Abstract 1901: Detection of EML4-ALK fusion gene expression in circulating tumor cells (CTCs) captured from non-small cell lung cancer (NSCLC) patients

Abstract

Abstract Background & Aims: Detection of unique genomic profile such as EML4-ALK rearrangement in CTCs can be directly implicated to the course of treatment in patients with NSCLC. The aims of this study were to determine 1) if CTC could reliably be identified using microfabricated porous filter platform in advanced NSCLC; 2) feasibility of RT-PCR as a useful tool in detection of EML4-ALK rearrangement from CTCs. Method: Lung cancer cell lines with EML4-ALK rearrangement (NCI-H3122, NCI-H2228) were spiked into 5 ml of blood and were passed through the CTC platform. Twenty-five patients (19 FISH-proven ALK positive and 6 ALK negative in tissue) were prospectively enrolled in this study. Peripheral blood samples were drawn from the study patients and processed through CTC platform. Captured cells were characterized by IF staining; DAPI (nucleated cell marker), cancer cells by EpCAM and WBCs by CD45. RNA was extracted from the captured CTCs and RT-PCR was used to detect EML4-ALK fusion gene. Results: EpCAM expression was evaluated qualitatively and quantitatively in NSCLC cell lines by FACS analysis. Surprisingly, 100% of NSCLC cells expressed EpCAM, most at very high levels (165,000 ∼ 215,274 EpCAM antigens/cell). EpCAM was uniformly expressed throughout the population. The capture yield of ALK positive lung cancer cells were varied in spiking experiments (41-59%). There were 25 stage IV NSCLC patients whose clinical situations were variable in the aspect of previous cytotoxic chemotherapies and ALK-targeted tyrosine kinase inhibitors. CTCs were detected in 41% and EML4-ALK expressions were detected by RT-PCR in 58% of initially EML4-ALK positive NSCLC patients. Sequencing of PCR products identified the expression of EML4-ALK fusion gene. The sensitivity and the specificity of RT-PCR in detection of EML4-ALK fusion gene expression from the CTCs of NSCLCs were 58% and 100%, respectively. Conclusion We have proved the existence of EML4-ALK positive CTCs using RT-PCR after the enrichment of CTCs from the peripheral blood of NSCLC patients. Being able to reliably capture and molecularly characterize CTC may not only allow us to characterize a patient's cancer from a simple blood draw but investigation of genomic profile from CTCs may give us insights into the genetics and biology of tumor cell dissemination with further investigation. Citation Format: Joo Kyung Park, Ji Kon Ryu, Se-Hoon Lee, Eun-Hye Kim, Byung-Chul Kim. Detection of EML4-ALK fusion gene expression in circulating tumor cells (CTCs) captured from non-small cell lung cancer (NSCLC) patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1901. doi:10.1158/1538-7445.AM2014-1901