CD166 is a member of the Ig superfamily and is expressed on activated T-cells, B cells and other cells including thymic epithelial cells, fibroblasts, keratinocytes and neurons. CD6 has been identified as a receptor for CD166.
The expression of CD166 is up-regulated in low-grade prostate tumors and down-regulated in high-grade tumors; may play role in progression of prostate cancer.