Extracellular matrix proteins in metastases to the liver - Composition, function and potential applications.

The rising evidence of the tumor microenvironment (TME) and its role in cancer have made this an area of increased research efforts. The focus is both on the primary tumor but also on the metastatic setting. The TME though, does not only consist of the non-malignant cells of a tumor, but also of the acellular compartment: The Extracellular Matrix (ECM). The liver is a common organ for metastasis of many cancers and for some of these cancers' liver surgery is a standard treatment with long-term cure, whereas for other cancers not considered meaningful. Blood supply and anatomical reasons plays one part for the establishment of liver metastasis. It is however a well-known fact that the "soil" of a metastatic organ is of utter importance in the process of metastasis. The "soil" consists of the TME where the ECM is a critical and active part. This review focuses what is known about the normal ECM of the human liver, what is known about ECM proteins in human liver metastasis, challenges of studying the ECM in liver metastases and lastly, potential applications of this field of knowledge.