Utility of Qdot FISH Probes for Detecting Gene Rearrangements in Prostate Cancer
U Sathyanarayana, C Lafargue, D Nagy, J Riley, M Bachrach, R Esgueva, A Santa-Cruz, N Palanisamy, R Nagle, M Rubin, F Demichelis, P Miller, G Pestano. Ventana, a Member of the Roche Group, Tucson; Weill Cornell Medical College, NYC; University of Michigan Medical School, Ann Arbor; Arizona Cancer Center, Tucson
Background: Prostate cancer is one of the most prevalent malignancies affecting men worldwide. While men with distal spread of prostate cancer have a 5 year survival of 32%, for those with organ-confined disease it is 100%. It is thus critical to correctly diagnose and treat prostate cancer. Rearrangements in the ETS gene in prostate cancer has both therapeutic and diagnostic implications. Gene fusions identified thus far are characterized by 5' regulatory elements (example TMPRSS2), fused to transcription factors, including ERG, ETV1, 4 and 5.
Design: In this report, we describe the development of automated in situ hybridization sssays including novel repeat-depleted DNA probes, and Qdot bioconjugates. In an initial study, the new ERG-specific probes were evaluated for concordance with BAC probes developed using traditional methods and currently cited in the literature. Two prostate cancer cohorts with a total of 107 clinical cases represented on tissue microarrays were evaluated using ERG break-apart probes. Both cohorts were previously characterized for ERG rearrangement status using BAC clones RP11-24A11 (3' ERG) and RP11-372O17 (5' ERG) labeled with organic dyes. Slides were independently evaluated by three individual readers.
Results: We have shown sensitive and specific detection of gene rearrangements with these reagents in xenografts, prostate needle biopsies, and in radical prostatectomies. Specifically, there were 103 cases and 175 foci that were evaluable by both the newly developed ERG break-apart probes and the traditionally developed BAC probes. The various genomic events assessed were: no rearrangement, translocation through insertion, and translocation through deletion. Overall, there was 100% concordance between evaluations using either probe set.
Conclusions: In summary, these reagents provide new technology for detecting diagnostic markers in situ. Qdots provide greater signal intensity and stability for fluorescence detection, while repeat-depleted probes increase sensitivity of the assay for the target genes. Studies are in progress to validate these reagents in selected cancer and biopsy cohorts. This novel assay is also being developed to allow for the detection of multiple translocation events in single cells in prostate cancer.
Category: Genitourinary (including renal tumors)
Wednesday, March 24, 2010 1:00 PM
Poster Session VI # 124, Wednesday Afternoon