bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specific Ki‐ras codon 61 mutations may determine the development of urethan‐induced mouse lung adenomas or adenocarcinomas
Authors: Nuzum Edwin O. , Malkinson Alvin M. , Beer David G. 
Published: February 2007

AbstractIn A/J strain mice, the carcinogen urethan induces lung adenomas and adenocarcinomas that contain Ki‐ras‐activating mutations primarily in codon 61. These mutations affect the middle adenine in codon 61 resulting in the substitution of either arginine (AT→GC transition) or leucine (AT→TA transversion) for the wild‐type gluta‐mine. To analyze the expression of the wild‐type and mutant Ki‐ras mRNAs in primary mouse lung tumors and transformed mouse lung cell lines, we utilized reverse transcription of total mRNA and DNA amplification by the polymerase chain reaction. The wild‐type allele of coden 61 was expressed in all normal lung and primary tumor samples and in all transformed cell lines, except one. Significantly, the leucine‐substituted allele was expressed primarily in very small lung adenomas, whereas the arginine‐substituted allele was expressed in large lung adenocarcinomas and transformed lung cell lines. The relative amounts of expression of the mutant versus wild‐type Ki‐ras alleles and the total Ki‐ras mRNA expression was similar in both lung adenomas and adenocarcinomas. Further, the arginine mutant allele was present in adenocarcinomas having either alveolar or papillary tumor morphologies. These results suggest that the specific activating Ki‐ras mutation is more critical to either lung adenoma or adenocarcinoma development than is the tumor's cell of origin or the extent to which the mutant alleles are expressed. A distinct role of the specific activating Ki‐ras mutations in affecting lung tumor growth or malignant potential is indicated.
Differentiation of cultured human breast cancer cells (AU‐565 and MCF‐7) associated with loss of cell surface HER‐2/neu antigen
Authors: Bacus Sarah S. , Kiguchi Kaoru , Chin Dot , King C. Richter , Huberman Eliezer 
Published: February 2007

AbstractThe relationship between terminal cell differentiation and changes in the subcellular levels of the HER‐2/neu antigen was investigated in cultured human breast cancer cells: AU‐565 cells (which overexpress the HER‐2/neu gene) and MCF‐7 cells (which do not overexpress this gene). Differentiation was achieved by treating the cells with mycophenolic acid (MPA), phorbol 12‐myristate 13‐acetate (PMA), retinoicacid (RA), or the TA‐1 monoclonal antibody to the extracellular domain of the HER‐2/neu protein. Ten to twenty percent of the cells in untreated, sparsely growing AU‐565 cultures exhibited morphological maturation characterized by large lacy nuclei surrounded by sizable flat cytoplasms. A fraction of these cells harbored milk factors such as casein and large lipid droplets. Treatment of the AU‐565 cells for 4 d with 9 μM MPA, 1.6 nM PMA, 2.5 μM RA, or 1 μg/mL TA‐1 antibody resulted in cell growth inhibition and an increase in the percentage of cells (48‐97%) that exhibit a mature phenotype. MCF‐7 cells were also susceptible to differentiation by MPA and RA, but to a lesser degree than the AU‐565 cells. Differentiation in the AU‐565 and MCF‐7 cells was associated with reduced immunostaining for the HER‐2/neu protein at the cell surface membrane and with a transient increased diffuse immunostaining for this protein in the cytoplasm.
Activating missense mutations in Ha‐ras‐1 genes in a malignant subset of Bladder lesions induced by N‐butyl‐N‐(4‐hydroxybutyl) nitrosamine or N‐[4‐(5‐nitro‐2‐furanyl)‐2‐thiazolyl]formamide
Authors: Jones Richard F. , Debiec‐Rychter Maria , Zukowski Kim , Wang Ching Y. 
Published: February 2007

