[The trends and preventive strategies of esophageal cancer in high-risk areas of Taihang Mountains, China]

OBJECTIVE

To analyze and predict the trends of incidence and mortality rates of esophageal cancer in areas of Taihang Mountains, and explore the strategies for facilitating the reduction of the incidence and mortality of esophageal cancer.

METHODS

The data were collected from Linxian and Cixian Counties registries between 1988-1997. The trends of the incidence and mortality rates for esophageal cancer had been fitted and predicted by the model of BP (Back Propagation) Neural Networks. Then Linqi Xiang in Linxian County was taken as an example, to determine the power for reducing incidence and mortality of esophageal cancer using endoscopic technology as an early detection and treatment method.

RESULTS

There were slowly declining trends for both incidence and mortality rates during past 10 years in Taihang Mountains. The predicting rates of the esophageal cancer incidence in 2,002 are 115. 70/100,000 for male and 79.88/100,000 for female; mortality rates are 94.00/100,000 and 56.29/100,000 respectively. Both incidence and mortality rates a still in high level. But when using endoscopic technology as an early detection and treatment method, the incidence rate is nearly 1/3 of a control group and the power is 88.30% at the end of eight years. The mortality rate is 1/4 of the control group and power is 89.44% after five years intervention (both powers based on 0.05 significant levels).

CONCLUSIONS

The incidence and mortality rates for esophageal cancer are still on high levels in Taihang Mountains. We should continue to enhance our preventive effort there. After using endoscopic technology as an early detection and treatment method, the incidence and mortality rates will be decreased markedly during 5 to 8 years. It is recommended to implement a large-scale secondary prevention strategy in these areas.

[Vacuole formation and endothelial damage in microvessels after ischemia reperfusion]

AIM

Damage of endothelial cells and adhesion of leukocytes and platelets were studied in rat mesentery microvessels after ischemia reperfusion.

METHODS

The model was made by losing blood and reperfusion from carotid artery in rat. Changes of mesentery microvessels were observed by high magnify microscope.

RESULTS

Leukocytes and platelets adhesions were found in venules and co capillaries 1-3 hours after ischemia reperfusion. Endothelial cells were edema and vascular walls were thickening. Vacuoles formed in intracytoplasm of some vascular endothelium and some bigger endothelial vacuoles prominence toward the luminal surface. Vacuoles liked circle shape and the diameter was 10-30 microm. More vacuoles were found in arterioles, even there were several vacuoles in a arteriole. The biggest vacuole almost occupied 2/3 of vascular lumen.

CONCLUSION

Edema and vacuole formation in vascular endothelium indicate that endothelial cells are injured seriously after ischemia reperfusion.

Developmental study of cytochrome oxidase activity in the brain stem respiratory nuclei of postnatal rats

We utilized cytochrome oxidase (CO) as a marker of neuronal functional activity to examine metabolic changes in brain stem respiratory nuclei of rats from newborn to 21 day of age. The pre-Bötzinger complex (PBC), upper airway motoneurons of nucleus ambiguus (NA(UAM)), ventrolateral nucleus of solitary tract (NTS(VL)), and medial and lateral parabrachial nuclei (PB(M) and PB(L), respectively) were examined at postnatal days (P) 0, 1, 2, 3, 4, 5, 7, 14, and 21. CO histochemistry was performed, and the intensity of CO reaction product was quantitatively analyzed by optical densitometry. In addition, CO histochemistry was combined with neurokinin-1 receptor (NK1R) immunogold-silver staining to doubly label neurons of PBC in P14 animals. The results showed that levels of CO activity generally increased with age in all of the nuclei examined. However, a significant decrease was found in NA(UAM) at P3 (P < 0.01), and a distinct plateau of CO activity was noted at P3 in PBC and at P3 and P4 in NTS(VL), PB(M), and PB(L). Of the neurons examined in PBC, 83% were doubly labeled with CO and NK1R. Of these, CO activity was high in 33.9%, moderate in 27.3%, and light in 38.8% of neurons, suggesting different energy demands in these metabolic groups that may be related to their physiological or synaptic properties. The transient decrease or plateau in CO activity at P3 and P4 implies a period of synaptic adjustment or reorganization during development, when there may be decreased excitatory synaptic drive or increased inhibitory synaptic drive, or both, in these brain stem respiratory nuclei. The adjustment, in turn, may render the system less responsive to respiratory insults. This may bear some relevance to our understanding of pathological events during postnatal development, such as occurs in sudden infant death syndrome.

