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Biomedical subjects

C C Harris

Publications and source records attributed to C C Harris.

At least 109 records · Page 6Linked to original sources
PubMed1996

Molecular analysis of the cyclin-dependent kinase inhibitor genes p15INK4b/MTS2, p16INK4/MTS1, p18 and p19 in human cancer cell lines.

Cyclin-dependent kinase-4 inhibitor genes (INK4) regulate the cell cycle and are candidate tumor-suppressor genes. To determine if alterations in the coding regions of the p18 and p19 genes, which are novel members of the INK4 family and if they correlate with the development of human cancer, 100 human cancer cell lines were analyzed. Two other INK4 gene family members, p15INK4b/MTS2 and p16INK4/MTS1 genes were also analyzed. Homozygous deletions of the p15INK4b/MTS2 gene were detected in 29 cancer cell lines. Thirty-five homozygous deletions and 7 intragenic mutations of the pl6INK4/MTS1 gene were also detected in these cell lines. Neither homozygous deletions nor intragenic mutations of the p18 and p19 genes were found except in an ovarian cancer cell line, SKOV3, harboring a single base pair deletion in exon 1 of p19. In p16INK4/MTS1 expression analysis, 5 cell lines with both authentic and alternative spliced p16INK4/MTS1 mRNA had no detectable p16INK4/MTS1 protein. These results suggest the hypotheses that either post-translational modification or enhanced degradation may be responsible for the lack of detection of the p16INK4/MTS1 protein. Using Western blot analysis, subsets of 26 human cancer cell lines were examined for p18 expression and 39 cell lines for p19 expression. All of these cell lines expressed the p18 or p19 protein, with the exception of SKOV3, which did not express p19. Therefore, the INK4 gene family may be divided into 2 groups. One group includes p15INK4b/MTS2 and p16INK4/MTS1, in which genetic and epigenetic alterations might contribute to the development of human cancers. The other group includes p18 and p19, in which somatic mutations are uncommon in many types of human cancer, and their role in human carcinogenesis and cancer progression is uncertain.

Carrier Proteins↗
PubMed1996

Structure and function of the p53 tumor suppressor gene: clues for rational cancer therapeutic strategies.

The p53 tumor suppressor protein is involved in multiple central cellular processes, including transcription, DNA repair, genomic stability, senescence, cell cycle control, and apoptosis. p53 is functionally inactivated by structural mutations, interaction with viral products, and endogenous cellular mechanisms in the majority of human cancers. This functional inactivation can, in some circumstances, produce resistance to DNA-damaging agents commonly used in cancer chemotherapy and radiotherapeutic approaches. Current research is defining the biochemical pathways through which p53 induces cell cycle arrest and apoptosis. Knowledge of these fundamental processes is leading to the identification of molecular targets toward which multimodality cancer therapies, using chemotherapeutic, immunotherapeutic, and gene-therapeutic strategies, can be based.

Animals↗
PubMed1996

The genomic structure of the gene encoding the human transforming growth factor beta type II receptor (TGF-beta RII).

The genomic structure of the human transforming growth factor-beta type II receptor gene (TGF-beta RII) was determined by two PCR-based methods, the "long distance sequencer" method and the "promoter finder" method. Genomic fragments containing exons and adjacent introns were amplified by PCR, and the nucleotide sequences were determined by direct sequencing and subcloning sequencing. The TGF-beta RII protein is encoded by 567 codons in 7 exons. This is the first report about the genomic structure of a gene that belongs to the serine/threonine kinase type II receptor subfamily. Knowledge of the genomic structure of the TGF-beta RII gene will facilitate investigation of the TGF-beta signaling pathway in normal human cells and of the aberrations occurring during carcinogenesis.

Amino Acid Sequence↗
PubMed1996

The XPB and XPD DNA helicases are components of the p53-mediated apoptosis pathway.

