Targeting
receptor tyrosine kinase (RTK) degradation may be an interesting approach to reduce RTK cell signaling in
cancer cells. Here we show that increasing
E3 ubiquitin ligase casitas B-lineage
lymphoma (c-Cbl) expression using lentiviral
infection decreased
osteosarcoma cell replication and survival and reduced cell migration and invasion in murine and human
osteosarcoma cells. Conversely, c-Cbl inhibition using
short hairpin RNA (
shRNA) increased
osteosarcoma cell growth and survival, as well as invasion and migration, indicating that c-Cbl plays a critical role as a bone
tumor suppressor. Importantly, the anticancer effect of increasing c-Cbl expression in
osteosarcoma cells was related mainly to the downregulation of
epidermal growth factor receptor (EGFR) and
platelet-derived growth factor receptor alpha (PDGFRα). In a murine bone
tumor model, increasing c-Cbl expression also reduced RTK expression, resulting in decreased
tumor cell proliferation and survival and reduced
tumor growth. Interestingly, increasing c-Cbl also markedly reduced lung
metastasis in mice. Tissue microarray analysis revealed that low
c-Cbl protein expression is associated with elevated EGFR and PDGFRα
protein levels in human
osteosarcoma with poor outcome. This study shows that increasing c-Cbl expression reduces
osteosarcoma cell growth, survival, and
metastasis in part through downregulation of RTKs, which supports the potential therapeutic interest of targeting c-Cbl in malignant
bone diseases involving increased RTK.