Effect of pre-induction of heat shock proteins on indomethacin-induced small-intestinal lesion in rats

Systemic hyperthermia induces the synthesis of heat shock proteins (HSPs) in several organs. However, the mechanism of induction and the functions of HSPs in the small-intestinal mucosa have not been established. We examined the expression of HSPs in the small-intestinal mucosa after systemic hyperthermia, and evaluated the cytoprotective function of pre-induced HSPs on experimentally induced mucosal damage. HSP expression was investigated by Western blot and densitometric analysis before and after hyperthermia (42.5 degrees C; 20 min). Expression of a 72-kDa heat shock protein (HSP72) and a 73-kDa heat shock protein (HSP73), both of which are endogenous cytoprotectants in vitro significantly increased, peaking 6-9 h after hyperthermia, without any pathologic alterations, whereas the expression of a 60-kDa heat shock protein (HSP60) did not increase. To investigate the influence of pre-induction of HSPs on small-intestinal damage, rats received indomethacin (10 mg/kg; orally) with or without pre-treatment with hyperthermia. Small-intestinal damage caused by indomethacin was not influenced by pre-induction of HSP72 and HSP73. We demonstrated that systemic hyperthermia induced HSP72 and HSP73, although pre-induction of these proteins did not have a cytoprotective function in the small-intestinal damage caused by indomethacin.

Transforming growth factor-beta and hepatocyte growth factor produced by gastric fibroblasts stimulate the invasiveness of scirrhous gastric cancer cells

Scirrhous gastric carcinoma is characterized by cancer cells that infiltrate rapidly in the stroma with extensive growth of fibroblasts. In the present study, we examined the effect of gastric fibroblasts on the invasiveness of a scirrhous gastric cancer cell line, OCUM-2D, using an invasion assay. Gastric fibroblast-derived conditioned medium (CM) significantly stimulated the invasiveness of OCUM-2D cells, as did transforming growth factor-beta (TGF-beta) and hepatocyte growth factor (HGF). The stimulating activity of gastric fibroblast-derived CM was inhibited significantly by anti-TGF-beta neutralizing antibody or anti-HGF neutralizing antibody. TGF-beta and HGF were detected in the gastric fibroblast-derived CM, and TGF-beta receptor and C-met (HGF receptor) were expressed on OCUM-2D cells. Thus, TGF-beta and HGF produced by gastric fibroblasts appear to affect the invasiveness of scirrhous gastric cancer cells. TGF-beta was also detected in the conditioned medium derived from OCUM-2D cells, though HGF was not. TGF-beta appears to affect the invasiveness of OCUM-2D cells in both paracrine and autocrine fashions.

Overexpression of cyclin D1 in rat esophageal carcinogenesis model

Overexpression of cyclin D1 in human esophageal carcinomas has been well documented. The aim of the present study was to assess the expression of cyclin D1 in different types of esophageal epithelial lesions induced by N-nitrosomethylbenzylamine (NMBA) in rats. A total of 30 rats received s.c.-injections, five times/week, of 1.0 mg/kg NMBA for a period of 5 weeks followed by the same dose once per week for another 10 weeks. An additional 15 rats were given saline and used as controls to provide normal epithelium. The tumor incidence was 100% at the termination point of 21 weeks. Seventeen rats (57%) showed nuclear staining for cyclin D1, with a great variation in the intensity, as demonstrated by using an immunohistochemical technique. The cyclin D1 positive indices were in the range of 0% to 60% of the individual cells. Negligible staining was observed for normal esophageal epithelium, with a minimal increase in hyperplastic and dysplastic lesions. A significant elevation of cyclin D1 levels was observed in tumors. However, no significant differences were found between papillomas and carcinomas. The immunohistochemical results were confirmed by western blotting analysis. Tumors, papillomas and carcinomas overexpressing cyclin D1 had elevated proliferating cell nuclear antigen (PCNA) indices (P < 0.05). The correlation coefficient of overexpressions of PCNA and cyclin D1 was r = 0.7 for papillomas, but only r=0.3 for carcinomas. The study thus provides strong evidence of relatively early overexpression of cyclin D1 during tumorigenesis in the present rat esophageal model. Cyclin D1 expression is not simply a direct consequence of increase cell proliferation.

