Acute leukemia in adults

Clonogenic growth patterns correlate with chemotherapy response in acute myeloid leukaemia

Cytosine arabinoside and anthracycline-containing regimens induce remission in upwards of 60% of previously untreated patients with adult acute myeloid leukaemia (AML). Despite this, in addition to primary drug resistance, the majority of these patients relapse. Reliable methods for uniformly recognising these two subgroups at presentation do not exist and therefore a further attempt has been made to relate in vitro toxicity, using a clonogenic assay, to clinical outcome. In 10 normal controls and 12 chemotherapy naïve cases, mononuclear cells harvested by density gradient separation were re-suspended at a concentration of 2 x 10(5)/ml and quadruplicates of 250 microl per well cultured in methycellulose containing foetal calf serum and phytohaemagglutinin stimulated leucocyte conditioned medium. Cell kill was determined for cytosine arabinoside, daunorubicin and etoposide either singly or in combination using both a pulsed and continuous exposure. Aggregates were scored after seven days and three distinct patterns recognised. The patients all received the same drugs in a standard protocol and achievement of complete remission correlated with growth pattern. The survival of normal marrow colony-forming cells or GM-CFUc and the leukemic equivalent designated L-CFUc were assessed and a sensitivity index (SI) determined as a ratio of these two values in which more reproducible results were found when the drug was continuously present. It is concluded that the microculture technique is feasible and clearly demonstrates chemotherapy effect but no correlation was demonstrated with clinical outcome. This is a negative pilot study and, as a means of recognising drug sensitivity or resistance, should be discarded in favour of currently available molecular techniques.

Radioimmunotherapy of CD22-expressing Daudi tumors in nude mice with a 90Y-labeled anti-CD22 monoclonal antibody

A study was undertaken to investigate the efficacy of a high affinity, rapidly internalizing anti-CD22 monoclonal antibody for selectively delivering high-energy (90)Y radioactivity to B lymphoma cells in vivo. The antibody, RFB4, was readily labeled with (90)Y using the highly stable chelate, 1B4M-diethylenetriaminepentaacetic acid. Labeled RFB4 selectively bound to the CD22(+) Burkitt's lymphoma cell line Daudi, but not to CD22(-) control cells in vitro as compared with a control antibody, and was more significantly bound (P = 0.03) to Daudi solid tumors growing in athymic nude mice. Biodistribution data correlated well with the antitumor effect. The therapeutic effect of (90)Y-labeled anti-CD22 (Y22) was dose-dependent, irreversible, and the best results were achieved in mice receiving a single i.p. dose of 196 microCi. These mice displayed a significantly better (P < 0.01) antitumor response than control mice and survived >200 days with no evidence of tumor. Histology studies showed no significant injury to kidney, liver, or small intestine. Importantly, tumor-bearing mice treated with Y22 had no radiologic bone marrow damage compared with tumor-bearing mice treated with the control-labeled antibody arguing that the presence of CD22(+) tumor protected mice from bone marrow damage. When anti-CD22 radioimmunotherapy was compared to radioimmunotherapy with anti-CD19 and anti-CD45 antibodies, all three antibodies distributed significantly high levels of radioisotope to flank tumors in vivo compared with controls (P < 0.05), induced complete remission, and produced long-term, tumor-free survivors. These findings indicate that anti-CD22 radioimmunotherapy with Y22 is highly effective in vivo against CD22-expressing malignancies and may be a useful therapy for drug-refractory B cell leukemia patients.

