Circulating Prostate Tumor Cells Detected by Reverse Transcription-PCR in Men with Localized or Castration-Refractory Prostate Cancer: Concordance with CellSearch Assay and Association with Bone Metastases and with Survival

Abstract

Background: Reverse transcription-PCR (RT-PCR) assays have been used for analysis of circulating tumor cells (CTCs), but their clinical value has yet to be established. We assessed men with localized prostate cancer or castration-refractory prostate cancer (CRPC) for CTCs via real-time RT-PCR assays for KLK3 [kallikrein-related peptidase 3; i.e., prostate-specific antigen (PSA)] and KLK2 mRNAs. We also assessed the association of CTCs with disease characteristics and survival. Methods: KLK3, KLK2, and PSCA (prostate stem cell antigen) mRNAs were measured by standardized, quantitative real-time RT-PCR assays in blood samples from 180 localized-disease patients, 76 metastatic CRPC patients, and 19 healthy volunteers. CRPC samples were also tested for CTCs by an immunomagnetic separation system (CellSearch™; Veridex) approved for clinical use. Results: All healthy volunteers were negative for KLK mRNAs. Results of tests for KLK3 or KLK2 mRNAs were positive (≥80 mRNAs/mL blood) in 37 patients (49%) with CRPC but in only 15 patients (8%) with localized cancer. RT-PCR and CellSearch CTC results were strongly concordant (80%–85%) and correlated (Kendall τ, 0.60–0.68). Among CRPC patients, KLK mRNAs and CellSearch CTCs were closely associated with clinical evidence of bone metastases and with survival but were only modestly correlated with serum PSA concentrations. PSCA mRNA was detected in only 7 CRPC patients (10%) and was associated with a positive KLK mRNA status. Conclusions: Real-time RT-PCR assays of KLK mRNAs are highly concordant with CellSearch CTC results in patients with CRPC. KLK2/3-expressing CTCs are common in men with CRPC and bone metastases but are rare in patients with metastases diagnosed only in soft tissues and patients with localized cancer.

ApoStream™, a new dielectrophoretic device for antibody independent isolation and recovery of viable cancer cells from blood

“…3, 16 It is inapplicable to cancers of non-epithelial origin such as melanoma, brain cancers, and sarcomas as well as advanced metastatic disease where EpCAM expression is lost. 17,18 The immunomagnetic isolation procedure associated with CTC identification with the CellSearch system involves chemical and mechanical manipulation that creates challenges to culture these cells for downstream analysis.…”

Microchips and their Significance in Isolation of Circulating Tumor Cells and Monitoring of Cancers

“…In this case, prognostic markers which are expressed adequately in early stages should be considered as proper target for detection (Allan and Keeney, 2010). The most applicable markers in this regard include cytokeratin-19, cytokeratin-20 or CEA, and PSA or PSCA which are used to isolate CTCs in early stages of breast, colorectal, and prostate cancers, respectively (Stathopoulou et al, 2003;Allen-Mersh et al, 2007;Helo et al, 2009).…”

Rational Design of Materials Interface for Efficient Capture of Circulating Tumor Cells

“…Hence, EpCAM is one expressed CTC‐associated biomarkers known, and CTC isolation techniques based on EpCAM antibodies are widely used 44, 45. The popular CellSearch system, which has been extensively used to capture and isolate CTCs from the blood of patients with cancers of the breast, prostate, and colon, employs a conjugation of EpCAM antibodies to ferrofluidic beads to enable the capture of CTCs through a magnetic field 46, 47, 48. In addition to EpCAM, several studies have reported that HER2 is overexpressed in CTCs of both metastatic and early breast cancer patients, and clinical data has shown that the change of HER2 status from low level expression to high level also occurred along with breast cancer recurrence and progression 49, 50.…”