Detection by ligase chain reaction of precore mutant of hepatitis B virus

The clinical diagnosis of infection with the most common precore mutant of hepatitis B virus (HBV), that with a point mutation from guanine to adenine at nucleotide 83 in the precore region, is important because the disease may progress rapidly despite interferon therapy. A practical method to detect this mutant is needed. With the ligase chain reaction (LCR), target DNA sequences can be amplified and single base mutations can be detected. We tried to detect mutant HBV by the LCR alone, but the limit of detection (10(9) copies per tube) was too high. To increase the sensitivity, we used the LCR on DNA already amplified by the polymerase chain reaction (PCR), and tested serum samples from 23 subjects with chronic HBV infection for mutant and wild-type HBV. As few as 10(2) copies per tube could be detected. The results corresponded with the results of nucleotide sequencing for 22 of the 23 patients. The ratio of clones of mutant and total viruses was estimated for each individual by PCR-coupled LCR. Seroconversion could be identified earlier in the illness by an increase in this ratio than by the decrease in HBeAg. We also tested serum samples from 11 patients with acute liver failure by PCR-coupled LCR. Mutant HBV was detected at a low ratio in all 4 patients with acute self-limited hepatitis (AH). Wild-type HBV coexisted with mutant HBV in 6 of 7 patients with fulminant hepatitis (FH), and the mean ratio of mutant to total HBV was significantly higher than that in AH. PCR-coupled LCR could be used to detect mutant HBV and to estimate the ratio of mutant to total viruses.

Rapid dendritic Ca2+ influx is associated with induction of homosynaptic long-term depression in adult rat hippocampus

Homosynaptic long-term depression was induced in area CA1 of adult hippocampus by prolonged low-frequency stimulation (900 pulses at 2 Hz) in the presence of the GABAA receptor antagonist picrotoxin. Using ratio imaging with fura-2, we demonstrate that the induction of this long-term depression is associated with a rapid and transient (approximately 30 s) dendritic Ca2+ increase (approximately 500 nM) dependent on the activation of voltage-gated Ca2+ channels. This transient increase, by itself, was insufficient for long-term depression induction.

Highly hydrogenated dietary soybean oil modifies the responses to polychlorinated biphenyls in rats

The effects of dietary highly hydrogenated soybean oil (HSO) upon the changes caused by dietary polychlorinated biphenyls (PCBs) were examined in rats. Six groups of rats were fed the following diets for 30 d: a 20% soybean oil-containing diet (control diet), a diet in which a half of soybean oil was substituted with HSO (HSO-A diet), a diet in which cellulose powder was replaced with HSO (HSO-B diet) and these diets supplemented with 100 ppm PCBs (control + PCBs, HSO-A + PCBs and HSO-B + PCBs diets). Hepatic concentration of PCBs and relative liver weight were markedly decreased in rats fed with the HSO-A + PCBs diet compared with those fed with the other diets containing PCBs. Liver lipids and liver cholesterol were considerably decreased with a reciprocal increase in fecal sterol excretion by rats fed the HSO-A + PCBs and the HSO-B + PCBs diets compared with those fed with the control + PCBs diet. The fatty acid composition in hepatic phospholipids showed an independent increase of the saturated fatty acid content induced by dietary HSO and PCBs. Dietary PCBs also caused decreases in the amounts of monounsaturated and n-3 polyunsaturated fatty acids. These results suggest that dietary HSO prevents accumulation of PCBs in the liver and promotes the excretion of lipids stimulated by PCBs, accompanied by a change in fatty acid metabolism.

The activation of K-ras gene at an early stage of lung tumorigenesis in mice

To clarify the exact timing of K-ras gene mutational activation in lung tumorigenesis of mice, we applied a sensitive mutant allele specific amplification (MASA) method to pulmonary DNA from urethane-treated mice. The activation of K-ras gene with 61st codon AT mutation was detected in the lungs of mice at day 14 but not day 7 after urethane treatment by MASA. The mutation of MASA products was also checked by XbaI restriction fragment length polymorphism analysis and DNA sequencing. These data suggest that the mutation of K-ras gene in the lungs of mice treated with urethane occurred at the early stage of lung tumorigenesis.

The involvement of polyamines in the proliferation of cultured retinal pigment epithelial cells

PURPOSE

To investigate the involvement of polyamines (putrescine, spermidine, and spermine) in the proliferation of retinal pigment epithelium (RPE) using cultured bovine RPE cells.

