In vitro growth in acute myeloblastic leukemia: clinico-biological correlations

In the present review we analyse the current knowledge about the growth properties of AML progenitor cells and their relationship with other clinico-biological characteristics of the disease. Leukaemic colony forming unit L-CFU is considered to be the clonogenic cell in AML and more immature than the blast cell population. Our studies have shown that in leukaemic hematopoiesis colony forming cells can exist among both cell fractions CD34+ and CD34-. Optimal "in vitro" proliferation of L-CFU is dependent upon the addition of exogenous growth factors. However, it has been observed that leukaemic progenitor cells frequently display a certain degree of autonomous proliferation. In order to quantify the "in vitro" behaviour of L-CFU, we have explored 3 parameters: 1) plating efficiency (PE); 2) autonomous growth (AG); and 3) autonomous proliferative index (API) which was calculated as AG divided by PE and we have correlated them with other clinico-biological data. According to the FAB classification we could observe that patients with M3 subtype showed an higher PE than other AML subgroups and a significantly lower API. Regarding CD34 expression we observed that AG was enhanced in CD34+ cases and also in those showing a higher rh123 elimination. In order to determine whether PE could condition clinical evolution, we analysed this parameter in a large series of patients but failed to demonstrate any relationship. By contrast, we observed that patients who displayed a higher API showed a shorter survival than patients with lower API (18% vs 48% surviving at 3 years). We have also shown that abnormalities in the CFU-GM growth pattern could be associated with risk the of relapse in AML patients; a switch from normal to abnormal "in vitro" growth should alert us. But for the assessment of the real value of these analyses sequential follow-up studies are mandatory. In summary, cell culture studies contribute not only to a better understanding of leukaemic hematopoiesis but may also contribute to better disease monitoring.

Factors that influence long-term hematopoietic function following autologous stem cell transplantation

The aim of the present study was to assess which factors influence hematopoietic function long term after transplantation. For this purpose, we have analyzed a series of 79 patients who underwent autologous transplantation. None of them received any further chemotherapy or radiotherapy after transplant. All patients were disease-free 1 year after autologous transplantation. Late impairment of hematopoietic function was defined as the presence of non-transient peripheral blood cytopenias, detected 6 and 12 months after autografting. Before transplantation, 38.7% of patients showed peripheral blood cytopenias. Six and 12 months after transplantation, cytopenias presented in 44.2% and 42.4% of patients, respectively. Cases displaying cytopenias 6 months after transplantation had received a significantly lower dose of CFU-GM and CD34+ cells than patients without cytopenias (P = 0.012 and P = 0.04, respectively). The same correlation, with even higher statistical significance, was observed 12 months after transplant (P = 0.007 and P = 0.005). Alkylating agents and radiotherapy administered prior to transplantation and age did not seem to influence the presence of permanent cytopenias. The incidence did not vary significantly according to the stem cell source (bone marrow or peripheral blood). The number of CFU-GM and CD34+ cells infused was the most important factor for maintenance of adequate hematopoiesis.

Haematopoietic damage persists 1 year after autologous peripheral blood stem cell transplantation

In the present study we have used cell culture assays in order to assess the damage in the haematopoietic system 1 year after peripheral blood stem cell transplantation (PBSCT), and to establish at what level, haematopoietic progenitor cells (HPC) or stroma, this damage occurs. Thirty-one patients, nine breast cancer (BC), 17 non-Hodgkin lymphoma (NHL) and five Hodgkin disease (HD), who had received autologous PBSCT were included. Forty-eight normal subjects who had given informed consent were used as controls. Results were also compared with a matched group of patients (25 cases) prior to PBSCT. Progenitor cells were analysed using CFU-GM and plastic adherent delta (Pdelta) assays. Long-term bone marrow cultures (LTBMC) in one and two stages were established. One year after transplant both the number of committed progenitor cells and the CFU-GM production in LTBMC were significantly reduced in the three groups of patients when compared with controls (P < 0.05 or P < 0.01). Two-stage LTBMC experiments showed that the impairment in CFU-GM production was due to damage in both patients' stroma and haematopoietic progenitor cells (HPC). All patients, except those with HD, showed a decreased stromal layer confluence (P < 0.05), with significant differences in cell composition as compared to normal bone marrow (P = 0.001). When all these variables were compared with pretransplant results, we observed that stroma formation was significantly lower after PBSCT (P < 0.05), while the number of progenitor cells analysed by the Pdelta assay was significantly increased (P < 0.05). We can conclude that even 1 year after PBSCT, both the committed HPC and BM stroma remain damaged.

