Loss of heterozygosity and heterogeneity of its appearance and persisting in the course of acute myeloid leukemia and myelodysplastic syndromes.

Screening for loss of heterozygosity (LOH) of the panel of 18 highly polymorphic microsatellite markers, especially from the region 11p15, was carried out on 154 samples from 26 patients with acute myeloid leukemia and eight with myelodysplastic syndromes (MDS). LOH was detected at the majority (72%) of the loci tested: 47% of informative patients displayed LOH for at least one of the microsatellite locus from the region 11p15 and 23.5% of patients displayed LOH among the other markers tested within the study. A longitudinal follow-up of patients showed a remarkable heterogeneity of LOH appearance and its persistance during the course of the disease suggesting an intratumor clonal heterogeneity, or alternatively, presence of LOH in more than one cell clone. The data revealed two regions of high loss of one allele in 11p15.5, defined by markers D11S1363 and D11S1338, indicating that LOH at the subtelomeric region of the short arm of chromosome 11 is a much common event in hematological malignancies than it was previously reported.

Detailed monitoring of hematopoietic chimerism in a child treated by adoptive immunotherapy for high risk of relapse after BMT for acute myeloid leukemia.

We report a case of a 13-year-old boy who was transplanted for relapse of acute myeloid leukemia (AML). A detailed study of hematopoietic chimerism was performed using polymerase chain reaction (PCR) of variable number of tandem repeats (VNTR) at very short time intervals. We used discontinuation of post-transplant immunosuppression and donor lymphocyte infusions (DLI) in order to prevent leukemia relapse that was indicated by a progressive increase in autologous hematopoiesis. Despite the fact that the boy relapsed 10 months after BMT, we could see a significant influence of adoptive immunotherapy on the mixed chimerism status during the post-transplant period.

Prediction and reversion of post-transplant relapse in patients with chronic myeloid leukemia using mixed chimerism and residual disease detection and adoptive immunotherapy.

In the prospective study, we examined hematopoietic mixed chimerism (using polymerase chain reaction (PCR) of variable number of tandem repeat-VNTR sequences) and minimal residual disease (MRD) status (using qualitative and in the case of positivity quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for the BCR/ABL fusion mRNA) in serial peripheral blood samples taken from 25 patients after bone marrow transplantation (BMT) for chronic myeloid leukemia (CML). Increasing mixed chimerism in correlation with increasing signal of MRD was detected in 10 patients. In two patients mixed chimera status and BCR/ABL rearrangement led to hematologic relapse, in five patients molecular relapse was followed by reappearance of Ph chromosome and three patients developed molecular relapse only. Adoptive immunotherapy-donor lymphocyte infusion (DLI), interferon (INF) and discontinuation of post-transplant immunosupression-separately or in different combinations was used in nine patients with molecular, cytogenetic or hematologic relapse of CML. The results demonstrate that significant response at the molecular level can be achieved for a majority of CML patients and that using of all forms of adoptive immunotherapy controlled by MC and MRD is more efficient in patients treated in early molecular relapse-with minimal disease burdens.

[DNA polymorphism, allogenic bone marrow transplantation and peripheral cell chimerism]. / DNA polymorfismy, alogenní transplantace kostní drene a periferní bunecný chimérismus.

BACKGROUND: Bone marrow transplantation or transplantation of peripheral stem cells is an effective treatment of a number of diseases. Its increasing success and expanding use in associated with the development of molecular diagnostic methods which enable to follow up the graft from its engraftment in a recipient and then during the whole posttransplantation period at the level extremely small numbers of cells. METHODS AND RESULTS: In peripheral blood of patients, genotypes of the following loci were examined by polymerase chain reaction (PCR): APOB, COL2A1, D17S20, D1S80, HVR/1G, SRY and AMXY. Technique of restriction analysis was used for loci DXYS20 and DXYS75. 1. The first signs of donor bone marrow activity were observed in 50% of patients already at the beginning of the second week after transplantation, while in the second half of patients increasing number of donor cells in peripheral blood was noticed in the second and third week. 2. Engraftment with full and permanent substitution of own bone marrow without presence of recipients cells in peripheral blood--complete chimerism--was achieved only in a part of patients (cca 50%). 3. Peripheral blood of other patients did not contain only donor cells but also recipients cells--mixed chimerism. With regard to its onset, the authors have divided mixed chimerism into early and late, taking into account that some patients can develop both types. In patients under study, early chimerism was found more frequently, which apparently resulted from a shorter period of observation of lately transplanted patients. 4. In cases of oncohaematologic patients, which allowed to study specifically the presence of a pathologic clone, the follow-up of chimerism enabled to distinguish between relapse of the original disease and "biologic" recovery--resurrection of original disease-free haematopoiesis. 5. Regression of mixed chimerism was supposed to be the result of treatment focused at the original disease (CML), in some patients, however, it was a spontaneous process. CONCLUSIONS: Follow-up of cellular chimerism in transplanted patients by means of molecular genetic methods provides substantial information about patient's shape which can be utilized it is necessary to decide on treatment procedures. For this reason it is desirable that examination of chimerism by molecular methods should form integral part of care of these patients.