AbstractUrothelial cell cultures generated from urinary bladders from a series of N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN)‐ or N‐[4‐(5‐nitro‐2‐furanyl)‐2‐thiazolyl]formamide (FANFT)‐treated Fischer 344 rats were examined for activating missense mutations in Ha‐ras‐1 genes. Our overall objective was to identify oncogene‐activating mutations in this system and to determine what altered biological properties correlate with such genetic changes. The urinary bladders from the treated animals showed a spectrum of histopathologies, from simple hyperplasia to transitional cell carcinoma (TCC). Using restriction analysis, oligonucleotide hybridization, and DNA sequencing, we found that approximately 20% (3/14) of the bladder cell cultures had acquired oncogenic single‐base substitutions in codon 61 of Ha‐ras‐1 genes (CAA → AAA or CGA). The donor bladder lesions for these three cultures, which also harbored the same ras‐activating mutations, were all classified as stage A or B TCCs. However, four other TCCs also arising in this series were found to have normal Ha‐ras genes. Whereas approximately half of the bladder cultures derived from the carcinogen‐treated rats were nontumorigenic in athymic mice, the three cultures containing ras oncogenes were all highly tumorigenic (forming tumors within 5 wk of injection into athymic mice). These cultures also displayed a high degree of anchorage‐independent growth and NIH 3T3‐transforming activity in gene transfer assays. The nontumorigenic cultures were derived from bladder lesions that included three hyperplasias and three stage A TCCs. We conclude that ras‐activating missense mutations were present in a malignant subset of bladder lesions induced by BBN or FANFT, but most of the lesions in this system appeared to involve genetic alterations elsewhere. Thus other oncogenes besides activated Ha‐ras may apparently be associated with the same bladder histopathologies and transformation markers.
Mutational activation of c‐HA‐ras gene in squamous cell carcinomas of rat zymbal gland induced by carcinogenic heterocyclic amines
Authors: Kudo Mami , Ogura Tsutomu , Esumi Hiroyasu , Sugimura Takashi 
Published: February 2007

AbstractThe activation of the c‐Ha‐ras gene and its carcinogen specificity were examined in squamous cell carcinomas (SCCs) induced by the mutagenic heterocyclic amines 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ), 2‐amino‐3, 8‐dimethylimidazo[4,5‐f]quinoxaline (MeIQx), and 2‐amino‐3, 4‐dimethylimidazo[4,5‐f]quinoline (MeIQ) in the Zymbal gland in rats. DNA fragments of the c‐Ha‐ras gene were amplified from formalin‐fixed and paraffin‐embedded tissues by polymerase chain reaction and analyzed for activating mutations involving codons 12, 13, and 61 by oligonucleotide differential hybridization and sequencing. c‐Ha‐ras mutations were found in four of seven and two of six Zymbal gland SCCs induced by IQ and MelQx, respectively. These mutations were located in either codon 13 or 61. In the case of MelQ, point mutations at the second nucleotide of codon 13 were found in nine of the total 14 Zymbal gland SCCs and in one papilloma. Of the nine SCCs that had mutations in codon 13, two possessed mutations at the second nucleotide of codon 12 as well. Most reported mutations in c‐Ha‐ras are located at codon 12 or 61, but the heterocyclic amines in this study induced mutations not only at codons 12 and 61 but also in codon 13. Transversions were the dominant mutation induced by these heterocyclic amines.
Evidence for autocrine/paracrine growth stimulation by transforming growth factor‐α during the process of skin tumor promotion
Authors: Imamoto Akira , Beltrán Linda M. , Digiovanni John 
Published: February 2007

AbstractA single topical application of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) to mouse skin decreased 125I‐labeled epidermal growth factor (EGF) binding in epidermal membrane preparations within 1 h while 1,8‐dihydroxy‐3‐methyl‐9‐anthrone (chrysarobin) gradually reduced binding with maximum inhibition at 15 h. Subsequently, 125I‐EGF binding increased to ∼ 200% of control in epidermal membrane preparations from both TPA‐ and chrysarobin‐treated mice. A single application of TPA but not chrysarobin resulted in a rapid translocation of protein kinase C (PKC) to the membrane; however, treatment with both promoters ultimately led to a time‐dependent loss of PKC activity in both membrane and cytosol fractions. The initial inhibition of 125I‐EGF binding was sustained for at least 24 h after single and multiple treatments with both promoting agents. Acid washing restored EGF binding to control levels in membrane preparations obtained 24 h after a single application, whereas acid washing of membrane preparations obtained 24 h after a second application of TPA or chrysarobin increased binding (2.5‐fold and 1.5‐fold that of the control, respectively). The presence of increased amounts of ligands for the EGF receptor in tumor promoter‐treated epidermis was initially confirmed in 125I‐EGF binding competition experiments using NRK‐49F cells. A single topical application of TPA or chrysarobin induced elevated levels of transforming growth factor‐α (TGF‐α) mRNA at 6 h or 15–24 h, respectively. Elevated levels of a TGF‐α precursor (21 kDa) were subsequently observed in cytosol and membrane preparations after single and multiple applications of TPA or chrysarobin. These results suggest that repeated topical application of tumor promoters may lead to sustained loss of a negative‐feedback mechanism involving phosphorylation at Thr‐654 of the EGF receptor by PKC. The concomitant elevation of ligands, such as TGF‐α, may provide a mechanism for sustained cell proliferation essential for skin tumor promotion.
Analysis of CYP1A1 promoter function by transcription in vitro
Authors: Wen Long‐Ping , Jones Keith W. , Whitlock James P. 
Published: February 2007

