Cytogenetic and Southern blot analysis to demonstrate clonality and to estimate prognosis in patients with myelodysplastic syndromes

Abstract

We examined the bone marrow of 109 patients with myelodysplastic syndrome (MDS) at the time of diagnosis and during the course of the disease by means of Southern blot analysis and/or cytogenetic studies to detect and evaluate clonal markers, their implications for the prognosis of the disease, and the response to treatment. The patients either were enrolled in an EORTC study and received low-dose Ara-C with (n=31) or without (n=21) growth factors, according to the study protocol, or were treated supportively (only one patient received regular chemotherapy for concomitant lymphoma). Full or at least partial remission was achieved by 34% of the treated patients (n=54). In 57% (53 of 93) of all patients a clonal marker of either kind was detected by Southern blot analysis and/or cytogenetic examination. Clonal chromosomal aberrations were found in 45% (35 of 77) of the cases examined at diagnosis, with solitary del(5q) aberrations occurring in 10% of the cases and complex aberrations in 18%, trisomy 8 or monosomy 7 being a frequent finding. Of all patients, 49% (28 of 57) were characterized by one or more gene rearrangements (e.g., Ig-JH, TcR-beta, M-bcr, GM-CSF, G-CSF, or IL-3) at diagnosis. In five of 21 cases (24%) studied in hematological remission of the disease chromosomal aberrations were still detectable, and in seven of 23 (30%) a gene rearrangement persisted. We also found six cases with multiple clones exhibiting different susceptibilities to treatment and thereby indicating the oligoclonal character of this disease. Clinical evaluation revealed that the prognosis of the respective patients was directly related to the particular clonal markers detected at diagnosis: Risk groups were subdivided according to the karyotypes, with a solitary del(5q) aberration meaning a favorable, a normal karyotype an intermediate, solitary aberrations without del(5q) a poor, and complex karyotypes a very poor prognosis. We showed that densitometry helps to increase the sensitivity of Southern blot analysis by quantifying the amount of altered DNA, which often increases shortly before or at progression of MDS. Overall, there was a high level of concordance of both clonality examinations with the clinical course of the disease and the response rate. Therefore, we recommend cytogenetic studies and Southern blot analysis to detect clonal markers at diagnosis of MDS, to detect oligoclonality and clonal evolution, or to quantify the amount of clonal DNA, which appears to be a sensitive tool for evaluating the prognosis and response to therapy in MDS.