METHODS

The polyamine content and the activities of rate-limiting enzymes in polyamine biosynthesis (ornithine decarboxylase [ODC] and S-adenosylmethionine decarboxylase [SAMDC]) and in polyamine biodegradation (spermidine spermine N1-acetyltransferase [SAT]) were measured after proliferative stimulation by 10% fetal calf serum (FCS). DNA synthesis was determined by [3H]thymidine incorporation into the acid-insoluble fraction after the addition of an inhibitor of ODC (alpha-difluoromethylornithine [DFMO]) or SAMDC (methylglyoxal bis[guanylhydrazone] [MGBG]). The effects of exogenous polyamines on DNA synthesis after the additions of inhibitors also were determined.

RESULTS

ODC and SAMDC activities were elevated after stimulation by FCS and reached their peaks 16 hours and 4 hours, respectively, after the addition of FCS. SAT activity was not increased. Polyamine content was increased significantly after stimulation by FCS. DFMO did not inhibit DNA synthesis induced by FCS, and only putrescine content was decreased significantly among polyamines. However, MGBG inhibited DNA synthesis in a dose-dependent manner, and the amounts of spermidine and spermine were decreased significantly. Exogenous polyamines, especially spermine, restored MGBG-induced inhibition of DNA synthesis.

CONCLUSIONS

Polyamines are essential for the proliferation of cultured bovine RPE cells. These data suggest that, of the polyamines, spermine has the greatest effect on DNA synthesis although other polyamines can substitute for spermine at higher concentrations with similar results. As for polyamine metabolism in RPE proliferation, it is possible that SAMDC is the key enzyme rather than ODC.

Suppressive effects of chlorophyllin on mutagen-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) and tumor promoter-dependent ornithine decarboxylase induction in BALB/c 3T3 fibroblast cells

The potentially protective role of chlorophyllin, the sodium and copper salt of chlorophyll a against the initiation and promotion stages in carcinogenesis was studied by in vitro short-term assays. Chlorophyllin showed a dose-dependent suppressive effect on 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indol (Trp-P-1)-induced umu C gene expression of Salmonella typhimurium (TA 1535/pSK 1002) in the presence of metabolizing enzyme mixture. The similar inhibitory effect of chlorophyllin was detected in mitomycin C (MMC)-dependent umu C gene expression in the absence of metabolizing enzyme mixture. Furthermore chlorophyllin also exhibited a dose-dependent inhibition on 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity of 3T3 fibroblast cells at the same concentrations. However, when chlorophyll a isolated from Japanese tea leaves was applied on the same assay systems as a comparative experiment, chlorophyll a showed much weaker activity compared with that of chlorophyllin. The significance of this finding is discussed from the viewpoint of the protective role of chlorophyllin against carcinogenesis.

Suppressive effects of retinoids, carotenoids and antioxidant vitamins on heterocyclic amine-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002)

Effects of retinoids, carotenoids and antioxidant vitamins were studied by mutagen-induced umu C gene expression system in Salmonella typhimurium (TA 1535/pSK 1002). Retinol (vitamin A), retinol acetate and retinoic acid showed remarkable inhibitory activities, whereas retinol palmitate exhibited significant but weak activity for umu C gene expression in tester bacteria induced by 3-amino-3,4-dimethyl-5H-pyrido[4.3-b]indol (Trp-P-1) in the presence of hepatic metabolizing enzymes (S9 mixture). Carotenoids having provitamin A activity (beta-carotene and canthaxanthin) exhibited moderate suppressive effects on the same experimental system. The ranks of suppressive activities were retinol > retinol acetate > retinoic acid > canthaxanthin > beta-carotene > retinol palmitate and their doses for inhibition by 50% (ID50) were estimated to be 1.2 x 10(-7), 3.0 x 10(-7), 5.4 x 10(-7), 1.5 x 10(-6), 4.0 x 10(-5) and 6.0 x 10(-5) M, respectively. However, they did not cause significant inhibition on umu C gene expression induced by direct-acting mutagen (adriamycin or mitomycin C) in the absence of S9 mixture. Inhibition of umu gene expression appears to be due to inhibition of P450-mediated metabolic activation of the heterocyclic amine Trp-P-1. Ascorbic acid (vitamin C) showed weak but significant suppressive activity at high-dose concentrations (3 x 10(-6) - 10(-4)M). However, alpha-tocopherol did not exhibit significant suppression at all dose concentrations. The significance of the experimental results is discussed from the viewpoint of the chemoprevention against genotoxicity associated with carcinogenesis.

