New scientific discovery may enable accurate prediction of cancer spread even before cancer develops
Researchers from Erler Group at the Biotech Research & Innovation Centre (BRIC) in Copenhagen have discovered that the rigidity of a thin membrane structure encompassing cells and lining all vessels regulates how easily cancer cells can breach tissues to spread through the body, and is thus a key determinant of cancer patient survival. The results are published in Nature Materials today. You can find the published article here.
The researchers analysed cells, mouse models, and human patient samples using biochemical, mathematical, and biophysical methods. They identified a protein present in the mesh-like membrane structure (the basement membrane) associated with tumour and vessel softness, and good survival of cancer patients. The researchers tested if removing this protein from the basement membrane would enhance the spread of cancer, which it did, and if supply of this protein would reduce cancer spread, which it did. They proceeded to show that the levels of this protein (netrin-4) already present in basement membrane of organs may determine cancer spread even before cancer develops, in several cancer types.
“These are extremely exciting findings that open up the possibility to predict which organs a person’s cancer most probably spread to before they even have cancer. This information therefore has the potential to guide and improve cancer patient treatment and care.” said Professor Janine Erler, senior researcher on the paper.
In their study, the researchers could show for the first time the impact of basement membrane composition on its mechanical properties thereby affecting cancer cell transmigration over this protein border within the inter-cellular space. They identified the secreted protein netrin-4 to open nodes inside the basement membrane network, which simultaneously softens the basement membrane and increases its mesh (pore) size. This unexpected finding highlights that cancer cell movement is dominantly controlled by the basement membrane stiffness and pore size plays an underpart. Thus, the more netrin-4 inside the basement membrane of the primary tumour or inside blood vessels within organs prone to metastasis, the less metastasis, impacting on patient survival. Moreover, they demonstrate for the first time that the mechanical properties of the basement membrane independent of cancer-related modifications are a pivotal determinant of cancer patient survival.
“We were incredibly excited to find a mechanistic explanation for our observations where the theoretical modelling closely matched our experimental data. We could show that the more netrin-4 molecules present, the softer the basement membrane and the more difficult for a cell to traverse this membrane thereby keeping cells contained in one area. We are currently exploring the therapeutic and diagnostic potential of our findings. Our study is a result of a huge collaboration effort from researchers in Denmark, Sweden, Germany, the UK, and Belgium, spanning many disciplines, which has been key to obtaining the exciting results.” added Dr Raphael Reuten, lead researcher on the study.
Historically, there has been much focus on the stiffness of the extracellular matrix that lies outside of cells and the influence on cancer progression. However, there have not been studies investigating the influence of basement membrane stiffness. Moreover, studying the impact of mechanical properties of the basement membrane on cell invasion and cancer metastasis has not been possible so far. The mechanistic insights into netrin-4 activity inside basement membranes has enabled the researchers to bridge this gap of knowledge and present new opportunities to study basement membrane stiffness in a broad range of biological processes.
This work was funded by the European Research Council, Danish Cancer Society, German Cancer Aid, Novo Nordisk Foundation, Lundbeck Foundation, Danish Research Council, among other international agencies.
New technique to unveil matrix inside tissues and tumours
We have developed a groundbreaking method to reveal the structure of tissues and tumours with unprecedented detail, by completely dissolving away cells and leaving the delicate extracellular matrix intact.
The matrix surrounds the cells in every organ of our bodies, and provides shape and structure to the organ. The matrix has a profound impact on how cells behave, and so controls the progression of diseases such as cancer. Yet the matrix is extremely difficult to study in detail.
Now our team has developed a new technique published in Nature Medicine today that makes closer study of the matrix possible. The technique, which is known as ‘ISDot: in situ decellularization of tissues’ reveals the inner structure of organs and tumours by removing cells but leaving the matrix completely unaltered. The three-dimensional structure of this matrix has never been seen in such detail before. You can find the published article here.
“We have developed a technique to obtain intact organ scaffolds and to image them in incredibly high detail using microscopes. We are the first to image the 3D structures of primary and metastatic tumours as well as healthy organs in this way”, says Professor Erler.
A world of details revealed
Cells which are organised together to form tissues rely on the extracellular matrix as a foundation for attachment, to arrange themselves properly, and to sense how to behave when their environment changes. Sometimes this organisation goes wrong and cells grow into tumours. To destroy a tumour, it is essential to know both its structure and the foundation upon which it is built.
The new method was pioneered by postdoctoral fellow Dr Alejandro Mayorca-Guiliani, who says, “We have isolated the structure that keeps tissues in place and organises the cells inside them. We did this by using existing blood vessels to deliver cell-removing compounds directly to a specific tissue to remove all cells within an organ. Doing this leaves behind an intact scaffold that could be analysed biochemically and microscopically, providing us with the first view of the structure of tumours.”
Imaging expert and co-first author Chris Madsen (now at Lund University, Sweden) says “When you remove the cells, the clarity of what you can see through the microscope is much improved – you can see the fibres of the matrix more clearly and you can look much deeper into the tissue. Using this approach, we have been able to see important differences in matrix organisation when we looked at metastatic tumours in the lung and in the lymph node.”
Matrix Biology and mass spectrometry expert and also co-first author Thomas Cox (now based at the Garvan Institute of Medical Research, Sydney) says “Because we are removing the cells completely, we can use mass spectrometry to identify and catalogue the components of the matrix – in normal tissue and in tumours – in unprecedented detail. What is really exciting is we found that some of the components of the matrix in different secondary tumours metastases are unique to that tissue. That is telling us that remodelling of the matrix in cancer is organ-specific”.
Understanding cancer progression
This research is an advance in the fields of both cancer research and bioengineering: By using the decellularised organs we can learn much more about how tumours and normal organs are built, and what their differences are. This new technique might evenhave an impact on organ regeneration and tissue engineering in the future.
“We are now re-introducing cells into our extracellular matrix scaffolds, bringing them back to life, to study how tumours form and how cancer progresses. This is extremely exciting and offers a unique opportunity to study how cells behave in their native environment,” explains Professor Erler.
The research is supported by the Danish Cancer Society, an ERC Consolidator Award, the Novo Nordisk Foundation, a European Research Council Consolidator Award, the Ragnar Söderberg Foundation Sweden, Cancerfonden Sweden, the Innovation Foundation Denmark, the National Health and Medical Research Council (NHMRC) Australia and the Danish Council for Independent Research.