T cell receptor gamma (TCRG) gene rearrangements in Brazilian children with acute lymphoblastic leukemia: analysis and implications for the study of minimal residual disease.

The high frequency of T cell receptor gamma (TCRG) gene rearrangements in both B-lineage and T cell acute lymphoblastic leukemia (ALL), its easy detection and the lower incidence of oligoclonality make this gene one of the main target for the detection of minimal residual disease by PCR in childhood ALL. We analyzed the frequency and type of TCRG rearrangements in DNA samples obtained from the bone marrow of 102 Brazilian children at diagnosis using PCR and automatic sequencing. TCRG rearrangements were found in 69% of patients with B-lineage ALL and in 94% of patients with T cell ALL. In contrast to other studies, rearrangements involving the Vgamma9 segment reported to be uncommon were the most frequent both in B-lineage and T cell ALL and involved 49/109 (45%) of the rearranged alleles. This fact should be considered when standardizing consensus primers for the study of minimal residual disease in different populations.