Gene transfer of recombinant endothelial nitric oxide synthase to liver in vivo and in vitro

Endothelial nitric oxide synthase (eNOS)-derived nitric oxide (NO) contributes to hepatic vascular homeostasis. The aim of this study was to examine whether delivery of an adenoviral vector encoding eNOS gene to liver affects vasomotor function in vivo and the mechanism of NO production in vitro. Rats were administered adenoviruses encoding beta-galactosidase (AdCMVLacZ) or eNOS (AdCMVeNOS) via tail vein injection and studied 1 wk later. In animals transduced with AdCMVLacZ, beta-galactosidase activity was increased in the liver, most prominently in hepatocytes. In AdCMVeNOS-transduced animals, eNOS protein levels and catalytic activity were significantly increased. Overexpression of eNOS diminished baseline perfusion pressure and constriction in response to the alpha(1)-agonist methoxamine in the perfused liver. Transduction of cultured hepatocytes with AdCMVeNOS resulted in the targeting of recombinant eNOS to a perinuclear distribution and binding with the NOS-activating protein heat shock protein 90. These events were associated with increased ionomycin-stimulated NO release. In summary, this is the first study to demonstrate successful delivery of the recombinant eNOS gene to liver in vivo and in vitro with ensuing NO production.

Preclinical development of eniluracil: enhancing the therapeutic index and dosing convenience of 5-fluorouracil

Eniluracil (5-ethynyluracil, GW 776, 776C85) is being developed as a novel modulator of 5-fluorouracil (5-FU) for the treatment of cancer. Eniluracil is an effective mechanism-based inactivator of dihydropyrimidine dehydrogenase (DPD), the first enzyme in the catabolic pathway of 5-FU. By temporarily eliminating this prevalent enzyme, eniluracil provides predictable dosing of 5-FU and enables oral administration of 5-FU to replace intravenous bolus and continuously infused dosing. New DPD is synthesized with a half-life of 2.6 days. It also eliminates the formation of problematic 5-FU catabolites. Most importantly, in laboratory animals, eniluracil increases the therapeutic index and absolute efficacy of 5-FU. Accompanying reports in this journal indicate that eniluracil has promising clinical potential.

Measurement of estrogen receptors in intact cells by flow cytometry

BACKGROUND

Estrogen receptor (ER) levels in tumor cells are important for determining the outcome of treatment and the prognosis of breast cancer patients. Flow cytometry is a convenient tool for quantifying the ER in cells, but a more sensitive, reproducible method for immunostaining the ER with anti-ER antibody is needed. Materials and Methods ER-positive human breast cancer cells MCF-7 and T47D, and ER-negative MDA-MBA-321 cells, were fixed and permeabilized by three different protocols. The cells were then stained by indirect immunofluorescence, using two commercial antibodies to ER (MA1-310 and DAKO 1D5), or by direct immunofluorescence using FITC-labeled anti-idiotypic antibody clone 1D(5). The stained cells were analyzed by flow cytometry.

RESULTS

The fixation of cells with a mixture of 0.25% paraformaldehyde and 70% methanol, permeabilization with 0.05% Triton X-100, and increasing antibody and antigen reaction time led to 80-99% of cells being stained with anti-ER antibodies. The relative brightness of ER immunostaining was as follows: anti-idiotypic antibody ID5 > MA1-310 > DAKO 1D5.

CONCLUSIONS

Direct immunofluorescence with the FITC-labeled anti-idiotypic antibody of permeabilized cells resulted in improved specific staining of the ER, as compared to indirect immunofluorescence with anti-ER antibodies of fixed and permeabilized cells. Increasing the length of staining, and treatment of cells with Triton X-100, are both necessary to improve the staining of intracellular antigen for flow cytometric analysis.

[Matrix effects in inductively coupled plasma mass spectrometry by use of organic solvents]

Matrix effects arising from ethanol, propanol, glycerol, acetic acid, ethylenediamine and triethanolamine in inductively coupled plasma mass spectrometry have been studied. Addition of ethanol, propanol, glycerol, acetic acid, ethylenediamine and triethanolamine into solution has an enhancement effect on the signal intensity of analyte with ionization potential between 9 and 11 eV. The ethylenediamine and triethanolamine have higher enhancement effect on the signal intensity of Hg than that of ethanol, propanol, glycerol and acetic acid. Addition of ethylenediamine and triethanolamine into solution has a suppression effect on the signal intensity of Pb and Sr. The mechanism of the enhancement or suppression was investigated. The signal enhancement of Hg in the presence of ethylenediamine and triethanolamine is not caused by improved degree of ionization of Hg and nebulization efficiency. The suppression effects of Pb and Sr in the presence of ethylenediamine and triethanolamine are due to decrease of atomization efficiency of these elements. A method for the determination of Hg in the biological standard samples by ICP-MS was developed.