AbstractWe have analyzed the function of the CYP1A1 promoter using in vitro transcription. Using nuclear extracts from HeLa cells, we found that transcription from the promoter in vitro was constitutive. Transcription in vitro was not increased by prior exposure of the HeLa cells to the inducer 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin nor by the inclusion of a dioxin‐responsive enhancer in the DNA template. Analyses of mutants revealed that a TATAAA sequence and two recognition motifs for CCAAT box transcription factor/nuclear factor I contributed to the constitutive activity of the promoter in vitro.
Expression of RB and p53 proteins in HPV‐positive and HPV‐negative cervical carcinoma cell lines
Authors: Wrede David , Tidy John A. , Crook Tim , Lane David , Vousden Karen H. 
Published: February 2007

AbstractMutations within the tumor suppressor genes Rb‐1 and p53 are commonly found in many human malignancies, and loss of wild‐type function of both p53 and RB appear to be important events in the development of these malignancies. Interference with normal RB and p53 function in the cell has apparently also been exploited by the oncogenic genital human papillomaviruses (HPVs), which encode transforming proteins capable of binding cellular RB and p53 proteins. We have investigated the expression of RB and p53 in a series of eight cervical carcinoma cell lines, six of which contain HPV sequences and two of which have arisen apparently independently of HPV infection. In the six HPV‐positive lines, no evidence of abnormal RB or p53 protein could be detected. However, there was evidence for abnormal RB and p53 in the two HPV–negative lines. These data are consistent with the hypothesis that loss of wild‐type RB and p53 function is necessary for tumor development and that such loss can occur either by mutation within the cellular gene or by expression of viral proteins capable of complexing wild‐type cellular proteins.
Analysis of oncogene alterations in human endometrial carcinoma: Prevalence of ras mutations
Authors: Boyd Jeff , Risinger John I. 
Published: February 2007

AbstractThe molecular genetics of human endometrial carcinoma have yet to be defined to any significant extent. Cell lines from 11 endometrial carcinomas were examined for alterations in proto‐oncogenes that might predictably be present, based on existing data from the better‐characterized human carcinomas of the uterine cervix, ovary, and breast. Codons 12, 13, and 61 of the Ha‐ras, Ki‐ras, and N‐ras genes were examined for possible point mutations, and the c‐erbB2/neu, c‐myc, and epidermal growth factor receptor (EGFR) genes were examined for amplification or overexpression. Ras mutations were found in seven of 11 (64%) tumors, including three in codon 61 of Ha‐ras (CAG·CAT) and four in codon 12 of Ki‐ras (GGT→GAT in two and GGT→GTT in two). No evidence was found for amplification or overexpression of the c‐enbB2 or EGFR genes in any tumor. One tumor contained amplified c‐myc sequences and exhibited relative overexpression of c‐myc. These data suggest that the amplification or overexpression of several proto‐oncogenes frequently observed in other human gynecologic and breast tumors are not prevalent in endometrial carcinoma and that ras gene mutations are relatively common in this tumor type.
Ras gene mutation and amplification in human nonmelanoma skin cancers
Authors: Pierceall William E. , Goldberg Leonard H. , Tainsky Michael A. , Mukhopadhyay Tapas , Ananthaswamy Honnavara N. 
Published: February 2007

AbstractOur previous studies have shown that human skin cancers occurring on sun‐exposed body sites frequently contain activated Ha‐ras oncogenes capable of inducing morphologic and tumorigenic transformation of NIH 3T3 cells. In this study, we analyzed human primary squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs) occurring on sun‐exposed body sites for mutations in codons 12, 13, and 61 of Ha‐ras, Ki‐ras, and N‐ras oncogenes by amplification of genomic tumor DNAs by the polymerase chain reaction, followed by dot‐blot hybridization to synthetic oligonucleotide probes designed to detect single base‐pair mutations. In addition to the primary human skin cancers, we also analyzed Ha‐ras‐positive NIH 3T3 transformants for mutations in the Ha‐ras oncogene. The results indicated that all three NIH 3T3 transformants, 11 of 24 (46%) SCCs, and 5 of 16 (31 %) BCCs contained mutations at the second position of Ha‐ras codon 12 (GGC→GTC), predicting a glycine‐to‐valine amino acid substitution, whereas only 1 of 40 skin cancers (an SCC) displayed a mutation in the first position of Ki‐ras codon 12 (GGT→AGT), predicting a glycine‐to‐serine amino acid change. In addition, three of the SCCs contained highly amplified copies of the N‐ras oncogene in their genomic DNA. Interestingly, two of the SCCs containing amplified N‐ras sequences also had G→T mutations in codon 12 of the Ha‐ras oncogene. These studies demonstrate that mutations in codon 12 of the Ha‐ras oncogene occurred at a high frequency in human skin cancers originating on sun‐exposed body sites, whereas mutation in codon 12 of Ki‐ras or amplification of N‐ras occurred at a low frequency. Since the mutations in the Ha‐ras and Ki‐ras oncogenes were located opposite potential pyrimidine dimer sites (C‐C), it is likely that these mutations were induced by ultraviolet radiation present in sunlight.
Altered growth regulation of rat kidney proximal tubule epithelial cells transformed in vitro by SV40 viral DNA: Fibroblast growth factors (heparin‐binding growth factors) are potent inducers of anchorage‐independent growth
Authors: Zhang Guohong , Stevens James L. 
Published: February 2007

