories and developing new ideas into the next generation of drugs, we thrive to benefit cancer patients with healthier, longer and better lives.

Dormancy: The late onset of secondary tumours in breast cancer

We believe that it may be possible to prevent the development of secondary breast cancer by keeping tumour cells that have spread from the original tumour in a dormant state.
Breast cancer starts with the uncontrolled growth of breast tissue. When a tumour develops in the breast it is known as a ‘primary’ tumour.  The majority of women diagnosed with breast cancer that is confined to the breast will respond well to early treatment and will not relapse. In a small number of women diagnosed with breast cancer, their tumours will already have spread from the breast to other areas in the body. If breast cancer has spread to other areas, such as the lungs or bones, it is called ‘secondary’ breast cancer. This is also known as ‘metastatic’ or ‘advanced’ breast cancer and a cure is yet to be found.

Tumour cells that have spread to other areas in the body can lay in a sleep-like state called dormancy.
Breast cancer can return up to 20 years after the first diagnosis.
Breast cancer tumour cells may be shed into the bloodstream and circulate.  Many of these cells, known as circulating tumour cells, can subsequently lodge in tissues such as bone or lung. When this occurs, the
cells are called disseminated tumour cells. Once in these tissues, they can lie in a sleep-like state called dormancy and remain in this state for many years after an initial diagnosis. Then something triggers these cells to ‘wake up’ and start growing into a secondary breast cancer tumour. Breast cancer can return up to 20 years after the first diagnosis. This possibility causes much uncertainty for patients and their families.

As part of the National Breast Cancer Foundation (NBCF) funded EMPathy Breast Cancer Network¹ our researchers are working to understand more about:

• the genes that control dormancy and what causes cells to ‘wake up’
• how cancer cells can remain alive and undetected for long periods of time
• the link between circulating tumour cells, disseminated tumour cells,  and dormancy

We propose that it may be possible to prevent the development of secondary breast cancer by keeping disseminated tumour cells in a dormant state. Alternatively we may be able to develop a therapy that can kill dormant tumour cells.

Behind the Scenes:
Identifying and Isolating Tumour Cells in the Blood and Bone Marrow

Tumour cells that are found in the blood and bone marrow in some breast cancer patients are believed to be the seeds by which breast cancers spread and settle elsewhere in the body. They consist of:

• circulating tumour cells (CTCs), found in the blood
• disseminated tumour cells (DTCs), found in the bone marrow

These cells have been identified in many women whose breast cancer has spread to other parts of the body.  A tumour found in the breast is called a ‘primary’ tumour, whereas breast cancer that has spread to
other areas is known as ‘metastatic’, ‘advanced’ or ‘secondary’ breast cancer.

These cells have the potential to become important clinical tools in the fight against breast cancer.

In order for tumour cells to leave the primary tumour to become CTCs or DTCs, the cells have to undergo some changes. As breast cancers mostly arise in the component of the breast known as the epithelium, the
primary tumour cells are initially epithelial in cell type. Epithelial cells tend to be inactive or stationary cells. However, in order for these tumour cells to escape from the primary tumour and move out and survive in the blood, they need to change to a more mobile, resilient type of cell known as mesenchymal. The term epithelial mesenchymal plasticity (EMP) refers to the ability of cells such as tumour cells to change between epithelial and mesenchymal cell types, allowing them to alter their behaviour. EMP is not unique to tumour cells; it was first described in the development and growth of embryos, and is also involved in wound healing.

The underlying mission of the EMPathy Breast Cancer Network¹ is to study these EMP changes in order to develop diagnostic tools and treatments specifically targeting CTCs and DTCs. The EMP changes of tumour cells is believed to be vital for the survival of the separated tumour cells, allowing them to move around the body, and invade and
settle at a distant site where they may become dormant or develop into a secondary breast cancer tumour (metastasis). Studying EMP involves analysing the genes of these cells, as EMP changes of these cells are a
result of certain EMP genes being switched off or on.