Synergistic antitumor activity of irinotecan in combination with 5-fluorouracil in rats bearing advanced colorectal cancer: role of drug sequence and dose

The basis for current clinical trials in the treatment of colorectal cancer with the combination of irinotecan (CPT-11) and 5-fluorouracil (FUra) with or without leucovorin (LV) is their proven activity as single agents, their different mechanisms of action, and lack of CPT-11 cross-resistance to previous FUra/LV treatment. The role of drug dose and administration sequence in this combination was studied in vivo using a rat colon tumor model (Ward colon carcinoma); we administered CPT-11 and FUra by i.v. push once a week for four consecutive weeks (weekly x 4), a clinically relevant schedule. The maximum tolerated doses (MTDs) of CPT-11 and FUra administered as single agents were 100 mg/kg/week for both agents. Three different combination administration sequences were evaluated: (a) CPT-11 administered simultaneously with FUra (sequence I); (b) FUra administered 24 h before CPT-11 (sequence II); and (c) CPT-11 administered 24 h before FUra (sequence III). When combining the two drugs at 50% of their respective MTD, the antitumor efficacy was sequence dependent with 62, 38, and 95% complete tumor regression rate for sequences I, II, and III, respectively. For sequences I and II, dose escalation to 75% of the MTD for each drug was paralleled by reversible host toxicity with no significant increase in the antitumor activity of the combination. With sequence III, however, the combination was lethal in 100% of treated animals when the doses of both drugs were at 75% of the MTD or higher. With the sequential combination of CPT-11 followed 24 h later by FUra (sequence III), the high complete tumor regression rate (cure) could be maintained, even when the dose of CPT-11 was reduced to 12.5% of the MTD as long as the doses of FUra was kept at 50 -75 % of the MTD. The data demonstrate that the antitumor activity and toxicity of combining CPT-11 with FUra is highly sequence dependent and that a sequence of CPT-11 preceding FUra is superior with a significant increase in the therapeutic index over the other sequences tested. In addition, the data also demonstrate that toxicity associated with high dose of CPT-11 can be eliminated without loss of the antitumor efficacy by reducing the dose of CPT-11 to at least 50% of its MTD, whereas the dose of FUra is kept at 50-75 % of its MTD.

Small-diameter portacaval H-graft shunt: a paradigm shift back to surgical shunting in the management of variceal bleeding in patients with preserved liver function

Small-diameter portacaval H-graft (SDPHG) shunts are partial portosystemic shunts that control variceal bleeding while preserving nutrient blood flow to the liver, minimizing postoperative encephalopathy and liver failure. Since July 1, 1997, we placed SDPHG shunts in 18 patients (age, 52.1 +/- 2.6 years; range, 35 to 72 years) with cirrhosis (Child's class A, B, and C in 6, 10, and 2 patients, respectively) and refractory variceal bleeding who were not candidates for transplantation. Ten procedures (55.6%) were urgent or emergent. SDPHG shunts effectively reduced the portacaval pressure gradient (18 +/- 3 v 5 +/- 2 mm Hg; P <.05). Surgical times (210 +/- 11 minutes), estimated blood losses (358.3 +/- 107.8 mL), transfusion requirements (0 transfusions in 10 patients; 55.6%; mean, 0.9 +/- 0.3 units), and postoperative hospitalization (7.7 +/- 1.0 days) were excellent. Surgical mortality (30 days) was 0%. During 14. 0 +/- 1.9 months (range, 1.1 to 29.1 months) of follow-up, 4 patients (22.2%) died, including both patients with Child's class C cirrhosis. The cumulative 1-year survival rate was 82.1% (Child's class A, B, and C, 83.3%, 90%, and 0%, respectively). Long-term survivors had significantly lower preoperative Child-Pugh scores compared with nonsurvivors (7.8 +/- 0.3 v 9.5 +/- 1.0; P <.05). Postoperative encephalopathy developed in 3 survivors (20%). Fifteen patients (83.3%) have not experienced rebleeding; shunt failure led to rebleeding in only 1 patient (5.6%). SDPHG shunt placement can be performed with low morbidity and surgical mortality. Nontransplantation candidates with Child's class A and B cirrhosis have excellent long-term survival with this safe, effective, and definitive treatment for refractory variceal bleeding.