The sulfonylurea glimepiride regulates intracellular routing of the insulin-receptor complexes through their interaction with specific protein kinase C isoforms

Sulfonylureas may stimulate glucose metabolism by protein kinase C (PKC) activation. Because interaction of insulin receptors with PKC plays an important role in controlling the intracellular sorting of the insulin-receptor complex, we investigated the possibility that the sulfonylurea glimepiride may influence intracellular routing of insulin and its receptor through a mechanism involving PKC, and that changes in these processes may be associated with improved insulin action. Using human hepatoma Hep-G2 cells, we found that glimepiride did not affect insulin binding, insulin receptor isoform expression, and insulin-induced receptor internalization. By contrast, glimepiride significantly increased intracellular dissociation of the insulin-receptor complex, degradation of insulin, recycling of internalized insulin receptors, release of internalized radioactivity, and prevented insulin-induced receptor down-regulation. Association of PKC-betaII and -epsilon with insulin receptors was increased in glimepiride-treated cells. Selective depletion of cellular PKC-betaII and -epsilon by exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA) or treatment of cells with PKC-betaII inhibitor G06976 reversed the effect of glimepiride on intracellular insulin-receptor processing. Glimepiride increased the effects of insulin on glucose incorporation into glycogen by enhancing both sensitivity and maximal efficacy of insulin. Exposing cells to TPA or G06976 inhibitor reversed these effects. Results indicate that glimepiride increases intracellular sorting of the insulin-receptor complex toward the degradative route, which is associated with both an increased association of the insulin receptor with PKCs and improved insulin action. These data suggest a novel mechanism of action of sulfonylurea, which may have a therapeutic impact on the treatment of type 2 diabetes.

The relationship between social support and well-being of rural elderly women

The purpose of this study is to examine the relationship between social support and well-being of rural elderly women. A sample of 284 women aged 60 and older (M = 69.12, SD = 6.40) in a rural area of southern Taiwan completed all interview questions. The Chinese versions of the Personal Resource Questionnaire (PRQ) and the Positive Affect and Negative Affect Scale (PANAS) were used to measure social support and well-being. Content validity of the Chinese versions of the instruments was estimated as satisfactory. The alpha reliability coefficients were .86 for the entire PRQ-85 Part 2 and from .65 to .78 for the subscales. The alpha reliability coefficients were .85 and .65 for the PA subscale and NA subscale respectively. Pearson correlation coefficients were used to examine the relationship between social support and well-being. The findings demonstrated that not only the entire social support but also its five dimensions were positively correlated with positive affect (r ranged from .24 to .48, p < .01) and were inversely correlated with negative affect (r ranged from -.15 to -.21, p < .05 or .01). A substantive intervention design may help verify the effectiveness of social support on elderly women's positive affect and negative affect. Using social support as a strategy to promote these women's well-being, therefore, should be the subject of future study.

Regulation of ligand-induced heterodimerization and coactivator interaction by the activation function-2 domain of the vitamin D receptor

Twenty-epi analogs of 1alpha,25-dihydroxyvitamin D3 (1,25D3) are 100-1000 times more potent transcriptionally than the natural hormone. To determine whether this enhanced activity is mediated through modulation of the dimerization process or through interaction with coactivators, we performed quantitative protein-protein interaction assays with in vitro translated vitamin D receptor (ivtVDR) and fusion proteins containing glutathione-S-transferase (GST) and either the ligand-binding domain of retinoid X receptor (RXRalpha), or the nuclear receptor-interacting domain of the steroid receptor coactivator 1 (SRC-1), or the glucocorticoid receptor-interacting protein 1 (GRIP-1). We found that heterodimerization of the ligand-binding domains of RXRalpha and VDR was primarily deltanoid dependent as was the interaction of VDR with the SRC-1 or with GRIP-1. The ED50 for induction of heterodimerization was 2 nM for 1,25D3 and 0.05 nM for 20-epi-1,25D3. However, the ED50 for induction of VDR interaction with SRC-1 was similar for both 1,25D3 and the 20-epi analog (ED50 = 0.7-1.0 nM) as was the ED50 for ligand-mediated interaction of VDR with GRIP-1 (ED50 = 0.1-0.3 nM). Mutations in heptad 9 diminished both 1,25D3 and the 20-epi analog-mediated dimerization, without changing binding of these ligands to VDR. Mutations in VDR's activation function 2 (AF-2) domain/helix 12 residues diminished the ability of 1,25D3 to induce heterodimerization and interaction with SRC-1. These mutations did not change the ability of 20-epi-1,25D3 to induce dimerization but did diminish its ability to induce interaction with SRC-1. We hypothesize that both the hormone and the analog stabilize receptor conformations that expose VDR's functional interfaces. The mechanisms by which the two ligands expose these functional interfaces differ with respect to participation of the AF-2 domain.

