HER-2 Expression in Secondary Circulating Prostate Cells does not Increase Risk of Biochemical Failure after Radical Prostatectomy for Prostate Cancer

Research Article

Austin J Cancer Clin Res 2014;1(3): 1015.

HER-2 Expression in Secondary Circulating Prostate Cells does not Increase Risk of Biochemical Failure after Radical Prostatectomy for Prostate Cancer

Murray NP1,2,3*, Reyes E1,4, Fuentealba C1, Orellana N1 and Dueñas R1

1Department of Urology, Hospital Carabineros, Chile

2Department of Medicine, Universidad Mayor, Chile

3Institute of Bio-Oncology, Chile

4Department of Medicine, Universidad Diego Portales, Chile

*Corresponding author: Murray NP, Department of Medicine, Institute of Bio-Oncology, Hospital Carabineros, Simon Bolivar 2200 Providencia, Santiago, Chile

Received: June 24, 2014; Accepted: July 24, 2014; Published: July 25, 2014


Introduction: There is evidence linking HER-2 expression in prostate cancer to disease progression and the development of androgen independent disease. HER-2 expression increases after androgen blockade and is associated with increased prostate cancer specific mortality. We present the effect of HER-2 expression in circulating prostate cells (CPCs) on the risk of biochemical failure and its association with standard clinic-pathological parameters.

Methods and patients: Blood samples were taken 4 monthly after radical prostatectomy to detect CPCs using anti-PSA and standard immunocytochemistry. Samples positive for CPCs underwent analysis for HER-2 expression using the HercepTest® kit. Standard clinicopathological parameters were recorded. Kaplan Meier plots determined the different biochemical failure free survival curves.

Results: 92 biochemical failure free men participated, 37/92(40.2%) of men had secondary CPCs detected. Biochemical failure was significantly more frequent in men CPC positive than those CPC negative (p=0.001). The expression of HER-2 in secondary CPCs did not increase biochemical failure free survival in comparison with men CPC (+) HER-2 (-).

Conclusion: In men without biochemical failure the expression of HER-2 positive CPCs did not increase the risk of developing biochemical failure.

Keywords: Prostate cancer; Circulating prostate cells; HER-2; Biochemical failure


There is evidence linking the expression of HER-2 in prostate cancer to disease progression and the development of androgen independent disease. HER-2 is a member of the ErbB family of receptor tyrosine kinases and plays a crucial role in growth, differentiation, and motility of normal and cancer cells. HER-2 has been proposed as a survival factor for prostate cells in the absence of androgens, possibly by activating the androgen receptor [1-3]. In hormone-naive patients, whether in patients undergoing observation, or post-treatment with or without biochemical failure, the expression of HER-2 is infrequent both in the original tumor, circulating prostate cells (CPCs) and micro metastasis [2,4], whereas patients treated with androgen blockage have significantly increased levels of HER-2 expression in both the original tumor, CPCs and micro metastasis [2,4]. There is a suggestion that HER-2 may have a role in prostate cancer development, however its expression is variable, ranging between 0 to 100% depending on the HER-2 assay used [5] and gene amplification ranges from 0 to 53% [6,7]. Despite this discrepancy, there is still a consistent association between HER-2 over expression with a higher risk of death and recurrence in men with prostate cancer according to a meta-analysis [8]. Secondary CPCs are associated with a seven fold increase of biochemical failure after radical prostatectomy and CPC detection using standard immunocytochemisty is able to identify a high risk group for biochemical failure before there is a rise in the serum PSA [9].

We present a prospective study of the detection of secondary CPCs and the expression of HER-2 in men with a PSA <0.2ng/ml, the association with clinic-pathological parameters and the occurrence of biochemical failure.

Patients and Methods

Patient selection

From January 2009 to December 2011 blood samples from consecutive prostate cancer patients were prospectively collected for the purpose of detecting CPCs and evaluating whether these cells were correlated with clinical outcomes. All patients who had undergone radical prostatectomy at the author’s institution and all those seen during follow up were invited to participate. Samples were taken from men at least three months after surgery and considered to be without evidence of disease and repeated four monthly. This was defined as being bone scan negative and a serum PSA <0.20ng/ ml. A group of men with a serum PSA of 0.2-1.0ng/ml and bone scan negative were selected to represent men with biochemical failure. All samples were obtained after written informed consent and collected using protocols approved by the local ethics committee.

Sample collection and cell enrichment

8ml of venous blood was collected in tubes containing EDTA (Beckson-Vacutainer®). Mononuclear cells were obtained using gel differential centrifugation using Histopaque 1,077® (Sigma-Aldrich) at room temperature according to manufacturer’s instructions and finally washed 3 times in phosphate buffered saline pH 7.4 (PBS). The pellet was re-suspended in 100μl of autologous plasma and 25µl used to prepare each slide (sialinzed DAKO, USA). The slides were air dried for 24 hours and finally fixed in a solution of 70% ethanol, 5% formaldehyde and 25% PBS for 5 minutes and then washed 3 times with PBS.

Identification of CPCs

Slides were processed within 1 hour of fixation and incubated with anti-PSA clone 28A4 (Novocastra Laboratory, UK) in a concentration of 2.5 μg/ml for 1 hour at room temperature and identified using a detection system based on alkaline phosphatase-antialkaline phosphatase (LSAB2 DAKO, USA) with new-fuschin as the chromogen. To permit the rapid identification of positive cells there was no counter staining with Mayer’s hematoxilin. Levisamole (DAKO, USA) was used as an inhibitor of endogenous alkaline phosphatase. Positive and negative controls were processed in the same way. Definition of secondary CPCs using the criteria of ISHAGE was used to identify immunostained cells [10] (Figure 1A-B). A sample was classified as CPC positive if 1 cell PSA positive was detected.