[Determination of ultra-trace rare-earth elements in human plasma by inductively coupled plasma mass spectrometry]

Inductively coupled plasma mass spectrometry (ICP-MS), highly sensitive inorgnic analytic technique, fits to determine ultra-trace rare-earth elements in human plasma. Under the optimized conditions detection limits for 15 rare-earth elements are in the range of 0.7 (for Eu)-5.4 (for Gd) ng.L-1. Indium as an internal standard element is used to compensate for matrix suppression effect and sensitivity drift. Three kinds of preparation methods, diluted with 1% HNO3, digested with HNO3-H2O2 and with HNO3-HClO4, are checked and compared, and the former is the simplest way to be measured. The samples diluted with 1% HNO3, stored in 4 degrees C, are very steady for 16 days. With the method, 11 healthy plasma samples in Changchun area of China are analysed.

Contribution of caveolin protein abundance to augmented nitric oxide signaling in conscious dogs with pacing-induced heart failure

Myocardial NO signaling appears elevated in heart failure (HF). Whether this results from increased NO production, induction of the high-output NO synthase (NOS)2 isoform, or changes in NOS regulatory pathways (such as caveolae) remains controversial. We tested the hypothesis that increased abundance of caveolin-3 and/or sarcolemmal caveolae contribute to increased NO signaling in pacing-induced HF. Abundance of caveolin-3 (0.59+/-0.08 versus 0.29+/-0.08 arbitrary units, P = 0.01) but not caveolin-1 was increased in HF compared with control conditions, assessed by Western blot. Additionally, transmission electron microscopy revealed increased caveolae (2. 7+/-0.4 versus 1.3+/-0.3 per micrometer myocyte membrane, P<0.005). The association between caveolin-3 and NOS3 at the sarcolemma and T tubules was unchanged in HF compared with control myocytes. The impact of NOS inhibition with L-N(G)-methylarginine hydrochloride (L-NMMA) on beta-adrenergic inotropy was assessed in conscious dogs before and after HF. In control dogs, dobutamine (5 microg. kg(-1) x min(-1)) increased +dP/dt by 36+/-7%, and this was augmented to 66+/-24% by 20 mg/kg L-NMMA (P = 0.04 versus without L-NMMA, n = 8) but not affected by 10 mg/kg L-NMMA (34+/-10%, P = NS; n = 8). In HF, dobutamine +dP/dt response was depressed (P<0.001 versus control), and increased concentrations were required to match control inotropic responses (10 to 15 microg. kg(-1) x min(-1), 48+/-7%). L-NMMA enhanced +dP/dt responses similarly at 10 mg/kg (61+/-17%, P = 0.02; n = 4) and 20 mg/kg (54+/-7%, P = 0.04; n = 7). Caveolin-3 abundance positively correlated with L-NMMA augmentation of dobutamine inotropic responses in HF (r = 0.9, P = 0.03; n = 4). Thus, in canine pacing-induced HF, expression of caveolin-3 and of sarcolemmal caveolae is increased. This increase is associated with augmented agonist-stimulated NO signaling, likely via a compartmentation effect.

alpha-fluoro-beta-alanine: effects on the antitumor activity and toxicity of 5-fluorouracil

We have shown previously that (R)-5-fluoro-5,6-dihydrouracil (FUraH(2)) attenuates the antitumor activity of 5-fluorouracil (FUra) in rats bearing advanced colorectal carcinoma. Presently, we found that alpha-fluoro-beta-alanine (FBAL), the predominant catabolite of FUra that is formed rapidly via FUraH(2), also decreased the antitumor activity and potentiated the toxicity of FUra. In rats treated with Eniluracil (5-ethynyluracil, GW776), excess FBAL, in a 9:1 ratio to FUra, produced similar effects when administered 1 hr before, simultaneously with, or 2 hr after FUra. FBAL also decreased the antitumor activity of FUra in Eniluracil-treated mice bearing MOPC-315 myeloma at a 9:1 ratio with FUra, but not at a 2:1 ratio. FBAL did not affect the antitumor activity of FUra in mice bearing Colon 38 tumors. We also evaluated the effect of thymidylate synthase (TS) and thymidine kinase (TK) from tumor extracts after FUra +/- Eniluracil +/- FBAL treatment. The activity of TK was similar among the three groups at both 18 and 120 hr. There was also no difference in TS inhibition ( approximately 35%) at 18 hr. However, significantly more TS inhibition was observed in the Eniluracil/FUra group than in the FUra-alone group at 120 hr. FBAL did not alter the effect of Eniluracil/FUra in TS inhibition. Neither FUraH(2) nor FBAL affected the IC(50) of FUra in culture. Thus, the effect of FBAL did not result from direct competition with FUra uptake or immediate anabolism. Either another downstream catabolite that is not formed in cell culture is the active agent, or the effect requires the complexity of a living organism or an established tumor.

