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J C Barrett

Publications and source records attributed to J C Barrett.

At least 127 records · Page 7Linked to original sources
PubMed1998

Identification and chromosomal assignment of two heterozygous mutations in the Trp53 gene in L5178Y/Tk(+/-)-3.7.2C mouse lymphoma cells.

The thymidine kinase locus (Tk1) in Tk(+/-)-3.7.2C mouse lymphoma cells is widely used to identify mutagenic agents. Because Trp53 (the mouse homolog of human TP53) is located with Tk1 on chromosome 11 and is critical in regulating cellular responses following exposure to DNA damaging agents, we wanted to determine if these mouse lymphoma cells harbor mutations in Trp53. Single-stranded conformation polymorphism (SSCP) analysis of PCR-amplified exons 4-9 of Trp53 indicated mutations in both exons 4 and 5. We sequenced exons 4-9 from isolated clones of Tk(+/-)-3.7.2C cells and a Tk-/- mutant (G4). Mutant G4 has two copies of the chromosome carrying the Tk1- allele and no copy of the chromosome carrying the Tk1+ allele and thus could establish linkage of the individual Trp53 and Tk1 alleles. DNA sequence analysis revealed no mutations in exons 6-9 in any Tk(+/-)-3.7.2C or G4 clones. As suggested by SSCP, there was a nonsense mutation in exon 4 at bp 301 (codon 101) in one Trp53 allele. Tk(+/-)-3.7.2C clones have both mutant and wild-type sequences at bp 301; G4 clones have wild-type exon 4 sequence. These data allow assignment of the Trp53 exon 4 mutated allele to chromosome 11 carrying the Tk1+ allele. The exon 4 mutation leads to a stop codon early in translation, thus functionally deleting the Trp53 allele on the Tk1(+)-bearing chromosome. As previously reported, we find a missense mutation in exon 5 at bp 517 (codon 173) in one Trp53 allele. Using the G4 clones we determined that the exon 5 mutation is linked to the Tk1- allele. Thus the Tk +/-(-)3.7.2C mouse lymphoma cells have two mutant Trp53 alleles, likely accounting for their rapid cell growth and contributing to their ability to detect the major types of mutational damage associated with the etiology of tumor development. This ability to integrate across the mutational events seen in the multiple stages of tumor development further supports the use of the assay in chemical and drug safety studies and its recommendation as part of the required screening battery for regulatory agency submissions.

Alleles↗
PubMed1998

Rescue of targeted regions of mammalian chromosomes by in vivo recombination in yeast.

In contrast to other animal cell lines, the chicken pre-B cell lymphoma line, DT40, exhibits a high level of homologous recombination, which can be exploited to generate site-specific alterations in defined target genes or regions. In addition, the ability to generate human/chicken monochromosomal hybrids in the DT40 cell line opens a way for specific targeting of human genes. Here we describe a new strategy for direct isolation of a human chromosomal region that is based on targeting of the chromosome with a vector containing a yeast selectable marker, centromere, and an ARS element. This procedure allows rescue of the targeted region by transfection of total genomic DNA into yeast spheroplasts. Selection for the yeast marker results in isolation of chromosome sequences in the form of large circular yeast artificial chromosomes (YACs) up to 170 kb in size containing the targeted region. These YACs are generated by homologous recombination in yeast between common repeated sequences in the targeted chromosomal fragment. Alternatively, the targeted region can be rescued as a linear YACs when a YAC fragmentation vector is included in the yeast transformation mixture. Because the entire isolation procedure of the chromosomal region, once a target insertion is obtained, can be accomplished in approximately 1 week, the new method greatly expands the utility of the homologous recombinationproficient DT40 chicken cell system.

Animals↗
PubMed1998

Expression of KAI1 in paraffin-embedded normal, hyperplastic and neoplastic prostate and prostate carcinoma cell lines.

