Cell Component and Function of Tumor Microenvironment in Thyroid Cancer.

Thyroid cancer is the most common cancer in the endocrine system. Most thyroid cancers have good prognosis, but some of them are resistant to treatment or show aggressive behavior. Like other tumors, thyroid cancers harbor tumor microenvironment (TME) composed of cancer associated fibroblasts (CAF) and immune cells. Autoimmune lymphocytic thyroiditis can occur in the thyroid, and it may be associated with cancer development. TME is involved in tumor progression through various mechanisms: (1) CAF is involved in tumor progression through cell proliferation and extracellular matrix (ECM) remodeling; and (2) immune cells are involved in tumor progression through cell proliferation, angiogenesis, epithelial mesenchymal transformation (EMT), and immune suppression. These events are activated by various cytokines, chemokines, and metabolites secreted from cells that comprise TME. This review is focused on how CAF and immune cells, two important cell components of thyroid cancer TME, are involved in tumor progression, and will explore their potential as therapeutic targets.