The molecular pathway of p53-dependent apoptosis (programmed cell death) is poorly understood. Because p53 binds to the basal transcription-repair complex TFIIH and modulates its DNA helicase activities, we hypothesized that TFIIH DNA helicases XPB and XPD are members of the p53-mediated apoptotic pathway. Whereas transfer of a wild-type p53 expression vector by microinjection or retroviral infection into primary normal human fibroblasts resulted in apoptosis, primary fibroblasts from individuals with xeroderma pigmentosum (XP), who are deficient in DNA repair and have germ-line mutations in the XPB or XPD gene, but not in the XPA or XPC gene, have a deficiency in the apoptotic response. This deficiency can be rescued by transferring the wild-type XPB or XPD gene into the corresponding mutant cells. XP-D lymphocytes also have a decreased apoptotic response to DNA damage by adriamycin, indicating a physiologically relevant deficiency. The XP-B or XP-D mutant cells undergo a normal apoptotic response when microinjected with the Ich-L, and ICE genes. Analyses of p53 mutants and the effects of microinjected anti-p53 antibody, Pab421, indicate that the carboxyl terminus of p53 may be required for apoptosis. Direct microinjection of the p53 carboxy-terminal-derived peptide (amino acid residues 319-393) resulted in apoptosis of primary normal human fibroblasts. These results disclose a novel pathway of p53-induced apoptosis.

Apoptosis↗
PubMed1996

Deletions and insertions in the p53 tumor suppressor gene in human cancers: confirmation of the DNA polymerase slippage/misalignment model.

We analyzed all published deletions and insertions in the p53 gene to assess the relevance of mutagenesis models. Almost all deletions and insertions can be explained by one or more of the following DNA sequence features: monotonic base runs, adjacent or nonadjacent repeats of short tandem sequences, palindromes, and runs of purines or pyrimidines (homocopolymer runs). Increased length of monotonic runs correlates positively with increased frequency of events. Complex frameshift mutations can be explained by the formation of quasi-palindromes, with mismatch excision and replication using one strand of the palindrome as a template. Deletions and insertions in the p53 tumor suppressor gene may reflect both spontaneous and carcinogen-induced mutagenesis.

Base Sequence↗
PubMed1996

Nitric oxide-induced p53 accumulation and regulation of inducible nitric oxide synthase expression by wild-type p53.

The tumor suppressor gene product p53 plays an important role in the cellular response to DNA damage from exogenous chemical and physical mutagens. Therefore, we hypothesized that p53 performs a similar role in response to putative endogenous mutagens, such as nitric oxide (NO). We report here that exposure of human cells to NO generated from an NO donor or from overexpression of inducible nitric oxide synthase (NOS2) results in p53 protein accumulation. In addition, expression of wild-type (WT) p53 in a variety of human tumor cell lines, as well as murine fibroblasts, results in down-regulation of NOS2 expression through inhibition of the NOS2 promoter. These data are consistent with the hypothesis of a negative feedback loop in which endogenous NO-induced DNA damage results in WT p53 accumulation and provides a novel mechanism by which p53 safeguards against DNA damage through p53-mediated transrepression of NOS2 gene expression, thus reducing the potential for NO-induced DNA damage.

Animals↗
PubMed1996

Intragenic mutations of the p16(INK4), p15(INK4B) and p18 genes in primary non-small-cell lung cancers.

The p15(INK4B), p16(INK4) and p18 genes are members of the gene family coding for inhibitors of cyclin-dependent kinases 4 and 6. p15(INK4B) and p16(INK4) are located at 9p21, a chromosomal region frequently deleted in many human neoplasms. To examine the role of these 3 genes in lung carcinogenesis, somatic mutations within the genes were analyzed by single-strand conformation polymorphism and DNA sequencing in 71 non-small-cell lung cancer (NSCLC) samples. Six somatic mutations in the p16(INK4) gene and 3 cases with a polymorphic allele were observed. Loss of heterozygosity in the p18 gene was found in 1 sample. We did not find any intragenic mutations in the p15(INK4B) or p18 genes. We conclude that p16(INK4) mutations play a role in the formation of some NSCLCs, whereas the involvement of p15(INK4B) and p18 is uncommon.

Base Sequence↗
PubMed1996

Somatic point mutations in the p53 gene of human tumors and cell lines: updated compilation.

In 1994 we described a list of approximately 2500 point mutations in the p53 gene of human tumors and cell lines which we had compiled from the published literature and made available electronically through the file server at the EMBL Data Library. This database, updated twice a year, now contains records on 4496 published mutations (July 1995 release) and can be obtained from the EMBL Outstation-the European Bioinformatics Institute (EBI) through the network or on CD-ROM. This report describes the criteria for inclusion of data in this database, a description of the current format and a brief discussion of the current relevance of p53 mutation analysis to clinical and biological questions.

CD-ROM↗
PubMed1996

Suppression of growth in vitro and tumorigenicity in vivo of human carcinoma cell lines by transfected p16INK4.

