MEF2C expression, but not absence of bi-allelic deletion of TCR gamma chains (ABD), is a predictor of patient outcome in Indian T-acute lymphoblastic leukemia

Abstract

Emerging evidence suggests existence of three prognostically relevant molecular entities among immature TALL early thymic precursor ALL (ETP-ALL), TALL with the absence of biallelic deletion of TCRγ chains (ABD) and MEF2C (Myocyte Enhancer Factor 2C) high TALL. However, the usefulness of ETP-ALL immunophenotype and assessment of ABD for this purpose has been questioned and, MEF2C has not been studied in much detail. In this prospective analysis of 143 TALL patients, we evaluated the mutual association of these three entities and also determined how immunophenotypically-defined poor prognosis immature TALL relates to these entities. We found that all three of them, especially ABD, nearly completely characterized the immature group. High MEF2C expression reflected ETP-ALL somewhat poorly and a few ABD and MEF2C-high patients had non-immature immunophenotype-findings, that though in accord with published literature, call for exploration per T-cell receptor (TCR) classification scheme. ETP-ALL and MEF2C high but not ABD had a higher frequency of minimal residual disease positivity and poor event-free survival. MEF2C high, not ETP-ALL immunophenotype or ABD, had poorer overall survival. The value of ETP-ALL immunophenotype and MEF2C status, as indicators of poor treatment response, needs further evaluation for possible incorporation in standard TALL management practice.