Chondrosarcomas are notorious for their resistance to conventional chemo- and radiotherapy, indicating there are no curative treatment possibilities for patients with inoperable or metastatic disease. We therefore explored the existence of molecular targets for systemic treatment of chondrosarcoma using kinome profiling.

Peptide array was performed for 4 chondrosarcoma cell lines and 9 primary chondrosarcoma cultures. Acitivity of kinases was verified using immunoblot and active Src- and PDGFR signaling were further explored using imatinib and dasatinib on chondrosarcoma cell lines and primary cultures.

The AKT1/GSK3B pathway was clearly active in chondrosarcoma. In addition, the PDGFR pathway and the Src kinase family were active. PDGFR and Src kinases can be inhibited by imatinib and dasatinib, respectively. While imatinib did not show any effect on chondrosarcoma cell cultures, dasatinib showed a decrease in cell viability at nanomolar concentrations in 3 out of 5 chondrosarcoma cultures. Whereas inhibition of phosphorylated Src (Y419) was found both in responsive and non-responsive cells, caspase-3 related apoptosis was found only in cell line GIST882, suggesting that the mechanism of decreased cell viability in chondrosarcoma by dasatinib is caspase-3 independent.

In conclusion, using kinome profiling we found the Src pathway to be active in chondrosarcoma. Moreover, in the chondrosarcoma cell lines and primary cultures we showed that the inhibitor of the Src pathway, dasatinib, may provide a potential therapeutic benefit for chondrosarcoma patients which are not eligible for surgery.

In both Enchondromatosis (EC) and Multiple Osteochondromas (MO), multiple benign cartilaginous tumours occur, which have a severely increased risk of malignant progression. Preventing new tumor formation and malignant progression would benefit the prognosis of these patients. A protective effect of selective Cox-2 inhibitor celecoxib, has been suggested against development and growth of colorectal cancer in familial syndromes. At last year’s EMSOS meeting we reported on expression of Cox-2 in 37% (central) – 46% (peripheral) of conventional chondrosarcomas. mRNA levels of EC related tumours were slightly higher than the solitary tumours. Celecoxib treatment of the chondrosarcoma cell lines resulted in a 3 fold decrease of PGE2 levels already at 5 μM. A significant decrease in proliferation was found at 10 μM in OUMS27 and at 25 μM in SW1353 and CH2879 compared to DMSO controls.

For the present study we assessed the (prophylactic) effect of celecoxib on chondrosarcoma growth in vivo using a xenograft model of immunoincompetent nude mice which were injected with cell line CH2879 subcutaneously. Tumour volume was measured during 8 weeks. Celecoxib serum levels were determined by HPLC. Expression of proliferation marker Ki-67 and Cox-2 was assessed by IHC.

Our in vivo results also showed a beneficial effect of high dose prophylactic celecoxib treatment. Tumour volumes were negatively correlated with celecoxib serum levels (r2=0.152). However, at the end of pubertal growth of the mice, a catch-up tumour growth was observed, resulting in the absence of differences in tumour volume between control and treatment groups. Accordingly, proliferation marker Ki67 was higher expressed in the treated groups at sacrifice.

This suggests that there is no role for celecoxib in the treatment of adult chondrosarcoma patients. Celecoxib treatment of younger patients, especially to prevent formation of new tumours in EC and OC patients, might be beneficial, however more research is necessary.