Ethnicity and prognosis in acute myeloid leukemia

Ethnicity has been described as a prognostic factor in breast cancer and in childhood acute lymphocytic leukemia but not in adult acute myeloid leukemia (AML). We reviewed the records of 225 consecutive AML patients who were diagnosed and treated between 1983 and 1995. Data were collected concerning demographic factors, presenting clinical features, and treatment protocols. We categorized ethnicity as follows: European Jews, non-European Jews, and Arabs. We assessed the role of ethnicity controlling for other known prognostic factors on treatment outcome and survival in this population. Older age, high leukocyte count at diagnosis, and high-risk chromosomal aberrations were significantly associated with overall survival in univariate analysis. In multivariate analysis high leukocyte count and high-risk chromosomal aberrations exerted an independent negative effect on survival. European origin was associated with longer event-free survival in univariate analysis (P = 0.024) and longer overall (P < 0.01) and event-free (P < 0.01) survival but not with a higher remission rate in multivariate analysis. For AML patients who achieved remission after induction chemotherapy and survived its complications, European origin is an independent favorable prognostic factor for long-term remission and survival in Israel. These findings may reflect better socioeconomic status, social support, increased compliance with treatment protocols, or better psychological coping mechanisms with malignancy.

The roles of FLT3 in hematopoiesis and leukemia

FLT3 is a receptor tyrosine kinase expressed by immature hematopoietic cells and is important for the normal development of stem cells and the immune system. The ligand for FLT3 is expressed by marrow stromal cells and other cells and synergizes with other growth factors to stimulate proliferation of stem cells, progenitor cells, dendritic cells, and natural killer cells. Mutations of FLT3 have been detected in about 30% of patients with acute myelogenous leukemia and a small number of patients with acute lymphocytic leukemia or myelodysplastic syndrome. Patients with FLT3 mutations tend to have a poor prognosis. The mutations most often involve small tandem duplications of amino acids within the juxtamembrane domain of the receptor and result in constitutive tyrosine kinase activity. Expression of a mutant FLT3 receptor in murine marrow cells results in a lethal myeloproliferative syndrome and preliminary studies suggest that mutant FLT3 cooperates with other leukemia oncogenes to confer a more aggressive phenotype. Taken together, these results suggest that FLT3 is an attractive therapeutic target for kinase inhibitors or other approaches for patients with mutations of this gene.

Role of FLT3 in leukemia

FLT3 is the most frequently mutated gene in cases of acute myelogenous leukemia (AML). About 30 to 35% of patients have either internal tandem duplications (ITDs) in the juxtamembrane domain or mutations in the activating loop of FLT3. FLT3 mutations occur in a broad spectrum of FAB subtypes in adult and pediatric AML and are particularly common in acute promyelocytic leukemia (APL). FLT3 mutations confer a poor prognosis in most retrospective studies. The consequence of either FLT3-ITD or activating loop mutations, which occur predominantly at position D835, is constitutive activation of the tyrosine kinase; FLT3 mutants confer factor-independent growth to Ba/F3 and 32D cells and activate similar transduction pathways as the native receptor in response to ligand, including the STAT, RAS/mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3; kinase (PI3K)/AKT pathways. Injection of FLT3-ITD transformed cells, such as Ba/F3 or 32D, into syngeneic recipient mice results in a leukemia-like syndrome, and expression in primary murine bone marrow cells in a retroviral transduction assay results in a myeloproliferative disorder. Mutations that abrogate FLT3 kinase activity result in loss of transforming properties in these assays. Further, FLT3-selective inhibitors impair transformation of primary AML cells that harbor these mutations, and also inhibit FLT3 transformed hematopoietic cell lines, and leukemias induced by activated FLT3 mutants in murine models. Collectively, these data indicate that FLT3 may be a viable therapeutic target for treatment of AML.

Up-regulation of costimulatory/adhesion molecules by histone deacetylase inhibitors in acute myeloid leukemia cells

