Vaccination with leukemia cells expressing cell-surface-associated GM-CSF blocks leukemia induction in immunocompetent mice.

The fundamental basis for immunotherapy of leukemia is that leukemic cells express specific antigens that are not expressed by normal hematopoietic cells. However, the host immune system appears to be tolerant to leukemia cells. To overcome this tolerance, we vaccinated immunocompetent mice with murine leukemia cells (WEHI-3B and BCR-ABL+ 32D cells) transduced with a specifically constructed transmembrane form of granulocyte-macrophage colony-stimulating factor (tmGM-CSF). The transduced cells expressed tmGM-CSF on the cell-surface. To determine whether tmGM-CSF-expressing WEHI-3B leukemia cells would prevent leukemia formation as a vaccine, immunocompetent mice (BALB/c and C3H/HEJ) were immunized with lethally irradiated murine leukemia cells expressing cell-surface tmGM-CSF before challenging mice with murine leukemia cells. Two immunocompetent mouse models were investigated, either WEHI-3B cells in BALB/c mice or BCR-ABL+ 32D cells in C3H/HEJ mouse. The results showed that 100% of WEHI-3B/tmGM-CSF-vaccinated BALB/c mice and about 65% of 32D+ BCR-ABL/tmGM-CSF-vaccinated C3H/HEJ mice were protected from leukemia after leukemia cell challenge, whereas all non-vaccinated mice succumbed to leukemia. Spleen and marrow cell suspensions from vaccinated mice challenged with WEHI-3B cells lacked detectable GFP+ WEHI-3B cells at 82 days post-challenge. A significant delay of death was observed in C3H/HEJ mice challenged with the very aggressive DA-1 cell line expressing BCR-ABL. Vaccination of mice with WEHI-3B/CD40L cells protected 80% of the mice from the WEHI-3B challenge. Notably, 60% of the WEHI-3B/BALB/c mice were also protected from leukemia when WEHI-3B/tmGM-CSF vaccination was carried out after the leukemia challenge. In order to determine whether cellular immunity is involved in this vaccine-mediated protection, either CD4+ or CD8+ T cells were depleted from mice after the WEHI-3B/tmGM-CSF vaccination. The results indicate that CD8+ T-cells mediated the protective immune response provided by the irradiated tmGM-CSF-expressing WEHI-3B cells. In addition, vaccination of nude mice did not provide protection from WEHI-3B leukemia induction. Importantly, 80% of non-vaccinated mice were also protected from a WEHI-3B cell challenge after receiving spleen cells from vaccinated mice 1 day before challenge with leukemia cells. These results indicate that overexpression of tmGM-CSF on the leukemia cell-surface can enhance the recognition of leukemic cells by CD8+ T cells, and can either prevent or significantly delay leukemia induction. These findings suggest that injection of irradiated leukemia cells expressing cell-surface-bound GM-CSF has the potential as an immunological approach to treat leukemia.

Antimutagenic effects of taurine in a bacterial assay system.

Taurine (2-aminoethanesulfonic acid) was evaluated as an antimutagen in the Ames Salmonella tester strain assay. Taurine inhibited mutagenesis by doxorubicin (-74%), bleomycin (-55%), mitomycin C (-56%), and 2-aminofluorene (-52%), but not danthrone or benzo(a)pyrene, in strain TA102. In strain TA98, doxorubicin mutagenicity, but not that of 2-aminofluorene or benzo(a)pyrene, was inhibited by taurine. N-Methyl-N'-nitro-N-nitrosoguanidine (-73%), but not dexon, mutagenicity was inhibited by taurine in strain TA100. Taurine inhibited those mutagens against which it was effective in a dose-related fashion. Taurine was more effective in inhibiting doxorubicin mutagenicity in strain TA102 than its analogues hypotaurine, beta-alanine, and guanidinoethanesulfonic acid or alanine or glycine. The observed inhibition may indicate a role for taurine in modulating the activity of oxidant species.

Determination of potential uterine (conceptus) doses from axial and helical CT scans.

A tissue equivalent Rando Phantom and thermoluminescent dosimeters (TLDs) (LiF) were used to determine potential doses to the uterus at approximately the position of a conceptus from axial and helical CT scans of that region of the body. Doses were measured at the surface of the phantom and at various locations throughout the phantom. The results indicate that measurements taken on the surface of a patient or phantom are generally higher than the level at the location of the uterus within the patient. The results also indicate that the dose to tissue that is 12.7 cm (5 in) out of the direct beam is less than 10% of the dose within the beam. For tissues that are 20 cm (8 in) out of the beam, the dose is approximately 1% of the dose in the beam.

