Presence of clone-specific markers at birth in children with acute lymphoblastic leukaemia

Abstract

Recent studies have suggested that development of childhood acute lymphoblastic leukaemia may often be initiated in utero. To provide further evidence of an prenatal origin of childhood leukaemia, we conducted a molecular biological investigation of nine children with B-precursor acute lymphoblastic leukaemia carrying the chromosomal translocation t(12;21), the most common subtype of all childhood acute lymphoblastic leukaemia. Specifically, for each child we identified the non-constitutive chromosomal sequences made up by the t(12;21) fusion gene. From these, leukaemia clone-specific DNA primers were constructed and applied in nested polymerase chain reaction analyses of DNA extracted from the patients' Guthrie cards obtained at birth. Leukaemia clone-specific fusion gene regions were demonstrated in Guthrie card DNA of three patients, age 2 years 11 months, 3 years 4 months, and 5 years 8 months at leukaemia diagnosis. Our findings are consistent with previous observations, and thus provide further evidence that the development of t(12;21) B-precursor acute lymphoblastic leukaemia may be initiated in utero. Review of the current literature moreover indicates that age at leukaemia may be inversely correlated with the burden of cells with leukaemia clonal markers, i.e. leukaemia predisposed cells at birth, and that certain types of childhood acute lymphoblastic leukaemia develop as a multiple step process involving both pre- and postnatal genetic events.

Figure 1

(A) Demonstrates the three translocation positive samples run on a 3% agarose gel electrophoresis. M: Molecular size marker pBR 327/Hae III. GC: DNA extract from the patient's Guthrie card. NTC: Non-template control. Sizes of the PCR products were: (Patient 1) 242/190 bp, (Patient 3) 183 bp and (Patient 8) 166 bp. The two fragment sizes in Patient 1, is due to inefficient nesting of one of the second round PCR primers. The identities were verified by direct sequence analysis. (B) The three patients individual chromosomal fusion regions are demonstrated. The arrows indicate the PCR primers used in the nested PCR reactions for the detection of the fusion gene (primer 1 followed by primer 2). The vertical line/box shows the site of fusion gene and the box demonstrates the base pairs introduced by the fusion gene event.