A mammalian cytochrome fused to a chloroplast transit peptide is a functional haemoprotein and is imported into isolated chloroplasts

The small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a major chloroplast stromal protein that is cytosolically synthesized as a precursor with an N-terminal extension, known as the transit sequence or transit peptide (Tp). The Tp is essential for the post-translational uptake of the precursor by the chloroplast. The Tp is thought to influence the conformation of the precursor protein and to facilitate polypeptide translocation across the chloroplast envelope barrier via a Tp-selective translocon. To address these issues we have devised a novel strategy to generate substrate amounts of a chloroplast targeting sequence as a fusion with the chromogenic globular domain of cytochrome b(5) (Cyt). The chimaeric protein is an ideal probe for investigating the conformation of a preprotein and events surrounding protein import into isolated chloroplasts. The Cyt of liver endoplasmic reticulum was fused at its N-terminus with the Tp of the small subunit of Rubisco of Pisum sativum (pea). To enhance its production by clearance from the cytoplasm of Escherichia coli, the chimaera was engineered by further N-terminal linkage of a prokaryotic secretory signal. Expression of this tripartite fusion resulted in mg quantities of the signal sequence-processed Tp-Cyt protein, which was eventually targeted to the membranes. The chromogenic nature of the chimaera and its localization to the bacterial membrane facilitated the biochemical isolation of the precursor in a soluble and functional form. The purified preprotein displayed spectral and enzymic properties that were indistinguishable from the native parental Cyt, implying an absence of observable influence of the Tp on the conformation of the haemoprotein. The chimaeric precursor was imported into the stroma of the isolated chloroplasts in a dose-dependent manner. Import was also strongly dependent upon exogenously supplied ATP. The stromally imported chimaeric precursor protein was processed to a size characteristic of Cyt.

Prognosis and recurrent patterns in bronchioloalveolar carcinoma

STUDY OBJECTIVE

Bronchioloalveolar carcinoma (BAC) is an uncommon pulmonary neoplasm with various radiologic and clinical presentations. In this article, we analyze the initial radiologic findings, TNM stagings, surgical types, and radiologic features of recurrence, and correlate them with patient survival.

DESIGN

A retrospective review of 93 patients who underwent resection for BAC from February 1989 to May 1999.

PATIENTS

There were a total of 153 patients with BAC diagnosed during this period. Among them, 60 patients (39.2%) had diffuse disease and received medical therapy only, and the remaining 93 patients (60.8%), who had localized disease, underwent surgical resection. Patients who received surgical resection were enrolled in this study.

MEASUREMENTS

Data regarding demographics, presentation symptoms, initial radiologic features, surgical type, tumor staging, recurrence status, radiologic patterns of recurrence, and survival were obtained from all patients.

RESULTS

Female patients were significantly younger than male patients. Patients who were female, nonsmoking, undergoing curative surgery, lobectomy, or bilobectomy, and with early tumor staging and no nodal involvement had a better prognosis. Patients with a right lung tumor had a longer survival than those with a left lung tumor, with borderline significance. Among those who suffered from recurrent diseases, a second resection yielded a better survival. Multivariate analysis showed curative surgery, initial surgical type, recurrence status, radiologic patterns of recurrence, and duration from surgical resection to recurrence all had a significant impact on survival.

CONCLUSIONS

Those patients with localized, early-stage BAC who underwent curative surgery had a better survival. Patients with localized recurrence after the initial surgery warranted a second resection. Those with a diffuse radiologic pattern of recurrence and/or early recurrence had a worse prognosis.

[A new flavonoid glycoside from Allium cepa L. var agrogatum Don]

AIM

To investigate the chemical constituents from the bulb stems of the Chinese medicinal plant Allium cepa L. var. agrogatum Don.

METHODS

The crude extracts of the bulb stem were purified by Sephadex LH-20 chromatography. IR, UV, MS, 1H, 13CNMR, 1H-1H COSY, 1H-13C COSY and HMBC spectra were used to determine the structure of the isolated constituents.

RESULTS

A new compound named quercetin 3'-methoxy-4'-O-beta-D-glucopyranoside(I), together with three known compounds kaempferol(II), quercetin 4'-O-beta-D-glucopyranoside(III) and quercetin 3,4'-di-O-beta-D-glucopyranoside(IV) were isolated.

CONCLUSION

Quercetin 3'-methoxy-4'-O-beta-D-glucopyranoside(I) is a new compound, compounds II-IV were isolated from this plant for the first time.