Up-regulation of base excision repair activity for 8-hydroxy-2'-deoxyguanosine in the mouse brain after forebrain ischemia-reperfusion

The repair enzyme 8-oxoguanine glycosylase/ apyrimidinic/apurinic lyase (OGG) removes 8-hydroxy-2'deoxyguanosine (oh8dG) in human cells. Our goal was to examine oh8dG-removing activity in the cell nuclei of male C57BL/6 mouse brains treated with either forebrain ischemia-reperfusion (FblR) or sham operations. We found that the OGG activity in nuclear extracts, under the condition in which other nucleases did not destroy the oligodeoxynucleotide duplex, excised oh8dG with the greatest efficiency on the oligodeoxynucleotide duplex containing oh8dG/dC and with less efficiency on the heteroduplex containing oh8dG/dT, oh8dG/dG, or oh8dG/dA. This specificity was the same as for the recombinant type 1 OGG (OGG1) of humans. We observed that the OGG1 peptide and its activity in the mouse brain were significantly increased after 90 min of ischemia and 20-30 min of reperfusion. The increase in the protein level and in the activity of brain OGG1 correlated positively with the elevation of FblR-induced DNA lesions in an indicator gene (the c-fos gene) of the brain. The data suggest a possibility that the OGG1 protein may excise oh8dG in the mouse brain and that the activity of OGG1 may have a functional role in reducing oxidative gene damage in the brain after FblR.

[Malignant transformation of mouse embryonic fibroblast induced by mitochondrial DNA fragments]

OBJECTIVE

To investigate the malignant transforming effect and mechanism of mitochondrial DNA (mtDNA) fragments.

METHODS

Tumorigenicity of mtDNA-transformed mouse embryonic fibroblast (NIH3T3) in nude mice was studied using transgenic techniques. Transformed tumors were detected by pathological examination and hybridization signals of mtDNA probe were analyzed by fluorescence in situ hybridization (FISH) techniques.

RESULTS

Hybridization signals were observed on the nuclei of 18% - 20% NIH 3T3 cells 1 week after mtDNA fragments transforming. Tumor from mtDNA-transformed NIH 3T3 cells was developed in all 8 nude mice (8/8) respectively 2 weeks after the transformation. The pathological characteristics of the tumors developed were similar to that of fibrosarcoma.

CONCLUSIONS

Auto-integration of mtDNA fragments into nuclear genome is a new factor involved in carcinogenesis.

Overexpression of Bax enhances antitumor activity of chemotherapeutic agents in human head and neck squamous cell carcinoma

Overexpression of the Bax protein in human head and neck squamous cell carcinoma A253 cells was reported to result in an increased sensitivity to various chemotherapeutic agents in vitro (Guo et al., Oncol. Res., 11: 91-99, 1999). In the present study, the relationship between Bax expression and response to chemotherapy was further investigated in vitro and in vivo model systems. For in vitro study, A253, A253/Vec (pcDNA3 vector transfectant), and A253/Bax (pcDNA3/Bax transfectant, expressing 50-fold higher Bax protein than A253 and A253/Vec) cells were exposed to various concentrations of raltitrexed (a specific thymidylate synthase inhibitor) and SN-38 (a topoisomerase I inhibitor) for 2 h, and cell growth inhibition was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide clonogenic assay. Compared to A253/Vec, A253/Bax cells exhibited 9.5- and 13.5-fold increases in sensitivity to raltitrexed and SN-38, respectively. For in vivo study, A253/Vec and A253/Bax tumor xenografts were established by s.c. injection of tumor cells into nude mice. The antitumor activity and toxicity of raltitrexed (i.v. push daily for 5 days) and irinotecan (a prodrug of SN-38; i.v. push daily for 3 days) were evaluated. The maximum tolerated doses of raltitrexed and irinotecan were 30 and 100 mg/kg/day, respectively. At the maximum tolerated doses, minimal antitumor activity was observed with raltitrexed, although irinotecan was more active than raltitrexed against A253 or A253/Vec tumors. In contrast, both raltitrexed and irinotecan were significantly more active against A253/Bax xenografts than against A253/Vec xenografts; the yield for complete tumor regression (cure) was 40% and 100% with raltitrexed and irinotecan, respectively, with no significant toxicity. Furthermore, the observed increase of antitumor activity in A253/Bax tumors was associated with an enhanced induction of apoptosis in vivo. The in vivo results demonstrated a proof of the principal concept that selecting up-regulation of the proapoptosis gene Bax can provide the basis for a greater therapeutic efficacy to a variety of chemotherapeutic agents with different structures and mechanisms of action.

Mechanism of action of the dual topoisomerase-I and -II inhibitor TAS-103 and activity against (multi)drug resistant cells

TAS-103 is a recently developed dual inhibitor of topoisomerase-I (topo-I) and topoisomerase-II (topoII). TAS-103 has documented cytotoxicity in vitro and antitumor activity against a variety of mouse, rat, and human xenografts in vivo.