Histone deacetylase inhibitors (HDACIs) have been used to focus on the effects of inducing gene expression through the acetylation of histones which results in chromatin remodeling. The study explored whether HDACIs could induce the expression of costimulatory/adhesion molecules on acute myeloid leukemia (AML) cells, thereby effectively inducing tumor immunity. The expression of CD80, CD86, human leukocyte antigen (HLA)-DR, HLA-ABC, and intracellular adhesion molecule–1 (ICAM-1) was tested in human AML cell lines after the addition of HDACI, sodium butyrate (SB). Generally, increased expression of CD86 was observed by SB treatment in a majority of cell lines, and ICAM-1 was expressed in fewer cell lines. Essentially the same results were obtained using other HDACIs such as FR901228, trichostatin A, and trapoxin A. Quantitation of transcripts of CD86 accompanied with RNA synthesis inhibition assay and nuclear run-on assay revealed that SB up-regulates the CD86 expression transcriptionally. Furthermore, chromatin immunoprecipitation experiments showed that HDACI treatment caused remarkable acetylation on histone H3 and H4 at CD86 promoter chromatin in vivo. In 30 clinical AML samples, CD86 expression was significantly increased (P &lt; .001) by SB treatment, and the expression of HLA-DR and ICAM-1 was moderately increased (P &lt; .05) by SB treatment. Finally, the allogeneic mixed leukocyte reaction (allo-MLR) against HL60 cells pretreated with SB was enhanced 4-fold compared with allo-MLR obtained with non-treated HL60 cells. These results suggest that the immunotherapeutic use of HDACIs may become a novel tool for treatment of AML.

Up-regulation of costimulatory/adhesion molecules by histone deacetylase inhibitors in acute myeloid leukemia cells

Histone deacetylase inhibitors (HDACIs) have been used to focus on the effects of inducing gene expression through the acetylation of histones which results in chromatin remodeling. The study explored whether HDACIs could induce the expression of costimulatory/adhesion molecules on acute myeloid leukemia (AML) cells, thereby effectively inducing tumor immunity. The expression of CD80, CD86, human leukocyte antigen (HLA)-DR, HLA-ABC, and intracellular adhesion molecule–1 (ICAM-1) was tested in human AML cell lines after the addition of HDACI, sodium butyrate (SB). Generally, increased expression of CD86 was observed by SB treatment in a majority of cell lines, and ICAM-1 was expressed in fewer cell lines. Essentially the same results were obtained using other HDACIs such as FR901228, trichostatin A, and trapoxin A. Quantitation of transcripts of CD86 accompanied with RNA synthesis inhibition assay and nuclear run-on assay revealed that SB up-regulates the CD86 expression transcriptionally. Furthermore, chromatin immunoprecipitation experiments showed that HDACI treatment caused remarkable acetylation on histone H3 and H4 at CD86 promoter chromatin in vivo. In 30 clinical AML samples, CD86 expression was significantly increased (P < .001) by SB treatment, and the expression of HLA-DR and ICAM-1 was moderately increased (P < .05) by SB treatment. Finally, the allogeneic mixed leukocyte reaction (allo-MLR) against HL60 cells pretreated with SB was enhanced 4-fold compared with allo-MLR obtained with non-treated HL60 cells. These results suggest that the immunotherapeutic use of HDACIs may become a novel tool for treatment of AML.

In vitro drug resistance profiles of adult versus childhood acute lymphoblastic leukaemia

The difference in the current cure rates between adult and childhood acute lymphoblastic leukaemia (ALL) may be caused by differences in drug resistance. Earlier studies showed that in vitro cellular drug resistance is a strong independent adverse risk factor in childhood ALL. Knowledge about cellular drug resistance in adult ALL is still limited. The present study compared the in vitro drug resistance profiles of 23 adult ALL patients with that of 395 childhood ALL patients. The lymphoblasts were tested by the MTT assay. The group of adult ALL samples was significantly more resistant to cytosine arabinoside, L-asparaginase, daunorubicin, dexamethasone and prednisolone. The resistance ratio (RR) was highest for prednisolone (31.7-fold) followed by dexamethasone (6.9-fold), L-asparaginase (6. 1-fold), cytosine arabinoside (2.9-fold), daunorubicin (2.5-fold) and vincristine (2.2-fold). Lymphoblasts from adult patients were not more resistant to mercaptopurine, thioguanine, 4-HOO-ifosfamide, mitoxantrone and teniposide. There were no significant differences in drug resistance between adult T-cell (T-) ALL (n = 11) and adult common/pre-B-cell (B-) ALL (n = 10). Additionally, adult T-ALL did not differ from childhood T-ALL (n = 69). There were significant differences between adult common/pre-B-ALL and childhood common/pre-B-ALL (n = 310) for prednisolone (RR = 302, P = 0.008), dexamethasone (RR = 20.9, P = 0.017) and daunorubicin (RR = 2.7, P = 0.009). Lymphoblasts from adults proved to be relatively resistant to drugs commonly used in therapy. This might contribute to the difference in outcome between children and adults with ALL.