AbstractThe majority of renal cancers are thought to arise from the proximal tubule epithelium, but little is known about their etiology. In this investigation, we have established an in vitro model to study the transformation of these target cells using rat kidney proximal tubule epithelial cells (RPTE) transformed in defined medium with SV40‐viral DNA. Selection by passaging cells onto plastic surfaces yielded a population of cells (SV‐RPTE) that expressed keratin and vimentin along with SV40 large‐T antigen. The cells were morphologically transformed and lost their differentiated character as determined by several RPTE markers. SV‐RPTE cells grew in soft agar in serum‐supplemented medium containing insulin, epidermal growth factor, and cholera toxin, but were unable to grow when serum and growth factors were not combined. Acidic and basic fibroblast growth factors (aFGF and bFGF) were unique since they were the only single factor that induced anchorage‐independent growth in the presence of serum alone. Transforming growth factor‐β1 (TGF‐β1) was a potent inhibitor of anchorage‐independent growth, but the inhibition was partially overcome by a combination of growth factors. The growth factor responses of SV‐RPTE in monolayer cultures differed from those in soft agar; the cells were more sensitive to growth stimulation by insulin and insulin‐like growth factor, neither of which stimulated anchorage‐independent growth. SV‐RPTE cells in monolayer cultures had also lost the sensitivity to growth inhibition by TGF‐β1 characteristic of normal RPTE. The RPTE transformation model described here will be very useful for investigating the molecular basis and etiology of renal cancers. Furthermore, the data suggest that maintenance of the transformed phenotype by aFGF and bFGF and loss of negative growth regulation by TGF‐β1 could play a role in renal carcinogenesis.
Racial variation in the distribution of Ha‐ras‐1 alleles
Authors: Weston Ainsley , Vineis Paolo , Caporaso Neil E. , Krontiris Theodore G. , Lonergan Joyce A. , Sugimura Haruhiko 
Published: February 2007

AbstractRestriction fragment length polymorphism analyses of the Ha‐ras‐1 proto‐oncogene were undertaken in white and black populations residing in the Baltimore‐Washington metropolitan area to address whether specific rare alleles of the Ha‐ras‐1 proto‐oncogene locus vary in their distribution among different racial groups. High‐molecular‐weight genomic DNA samples from the lungs of 80 lung cancer patients and 92 accident victims were digested with appropriate restriction enzymes and subjected to Southern analysis using the 6.6‐kb BamHl human Ha‐ras‐1 recombinant fragment from the plasmid pEC. Thirty allelomorphs of different sizes were detected among the 172 study subjects. An association was observed between race and specific alleles. Rare alleles were more frequent in black cancer patients and trauma victims than in whites. Within each racial category, lung cancer patients had an excess of rare alleles. These data indicate the importance of controlling for racial variation when designing studies to determine human cancer risk factors.
The role of Ha‐ras oncogenes in growth factor independence in rat mammary carcinoma cells
Authors: Chiodino Caterina , Jones Richard F. , Ethier Stephen P. 
Published: February 2007

