Pattern of immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements in childhood acute lymphoblastic leukemia in India

Abstract 

In 120 cases of acute lymphoblastic leukemia (median age 8 years), IgH chain gene was rearranged in 99% B-Cell Precursor (BCP) ALLs and 13% T-ALLs. One or the other TCR locus was rearranged not only in all T-ALLs, but also in 87% of BCP-ALLs. TCR-β rearrangement in BCP-ALL was associated with a higher mean age at presentation (8.7 vs. 6.2 years, P=0.008), lower mean platelet counts (61.2×10⁹/l vs. 103.7×10⁹/l, P=0.003) and a poorer DFS (% cummulative survival 0 vs. 88.9±10.5, P=0.004). TCR-γ rearrangement in T-ALL was associated with a higher mean WBC count (186.3×10⁹/l vs. 63.4×10⁹/l, P=0.002). Also, the pattern of rearrangement of these genes appeared to be different from the West; viz. TCR-β rearrangement in a higher proportion of BCP-ALLs (58%, 95% confidence intervals 45–69%), invariable deletion of Cγ1 and only monoallelic rearrangement for TCR-δ locus. This repertoire of gene rearrangement may have a bearing on the poor treatment outcome reported previously from our geographic region.

Keywords:  ALL in India, Biology of ALL, Childhood ALL, Ig gene rearrangements, Immunophenotype, TCR gene rearrangements

Abbreviations:  ALL, acute lymphoblastic leukemia, BCP, B-cell Precursor, C-ALL, common ALL, DFS, disease free survival, T-ALL, T-cell ALL, Ig, Immunoglobulin, TCR, T-cell receptor