Expression of KAI1, a tumor metastasis suppressor gene, was studied with different fixatives in frozen and paraffin-embedded sections of human and rat prostate carcinoma cell lines and human prostate lesions by immunohistochemistry. Immunoreactivity of the membrane antigen in cell lines was associated with known expression levels in these lines and the fixative used. Formalin and paraformaldehyde helped maintain the immunoreactivity of cells. In human prostate, frozen sections revealed diffuse reactivity of the antigen in normal and neoplastic tissues while paraffin-embedded tissues usually showed focal reactivity, although more than 50% of cases with normal epithelium and adenocarcinomas were reactive. In some cases, pretreatment with trypsin enhanced immunoreactivity. Benign prostatic hyperplasia (BPH) showed the most intense diffuse immunoreactivity, which suggested enhanced expression. Prostatic intraepithelial neoplasia (PIN) also often expressed high levels of KAI1. Three of five metastases were reactive but two primaries and their metastases were not. Lymphocytes in primary carcinomas and lymphocytes and germinal center cells in lymph nodes were immunoreactive, while adjacent primary or metastatic prostate adenocarcinoma epithelium was not immunoreactive. Although paraffin-embedded human tissues were not optimal for determining levels of expression of KAI1, they did show immunoreactivity that could have prognostic value and showed the specific cytoplasmic localization of the protein in cells.

Adenocarcinoma↗
PubMed1998

Correlation between reduction of metastasis in the MDA-MB-435 model system and increased expression of the Kai-1 protein.

Using microcell-mediated transfer of a normal chromosome 11 into the highly metastatic MDA-MB-435 human breast carcinoma cell line, we previously showed that human chromosome 11 contains a metastasis-suppressor gene for breast cancer. A known metastasis-suppressor gene, kai-1, and a related family member, tapa-1, have been mapped to chromosome 11p11.2 and 11p15.5, respectively. To determine if these genes are responsible for the metastasis suppression seen in our microcell hybrids, we examined their expression by western blot analysis. Although tapa-1 expression did not significantly correlate with metastasis suppression, kai-1 production was dramatically increased in the metastasis-suppressed chromosome 11 microcell hybrids and unchanged in the metastatic chromosome 6 controls. Transfection of full-length kai-1 cDNA into MDA-MB-435 cells resulted in clones that did not have a significantly decreased in vivo incidence of lung metastases. However, western blot analysis showed that the primary tumors and the metastatic lesions of the transfectants had decreased levels of kai-1 protein compared with the inoculated cells. Furthermore, several of the transfectant clones expressed heavily modified kai-1 protein compared with that of the microcell hybrids. Our data indicate that protein modification may affect the normal function of kai-1 in vivo and that a threshold level of kai-1 protein expression may be necessary for suppression of the metastatic phenotype.

Animals↗
PubMed1998

Differential subcellular p53 localization and function in N- and S-type neuroblastoma cell lines.

Neuroblastoma (NB) cells in vitro are capable of bidirectional transdifferentiation, resulting in two distinct, yet reversible, phenotypes of neuroblastic (N-type) and nonneuronal (S-type) Schwann-like cells. Our previous studies suggested that the wild-type p53 protein is subject to differential regulation in a subset of neuronal cell types. To further test this hypothesis, we compared p53 function in three matched pairs of N- and S-type cell lines, each pair originating from an individual NB tumor. Our data show that although p53 remains cytoplasmically sequestered in a punctate pattern in N-type cells after DNA damage, the protein is diffusely distributed in the S-type cells and is additionally capable of translocating to the nucleus and mediating a biological response to this damage. Our data, therefore, suggest that the p53 protein may be differentially regulated by a neuronal cellular environment and that the sequestration of p53 in NB may be reversible.

Cell Line↗
PubMed1998

PTEN mutation in endometrial cancers is associated with favorable clinical and pathologic characteristics.

