Serum BCL2/IGH DNA in follicular lymphoma patients: A minimal residual disease marker

The majority of follicular lymphoma patients carry a t(14;18) juxtaposing t he BCL2 oncogene to the immunoglobulin heavy chain joining region (IgH). Mo lecular analysis for follicular lymphoma-specific DNA translocations may pe rmit evaluation of minimal residual disease (MRD), We identify extracellula r BCL2/IGH transgene DNA in the serum of patients with follicular lymphoma, and evaluate its utility as a surrogate marker. DNA was harvested from bot h the sera and bone marrow of 5 stage IV follicular lymphoma patients prior to and after chemotherapy and following a novel vaccine-based regimen. Ser ial PCR amplifications were performed using heminested BCL2-specific major breakpoint cluster region (MBR) primers and the immunoglobulin heavy chain consensus primer. Amplification products were detected by agarose gel elect rophoresis, and comparison was made to amplification products from the orig inal tumor biopsy. Results show that four of the five lymphoma patients car ried extracellular BCL2/IGH transgene DNA in their serum. The remaining pat ient did not have an amplification product from either the tumor or the ser um, suggesting either the absence of a translocation or the presence of a v ariant translocation not detectable with this primer set. Transgene DNA was detectable in serum even in patients with MRD, comparing favorably with bo ne marrow results. In at least one patient, the presence of the transgene i n serum at the conclusion of therapy preceded relapse. In conclusion, it se ems that tumor-specific, extracellular DNA is present in the serum of folli cular lymphoma patients, including those with MRD, Because extracellular DN A may be released into the bloodstream by tumor throughout the body it may be less subject to sampling error, and appears to be an ideal surrogate mar ker.