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C Qian

Publications and source records attributed to C Qian.

At least 73 records · Page 4Linked to original sources
PubMed1998

Loss of imprinting and allele switching of p73 in renal cell carcinoma.

p73, a protein that has substantial structural and functional similarity to p53, has recently been identified. It was found to be monoallelically expressed in all cell lines and normal individuals tested. To elucidate its role in cancer development and as a potential imprinted tumor suppressor, we investigated the allele-specific expression of the human p73 gene in 28 cases of renal cell carcinoma and its imprinting status in fetal pancreatic and thymic tissues. Of 12 informative pairs of renal cell carcinoma and matched normal tissues identified by StyI restriction fragment length polymorphism (RFLP) in exon 2, p73 showed monoallelic expression in 11 out of 12 normal tissues but biallelic expression in 8/12 and switched allele expression in 2/12 of the matched corresponding cancers. An imprinting study of the p73 gene in two families using a newly identified exonic BanI RFLP indicated that expression of p73 was limited to the maternal allele in RNA from fetal pancreas and thymus, demonstrating that p73 is imprinted in at least these two tissues. These findings strongly suggest that loss of imprinting or switching of allelic expression of the p73 gene is associated with the development of renal cell carcinoma.

Alleles↗
PubMed1998

Genomic organization and mutation analysis of p73 in oligodendrogliomas with chromosome 1 p-arm deletions.

p73, a protein having substantial structural and functional similarity to p53, has recently been identified and demonstrated to be a potential tumor suppressor. Its location on human chromosome 1p36.33 implicates p73 as a candidate for neuroblastoma. Like neuroblastoma, oligodendrogliomas also show a high frequency of deletions in chromosome 1p36.3. To determine whether p73 is a potential tumor suppressor gene involved in the development of oligodendrogliomas, we performed mutation analysis of p73 in oligodendrogliomas with chromosome 1 p-arm deletions. We first determined the genomic organization and the intron-exon boundary sequences of the p73 gene by long PCR, vectorette PCR, and Southern hybridization. This gene spans about 65 kb with a large first intron. Primer pairs for the amplification of each of the 13 p73 encoding exons were designed in corresponding introns. The amplicons were then analyzed using the denaturing high-performance liquid chromatography system for mutations in the p73 gene. Twenty oligodendroglioma samples with 1p36.3 deletions were screened, but no mutations were detected except for several polymorphisms. It is thus clear that p73 is not a candidate gene for oligodendroglioma despite its location in the frequently deleted 1p36.3 region.

Chromosomes, Human, Pair 1↗
PubMed1998

Activation of p73 silent allele in lung cancer.

p73, a first p53 relative, has recently been identified and demonstrated to be monoallelically expressed. This protein shows significant amino acid sequence and functional similarities to p53. However, it is unclear whether this protein functions as a tumor suppressor. To elucidate the role of p73 in tumor development, we investigated the expression of the p73 gene in lung cancer. In a comparison between normal lung and tumor tissues, p73 was more highly expressed in tumors. Moreover, using a C/T polymorphism in exon 2 for allele-specific expression analysis in 21 pairs of lung tumors and matched normal tissues, we found that five heterozygous samples exclusively expressed both alleles in tumors while showing monoallelic expression in matched normal tissues. This result was confirmed by single-nucleotide primer extension analysis. Mutation analysis of all 13 coding exons of the gene in 21 lung tumor DNAs revealed several polymorphisms, but no tumor-specific mutations were detected. These findings strongly suggest that p73 may play an important role in lung tumorigenesis through activation of a silent allele and overexpression of wild-type p73 rather than as a tumor suppressor.

Alleles↗
PubMed1998

(+/-)-trans-2-[3-methoxy-4-(4-chlorophenylthioethoxy)-5-(N-methyl-N- hydroxyureidyl)methylphenyl]-5-(3,4, 5-trimethoxyphenyl)tetrahydrofuran (CMI-392), a potent dual 5-lipoxygenase inhibitor and platelet-activating factor receptor antagonist.

