REARRANGEMENTS OF IGH, TCRD AND TCRG GENES AS CLONALITY MARKER OF CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIA
Aim: Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements are excellent patient-specific targets for clonality studies and monitoring of acute lymphoblastic leukemia (ALL). The aims of the study were to select the optimum panel of primers, evaluate incidence of particular types of monoclonal and oligoclonal gene rearrangements and observe alteration of rearrangement profile between diagnosis of ALL and subsequent relapse(s). Methods: We used polymerase chain reaction (PCR) for amplification of junctional region of rearranged IgH, TCRD and TCRG genes in combination with heteroduplex analysis in polyacrylamide gel. Results: TCRD gene rearrangements were detected in 64%, TCRG – in 45%, and IgH – in 79% of B-precursor ALL patients. For patients with T-ALL, TCRD gene rearrangements were found in 47%, TCRG gene – in 66%, and IgH – in 19% of cases. Evaluation of biallelic and oligoclonal rearrangements was performed in the study. The highest incidence of oligoclonal rearrangements - 25% was shown for IgH gene in patients with B-precursor ALL. Seven pair cases of patients with de novo leukemia and relapses were analyzed and revealed subclonal deviation in rearrangements of IgH or TCR genes during disease evolution. Conclusion: We propose a panel of 13 types of rearrangements (primer pairs) sufficient for tumor cell clonality detection in 96% of patients with ALL. Applications of PCR-based analysis of rearranged IgH, TCRD and TCRG genes for discrimination of mono- and oligoclonality and identification of the origin of relapse were demonstrated.
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