Rapid detection of BCR/ABL and PML/RARA using fluorescence in situ hybridization in cytospin preparations

Fluorescence in situ hybridization (FISH) is increasingly used as an adjunct to conventional cytogenetic analysis in the diagnosis of haematological malignancies and in monitoring minimal residual disease. FISH, however, is generally performed on slides prepared after short-term sample incubation and therefore, whilst faster than conventional cytogenetics, still requires a minimum of 2 days for a result to be obtained. A simplification of the FISH procedure is reported using uncultured cytospin preparations of bone marrow or peripheral blood for the rapid diagnosis of the BCR-ABL and PML-RARa gene rearrangements. It demonstrates that culturing has no effect on the ratio of normal to abnormal cells in the nondividing population. Data is presented from an analysis of 24 cases in whom unequivocal results were obtained in less than 12 h and in complete concordance with results obtained by conventional cytogenetics and/or interphase FISH.

Regulation of CD80/B7-1 and CD86/B7-2 molecule expression in human primary acute myeloid leukemia and their role in allogenic immune recognition

Clinical data and animal models afford evidence for anti-leukemia immunity in humans, but the interactions critical for blast cell recognition are unresolved. Expression of B7 molecules by antigen-presenting cells (APC) provides co-stimulatory signals to T lymphocytes via CD28 and CTLA-4 which prevent the induction of alloantigen-specific tolerance. Conversely, expression of CD40 ligand by stimulated T cells activates APC via CD40. In human hematological B cell malignancies (follicular lymphoma and chronic lymphocytic leukemia), the defect in alloantigen presentation of tumoral cells can be repaired by up-regulation of B7 and other co-stimulatory molecules via CD40. We studied the role of B7 molecules in alloimmune recognition and the various ways to improve the antitumoral response on peripheral blood leukemic cells from 20 patients with a diagnosis of primary acute myeloid leukemia (AML). We focused on myelo/monocytic M4/M5 French-American-British classification subtypes which are considered as the neoplastic counterpart of normal monocytes, a prototypic APC. In one-way mixed lymphocyte reaction of CD4+ T cells against leukemic cells, differences in B7-1, B7-2 or CD40 expression by AML cells did not induce specific cytokine secretion; interleukin (IL)-2 and interferon (IFN)-gamma were detected but not IL-4, corresponding to a Th1 pattern. Blockade experiments showed that proliferation and IFN-gamma secretion only partially depended on B7 molecules, which in contrast had a pivotal role in IL-2 synthesis. In contrast with murine models which suggest a pivotal role for CD80/B7-1 in the immune response against AML, our data support a greater role for CD86/B7-2, in line with the baseline expression of CD86/B7-2 and lack of CD80/B7-1 on most M4/M5 AML cells. AML cell stimulation via CD40: (1) significantly improved IL-2 secretion but not proliferation of responding T lymphocytes, (2) increased CD54/ICAM-1 expression in three quarters of cases, (3) failed in most cases to induce CD40-specific CD80/B7-1 up-regulation, and (4) had a weak effect on CD86/B7-2 expression. These data contrast with the very efficient up-regulation of both B7 co-stimulatory molecule expression and tumoral cell alloimmune recognition following CD40 stimulation in B cell malignancy models. The role of the defective B7 molecule up-regulation by the CD40 pathway in inefficient tumor immunogenicity of primary AML cells has to be further investigated, in particular using transfection experiments of CD80/B7-1-deficient AML cell lines. From our in vitro data we conclude that B7 molecules play an important role in the alloimmune surveillance of AML as suggested by the high B7 molecule dependency of IL-2 secretion. Nonetheless, the contribution of B7 molecules to alloimmune T cell proliferation against primary AML cells in human and the way to improve it--regulation via CD40 in particular--differ from B cell malignancies and murine models, suggesting the requirement for specific strategies in the development of antitumor immunity.