Editorial: Proteoglycans in the tumor microenvironment

Proteoglycans (PGs) are a family of heavily glycosylated proteins consisting of a core protein covalently attached to glycosaminoglycans (GAGs) and present in diverse environments, such as cell membrane surface, extracellular matrix, and intracellular granules. Extracellular proteoglycans play crucial roles in promoting cell signaling and migration by interaction with growth factor and/or their receptors, intracellular enzymes, extracellular ligands, matrix components, inflammatory cytokines, and structural proteins. Besides regulating the normal behavior and turnover of tissues, proteoglycans can also encourage tumor-microenvironment interactions via the same dysregulated pathways and facilitating metastasis, thus becoming important markers in cancer progression. Proteoglycans play crucial roles in regulating tumor cell growth, proliferation, adhesion, metastasis, and angiogenesis. These functions are widely mediated through interaction between their GAGs chains and several bioactive proteins such as growth factors, morphogens, adhesion molecules, chemokines, and cytokines. The main goal of this Research Topic will be to provide a better understanding of the functional role of proteoglycans in all the aspects of carcinogenesis. In particular, the topics can be focused in, but not restricted to, to some aspects still debated such as the presence of proteoglycans in extracellular vesicle shared between cancer and normal tissue; the correlation between hormones and proteoglycans metabolism; the roles of PGs in cell cycle; changes in GAG composition and their roles in tumor development; epigenetics events that can lead to PGs alterations.