Abstract 2791: Hypoxia selectively confers resistance to the survivin-targeting compound YM155 in acute myeloid leukemia and Ewings sarcoma cell lines
Authors: Montoya Justin , Finch Kieran , Simper Jan , Arceci Robert J. , Aleem Eiman A. 
Published: July 2016

Abstract
Background
Hypoxia is characteristic of almost all types of solid tumors and is an important component of the bone marrow microenvironment. It is an adverse prognostic indicator in cancer as it is associated with tumor progression and chemoresistance. Cells may adapt to hypoxia in different ways; including growth arrest, stimulation of angiogenic factors, inhibition of apoptosis, induction of the ER stress program, or modification of the cellular energy metabolism. YM155 inhibits survivin gene expression by suppressing promoter activity and subsequent gene expression. The role of hypoxia and its clinical implications in childhood cancer remain largely unknown. Therefore, studying the drug response of cancer cells within a hypoxic environment is critical for the accurate prediction of patients’ response to therapy.
The aims of the present study were (1) to perform screening of the effects of 5 molecularly targeted compounds on a large panel of pediatric cancer cell lines including acute myeloid leukemia (AML), Ewings sarcoma (ES), osteosarcoma (OS), and neuroblastoma (NB), under normoxia and hypoxia, and (2) to determine the potential mechanisms of drug resistance under hypoxia.
Methods and Results
In the present study the IC50 values were determined for the following targeting agents: linsitinib, picropodophylin (insulin-like growth factor-1 receptor), YM155 (survivin), AZD 8055 (mTOR), dovitinib (FLT3, c-kit, FGF4), and Palbociclib (CDK4/CDK6) in a panel of 15 AML, 4 ES, 2 OS and 2 NB cell lines using Cell Titer Glo assay. The effect of hypoxia was differential. It depended on the cell line and the compound used. However, hypoxia induced universal resistance to YM155 in all cell lines tested. YM155 had significant cytotoxicity in AML cell lines (IC50 between 2.5-1775 nM) in normoxia, however, the IC50 values in hypoxia were in the micromolar range, with an increase of &gt; 100 fold. The effect of hypoxia on YM155 response in ES cell lines was less pronounced with (IC50s between 1-10 nM) in normoxia compared to (IC50 between 6 and 350 nM) in hypoxia. We studied the effect of hypoxia on the cell cycle using propidium iodide and flow cytometry in MV4-11 AML cells. Treatment with YM155 for 24 h in normoxia induced a pronounced decrease in the percentage of cells in S phase and G2/M phase and an increase in the sub-G1 phase. However, no change in cell cycle phases was detected under hypoxia. Ongoing studies are focusing on determining the mechanisms of hypoxia-induced YM155 resistance through studying the expression of proteins regulating hypoxia, cell cycle, and apoptosis using western blot.
Conclusion
These data demonstrate that hypoxia induced different effects in a panel of pediatric cancer cell lines. However, it conferred pronounced resistance to YM155 in AML and ES cell lines. Hypoxia is likely a key factor in programming treatment resistance and, thus, relapse and poor outcomes.
Citation Format: Justin Montoya, Kieran Finch, Jan Simper, Robert J. Arceci, Eiman A. Aleem. Hypoxia selectively confers resistance to the survivin-targeting compound YM155 in acute myeloid leukemia and Ewings sarcoma cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2791.