PTEN loss in circulating tumour cells correlates with PTEN loss in fresh tumour tissue from castration-resistant prostate cancer patients

Abstract

Background:PTEN gene loss occurs frequently in castration-resistant prostate cancer (CRPC) and may drive progression through activation of the PI3K/AKT pathway. Here, we developed a novel CTC-based assay to determine PTEN status and examined the correlation between PTEN status in CTCs and matched tumour tissue samples.Methods:PTEN gene status in CTCs was evaluated on an enrichment-free platform (Epic Sciences) by fluorescence in situ hybridisation (FISH). PTEN status in archival and fresh tumour tissue was evaluated by FISH and immunohistochemistry.Results:Peripheral blood was collected from 76 patients. Matched archival and fresh cancer tissue was available for 48 patients. PTEN gene status detected in CTCs was concordant with PTEN status in matched fresh tissues and archival tissue in 32 of 38 patients (84%) and 24 of 39 patients (62%), respectively. CTC counts were prognostic (continuous, P=0.001). PTEN loss in CTCs associated with worse survival in univariate analysis (HR 2.05; 95% CI 1.17–3.62; P=0.01) and with high lactate dehydrogenase (LDH) in metastatic CRPC patients.Conclusions:Our results illustrate the potential use of CTCs as a non-invasive, real-time liquid biopsy to determine PTEN gene status. The prognostic and predictive value of PTEN in CTCs warrants investigation in CRPC clinical trials of PI3K/AKT-targeted therapies.

Phenotypic Heterogeneity of Circulating Tumor Cells Informs Clinical Decisions between AR Signaling Inhibitors and Taxanes in Metastatic Prostate Cancer

“…These positive selection methods often miss critical CTC subtypes and do not consistently assess cell features essential to the analysis of heterogeneity. The CAP-accredited and CLIA-certified Epic Sciences platform used here has undergone the necessary analytical validation (accuracy, linearity, specificity, and intra/inter-assay precision) for CTC detection and enumeration (26) and has been previously demonstrated to detect a wide range of CTC phenotypes (32,33,40,43). These include rare CTCs that are negative for epithelial markers with malignant genomics (40,43) and CTCs that are smaller than WBCs (32,43).…”

“…Red blood cells were lysed, and approximately 3 million nucleated cells were dispensed onto 10–16 glass microscope slides and placed at −80 °C for long-term storage as previously described (26,32,33). Sample processing and testing were conducted in laboratories following both Clinical Laboratory Improvement Amendments (CLIA) and College of American Pathologists (CAP) regulations.…”

“…CTCs were characterized by automated immunofluorescent staining for DAPI (a DNA stain), cytokeratins, CD45 (hematopoietic lineage marker), and AR N-terminal domain (AR) (Cell Signaling D6F11) as previously described (26,32,33). Up to two slides were evaluated per sample tested.…”

Current treatment strategies for advanced prostate cancer

“…83 Genetic alternations, such as PTEN loss, have been investigated and proved that patients with this loss seem to be associated with worse outcome. 84,85 In addition, other genetic alternations cause the dysregulation of AR signaling, which might be exploited to develop a new molecular biomarker for disease prediction. ERG, one of the erythroblast transformation-specific transcription factors, often fuses with the promoter region of the TMPRSS2 gene (21q21.2-3), called TMPRSS2/ERG fusion, and upregulation of the ERG expression level by AR binding to the promoter of TMPRSS2 plays a pivotal role in tumorgenesis with cooperation of other important somatic mutations.…”

The Heterogeneity of Prostate Cancer: A Practical Approach

“…Another potential problem for such studies is the necessity to obtain the tissue for molecular analysis from metastases, which is normally not indicated from the clinical point of view [81]. However, some modern research technologies (single-cell sequencing, single-nucleus sequencing, circulating tumor DNA analysis) would support these efforts [69,82,83,84,85,86]. While the very complex clonal heterogeneity in patients with metastatic disease [72] is under investigation, some studies show that analysis of a single metastasis could be enough to assess major oncogenic driver events because the genomic diversity between metastases is limited [37].…”