Common leukemia- and lymphoma-associated genetic aberrations in healthy individuals

Abstract

Leukemia- and lymphoma-associated (LLA) chromosomal rearrangements are critical in the process of tumorigenesis. These genetic alterations are also important biological markers in the diagnosis, prognosis, and treatment of hematopoietic malignant diseases. To detect the presence or absence of these genetic alterations in healthy individuals, sensitive nested RT-PCR analyses were performed on a large number of peripheral blood samples for selected markers including MLL partial tandem duplications (PTDs), BCR-ABL p190, BCR-ABL p210, MLL-AF4, AML1-ETO, PML-RARA, and CBFB-MYH11. Using nested RT-PCR, the presence of all of these selected markers was detected in healthy individuals at various prevalence rates. No correlation was observed between incidence and age except for BCR-ABL p210 fusion, the incidence of which rises with increasing age. In addition, nested RT-PCR was performed on a large cohort of umbilical cord blood samples for MLL PTD, BCR-ABL p190 and BCR-ABL p210. The results demonstrated the presence of these aberrations in cord blood from healthy neonates. To our knowledge, the presence of PML-RARA and CBFB-MYH11 in healthy individuals has not been previously described. The present study provides further evidence for the presence of LLA genetic alterations in healthy individuals and suggests that these mutations are not themselves sufficient for malignant transformation.

Figure 1

Transcription of MLL PTDs in peripheral blood samples from healthy individuals. Upper panel, MLL PTD transcription. Lanes 1 and 8 show e11/e3 fusion, and lane 6 shows e9/e3 fusion. Lower panel, Corresponding internal positive controls using primers for the abl gene. B, blank; M, marker.

Figure 2

MLL PTDs in peripheral blood samples from healthy individuals at the genomic level. Seminested PCR using genomic DNA from individuals positive for MLL PTD transcripts. B, blank; positive control from a patient with AML.

Figure 3

Transcription of MLL PTDs in cord blood samples from healthy newborns. Upper panel, MLL PTD transcripts. Lower panel, ABL transcripts in the corresponding samples are shown as internal positive controls. M, marker; B, blank.

Figure 4

Results of K562 cell dilution experiment. Cell line K562 was used to dilute cultured fibroblast cells. A: Results of primary PCR using A <–> B primer set for BCR-ABL p210. Dilution ratios are shown. B: Results of nested PCR using the internal C <–>D primer set. C: β-actin. F, cultured fibroblast cells; H₂O, blank control; K-RT, K562 RNA control reverse transcription without adding reverse transcriptase (RT); M, 100-bp DNA ladder.

Figure 5

Transcripts of PML-RARA in peripheral blood samples from healthy individuals. Lanes 1 to 4, healthy individuals. Individuals 2, 3, and 4 are positive for PML-RARA. M, marker; L form, long form, 427-bp PML-RARA chimeric transcript; S form, short form, 393-bp PML-RARA chimeric transcript. Lane 5, minus RT control; lane 6, blank.