A prostate cancer cell line, VCaP, (30) with a TMPRSS2 and ERG fusion (2) was used for initial feasibility testing. The total RNA was subjected to RT-PCR with a pair of primers located at exon 6 of ERG and exon 1 of TMPRSS2 (2, 9) . The unpurified product was labeled and hybridized on the microarray ( Figure 1B ). Only spots corresponding to exon 1 of TMPRSS2 and exons 4-5 of ERG developed strong signals. This result indicates the fusion junction is at the exon 1 of TMPRSS2 and exon 4 of ERG, which is consistent with a previous report (2) .