Abstract 1013: Role of mitochondria and glutamine metabolism in therapy resistance: Combined targeting of estrogen receptor alpha and exportin 1 in endocrine resistant breast cancers

Abstract

Majority of breast cancer specific deaths in women with ERα (+) tumor occur due to metastases that are resistant to endocrine therapy. There is a critical need for novel therapeutic approaches to prevent or delay recurrence of ERα (+) tumors. The objective of this study was to elucidate the role of mitochondrial pathways that are activated in the presence of single therapies and undermine therapy effectiveness in ER (+) breast cancers. In our previous studies, we identified Exportin 1 (XPO1), a nuclear export protein, as an important player in endocrine resistance progression. Selinexor (SXR), an XPO1 antagonist, has been evaluated in multiple later stage clinical trials in patients with relapsed and /or refractory hematological and solid tumor malignancies. Using a combination of transcriptomics, kinase arrays, metabolomics and metabolic flux experiments, we identified glutamine metabolism pathways to be rewired during endocrine resistance. In limited media conditions mimicking nutrient deprived tumor microenvironment, endocrine resistant cells were more dependent on mitochondria for energy production. Their glucose and fatty acid dependency decreased in the presence of SXR and cells were more dependent on glutamine. The effect of glutamine was dependent on conversion of the glutamine to glutamate and mitochondrial complex 1 activity. In order to examine metabolites that might result in the observed phenotype we performed GC/MS whole metabolite profiling and identified aminoacid metabolism pathways to be upregulated when cells were treated with SXR. We demonstrated that combined targeting of XPO1 and ERα rewires metabolic pathways and shuts down both glycolytic and mitochondrial pathways that would eventually lead to autophagy. Remodeling metabolic pathways to regenerate new vulnerabilities in endocrine-resistant breast tumors is novel, and given the need for better strategies for improving therapy response of relapsed ERα (+) tumors, our findings show great promise for uncovering the role ERα-XPO1 crosstalk plays in reducing cancer recurrences. Citation Format: Eylem Kulkoyluoglu Cotul, Brandi Patrice Smith, Hua Chang, Yosef Landesman, Kevin Duong, Zeynep Madak Erdogan. Role of mitochondria and glutamine metabolism in therapy resistance: Combined targeting of estrogen receptor alpha and exportin 1 in endocrine resistant breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1013.