Expression of an anti-CD3 single-chain immunotoxin with a truncated diphtheria toxin in a mutant CHO cell line

ADP-ribosylating immunotoxins are generally expressed in Escherichia coli and then refolded in vitro. Because the efficiency of the in vitro refolding process decreases with the number of protein domains and internal disulfide bonds, these immunotoxins have been generally limited to single-chain monovalent structures. We now show that using the hamster cell line CHO K1 RE1.22c (J. M. Moehring and T. J. Moehring, 1979, Somat. Cell Genet. 5, 453-468) that has been mutated to ADP-ribosylation insensitivity, a level of 4 microg/ml of a truncated anti-T cell immunotoxin, DT390-scFvUCHT1, can be secreted into the medium. This immunotoxin is glycosylated at the two potential N-linked glycosylation sites in the toxin moiety: positions 16-18 in the A chain and residues 235-237 in the B chain. The glycosylated immunotoxin is relatively nontoxic (IC(50) 4.8 x 10(-10) M). Removal of the N-linked oligosaccharides by N-glycosidase F treatment or mutations at the two N-linked glycosylation sites results in a highly active immunotoxin with an IC(50) of 4 x 10(-12) M toward CD3(+) Jurkat cells. This is a 12-fold increase in toxicity over the same immunotoxin harvested from E. coli periplasm without refolding. A single Asn(235) Ala mutation that removed the B chain glycosylation was nearly as toxic as the double mutant. This suggests that B chain glycosylation is the major cause for the loss of toxicity.

Uncoupling ceramide glycosylation by transfection of glucosylceramide synthase antisense reverses adriamycin resistance

Previous work from our laboratory demonstrated that increased competence to glycosylate ceramide conferred adriamycin resistance in MCF-7 breast cancer cells (Liu, Y. Y., Han, T. Y., Giuliano, A. E. , and M. C. Cabot. (1999) J. Biol. Chem. 274, 1140-1146). This was achieved by cellular transfection with glucosylceramide synthase (GCS), the enzyme that converts ceramide to glucosylceramide. With this, we hypothesized that a decrease in cellular ceramide glycosylation would result in heightened drug sensitivity and reverse adriamycin resistance. To down-regulate ceramide glycosylation potential, we transfected adriamycin-resistant breast cancer cells (MCF-7-AdrR) with GCS antisense (asGCS), using a pcDNA 3.1/his A vector and developed a new cell line, MCF-7-AdrR/asGCS. Reverse transcription-polymerase chain reaction assay and Western blot analysis revealed marked decreases in both GCS mRNA and protein in MCF-7-AdrR/asGCS cells compared with the MCF-7-AdrR parental cells. MCF-7-AdrR/asGCS cells exhibited 30% less GCS activity by in vitro enzyme assay (19.7 +/- 1.1 versus 27.4 +/- 2.3 pmol GC/h/microg protein, p < 0.001) and were 28-fold more sensitive to adriamycin (EC(50), 0.44 +/- 0.01 versus 12.4 +/- 0.7 microM, p < 0. 0001). GCS antisense transfected cells were also 2.4-fold more sensitive to C(6)-ceramide compared with parental cells (EC(50) = 4. 0 +/- 0.03 versus 9.6 +/- 0.5 microM, p < 0.0005). Under adriamycin stress, GCS antisense transfected cells compared with parental cells displayed time- and dose-dependent increases in endogenous ceramide and dramatically higher levels of apoptotic effector, caspase-3. Western blotting showed that adriamycin sensitivity, introduced by asGCS gene transfection, was independent of P-glycoprotein and Bcl-2 expression. In summary, this work shows that transfection of GCS antisense tempers the expression of native GCS and restores cell sensitivity to adriamycin. Therefore, limiting the potential to glycosylate ceramide, which is an apoptotic signal in chemotherapy and radiotherapy, provides a promising approach to combat drug resistance.

A chloroplast envelope-transfer sequence functions as an export signal in Escherichia coli

The small subunit precursor of pea ribulose-1,5-bisphosphate carboxylase/oxygenase engineered with prokaryotic elements was expressed in Escherichia coli. This resulted in a dependable level of synthesis of the precursor protein in E. coli. The bacterially synthesised plant precursor protein was translocated from the cytoplasm and targeted to the outer membrane of the envelope zone. During the translocation step, a significant proportion of the precursor was processed to a soluble, mature SSU and found localised in the periplasm. The determined amino acid sequence of the isolated precursor showed that it had a deletion of an arginine residue at position -15 in the transit peptide. Expression of this transit peptide-appended mammalian cytochrome b(5) in E. coli displayed a targeting profile of the chromogenic chimera that was similar to that observed with the plant precursor protein.