AbstractTo determine if activation of the c‐Ha‐ras‐1 gene is involved in the acquisition of growth factor independence in 7,12‐dimethylbenz[a]anthracene (DMBA)‐and N‐nitrosomethylurea (NMU)‐induced rat mammary carcinomas, three strategies were used. First, Ha‐ras DNA from growth factor‐independent DMBA‐induced rat mammary tumor cells was amplified using the polymerase chain reaction and examined for the presence of mutations in the first and second exons of Ha‐ras‐1 by restriction fragment length polymorphism analysis, allele‐specific oligonucleotide hybridization, and direct sequencing. No mutations were found in the codon 12/13 or codon 61 regions of the Ha‐ras‐1 gene. Second, a similar analysis of an NMU‐induced mammary carcinoma showed that it harbored an activating mutation in codon 12 of Ha‐ras‐1. When analyzed for growth factor requirements, these cells were found to express limited growth potential in all media tested, in contrast to growth factor‐independent cells, which proliferated extensively in the presence or absence of exogenous growth factors. Third, growth factor‐dependent rat mammary tumor cells and spontaneously immortalized rat normal mammary epithelial cells were transfected with an activated form of the Ha‐ras‐1 (T24) gene, and the growth factor requirements of the transfected cells were examined. The ras‐transfected cells retained the growth factor requirements of the normal cells. In addition, ras‐transfected cells were transplanted into syngeneic rats and nude mice, and no tumors developed after 6 mo in vivo. These results indicate that, in rat mammary tumor cells, neither growth factor independence in vitro nor transplantability are directly mediated by Ha‐ras oncogenes. The results also suggest that ras activation and growth factor independence may be associated with independent pathways to malignancy in rat mammary tumorigenesis.
The B subgroup bovine papillomaviruses lack an identifiable E6 open reading frame
Authors: Jackson Maria E. , Pennie William D. , McCaffery Roselyn E. , Smith Kenneth T. , Grindlay G. Joan , Campo M. Saveria 
Published: February 2007

AbstractAnalysis of the corrected DNA sequence for the bovine papillomavirus type 4 (BPV4) genome revealed that there is no open reading frame (ORF) that might encode an E6 protein. The other two B subgroup bovine papillomaviruses, BPV3 and BPV6, were found to have the same arrangement of ORFs in this region as BPV4. Thus, we conclude that E6 functions are either not required by these viruses or are performed by another viral (or host) protein. Furthermore, the position that might be expected to be occupied by E6, between the long control region and the E7 ORF, contains the E8 ORF, which has the potential to encode a 42‐residue polypeptide with considerable similarity to the E5 transforming protein of BPV1. Therefore, it appears that during the evolution of the B subgroup of BPVs, genomic rearrangements may have occurred resulting in the present layout of the early ORFs.
Formation of stable p53 homotetramers and multiples of tetramers
Authors: Stenger Judith E. , Mayr Gregory A. , Mann Kristine , Tegtmeyer Peter 
Published: February 2007

AbstractWe have used gradient gel electrophoresis and chemical cross‐linking to analyze the quaternary structure of purified, wild‐type, murine p53. Under nondenaturing conditions, p53 electrophoreses as tetramers and multiples of tetramers. Under denaturing conditions, fully cross‐linked p53 also behaves as tetrameric structures. We confirmed the composition of the tetramers by partially cross‐linking p53 and dissociating tetramers into monomers, dimers, and trimers. © 1992 wiley‐Liss, Inc.
Increased expression of cathepsins L and B and decreased activity of their inhibitors in metastatic, ras‐transformed NIH 3T3 cells
Authors: Chambers Ann F. , Colella Rita , Denhardt David T. , Wilson Sylvia M. 
Published: February 2007

AbstractWe previously found that the T24 Ha‐ras oncogene induces metastatic ability in NIH 3T3 cells and that this change depends on expression of the ras oncogene. As part of our studies on mechanisms by which ras may induce metastasis, we investigated expression and activity of two cysteine proteinases, cathepsin L (major excreted protein) and cathepsin B, as well as cysteine proteinase inhibitor activity, in ras‐transformed NIH 3T3 cells. In a series of cell lines that expressed differing amounts of ras, we found a good correlation between levels of ras expression and cathepsin L expression (r = 0.80). There was also a good correlation between secreted procathepsin L protein levels and experimental metastatic ability (r = 0.88). We found a similar but less strong association between cathepsin B levels and metastatic ability in these cells (r=0.76 and r=0.72 for 2.2‐kb and 4.1‐kb transcripts, respectively). Functional cathepsin L plus B activity (both secreted and cell‐associated) was found to be higher in ras‐transformed cells and was dependent on cell confluency in culture. Coupled with increased expression and activity of cysteine proteinases, ras‐transformed NIH 3T3 cells showed reduced cysteine proteinase inhibitor activity. We conclude that the balance between expression of cysteine proteinases and their inhibitors may be coregulated by ras expression. Our results suggest that ras‐induced increases in production of degradative enzymes such as cathepsins L and B, along with decreased activities of their inhibitors, may contribute to the increased malignant properties of ras‐transformed NIH 3T3 cells. © 1992 Wiley‐Liss, Inc.