Abstract 3918: Identification of disseminated prostate tumor cells in bone marrow during radical prostatectomy from patients with localized prostate cancer
Authors: Glavaris Stephanie A. , Toom Emma E. van der , Gorin Michael , Verdone James , Lu Changxue , Luo Jun , Pienta Kenneth , Chalfin Heather 
Published: July 2017

INTRODUCTION AND OBJECTIVES In prostate cancer, disseminated tumor cells (DTC) can escape the primary lesion and enter the bone marrow (BM) niche, representing an initial step towards conventionally detectable metastasis. The frequency of occurrence is elusive in clinically localized prostate cancer. We detected and characterized these cells by measuring gene expression of prostate-specific markers from BM samples collected at the time of radical prostatectomy (RP).

METHODS 5 mL of BM were harvested at RP for 36 clinically localized patients. A whole cell extract was assayed with the AdnaTest ProstateCancerSelect kit (Qiagen). Reverse transcription (SensiScript RT kit, Qiagen) and real-time qPCR quantified expression of RPL13A (control, ribosomal protein), EPCAM (epithelial), NKX3.1 and HOXB13 (prostate-specific), and AR-FL (androgen receptor full length). Prostate markers known to be less sensitive or specific were also assayed in a subset of patients (TMPRSS2-ERG, AR-V7, PSA, and PSMA). DTC detection was defined as prostate-specific marker expression in the BM. Quality control was performed with Sanger sequencing. The associations of PSA and Gleason score (GS) with DTC detection were evaluated with the Mann-Whitney U Test and Fisher’s exact test respectively.

RESULTS DTC were detected via NKX3.1 expression in 30/36 patients (83%). 100% of patients were EPCAM+, consistent with the known non-specific expression of EPCAM in the BM. HOXB13, AR-V7, and TMPRSS2-ERG were not detected in any sample. AR-FL was also non-specifically expressed in 67% of NKX3.1+ and 83% of NKX3.1- patients. There was a pattern with DTC detection and higher PSA and GS, with 100% of NKX3.1- patients having low-risk PSA less than 10, and only one with primary GS greater than 3 (17%, 1/6). Conversely 47% (14/30) of NKX3.1+ patients had primary GS greater than or equal to 4, and 27% (8/30) had PSA greater than 10. Yet, this was not statistically significant (GS p=0.367, PSA p=0.302), and DTC were detected across all Gleason scores.

CONCLUSIONS DTC were detected based on NKX3.1 positivity in a large portion of clinically localized prostate cancer patients at all Gleason scores. Ongoing investigation with healthy patient BM will clarify whether NKX3.1 is truly prostate-specific, and if its expression associates with clinico-pathologic outcomes.

Citation Format: Stephanie A. Glavaris, Emma E. van der Toom, Michael Gorin, James Verdone, Changxue Lu, Jun Luo, Kenneth Pienta, Heather Chalfin. Identification of disseminated prostate tumor cells in bone marrow during radical prostatectomy from patients with localized prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3918. doi:10.1158/1538-7445.AM2017-3918