[A study on screening and high density cell cultivation of a yeast strain Kluyveromyces with high inulinase yielding and its enzymology properties]

A yeast strain Kluyveromyces with high inulinase yield was screened. The highest inulinase activity of 288.78 u/mL was reached when a high cell density cultivation method was developed for inulinase production. It was 6.8 times higher than the highest level reported in the same species. The activity ratio of its inulinase to invertase was 1/24.72, the Km values were 13.3 mmol/L and 62.6 mmol/L when inulin and sucrose were used as substrate, respectively; The optimum pH value was 4.4, this enzyme also showed a good pH adaptability and stability, i.e. more 90% of the highest level was maintained between pH 3.8 and 5.6; The optimum reaction temperature was 55 degrees C, higher activity was maintained between 50-57.5 degrees C, its half life period was 16 hours at 55 degrees C; It was found for the first time that addition of magnesium ion into the reaction system increased the enzyme activity by 11%.

Acute respiratory distress syndrome following cutaneous exposure to Lysol: a case report

Lysol (mixed cresols) is a brand of popular detergent commonly used to disinfect toilets and floors in Taiwan. We report a patient with acute respiratory failure immediately following chemical burns caused by skin contact with Lysol solution. On admission, chest radiography showed bilateral diffuse pulmonary infiltrates and an arterial blood gas analysis disclosed hypoxemia refractory to a high concentration of oxygen by inhalation. Under the impression of acute respiratory distress syndrome, our patient was admitted to the intensive care unit for respiratory care. Poor clinical improvement was noted, despite aggressive respiratory therapy. High-dose steroid therapy (hydrocortisone 30 mg/kg/day) was administered from the seventh day after mechanical ventilation began and the ratio of arterial partial pressure of oxygen to fractional concentration of oxygen in inspired gas improved thereafter. The amount of steroid was gradually tapered to the maintenance dose and the patient was successfully weaned from the ventilator after a 93-day course of mechanical ventilation.

Glycosylation of ceramide potentiates cellular resistance to tumor necrosis factor-alpha-induced apoptosis

Ceramide, as a second messenger, initiates one of the major signal transduction pathways in tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. Glucosylceramide synthase (GCS) catalyzes glycosylation of ceramide and produces glucosylceramide. By introduction of the GCS gene, cytotoxic resistance to TNF-alpha has been conferred in human breast cancer cells. MCF-7/GCS-transfected cells expressed 4.1-fold higher levels of GCS activity and exhibited a 15-fold (P < 0.0005) greater EC(50) for TNF-alpha, compared with the parental MCF-7 cell line. DNA fragmentation and DNA synthesis studies showed that TNF-alpha had little influence on the induction of apoptosis or on growth arrest in MCF-7/GCS cells, compared to MCF-7 cells. These studies reveal that TNF-alpha resistance in MCF-7/GCS cells is closely related to ceramide hyperglycosylation, a hallmark of this transfected cell line, and resistance was not aligned with changes in TNF receptor 1 expression. This work demonstrates that GCS, which catalyzes ceramide glycosylation, potentiates cytotoxic resistance to TNF-alpha.

Pulmonary alveolar-septal amyloidosis presenting as heart failure with unilateral pleural effusion: a case report

We report a case of pulmonary alveolar-septal amyloidosis associated with chylothorax and paraproteinemia initially presenting as congestive heart failure with unilateral pleural effusion. A 72-year-old man was initially diagnosed with congestive heart failure based on the correlation of clinical manifestation and chest radiography. Concentric left ventricular hypertrophy with mild hypokinesis of the left ventricle was found on cardiac echography. Thoracocentesis was performed for right-sided pleural effusion, which persisted despite medical treatment; chylous exudate was aspirated. Because the etiology of the exudative pleural effusion was undetermined, the patient underwent a thoracotomy that showed pulmonary alveolar-septal amyloidosis. Immunoglobulin M paraproteinemia was identified by serum immunoelectrophoresis. We conclude that it is imperative to search for the cause of an undetermined exudative pleural effusion, with particular attention to chylothorax and amyloidosis as the differential diagnoses.