PURPOSE

To determine TAS-103 activity against (multi)drug resistant cells in vitro and to delineate its mechanism of action.

METHODS

TAS-103 was evaluated for activity against three human multidrug-resistant cell lines representing resistance mediated by P-glycoprotein (Pgp)-, multidrug resistance protein (MRP), and lung resistance protein (LRP) as well as one camptothecin-resistant cell line associated with a mutated topo-I enzyme. Drug sensitivity following short (2 h), intermediate (6-8 h) and long term (24 h) exposures were compared. The mechanism of action was studied by evaluating inhibition of topoisomerase-I and -II specific DNA relaxation assays, drug-induced DNA/protein cross-link formation, and competitive DNA intercalation with ethidium bromide.

RESULTS

Increasing the exposure time only modestly potentiated TAS-103 cytotoxicity (3-5 fold) demonstrating a lack of strong exposure duration dependency. TAS-103 cytotoxicity was not affected by the presence of any of the drug resistance mechanisms studied. TAS-103 inhibits topo-I and -II activity in DNA relaxation assays, but in our assay system TAS-103 was found to have only a weak ability to induce DNA-protein crosslinks. DNA migration patterns in agarose gel electrophoresis indicate that TAS-103 can interact directly with DNA. Also its ability to displace ethidium bromide which has intercalated into the DNA provides an indication on the nature of drug-DNA interaction.

CONCLUSIONS

TAS-103 cytotoxicity is not affected by the presence of Pgp, MRP, LRP or mutations in the CAM binding region of the topo-I enzyme and its growth-inhibitory effect appears to be weakly dependent on exposure duration. The presented evidence suggest that the inhibitory effects of TAS-103 on topo-I and -II may in part be related to its DNA binding rather than primarily through stabilization of topo-I or -II intermediates with DNA through specific binding to the enzymes.

[Studies on schedules for human rabies immunization]

OBJECTIVES

To study the feasibility of interferon (INF) plus an immunization schedule of two dose-two dose-one dose (2 - 2 - 1) of rabies vaccine and a simple 2 - 2 - 1 schedule, and to explore immune regulation mechanism of INF.

METHODS

For an IFN plus 2 - 2 - 1 schedule, 5.0, 5.0 and 2.5 I.U. of primary hamster kidney cell rabies vaccine (PHKCV) were injected on the 1st, 7th and 14th day, respectively, and 0.2 million I.U. of IFN-alpha on the 1st day simultaneously. For a simple 2 - 2 - 1 schedule, only 5.0, 5.0 and 2.5 I.U. PHKCV were injected on the 1st, 7th and 14th day, respectively. And, for controls, a routine schedule recommended by WHO was used.

RESULTS

On the 7th day after immunization, their geometric mean titer (GMT) of antibody was 1.71, 1.57 and 1.21 for the above three schedule groups, respectively; on the 14th day, 62.77, 58.79 and 28.96; on the 45th day, 76.64, 72.90 and 62.22. Conversion rate of antibody was 85.00%, 61.11% and 65.00%, respectively on the 7th day, and was 100.00% for all on the 14th day. Proportion of those with protective antibody level was 10.00%, 0.00% and 0.00%, respectively for the three schedule groups, on the 7th day; 100.00%, 100.00% and 95.00%, on the 14th day; and was 100.00% for all on the 45th day. Proportion of those with antibody titer more than 1:1 was 55.00%, 33.33% and 20.00%, respectively, on the 7th day. Adverse reaction rate was 0.00% - 55.00%, without significant difference between three schedule groups.

CONCLUSIONS

Lower dose of IFN could enhance the effect of immune response to rabies vaccine. IFN plus 2 - 2 - 1 rabies vaccine schedule was better than that of simple 2 - 2 - 1 schedule, while the later was better than the routine schedule.

[Determination of the impurities elements in high-purity cadmium by inductively coupled plasma mass spectrometry]

A method for the determination of impurity elements in high purity cadmium by inductively coupled plasma mass spectrometry was developed. The spectral interference arising from Cd was discussed and the magnitude of interference by the polyatomic ion of Cd was compared. The effect of the high concentration Cd on the analyte signal was studied. The results showed that Cd possessed both significant suppression effects on the light mass elements signal and enhancement effects on the heavy mass elements signal, and the effects can be corrected by the use of internal standard elements. In this paper, Y and Bi was employed for the light mass elements and the heavy mass elements, respectively. As, Be, Co, Cu, Ga, Ge, Mn, Mo, Pb, Ni, Sr, Au, Tl, Th, V and U in high purity cadmium were determined. Detection limits are 0.005-0.052 microg x L(-), and the recoveries of standard addition are 82%-108%.