[Successful scartectomy and cryoablation for ventricular tachycardia occurring late after correction of tetralogy of Fallot]

A 26-year-old man had a total repair of tetralogy of Fallot at 1 year of age, and had redo surgery for restenosis of the right ventricular outflow tract and small residual VSD at 11 years of age. After the second operation, AV block developed and an endocardial pacemaker system was implanted. For the last 3 years, he had mild febrile episodes, cough, occasional hemoptysis and paroxysmal ventricular tachycardia. Because of his refractory tachycardia and suspected infective endocarditis, he was admitted for further study. Blood culture revealed Peptostreptococcus, echocardiogram showed vegetation around intravenous pacing lead, and electrophysiological study demonstrated delayed potential on the left side of the right ventricular outflow tract. He underwent scartectomy and cryoablation of the focus of the tachycardia which was reconfirmed by epicardial and endocardial mapping during the operation, which involved removal of the endocardial lead and new outflow tract patch repair. His postoperative course was uneventful without any antiarrhythmic drugs. Pathological examination of the scar showed myocardial fibrosis and replacement by fatty tissue which was different from the pathological characters of the arrythmogenic right ventricular dysplasia.

Destruction of cholera toxin receptor on HeLa cell membrane using microbial endoglycoceramidase

The sensitivity of HeLa cells to cholera toxin decreased by Corynebacterium sp. endoglycoceramidase treatment. This endo-enzyme destroyed the cholera toxin receptor, ganglioside G(M1), on the cell surface membrane by liberating intact oligosaccharide from it, which was confirmed by the decrease of intracellular cAMP accumulation and the results of the analysis of released oligosaccharide with a combination of pyridylamination method and HPLC. Fluorescence microscopy using the immunofluorescence method revealed that the amount of cholera toxin attached to the cells decreased in endoglycoceramidase-treated cells. The enzyme acted on cellular glycosphingolipids without addition of any activator protein which is required by other similar enzymes. Corynebacterium endoglycoceramidase is a useful tool to elucidate the function of glycosphingolipids on the cell surface in situ.

[Preanesthetic evaluation of cardiovascular reserve in a patient with dilated cardiomyopathy]

We described an anesthetic management of a patient with abdominal aortic aneurysm associated with dilated cardiomyopathy (DCM) focusing on preanesthetic evaluation of cardiovascular reserve and on intraoperative continuous circulatory monitoring with transesophageal echocardiography (TEE) and continuous cardiac output measurement (CCO). Based on echocardiographic and hemodynamic measurements after a 50 m-walk load, we predicted the allowable range of alteration of preload (LV diastolic dimension; Dd), myocardial performance (arterial blood pressure and ejection fraction) and of heart rate. During anesthesia and operation, we continuously monitored Dd, arterial blood pressure, heart rate and cardiac output, and maintained these variables within the allowable range. The changes in preload after clamping or unclamping of the aorta was promptly reflected by Dd as compared to pulmonary capillary wadge pressure. The CCO was also usuful in detecting abrupt changes in myocardial performance. In conclusion, we suggest preanesthetic stress test to be performed to evaluate cardiovascular reserve and to predict the allowable range of alteration of hemodynamic variables. Continuous monitoring of preload (Dd) by TEE and of myocardial performance by CCO is useful to detect early changes in these variables.

A novel synaptic interaction underlying induction of long-term depression in the area CA1 of adult rat hippocampus

1. We describe a novel synaptic property that regulates induction of homosynaptic long-term depression (LTD), and slowly developing heterosynaptic LTD, of Schaffer collateral-pyramidal cell synapses in adult rat hippocampus. 2. Two independent pathways converging on the same neuron were alternately tested with 0.017 Hz single pulses, and LTD was induced by 900 conditioning stimuli delivered at 2 Hz. All experiments were performed in the presence of the GABA(A) antagonists picrotoxin or bicuculline. 3. After delivery of the 2 Hz stimulation to the homosynaptic pathway, the 0.017 Hz test pulses to the heterosynaptic pathway were interrupted for 25 min. When the test stimulations were resumed, heterosynaptic LTD could not be observed. Homosynaptic LTD also failed to be induced in this protocol. Interruption of test pulses did not itself cause a general increase of synaptic responses. 4. Doubling the frequency of homosynaptic test pulses (to 0.033 Hz) during a 25 min interruption of heterosynaptic stimulus did not preserve homosynaptic LTD. This suggests that the failure of homosynaptic LTD induction seen when the test pulses were interrupted was not caused by a decrease in the number of synaptic inputs at the postsynaptic neuron following conditioning. 5. When only the homosynaptic pathway was involved, with no heterosynaptic stimulation, as in conventional experiments, 2 Hz conditioning successfully induced homosynaptic LTD. 6. We propose that when a heterosynaptic pathway has been recently used, continuous input to that pathway following conditioning is necessary for induction of homosynaptic LTD on the same neuron.