In vitro growth in acute myeloblastic leukaemia: relationship with other clinico-biological characteristics of the disease

The in vitro growth characteristics of a large series of acute myeloid leukaemia (AML) patients and their relationship with other clinical and biological disease characteristics were analysed. Patients with AML were studied, 181 with de novo AML and 45 with secondary AML (24 myelodysplastic syndrome, sAML-MDS, 21 myeloproliferative disorder, sAML-MPD). Leukaemic colony forming units (L-CFU) were assayed by plating peripheral blood (PB) blast cells in methyl-cellulose and using LCM-PHA as stimulant. In each case parallel cultures were made with and without stimulating factors. Plating efficiency (PE) was defined as the number of clusters plus colonies/10(5) cells plated. Autonomous growth (AG) was the number of colonies plus clusters growing without stimulant. The autonomous proliferative index (API) was calculated as the number of clusters + colonies without stimulating factor divided by the number of clusters + colonies with stimulating factor. No significant differences in the PE between de novo and secondary AML were found. Autonomous growth was significantly higher in sAML-MPD. The FAB subtype M3 leukaemias displayed a significantly greater PE and a significantly lower API when compared with the other FAB subgroups (P=0.0002). Upon analysing the relationship with the immunophenotype, only CD33 expression showed a significant relationship with the in vitro growth pattern; CD33+ cases displayed a higher PE (P=0.0002) and AG (P=0.0003) than CD33- cases. When patients were grouped according to the level of rh123 efflux (MDR1) it was observed that cases with >30% elimination showed a higher AG and API than those with <30% (P=0.03). Finally we found that patients with higher API (>0.05) displayed a significantly shorter overall survival as compared with patients with API<0.05 (P=0.04). The in vitro study properties of clonogenic cells produces relevant clinical information of leukaemic cell biology in AML patients.

The value of cell cultures for the diagnosis of mixed myelodysplastic/myeloproliferative disorders

BACKGROUND AND OBJECTIVE

Myelodysplastic syndromes (MDS) are a group of disorders characterized by dyshematopolesis in bone marrow (BM) and peripheral blood (PB) cytopenias. In recent years particular attention has been paid to myeloproliferative disorders with dysplastic features or myelodysplastic syndromes that evolve into a myeloproliferative disorder. The present study was designed to analyze patients with MDS but with a normal or increased colony forming capacity, in order to see whether or not cell cultures could contribute to the diagnosis of intermediate MDS-MPD conditions.

DESIGN AND METHODS

A total of 80 patients diagnosed as having MDS were included in the study. CFU-GM assay was performed by plating 1 x 10(5) mononuclear cells/mL in IMDM and 0.9% methyl-cellulose containing 10% PHA-LCM. In all cases cultures were run in parallel without PHA-LCM to assess autonomous growth. Cultures were incubated at 37 degrees C in a fully humidified atmosphere with 5% CO2 and scored at day 14. Cytogenetic analysis was performed according to standard procedures. Short-term cultures of 24 and/or 48 hours were used.

RESULTS

Twenty-two patients out of the 80 MDS cases included in the study showed a normal or increased cell growth pattern. Among these 22 patients, eight were diagnosed as suffering from chronic myelomonocytic leukemia (CMML) according to the FAB criteria and were excluded from the present analysis. The remaining 14 cases, which constitute the body of this study, displayed an increased number of clusters and/or colonies, with an altered cluster/colony ratio (anomalous growth) in 10 cases. Autonomous colony formation was present in five of these 14 cases and autonomous cluster growth was seen in all but three of them. In addition, one patient showed endogenous BFU-E growth. Morphological diagnoses were then revised due to this aberrant colony growth pattern: based on actual criteria, 3 patients could have been considered as having a-CML (atypical chronic myeloid leukemia). Another 6 cases evolved to a more proliferative disorder: 5 to CMML, and one to a-CML. Interestingly, in 3 of these 6 patients the evolution took place concomitantly with an infectious episode. In one additional patient the platelet count increased up to 1000 x 10(9)/L and required treatment with hydroxyurea.

INTERPRETATION AND CONCLUSIONS

Our results show that intermediate MDS-MPD cases are relatively common and that in vitro characteristics, i.e. high clonogenic capacity with a high cluster/colony ratio and scanty autonomous growth, in patients showing myelodysplastic features could contribute to an early diagnosis in these cases. It is possible that in some cases an infectious episode, through higher cytokine secretion, contributes to the development of these disorders.