Modulation of chloride, potassium and bicarbonate transport by muscarinic receptors in a human adenocarcinoma cell line.
(17/18479)
1. Short-circuit current (I(SC)) responses to carbachol (CCh) were investigated in Colony 1 epithelia, a subpopulation of the HCA-7 adenocarcinoma cell line. In Krebs-Henseleit (KH) buffer, CCh responses consisted of three I(SC) components: an unusual rapid decrease (the 10 s spike) followed by an upward spike at 30 s and a slower transient increase (the 2 min peak). This response was not potentiated by forskolin; rather, CCh inhibited cyclic AMP-stimulated I(SC). 2. In HCO3- free buffer, the decrease in forskolin-elevated I(SC) after CCh was reduced, although the interactions between CCh and forskolin remained at best additive rather than synergistic. When Cl- anions were replaced by gluconate, both Ca2+- and cyclic AMP-mediated electrogenic responses were significantly inhibited. 3. Basolateral Ba2+ (1-10 mM) and 293B (10 microM) selectively inhibited forskolin stimulation of I(SC), without altering the effects of CCh. Under Ba2+- or 293B-treated conditions, CCh responses were potentiated by pretreatment with forskolin. 4. Basolateral charybdotoxin (50 nM) significantly increased the size of the 10 s spike of CCh responses in both KH and HCO3- free medium, without affecting the 2 min peak. The enhanced 10 s spike was inhibited by prior addition of 5 mM apical Ba2+. Charybdotoxin did not affect forskolin responses. 5. In epithelial layers prestimulated with forskolin, the muscarinic antagonists atropine and 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP, both at 100 nM) abolished subsequent 10 microM CCh responses. Following addition of p-fluoro hexahydro-sila-difenidol (pF-HHSiD, 10 microM) or pirenzepine (1 microM), qualitative changes in the CCh response time-profile also indicated a rightward shift of the agonist concentration-response curve; however, 1 microM gallamine had no effect. These results suggest that a single M3-like receptor subtype mediates the secretory response to CCh. 6. It is concluded that CCh and forskolin activate discrete populations of basolateral K+ channels gated by either Ca2+ or cyclic AMP, but that the Cl- permeability of the apical membrane may limit their combined effects on electrogenic Cl- secretion. In addition, CCh activates a Ba2+-sensitive apical K+ conductance leading to electrogenic K+ transport. Both agents may also modulate HCO3- secretion through a mechanism at least partially dependent on carbonic anhydrase. (+info)
Effectiveness of indomethacin as an antitumor agent in Colon 26-bearing conventional and nude mice, and telomerase activity in the tumors.
(18/18479)
The antitumor effect of indomethacin on Colon 26 tumor was investigated in conventional (CDF1) and nude mice (BALB/c nu/nu), and the telomerase activity in the tumor tissues treated with indomethacin was monitored. Growth of Colon 26 tumor was significantly suppressed with indomethacin treatment compared to the controls both in conventional and nude mice. And telomerase activity in the tumor tissues noticeably declined in contrast to normal somatic tissues (testis, liver and colon), which were not affected by indomethacin treatment. We also showed that indomethacin can suppress tumor growth in association with a preferential decrease in telomerase activity in tumor tissues both in conventional and nude mice to the same extent. This study suggests a method for investigating the mechanism of tumor suppression by indomethacin, and suggests that indomethacin might be useful as a novel agent for human cancer therapy. (+info)
Effect of retinoids on AOM-induced colon cancer in rats: modulation of cell proliferation, apoptosis and aberrant crypt foci.
