GSE132762
Characterization of Ewing sarcoma resistance to the EWS-FLI1 inhibitor YK-4-279
Ewing sarcoma (ES) is the second most common pediatric malignancy of the bones and soft tissue, but few advances in therapeutic options have been made over the past several decades. A characteristic feature of ES that and an attractive therapeutic targets is the EWS-FLI1 fusion protein. A small molecule inhibitor of EWS-FLI1, YK-4-279 was as a targeted therapy option for Ewing sarcoma patients. A YK-4-279 analog, TK216, is currently in clinical trial. With any targeted therapy, there is always the risk that tumors will become resistant and stop responding to treatment. Here, we investigated resistance mechanisms to YK-4-279 (YK) by developing ES cell lines specifically resistant to YK. We found that expression of the cell surface protein CD99 was elevated in YK-resistant cells. Increased CD99 expression occurs within five days of YK treatment in vivo. When CD99 expression is reduced by shRNA, resistant cells regain sensitivity to YK but reducing CD99 expression in non-resistant cells does not affect sensitivity. Little is known about CD99 function in the context of Ewing sarcoma, but the data presented here indicates the function of CD99 is altered upon acquisition of YK resistance, and that CD99 serves a critical function in developed resistance to YK-4-279. RNA sequencing analysis yielded candidate genes that may also be involved in the YK resistance mechanism. We identified a potential modulator of CD99 function, ANO1, a member of the ANO family and a participant in membrane-bound ion channel activity. CD99 has previously been linked with membrane-associated ion channels. A functional association between the two proteins remains to be investigated. Overall design: Three samples each of A4573, TC-71, A4573-R, and TC-71-R