Abstract 7501: Gene expression profiling of rare cells captured from liquid biopsy using the genesis cell isolation system
Authors: Perike Srikanth , Olcott Angelica , Jiang Cissy , Kumar Nish , Knapp Nathan , Placek Jennifer , Cox Candice , Kang Yoon-Tae , Lingelbach Linda , Dreskin Elizabeth 
Published: March 2024

Abstract
Background: Targeting rare cell types such as circulating tumor cells (CTCs), considered to be metastatic precursors in cancer progression, may provide long-term clinical benefits by enhancing patient outcomes. The study of CTCs comes with technical challenges due to their heterogeneity and low cell numbers, leading to difficulties in genomic characterization. This study aims to overcome these technical challenges by developing a comprehensive gene expression profiling workflow using qPCR and RNA sequencing (RNA-Seq) on rare cells enriched with Genesis System with Celselect SlidesTM.
Methods: To mimic CTCs in blood, we created a rare cell model sample by spiking A549 non-small cell lung cancer cells at concentrations of 50, 100, 500 and 1000 cells/ml in whole blood from healthy donors. The Genesis System, which can capture rare cells of 8µm-30µm, isolated 83.73% of spiked A549 cells in whole blood. Using the same blood samples without A549 spiked in, we enriched cells using the Genesis and it was used as a baseline for gene expression controls. High quality RNA was extracted from each of the enriched samples and used for both qPCR and RNA-Seq to detect the gene expression signature of the non-small cell lung cancer cells.
Results: Our analyses revealed significant differential expression of cancer-related genes (p &lt; 0.05) in all A549-spiked samples when compared to the blood-only controls. Notably, in the 50 cells/ml dilution, RNA-Seq analysis identified over 3,000 differentially expressed genes, encompassing protein-coding genes, long non-coding RNAs, and small non-coding RNAs. Among these, 759 genes were consistently present across all enriched samples, suggesting a common expression pattern. To investigate the potential utility of these genes as non-small cell lung cancer biomarkers, we constructed a custom qPCR array comprising 38 of these genes and pre-amplified their targets using 50pg of RNA from the enriched cell samples. Notably, six genes from this panel (MET, TOP2A, NF1, SPP1, GAPDH, and ANXA5) exhibited significant differential expression (+/- 4-fold, p&lt;0.05) in the enriched samples. MET and TOP2A, in particular, are well-known biomarkers for non-small cell lung cancer.
Conclusion: Our liquid biopsy workflow demonstrates the recovery of high-quality RNA from enriched rare cells, including CTCs. It enables comprehensive profiling of the tumor transcriptome, encompassing RNAs of various sizes, including miRNAs. Our approach has the potential to facilitate the identification of patient-specific biomarkers, enabling swift monitoring using preamplification and qPCR in advancement of targeted oncology therapy and research.
Citation Format: Srikanth Perike, Angelica Olcott, Cissy Jiang, Nish Kumar, Nathan Knapp, Jennifer Placek, Candice Cox, Yoon-Tae Kang, Linda Lingelbach, Elizabeth Dreskin. Gene expression profiling of rare cells captured from liquid biopsy using the genesis cell isolation system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7501.