(19/18479)
We have previously reported that the retinoids, 4-(hydroxyphenyl)retinamide (4-HPR) and 9-cis-retinoic acid (RA) prevented azoxymethane (AOM)-induced colon tumors and along with 2-(carboxyphenyl)retinamide (2-CPR) prevented aberrant crypt foci (ACF). In this study, we evaluated the effect of 2-CPR on AOM-induced colon tumors and the effect of the three retinoids on apoptosis and cell proliferation. Male F344 rats were administrated 15 mg/kg AOM at weeks 7 and 8 of age. 2-CPR (315 mg/kg) was administered in the diet starting either 1 week before or at week 12 after the first dose of AOM. The rats continued to receive the 2-CPR until killed at week 46. Unlike the demonstrated prevention of colon cancer by the other two retinoids, both dosing schedules of 2-CPR resulted in an approximate doubling of the yield of colon tumors. In adenomas, 2-CPR, 4-HPR and 9-cis-RA were equally effective in reducing mitotic activity, while only 4-HPR and 9-cis-RA but not 2-CPR enhanced apoptosis. When administered for only the 6 days prior to killing 4-HPR but not 2-CPR decreased the Mitotic Index and increased the Apoptotic Index in adenomas. In non-involved crypts, chronic exposure to 4-HPR and 9-cis-RA in contrast to 2-CPR reduced the Mitotic Index and enhanced the Apoptotic Index. In concurrence with our previous study, both 2-CPR and 4-HPR were very potent in preventing ACF when administered in the diet starting 1 week before the first dose of AOM and continuing for the 5 weeks of the study. Hence, unlike the other two retinoids, 2-CPR, although very potent in preventing ACF, enhanced rather than prevented AOM-induced colon cancer. Furthermore, our results suggest that the effect of 2-CPR on tumor yield is different from 4-HPR and 9-cis-RA because, unlike them, it does not enhance apoptosis. (+info)
Possible carcinogenic effects of X-rays in a transgenerational study with CBA mice.
(20/18479)
A lifetime experiment using 4279 CBA/J mice was carried out to investigate whether the pre-conceptual exposure of sperm cells to X-ray radiation or urethane would result in an increased cancer risk in the untreated progeny, and/or increased susceptibility to cancer following exposure to a promoting agent. The study consisted of four main groups, namely a control group (saline), a urethane group (1 mg/g body wt) and two X-ray radiation groups (1 Gy, 2 Gy). At 1, 3 and 9 weeks after treatment, the males of these four parental groups were mated with untreated virgin females. The offspring of each parental group was divided into two subgroups: one received s.c. urethane (0.1 mg/g body wt once) as a promoter, the other saline, at the age of 6 weeks. All animals were evaluated for the occurrence of tumours. K-ras oncogene and p53 tumour suppressor gene mutations were investigated in frozen lung tumour samples. The female offspring of male parents exposed to X-rays 1 week before their mating showed a trend towards a higher tumour incidence of the haematopoietic system than the F1 controls. In addition, a higher percentage of bronchioloalveolar adenocarcinomas in male offspring born to irradiated paternals mated 1 week after X-ray treatment points to a plausible increased sensitivity of post-meiotic germ cell stages towards transgenerational carcinogenic effects. On the other hand, no increased tumour incidence and malignancy were observed in the offspring born to irradiated paternals mated 3 and 9 weeks after X-ray treatment. Paternal urethane treatment 1, 3 and 9 weeks prior to conception did not result in significantly altered incidence or malignancy of tumours of the lung, liver and haematopoietic tissue in the offspring. K-ras mutations increased during tumour progression from bronchioloalveolar hyperplasia to adenoma. Codon 61 K-ras mutations were more frequent in lung tumours of urethane-promoted progeny from irradiated parents than from control parents. P53 mutations were absent from these lung alterations. (+info)
The expression of beta-catenin in non-small-cell lung cancer: a clinicopathological study.
(21/18479)
AIMS: To investigate the expression of beta-catenin in non-small-cell lung cancer (NSCLC) and its clinical significance. METHODS: 101 patients were surgically treated for NSCLC by lobectomy or pneumectomy with systematic lymph node dissection. Follow up was available in all patients, ranging from 24 to 110 months. Immunostaining of tissue sections from primary tumours and (when present) their lymph node metastases was performed and evaluated using a monoclonal antibody against beta-catenin. Correlations were investigated between beta-catenin immunostaining in primary tumours and E-cadherin immunostaining (data available from a previous study), lymph node stage, and survival. RESULTS: There were significant correlations between scores for beta-catenin immunostaining and E-cadherin immunostaining in primary tumours (p = 0.007), and between the beta-catenin immunostaining score in primary tumours and in their lymph node metastases (p = 0.006). An inverse correlation was found between the beta-catenin immunostaining score in primary tumours and lymph node stage N0, N1, or N2 (p = 0.03). According to the Kaplan-Meier survival estimate, the level of beta-catenin expression in primary tumours was a statistically significant prognostic factor (p = 0.01). CONCLUSIONS: Reduced beta-catenin expression in surgically treated NSCLC is clearly associated with lymph node metastasis and an infavourable prognosis. The existence of a functional relation between E-cadherin and beta-catenin is supported by the results of this clinicopathological study. (+info)
Attenuation by all-trans-retinoic acid of sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats.
