Passenger Deletion Of Eno1 As A Collateral Lethality Target In Cancer

Large scale genomic characterization efforts such as TCGA have painted an unprecedentedly detailed picture of the genetic alterations that underlie tumorigenesis. Yet, the majority of genetic alterations are passenger rather than driver events and are considered unactionable. We have previously proposed that passenger or collateral deletions could serve as pharmacologically targetable vulnerabilities Collateral Lethality, in case passenger genes are homozygously deleted and member of a paralogous gene family carrying out an essential housekeeping function. We have presented proof-of-principal, whereby passenger deletion of the glycolytic gene Enolase 1 (ENO1) as part of the 1p36-tumor suppressor locus, renders glioma cells harboring such deletions highly sensitive to ablation of its redundant paralogue, ENO2. While our original analysis identified ENO1-homozygous deletions in Glioblastoma (GBM), recent bioinformatics analyzes, backed by immunohistochemistry, show that ENO1-homozygous deletions also occur in Hepatocellular Carcinoma and Cholangiocarcinoma. In GBM, multisector analysis of primary and recurrent tumors, indicate that ENO1 deletion is an early event which is homogenously distributed through the primary tumor and persist during recurrence. To pharmacologically exploit ENO1-deletion, we have pursued two approaches. First, we have synthesized cell-permeable prodrug derivatives of the natural Enolase inhibitor SF2312. The lead compound, POMHEX, shows potent killing of ENO1-deleted glioma cells in the low nM range while ENO1-restored isogenic or normal cells can tolerate μM doses. POMHEX has a short half-life yet can eradicate intracranial xenografted ENO1-deleted tumors, provided extensive breakdown of the blood-brain barrier. Our second approach to targeting ENO1-deletion consisted of chemical biology screening of drug libraries for the ability to kill ENO1-deleted but not isogenic rescued cells. We find that ENO1-deleted cells show a dramatic sensitization to inhibitors of the mitochondrial electron transport chain. These include tool compounds such as rotenone as well as compounds not previously associated with mitochondria, such as Mubritinib and an experimental anti-neoplastic agent previously described as a HIF1-inhibitor, now known to inhibit mitochondrial Complex I. The latter agent shows potent activity against ENO1-deleted intracranial xenografts. The likely cause for this sensitivity is the inability of ENO1-deleted cells to compensatory upregulate glycolysis in response mitochondrial inhibition, the typical response of ENO1-intact glioma cells and normal cells. Together, these data indicate that passenger deletion of ENO1 is an encouraging drug-target and provide support for collateral lethality as a viable therapeutic strategy, which, given the large number of passenger deletions in the cancer genome, may be broadly applicable. Citation Format: Yu-Hsi Lin, Nikunj Satani, Naima Hammoudi, Joe Marszalek, Yuting Sun, Marina Protopopova, Maria E. Di Francesco, Barbara Czako, Alan Wang, Ronald A. DePinho, Florian L. Muller. Passenger deletion of ENO1 as a collateral lethality target in cancer. [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 3837.