New drugs in therapy of colorectal cancer: preclinical studies

For years, 5-fluorouracil (5-FU) was the only chemotherapeutic agent for the treatment of patients with advanced colorectal cancer. Based on laboratory data, modulation of 5-FU by leucovorin (LV) was proven to be an active alternative. In addition, a number of 5-FU prodrugs and antifolate antimetabolites became available for preclinical and clinical evaluation. With the 5-FU prodrugs, the overall aim was to improve the therapeutic efficacy and selectivity of 5-FU and to provide an oral form of therapy. In preclinical systems, several of the 5-FU prodrugs, eg, capecitabine, uracil/ ftorafur (UFT)/LV, and S- , are active and offer significant therapeutic advantages over 5-FU/LV. A direct and specific new thymidylate synthase (TS) inhibitor, Tomudex (raltitrexed, ZDI694; Zeneca Pharmaceuticals, Macclesfield, UK), is active in several preclinical and clinical settings. The major focus of this report will be on the preclinical development of selected fluoropyrimidine prodrugs.

Involvement of cyclin D1-cdk5 overexpression and MCM3 cleavage in bax-associated spontaneous apoptosis and differentiation in an A253 human head and neck carcinoma xenograft model

Time-dependent ladder-type DNA fragmentation and morphological alterations consistent with apoptosis were observed among A253 human head and neck squamous cell carcinoma (HNSCC) cells in nude mice from 15 to 18 days after transplantation, without any drug treatment. No evidence of ladder-type DNA fragmentation was detected in A253 cells in vitro or in normal nude mouse tissues (skin and muscle). Our aim was to explore molecular factors associated with such spontaneous apoptosis. Bcl-2 protein expression decreased, while bax protein expression increased from day 9 after transplantation. Moreover, altered expression of bcl-2 and bax was accompanied by the increased proteolytic cleavage of poly(ADP-ribose) polymerase (PARP). Time-dependent dephosphorylation of Rb, followed by proteolytic cleavage, was also observed from day 9 after transplantation. The data indicate that the caspase-3 activation and cleavage of Rb protein may represent important steps in the regulation pathway of bax-mediated spontaneous apoptosis. Interestingly, the time-dependent activation of spontaneous apoptosis was almost simultaneous with the induction of differentiation and increased expression of several differentiation-associated regulatory proteins. An increased expression of cyclin D1 and cyclin-dependent kinase-5 (cdk5) was observed from day 9 after transplantation, whereas only slight alteration of cdk4 expression was found. The time-dependent activation of cyclin D1 and cdk5 preceded both the induction of ladder-type DNA fragmentation and increased keratin pearl formation. Furthermore, MCM3 was cleaved early in spontaneous apoptosis and differentiation. Our observations suggest the involvement of cyclin D1-cdk5 overexpression and MCM3 cleavage in bax-mediated spontaneous apoptosis and differentiation in A253 xenografts. P53 and WAF1 proteins were not expressed in the xenografts, indicating that the changes in the regulatory proteins during apoptosis and differentiation were not p53 or WAF1 dependent.

[Effects of strontium in drinking water on the growth of school-age children]

An epidemiological study on the effect of strontium in drinking water on body shape development, bone age, prevalence of caries and dental fluorosis was carried out. The results show: there is a certain promotion on the development of bone age of school-age children, especially of girls, and there is no obvious impact on body shape developing when the concentration of strontium in drinking water is only 10 mg/L. The correlation between strontium in drinking water and the prevalence of caries in children could not get a conclusive evidence in this paper. A further epidemiological investigation is necessary if the role of strontium against caries should be proved.

Dimerization of mitochondrial Bax is associated with increased drug response in Bax-transfected A253 cells

Human head and neck squamous cell carcinoma A253 cells, which do not express p53 and p21 proteins, were engineered to stably express about 50-fold higher level of Bax protein (A253/Bax) than the mock-transfected (A253/vec) or parental cells. Using these cell lines, studies were carried out to evaluate the role of Bax in response to anticancer drugs and to study the associated mechanisms. A253/Bax cells exhibited a significant increase in in vitro sensitivity to various anticancer drugs, including tomudex (9.5-fold), SN-38 (13.8-fold), doxorubicin (7.9-fold), taxol (3.1-fold), 5-FU (2.7-fold), and 5-FU/LV (4.5-fold). Increased level of drug-induced apoptosis was observed in A253/Bax cells in a drug concentration-dependent manner. In untreated A253/Bax cells, Bax was expressed in a monomeric state. Treatment with tomudex induced the formation of Bax dimer in a drug concentration-dependent manner. Dimerization of Bax occurred only in mitochondria, while the cytosolic Bax was retained in the monomeric state. Low level of Bax dimerization was also detected in parental A253 cells following tomudex exposure. In addition, Bax dimer formation was associated with mitochondrial cytochrome c release and activation of caspases in A253/Bax cells. The data suggest that Bax overexpression increases drug response by enhancing drug-induced apoptosis. Furthermore, dimerization of mitochondrial Bax and downstream mechanisms are associated with drug-induced apoptotic cell death and increased drug sensitivity.

