Abstract 3153: Transcriptome differences in tyrosine kinase inhibitor-resistant clones of EGFR-mutant lung cancer using a new microfluidic assay for concurrent single-cell RNA and targeted DNA sequencing
Authors: Kong Say Li , Li Huipeng , Ruff Dave , Tai Joyce An Yi , Courtois Elise T. , Poh Huay Mei , Lau Dawn Pingxi , Liew Audrey Ann , Tan Gek San , Lim Tony Kiat Hon , Tan Daniel Shao Weng , Prabhakar Shyam , Hillmer Axel M. 
Published: July 2017

Abstract
Resistance to therapy is one of the major causes of cancer-associated death. While a number of mechanisms for the development of resistance to epidermal growth factor receptor, EGFR-targeting drugs in lung cancer have been described, most genomic and transcriptomic studies have focused on analyzing bulk samples that can only provide an average measurement over the entire mixture of cell populations of a tumor. With this approach, it is difficult to resolve cell-to-cell variability of drug resistance within a heterogeneous tumor. In order to accurately describe and eventually delineate the underlying causes of cancer progression, it requires the analysis of single cells on both, the transcriptomic and the genomic level. Only the co-detection of mutations and expression features in individual cells allows to define the connection between the two. We therefore aimed to establish a new methodology for concurrent evaluation of transcriptomic and genomic features within the same single cell on the Fluidigm C1 system. We applied this protocol to an EGFR-mutant lung cancer cell line, PC9, that has developed resistance to tyrosine kinase inhibitor, TKI treatment after prolonged exposure to sublethal doses of Gefitinib. We amplified cDNA and selected genomic EGFR regions of the TKI responsive and resistant PC9 clones from a total of ≈300 single cells. We used our in-house single cell’s analysis pipeline for parallel processing of transcriptome and variants detection. In addition, a novel algorithm, NODES was used to normalize the single cell RNAseq data and detect differentially expressed genes. The differential transcriptome and emergence of the EGFR T790M resistance mutation in relation to the TKI response were evaluated. We observed up-regulation of receptor tyrosine kinase AXL in the resistant cell lines. This observation is in agreement with previous findings that AXL is the key player that promotes TKI resistance in lung cancer. In addition, we found up-regulation of other genes that have not been previously described. Cumulatively, this method allows us to dissect the underpinnings of the TKI resistance mechanism and enables us to identify biomarker for specific cellular features that are connected with resistance and thereby with lung cancer patient’s response to TKI treatment.
Citation Format: Say Li Kong, Huipeng Li, Dave Ruff, Joyce An Yi Tai, Elise T. Courtois, Huay Mei Poh, Dawn Pingxi Lau, Audrey Ann Liew, Gek San Tan, Tony Kiat Hon Lim, Daniel Shao Weng Tan, Shyam Prabhakar, Axel M. Hillmer. Transcriptome differences in tyrosine kinase inhibitor-resistant clones of EGFR-mutant lung cancer using a new microfluidic assay for concurrent single-cell RNA and targeted DNA sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3153. doi:10.1158/1538-7445.AM2017-3153