Ceramide toxicity and metabolism differ in wild-type and multidrug-resistant cancer cells

Previously we demonstrated that multidrug-resistant (MDR) cancer cells have elevated levels of a glycosylated form of ceramide, glucosylceramide. Here we compared ceramide metabolism and ceramide toxicity in MCF-7 and in adriamycin-resistant (MCF-7-AdrR) human breast cancer cells. MCF-7-AdrR cells were resistant to C6-ceramide (1-10 microM); however, in MCF-7 cells treated with C6-ceramide, viability dropped sharply. Ceramide, when supplemented, was not metabolized by MCF-7 cells. In contrast, ceramide was efficiently converted to glucosylceramide by MCF-7-AdrR cells. Analysis of extracellular [3H]ceramide in radiolabeled cells showed that MCF-7-AdrR cells do not have an enhanced capacity to efflux ceramide compared with MCF-7 cells. Triphenylethylene anti-estrogens, known modulators of drug resistance, were effective inhibitors of ceramide conversion to glucosylceramide, suggesting that blocking ceramide metabolism plays a role in chemosensitization. The anti-progestine, RU486, also blocked glucosylceramide synthesis in cells; however, LY117018, a raloxifene analog, was without influence. We propose that an enhanced capacity to glycosylate ceramide as evidenced in MCF-7-AdrR cells, is a molecular determinant of drug resistance, particularly as regards resistance to ceramide-enhancing agents such as anthracyclines, ionizing radiation, and tumor necrosis factor-alpha.

Modification of ceramide metabolism increases cancer cell sensitivity to cytotoxics

In the preceding report we demonstrated that MCF-7-AdrR cells (adriamycin resistant) were insensitive to ceramide, whereas MCF-7 wild-type cells were sensitive. It was also shown that the drug resistant cells had an increased capacity to convert ceramide to glucosylceramide. Here we demonstrate that blocking the conversion of ceramide to glucosylceramide increases MCF-7-AdrR cell sensitivity to ceramide as well as to antitumor agents. Treatment of MCF-7 cells with adriamycin elicited a 5-fold increase in ceramide, and caused oligonucleosomal fragmentation, characteristic to apoptosis. Under similar treatment conditions, ceramide was not generated in MCF-7-AdrR cells. In MCF-7-AdrR cells neither C6-ceramide nor tamoxifen was cytotoxic; however, the addition of tamoxifen to the C6-ceramide treatment regimen reduced cell viability to 42% and elicited apoptosis. Treatment of MCF-7-AdrR cells with Adriamycin promoted an increase in ceramide only if tamoxifen was present, in which case ceramide increased 7-fold, and cell viability decreased to 50%. The employment of another agent, RU486 (Mifepristone), which blocks ceramide glycosylation, increased MCF-7-AdrR cell sensitivity to adriamycin in a dose-dependent manner. Our data show that agents that block ceramide glycosylation potentiate cellular sensitivity to ceramide and to chemotherapeutic drugs, and suggest that the ceramide metabolic pathway is an important target for anticancer drug development.

Multidrug resistance modulators and doxorubicin synergize to elevate ceramide levels and elicit apoptosis in drug-resistant cancer cells

BACKGROUND

To provide insight for the development of more effective clinical agents, the authors attempted to elucidate the mechanisms of action of multidrug resistance (MDR) modulators. Previously, the authors found that MDR modulators blocked the conversion of ceramide to glucosylceramide in MDR cells, thereby enhancing cytotoxicity. Because ceramide is a critical component of the apoptosis signaling cascade, the current study examined the impact of therapy using agents that elicit ceramide formation combined with agents that block ceramide glycosylation.

METHODS

Doxorubicin-resistant human breast carcinoma cells (MCF-7-AdrR) were treated with either doxorubicin, tamoxifen, cyclosporine A, or the cyclosporine A analog SDZ PSC 833 (PSC 833) or with combinations thereof, and ceramide and glucosylceramide metabolisms were measured by cell radiolabeling. Cell viability was quantitated spectrophotometrically and apoptosis was evaluated analyzing DNA integrity by gel electrophoresis.

RESULTS

Whereas cyclosporine A blocked the generation of glucosylceramide in MCF-7-AdrR cells, a chemical cousin, PSC 833, elicited a 3-fold increase in glucosylceramide and a 5-fold increase in ceramide levels at 24 hours. The PSC 833 response was time-dependent(as early as 30 minutes) and dose-dependent (as low as 0.1 microM). The appearance of ceramide foreran the generation of glucosylceramide. Sphingomyelin levels were not decreased in response to PSC 833; however, Fumonisin B1, a ceramide synthase inhibitor, blocked PSC 833-induced ceramide generation. Adding tamoxifen, which blocks ceramide glycosylation, to the PSC 833 regimen boosted ceramide levels 11-fold over controls and caused DNA fragmentation. A 3-component regimen comprised of tamoxifen, doxorubicin, and PSC 833 increased ceramide levels 26-fold and brought cell viability to zero.

