Differentiation of human leukemia cells and its usefulness for clinical diagnosis

12-0-Tetradecanoyl Phorbol-13-Acetate (TPA) and Its Effect on Leukaemic Cells, In-vitro-A Review

The action of the promoting agent 12-0-tetradecanoyl phorbol-13-acetate (TPA), an active component of croton oil, on the cell membrane, is described. TPA primarily acts on Protein Kinase C (PKC), which is the prime target for this agent. PKC activation and calcium mobilization are the basic pathways for signal transduction and the regulation of differentiation, explaining how TPA affects cell growth and proliferation in some cell types. The effects of TPA on leukaemic cells in-vitro, is reviewed and the changes in cell surface features, membrane phenotype, regulation of growth and differentiation in leukaemic cells and particularly in B-cell neoplasias are described and discussed in detail. The importance of incubation of leukaemic cells with TPA, as a routine in-vitro test in leukaemia is emphasized, in the light of information reported in this review.

Treatment of human promyelocytic leukemia in the SCID mouse model with cotylenin A, an inducer of myelomonocytic differentiation of leukemia cells

Cotylenin A has differentiation-inducing activity in human myeloid leukemia cell lines and leukemic cells that were freshly isolated from acute myeloid leukemia (AML) patients in primary culture. Injection of the human promyelocytic leukemia cell line NB4 into SCID mice resulted in the death of all mice due to leukemia. Administration of cotylenin A significantly prolonged the survival of mice inoculated with NB4 cells. In an in vivo analysis, cotylenin A induced the differentiation of leukemia cells in a retinoid-resistant leukemia model. Cotylenin A may be useful for differentiation therapy of retinoid-resistant leukemia.

Differentiation of human myeloid leukemia cells by plant redifferentiation-inducing hormones

Although differentiation therapy for patients with acute promyelocytic leukemia (APL) using all-trans retinoic acid (ATRA) has now been established, acute myeloid leukemia (AML) patients with other than APL only show a limited clinical response to ATRA. We must consider novel therapeutic drugs against other AML to develop a differentiation therapy for leukemia. Regulators that play an important role in the differentiation and development of plants may also affect the differentiation of human leukemia cells through a common signal transduction system, and might be clinically useful for treating AML. Cytokinins are important purine derivatives that serve as hormones that control many processes in plants. Cytokinins such as kinetin, isopentenyladenine (IPA) and benzyladenine were very effective at inducing nitroblue tetrazolium (NBT) reduction and morphological changes in human myeloid leukemia cells into mature granulocytes. On the other hand, cytokinin ribosides such as kinetin riboside, isopentenyladenosine (IPAR) and benzyladenine riboside were the most potent for inhibiting growth and inducing apoptosis. When the cells were incubated with cytokinin ribosides in the presence of an O2- scavenger, antioxidant or caspase inhibitor, apoptosis was significantly reduced and differentiation was greatly enhanced. These results suggest that both cytokinins and cytokinin ribosides can induce the granulocytic differentiation of HL-60 cells, but cytokinin ribosides also induce apoptosis prior to differentiation. Cotylenin A has been isolated as a plant growth regulator exhibits cytokinin-like activity. Although it has a different structure than cytokinins, it also induces the differentiation of human myeloid leukemia cells. These results suggest that there is an association between the action of plant redifferentiation-inducing hormones and the mechanism of the differentiation of human leukemia cells.

Cotylenin A--a plant growth regulator as a differentiation-inducing agent against myeloid leukemia

Acute myeloid leukemia (AML) is characterized by the arrest of differentiation leading to the accumulation of immature cells. This maturation arrest can be reversed by certain agents. Although differentiation therapy for patients with acute promyelocytic leukemia (APL) using all-trans retinoic acid (ATRA) has been established, the clinical response of AML patients other than those with APL to ATRA is limited. We must consider novel therapeutic drugs against other forms of AML for the development of a differentiation therapy for leukemia. Regulators that play an important role in the differentiation and development of plants or invertebrates may also affect the differentiation of human leukemia cells through a common signal transduction system, and might be clinically useful for treating AML. Cotylenin A, a plant growth regulator, is a potent and novel inducer of the monocytic differentiation of human myeloid leukemia cell lines and leukemia cells freshly isolated from AML patients.