The function of p16INK4 as a putative tumor suppressor gene was examined by investigating its ability to inhibit the growth of cancer cell lines in vitro and tumor formation in vivo. A p16INK4 cDNA expression vector was transfected into five human cancer cell lines that varied in their p16INK4 and retinoblastoma (Rb) status. Suppression of colony-forming efficiency was seen in four cell lines. Of two cell lines wild type for p16INK4 but null for Rb protein expression, one (Hep 3B) showed inhibition of colony formation, whereas the other (Saos-2) did not. This observation may demonstrate involvement of p16INK4 independent of Rb. The transfected p16INK4 gene was frequently selected against and lost during continued growth in vitro. When compared to the colon carcinoma cell line (DLD-1),p16INK4-transfected DLD-1 clone 1 cells were less tumorigenic in athymic nude mice. Tumors arising from p16INK4-transfected DLD-1 clones, which were growth suppressed in vitro, either lost the integrated exogenous p16INK4 or expressed reduced amounts of p16INK4 protein. Therefore, p16INK4 was also selected against during tumor formation in vivo. These data are consistent with the hypothesis that p16INK4 is a tumor suppressor gene.

Animals↗
PubMed1996

Tissue-specific growth suppression and chemosensitivity promotion in human hepatocellular carcinoma cells by retroviral-mediated transfer of the wild-type p53 gene.

Selective expression of cytotoxic gene products in tumor cells is one of the goals of gene therapy for treating cancer. We are developing such a strategy for the treatment of human hepatocellular carcinoma (HCC) by linking the wild-type p53 (WT-p53) gene with HCC-associated transcriptional control elements (TCE) to achieve selective growth inhibition of retrovirally transduced HCC cells. Replication-defective, amphotrophic retroviruses were constructed containing a WT-p53 complementary DNA (cDNA) that is transcriptionally regulated by the HCC-associated alpha-fetoprotein (AFP) gene TCE. Expression of exogenous WT-p53 from this retroviral vector was limited to AFP-producing cells. Introduction of WT-p53 into AFP-positive HCC cells by retroviral infection markedly inhibited their clonal growth in monolayer and soft agar cultures, and increased the sensitivity of these cells to the chemotherapeutic drug, cisplatin. Therefore, restoration of WT-p53 expression in HCC cells, in combination with chemotherapeutic drugs, can be considered as a strategy for the therapy of human liver cancer.

Antineoplastic Agents↗
PubMed1996

The formation and evolution of the Society of Nuclear Medicine.

The Society of Nuclear Medicine was created and constructed by persons from many branches of medicine and the physical sciences, but it originated mostly in the mind of a chemist-physicist-engineer named Norman "Jeff" Holter. Because most medical organizations seemed to care little about the use of radioactive materials for medical purposes, Holter believed a new organization was necessary for their promotion. From its origin in 1954 as the Pacific Northwest Society of Nuclear Medicine, The Society of Nuclear Medicine became a national, multidisciplinary organization in 1956. Rapidly gathering strength with an expanding membership, it employed an administrator in 1959. With this administrator and a dedicated volunteer editor, publication of the Journal of Nuclear Medicine began. Over the next several years the Society evolved into an active force in the development of the application of radioactivity to medical applications. It generated significant internal initiatives and participated in the generation of several important external institutions. The Society of Nuclear Medicine developed a tradition of annual meetings with strong educational programs for all members. By nurturing and embracing the Technologist Section, the Society became a robust and representative organization for all who serve nuclear medicine. From these beginnings came the vigorous Society of Nuclear Medicine of today. Jeff Holter (1914-1983) would be justifiably proud.

History, 20th Century↗
PubMed1996

Chromosomal changes and progressive tumorigenesis of human bronchial epithelial cell lines.

