Characterization of Three Novel H3F3A-mutated Giant Cell Tumor Cell Lines and Targeting of Their Wee1 Pathway

The giant cell tumor of bone (GCTB) is a locally aggressive primary bone tumor that is composed of mononuclear stroma cells, scattered macrophages, and multinucleated osteoclast-like giant cells which cause pathologic osteolysis. The stroma cells represent the neoplastic population of the tumor and are characterized by the H3F3A mutation G34W. This point mutation is regarded as the driver mutation of GCTB. We have established three new stable H3F3A mutated GCTB cell lines: U-GCT1, U-GCT2, and U-GCT3M. MK-1775 is a Weel-kinase inhibitor which has been used for blocking of sarcoma growth. In the cell lines we detected Weel, Cdk1, Cyclin B1, H3K36me3, and Rrm2 as members of the Weel pathway. We analyzed the effect of MK-1775 and gemcitabine, alone and in combination, on the growth of the cell lines. The cell lines showed a significant reduction in cell proliferation when treated with MK-1775 or gemcitabine. The combination of both agents led to a further significant reduction in cell proliferation compared to the single agents. Immunohistochemical analysis of 13 GCTB samples revealed that Weel and downstream-relevant members are present in GCTB tissue samples. Overall, our work offers valuable new tools for GCTB studies and presents a description of novel biomarkers and molecular targeting strategies.