Formation of cytosine arabinoside-5'-triphosphate in different cultured lymphoblastic leukaemic cells with reference to their drug sensitivity.

The accumulation of intracellular cytosine arabinoside-5'-triphosphate (Ara-CTP) is determined in five lymphoblastic cell lines: Molt 4, H9 and three newly established cell lines from paediatric patients, KFB-1, KFB-2, KFT-1. The cell lines KFB-1 and KFB-2 are B-lymphoblastic (B-ALL), the others are T-lymphoblastic leukaemic cells (T-ALL). The Ara-CTP levels were compared with the sensitivity of the cells to Ara-C. The cells were incubated at different concentrations (100 nM-100 microM) of Ara-C for 4 h or incubated for variable times (30 min-11 h) at 0.1, 1 and 10 microM Ara-C to form Ara-CTP. The Ara-CTP-concentrations were measured by high pressure liquid chromatography (HPLC). To determine the sensitivity of the cells to Ara-C, the MTT colorimetric-assay was used. The studies indicate that different B- and T-lymphoblastic leukaemia cell lines accumulate Ara-CTP to a markedly different extent. Ara-CTP plateau levels and sensitivity of the cells to Ara-C correlated well in four of the five cells lines studied.

Decreased anti-human immunodeficiency virus type-1 activities of 2',3'-dideoxynucleoside analogs in MOLT-4 cell sublines resistant to 2',3'-dideoxynucleoside analogs.

Human T-lymphoid MOLT-4 cells were grown continuously for more than 1 year in medium containing either 3'-azido-2',3'-dideoxythymidine (AZT), 2',3'-dideoxyinosine (ddI) or 2',3'-dideoxycytidine (ddC) at concentrations similar to peak plasma levels found in clinical trials in patients with AIDS. To test antiviral activities of the nucleoside analogs against HIV-1 in the cell sublines designated MOLT-4r-AZT, MOLT-4r-ddI and MOLT-4r-ddC, the number of infected cells, p24 HIV-1 antigen in culture medium and syncytium formation of infected cultures were determined. The results showed that anti-HIV-1 activities of AZT, ddI and ddC were significantly decreased in the resistant MOLT-4 cell sublines grown continuously with the respective nucleoside analog, probably due to the development of cell populations resistant to the drugs.

In vitro differentiation of human neuroblastoma cells induced by sodium phenylacetate.

Sodium phenylacetate (NaPA) at concentrations ranging from 2 to 6 mM stimulated morphological differentiation of two human neuroblastoma cell lines IMR-32 and UKF-NB-3. These concentrations inhibited growth and DNA synthesis of the cells in a dose dependent manner without significant effect on cell viability. The differentiated cells showed pseudoganglia formation and extension of cellular processes. The morphological differentiation in both cell lines was accompanied by decreased expression of N-myc oncoprotein. These results suggest that NaPA at concentrations, which have been achieved in humans with no significant adverse effects, promotes differentiation of cultured human neuroblastoma cells in association with the reduced expression of the malignant phenotype.

Aphidicolin selectively kills neuroblastoma cells in vitro.

Aphidicolin is a tetracyclic diterpene antibiotic which is known to inhibit the growth of eucaryotic cells by reversible binding to DNA polymerase alpha without significant effect on cell viability in most common human cell lines. We observed that aphidicolin at a concentration of 5 x 10(-7) M kills all cells of four human neuroblastoma cell lines. In contrast, viability of normal human embryonal cells and of human continuous cell lines including HeLa, H9, A549 and Caco-2 was influenced only moderately by aphidicolin. In addition, neuroblastoma cells were killed after treatment with 5 x 10(-7) M aphidicolin in cocultures with normal embryonal cells which continued to proliferate after removal of aphidicolin. These results show that aphidicolin provides an agent which selectively kills neuroblastoma cells in vitro.

Effect of aciclovir on the replication of herpes simplex virus type 1 in MA-104 cell line resistant to aciclovir.

A culture of monkey kidney cells (MA-104) resistant to aciclovir (CAS 59277-89-3) was established. The resistant cells were continuously grown in medium containing 200 mumol/l aciclovir whereas normal cells died in such medium. The doses of aciclovir required for 50 and 90% reduction in virus yield were for several Herpes simplex virus Type 1 clinical isolates up to 5-fold higher in resistant than in normal MA-104 cells; in contrast, doses required for 99% reduction in virus yield could be as much as 50-fold higher in the resistant cells. Virus yields developed in the presence of 30 mumol aciclovir in culture medium were at least 10(3)-fold higher in resistant than in normal MA-104 cells. The results showed that the antiviral effect of aciclovir may be significantly decreased in the cell line which developed resistance to aciclovir.

2',3'-Dideoxycytidine preferentially inhibits in vitro growth of granulocyte-macrophage colony-forming cells from patients with chronic myeloid leukemia.

The effect of three nucleoside analogs, including 2-methyl-2'-deoxyadenosine (MDA), 5-amino-2'-deoxyuridine (ADU) and 2',3'-dideoxycytidine (DDC) on colony formation from unfractionated human bone marrow obtained from volunteers expressing parameters typical for normal cells (NBM) and from patients with the diagnosis of chronic myeloid leukemia (CMLBM) was observed. For the clonal growth of granulocyte-macrophage colony-forming cells (GM-CFC), a semisolid fibrin clot culture medium supplemented with 20% fetal bovine serum and 10% human placental conditioned medium was used. DDC has been shown to be at least a 10-fold more potent inhibitor for the growth of GM-CFC from CMLBM than from NBM. On the other hand, the effect of MDA and ADU on CMLBM did not differ markedly from the effect on NBM. These results suggest that DDC inhibits preferentially progenitor cells from CMLBM.