Abstract 976: Metabolic eradication of treatment resistant cancer stem cells in pancreatic tumors: A clonal tracking-based platform for identifying the best personalized treatment
Authors: Corti Denise , Carugo Alessandro , Sahil Seth , Marchesini Matteo , Pettazzoni Piergiorgio , Nezi Luigi , Green Tessa , Marszalek Joseph R , Di Francesco Maria Emilia , Heffernan Timothy P , Draetta Giulio F , Viale Andrea 
Published: August 2015

Abstract
Pancreatic ductal adenocarcinoma (PDAC) continues to have a poor prognosis despite new drugs advancing to the clinic.
We recently characterized a population of cells able to survive the genetic and pharmacologic extinction of oncogenic pathways and demonstrated that the surviving cells (SC) are tumor stem cells (CSC) able to remain in a quiescent state for months before relapsing. In-depth transcriptomics and metabolomics analyses revealed SCs to exhibit different metabolic features compared to the bulk of tumor cells. Specifically, SC relied on mitochondrial respiration (OXPHOS) and displayed impaired glycolytic capacity. In accord with their decreased dependence on glycolysis these SC were highly sensitive to OXPHOS inhibitors, which prevented tumor recurrence.
Notably, preliminary results in patients suggest that SC resistant to conventional chemoradiation also have similar features. We analyzed specimens after neoadjuvant treatment and observed dormant cells positive for CSC markers and characterized by an increased mitochondrial mass. Evaluation of TMA of hundreds of treated tumors revealed that high mitochondrial content is a common feature of SC. Furthermore, functional metabolic characterization of human cells resistant to gemcitabine revealed that SC have a severely impaired glycolytic reserve, closely resembling mouse SC. Based on these findings, we posit that OXPHOS inhibitors may be an effective adjuvant therapy to eradicate resistant cells in patients.
To validate the efficacy of OXPHOS inhibition, we developed a new platform to study tumor evolution in response to treatments based on clonal tracking. Lentivirus-based systems have been extensively used as a tool to investigate the clonal dynamics, but they have been limited by lack of sensitivity and the impossibility of tracking identical clones in different animals. Here, using a new version of the barcoded technology coupled with deep-sequencing, we track hundreds of thousands of clones at the single-cell level. We generated patient-derived xenograft animal cohorts in which tumors were clonal replicas of each other (each tumor is maintained by the same clones of all other tumors), representing a unique tool to evaluate responses to treatments. More importantly, resistant tumor clones generated in vivo can be isolated and fully characterized and compared to pre-treatment clones to identify new mechanisms of resistance.
Our integrated analysis paves the way for new therapeutic strategies for patients to eradicate treatment-resistant CSC by specifically targeting their unique metabolism. In addition, our clonal tracking-based platform monitoring the efficacy of different treatments in eradicating resistant clones represents an unprecedented tool for exploring treatment responses at the single-cell level, which will help guide the development of personalized treatments.
Citation Format: Denise Corti, Alessandro Carugo, Seth Sahil, Matteo Marchesini, Piergiorgio Pettazzoni, Luigi Nezi, Tessa Green, Joseph R Marszalek, Maria Emilia Di Francesco, Timothy P Heffernan, Giulio F Draetta, Andrea Viale. Metabolic eradication of treatment resistant cancer stem cells in pancreatic tumors: A clonal tracking-based platform for identifying the best personalized treatment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 976. doi:10.1158/1538-7445.AM2015-976