Metabolic alterations of zinc and prostaglandins in both human and animal colonic tumor cells.

OBJECTIVE: To understand the relationship between zinc and prostaglandin (PG) metabolisms in inducing colon cancer incidence in human and animals. METHODS: Human colonic tumor and normal cells were obtained from Departments of Surgery and Pathology at the Kaiser Permanente Medical Center, Los Angeles, CA and US VA Medical Center, North Hills, CA. Rat colonic tumor and normal cells were isolated from the rats that received two injections of 50 mg/kg of Azoxymethan (AOM) in 2 weeks and then kept 30 weeks in the animal facility. Then, the effects of zinc on the PGE2 synthesis and PGE2 on zinc metabolism in tumor and normal cells were determined. RESULTS: PGE2 concentrations in both human and AOM-induced rat colonic tumor cells increased compared to those in adjacent normal colonocytes, whereas PGF2 alpha concentrations did not change. Gene expression of inducible form of prostaglandin synthase (PGS-2) is stimulated in rat colonocytes by epidermal growth factor and by tetradecanoyl 13-phorbol acetate (a tumor promoter and mitogen) only in the presence of zinc. PGE2 binding activity of rat enterocytes was maximum at 15 microM of zinc (normal plasma zinc concentration), but PGE2 synthesis activity increased for the first 15 minutes when extracellular zinc concentrations were either higher or lower than the normal extracellular zinc concentration. However, variations in extracellular zinc concentrations did not change the rate of PGF2 alpha synthesis in the normal rat enterocytes. PGE2 significantly increased zinc uptake rates of colonic tumor cells but PGF2 alpha showed only moderate effect. CONCLUSIONS: These results suggest that zinc is required for PGS-2 gene expression, that maintaining an optimal zinc nutriture is important for normal PG synthesis of intestinal cells, and that only PGE2 synthesis mechanisms rather than PGS-2 gene expression are altered in colonic tumor cells resulting in the abnormal zinc nutriture of these cells.

Verapamil preferentially potentiates in-vitro cytotoxicity of vincristine on malignant lymphoid cells.

Verapamil has been shown to overcome acquired drug resistance to vincristine in P388 leukemia both in vitro and in vivo. To study the selectivity of this action, the effect of addition of verapamil on the cytotoxicity of vincristine was studied using lymphocytes from eight patients with chronic lymphocytic leukemia (CLL), lymphoblasts from a T-acute lymphoblastic leukemia (T-ALL) cell line (GM 3639), and peripheral blood lymphocytes (PBL) from eight normal healthy volunteers. Using the differential staining cytotoxicity (DiSC) assay, we demonstrated that verapamil at 1 microM concentration potentiated the in-vitro cytotoxicity of vincristine on CLL and GM 3639 cells in concentrations of 0.04-0.25 micrograms/l. There was however, no enhancement of cytotoxicity noted against the control PBL. The data demonstrate that verapamil preferentially enhances the in-vitro cytotoxicity of vincristine on CLL and GM 3639 cells but no enhancement of cytotoxicity is seen against PBL.

Zinc, calcium, and magnesium metabolism: effects on plasmacytomas in Balb/c mice.

The effects of different amounts of dietary zinc on the Zn absorption rate and on Zn, calcium and magnesium concentrations in tissues of MOPC 104E tumor-bearing Balb/c mice were determined. The Zn absorption rate was inversely related to the amounts of Zn in their diets and was lower than that of nontumor-bearing control mice fed a laboratory mice chow. Zn concentrations of tumor-bearing mice were also low compared with control mice but tumor Zn concentrations, regardless of the concentrations of Zn in the diets, were higher than those of normal tissues of the host other than the pancreas. Ca concentrations in tumor and tissues of tumor-bearing mice were higher than in control animals but Mg concentrations in tissues of tumor-bearing mice appeared to be similar to those of control mice. Results suggest that tumor-bearing mice have a lower intestinal Zn absorption capacity and a higher Zn uptake rate causing other tissues to become hypozincemic and hypercalcemic.

Effect of different levels of dietary zinc on longevity of BALB/c mice inoculated with plasmacytoma MOPC 104E.

