Targeting Sp1 in Ewing Sarcoma: A multi-approach method for the utilization of Mithramycin




Sankpal, Umesh
Basha, Riyaz


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Purpose: Ewing Sarcoma (ES) is a bone and soft tissue cancer affecting young adults and children. ES mostly occurs in the bones or soft tissue of the arms, legs, and pelvis. Localized ES presents with 5-year survival rate of 70%, but metastatic 5-year survival rate is between 15% and 30%. Our laboratory is interested in combination treatments using less toxic agents to induce sensitization to chemotherapy in ES. The anti-cancer activity of an antineoplastic antibiotic, Mithramycin, against ES cells has been shown. Mithramycin inhibits Specificity protein 1 (Sp1) a marker associated with aggressive cancer cell growth and resistance to chemo/radiation therapies. However, its mechanistic effects on survivin, an anti-apoptotic protein associated with poor prognoses in multiple cancers, are continuing to be elucidated in ES. This studies purpose is to evaluate the effectiveness of Mithramycin and various combinations with other chemotherapeutics, Etoposide and Vincristine, to inhibit ES cell growth and effect various cancer related proteins. Methods: Anti-proliferative activity of Mithramycin and/or Vincristine and Etoposide against ES cell lines, TC205 and CHLA10, was evaluated using CellTiterGlo kit. Dose curves were plotted and IC50 values were determined by Sigma-Plot software. The expression of Sp1 and survivin was determined by Western blot analysis. Cell lines were obtained from Children's Oncology Group (COG). Results: Mithramycin significantly decreased ES cell line viability and showed the ability to reduce the expression of Sp1 and offer differing effects on survivin expression, indicative of anti-apoptotic mechanisms being implemented in the ES cell lines. IC50 values of both chemotherapeutics and Mithramycin were decreased by nearly 50% when used in combination and this effect was mirrored in Sp1 expression. Conclusions: Mithramycin may effectively sensitize certain ES cells and improve the response of chemotherapy while lowering necessary effective dosages. Studies to understand the mechanisms of action of Mithramycin on Sp1 and survivin are underway.


Research Appreciation Day Award Winner - 2022 School of Biomedical Sciences, Microbiology, Immunology, & Genetics - 1st Place