JUN and osteosarcoma: In this context, it is interesting to note that c-Jun activity is increased in a variety of cancers, including high-grade osteosarcoma, where it seems critical for disease progression.31, 32 c-Jun is also highly amplified and overexpressed in human liposarcomas, leading to undifferentiated aggressive tumors associated with an early stage of adipocyte differentiation.33 Thus c-Jun amplification may confer an undifferentiated and more aggressive phenotype to an already developing tumor.