Antitumor activity of ZD1694 (tomudex) against human head and neck cancer in nude mouse models: role of dosing schedule and plasma thymidine

We studied the antitumor activity and toxicity of ZD1694 (tomudex), a specific inhibitor of thymidylate synthase (TS), in nude mice bearing human head and neck squamous cell carcinoma A253 and FaDu xenografts. Mice were treated by single i.v. push (i.v. x 1), i.v. push once a week for 3 weeks (weekly x 3), and i.v. push once a day for 5 days (daily x 5), and the maximum tolerated doses (MTDs) of ZD1694 were 300 mg/kg, 60 mg/kg/week, and 30 mg/kg/day, respectively. ZD1694 was moderately active against both A253 and FaDu xenografts. Antitumor activity was schedule-dependent in both tumors: weekly x 3 > or = i.v. x 1 >> daily x 5. In contrast, the rank order of toxicity was daily x 5 >> weekly x 3 > or = i.v. x 1. ZD1694 at the MTD produced 20% complete tumor regression and 20% partial tumor regression (PR) with i.v. x 1 and weekly x 3 schedules and 12-day tumor growth delay with daily x 5 schedule against FaDu xenografts. No complete tumor regression was achieved with ZD1694 with any schedule against A253; a 20% PR, 40% PR, and 10-day tumor growth delay were observed with i.v. x 1, weekly x 3, and daily x 5 schedules, respectively. The data indicate that ZD1694 was slightly more effective against FaDu than against A253. Of interest and potential clinical importance was the observation that ZD1694 was still active at doses lower than the MTD (> or =1/3 MTD), which showed a high therapeutic index and wide safety margin. Study of ZD1694 compared with 5-fluorouracil and 5-fluoro-2'-deoxyuridine at the MTD revealed that the antitumor activity of ZD1694 was comparable with or superior to 5-fluorouracil and 5-fluoro-2'-deoxyuridine against both A253 and FaDu xenografts, with less toxicity. High plasma thymidine in mouse relative to human (approximately 1.3 microM and <0.1 microM, respectively) may complicate the study of antitumor activity and toxicity of TS inhibitors with human tumor xenografts grown in the mouse. To test this hypothesis, we preadministered methoxypolyethyleneglycol-conjugated thymidine phosphorylase (MPEG-TPase; 2500 units/kg/dose) to reduce mouse plasma thymidine, then treated with various doses of ZD1694 using the daily x 5 or i.v. x 1 schedules in the A253 tumor model. MPEG-TPase significantly increased the toxicity of ZD1694; the MTD of ZD1694 plus MPEG-TPase was reduced 3- and 10-fold compared with ZD1694 alone for i.v x 1 and daily x 5 schedules, respectively. However, preadministration of MPEG-TPase did not potentiate the antitumor activity of ZD1694 with either schedule. The data indicate that the study of TS inhibitors in rodent models may not be suitable for predicting a safe dose for clinical study. However, rodent models, particularly human tumor xenografts, are still useful models for evaluation of antitumor activity and schedule selection for TS inhibitors.

[Study on transient infection of T cell lines by M tropic HIV-1 strains]

OBJECTIVE

To reveal the mechanism of transient infection of T cell by HIV-1 isolates of early stages from Yunnan and Xinjiang, China.

METHODS

We made these viruses pass on CXCR4 expressing T cell lines and CCR5 expressing U937 cell line. After having observed the biological phenotype, we analyzed sequences of env gene to find genetic mutations of the strains, and used heteroduplex mobility assay (HMA) to show the complexity of the virus groups.

RESULTS

Sequence analysis indicated that these viruses are M tropic, NSI strains, correlating with their phenotype; they mutated largely through T cell passage, all showed sequence characteristics deviating from M tropic/NSI to different extents. HMA results indicated the complexity of virus groups was low at the very beginning of the passage and kept high later.

CONCLUSION

We concluded that these viruses tried mutating to different directions to adapt the T cell line but all failed. Although env gene correlates with cell tropism, coreceptor usage and HIV syncytium inducing, it may have relationship with the whole genome, whether these phenotypes are present or not. The results imply that there is no T tropic/SI strain in the M topic/NSI virus pool in early infection, it is generated later following continued infection in vivo.

