Study Of Microsatellite Instability On Chromosome 5 In Leukemia And MDS

Objective To study microsatellite instability on chromosome 5 in leukemias and MDS, and to investigate the possible genetic abnormalities that are associated with the pathogenesis and progression of leukemia and the significance of these abnormalities in leukemias.Methods We have chosen 82 leukemia and preleukemic MDS cases, including 43 patients with acute myelocytic leukemia, 28 with acute lymphocytic leukemia, 5 with chronic myelocytic leukemia and 6 with myelodysplastic syndrome. Matched bone marrow and oral mucosa cell DNA samples of these patients were examined using 5 microsatellite markers on chromosome 5,that is D5s346 and D5s409 near to 5q21 and D5s393,D5s399 and D5s476 on 5q31, for MSI and LOH by multi-PCR amplification, PAGE and argentine dye.Results In all patients with leukemias and MDS, microsatellite instability at at least one microsatellite marker were found in 55 out of 82 patients(67. 1%) and loss of het-erozygosity were in 25(30. 5%). There were 27(62. 8%) patients with MSI and 18 ones (18/43, 41. 9%)with LOH in AML, and MSI was detected at at least two microsatellite loci in 15 AML patients(34. 9%) ; 11 patients(39. 3%) with MSI and 4 ones(4/28, 14. 3%) with LOH in ALL; 2 MSI and 1 LOH in 5 patients with CML; 2 MSI and 1 LOH in 6 patients with MDS, respectively. Only one case in accelerated phase of CML shows MSI at 4 loci, that is, D5s346,D5s399,D5s476 and D5s393. MSI at D5s399 occurs in one MDS patient and another has LOH at loci D5s409,D5s393 and D5s399. These two patients both were RAEB-T. The frequency of LOH was much higher in myeloid malignancies than lymphoid ones. MSI was also seen in 29 of 50 AML and MDS cases (58. 0%) over the age of 60 years. We also found higher incidences of LOH at D5s346 in 5q21( 15/82, 18. 3%) and D5s476( 17/82,20. 7%) in 5q31. No abnomalities were detectes in normal controls and benigh hematopathies.Conclusions There was a high incidence of microsatellete instability at 5 microsatellite loci on chromosome 5. In addition, LOH was found more freqently in AML and malignant myeloid disorders than lymphoid leukemias, but there was no significance in frequencies of subtypes of these patients. MSI was seen at several markers in the accelerated phases of CML and MDS. These results meant that MSI in chromosome 5 might be a genetic event in the multi-sites/steps of the generation and progression of myeloid malignancies. LOH was inclined to occur in cases over the ages of 60 years, which might be caused bythe accumulation of DNA lesions resulted of defected mismatch repair genes and tumor suppressor genes. We also found that the markers D5s346 on 5q21 to 22 and D5s476 on 5q31 had higher chances of LOH than the other markers, thus these two chromosomal intervals may have TSGs such as APC,IRF-1 gene associated with leukmias that played a role in the pathogenesis and progression of leukemias and preleukemic MDS. Microsatellite technique based on multi-PCR is a valuable method in detecting minimal deletion and ge-nomic instability.