The hallmarks of CAFs in cancer invasion.

The ability of cancer cells to move out of the primary tumor and disseminate through the circulation to form metastases is one of the main contributors to poor patient outcome. The tumor microenvironment provides a niche that supports cancer cell invasion and proliferation. Carcinoma-associated fibroblasts (CAFs) are a highly enriched cell population in the tumor microenvironment that plays an important role in cancer invasion. However, it remains unclear whether CAFs directly stimulate cancer cell invasion or they remodel the extracellular matrix to make it more permissive for invasion. Here we discuss paracrine communication between cancer cells and CAFs that promotes tumor invasion but also stimulates CAFs to remodel the matrix increasing cancer dissemination.