Cell-Free DNA Variant Sequencing Using Plasma and AR-V7 Testing of Circulating Tumor Cells in Prostate Cancer Patients

Verena Lieb,Amer Abdulrahman,Katrin Weigelt,Arndt Hartmann,Helge Taubert,Robert Stöhr,Juan Guzman,Laura Bellut,Michael Gombert,Sven Wach,Bernd Wullich,Peter J Goebell,Siegfried Hauch

doi:10.3390/cells10113223

Abstract

Prostate cancer (PCa) is the second most common malignant cancer and is a major cause of morbidity and mortality among men worldwide. There is still an urgent need for biomarkers applicable for diagnosis, prognosis, therapy prediction, or therapy monitoring in PCa. Liquid biopsies, including cell-free DNA (cfDNA) and circulating tumor cells (CTCs), are a valuable source for studying such biomarkers and are minimally invasive. In our study, we investigated the cfDNA of 34 progressive PCa patients, via targeted sequencing, for sequence variants and for the occurrence of CTCs, with a focus on androgen receptor splice variant 7 (AR-V7)-positive CTCs. The cfDNA content was associated with overall survival (OS; p = 0.014), disease-specific survival (DSS; p = 0.004), and time to treatment change (TTC; p = 0.001). Moreover, when considering all sequence variants grouped by their functional impact and allele frequency, a significant association with TTC (p = 0.017) was observed. When investigating only pathogenic or likely pathogenic gene variants, variants of the BRCA1 gene (p = 0.029) and the AR ligand-binding domain (p = 0.050) were associated with a shorter TTC. Likewise, the presence of CTCs was associated with a shorter TTC (p = 0.031). The presence of AR-V7-positive CTCs was associated with TTC (p < 0.001) in Kaplan–Meier analysis. Interestingly, all patients with AR-V7-positive CTCs also carried TP53 point mutations. Altogether, analysis of cfDNA and CTCs can provide complementary information that may support temporal and targeted treatment decisions and may elucidate the optimal choice within the variety of therapy options for advanced PCa patients.

Highlights

Prostate cancer (PCa) is a major cause of disease and mortality among men worldwide each year, and 1.4 million men are diagnosed with PCa
We studied a group of PCa patients with progressive disease in different pretreatment and treatment stages
We performed targeted cell-free DNA (cfDNA) sequencing for sequence variant identification and androgen receptor splice variant 7 (AR-V7) testing of circulating tumor cells (CTCs) from the patients

Summary

Introduction

Prostate cancer (PCa) is a major cause of disease and mortality among men worldwide each year, and 1.4 million men are diagnosed with PCa. Approximately 375,000 men died in 2020 of PCa [1]. PCa is recognized as a genetically heterogeneous disease, comprising a large scope of malignancies, from indolent localized cancers that may never progress to rapidly progressing castration-resistant PCa (CRPC) [2]. In accordance with the recent knowledge of clinicopathologies and genetics, the World Health Organization’s (WHO) classification of prostatic cancers has been revised, and five grade groups have been established [3]. This classification is based on biopsy or prostatectomy specimens. A valuable source of information is a noninvasive liquid biopsy, which can be used to characterize different components of body fluids, including circulating tumor cells (CTCs), cell-free DNA (cfDNA), circulating RNA, microRNAs, and extracellular vesicles (EVs), and can be prognostic of PCa outcome, predictive of response to treatment, or used to monitor disease [4]

Methods

Results

Conclusion