Tolfenamic Acid Sensitizes Ewing Sarcoma Family Tumor Cells to Chemotherapy

Ewing sarcoma family tumor (EFT) is the second most prevalent bone and soft tissue tumor observed in children and young adolescents. Patients with metastatic disease have poor outcome with 5-year overall survival rate less than 30%. Current chemotherapeutic options are causing limited progress in the management of EFT. Our aim was to identify novel targets and less toxic agents to improve the efficacy of standard care offered to EFT patients. Specificity protein 1 (Sp1) transcription factor is known to be upregulated in various cancers and is frequently linked to poor prognosis. In this study, Tolfenamic acid, an inhibitor of Sp1 was tested to sensitize EFT cells to commonly used chemotherapeutic agent Vincristine (Vin). The effect of TA or Vin or TA+Vin on cell viability was evaluated by CellTiter-Glo assay and caspase 3/7 activity was measured by Caspase3/7 Glo assay. Western blot analysis was performed to determine the expression of Sp1, survivin, and cleaved-PARP. Apoptotic cell population was measured by Annexin V staining. Results showed a dose and time dependent decrease in cell viability with both agents while the combination of TA+Vin caused a significantly higher response as compared to individual treatments. This inhibition of cell viability was accompanied by the inhibition of Sp1 and survivin expression and an increase in the apoptotic markers i.e. Annexin-V positive cells, caspase 3/7 activity and the levels of c-PARP. Our results suggest that TA+Vin combination treatment provides an effective therapeutic strategy for the treatment of EFT.