The effect of different levels of Zn intake on survival was studied in 6 groups of 4-week-old BALB/c mice inoculated with MOPC 104E tumor cells. The first 3 groups received either a Zn-deficient (0.5 microgram Zn/g), a Zn-supplemented (1 mg Zn/g), or a control diet (37.5 micrograms Zn/g) starting 11 days after tumor inoculation (T11). The remaining 3 groups received the same diets starting the day the tumor was implanted (T0). The mean survival of rats beginning the Zn-deficient diet at T11 was significantly increased compared with that of the control group. However, when the same diet was begun at T0, the mean survival of the Zn-deficient group was significantly reduced; for this group the results probably related to the combined adverse effects from prolonged Zn deficiency and to those effects of the tumor itself. Similarly, excess Zn intake significantly prolonged the mean survival when given at T11. However, excess Zn intake at T0 produced no significant effect on survival, probably because of the elevation of plasma Zn level following oral Zn intake that occurred before the establishment of the tumor or possibly because of the inability of the small intestine to absorb excess Zn at T11 when the tumor was fully developed.

Presence of a serum hemagglutinin (lectinlike factor) in cystic fibrosis homozygotes and heterozygotes.

A lectinlike activity was discovered in serum from 25 patients with CF, 70 obligate heterozygotes (parents), and 18 of 27 siblings (67%) of 675 controls, 4.2% were found to have a positive test for the CF-lectin, approximating the 5% estimated prevalence of CF heterozygotes. The CF-lectin can be detected by dextran-enhanced agglutination of mouse RBCs and confirmed by agglutination inhibition with D-fructose. This simple and inexpensive assay has been found useful to detect carriers of the CF gene, but variability of commercial dextran and some unusual characteristics of the lectin itself have interfered with the successful completion of blind studies. All sugar moieties present in mucus inhibit the agglutination of mouse RBCs by CF serum, implying that the CF-lectin can bind the glycoproteins of mucus. The factor may play a role in the pathogenesis of Cf by stimulating mucus secretion and reacting with mucous glycoproteins to cause their precipitation. Most antibiotics remove or inhibit the CF-lectin activity, suggesting a therapeutic effect of antibiotics unrelated to their antibacterial action. This discovery of a lectinlike factor in the blood of patients with CF and their parents opens a new area for investigation of this devastating disease.

Impaired cellular interactions involving lymphocytes from patients with chronic lymphocytic leukemia and ataxia-telangiectasia.

Abnormal cellular interactions between T and B lymphocytes were identified in patients with CLL and AT. The system employed utilized the detection of a newly recognized lymphokine, NIF-T. This mediator is produced by T lymphocytes as a result of the interaction between T and B cells. Our studies demonstrated impaired T cell function but normal B cell activity in patients with AT with respect to mitogenic stimulation and MLC reactivity. In contrast, patients with B cell CLL had normal T cell function. The leukemic B cells from these patients, however, failed to collaborate with normal T cells in response to mitogens, and they did not participate in MLC reactions. In contrast, lymphocytes from patients with HCL functioned normally with respect to NIF-T production.

Structural and replicative forms of mitochondrial DNA from human leukocytes in relation to age.

The structure and replication of human leukocyte mitochondrial DNA (mtDNA) was investigated in healthy young adult males (23--37 years old), middle-aged males (42--52 years old) with secondary polycythemia, and elderly males (80--89 years old) who exhibited different degrees of age-related disease syndromes. The distribution of the various cell types within the white cell population was within normal limits in all samples. Total mtDNA was isolated in ethidium bromide--CsCl gradients and examined by electron microscopy after spreading by the aqueous and formamide techniques. The individual frequencies of catenated forms ranged from 2 to 6% but showed relatively little change (declining slightly) with age. The individual frequencies of circular dimers varied from 0 to 0.1% in the young adult and polycythemic groups and in 10 out of 12 elderly individuals. One elderly individual had a circular dimer frequency of 0.3% (including a circular molecular of tetramer size) and another had 4.5%. This finding suggest that agerelated cellular pathology may exist in the blood-forming system in some cases. The mode of replication of leukocyte mtDNA agrees well with that described for mouse L cells. There was no evidence of aberrant mtDNA replication as a result of aging.

Factor XIII deficiency in BALB/c mice with plasmacytoma.

These studies examined the fate of Factor XIII (fibrin-stabilizing factor) in mice with plasmacytoma (MOPC-300, MOPC-384, MOPC-467, and J-558). Plasma Factor XIII levels in these mice decreased progressively with tumor expansion. No plasma inhibitors of Factor XIII activity could be detected. Factor XIII was found on plasmacytoma cell membranes and in the cytoplasm of the malignant cells by immunofluorescence. The inverse relationship between tumor load and plasma Factor XIII levels suggested that the fibrin-stabilizing factor was absorbed by the malignant cells.

Detection of fibrin degradation products. A simplified technic.

An agglutination inhibition technic using CrCl3-treated erythrocytes for the quantification of circulating fibrin degradation products in patients with thromboembolic and fibrinolytic states is described.