Targeted Liquid Biopsy Using Irradiation to Facilitate the Release of Cell-Free DNA from a Spatially Aimed Tumor Tissue

Abstract

We investigated the feasibility of using an anatomically localized, target-enriched liquid biopsy (TLB) in mouse models of lung cancer. Materials and MethodsAfter irradiating xenograft mouse with human lung-cancer cell lines, H1299 (NRAS protooncogene, GTPase (NRAS) Q61K) and HCC827 (EGFR E746-750del), ctDNA levels were monitored with quantitative PCR (qPCR) on human long interspersed nuclear element-1 (LINE-1) and cell line-specific mutations. We checked dose-dependency at 6, 12, or 18 Gy to each tumor-bearing mouse leg using 6-MV photon beams. We also analyzed ctDNA of lung cancer patients by LiquidSCAN, a targeted deep sequencing to validated the clinical performances of TLB method. ResultsIrradiation could enhance the detection sensitivity of NRAS Q61K in the plasma sample of H1299-xenograft mouse to 4.5-fold. While cell-free DNA (cfDNA) level was not changed at 6 Gy, ctDNA level was increased upon irradiation. Using double-xenograft mouse with H1299 and HCC827, ctDNA PCR analysis with local irradiation in each region could specify mutation type matched to transplanted cell types, proposing an anatomically localized, target-enriched liquid biopsy. Furthermore, when we performed targeted deep sequencing of cfDNA to monitor ctDNA level in 11 patients with lung cancer who underwent radiotherapy, the average ctDNA level was increased within a week after the start of radiotherapy. ConclusionTLB using irradiation could temporarily amplify ctDNA release in xenograft mouse and lung cancer patients, which enables us to develop theragnostic method for cancer patients with accurate ctDNA detection.

A nanoparticle priming agent reduces cellular uptake of cell-free DNA and enhances the sensitivity of liquid biopsies

“…However, drawing large volumes of blood may not always be possible or desirable, particularly in frail or ill patients, and plasmapheresis carries associated risks and requires expensive instrumentation. Alternatively, methods to sample more proximal to the tumor ( 21 ) or to increase the shedding of ctDNA have also been investigated ( 22 , 23 ). Yet, both approaches require a priori knowledge of the tumor site and more invasive procedures, making them suboptimal in the context of cancer screening or monitoring of presumed disease-free patients.…”

Priming agents transiently reduce the clearance of cell-free DNA to improve liquid biopsies

“…Large volumes, however, are impractical in frail or ill patients, and plasmapheresis carries major risks and requires expensive instrumentation. Alternatively, methods to sample more proximally to the tumor ( 22 ) or to increase tumor DNA shedding have been proposed ( 23 , 24 ). These methods require prior knowledge of tumor location, are limited to specific primary tumors, and often require specialized, expensive, and invasive procedures.…”