Differentiation of human acute myeloid leukaemia cells in primary culture in response to cotylenin A, a plant growth regulator

Cotylenin A, which has a diterpenoid tricarbocyclic skeleton, has been isolated as a plant growth regulator, has been shown to affect several physiological processes of higher plants and have differentiation-inducing activity in several myeloid leukaemia cell lines. We examined the effect of cotylenin A on the differentiation of leukaemic cells that were freshly isolated from acute myeloid leukaemia (AML) patients in primary culture. Cotylenin A significantly stimulated both functional and morphological differentiation of leukaemia cells in 9 out of 12 cases. This differentiation-inducing activity was more potent than those of all-trans retinoic acid and 1alpha,25-dihydroxyvitamin D3 (VD3). Treatment with a combination of cotylenin A and VD3 was more effective than cotylenin A or VD3 alone at inducing the monocytic differentiation of AML cells.

The diagnosis of acute leukemia with undifferentiated or minimally differentiated blasts

A small group of acute leukemias can be classified by morphological, cytochemical, or immunological marker analysis neither as acute lymphatic leukemia nor as acute myeloid leukemia. These leukemias are referred to as acute undifferentiated leukemia (AUL) and make up 2%-7% of the acute nonmyeloid leukemias. These leukemias are poorly defined in the literature and are also sometimes referred to as AML-MO. Most of the definitions include in the morphological and cytochemical criteria the expression of myeloid antigens. Here the value of these markers and of other techniques used in the diagnosis of undifferentiated or minimally differentiated leukemia is discussed. More than half of the leukemias that are undifferentiated by morphology and cytochemistry on the light-microscopic level show a positive reaction for myeloperoxidase by electron microscopy, which points to an early myeloid differentiation of those leukemias. Immunological marker analysis in most cases is inconclusive. Most show a positive reaction for CD 13, CD 33 or other myeloid-associated markers. However, in about half of these leukemias co-expression of lymphatic markers is seen. In a small minority, only lymphatic markers are expressed. Cytogenetic abnormalities which are found in these leukemias vary in type, and antigen receptor rearrangements are not lineage specific. Receptor studies, gene expression, and in vitro culture studies may, in the near future, contribute substantially to our knowledge about the commitment of these undifferentiated or minimally differentiated blasts. Recent definitions for AUL and AML-MO based on these different techniques are discussed.

Prognostic significance of cytochemical analysis of leukemic M2 blasts

Cytochemical analysis of leukemic blasts from 46 patients with acute myeloblastic M2 leukemia (according to the FAB classification) was performed before and after cytostatic therapy, and compared with findings obtained in 20 age- and sex-matched control subjects. Cytochemical findings for myeloperoxidase (MPO), Sudan black B, acid phosphatase and alpha-naphthyl-acetate esterase (ANAE) were related to the achievement of the first complete remission (CR), i.e. data were compared after the patients had been divided into CR and non-CR groups. The analysis clearly showed that a high proportion of myeloperoxidase- and, to a lesser extent, Sudan black B-positive blasts before treatment may have constituted a significantly unfavourable prognostic factor.

In-vitro differentiation of cells of patients with acute undifferentiated leukaemia

The diagnosis of acute undifferentiated leukaemia (AUL) is made when the cells of patients with acute leukaemias cannot be classified as myeloid or lymphoid by means of morphological, cytochemical and immunological criteria. The mononuclear cells of eight different AUL patients were cultured in suspension for 3 d with or without TPA. After culture, especially in the presence of TPA, the cells of all patients expressed at least one myeloid membrane antigen. It was shown that this antigen expression was dependent on de novo protein synthesis and not influenced by inhibition of proliferation.

Clinical application of phorbol diester-induced leukemic cell differentiation for the definite diagnosis of acute leukemias

Seventy-three patients with acute leukemias or chronic myelogenous leukemias in blast crisis were evaluated as to the susceptibility of their leukemic cells to differentiation induction by a chemical agent, 12-O-tetradecanoyl phorbol-13-acetate (TPA). Leukemic cells of myeloid origin treated with TPA showed monocyte-macrophage-lineage differentiation morphologically and functionally, whereas those of lymphoid origin did not. We applied these differentiation phenomena for the clinical diagnosis of three leukemia cases in whom it was difficult to determine whether the leukemic cells were of non-lymphoid or lymphoid origin, although all the regular diagnostic procedures available had been performed. We successfully diagnosed these three cases by utilizing the above differentiation phenomena. Furthermore, this technique was clinically beneficial as to the choice of adequate chemotherapy in each of these leukemia cases. These findings confirm that the responsiveness to TPA of leukemic cells is of clinical usefulness for the definite diagnosis of acute leukemias.