By incorporating an N-hydroxyurea functionality onto diaryltetrahydrofurans, a novel series of compounds was investigated as dual 5-lipoxygenese (5-LO) inhibitor and platelet-activating factor (PAF) receptor antagonist. These dual functional compounds were evaluated in vitro for 5-LO inhibition in RBL cell extracts and human whole blood, and PAF receptor antagonism in a receptor binding assay. PAF-induced hemoconcentration and arachidonic acid- and TPA-induced ear edema in mice were used to determine in vivo activities. The structure-activity relationship analysis to define a preclinical lead is presented. (+/-)-trans-2-[3-methoxy-4-(4-chlorophenylthioethoxy)-5-(N-methyl- N-h ydroxyureidyl)methylphenyl]-5-(3,4, 5-trimethoxyphenyl)tetrahydrofuran (40, CMI-392) was selected for further study. In the arachidonic acid-induced mouse ear edema model, 40 was more potent than either zileuton (a 5-LO inhibitor) or BN 50739 (a PAF receptor antagonist), and it demonstrated the same inhibitory effect as a physical combination of the latter two agents. These results suggest that a single compound which both inhibits leukotriene synthesis and blocks PAF receptor binding may provide therapeutic advantages over single-acting agents. The clinical development of compound 40 is in progress.

Animals↗
PubMed1998

Fish mapping of YAC clones at human chromosomal band 7q31.2: identification of YACS spanning FRA7G within the common region of LOH in breast and prostate cancer.

Loss of DNA sequences within human chromosomal band 7q31.2 is frequently observed in a number of different solid tumors including breast, prostate, and ovarian cancer. This chromosomal band also contains the common fragile site, FRA7G. Many of the common fragile sites occur within chromosomal regions that are frequently deleted during tumor formation but their precise position, relative to the chromosome breakpoints and deletions, has not been defined for the majority of the fragile sites. Because the frequency of expression of FRA7G is low, we analyzed the expression of FRA7G in a chromosome 7-only somatic cell hybrid (hamster-human). YAC clones defining a contig spanning 7q31.2 were then used as FISH probes against metaphase spreads prepared from the hybrid cells after aphidicolin induction. This analysis quickly revealed whether a specific YAC clone mapped proximal, distal, or actually spanned the region of decondensation/breakage of FRA7G. By using this approach, we have identified several overlapping YAC clones that clearly span FRA7G. Interestingly, these clones map precisely to the common region of LOH in breast cancer and prostate cancer. In addition, the MET oncogene is contained within the three YACs that span FRA7G.

Animals↗
PubMed1998

Conserved mode of peptidomimetic inhibition and substrate recognition of human cytomegalovirus protease.

Human cytomegalovirus (HCMV) protease belongs to a new class of serine proteases, with a unique polypeptide backbone fold. The crystal structure of the protease in complex with a peptidomimetic inhibitor (based on the natural substrates and covering the P4 to P1' positions) has been determined at 2.7 A resolution. The inhibitor is bound in an extended conformation, forming an anti-parallel beta-sheet with the protease. The P3 and P1 side chains are less accessible to solvent, whereas the P4 and P2 side chains are more exposed. The inhibitor binding mode shows significant similarity to those observed for peptidomimetic inhibitors or substrates of other classes of serine proteases (chymotrypsin and subtilisin). HCMV protease therefore represents example of convergent evolution. In addition, large conformational differences relative to the structure of the free enzyme are observed, which may be important for inhibitor binding.

Amino Acid Sequence↗
PubMed1998

Antitumor effect of allogenic fibroblasts engineered to express Fas ligand (FasL).

Fas ligand is a type II transmembrane protein which can induce apoptosis in Fas-expressing cells. Recent reports indicate that expression of FasL in transplanted cells may cause graft rejection and, on the other hand, tumor cells may lose their tumorigenicity when they are engineered to express FasL. These effects could be related to recruitment of neutrophils by FasL with activation of their cytotoxic machinery. In this study we investigated the antitumor effect of allogenic fibroblasts engineered to express FasL. Fibroblasts engineered to express FasL (PA317/FasL) did not exert toxic effects on transformed liver cell line (BNL) or colon cancer cell line (CT26) in vitro, but they could abrogate their tumorigenicity in vivo. Histological examination of the site of implantation of BNL cells mixed with PA317/FasL revealed massive infiltration of polymorphonuclear neutrophils and mononuclear cells. A specific immune protective effect was observed in animals primed with a mixture of BNL or CT26 and PA317/FasL cells. Rechallenge with tumor cells 14 or 100 days after priming resulted in protection of 100 or 50% of animals, respectively. This protective effect was due to CD8+ cells since depletion of CD8+ led to tumor formation. In addition, treatment of pre-established BNL tumors with a subcutaneous injection of BNL and PA317/FasL cell mixture at a distant site caused significant inhibition of tumor growth. These data demonstrate that allogenic cells engineered with FasL are able to abolish tumor growth and induce specific protective immunity when they are mixed with neoplastic cells.

