Test for cryopreservation efficiency of human acute myelogenous leukaemia cells relevant to clinical requirements

Thymidine Phosphorylase: A Possible Marker of Cell Maturation in Acute Myeloid Leukaemia

Thymidine Phosphorylase activity has been measured in two populations of human Acute Myeloid Leukaemia cells (AML) and in normal human macrophages. During short-term culture in vitro of AML cells the activity of this enzyme increases progressively and approaches that of normal non-dividing macrophages at a time when the leukaemia cells in culture show evidence of maturation as assayed by functional, enzymatic and morphological criteria. It is suggested that the level of Thymidine Phosphorylase activity may be a marker of maturation in AML.

A comparison of the effect of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors simvastatin, lovastatin and pravastatin on leukaemic and normal bone marrow progenitors

Simvastatin is an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and also selectively inhibits the growth of leukaemic progenitor cells. The antileukaemic action of simvastatin was compared in vitro with that of lovastatin and pravastatin, chemically related compounds which are also competitive inhibitors of HMG-CoA reductase. After 18 hours incubation with 2.5-20 microM of inhibitor, no effect was observed by any of the compounds on the subsequent clonogenic growth of normal bone marrow (BM) progenitor cells from 4 donors and BM cells from one patient in remission. However, simvastatin and lovastatin produced inhibition of acute myeloid leukaemia (AML) progenitor cell growth of between 25% and 100% in 5 populations tested (4 primary AMLs and the HL60 cell line). Pravastatin showed similar growth inhibitory effects to simvastatin and lovastatin in 2 out of 3 primary AMLs but was less active against one primary AML cell population and HL60 cells. These results indicate that, in addition to simvastatin, lovastatin and pravastatin are also selective inhibitors of leukaemic cell growth, however simvastatin was chosen for clinical trial in patients with leukaemia.

Expression of immunological markers on leukemic cells before and after cryopreservation and thawing

We have studied the effects of cryopreservation on the viability and on the expression of surface antigens of acute leukemia cells. Marrow samples were obtained at initial diagnosis from 89 patients with acute myeloid leukemia (AML), acute undifferentiated leukemia (AUL), and acute lymphoid leukemia (ALL). In AML, the mean viability was greater than 90% in the types M1, M4, and M5 of the French-American-British classification, 79% in M2, and 3% in M3 types. The viability was 74% in AUL. In ALL, the viability was 95% for pre-B leukemias, but only 2% in T-cell leukemias. The expression of myeloid antigens was studied before and after freezing and thawing using three monoclonal antibodies (NHL30.5, against poorly differentiated granulocytic leukemias, VIMC6 against differentiated granulocytic leukemias and granulocytes; and UCHM1 or CRIS-6, against monocytic leukemias and monocytes). The percentage of cells stained by NHL30.5 and UCHM1 or CRIS-6 was very similar before and after cryopreservation. For VIMC6, the mean staining after cryopreservation was 60% of the initial one. In pre-B ALL, the stainings by anti common ALL antigen before and after cryopreservation were also very similar. We conclude that leukemic cryopreserved cells are suitable for immunologic studies. The recovery is, however, very low in promyelocytic AML and T-cell ALL.

2nd Gordon Hamilton Fairley lecture. Need for new approaches to the treatment of patients in clinical remission, with special reference to acute myeloid leukaemia

A serious limitation of chemotherapy for acute myeloid leukaemia (AML), Hodgkins disease and some classes of breast cancer is that, even when clinically evident disease responds well, the same chemotherapy when given during remission does not affect the rate of relapse after chemotherapeutic or surgical ablation of the primary disease. This cannot, in general, be caused by genetic adaptation of the residual cancer cells which renders them resistant to specific drugs, because after relapse further remissions can be obtained with the same drugs that were ineffective by chronic administration in prolonging remission. The resistance of the residual cells may arise from mechanisms such as inaccessibility for anatomical or other reasons, or because of a change in metabolic state which causes these cells temporarily to cease division, when they cannot be harmed by cycle-dependent drugs and repair damage sustained from cycle-independent drugs. Limited differentiation has been shown capable of reversal and this may be a mechanism which leads to quiescence and associated "resistance", particularly in the case of AML. Where such resistance occurs treatment during remission-or as an adjuvant to surgery and radiotherapy-may have to rely on mechanisms which are independent of cellular proliferation such as processes associated with graft-versus-host-disease or the induction of terminal differentiation. A model for studying the nature of resistance of residual cancer and for testing treatments that might be active against cancer cells in this state may be dormant metastases. The latter are malignant cells which appear to be in peaceful co-existence with their host and which in experimental systems have been induced to grow into lethal metastases by perturbation of the host by surgical trauma, by hormonal manipulation or by immunosuppression.

Maturation of human peripheral blood leukemic cells in short-term culture

This work is a continuation of earlier studies in this laboratory (Palú et al. 1979) in which two populations of cryopreserved acute myelogenous leukaemia (AML) cells were shown to undergo progressive maturation in vitro. Twelve other populations of AML cells have since been studied and three distinct patterns of in vitro behaviour have been observed: 1. Cells which did not mature. 2. Cells which matured to the polymorph series and 3. Cells which matured to the macrophage series. Six populations of AML cells were studied both before and after cryopreservation to demonstrate that exposure to the cryopreservative agent dimethylsulphoxide (DMSO) does not influence the patterns of maturation observed. The effect of thioproline and prostaglandins A1 and A2 on maturation was also studied. It is too early to say whether any correlation between the prognosis of the AML patients and the maturation pattern of their AML cells can be established.

Failure to detect autologous antibodies in the remission sera of patients with AML: complications introduced by the presence of rheumatoid factor

Sera were collected from patients with acute myelogenous leukaemia (AML) at various times during remission induced by chemotherapy, but after cessation of all immunosupressive treatment. These sera were tested, by a sensitive assay using radio-labelled antiglobulin binding, for the presence of antibodies which bound to the surface of autologous AML cells. The cell populations examined were chosen on the basis that they proliferated in short-term culture, did not bind anti-Ig reagents directly, and that more than 80% of the cells did not carry detectable Fc receptors. With 8/9 patients studied, no specific antibodies of the IgG or IgM class could be detected in serum samples taken during remission. IgG and IgM antibodies from the remission sera of one patient were found be bind to autologous leukaemic cells, but this was found to be due to the presence of rheumatoid factor (RF) and removal of the RF activity abolished this binding. This study has, like others, failed to detect autologous antibodies, in remission sera, that are directed against membrane components of AML cells.