Differentiation-associated changes in human non-T, non-B leukemia cell lines after treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA)

NF-kappaB (p65/RelA) as a regulator of TNFalpha-mediated ML-1 cell differentiation

ML-1 human myeloblastic leukemia cells, suspended in serum-depleted medium, proliferate when the insulin-like growth factor-1 (IGF-1) and transferrin (Tf) are supplied, but differentiate to monocytes when these factors are replaced by the tumor necrosis factor-alpha (TNF-alpha). Induction of differentiation, but not of proliferation, involved the selective activation of diverse members of the NF-kappaB family of proteins. In differentiation-induced cells, NF-kappaB (p65) was translocated from the cytoplasm to the nucleus, whereas NF-kappaB (p75) remained localized to the cytoplasm. In contrast, NF-kappaB (p52) was present in the nuclei of proliferation- as well as of differentiation-induced ML-1 cells. The differentiation-specific translocation of NF-kappaB (p65) from the cytoplasm to the nucleus was mediated by an increase in the level of NIK, the NF-kappaB-inducing kinase which, through phosphorylation of IkappaB kinase alpha (Ikappakalpha), causes a decrease in the level of IkappaBalpha, allowing p65 to move from the cytoplasm to the nucleus. The p52/p65 heterodimer formed in the nucleus, bound specifically to the promoter of the tumor suppressor protein p53, effecting a 25 to 30-fold increase in the level of this protein. As we reported previously (Li et al, Cancer Res 1998; 58: 4282-4287), that increase led to the decreased expression of proliferating cell nuclear antigen (PCNA) and to the loss of proliferation-associated DNA synthesis. The ensuing uncoupling of growth from differentiation was followed by the initiation of the monocyte-specific differentiation program.

Single glycosyltransferase, core 2 beta1-->6-N-acetylglucosaminyltransferase, regulates cell surface sialyl-Lex expression level in human pre-B lymphocytic leukemia cell line KM3 treated with phorbolester

Sialyl-Lex (sLex) antigen expression recognized by KM93 monoclonal antibody was significantly down-regulated during differentiation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in human pre-B lymphocytic leukemia cell line KM3. The sLex determinants were almost exclusively expressed on O-linked oligosaccharide chains of an O-glycosylated 150-kDa glycoprotein (gp150). A low shear force cell adhesion assay showed that TPA treatment significantly inhibited E-selectin-mediated cell adhesion. Transcript and/or enzyme activity levels of alpha1-->3-fucosyltransferase, alpha2-->3-sialyltransferase, beta1-->4-galactosyltransferase, and elongation beta1-->3-N-acetylglucosaminyltransferase did not correlate with sLex expression levels. However, transcript and enzyme activity levels of core 2 GlcNAc-transferase (C2GnT) were significantly down-regulated during TPA treatment. Following transfection and constitutive expression of full-length exogenous C2GnT transcript, C2GnT enzyme activities were maintained at high levels even after TPA treatment and down-regulation of cell surface sLex antigen expression by TPA was completely abolished. Furthermore, in the transfected cells, the KM93 reactivity of gp150 was not reduced by TPA treatment, and the inhibition of cell adhesion by TPA was also blocked. These results suggest that sLex expression is critically regulated by a single glycosyltransferase, C2GnT, during differentiation of KM3 cells.

The protein kinase C inhibitor H7 blocks phosphorylation of stathmin during TPA-induced growth inhibition of human pre-B leukemia REH6 cells

The human pre-B acute lymphoblastic leukemia cell line REH6 was used to analyze the regulation of a ubiquitous intracellular phosphoprotein stathmin (Mr 19,000, pl = 5.6-6.2). We demonstrated by 32P-labeling that the short (1 h) treatment of the REH6 cells with the tumor promoting phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), resulted in a rapid phosphorylation of at least three (P1, P2 and P3) stathmin isoforms without an alteration of stathmin isoform expression. Furthermore, Western blot analysis with specific antiserum showed that the prolonged period (48 h) of TPA treatment partially reduced protein levels particularly of two (N2 and P2) stathmin isoforms. The potent and relatively specific protein kinase C (PKC) inhibitor, 1,(5-isoquinolinesulphonyl)2methylpiperasine dihydrochloride (H7), partially inhibited these TPA effects, whereas the specific calmodulin inhibitor R24571 (calmidazolium) had no effect upon these events. Our findings suggest that stathmin phosphorylation in REH6 cells could be in part mediated by PKC activation.

Differential down-regulation of protein kinase C subspecies in KM3 cells

The down-regulation of protein kinase C (PKC) subspecies in KM3 cells (a pre-B, pre-T cell line) has been examined. The PKC from KM3 cells was resolved into two subspecies, type II (mainly beta II) and type III (alpha), upon hydroxyapatite column chromatography. Biochemical and immunocytochemical analysis revealed that, when these cells were treated with 12-O-tetradecanoylphorbol 13-acetate (TPA), the time course of down-regulation of the PKC subspecies was different; type II PKC was translocated and depleted from the cell more quickly than type III enzyme. The results suggest that each PKC subspecies plays a different role in the cellular response to TPA and probably to other external stimuli.

