Myeloperoxidase gene expression in non-infant pro-B acute lymphoblastic leukaemia with or without ALL1/AF4 transcript

In this study we examined myeloperoxidase (MPO) gene expression in a series of 31 non-infant pro-B acute lymphoblastic leukaemia (ALL) patients that i ncluded 16 cases with the t(4;11) translocation andlor the resultant ALL1/A F4 chimaeric gene, Sixteen out of 31 cases (51%) were MPO mRNA positive/enz yme negative. MPO mRNA was detected in nine out of 16 (56%) and seven out o f 15 (47%) patients with and without the ALL1/AF4 fusion transcript respect ively. The comparative study between MPO mRNA positive and negative cases s howed statistically significant differences with regard to age and white bl ood cell (WBC) count, and was 39.5 years vs. 26.3 years (P = 0.016) and 71. 4 x 10(9)/l vs, 157.8 x 10(9)/l (P = 0.046) in the MPO mRNA positive and ne gative groups respectively. The correlation analysis between MPO mRNA expre ssion, age, WBC count and leukaemic relapse according to the presence/absen ce of the ALL1/AF4 fusion showed that the statistically significant differe nces observed in the whole group were related mostly to the ALL1/AF4-positi ve ALL patients, In fact, in this latter group, the mean WBC count and pati ents' age were 85 +/- 79 x 10(9)/l vs, 289.8 +/- 102 x 10(9)/l (P = 0.0005) and 44.8 +/- 15.3 years vs. 26.7 +/- 13.7 years (P = 0.01) in patients wit h and without MPO mRNA expression respectively. It appears, therefore, that the assessment of MPO mRNA expression enables a further dissection of leuk aemia heterogeneity in apparently homogeneous genetic/immunophenotypic ALL subsets.