The Duality of Collagens in Metastases of Solid Tumors.

Metastases are responsible for the majority of cancer-related deaths and remain one of the most complex and therapeutically challenging hallmarks of cancer. The metastatic cascade involves a multistep process by which cancer cells invade local tissue, enter and survive in circulation, extravasate, and ultimately colonize distant organs. Increasingly, the tumor microenvironment (TME), particularly the extracellular matrix (ECM), has emerged as a central regulator of these steps. Far from being a passive scaffold, the ECM actively influences cancer progression through its biochemical signals, structural properties, and dynamic remodeling. Among ECM components, collagens play a particularly pivotal role by mediating tumor cell adhesion, migration, invasion, survival, immune evasion, and therapeutic resistance. This narrative review synthesizes current knowledge of the dual roles of collagen in the metastatic process, with a focus on the cellular and molecular mechanisms. We highlight how altered ECM architecture and signaling contribute to metastatic niche formation and explore the potential of targeting ECM components as a strategy to enhance cancer therapy and improve patient outcomes.