Identification of antimutagenic substances in an extract of edible red alga, Porphyra tenera (Asakusa-nori)

Recently, a relatively strong antimutagenic activity has been detected in the extract of Porphyra tenera (Asakusa-nori in Japanese) which showed a suppressive effect on mutagen-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002 (Okai et al. (1994) Cancer Lett., 87, 25-32). In the present paper, we analyzed the active principles for the antimutagenic activity in an extract of Porphyra tenera and detected three color spots on a silica gel TLC plate which indicated very similar Rf values and absorbance spectra of standard pigments such as beta-carotene, chlorophyll a and lutein. The seaweed pigments recovered from preparative silica gel TLC corresponding to beta-carotene, chlorophyll a and lutein exhibited significant suppressive activities against mutagen-induced umu C gene expression and combined treatment with these pigments showed an additive effect compared with single treatment with each pigment. Furthermore, the standard pigments prepared from other biological sources also exhibited similar anti-mutagenic activities. The significance of this finding is discussed from the protective role of seaweed pigments against mutagenesis probably associated with carcinogenesis.

Phosphorus intake regulates intestinal function and polyamine metabolism in uremia

This study found that 5/6-nephrectomized uremic rats showed secondary hyperparathyroidism as reflected by an increase in their serum parathyroid hormone (PTH) level in association with a decrease in serum 1,25-dihydroxyvitamin D [1,25-(OH)2D]. These changes recovered partially upon phosphorus restriction. Calcium absorption and gene expression of calbindin-D9k were decreased in uremia and were also improved by phosphorus restriction. In uremia, intestinal spermidine/spermine N1-acetyltransferase activity was decreased, while ornithine decarboxylase (ODC) activity and its gene expression were potentiated. Enhancement of c-fos and c-jun gene expressions was also observed in uremia. These phenomena suggest that the intestinal villus may proliferate in uremia. Phosphorus restriction prevented increases in the expression of ODC, c-fos and c-jun observed in uremia. Since phosphorus restriction caused a rise in the serum 1,25-(OH)2D level, the role of 1,25-(OH)2D in uremia-induced intestinal dysfunction was examined. A single injection of 1,25-(OH)2D3 to uremic rats caused an increase in the steady-state calbindin-D9k mRNA level, and decreases in steady state c-fos and ODC mRNA levels, suggesting that the deficiency of 1,25-(OH)2D3 is responsible for intestinal dysfunction in uremia. In conclusion, altered polyamine metabolism caused by 1,25-(OH)2D deficiency is intimately involved in intestinal dysfunction and the development of the proliferative state of the intestinal villus in uremia.

Effect of vitamin E deficiency on inhibition of liver regeneration by long-term administration of alcohol

The effects of vitamin E (VE) deficiency on liver regeneration suppressed by long-term administration of alcohol were studied. Male rats were divided into two groups: the alcohol group and the control group. In addition, each group was subdivided into two groups according to the presence or not of VE. Altogether, four groups were provided: a group maintained on the VE-deficient alcohol diet (group EA), a group maintained on the VE-deficient control diet (group EC), a group maintained on the ordinary alcohol diet (group A), and a group maintained on the ordinary control diet (group C). After pair-feeding for 6 weeks, partial hepatectomy was performed to determine the omithine decarboxylase (ODC) activity, polyamine levels, lipid peroxide levels, and DNA synthesis, DNA synthesis at 24 hr after partial hepatectomy was suppressed significantly in the alcohol administration group, regardless of the presence or not of VE DNA synthesis at 48 hr after partial hepatectomy tended to show low values in group EA, compared with group A. As for the hepatic ODC activity, group EA showed the lowest value at 4 hr after partial hepatectomy. Of polyamines, the putrescine level in group EA at 4 hr after partial hepatectomy was significantly low, compared with the other three groups. The levels of spermidine and spermine decreased by long-term administration of alcohol, but the effect of VE deficiency was not found. The lipid peroxide level increased significantly in the VE-deficient diet administration group, but the effect of alcohol administration was not found. These results suggested that the decrease in putrescine after ODC suppression by VE deficiency in addition to the decrease in spermidine and spermine caused by long-term alcohol administration were concerned with suppression of DNA synthesis later.

