Characteristics of reovirus-mediated chemoimmunotherapy of murine L1210 leukemia

Summary We have previously demonstrated the ability of reovirus to function synergistically with chemotherapy in the treatment of murine EL-4 lymphoma. This study characterizes this treatment regimen in the therapy of L1210 leukemia. Animals with an estimated tumor burden of 10⁷ cells were treated with 9 mg/kg 1,3-bis(2-chloroethyl)-1-nitrosourea. Reovirus type 3, which had been quantitated either by particles or plaque-forming units (pfu), was administered 48 h after chemotherapy. Complete remission of tumor was observed in 80% of the animals which received either 10¹¹ particles or 10⁹ pfu of reovirus. Cured animals were resistant to challenge with homologous tumor, but were susceptible to challenge with heterologous tumor. Reovirus undergoes limited replication at the tumor site, and virus-specific antibody appears only after disappearance of reovirus-infected cells and virus from the ascites fluid. Reovirus appears to function therapeutically by inducing a tumor-specific cytolytic immune response.     

An antagonistic effect between aziridine and diaziridine on their cytotoxic activities against L-1210 mouse leukemia cells

The effect of the combination of 1-methyl-2-$\text{p}$-chlorophenylaziridine and 1,2-dimethyl-3-$\text{p}$-chlorophenyldiaziridine on cytotoxic activities against L-1210 mouse leukemia cells was studied. Both compounds clearly showed an antagonistic interaction. The results supported our hypothesis that nitrosomethane formed by the fragmentation of aziridine via the N-oxide in a cellular system causes the cytotoxic behavior of the N-methyl aziridines.     

Characteristics of the chemostat culture of murine leukemia L 1210 cells

Mouse leukemia L 1210 cells were cultivated under glucose limitation in a chemostat. More than 20 steady-states were established over 9 different dilution rates ranging from 0.20 day⁻¹ (cell doubling time 83 h) to 2.0 days⁻¹ (cell doubling time 8.3 h). The steady-states were characterized by: a constant cell number, constant cell volume, constant concentrations of DNA, RNA, and L-lactate (in the culture supernatant), a constant percentage of cells labelled by autoradiography, and constant rate of incorporation of [³H]TdR, [³H]uridine, and ¹⁴C-labelled amino acids into cellular acid-precipitable material. Individual steady-states were maintained for periods up to 600 h continuous operation of the chemostat. A maximum output of 66.4 × 10⁶ cells/h was obtained at a dilution rate of 1.3 day⁻¹. The glucose substrate constant was determined as 0.0063 mg/ml. The relationships between dilution rate and the steady-state cell concentration, glucose concentration, and output of L 1210 cells from the chemostat, were in general agreement with the theoretical curves. It was found that the principles of continuous culture derived from the study of microorganisms are to a large extent applicable to the cultivation of animal cells.     

Decreased sensitivity of an interferon-resistant subline of murine leukemia L-1210 cells to toxic effects of ricin and abrin.

Approximately two to four times higher concentrations of the plant toxins abrin and ricin are required to inhibit protein synthesis in interferon-resistant L-1210R cells to the same degree as in interferon-sensitive L-1210S cells. However, amounts of interferon 10-fold higher than those required for protection from viral infection fail to show any effect on ricin intoxication of L-1210S cells.     

Chronochemotherapy: L 1210 leukemia and beyond

In cancer and other therapeutic research, an interpretation of median survival times can and should take cure into account. With this qualification, an analysis of recently published data provides further statistically significant evidence in favor of cancer chronotherapy as compared to homeostatic therapy.     

Active transport of cobalamins in leukemic cells of L-1210 mice

The Tc-II receptors of cell surface membrane and the cobalamins entering into the L-1210 mouse leukemia cells were investigated. We used the blood serum Tc-II saturated with 57CoCNCbl for radioactivity determination separately in solubilized receptors and inside of the cells. The data on ligand regulation of the leukemic cell membrane receptors number were received. The internalization of radioactive complex of Tc-II and cobalamin was revealed during intensive 3H-thymidine incorporation into DNA of the cultivated cells.     

5-Methylnicotinamide-resistant variant of mouse lymphoma L1210 cells

5-methylnicotinamide is an inhibitor of poly(ADP-ribose) synthetase, and it enhances the cytotoxicity of alkylating agents and of radiation in mouse lymphoma L1210 cells. We have isolated a spontaneous variant L1210 cell which shows increased resistance to 5-methylnicotinamide and has a reduced potentiation of cell-killing by methylnitrosourea and by γ-radiation. This observation is further evidence in support of the participation of (ADP-ribose)_n in DNA excision repair and in cell survival. This variant may be of use in the molecular analysis of this component of DNA repair.     