Fecapentaene excretion: aspects of excretion in newborn infants, children, and adult normal subjects and in adults maintained on total parenteral nutrition.

People in developed nations such as the United States and Canada have an increased risk of colon cancer. Fecal mutagens have been detected in the feces of individuals at high risk for colon cancer. We describe a rapid, sensitive, reliable, reproducible high-pressure liquid chromatography (HPLC) method for detecting fecapentaenes, the most active and chief mutagen found in human stool. We found fecapentaene in all the stool samples of adults on typical high-fat, low-fiber Western diets. These fecapentaene concentrations remained largely constant when subjects consumed constant diets. Fecapentaene concentrations were reduced for total-parenteral-nutrition (TPN) patients with severe intestinal malabsorption. This finding with TPN patients may reflect changes in important variables of gut microflora in fecapentaene production. Studies with newborns and children showed that fecapentaenes appeared very early in life but are not present in stool at birth.

Doxorubicin cytotoxicity enhanced by local anesthetics in a human melanoma cell line.

Local anesthetics may influence cell membrane structure and permeability. An established human melanoma cell line (SHG) derived from malignant ascites was used to evaluate the growth-inhibitory effects of local anesthetics (procaine and lidocaine) as well as of doxorubicin at incubation temperatures of 37.5 degrees C and 40 degrees C. In this system, procaine and lidocaine inhibited growth at 0.82 mg/ml and doxorubicin inhibited growth at 28 ng/ml. Noninhibitory concentrations of procaine (0.64 mg/ml) when combined with noninhibitory concentrations of doxorubicin (10 ng/ml) resulted in marked growth inhibition. Incubating temperatures of 40 degrees C enhanced all effects of procaine and doxorubicin on cell growth. These results suggest that clinically achievable concentrations of local anesthetics enhance doxorubicin cytotoxicity.

Abnormal deoxyuridine suppression as a rapid predictor for antimetabolite chemosensitivity: correlation with in vitro tests of growth inhibition.

The deoxyuridine (dU) suppression test, which estimates the activity of the de novo pathway to DNA synthesis from dU, was evaluated as a predictor of antimetabolite growth inhibition. Observations of growth inhibition were made using flask cell culture and soft agar clonogenic assay and correlated with results of the rapidly performed dU suppression test in human (SK-L7) leukemia cells, in methotrexate-sensitive and -resistant murine (L1210) leukemia cells, and in human tumor explants. The concentration of methotrexate resulting in a positive dU suppression test was closely correlated with the methotrexate concentrations required for growth inhibition in flask and soft agar culture systems. The fact that the dU suppression test can be rapidly interpreted in 4 hours compared to the longer period required for clonogenic assay suggests that further evaluation of this procedure as a rapid predictor for clinical antimetabolite response is warranted.

Synergistic cytotoxicity between menadione and dicumarol vs. murine leukemia L1210.

The water-soluble derivative of vitamin K, menadiol sodium bisulfite (K3), and the related anticoagulant dicumarol, inhibited growth of murine leukemia L1210 in liquid suspension culture. K3, but not dicumarol, cytotoxicity was abrogated by 1 mM cysteine. Isobolographic analysis of the effect of K3-dicumarol combinations, in the concentration ranges between 5 and 75 microM, on L1210 growth, indicated synergy between the two drugs. K3 (10 microM) caused a 3-fold stimulation of KCN-resistant O2 consumption by L1210 cells; addition of 50 microM dicumarol did not enhance KCN-resistant O2 consumption further, suggesting that K3-dicumarol synergy in L1210 was not due to dicumarol-mediated augmentation of K3-semiquinone-free radical formation. We examined the effect of dicumarol addition on L1210 cellular metabolites known to be affected by K3, i.e., glutathione, NADPH and ATP. Dicumarol prevented the elevation of the glutathione pool caused by less than or equal to 18 microM K3. K3-dicumarol combinations depleted the NADPH pool significantly, at concentrations of each which did not affect the NADPH pool. No synergistic effect on the ATP pool was observed. Thus, although the mechanism of K3-dicumarol synergy vs. leukemia remained unclear, it was possible that effects on the glutathione and/or NADPH pools contributed. We also investigated the effect of K3 and dicumarol on 45Ca++ transport by L1210 cells because of their effects on glutathione. Neither drug affected 45Ca++ influx or efflux rate constants. However, equilibrium 45Ca++ uptake was suppressed by K3 at concentrations lower than those which depleted glutathione.