Mutation of the PTEN tumor suppressor gene is a frequent event in endometrial cancers. In other types of cancers, PTEN mutation has been associated with metastatic behavior and advanced stage. To examine the relationship between PTEN mutation and clinical features of endometrial cancers, we screened 136 cases for mutations in the nine exons and intronic splice sites of the PTEN gene, using single-strand conformation analysis, and aberrant bands were sequenced. Mutations were noted in 44 of 136 (32%) endometrial cancers, and two mutations were present in 8 cases. There were 36 cases with mutations resulting in truncated protein products, 6 cases with missense mutations in the phosphatase domain, 1 case with an in-frame deletion, and 1 case with a large insertion. Mutation of the PTEN gene correlated most closely with endometrioid histology; mutations were seen in only 5% (1 of 21) of serous/clear cell cancers compared with 37% (43 of 115) of endometrioid cancers (P = 0.004). PTEN mutation was associated with early stage, nonmetastatic disease and more favorable survival in both the entire group of 136 cases and in the 115 endometrioid cases. In addition, PTEN mutation correlated with other molecular features associated with favorable clinical behavior, including microsatellite instability and absence of p53 overexpression. Microsatellite instability was found in 60% of cases with PTEN mutations compared with only 25% of cases without mutations (P = 0.004). Overexpression of p53 was seen in only 14% of cases with PTEN mutations compared to 39% of cases without mutations (P = 0.006). In conclusion, PTEN mutation is associated with endometrioid histology and other favorable pathological, clinical, and molecular features rather than with increased metastatic potential as has been noted in some other types of cancers.

Adult↗
PubMed1997

Human chromosome 7 carries a putative tumor suppressor gene(s) involved in choriocarcinoma.

Choriocarcinoma developed from a complete hydatidiform mole has an unique genetic feature that involves monoallelic contribution from the paternal genome. To determine the chromosome carrying putative tumor suppressor gene(s), microcell-hybrids were isolated following fusion of choriocarcinoma cells with microcells from mouse A9 cells containing a single human chromosome (1, 2, 6, 7, 9 or 11). Microcell-hybrids with the introduction of chromosome 7 were suppressed or modulated for tumorigenicity and exhibited altered in vitro growth properties. Introduction of chromosomes 1, 2, 6, 9 or 11 had no effect. Tumorigenic revertants isolated from microcell-hybrids with the introduced chromosome 7 contains reduced numbers of chromosome 7. These findings suggest that chromosome 7 contains a putative tumor suppressor gene(s) for choriocarcinoma. Alterations in tumorigenic phenotypes seen in microcell-hybrids were not associated with the presence of either ERV3 or H-plk locus located on the introduced chromosome 7, indicating the putative tumor suppressor gene(s) is outside of ERV3 and H-plk gene loci. Furthermore, we obtained evidence to define a critical region on chromosome 7 (7p12-7q11.23) that was frequently lost in surgically removed choriocarcinoma tissues and cell lines. Using a panel of microsatellite markers, biallelic deletions were observed, which strongly suggests the presence of a tumor suppressor gene(s) within this critical region.

Animals↗
PubMed1997

Cell-transforming activity and genotoxicity of phenolphthalein in cultured Syrian hamster embryo cells.

Phenolphthalein is a cathartic agent widely used in non-prescription laxatives. For the simultaneous assessment of in vitro carcinogenicity and mutagenicity of phenolphthalein, the ability of this chemical to induce cell transformation and genetic effects was examined using the Syrian hamster embryo (SHE) cell model. Cell growth was reduced by treatment with phenolphthalein at 10-40 microM in a dose-related manner. Treatment with phenolphthalein for 48 hr induced a dose-dependent increase in morphological transformation of SHE cells. Over the dose range that resulted in cell transformation ( 10-40 microM), treatment of SHE cells with phenolphthalein induced gene mutations at the hprt locus but not at the Na+/K+ ATPase locus. A statistically significant level of chromosomal aberrations was elicited in SHE cells treated with phenolphthalein at the highest dose (40 microM). Meanwhile, neither numerical chromosomal changes nor DNA adduct formation, analyzed by the nuclease P1 enhancement version of 32P-post-labeling, were induced by treatment with phenolphthalein at any concentrations examined. We thus report cell-transforming activity and mutagenicity of phenolphthalein assessed with the same mammalian cells in culture. Our results provide evidence that phenolphthalein has cell-transforming and genotoxic activity in cultured mammalian cells. The mutagenic and clastogenic activities of phenolphthalein could be a causal mechanism for carcinogenicity in rodents.

