CD44 and cancer: The controversial discussions on the relevance of CD44 gene products in cancer biology in general and the limited knowledge on their biological functions in OS and metastasis in particular prompted us to perform the here reported CD44 silencing study in an intratibial OS xenograft model in SCID mice that makes use of the human highly metastatic 143-B cell line and reproduces the human disease with metastasis to the lung.