CONCLUSIONS

These results demonstrate that MDR modulators can be used separately, in combination, or in conjunction with chemotherapy at clinically relevant concentrations to manipulate cellular ceramide levels and restore sensitivity in the drug resistant setting. As such, this represents a new direction in the treatment of cancer.

Hepatic regeneration in insulin-like growth factor binding protein-1 transgenic mice

BACKGROUND/AIMS

Partial hepatectomy results in activation of genes in the residual liver tissue which serve to restore glucose homeostasis and regenerate liver mass. Expression of insulin-like growth factor binding protein-1 (IGFBP-1) is up-regulated following partial hepatectomy and IGFBP-1 can modulate both the metabolic and mitogenic effects of insulin-like growth factor-1 (IGF-I). The aim of the study was to compare the effects of partial hepatectomy on blood glucose levels and hepatic regeneration in wild-type and transgenic mice which constitutively overexpress IGFBP-1.

METHODS

Hepatic IGFBP-1 mRNA, blood glucose concentrations, liver mass and hepatic DNA synthesis were compared in sham-operated and partially hepatectomized transgenic and wild-type mice.

RESULTS

Hepatic IGFBP-1 mRNA was higher in sham-operated transgenic than wild-type mice, but in both groups of mice, partial hepatectomy was associated with a significant rise in IGFBP-1 mRNA. The absolute decline in blood glucose levels following partial hepatectomy was greater in transgenic mice. Basal DNA synthesis and the response to IGF-I in isolated hepatocytes from both groups of mice were similar, and DNA synthesis in the regenerating liver in vivo was not significantly different in transgenic as compared to wild-type mice: 449.3 +/- 63.9 vs. 321.6 +/- 52.3 cpm/microgram DNA. Hepatic regeneration as measured by liver weight after hepatectomy was not different between transgenic and wild-type mice.

CONCLUSIONS

Constitutive overexpression of IGFBP-1 does not enhance hepatic regeneration and does not prevent the decline in blood glucose following partial hepatectomy.

SDZ PSC 833, the cyclosporine A analogue and multidrug resistance modulator, activates ceramide synthesis and increases vinblastine sensitivity in drug-sensitive and drug-resistant cancer cells

Resistance to chemotherapy is the major cause of cancer treatment failure. Insight into the mechanism of action of agents that modulate multidrug resistance (MDR) is instrumental for the design of more effective treatment modalities. Here we show, using KB-V-1 MDR human epidermoid carcinoma cells and [3H]palmitic acid as metabolic tracer, that the MDR modulator SDZ PSC 833 (PSC 833) activates ceramide synthesis. In a short time course experiment, ceramide was generated as early as 15 min (40% increase) after the addition of PSC 833 (5.0 microM), and by 3 h, [3H]ceramide was >3-fold that of control cells. A 24-h dose-response experiment showed that at 1.0 and 10 microM PSC 833, ceramide levels were 2.5- and 13.6-fold higher, respectively, than in untreated cells. Concomitant with the increase in cellular ceramide was a progressive decrease in cell survival, suggesting that ceramide elicited a cytotoxic response. Analysis of DNA in cells treated with PSC 833 showed oligonucleosomal DNA fragmentation, characteristic of apoptosis. The inclusion of fumonisin B1, a ceramide synthase inhibitor, blocked PSC 833-induced ceramide generation. Assessment of ceramide mass by TLC lipid charring confirmed that PSC 833 markedly enhanced ceramide synthesis, not only in KB-V-1 cells but also in wild-type KB-3-1 cells. The capacity of PSC 833 to reverse drug resistance was demonstrated with vinblastine. Whereas each agent at a concentration of 1.0 microM reduced cell survival by approximately 20%, when PSC 833 and vinblastine were coadministered, cell viability fell to zero. In parallel experiments measuring ceramide metabolism, it was shown that the PSC 833/vinblastine combination synergistically increased cellular ceramide levels. Vinblastine toxicity, also intensified by PSC 833 in wild-type KB-3-1 cells, was as well accompanied by enhanced ceramide formation. These data demonstrate that PSC 833 has mechanisms of action in addition to P-glycoprotein chemotherapy efflux pumping.