Induction of myeloperoxidase in five cases of acute unclassified leukaemia

For further analysis of their lineage affinity the differentiation capacity of five cases of acute unclassified leukaemias were studied in vitro using 5 nM 12-O-tetradecanoyl-phorbol-13-acetate as an inducing agent. After 4 d in vitro a co-expression of both myeloid and early B-lymphoid or myeloid and early T-lymphoid antigens on the same population of cells was found. While ultrastructural analysis of the blasts prior to culture revealed the morphology of undifferentiated blasts without any specific endogenous peroxidase activity, the cultured blasts displayed monoblastic features and myeloperoxidase activity after 4 d in vitro. Since this type of peroxidase is highly specific for the myelomonocytic lineage the data indicate myelomonocytoid differentiation of all five cases studied. The co-expression of lymphoid as well as myeloid antigens and myeloperoxidase by the same blasts after culture could be indicative of bilineage differentiation capacity characterizing the original blasts as bipotential progenitor cells.

Acute leukemia with mediastinal mass, lymphadenopathy, and monocytic precursor cells

Cell marker analysis with monoclonal antibodies (MoAb) as well as differentiation studies with the chemical inducer TPA were used to identify a population of apparently lymphoid cells as monocytic precursor cells in a patient with acute leukemia. The initial manifestation of the disease with mediastinal mass and lymphadenopathy was followed by the appearance of small lymphocyte-like blast cells in bone marrow (BM) and peripheral blood (PB). Although a lymph node biopsy revealed an infiltration with monoblasts, the leukemic cells in BM and PB were not classifiable. However, when the patient relapsed after chemotherapy with large monoblasts and again with morphologically lymphoid blast cells, the latter could be classified by treatment with TPA. After incubation with the inducer (12-48 hr) the cells became positive with the MoAB VIM-D5, showed a strong reaction with alpha-naphthyl-acetate-esterase and developed macrophage like morphology, as well as phagocytic properties. During the terminal phase of the disease, small, lymphocyte-like blast cells predominated. These cells could be classified by a panel of MoABs. They expressed myeloid determinants (VIM-D5, VIM-2, MY 9, VIM-12, VIM-13) but showed no reactivity with MoABs specific for lymphocytic cells.

An acidic glycosphingolipid, monosialo-ganglioside GM3, is a potent physiological inducer for monocytic differentiation of human promyelocytic leukemia cell line HL-60 cells

A remarkable increase in monosialo-ganglioside GM3 was observed during the monocytic differentiation of HL-60 cells induced by 12-0-tetradecanoyl-phorbol-13-acetate(TPA). On the other hand, when the cells were cultured with exogenously-added ganglioside GM3 in serum-free conditions, their differentiation along a monocytic lineage was demonstrated with simultaneous complete growth inhibition. Other gangliosides such as ganglioside GM1 showed no effects on cell differentiation, exhibiting instead stimulatory actions on the cell growth. These results indicate that a physiologically-existent, membranous ganglioside GM3, which specifically increases during monocytic cell differentiation, might play a primary role as a trigger in the monocytic cell differentiation.

Acute undifferentiated leukemia: induction of partial differentiation by phorbol ester

Expression of lineage-associated surface antigens, was studied in 7 patients with acute undifferentiated leukemia (AUL), 3 patients with acute myeloid leukemia (AML), 4 patients with acute lymphoid leukemia (ALL) and bone marrow from 2 healthy donors, before and after exposure to the differentiating agent 12-O-tetradecanoylphorbol-13-acetate (TPA). The surface antigens were identified by monoclonal antibodies (My4, My8, My9, MO1, B1, CALLA, T11) and formation of EA and EAC rosettes. Adherence to plastic was also assessed. Cells from the AML patients responded to TPA with an increase in myeloid antigen positive cells and other markers of differentiation. Four of the AUL patients showed, also, a large increase in the fraction of cells expressing one or more myeloid markers, in correlation with formation of EAC rosettes. In contrast, the percentage of cells expressing myeloid antigens, did not increase in the 4 ALL patients, or in the normal donors. These findings confirm the heterogeneity of undifferentiated leukemias, and suggest the hypothesis that some AUL's can be induced to express markers of early myeloid cells.

Established leukemia cell lines: their role in the understanding and control of leukemia proliferation

For investigation of mechanisms of leukemogenesis and control of proliferation of leukemia cells, various preleukemic hematopoietic progenitor cell lines and leukemia cell lines have been established. The role of these established cell lines in understanding leukemogenesis and control of leukemia cell proliferation is described. The results of studies on biological characteristics of numerous human leukemia-lymphoma cell lines suggest that the heterogeneity in various markers of the cell lines reflects different patterns of normal hematopoietic cell differentiation. Then, recent studies on the control of proliferation of leukemia cells by induction of terminal differentiation with the use of established leukemia cell lines both in vitro and in vivo are described. Therapeutic significance of the results obtained with these leukemia cell lines is also discussed.