Animals↗
PubMed1997

Dietary restriction reduces insulin-like growth factor I levels, which modulates apoptosis, cell proliferation, and tumor progression in p53-deficient mice.

Diet contributes to over one-third of cancer deaths in the Western world, yet the factors in the diet that influence cancer are not elucidated. A reduction in caloric intake dramatically slows cancer progression in rodents, and this may be a major contribution to dietary effects on cancer. Insulin-like growth factor I (IGF-I) is lowered during dietary restriction (DR) in both humans and rats. Because IGF-I modulates cell proliferation, apoptosis, and tumorigenesis, the mechanisms behind the protective effects of DR may depend on the reduction of this multifaceted growth factor. To test this hypothesis, IGF-I was restored during DR to ascertain if lowering of IGF-I was central to slowing bladder cancer progression during DR. Heterozygous p53-deficient mice received a bladder carcinogen, p-cresidine, to induce preneoplasia. After confirmation of bladder urothelial preneoplasia, the mice were divided into three groups: (a) ad libitum; (b) 20% DR; and (c) 20% DR plus IGF-I (IGF-I/DR). Serum IGF-I was lowered 24% by DR but was completely restored in the IGF-I/DR-treated mice using recombinant IGF-I administered via osmotic minipumps. Although tumor progression was decreased by DR, restoration of IGF-I serum levels in DR-treated mice increased the stage of the cancers. Furthermore, IGF-I modulated tumor progression independent of changes in body weight. Rates of apoptosis in the preneoplastic lesions were 10 times higher in DR-treated mice compared to those in IGF/DR- and ad libitum-treated mice. Administration of IGF-I to DR-treated mice also stimulated cell proliferation 6-fold in hyperplastic foci. In conclusion, DR lowered IGF-I levels, thereby favoring apoptosis over cell proliferation and ultimately slowing tumor progression. This is the first mechanistic study demonstrating that IGF-I supplementation abrogates the protective effect of DR on neoplastic progression.

Aniline Compounds↗
PubMed1997

PTEN/MMAC1 mutations in endometrial cancers.

Endometrial carcinomas represent the most common gynecological cancer in the United States, yet the molecular genetic events that underlie the development of these tumors remain obscure. Chromosome 10 is implicated in the pathogenesis of endometrial carcinoma based on loss of heterozygosity (LOH), comparative genomic hybridization, and cytogenetics. Recently, a potential tumor suppressor gene, PTEN/MMAC1, with homology to dual-specificity phosphatases and to the cytoskeletal proteins tensin and auxillin was identified on chromosome 10. This gene is mutated in several types of advanced tumors that display frequent LOH on chromosome 10, most notably glioblastomas. Additionally, germ-line mutations of PTEN/MMAC1 are responsible for several familial neoplastic disorders, including Cowden disease and Bannayan-Zonana syndrome. Because this locus is included in the region of LOH in many endometrial carcinomas, we examined 70 endometrial carcinomas for alterations in PTEN/MMAC1. Somatic mutations were detected in 24 cases (34%) including 21 cases that resulted in premature truncation of the protein, 2 tumors with missense alterations in the conserved phosphatase domain, and 1 tumor with a large insertion. These data indicate that PTEN/MMAC1 is more commonly mutated than any other known gene in endometrial cancers.

Adenocarcinoma↗
PubMed1997

Correction of hypermutability, N-methyl-N'-nitro-N-nitrosoguanidine resistance, and defective DNA mismatch repair by introducing chromosome 2 into human tumor cells with mutations in MSH2 and MSH6.