All-trans beta-carotene enhances mitogenic responses and ornithine decarboxylase activity of BALB/c 3T3 fibroblast cells induced by tumor promoter and fetal bovine serum but suppresses mutagen-dependent umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002)

Although previous epidemiological studies have indicated that beta-carotene is an important agent for the chemical prevention against carcinogenesis, a recent prospective study has strikingly suggested that supplementation with beta-carotene significantly increased the incidence of some types of cancer (The alpha-Tocopherol and beta-Carotene Cancer Prevention Study Group, New Engl. J. Med., 330 (1994) 1031-1035). To analyze the discrepancy of this problem, the authors analyze the effects of beta-carotene on biochemical and biological events associated with carcinogenesis by in vitro experiments. (1) All-trans beta-carotene enhanced the proliferation and DNA synthesis of BALB/c 3T3 cells induced by a tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and fetal bovine serum, although beta-carotene itself did not show mitogenic activity. (2) All-trans beta-carotene caused a remarkable stimulation for the early induction of ornithine decarboxylase (ODC) activity after the stimulation of TPA and fetal bovine serum. (3) All-trans beta-carotene exhibited significant antimutagenic activity which suppresses umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) induced by a typical mutagen, 2-aminoanthracene (2-AA). These experimental results suggest that all-trans beta-carotene might cause beneficial and harmful effects on different phases of carcinogenesis.

Promotive action of acylated ascorbate on cellular DNA synthesis and growth at low doses in contrast to inhibitory action at high doses or upon combination with hyperthermia

Effects of 6-O-palmitoyl ascorbate (ascorbate) developed to increase the antitumour activity of ascorbic acid on DNA synthesis and proliferation of Ehrlich ascites tumour cells were investigated. Treatment of the cells with the acylated ascorbate at 25-50 microM for 1 h resulted in no effect on DNA synthesis, assayed by pulse incorporation of [3H]thymidine after a culture period of 20 h, but led to 49%-87% enhanced DNA synthesis after 4 days, suggesting that long-term culture is required for promotion by ascorbate to occur. At a dose as high as 75 microM acylated ascorbate, however, cellular DNA synthesis was 64% inhibited after 20 h and 99% after 4 days. The results suggest that acylated ascorbate exhibits a dual action on DNA synthesis: promotion at low doses and inhibition at high doses, both of which are potentiated in a time-dependent manner. In contrast to the above-mentioned results at 37 degrees C, acylated ascorbate at 25-75 microM inhibited but did not promote DNA synthesis at 42 degrees C whatever the culture period. Similar results were exhibited when proliferation of cells cultured for a long period was investigated. At 37 degrees C, 50 microM acylated ascorbate increased the number of the cells to 3.6 times the control values after 8 days and to 1.9 times after 11 days; in contrast, a 75-microM dose decreased the cell number considerably. Combination with hyperthermia (42 degrees C) suppressed the increase and cell growth was completely inhibited at 75 microM.

Overexpression of c-myc messenger RNA in primary and metastatic lesions of carcinoma of the stomach

BACKGROUND

Although c-myc expression in carcinoma of the stomach has been reported to be involved in progression of the disease, little is known about the mechanism or significance of its expression.

STUDY DESIGN

We measured c-myc messenger RNA (mRNA) levels by Northern blot hybridization in 51 primary gastric carcinoma lesions and 15 metastatic lesions accompanied by normal mucosal tissues from the same patients. The extent of c-myc mRNA expression in malignant lesions was determined and compared with that in normal mucosal tissues. The clinical and pathologic significance of c-myc mRNA expression was investigated.

RESULTS

In 35 (68.6 percent) of 51 primary gastric carcinomas c-myc mRNA was overexpressed. Expression was found to be more frequent and stronger in early lesions than in advanced lesions (90 percent, 6.15-fold compared with 54.8 percent, 2.42-fold, p < 0.05). However, c-myc mRNA expression in the primary lesions showed little influence on either the histologic features or the disease progression. C-myc mRNA levels were higher in every metastatic lesion than in the primary lesions (9.89-fold compared with 3.04-fold, p < 0.05).

CONCLUSIONS

These observations suggest that c-myc mRNA overexpression may play a role in the early development of primary lesions as well as in the formation of metastatic lesions of carcinomas of the stomach.