Login to Access Video or Poster Abstract: MP33-12
Sources of Funding: Work is supported by NCI/EDRN ACN12011-001-0 and NCI RO1 CA162383-05 grants to SS

Introduction

Prostate cancer (CaP) affects 1 in 7 men in their life time. One of the major risk factors for the development of CaP is race/ethnicity. African American (AA) men have significantly higher incidence and mortality from CaP compared to Caucasian American (CA) men. Emerging data including ours have described significantly lower frequencies of alterations in common CaP driver genes (ERG and PTEN) in AA men as compared to CA men. We have also noted that genes commonly overexpressed in CaP (ERG, AMACR, PCA3), and currently used as diagnostic markers, exhibit much lower frequency and more heterogeneity in AA men. The goal of this study was to define a CaP marker panel that is overexpressed equally well in AA and CA CaP.

Methods

Three platforms (RNASeq, NanoString and qRT-PCR) were used for evaluation of CaP associated gene expression in CA and AA patients (N=144). Candidate genes with robust tumor overexpression (over 4-fold) in CaP in paired normal and tumor specimens from AA and CA patients were selected from Nanostring and RNASeq data for validation by qRT-PCR (TaqMan) in laser microdissected (LCM) tumor and benign cells of frozen tissue sections (50 CA and 35 AA). An assay protocol (gene specific RT and pre-amplification followed by TaqMan PCR) was set up for noninvasive early detection of candidate genes in regular patient urine (non-DRE) using urinary exosomal RNA.

Results

As expected tumor transcriptomes of CA patients consistently revealed elevated expression of PCA3 and AMACR. However, these genes had variable overexpression in AA cohort. The top genes that were similarly over expressed in tumors of AA and CA patients were validated by qRT-PCR in LCM tumor and normal epithelial cells (N=85). At least one gene of a six gene signature (DLX1, HOXC4, NKX2-3, COL10A1, HOXC6 and PSGR) was overexpressed in tumor cells of all AA and CA cases, providing a consistent ethnicity informed tumor expression signature, which was further validated in silico in TCGA RNASeq data. Urinary exosome based assay was developed and optimized for PSGR, DLX1, HOXC4, NKX2-3, as well as PCA3 and ERG. Sensitivity and specificity in a feasibility cohort (N=40) with optimal cutoff for the urine marker panel was 71% and 61%, respectively. Evaluation of the assay performance in CA and AA patients in a prospective independent cohort of 100 patients is in progress.

Conclusions

A CaP tissue based gene expression marker panel has been defined with potential diagnostic utility for both CA and AA men in the context of urinary exosomes.

Funding

Work is supported by NCI/EDRN ACN12011-001-0 and NCI RO1 CA162383-05 grants to SS