The human DNA mismatch repair genes hMSH2 and hMSH6 encode the proteins that, together, bind to mismatches to initiate repair of replication errors. Human tumor cells containing mutations in these genes have strongly elevated mutation rates in selectable genes and at microsatellite loci, although mutations in these genes cause somewhat different mutator phenotypes. These cells are also resistant to killing by certain drugs and are defective in mismatch repair. Because the elevated mutation rates in these cells may lead to mutations in additional genes that are causally related to the other defects, here we attempt to establish a cause-effect relationship between the hMSH2 and hMSH6 gene mutations and the observed phenotypes. The endometrial tumor cell line HEC59 contains mutations in both alleles of hMSH2. The colon tumor cell line HCT15 contains mutations in hMSH6 and also has a sequence change in a conserved region of the coding sequence for DNA polymerase delta, a replicative DNA polymerase. We introduced human chromosome 2 containing the wild-type hMSH2 and hMSH6 genes into HEC59 and HCT15 cells. Introduction of chromosome 2 to HEC59 cells restored microsatellite stability, sensitivity to N-methyl-N'-nitro-N-nitrosoguanidine treatment, and mismatch repair activity. Transfer of chromosome 2 to HCT15 cells also reduced the mutation rate at the HPRT locus and restored sensitivity to N-methyl-N'-nitro-N-nitrosoguanidine treatment and mismatch repair activity. The results demonstrate that the observed defects are causally related to mutations in genes on chromosome 2, probably hMSH2 or hMSH6, but are not related to sequence changes in other genes, including the gene encoding DNA polymerase delta.

Cell Fusion↗
PubMed1997

Location of KAI1 on the short arm of human chromosome 11 and frequency of allelic loss in advanced human prostate cancer.

BACKGROUND: We recently isolated the KAI1 gene, a metastasis suppressor gene for prostate cancer, from human chromosome region 11p13-cen-containing rat prostate cancer cells. The present study was performed to further locate the region of the KAI1 gene on the short arm of chromosome 11, and to examine whether loss of this region is significant during progression of human prostate cancer. METHODS: The small portion of human chromosome 11 (i.e., 11p13-cen) was reintroduced into highly metastatic rat prostate cancer cells by using microcell-mediated chromosome transfer. Loss of heterozygosity (LOH) at polymorphic microsatellite loci on the human chromosome 11 was examined in human prostate cancer tissues. RESULTS: The minimum region of human chromosome 11 that contained the KAI1 gene was located on the proximal region of 11p11.2 divided by the D11S554 locus. The percentage of LOH or allelic imbalance at the D11S1344 locus, which is located on the same region as the KAI1 locus, in metastasis tissues from autopsy cases who died from metastatic prostate cancer was 70% (7 of 10 informative cases), whereas the percentages in primary tumors from the same cases and from cases with clinically localized prostate cancer were 33% (3 of 9 informative cases) and 8% (1 of 12 informative cases), respectively. CONCLUSIONS: These findings demonstrate a high frequency of LOH or allelic imbalance at the centromeric region of 11p, which contains the KAI1 gene in advanced prostate cancer.

Adenocarcinoma↗
PubMed1997

p53-dependent p21 induction following gamma-irradiation without concomitant p53 induction in a human peripheral neuroepithelioma cell line.

We previously generated cell hybrids between a derivative of the E6-containing HeLa cell line and a p53 null peripheral neuroepithelioma (PNET) cell line. Although p53 protein from the hybrids was genotypically wild type, it did not demonstrate wild-type behavior. Therefore, in the present study, we introduced wild-type p53 into the PNET parent to investigate whether p53 retained wild-type function within this cell line. Although the p53 null PNET parent lacked detectable p21 protein, introduction of wild-type p53 resulted in a detectable expression of p21 protein in all clones tested, suggestive of wild-type p53 function. In addition, p53 expression was necessary for induction of p21 in response to irradiation, and, furthermore, we show this induction to occur at the transcriptional level. Although introduction of wild-type p53 seems to be responsible for p21 induction, the overall protein levels of p53 were not induced. The involvement of p53 in up-regulating p21 is further substantiated by the observation that p21 up-regulation was dependent on the introduction of the wild-type protein. Our results suggest that wild-type p53 is capable of up-regulating p21 in response to DNA damage in the absence of p53 induction.

Biological Transport↗
PubMed1997

Direct isolation of human BRCA2 gene by transformation-associated recombination in yeast.

Mutant forms of the BRCA2 gene contribute significantly to hereditary breast cancer. Isolation of the normal and mutant forms of the BRCA2 gene with its natural promoter would greatly facilitate analysis of the gene and its contribution to breast cancer. We have accomplished the direct isolation of the 90-kb gene from total human DNA by transformation-associated recombination in yeast using a small amount of 5' and 3' BRCA2 sequence information. Because the entire isolation procedure of a single chromosomal gene could be accomplished in approximately 2 weeks, the transformation-associated recombination cloning approach is readily applicable to studies of chromosome alterations and human genetic diseases.

