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Identification of ABCA5 as a tissue and urine diagnostic marker for PIN
Journal article   Peer reviewed

Identification of ABCA5 as a tissue and urine diagnostic marker for PIN

M. E. Stearns, Y. Hu, M. Wang and K. A. Veverka
Journal of clinical oncology, v 25(18_suppl), pp 15508-15508
20 Jun 2007
DOI: https://doi.org/10.1200/jco.2007.25.18_suppl.15508

Abstract

15508 Background: Bostwick and colleagues have suggested that prostatic intraepithelial neoplasia or PIN is the precursor of prostate cancer, and that a significant percentage of men with PIN develop prostate cancer (Sakr, 1994; Bostwick, 1995b; Arakawa, 1995; Qian, 1995; Qian, 1997). Currently there are no molecular diagnostic markers for PIN. Methods: Recently, we have developed ‘DNA-protein’ binding assays for the identification of novel transcriptional regulatory proteins associated with PIN glands. Electrophoretic mobility shift assays (EMSAs) with the 32P-labeled DNA probe was used for analysis of protein extracts from tissues and urine. Immunolabeling was carried out with rabbit antibodies specific for ABCA5. Results: Electrophoretic mobility assays (EMSAs) revealed that 1 DNA sequence (1 of 4,096 sequences screened) specifically bound a ∼160 Kda protein which was over-expressed in PIN and not found in BPH, SV or PCA glands (n=11). The gene encoding for the 160 Kda protein was cloned from a cDNA expression library by ‘in situ’ hybridization assays with the 32P-labeled DNA sequence. Sequencing revealed that the gene encoding for the 160 Kda protein was ABCA5, a member of the superfamily of ATP-binding cassette (ABC) transporters of multi-drug resistant genes. RT-PCR assays indicated the mRNA was over-expressed in PIN tissue, and was not present in BPH, or SV tissue. Rabbit polyclonal antibodies and immunolabeling showed that the antibodies specifically labeled the cell junctions of 3% glutaraldehyde fixed prostate cells. Immunohistochemistry indicated that ABCA5 was over expressed in foci of intermediate basal cells in normal glands, and in HGPIN. ABCA5 was faintly expressed in PCA glands. Enzyme linked immunoabsorbent assays (ELISAs) demonstrated in blinded studies that ABCA5 was a highly sensitive (>98% sensitivity) urine diagnostic marker for HGPIN in biopsy positive patients (n=107) at a cut off” of 25 ng/ml. ABCA5 was present at very low levels (i.e. <25 ng/ml) in the urine of patients diagnosed with BPH (n=79) or prostatitis or kidney and bladder cancer (>86% specificity). Conclusions: The data suggest that the expression of ABCA5 is over-expressed by PIN and may be a highly sensitive and specific urine diagnostic marker for detection of early stage prostate cancer. No significant financial relationships to disclose.

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