Establishment of a common acute lymphoblastic leukemia cell line (LC4-1) and effects of phorbol myristate acetate (PMA) on the surface antigen expression of the cell line

A common acute lymphoblastic leukemia (ALL) cell line, designated LC4-1, was established from peripheral blood mononuclear cells of a patient with acute non-T-cell ALL. LC4-1 cells were characteristically positive for Ia, B4, and common ALL antigens (CALLA), but negative for B2, Tac, T3, T4, T8, T11, and M1 antigens and E-rosette formation. Approximately 30% of LC4-1 cells expressed detectable amounts of B1 antigens. LC4-1 cells expressed neither Epstein-Barr-virus-associated nuclear antigen (EBNA), cytoplasmic immunoglobulins (cIg) nor surface immunoglobulins (sIg). Gene rearrangements had already occurred in LC4-1 in the D-J region of immunoglobulin heavy chain genes, but not in T-cell receptor (beta-chain) genes, suggesting that LC4-1 is a progenitor cell line of B-cell lineage earlier than pre-B-cells. The expression of cell surface antigens of LC4-1 was changed by treatment with 4-phorbol 12-myristate 13-acetate (PMA) (0.1 ng/ml) for 2 days. Before treatment with PMA, about 98% of LC4-1 cells were positive for B4, CALLA, and Ia. However, following treatment they lost CALLA expression without any change in expression of Ia and B4. There was no change in B1-positive population. The change in surface antigens on LC4-1 cells seems to be due to differentiation induced in the cells by PMA. These results support the hypothesis that CALLA is a differentiation antigen and suggest one possible differentiation pathway for pre-B-cells.

Isoenzyme studies in human leukemia-lymphoma cell lines--V. Induction of differentiation by T-cell derived differentiation-inducing activity

A panel of human leukemia cell lines from various lineages (T-cell, pre B- and Non-T/Non-B cell, myelomonocytic and erythroleukemia cell lines) were utilised as model systems of the distant effects of differentiation-inducing activity (DIA) produced by the T-leukemia cell line HUT-102. DIA inhibited cell proliferation and induced distinct morphological changes which were more pronounced in the myelomonocytic and erythroleukemia cell lines than in the lymphoid cell lines. DIA triggered in the myelomonocytic and erythroleukemia cell lines an increase in the number of NBT-reducing cells and caused strong adherence to plastic surface. The T-cell lines showed aggregation of cells in floating clusters. In the isoenzyme analysis of the enzymes carboxylic esterase and acid phosphatase, it was found that DIA stimulated the new expression of isoenzymes and a stronger staining intensity of several isoenzyme bands in all cell lines, however, at varying degrees. HL-60 and HEL displayed newly a monocyte-specific isoenzyme. Several myelomonocytic and erythroleukemia cell lines were triggered to express the tartrate-resistant acid phosphatase isoenzyme. The cell kinetic, morphological, functional and isoenzymatic data demonstrated that DIA effected the development of the different blood cell types. However, it appears that the cells reached a new differentiation block after acquired expression of differentiation-linked features; the lymphoid cell lines were more limited in their response to DIA than the myeloid and erythroid cells.

Phorbol ester enhances deoxynucleoside incorporation while inhibiting proliferation of K-562 cells

Recently a new technique has been developed to study bromodeoxyuridine incorporation into DNA as a function of the cell cycle phase distribution. We have made the observation that treatment of the hematopoietic cell line K-562 results in a complete and immediate cessation of cell growth, although tritiated thymidine incorporation is markedly elevated for as long as 5 days. We have made use of that newly described technique to study this phenomenon.

In vitro drug testing using hemopoietic cells: goals and limitations

In vitro drug sensitivity is one of many biologic variables which may predict in vivo drug response. Even if in vitro assays provide relevant data, for some tumors, variable levels of stem-cell origin, differentiation, tumor heterogeneity, or self renewal may be more important than cytotoxicity to proliferating cells. Although ANLL has been used here frequently as a model, it may not be the most appropriate tumor for study. Unlike many cancers, in ANLL, primary drug resistance is unusual, and in relapse, secondary drug resistance is usually incomplete. It has been suggested that in vitro drug sensitivity predicts remissions for patients who do not die of infection or remain aplastic during induction therapy. However, for the majority of patients, this argument acknowledges the overriding importance of biologic variables other than in vitro drug cytotoxicity. For rapidly growing tumors, such as Burkitt's lymphoma, rapid emergence of drug resistance related to disease burden may be the most important response determinant. Perhaps in other tumors, in vitro drug sensitivity will be an independent variable of overriding importance. To determine the role of in vitro drug testing, trials examining in vitro drug sensitivity must meet stringent criteria. The assays should use well-defined and reproducible cultures and drug exposures. The trials must be large enough, contain homogenously treated patients, and use carefully defined response and survival endpoints. Decision rules derived from such trials must be further tested by prospective evaluation. Investigators conducting these trials must be prepared to search for important in vitro results reflecting tumor biology and to analyze in vitro drug sensitivity as only one continuous variable determining in vivo responses. Such trials will be difficult to conduct and expensive. In the final analysis, in vitro assays may find their most important roles as preclinical drug screens and models for in vitro drug resistance. Further insights into molecular genetics of malignant transformation and drug resistance may make such assays obsolete, but for the present, they provide important insights into tumor variability and mechanisms of drug response.