Breast cancer metastases mean a poor prognosis. They often only appear after years and then grow rapidly. Researchers have investigated which mechanism plays a role.
Metastases occur in approximately one in five women with breast cancer. This often only happens years later, when you think the disease has already been conquered. From a medical perspective, the cancer is no longer curable at this stage.
Cancer research has long been interested in why some cancer cells leave their original tumor and continue to grow in other parts of the body. It is assumed that there is a complex molecular, cell biological mechanism behind this. Scientists from the German Cancer Research Center (DKFZ), the Helmholtz Center Munich, ETH Zurich and the Heidelberg Institute for Stem Cell Technology have tried to decipher it.
Breast cancer metastases are daughter tumors whose cells come from the tissue of their original tumor. They have detached themselves from its cell network and migrate to other parts of the body via the blood or lymphatic system. Breast cancer metastases most often spread to the bones. But organs such as skin, liver, brain or lungs can also be affected.
The scientists looked at a special cell mechanism, the so-called epithelial-mesenchymal transition (EMT). This causes the “sedentary” cancer cells to become mobile and can first penetrate the surrounding tissue and finally be transported to distant organs via the blood and lymphatic system.
The cancer cells change their identity: from “epithelial” to “mesenchymal” and vice versa. To explain: Epithelial cells and mesenchymal cells differ significantly from each other in their form and function. A key feature is that epithelial cells are tightly linked to one another, whereas mesenchymal cells do not have any tight cell connections and can therefore more easily detach themselves from the cell structure and penetrate the basement membrane of the epithelial cells.
Both types of cancer cells were present in the metastatic biopsies. However, not all breast cancer cells led to the development of metastases, as subsequent experiments showed. Only those cancer cells that had retained their original epithelial identity were able to form new metastases. In contrast, cancer cell clones with a loss of epithelial features had reduced metastatic potential.
“There are different and sometimes contradictory data about the importance of the EMT mechanism for metastasis formation, which may also differ depending on the type of cancer,” explains Martin Sprick from the Heidelberg research team. “Overall, our results suggest that complete and irreversible EMT surprisingly limits the clonal spread of the cancer cells, while the epithelial identity of the cancer cells is absolutely necessary for the spread of the disease.”
The findings of the study are a first step towards better identifying the mechanism behind metastasis formation. It is completely unclear whether this will eventually lead to therapies for metastatic breast cancer.
Nevertheless, it is important to continue pursuing the approach, says Christina Scheel from the Dermatological University Clinic in Bochum. “The process of metastatic growth is particularly important because cancers are generally most difficult to treat at this stage.”
It is now the task of future research to find out how this study result can be used in the treatment of aggressive, metastatic tumors.
If breast cancer has already spread, the disease is at an advanced stage. Complete healing can then no longer be expected. But there are treatments that can limit tumor growth, alleviate possible symptoms and improve the patient’s quality of life. In some cases, the progression of the disease can be delayed for many years.
Certified breast cancer centers, tumor centers and oncology practices are good places to go for the treatment of metastatic breast cancer. Those affected and their relatives can also find psycho-oncological support here.
Which therapy is suitable depends primarily on which region of the body the metastases occur and how many there are. The biological characteristics of the tumor also play a role. These include, among other things, hormonal influences. The patient’s age and physical condition must also be taken into account in the therapy plan.
It is impossible to predict exactly how the disease will progress, whether there will be stable phases of the disease and what the patient’s life expectancy will be. Nevertheless, there remains a legitimate hope for a good quality of life for as long as possible. According to the Munich Cancer Registry, out of 100 breast cancer patients with metastases, around 26 are still alive after five years and around 13 after ten years.