Animals↗
PubMed1998

In-vitro maturation of human germinal vesicle stage oocytes: role of cumulus cells and epidermal growth factor in the culture medium.

In-vitro maturation (IVM) of oocytes is a promising technique to reduce the costs and avert the side-effects of gonadotrophin stimulation for in-vitro fertilization (IVF). The pregnancy rates from oocytes matured in vitro are much lower than those of in-vivo stimulation cycles indicating that optimization of IVM remains a challenge. Therefore, we investigated the effect of supplementation of the medium with gonadotrophins, oestradiol and epidermal growth factor (EGF) and the effect of retaining or removing the cumulus cells on nuclear and cytoplasmic maturation of immature oocytes. Human germinal vesicle (GV) oocytes obtained after gonadotrophin stimulation for intracytoplasmic sperm injection (ICSI) were cultured in a complex defined medium either supplemented with gonadotrophins, oestradiol and physiological concentrations of EGF (2 ng/ml) or gonadotrophins and oestradiol alone. The cumulus cells were either removed or kept intact. In GV stage oocytes cultured without cumulus (group I) significantly more oocytes reached the metaphase II (MII) stage at 30 h in media supplemented with EGF (64.3 versus 33.9%, P < 0.003). For oocytes cultured with intact cumulus (group II), more oocytes reached MII at 30 h than in group I, but there was no difference in medium with or without EGF supplementation (81.8 and 79.8% respectively). Cytoplasmic maturation of MII oocytes was judged from their capability to activate and fertilize after ICSI. In group I, the rates of activation and normal fertilization were similar. However, in group II, significantly more oocytes underwent normal fertilization in the EGF-supplemented than the unsupplemented group (71.7 versus 45.6%, P < 0.05). The cleavage rates of the fertilized oocytes were similar in the sibling oocyte subgroups cultured with or without EGF supplementation, but the overall cleavage rates were higher in cumulus-intact compared to cumulus-denuded oocytes (88.9 versus 47.8%, P < 0.001). Thus, supplementation of the maturation medium with EGF and maintenance of the cumulus during culture improve the nuclear and cytoplasmic maturation of human oocytes in vitro.

Adult↗
PubMed1998

Effects of beta-amyloid peptide on transient outward potassium current of acutely dissociated hippocampal neurons in CA1 sector in rats.

OBJECTIVE: To explore the mechanism of beta-amyloid peptide (beta-AP) in Alzheimer's disease at ionic channel level. METHODS: Hippocampal CA1 neurons of 7-21 days' rats were acutely dissociated and the effects of beta-AP on transient outward potassium current were observed by a whole-cell recording patch clamp technique. RESULTS: beta-AP can significantly block transient potassium current in dose-dependent, time-dependent and partly voltage-dependent manners. CONCLUSION: beta-AP may decrease the membrane conductance of K+ channels in hippocampal neurons, playing an important role in the pathophysiological mechanism of Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed1998

[Preliminary study on the correlation between neovasculature and metastatic nasopharyngeal carcinoma by computer image analysis].

OBJECTIVE: To investigate the significance of neoangiogenesis in metastasis of nasopharyngeal carcinoma (NPC) so as to clarify further the role of neovascularity in evaluating the prognosis of NPC and the probability of antiangiogenesis in preventing distant metastasis of NPC. METHODS: Fifty-two patients with metastatic NPC were selected and strictly matched in sex, age, T stage, and N stage with another 52 patients with non-metastatic NPC and survived a long time. The tumor tissues of all 104 patients were retrived for computer-assisted, immunohistochemical analysis of tumor vasculature. RESULTS: Counts of microvessel and relative area of all microvessels per image were significantly higher in metastatic NPCs than those of curable, non-metastatic NPCs; while average area of microvessel and average perimeter of microvessel in metastatic NPCs were smaller than those of the opposite. No significant difference in any microvessel parameter had been found among various types of metastasis. CONCLUSIONS: The alterations of microvessel parameters bore significant relationships with metastases of NPC. Evaluation of neovascularity with computer image analysis may help in estimating the prognosis of NPC and in finding out the indications for aggressive multimodal treatments. Angiogenesis inhibitors might be helpful in preventing NPC from distant metastasis.

Adult↗
PubMed1997

Experiences from the structure determination of human cytomegalovirus protease.