Active immunotherapy of L1210 leukemia with neuraminidase-treated,drug-resistant L1210 sublines

Summary The effectiveness of neuraminidase-treated, drug-resistant L1210 sublines in active immunotherapy of L1210 leukemia was evaluated. Optimal conditions for the establishment of in vitro, drug-resistant cells included (a) proper drug concentration, (b) the use of logarithmic-phase cultures in fresh medium, containing 5 or 10% serum, and (c) continual exposure to drug. Active immunotherapy, after tumor burden was reduced with chemotherapy, with neuraminidase-treated cells alone was either effective or deleterious, depending upon the drug-resistant subline used for immunization. The combination of BCG and neuraminidase-treated cells was superior to treatment with chemotherapy only. Optimal response was observed with the use of parental L1210 cells, combined with BCG, in immunotherapy of parental L1210 tumor. The results emphasize that an important prerequisite to successful immunotherapy is that tumor vaccines must elicit immunologic products which are cytotoxic for residual tumor.Submitted in partial fulfillment of the requirements for the Masters of Science Degree, University of Oklahoma     

Induction of gamma-glutamylcysteine synthetase by prostaglandin A2 in L-1210 cells

Effects of prostaglandin A2 (PGA2) on glutathione (GSH) status in L-1210 cells were examined. When the cells were cultured in the presence of PGA2, a persistent rise of cellular GSH concentration was observed 6 h after the addition of PGA2. This stimulatory effect of PGA2 was abolished if the cells were pretreated with an enzyme inhibitor of GSH synthesis, buthionine sulfoximine. Subsequent study with cell free extract of cultured L-1210 has revealed that PGA2 stimulated the biosynthesis of gamma-glutamylcysteine synthetase (EC 6.3.2.2). Actinomycin D inhibited this stimulatory effect of PGA2 on cultured cells. The optimal pH, Km value for glutamic acid and sensitivity to inhibitors of gamma-glutamylcysteine synthetase from PGA2 treated and nontreated cells were virtually the same. Thus, our findings suggest that PGA2 induced gamma-glutamylcysteine synthetase in cultured L-1210 cells which is responsible for the elevated level of GSH in these cells.     

Immunological resistance to L1210 leukemia induced by viable L1210/DTIC cells

Summary Permanent, drug-induced antigenic alterations, not detectable in parental cells and transmissible after the withdrawal of treatment with the drug, have been obtained in mouse lymphoma. Viable L1210/DTIC cells, because they are rejected by syngeneic animals and carry L1210-associated TAA, can elicit host resistance to a subsequent inoculum of parental L1210. Mice challenged with viable L1210/DTIC cells, following rejection, were more resistant than mice immunized with inactivated parental cells. Resistance was specific and related to the immunogenicity of the TAA of the original tumor line employed.Active immunization was potentiated by adoptive transfer of immune lymphocytes, as evidenced by marked improvement in animal survival. Also, the treatment of tumor-bearing animals with anticancer compounds in conjunction with immunological alteration may result in an improved therapeutic response. BCNU administered to immunized animals 6 days after challenge with parental tumor cells resulted in augmented host survival, possibly attributable to partial resistance of a secondary immune response to the drug and a late nadir of immunosuppression, occurring after the completion of therapeutic action. Cyclophosphamide given before immunization enhanced host survival to a subsequent challenge of L1210 leukemia, conceivably as the result of preferential inhibition of T suppressor cells.     

Isolation and charaterization of surface glycoproteins from L-1210, P-388 and HeLa cells

A method is described that permits the rapid extration of the cell surface glycoproteins of two murine leukemic cells, the P-388 and the L-1210 cells as well as those of the human adenocarcinoma cells, the HeLa cells.Proof of the surface location of these glycoproteins is provided by labeling the intact cells; (a) with ¹²⁵I by the lactoperoxidase iodination technique; (b) with ³H by the galactose oxidase-reductive tritiation method. Most of these glycoproteins were also shown to incorporate radioactive glucosamine and fucose. By these criteria as well as by the distribution of molecular weights, the surface glycoproteins of the two murine cells are indistinguishable; however, they differ markedly from the surface glycoproteins of HeLa cells. The extracts of the murine cells wee shown to contain lectin receptor activity as determined by their ability to inhibit the lectin-induced agglutination of the intact cells.