Abstract 3965: Modulating glutathione s-transferase M4 activity for the treatment of Ewing sarcoma
Authors: Zhuo Rupeng , Kosak Kenneth M. , Sankar Savita , Wiles Elizabeth T. , Sun Yin , Zhang Jianxing , Prestwich Glenn D. , Shami Paul J. , Lessnick Stephen L. , Cairo Mitchell S. , Luo Wen 
Published: May 2015

Abstract
Ewing sarcoma is a malignant pediatric bone and soft tissue tumor. The prognosis for Ewing sarcoma remains dismal despite of intensive treatments including surgery, radiation, and chemotherapy. Moreover, these unspecific treatments often have severe side effects. We previously reported that Glutathione S-transferase M4 (GSTM4) is a potential specific treatment target for Ewing sarcoma. GSTM4 is required for oncogenic transformation and confers chemotherapeutic drug resistance in Ewing sarcoma cells; high GSTM4 level in primary tumor is correlated with poor patient outcome. Here we further evaluate the efficacy of modulating GSTM4 activity in treating Ewing sarcoma using patient-derived cells and mouse xenograft models. RNA-seq analysis for RNA levels of all GSTs in A673 Ewing sarcoma cells as well as online database searching for GSTM4 RNA level in tumor samples of various sarcomas demonstrate that GSTM4 is specifically highly expressed in Ewing sarcoma. By MTT and soft agar assays, we find that NBDHEX, a GSTM4 inhibitory compound, inhibits cellular proliferation and oncogenic transformation of Ewing sarcoma cells. Furthermore, NBDHEX has a synergistic effect in cytotoxicity with chemotherapeutic drug etoposide. Conversely, a GSTM4-activated anti-cancer agent, JS-K, significantly decreases Ewing sarcoma cell viability (p&lt;0.05). We find that JS-K works through GSTM4 because knockdown of GSTM4 by shRNA in Ewing sarcoma cells significantly decreases their sensitivity to JS-K (p&lt;0.05). Moreover, JS-K significantly decreases Ewing sarcoma xenograft tumor growth in immunodeficient mice (Mantel-Cox test p=0.0002). Next we examine the underlying mechanism of GSTM4 mediated drug resistance and find that GSTM4 interacts with Apoptosis Signal-regulating Kinase 1 (ASK1) and inhibits ASK1 activation of c-Jun N-terminal Kinase (JNK) mediated apoptosis upon etoposide treatment. Taken together, these data provide further evidence that GSTM4 is a novel therapeutic target for Ewing sarcoma. GSTM4 targeted inhibition by inhibitors or knockdown by RNA interference combined with standard chemotherapeutic regimens are potential treatments more specific and effective for Ewing sarcoma. GSTM4 pro-drugs are promising for treatment of patients with high GSTM4 expression tumors. Our data also suggest that agents intervening of GSTM4/ASK interaction may increase drug sensitivity of Ewing sarcoma cells and tumors and therefore be of therapeutic values.
Citation Format: Rupeng Zhuo, Kenneth M. Kosak, Savita Sankar, Elizabeth T. Wiles, Yin Sun, Jianxing Zhang, Glenn D. Prestwich, Paul J. Shami, Stephen L. Lessnick, Mitchell S. Cairo, Wen Luo. Modulating glutathione s-transferase M4 activity for the treatment of Ewing sarcoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3965. doi:10.1158/1538-7445.AM2014-3965