Several obstacles were encountered and overcome during the structure determination of human cytomegalovirus protease. Dehydration of crystals, by exposing them to higher concentrations of the precipitant, reduced the mosaicity of the crystals and may have also resolved their microscopic twinning. The initial phase information was obtained with the selenomethionyl multiple-wavelength anomalous diffraction technique. However, site-specific mutagenesis was required to introduce extra Met residues into the protease. The phase information had to be improved by non-crystallographic symmetry averaging, initially among three 'crystal forms'. A change in the composition of the artificial mother liquor led to a significant improvement, from 3.0 and 2.0 A resolution, in the diffraction quality of the crystals. The experiences reported here may prove useful to structure determination of other proteins.

Journal Article↗
PubMed1997

Gene transfer and therapy with adenoviral vector in rats with diethylnitrosamine-induced hepatocellular carcinoma.

In rats with diethylnitrosamine (DENA)-induced hepatocellular carcinoma (HCC), we studied in vivo gene transfer efficiency using intraportal injections of recombinant adenovirus carrying the lacZ reporter gene (AdCMVlacZ) and the therapeutic efficacy of adenovirus-mediated transfer of the thymidine kinase gene of the herpes simplex virus (HSV-tk) followed by ganciclovir (GCV) administration. DENA was very effective in inducing HCC but also stimulated nontumor cell replication, as shown by proliferating cell nuclear antigen (PCNA) staining. The study of in vivo gene transfer efficiency in tumor-bearing rats showed that nontumor tissue and small tumor nodules were transduced effectively whereas a poor transduction rate was noted in large tumor nodules. Concerning therapeutic efficacy, three groups of rats with established HCC were studied: group A and B received intraportally recombinant adenovirus carrying HSV-tk (AdCMVtk) or AdCMVlacZ, respectively, and 2 days after GCV was given intraperitoneally for 9 days; group C received only saline. Of the rats from groups B and C, 100% and 93% respectively, exhibited multiple HCC tumor nodules at end of the study. In contrast, a complete regression of tumor was observed in 63% of animals from group A. This group showed significant elevation of serum transaminases and a diffuse hepatotoxic lesion in liver tissue; histological signs of regeneration were observed in surviving animals. Nine out of 19 rats from group A died during the treatment period. We conclude that (i) in the DENA model of HCC, tumoral cells can be destroyed in vivo by the HSV-tk/GCV system despite poor transduction of large tumor nodules, suggesting that toxic metabolites generated by nontumor cells may exert a bystander effect on tumor tissue; (ii) significant hepatoxicity and a high mortality rate occurred in HSV-tk/GCV-treated rats; these side effects appear to be due to the fact that in DENA-treated livers enhanced cell proliferation was present not only in tumor nodules but also in nontumor parenchyma, leading to GCV sensitization of both tissues; (iii) our results have implications concerning the efficacy and potential risks of the HSV-tk/GCV system in the treatment of human HCC.

Adenoviridae↗
PubMed1997

A phase I/II study of external beam radiation, brachytherapy and concurrent chemotherapy in localized cancer of the esophagus (RTOG 92-07): preliminary toxicity report.

PURPOSE: A multi-institutional, prospective study was designed to determine the feasibility and tolerance of external beam irradiation plus concurrent chemotherapy and esophageal brachytherapy (EB) in a potentially curable group of patients with adenocarcinoma or squamous cell carcinoma of the esophagus. METHODS AND MATERIALS: Planned treatment was 50 Gy external beam radiation (25 fractions/5 weeks) followed 2 weeks later by EB [either high dose rate (HDR) 5 Gy, weeks 8, 9, and 10, for a total of 15 Gy, or low dose rate (LDR) 20 Gy, week 8]. The protocol was later revised to delete the LDR alternative, owing to poor accrual, and to decrease the HDR dose to 10 Gy (i.e. 5 Gy, weeks 8 and 9). Chemotherapy was given weeks 1, 5, 8, and 11 with cisplatin 75 mg/m2 and 5-fluorouracil 1000 mg2/m per 24 h, 96-h infusion. The study closed in January 1995 after 56 patients had been entered on the HDR arm. Six patients were declared ineligible owing to tumor extension to the gastroesophageal junction (three patients) or involved celiac lymph nodes (three patients). Of the 50 eligible patients, the planned EB dose was 15 and 10 Gy in 40 and 10 patients, respectively. Forty-six (92%) of the eligible patients had squamous histology, and three (6%) adenocarcinoma. RESULTS: Life-threatening toxicity or treatment-related death occurred in 13 (26%) and 4 (8%) of the 50 eligible patients, respectively. Treatment-related esophageal fistulas occurred in three patients (12% overall, 14% of patients starting EB) at 0.5-6.2 months from the first day of brachytherapy, leading to death in three. The fourth death was secondary to renal toxicity and infection attributed to chemotherapy. No correlation was found between the development of fistula and location of primary tumor, brachytherapy active length or applicator diameter. So far, 5 of the 6 treatment-related fistulas have occurred following 15 Gy EB. The other fistula occurred after only 5 Gy of a planned 15 Gy was delivered. CONCLUSION: Thirty-five patients (70%) were able to complete external beam, EB, and at least two courses of chemotherapy. Estimated survival rate at 12 months is 48%, with an estimated 11-month median survival rate. Survival following external beam radiation plus concurrent chemotherapy and EB does not appear to be significantly different from survival seen following external beam radiation and chemotherapy only. The development of six fistulas in the 35 patients completing EB is of concern. Based on the high incidence of fistulas, we urge extreme caution in employing EB as a boost following concurrent external beam radiation and chemotherapy.