(22/18479)
The effect of prolonged administration of all-trans-retinoic acid (RA) on sodium chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labelling and apoptotic indices and immunoreactivity of transforming growth factor (TGF) alpha in the gastric cancers was investigated in Wistar rats. After 25 weeks of carcinogen treatment, the rats were given chow pellets containing 10% sodium chloride and subcutaneous injections of RA at doses of 0.75 or 1.5 mg kg(-1) body weight every other day. In week 52, oral supplementation with sodium chloride significantly increased the incidence of gastric cancers compared with the untreated controls. Long-term administration of RA at both doses significantly reduced the incidence of gastric cancers, which was enhanced by oral administration of sodium chloride. RA at both doses significantly decreased the labelling index and TGF-alpha immunoreactivity of gastric cancers, which were enhanced by administration of sodium chloride, and significantly increased the apoptotic index of cancers, which was lowered by administration of sodium chloride. These findings suggest that RA attenuates gastric carcinogenesis, enhanced by sodium chloride, by increasing apoptosis, decreasing DNA synthesis, and reducing TGF-alpha expression in gastric cancers. (+info)
Induction of reactive oxygen intermediates in human monocytes by tumour cells and their role in spontaneous monocyte cytotoxicity.
(23/18479)
The present study examined the ability of human monocytes to produce reactive oxygen intermediates after a contact with tumour cells. Monocytes generated oxygen radicals, as measured by luminol-enhanced chemiluminescence and superoxide anion production, after stimulation with the tumour, but not with untransformed, cells. The use of specific oxygen radical scavengers and inhibitors, superoxide dismutase, catalase, dimethyl sulphoxide and deferoxamine as well as the myeloperoxidase inhibitor 4-aminobenzoic acid hydrazide, indicated that chemiluminescence was dependent on the production of superoxide anion and hydroxyl radical and the presence of myeloperoxidase. The tumour cell-induced chemiluminescent response of monocytes showed different kinetics from that seen after activation of monocytes with phorbol ester. These results indicate that human monocytes can be directly stimulated by tumour cells for reactive oxygen intermediate production. Spontaneous monocyte-mediated cytotoxicity towards cancer cells was inhibited by superoxide dismutase, catalase, deferoxamine and hydrazide, implicating the role of superoxide anion, hydrogen peroxide, hydroxyl radical and hypohalite. We wish to suggest that so-called 'spontaneous' tumoricidal capacity of freshly isolated human monocytes may in fact be an inducible event associated with generation of reactive oxygen intermediates and perhaps other toxic mediators, resulting from a contact of monocytes with tumour cells. (+info)
The contribution of DNA ploidy to radiation sensitivity in human tumour cell lines.
(24/18479)
The contribution of DNA ploidy to radiation sensitivity was investigated in a group of eight human tumour cell lines. As previous studies suggest, while more aneuploid tumours tend to be more radioresistant, there is no significant relationship between ploidy and radiation sensitivity (SF2). The failure to observe a significant effect of ploidy on radiation sensitivity is due to the complex and multifactorial basis of radiation sensitivity. When we determined the relationship between survival and radiation-induced chromosome aberration frequency, a measure independent of most other modifiers of sensitivity, we observed a direct relationship between ploidy and mean lethal aberration frequency. The mean lethal frequency of aberrations increased from about 1 for diploid cells to about 2 for tetraploid cells. The mean lethal frequency of aberrations was independent of DNA repair variations. These observations demonstrate that changes in DNA ploidy are an important contributor to radiation sensitivity variations in human tumour cell lines. Therefore, any battery of predictive assays should include DNA ploidy measurements. (+info)