Detection of Androgen Receptor Variant 7 (ARV7) mRNA Levels in EpCAM-Enriched CTC Fractions for Monitoring Response to Androgen Targeting Therapies in Prostate Cancer

Abstract

Expression of the androgen receptor splice variant 7 (ARV7) in circulating tumor cells (CTCs) has been associated with resistance towards novel androgen receptor (AR)-targeting therapies. While a multitude of ARV7 detection approaches have been developed, the simultaneous enumeration of CTCs and assessment of ARV7 status and the integration of validated technologies for CTC enrichment/detection into their workflow render interpretation of the results more difficult and/or require shipment to centralized labs. Here, we describe the establishment and technical validation of a novel ARV7 detection method integrating the CellSearch® technology, the only FDA-cleared CTC-enrichment method for metastatic prostate cancer available so far. A highly sensitive and specific qPCR-based assay was developed, allowing detection of ARV7 and keratin 19 transcripts from as low as a single ARV7+/K19+ cell, even after 24 h of sample storage. Clinical feasibility was demonstrated on blood samples from 26 prostate cancer patients and assay sensitivity and specificity was corroborated. Our novel approach can now be included into prospective clinical trials aimed to assess the predictive values of CTC/ARV7 measurements in prostate cancer.

Dual Inhibitory Action of a Novel AKR1C3 Inhibitor on Both Full-Length AR and the Variant AR-V7 in Enzalutamide Resistant Metastatic Castration Resistant Prostate Cancer

“…All cell lines were cultivated at 37 °C in a humidified atmosphere with 5% CO 2 . AR-V7 status of the used cell lines: 22Rv1: AR-V7 positive [ 37 ], DuCaP: AR-V7 positive [ 38 ], DuCaP EnzaR: AR-V7 positive [ 38 ], PC-3: AR-V7 negative [ 65 ].…”

AR-V7 Protein Expression in Circulating Tumour Cells Is Not Predictive of Treatment Response in mCRPC

“…The high AR-V7 detection rate in our study could also be caused by multiple pre-treatment at the stage of CRPC and overall insufficient performance status at a high tumour burden [18]. However, a limitation of the predictive value of AR-V7 in our study could be based on small cohort size (n = 26) and possible widely reported cross-reaction of AR-V7 antibodies [18,23,[31][32][33].…”

Circulating Tumor Cells Expressing the Prostate Specific Membrane Antigen (PSMA) Indicate Worse Outcome in Primary, Non-Metastatic Triple-Negative Breast Cancer

“…In this regard, from the technical point of view, El-Heliebi et al, published the feasibility and utility of in situ padlock probe technology for the analysis of AR-V7, AR-FL, and PSA expression in combination with immunostaining (panCK and CD45) in CTCs from PCA patients (50). Furthermore, using the CellSearch system for enrichment, followed by the detection of AR-V7 transcripts applying qPCR, adapted from the original Antonarakis et al publication in 2014, allowed the detection of AR-V7 and keratin 19 (K19) transcripts from as low as a single AR-V7+/K19+ cell (36,51). In the context of clinical studies, patients with CTCs expressing AR-V7 showed worst outcome when compared to those patients harboring AR-V7-negative CTCs or no CTCs (52).…”