A simian virus 40 (SV40)-transformed human bronchial epithelial cell line, BEAS-2B, underwent progressive changes, including the development of tumorigenicity, during extended in vitro passaging. Karyotypic changes occurred in parallel with the phenotypic changes. For the first 12 passages following viral transformation, there were random karyotypic changes. Immortalization occurred between passages 12 and 21, corresponding with the accumulation of four characteristic abnormal chromosomes-m-1: add(15)(p11.1); m-2: der(8;9)(q10;q10); m-3: add(16)(p13); and m-4: mar4- and the loss of one homolog of chromosomes 8, 15, 16, 21, and 22. With further passaging (from 21 to 63), the acquisition of weak tumorigenicity was observed, accompanied by an increased frequency of cells containing all four common abnormal chromosomes, m-1 through m-4, and missing one normal homolog of chromosomes 8, 15, 16, and 22. Four tumor cell lines (B39-TL, B39-TR, B61-T4 and B61-T7) were established from tumors induced by the injection of these weakly tumorigenic BEAS-2B 39th- and 61st- passage cells into athymic nude mice. One of the cell lines, B39-TL, is significantly more tumorigenic than the others. It is notable that B39-TL showed two specific abnormal chromosomes, del(3p);der(3;15) (q10;q10) and m-6; der(21)t(3;21)(p14.2;p12) inducing deletion of a short arm of chromosome 3. Fluorescence in situ hybridization analysis with a probe for protein tyrosine phosphatase-gamma demonstrated loss of heterozygosity in the 3p14 region. The development of step-wise karyotypic changes in this in vitro carcinogenesis model parallels changes documented in several common human cancers.

Animals↗
PubMed1996

An aflatoxin-associated mutational hotspot at codon 249 in the p53 tumor suppressor gene occurs in hepatocellular carcinomas from Mexico.

The p53 tumor suppressor gene is commonly mutated in human hepatocellular carcinoma (HCC). The most frequent mutation in HCC in populations exposed to a high dietary intake of aflatoxin B1 (AFB1) is an AGGarg-->AGTser missense mutation in codon 249 of the p53 gene. We analyzed HCCs from Monterrey, Mexico, for the codon 249ser hotspot mutation. We also analyzed the serum AFB1-albumin adduct levels of the donors and family members to measure the current AFB1 exposure in this population. Moreover, the presence of hepatitis B and/or C viral infection (HBV or HCV) was analyzed serologically in the patients. Tumor cells were microdissected from tissue sections and exon 7 p53 sequences were amplified by polymerase chain reaction from genomic DNA and sequenced directly. The serological tests for anti-p53 antibodies, HBV or HCV were done by ELISA. Immunohistochemical analysis of p53 protein was done using a polyclonal rabbit antiserum (CM-1). Eight of 21 cases were positive by p53 immunohistochemistry. Of the 16 cases sequenced for exon 7 of p53 three codon 249 AGGarg-->AGTser mutations were found. Serum antibodies recognizing p53 protein were found in one of 18 patients. Positive serology for HBV and/or HCV was found in 12 of 20 cases. The serum AFB1-albumin adduct levels in this population ranged from 0.54 to 4.64 pmol aflatoxin/mg albumin. These results indicate that dietary AFB1 and hepatitis viruses are etiological agents in the molecular pathogenesis of HCC in this geographic region of Mexico.

Adult↗
PubMed1996

p53 tumor suppressor gene: at the crossroads of molecular carcinogenesis, molecular epidemiology, and cancer risk assessment.

Carcinogenesis is a multistage process involving the inappropriate activation of normal cellular genes to become oncogenes, e.g., ras, and the inactivation of other cellular genes called tumor suppressor genes. p53 is the prototypic tumor suppressor gene that is well suited as a molecular link between the causes of cancer, i.e., carcinogenic chemical and physical agents and certain viruses, and the development of clinical cancer. The p53 tumor suppressor gene is mutated in the majority of human cancers. Genetic analysis of human cancer is providing clues to the etiology of these diverse tumors and to the functions of the p53 gene. Some of the mutations in the p53 gene reflect endogenous causes of cancer, whereas others are characteristic of carcinogens found in our environment. In geographic areas where hepatitis B virus and a dietary chemical carcinogen, aflatoxin B1, are risk factors of liver cancer, a molecular signature of the chemical carcinogen is found in the mutated p53 gene. A different molecular signature in the p53 gene is found in skin cancer caused by sunlight. Because mutations in the p53 gene can occur in precancerous lesions in the lung, breast, esophagus, and colon, molecular analysis of the p53 gene in exfoliated cells found in either body fluids or tissue biopsies may identify individuals at increased cancer risk. p53 mutations in tumors generally indicate a poorer prognosis. In summary, the recent history of p53 investigations is a paradigm in cancer research, illustrating both the convergence of previously parallel lines of basic, clinical, and epidemiologic investigation and the rapid translation of research findings from the laboratory to the clinic.

Animals↗