Adenocarcinoma↗
PubMed1997

The gene for microfibril-associated protein-1 (MFAP1) is located several megabases centromeric to FBN1 and is not mutated in Marfan syndrome.

Linkage studies have mapped the Marfan syndrome (MFS) locus to chromosome region 15q15-q21 with no convincing evidence of genetic heterogeneity. The fibrillin-1 (FBN1) gene, located at 15q21.1, that encodes the major component of the defective microfibrils, has been identified as the gene for MFS. However, extensive mutation screening in many laboratories has detected FBN1 mutations in only a fraction of MFS probands studied, leading to the hypothesis that the missing mutations could involve another microfibril gene located in the same region. Recently, the gene for microfibril-associated protein-1 (MFAP1, also called AMP) has been isolated and mapped to the 15q15-q21 region that overlaps the location of the FBN1 gene. Here we report that the two loci are physically close, making MFAP1 an alternative positional candidate gene for MFS. We have carried out MFAP1 mutation screening and gene expression analysis in 48 probands with MFS or related phenotypes who were selected for this study because their fibroblast cultures synthesized fibrillin at normal levels. No MFAP1 mutations were identified, and transcription occurred equally from both alleles. We conclude that the MFAP1 locus is not a reservoir for the hidden MFS mutations.

Base Sequence↗
PubMed1997

Sperm-associated oocyte-activating factor is released from the spermatozoon within 30 minutes after injection as a result of the sperm-oocyte interaction.

We have previously shown that sperm plasma membrane damage makes the sperm plasma membrane permeable and the sperm nucleus accessible for low molecular weight molecules such as eosin and dithiothreitol. In the present study, we investigated whether this damage is associated with a passive release of the sperm-associated oocyte activating factor (SAOAF) from the spermatozoon and, if so, its time sequence. In a first study, human oocytes remaining unfertilized after conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) and freshly ovulated mouse oocytes were injected with a whole spermatozoon or a sperm head respectively. They were randomly allocated to one of three groups: oocytes in group 1 were injected with a spermatozoon immobilized or sperm head detached immediately prior to the injection; oocytes in group 2 were injected with a spermatozoon immobilized or sperm head detached 2-4 h before injection; oocytes in group 3 were injected with a spermatozoon or sperm head that had been subjected to heat treatment. The activation rate of oocytes injected with a spermatozoon or sperm head was the same for groups 1 and 2, and significantly higher than in group 3 (P < 0.001). In a second series of experiments, human oocytes remaining unfertilized after IVF or ICSI were injected with a sperm head that was subsequently removed from the ooplasm 20-30 min after injection. The activation rates were compared to that of oocytes injected with heat-treated spermatozoa which subsequently were removed from the ooplasm. We found that the removal of the spermatozoon 30 min after injection did not prevent oocyte activation. Our data indicate that the initial damage to the sperm plasma membrane induced at immobilization, although essential for the onset of sperm nuclear swelling after ICSI, does not by itself lead to the release of SAOAF from the spermatozoon. We postulate, however, that SAOAF is released during the sperm nuclear swelling phase, which is induced by the so-called sperm nucleus decondensing factor (SNDF) of the oocyte.

Animals↗