BAALC-Expressing Leukemia Hematopoietic Stem Cells and Their Place in the Study of CBF-Positive Acute Myeloid Leukemias in Children and Adults

Background. Due to changing views on pathogenesis, risk factors and therapy strategies in prognostically favorable CBF-positive acute myeloid leukemias[1] (AML), the expression monitoring of RUNX1/RUNX1T1 or CBFB/MYH11 fusion genes, as an additional evaluation of treatment outcomes, appears to be insufficient. This indicates the need to improve the monitoring of the CBF+ AML course by means of parallel measurements of BAALC expression levels which roughly correlate with the mass of BAALC-expressing leukemia hematopoietic stem cells (BAALC-e LHSC). Aim. To improve the quality of assessing treatment outcomes with due account for expression levels of RUNX1/RUNX1T1 or CBFB/MYH11 fusion genes and the mass of BAALC-e LHSC and on this basis to pave the way for personalized CBF+ AML treatment. Materials & Methods. This study enrolled 39 adult patients aged 20–81 years (median 32 years) and 8 children aged 2–18 years (median 12 years). Among them there were 20 females and 27 males. AML with inv(16)(p13;q22)/t(16;16) was identified in 19 patients, t(8;21)(q22;q22) was detected in 28 patients. BAALC, WT1, RUNX1/RUNX1T1, CBFB/MYH11 expression levels were measured by quantitative real-time PCR and related to the expression of the ABL1 expert gene. Results. In 23 patients, inv(16) and t(8;21) appeared to be isolated. Additional multidirectional chromosomal changes were observed in 24 patients with inv(16) and in 18 patients with t(8;21). All enrolled patients showed increased BAALC expression. In the course of therapy, it was decreasing to the threshold value in 16/18 (89 %) patients. The evaluation of the mean BAALC expression levels in the pooled groups of children and adults with isolated findings of either inv(16) or t(8;21) showed the decrease of the BAALC-e LHSC mass only in children (p = 0.049). The comparison of the mean WT1 expression levels in the pooled groups of children and adults with isolated and additional chromosomal abnormalities revealed their significant decrease in patients with complicated variants (p = 0.023). Conclusion. The case reports provided in this paper show that the molecular monitoring with serial measurements of fusion genes and BAALC gene expression levels in CBF+ AML patients can lay the basis for further improvement of personalized treatment strategies for these patients. In all likelihood, parallel measurements of the above gene expression levels will allow to establish the framework for decision-making concerning treatment extent and timely HSC transplantation.