Biological and Clinical Significance of Clonogenic Assays in Patients with Myelodysplastic Syndromes

Abstract

Biological and clinical significance of growth pattern of hematopoietic progenitors were investigated in 117 patients with primary myelodysplastic syndromes (MDSs) at referral. Abnormal (i.e., "leukemic" or absent) growth of GM colonies (CFU-GM) and GM clusters was found in 47% of patients with "advanced" MDS (RAEB, RAEB-t, and CMML) and in 15% of "low-risk" (RA/RARS) patients. In vitro erythropoiesis was decreased in most of the patients, with significantly lower number of BFU-E in "advanced" MDS than in RA/RARS patients. Megakaryocyte progenitors (CFU-MK) were very low or absent in almost all the patients, regardless of the FAB type. Significant correlation was demonstrated between the number of BFU-E and hemoglobin concentration and between number of CFU-MK and platelet count. Growth capacity of GM progenitors appears to be in proportion to "myeloproliferative" capacity of the malignant clone. T-cell depletion had no influence on growth capacity of hematopoietic progenitors, nor did colony growth respond in a dose-dependent manner to different concentrations of LCM. Growth capacity of MDS hematopoietic progenitors was independent of Bournemouth score, of the presence and type of cytogenetic abnormality, and of the expression of CD95 and caspase-3 antigens on bone marrow cells. However, in patients with "abnormal" growth of GM progenitors, CD34 antigen expression was significantly higher than in patients with "normal" growth. "Abnormal" GM growth was found to be independently predictive regarding the survival and the risk for AML development. In contrast, the prognostic value of erythroid and megakaryocyte cultures was found to be limited.

Leukemic Cluster Growth in Culture Is an Independent Risk Factor for Acute Myeloid Leukemia and Short Survival in Patients with Myelodysplastic Syndrome

“…Our results are in line with numerous early [26,28] and some more recent [31,[35][36][37]] studies on the prognostic value of clonogenic assays in patients with MDS. The classification of MDS has undergone fundamental changes in recent years: RAEB-t and chronic myelomonocytic leukemia, two former FAB entities where leukemic growth was typically found, are no longer classified as MDS.…”

“…Lower numbers of normal colonies and grossly abnormal erythroid colonies [24] were found to be typical of MDS, and the growth of leukemic clusters in culture soon became an acknowledged sign of treatment resistance in AML [25] and of impending leukemic transformation in MDS [26,27] , particularly in patients with autocrine growth factor-independent leukemic proliferation [28,29] . However, as hematopoietic precursor cell cultures proved difficult to standardize [30] they were gradually replaced by other techniques, and only limited data are available on the impact of the colony-forming assay in the contemporary management of MDS [31] .…”

SALL4, a novel oncogene, is constitutively expressed in human acute myeloid leukemia (AML) and induces AML in transgenic mice

“…Statistically significant increased myeloid (CFU-GM in SALL4B transgenic mice: 53.6 Ϯ 10.3 [n ϭ 13] vs WT: 38.1 Ϯ 3.1 [n ϭ 8]; P ϭ .002) and decreased erythroid (BFU-E in SALL4B transgenic mice: 7.8 Ϯ 3.8 [n ϭ 13] vs WT: 14.1 Ϯ 2.7 [n ϭ 8]; P ϭ .001) colony populations (Figure 5Cii), however, were found in SALL4B transgenic mouse CFUs compared with those of WT controls, as has been reported in human MDS patients and other MDS mouse models. [31][32][33][34][35] These observations suggest that the defect in SALL4B transgenic mice lies at the stem cell/progenitor level affecting hematopoietic differentiation.…”

Distinctive gene expression profiles of CD34 cells from patients with myelodysplastic syndrome characterized by specific chromosomal abnormalities

“…[6][7][8][9] Monosomy 7 is associated with refractory and often severe pancytopenia and frequent progression to acute myeloid leukemia. [9][10][11] In one large retrospective analysis, patients with chromosome 7 abnormalities had a uniformly fatal course and all evolved to acute leukemia 6 ; chromosome 7 abnormalities therefore are an indicator of a poor prognosis in the International Scoring System. 6 Monosomy 7 commonly occurs as a late evolution event in aplastic anemia and, again, most patients succumb to refractory cytopenias or to leukemic transformation.…”

“…31 The close correlation of cytogenetic abnormalities with patterns of dysplastic marrow morphology, ineffective hematopoiesis, and leukemic transformation strongly suggests their pathophysiologic roles in marrow failure and leukemogenesis. 11,32,33 As early hematopoietic cells are readily identified and isolated based on the presence of the CD34 antigen, we examined purified populations of hematopoietic stem and progenitor cells using DNA microarrays, which allow assessment in minimally manipulated cells of the expression levels of thousands of genes simultaneously. Because CD34 cells are infrequent even in normal BM and particularly so in many MDS patients, we applied the accepted modifications of sample pooling and RNA amplification; these methods allow comparison of gene expression patterns between standard protocols with single-donor and pooled RNA samples and a new T7-linear amplification protocol when RNA quantities are insufficient.…”