Prenatal origin of childhood AML occurs less frequently than in childhood ALL

Background: While there is enough convincing evidence in childhood acute lymphoblastic leukemia ( ALL), the data on the pre-natal origin in childhood acute myeloid leukemia (AML) are less comprehensive. Our study aimed to screen Guthrie cards ( neonatal blood spots) of non-infant childhood AML and ALL patients for the presence of their respective leukemic markers. Methods: We analysed Guthrie cards of 12 ALL patients aged 2 - 6 years using immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements ( n = 15) and/or intronic breakpoints of TEL/AML1 fusion gene ( n = 3). In AML patients ( n = 13, age 1 - 14 years) PML/RARalpha ( n = 4), CBFbeta/ MYH11 ( n = 3), AML1/ETO ( n = 2), MLL/AF6 ( n = 1), MLL/AF9 ( n = 1) and MLL/ AF10 ( n = 1) fusion genes and/or internal tandem duplication of FLT3 gene (FLT3/ITD) ( n = 2) were used as clonotypic markers. Assay sensitivity determined using serial dilutions of patient DNA into the DNA of a healthy donor allowed us to detect the pre-leukemic clone in Guthrie card providing 1 - 3 positive cells were present in the neonatal blood spot. Results: In 3 patients with ALL (25%) we reproducibly detected their leukemic markers (Ig/TCR n = 2; TEL/AML1 n = 1) in the Guthrie card. We did not find patient-specific molecular markers in any patient with AML. Conclusion: In the largest cohort examined so far we used identical approach for the backtracking of non-infant childhood ALL and AML. Our data suggest that either the prenatal origin of AML is less frequent or the load of pre-leukemic cells is significantly lower at birth in AML compared to ALL cases.