Clinical significance of WT1 gene expression in peripheral blood cells and bone marrow cells of childhood leukemia

Objective To set up a simple, quick and accurate method for monitoring minimal residual disease (MRD) of leukemia, the clinical significance of WT1 gene expression in peripheral blood (PB) cells was compared with that in bone marrow (BM) cells from children with the acute leukemia (AL). Methods Thirty-four children with AL were selected in this study, including 23 acute lymphoblastic leukemia (ALL) and 11 acute myeloid leukemia (AML). Normal PB cells from 8 healthy children and BM cells from 8 non-hematological disease patients were used as the negative control and K562 cells as the positive control. Relative levels of WT1 gene expression in PB and BM mononuclear cells from 34 AL were dynamically detected by using the nested reverse transcriptase-polymerase chain reaction (RT-PCR), and analyzed quantitatively with GQS-960 image processing system software. The WT1/β-actin ratio was calculated. Results (1) WT1 gene expression showed 0.784±0.311 in BM cells of 27 patients with recently diagnosis, and 0.734±0.295 in PB cells of 26 cases. There was no difference of the WT1 gene expression(P>0.05). (2) Twenty-six out of 32 cases with AL achieved complete remission (CR) after chemotherapy, including 20 cases with WT1 positive expression in BM and PB, 6 cases with WT1 negative expression. The CR rate showed no difference. (3) Relative levels of WT1 gene expression in PB and BM markedly decreased after CR, 12 of 20 cases with WT1+ in BM changed to negative expression of WT1 gene. Eight cases still lasted positive (0.376±0.162 ). Fifteen of 20 cases with WT1+ in PB changed to negative expression, 8 cases still lasted positive (0.229±0.105 ). Six NR patients showed continued positive expression of WT1 gene (0.912±0.241 ). (4) Eighteen patients with WT1+ at the diagnosis were followed up from 6 to 24 months. Five out of 8 cases of WT1+ in BM relapsed, 3 out of 10 cases WT1- relapsed, which showed no market difference. While 5 cases with WT1+ in PB were all relapse, 3 out of 13 cases with WT1- relapsed, which showed significant difference (P=0.006 5). Conclusion The dynamic analysis of WT1 gene expression in children with AL could be used to monitor MRD and predict early relapse. WT1 gene expression detected in PB cells of MRD seems to be more specific and convenient than that detected in BM cells. Key words: Leukemia; Neoplasm residual; Oncogenes; Gene expression; Polymerase chain reaction