Expression of glucosylceramide synthase, converting ceramide to glucosylceramide, confers adriamycin resistance in human breast cancer cells

Multidrug-resistant cancer cells display elevated levels of glucosylceramide (Lavie, Y., Cao, H. T., Volner, A., Lucci, A., Han, T. Y., Geffen, V., Giuliano, A. E., and Cabot, M. C. (1997) J. Biol. Chem. 272, 1682-1687). In this study, we have introduced glucosylceramide synthase (GCS) into wild type MCF-7 breast cancer cells using a retroviral tetracycline-on expression system, and we developed a cell line, MCF-7/GCS. MCF-7/GCS cells expressed an 11-fold higher level of GCS activity compared with the parental cell line. Interestingly, the transfected cells demonstrated strong resistance to adriamycin and to ceramide, whereas both agents were highly cytotoxic to MCF-7 cells. The EC50 values of adriamycin and ceramide were 11-fold (p < 0.0005) and 5-fold (p < 0.005) higher, respectively, in MCF-7/GCS cells compared with MCF-7 cells. Ceramide resistance displayed by MCF-7/GCS cells closely paralleled the activity of expressed GCS with a correlation coefficient of 0.99. In turn, cellular resistance and GCS activity were dependent upon the concentration of the expression mediator doxycycline. Adriamycin resistance in MCF-7/GCS cells was related to the hyperglycosylation of ceramide and was not related to shifts in the levels of either P-glycoprotein or Bcl-2. This work demonstrates that overexpression of GCS, which catalyzes ceramide glycosylation, induces resistance to adriamycin and ceramide in MCF-7 breast cancer cells.

Tamoxifen induces selective membrane association of protein kinase C epsilon in MCF-7 human breast cancer cells

Tamoxifen, a synthetic antiestrogen, is known for its antitumoral action in vivo; however, it is well accepted that many tamoxifen effects are elicited via estrogen receptor-independent routes. Previously, we reported that tamoxifen induces PKC translocation in fibroblasts. In the present study, we investigated the influence of tamoxifen, and several triphenylethylene derivatives, on protein kinase C (PKC) in MCF-7 human breast cancer cells. As measured by Western blot analysis, tamoxifen elicited isozyme-specific membrane association of PKC-epsilon, which was time-dependent (as early as 5 min post-treatment) and dose-dependent (5.0-20 microM). Tamoxifen did not influence translocation of alpha, beta, gamma, delta or zeta PKC isoforms. Structure-activity relationship studies demonstrated chemical requirements for PKC-epsilon translocation, with tamoxifen, 3-OH-tamoxifen and clomiphene being active. Compounds without the basic amino side chain, such as triphenylethylene, or minus a phenyl group, such as N,N-dimethyl-2-[(4-phenylmethyl)phenoxy]ethanamine, were not active. In vitro cell growth assays showed a correlation between agent-induced PKC-epsilon translocation and inhibition of cell growth. Exposure of cells to clomiphene resulted in apoptosis. Since PKC-epsilon has been associated with cell differentiation and cellular growth-related processes, the antiproliferative influence of tamoxifen on MCF-7 cells may be related to the interaction with PKC-epsilon.

Synaptoid contacts between gland cells of the anterior pituitary of the rat

BACKGROUND

There is evidence suggesting cross-talk among gland cells of the anterior pituitary. We had reported a rare form of synaptoid contact between corticotrophs in the anterior pituitary of the dog. We then found similar synaptoid contacts with different characteristics in the rat, as described in the present article.

METHODS

Male Sprague-Dawley rats were used. The anterior pituitaries were prepared for ultrastructural study of substance P immunoreactivity of the anterior pituitary. Routine preembedding immunohistochemical staining was conducted, the sections were embedded in Epon 812 (Serva Feinbiochemica, Heidelberg, New York), and ultrathin sections were prepared.

RESULTS

In the anterior pituitary of the rat, synaptoid contacts were found between corticotrophs and lactotrophs. They appeared very close to typical synapses in the central nervous system, aside from evident weakness of presynaptic density.

CONCLUSIONS

The presence of synaptoid contacts suggests a form of cross-talk between the gland cells in the anterior pituitary of the rat.

Galanin-like immunoreactive nerve fibres in the anterior pituitary of the normal and adrenalectomized rat

Our previous studies have shown the presence of substantial amounts of substance P and calcitonin gene-related peptide-like immunoreactive nerve fibres in the anterior pituitary of the monkey, dog and rat. Furthermore, synaptic relationships have been demonstrated between these nerve fibres and the gland cells in the dog and rat. The substance P and calcitonin gene-related nerve fibres increase in number following adrenalectomy and ovariectomy, respectively. The present study was aimed to investigate the galanin-containing nerve fibres in the anterior pituitary of normal and adrenalectomized rats. The results showed only a small amount of galanin-like immunoreactive nerve fibres in the normal anterior pituitary, which were present among the gland cells as well as along the blood vessels. Following adrenalectomy, the number of galanin-like immunoreactive nerve fibres increased and ramification appeared more frequently. The results substantiate our hypothesis of a dual neural-humoral regulation of the mammalian anterior pituitary gland.