DNA-FISH was carried out according to a method for single copy loci detection (28) . The protocol was adapted with few modifications, using 50-mer oligonucleotides specific to the loci of interest and labeled with a desired hapten. Two probes were used for FISH for breakapart assay. A probe located at the promoter region of TMPRSS2 was labeled with biotin (Bio/GACTCCA GGAGCGCTCCCCAGAATCCCCTTCCTTAACCCA AACTCGAGCC). The other probe at exon 2 of ERG was labeled with 5 0 -6-carboxyfluorescein (56FAM) (56FAM/ GATCTTTGGAGACCCGAGGAAAGCCGTGTTGA CCAAAAGCAAGACAAATG). Detection of probes was achieved by using antibodies conjugated to quantum dots (Qdot) against the hapten label. Conditions were optimized to use a combination of two antibodies (1 : 200) obtained from Invitrogen-Molecular Probes TM (Qdot 655 Ã sheep anti-Bio primary antibody conjugate; Qdot 525 Ã Goat anti-FITC whole IgG primary antibody conjugate). Image acquisition was done with a Zeiss Axioplan 2e microscope (Carl Zeiss, Inc.). All pictures in the corresponding three channels were deconvolved and optical sections merged to produce 2D pictures using Axiovision 4.0 software (Carl Zeiss, Inc.) and Image J (Rasband, W.S., ImageJ, U. S. National Institutes of Health, Bethesda, MD, USA, http://rsb.info.nih.gov/ij/, 1997-2006.)