Roles and subtypes of cancer-associated fibroblasts (CAFs) in thyroid cancer

Thyroid cancer (TC) is one of the most common tumors of the endocrine system around the world. Most thyroid cancer patients have a favorable prognosis, but a minority develop into treatment resistance, resulting in a very poor prognosis. In addition to the tumor cell component, TC is characterized by a reticula and dynamic tumor microenvironment (TME), in which tumor cells and stromal cells interact with each other in an intricate network of interactions. Cancer-associated fibroblasts (CAFs), one of the most abundant stromal cells in TME of thyroid cancer, actively participate in various aspects of tumorigenesis including immunomodulation, extracellular matrix (ECM) remolding, metastasis. With the advent of sing-cell sequencing, an increasing number of CAF subtypes in TME of thyroid cancer have been identified, and their tumor-promoting roles are becoming progressively clearer. To explicate the potential of CAFs as therapeutic targets for TC, this review will discuss the origin of CAFs, their heterogeneity, plasticity, crosstalk and role in tumorigenesis of TC.