Detection of human tumor cells by amplicon fusion site polymerase chain reaction (AFS-PCR)

Reliable diagnostic strategies for individuals with cancer demand practical methods for highly sensitive and specific detection of tumor cells. Amplification of genomic regions that include putative oncogenes is common in tumor cells of various types. Genomic array platforms offer the opportunity to identify and precisely map amplified genomic regions (ampGRs). The stable existence of these tumor cell-specific genomic aberrations during and after therapy, in theory, make ampGRs optimal targets for cancer diagnostics. In this study, we mapped ampGRs around the proto-oncogene MYCN of human neuroblastomas using a high-resolution tiling array (HR-TA). Based on the HR-TA data, we were able to precisely describe the telomeric and centromeric borders of the ampGRs and deduce virtual fusion sites of the joined ampGRs (amplicon fusion sites [AFSs]). These AFSs served as blueprints for the subsequent design of AFS bridging PCR assays (AFS-PCRs). Strikingly, these assays were absolutely tumor cell specific and capable of detecting 1 tumor cell in 1 x 10(6) to 8 x 10(6) control cells. We successfully proved the in vivo practicability of AFS-PCR by detecting and quantifying the specific AFS DNA of human MYCN-amplified neuroblastomas in the patients' corresponding peripheral blood and bone marrow samples. Thus, we believe AFS-PCR could become a powerful and nevertheless feasible personalized diagnostic tool applicable to a large number of cancer patients, including children with MYCN-amplified neuroblastomas.