A Transcriptional- and Posttranscriptional-Based Prognostic Model in Pediatric Acute Myeloid Leukemia

Background. We have recently investigated transcriptional and posttranscriptional changes in AML cells (Oncotarget, 2016, 7, 2889-909) and identified ABCA3 expression, TET2 expression and TET2 exon 2 skipping (TET2E2S) as prognostic factors in pediatric AML (See companion abstracts from Ceraulo et al.). The present study was conducted in order to test whether the combination of these prognostic factors might help stratifying patients according to their relapse risk. Methods. Samples derived from 120 patients with available high-quality RNA and enrolled in the French ELAM2 protocol. Patients were classified according to their standardized cytogenetic and molecular (NPM1 mutations, FLT3-ITD, CEBPA double mutations) risk subgroups. Treatment consisted of 1 induction course (AraC and mitoxantrone) and 3 consolidation courses (course 1 and 3 with high dose AraC); all children with either intermediate or high-risk disease were candidates for hematopoietic stem cell transplant in complete remission (CR) after 1 to 2 consolidation courses. qRTPCR amplification of 2 conserved ABCA3 (exons 6-7 and exon 19-20) and TET2 (exon 4 and exon 2-3) mRNA sequences were performed with GUS and ABL as reference genes. TET2E2S was quantified as already described (Oncotarget, 2016, 7, 2889-909). The concordance index (c-index) was used to compare the relative statistical power of the new model compared with the standardized cytogenetic and molecular-based scoring system. Results. ABCA3 expression [HR 2.6 (95% CI 1.3-5), p=0.006], TET2 expression (HR 0.5 (0.2-0.9) p=0.04, and TET2E2S (HR 2.5 (1.2-5.1), p=0.01) represented independent prognostic factors for EFS. To design a convenient prognostic score, continuous variables were dichotomized using cutoff points that were based using the Maximally Selected Rank Statistics (maxstat R-statistics package, from the R-Project). One point was attributed for lower TET2 expression (n=85), higher ABCA3 expression (n=44), and TET2E2S (n=61). Three groups were formed: lower-risk patients (0 point, n=33), intermediate-risk patients (1 point, n=41), and higher-risk patients (either 2 or 3 points, n=46). The present score identified subgroups of patients with significantly different outcome (p Conclusion. We propose a new prognostic model that includes transcriptional and posttranscriptional data and can predict survival in pediatric AML. A validation in a larger, independent, multicenter, data set of patients is important to facilitate the translation of this model into clinical practice. Disclosures No relevant conflicts of interest to declare.