Active-latent glycosylation strategy toward Lewis X pentasaccharide in a form suitable for neoglycoconjugate syntheses

Glycosylation of 4-nitrophenyl 2-acetamido-6-O-tert-butyldiphenylsilyl-2-deoxy-1-thio-beta-D-gluc opyranoside with phenyl 2,3,4,6-tetra-O-benzoyl-1-thio-beta-D-galactopyranoside in the presence of NIS and TfOH as catalyst gave the lactosamine derivative regiospecifically in high yield. Further 3-O-fucosylation with phenyl 2,3,4-tri-O-benzyl-1-thio-beta-L-fucopyranoside using DMTST as promoter afforded the Lex trisaccharide intermediate. The latent glycosyl donor was transformed into its active form (p-acetamidothiophenyl) by reduction with zinc in acetic acid and N-acetylation. Glycosidation with p-nitrothiophenyl lactoside acceptor in the presence of NIS/TfOH as catalyst gave the Lex pentasaccharide in 71% yield.

Promoter activity of mouse kappa opioid receptor gene in transgenic mouse

The biological activity of mouse kappa opioid receptor (KOR) gene promoter was examined in transgenic mice using a beta-galactosidase (lacZ) reporter strategy for the first time. A lacZ cDNA was inserted at the 5th amino acid in the coding region of a mouse KOR genomic segment containing 3 kb of the 5' regulatory region, to generate a Kor-lacZ fusion gene which was then used to generate transgenic mice. The expression of transgene was demonstrated at the RNA level by reverse transcription-polymerase chain reaction (RT-PCR), and at the protein level by in situ lacZ enzyme assay. From studying three independent transgenic mouse lines that express this transgene, it is concluded that Kor-lacZ expression begins at embryonic day 9.5 (E9.5) and increases in several brain areas and neural tube as embryos develop. At E12.5 and E13.5, Kor-lacZ expression is found primarily in the mantle layer of midbrain, hindbrain and medulla oblongata, cranial ganglion and vagus nerve. At E15.5 and E17.5, the transgene is expressed in eye, ear, neopallial cortex, caudate putamen, lateral ventricle, thalamus, hypothalamus and pons. Therefore, the 3 kb 5' regulatory sequence of the mouse KOR gene is functional in transgenic animals and directs a specific expression pattern recapitulating that of the endogenous KOR gene expression during developmental stages. However, in adult animals, this transgene is only expressed in the brain, indicating that the regulatory information for peripheral expression in the adult is not encoded within this 3 kb upstream sequence.

Persistent induction of apoptosis and suppression of mitosis as the basis for curative therapy with S-1, an oral 5-fluorouracil prodrug in a colorectal tumor model

In an effort to improve the therapeutic selectivity of 5-fluorouracil (FUra) against colorectal cancer, S-1, a combination agent including a prodrug of FUra with two modulators, was recently developed by Taiho Pharmaceuticals Co. S-1 is a combination of tegafur (FT), 5-chloro-2,4-hydroxypyridine, and potassium oxonate in the molar ratio of 1.0:0.4:1.0, with the latter two components as inhibitors of dihydropyrimidine dehydrogenase and phosphoribosylpyrophosphate transferase, respectively. In this study, the therapeutic selectivity and efficacy of S-1 (oral) was compared with FT (oral) and FUra (i.v. infusion) in rats bearing advanced colorectal cancer by using clinically relevant schedules. The maximum tolerated doses (MTDs) of S-1, FT, and FUra were 31.5, 200, and 25 mg/kg/d for 7 days and 22.5, 150, and 12.5 mg/kg/d for 28 days, respectively. The therapeutic index of S-1 was 4- to 5-fold higher than that of either FT or FUra. S-1 achieved 100% complete tumor regression (CR) at its MTD in both 7-day and 28-day schedules. Furthermore, the high incidences of stomatitis, alopecia, and diarrhea observed with FUra and FT, were not observed with S-1. In an attempt to understand the basis for the observed superior therapeutic selectivity with S-1, we studied pharmacokinetic analysis of FUra, drug-induced apoptosis, suppression of mitosis, and inhibition of thymidylate synthase (TS) after S-1, FUra, or FT administration. The peak plasma FUra concentrations derived from FUra or S-1 (FT) at comparable MTDs were similar, but the plasma level of FUra was higher with S-1 than with FUra. Induction of high and sustained apoptosis was achieved with S-1. Although the initial level of apoptosis induced by FUra was comparable to S-1, it was not sustained. The sustained level of apoptosis appears to correlate with tumor growth inhibition. Mitotic figures were more greatly suppressed with S-1 treatment than with FUra. Studies on TS inhibition indicated that, although both S-1 and FUra caused a 4- to 6-fold induction of total TS protein, single oral administration of S-1 was superior to 24-h infusion of FUra in suppressing free TS. The data are consistent with the observation that the therapeutic efficacy of S-1 (100% cure) over FUra is associated with high and sustained levels of drug-induced apoptosis, greater suppression of mitosis, and inhibition of free TS in tumor tissues.