In order for the EMPathy team to study EMP in CTCs and DTCs they have been collecting blood and bone marrow from breast cancer patients when the surgeon removed their breast tumour, and when further blood is taken at other times throughout the patient’s treatment. The presence of persisting tumour cells after primary tumour removal and treatment is linked to an increased chance of the cancer coming back, and shorter
survival times in patients. It is therefore important to develop tools to identify these resilient tumour cells and then to find drugs that specifically target them.

An outline of the behind the scene processes involved in the EMPathy study is as follows:

• A human research ethics committee has assessed the EMPathy network study and protocols in order to ensure all patients involved are treated ethically.
• Methods have been developed and optimised to isolate and purify tumour cells from blood and bone marrow. Genetic tools for analysing genes potentially involved in EMP have been optimised on cultured cancer cells.
• Over 50 women with early and advanced breast cancer have been enrolled to help with our studies.
• Samples are collected from women who consent to participate after the study purpose and process has been explained. Blood is collected  using a needle in the arm  – just like a normal
  blood test, while bone marrow is collected in a minor surgical
  procedure while the patient is anaesthetised.
• The CTCs from blood or DTCs from bone marrow samples are then isolated using magnetic beads coated with antibodies that recognise and bind to
  proteins on the surface of the tumour cells. These proteins are not found on other cells normally found in the blood. A magnet is used to collect the bound cells and the other blood or bone marrow cells are washed away. It is technically challenging to completely eliminate the contaminating ‘background’ cells to obtain a ‘pure’ CTC/DTC population, because the small number of cancer cells will be in amongst billions of
  blood cells.
• Once the tumour cells have been isolated specific EMP genes are taken out of the cell, and their activity is measured.

The EMPathy network aims to gain understanding of how EMP changes allow tumour cells to survive cancer treatments, remain in the body for long periods of time, and help the spread of cancer in patients. Analysis of these cells has the potential to become important clinical tools in the fight against breast cancer, as they are considered instrumental in causing secondary breast cancer.

MicroRNAs and Secondary Breast Cancer

Metastasis – migration of breast cancer cells to other parts of the body

Most adult cancers or tumours arise from the abnormal growth of cells that perform the functions of our organs – we call these ‘epithelial’ cells, and they give rise to ‘carcinomas’. Normally ‘epithelial’ cells are
strongly attached to one another, however during cancer progression these cells can change and separate from this line-up and gain mobility via blood or lymphatic circulations. One way that they can gain this
mobility in by changing from an ‘epithelial’ state to a ‘mesenchymal’ state. When they arrive at a suitable secondary site these cells can transform back to the epithelial state and begin growing as a new tumour.

This migration of cancer cells to other areas of the body and subsequent formation of a new tumour is called ‘metastasis’. Metastatic breast cancer, also known as secondary or advanced breast cancer, is the leading cause of breast cancer death. The switching of cells back and forth between the stationary ‘epithelial’ state and the invasive ‘mesenchymal’ state is called ‘epithelial-mesenchymal plasticity’ (EMP). These events are preceded by alterations in activity of genes, microRNAs and proteins, which are the building blocks and regulatory units of cells. MicroRNAs are a new type of regulator that influences how our genes are converted into proteins. A single microRNA can affect the performance of one or many genes at the same time, making them very powerful regulators. So far only a few of the microRNA dominated genes involved in EMP are known, making it a promising area for further study.

MicroRNA’s (gene regulators) may be important in controlling breast cancer metastasis.

As part of the National Breast Cancer Foundation (NBCF) funded EMPathy Breast Cancer Network1 we have:

• Identified new microRNA-regulated genes acting in breast cancer EMP,
  using a method involving ‘Next-generation DNA sequencing’.
• Measured genes and microRNAs in breast cancer cells when in an
  epithelial state compared to a mesenchymal state.
• Correlated the gene and microRNA changes with EMP-like alterations
  using rigorous computational and statistical analyses.

We are working to identify new microRNAs and genes, involved in EMP and metastasis of breast cancer, that could potentially be targets for new drugs.

Some interesting changes in genes and microRNAs were identified and we are now testing them more comprehensively. Those changes that show a stronger association with EMP will be clinically tested with breast cancer patients.