BRCA2 Protein↗
PubMed1997

Insulin-like growth factor 1 (IGF-1) alters drug sensitivity of HBL100 human breast cancer cells by inhibition of apoptosis induced by diverse anticancer drugs.

In this study, we tested the hypothesis that insulin-like growth factor-1 (IGF-1) modulates apoptosis in human breast cancer cells, HBL100, induced by diverse chemotherapeutic drugs. IGF-1 increased cell survival of HBL100 cells treated with 5-fluorouracil (antimetabolite), methotrexate (antimetabolite), tamoxifen (antiestrogen/antiproliferative), or camptothecin (topoisomerase 1 inhibitor) and after serum withdrawal. Elevated cell survival was not due to an increase in cell proliferation by IGF-1, but rather to an inhibition of apoptosis. Evidence for death by apoptosis was supported by cellular morphology and DNA fragmentation. There were no changes observed in Bcl-2 protein or bax mRNA levels. Extracellular matrix (ECM) is known to influence the apoptotic response of cells; therefore, the antiapoptotic effect of IGF-1 on breast cancer cells was examined using different ECMs: laminin, collagen IV, or Matrigel. IGF-1 protected cells from apoptosis induced by methotrexate on all ECMs tested, providing the first evidence that IGF-1 protects against apoptosis in three-dimensional culture systems. These data provide the rationale to search for drugs that lower serum IGF-1 in an effort to improve the efficacy of chemotherapeutic drugs for the treatment of breast cancer.

Antineoplastic Agents↗
PubMed1997

An integrated transcript map of human chromosome 1p35-p36.

The distal short arm of human chromosome 1 (1p) is rearranged in a variety of malignancies, and several genetic diseases also map to this region. We have constructed an integrated transcript map to precisely define the positions of genes and expressed sequence tags (ESTs) previously mapped to 1p35-p36, a region spanning approximately 40 Mb. To anchor the integrated map, a framework genetic map was constructed with 24 genetic markers and a marker order of 1000:1 odds, yielding an average resolution of 2.8 cM. An additional 106 genetic markers were localized relative to the framework genetic map. To place markers more precisely within 1p35-p36, a chromosome 1-specific, radiation-reduced hybrid (RH) panel was created. Individual DNA fragments of the RH panel were identified and ordered by PCR with the framework genetic map. A total of 250 markers, including 142 genes and ESTs, were mapped by PCR against the RH panel. The map has an observed resolution of 800 kb, and the results closely match and more precisely define previous mapping information for most markers. This map will help to identify candidate genes for genetic diseases mapping to distal 1p and is fully integrated with existing genetic and RH maps of the human genome.

Animals↗
PubMed1997

Failure of HPV E6 to rapidly degrade p53 in human HeLa x PNET cell hybrids.

The ability of the E6 protein from high risk human papillomaviruses (HPVs) to degrade p53 via the ubiquitin pathway plays a major role in the development of cervical carcinomas. We have previously generated cell hybrids between a p53 null peripheral neuroepithelioma (PNET) cell line and a cervical carcinoma HeLa cell line which exhibits efficient E6-mediated degradation of p53. All of the resulting hybrids expressed HPV 18 E6 from the HeLa parent and some of the hybrids additionally expressed HPV 16 E6. Surprisingly, in spite of abundant E6 expression, the hybrids expressed relatively high steady-state levels of the wild-type p53 protein. We then examined the hybrids to determine whether other components of the E6-mediated degradation pathway were missing or nonfunctional. Specifically, we determined that the E6-associated protein (E6-AP), essential for E6-mediated degradation, was expressed. We further verified that these hybrids had a functional ubiquitination pathway, which suggests that this phenomenon is not due to a general defect in this pathway. We therefore conclude that other unidentified, possibly cell-specific factors can play a role in the E6-mediated degradative process and may act to inhibit this process.

DNA Damage↗