Abstract 2766: Amplification-associated upregulation of genes involved in oxidative phosphorylation for disseminated prostate cancer cells
Authors: Lin Chun-Lin , Xi Tan , Hung Chia-Nung , Osmulski Pawel A. , Chou Chih-Wei , Chen Meizhen , Wang Chiou-Miin , Mitsuya Kohzoh , Kirma Nameer , Gaczynska Maria E. , Chen Chun-Liang , Huang Tim H.-M. 
Published: August 2019

Abstract
Purpose: Little is known about adaptive selection of tumor cells transiting from in situ proliferation to distant colonization through blood circulation. This study used genomic, transcriptomic, and biophysical analyses at single-cell levels to explore biological and physical properties of circulating tumor cells (CTCs) undergoing hemodynamic stress. The aims are trying to understand how CTCs strive to survive in the bloodstream and to develop strategies for therapeutic intervention.
Experimental Design: We compared genomic profiles of CTCs in blood and primary tumor cells shed in urine of prostate cancer patients to identify amplified regions preferentially retained in CTCs. Single-cell RNA-seq was used to confirm amplification-associated overexpression of genes in CTCs.
Results: Among 261 recurrently amplified genomic regions in the analysis, 70 were found predominantly shown in CTCs relative to primary tumor cells. In line with the results at the genomic level, the transcriptomic data of CTCs demonstrate a great amount of cells showing high expression levels in the oxidative phosphorylation (OXPHOS) pathway compared to other hallmark gene sets. The finding suggests that tumor cells with these pre-existing genomic alterations were adaptively selected for transcription reprogramming during blood circulation. Specifically, amplified genes associated with OXPHOS were exploited by CTCs for alternative fuels. As to the upstream of this transcription event, we found the expression of MEN1, encoding menin known to form a transcription factor complex with the mixed-lineage leukemia protein (MLL) in prostate cancer cells, was positively correlated with 11 of the 14 OXPHOS loci in the Cancer Genomic Atlas prostate cancer cohort. In vitro assay showed that MEN1 knockdown by shRNA resulted in attenuation of both mRNA and protein expression of OXPHOS loci in PC-3 cells. Taken together pre-existing amplification of OXPHOS loci can be used as a transcription apparatus by menin for metabolic reprogramming of tumor cells in response to harsh microenvironments in the bloodstream.
Conclusions: Single-cell profiling identified signaling pathways that are crucial for CTCs to survive in the bloodstream. The finding suggests that a metabolic shift from Warburg to OXPHOS metabolism can be associated with a hybrid mesenchymal-epithelial phenotype of CTCs. Moreover, the study demonstrates the feasibility of routinely conducting single-cell analysis of exfoliated tumor cells for minimally invasive monitoring of disease progression and treatment response in prostate cancer patients
Citation Format: Chun-Lin Lin, Tan Xi, Chia-Nung Hung, Pawel A. Osmulski, Chih-Wei Chou, Meizhen Chen, Chiou-Miin Wang, Kohzoh Mitsuya, Nameer Kirma, Maria E. Gaczynska, Chun-Liang Chen, Tim H.-M. Huang. Amplification-associated upregulation of genes involved in oxidative phosphorylation for disseminated prostate cancer cells [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 2766.