Characterization of the human p53 gene

Sequence of a cDNA encoding the p53 protein in rhesus monkey (Macaca mulatta)

A 2184-nucleotide (nt) sequence of the p53 gene in Rhesus monkey (Macaca mulatta) was determined in order to facilitate the use of the Rhesus as an animal model in the testing of novel antisense oligodeoxyribonucleotides for a variety of human cancers, including acute myelogenous leukemia (AML). Within overlapping regions, we found greater than 95% identity between the Rhesus and human p53 sequences, and greater than 98% identity between Rhesus and African green monkey p53 sequences. The deduced amino acid (aa) sequence of the p53 protein is highly conserved between human and Rhesus monkey, with only 18 minor differences in 393 aa.

Negative effects of wild-type p53 and s-Myc on cellular growth and tumorigenicity of glioma cells. Implication of the tumor suppressor genes for gene therapy

Human (U251, U87, U343) and rat glioma cell lines (C6, 9L) were examined by the reverse transcriptase-polymerase chain reaction and subsequent nucleotide sequencing analysis to see whether they express wild type (wt)-p53 or mutated form (mut)-p53 messages. Results showed that U87, U343, and C6 cells expressed wt-p53 messages whereas U251 and 9L cells expressed mut-p53 messages. All these cell lines were transfected with wt-p53 cDNA or the s-myc gene linked to the mouse mammary tumor virus (MMTV) promoter. Of several G418-resistant clones obtained from each transfection, a few expressed the s-Myc or wt-p53 proteins. Independent of mutations in the intrinsic p53 gene, the cellular growth in vitro and tumorigenicity in nude mice of these clones were drastically suppressed, the extent of suppression being correlated with the expression level of the transfected gene. Flow-cytometric analysis demonstrated that both p53 and s-Myc arrested the cell cycle at the G1/S boundary. These data suggest that these genes having negative effects on tumor cell proliferation could be used in gene therapy of gliomas, which are caused by alteration of the p53 gene or by some other genetic change.

Paraffin section p53 protein immunohistochemistry in neuroectodermal tumors

In an attempt to characterize the role of p53 alterations in the pathogenesis of intracranial neuroectodermal tumors, 196 tumors were immunostained with a monoclonal antibody against the p53 protein on archival materials of formalin-fixed, paraffin-embedded materials. Only 11% of well differentiated astrocytomas stained positive, whereas up to 40% of high-grade astrocytomas (anaplastic astrocytomas and glioblastoma multiforme) were immunolabelled. The extent of immunolabelling of tumor cells also increased from the low-grade to high-grade astrocytomas. Among the high-grade astrocytomas, the small anaplastic cells were the predominant cell type which exhibited aberrant p53 protein accumulation. Rare cases of oligodendrogliomas and medulloblastomas also stained positive, whereas ependymomas and choroid plexus tumors were uniformly negative. p53 alterations therefore appear to play a role in the progression from low-grade to high-grade astrocytomas and the cell type which appeared to be critically involved appeared to be the small anaplastic cells.

Localization of p53 protein and human papillomavirus in anogenital squamous lesions: immunohistochemical and in situ hybridization studies in benign, dysplastic, and malignant epithelia

p53 Protein is a 53-kd nuclear phosphoprotein believed to play an important role in controlling proliferation of neoplastic and normal cells. This "natural tumor suppressor" can be rendered ineffective (or oncogenic) by mutations in the p53 gene or by interactions with proteins synthesized by DNA-transforming viruses, including specific subtypes of human papillomavirus (HPV). We describe the localization of p53 protein in association with HPV in paraffin sections of a spectrum of benign, dysplastic, and malignant anogenital squamous epithelia using immunohistochemical and in situ hybridization techniques. p53 Was detected in 81% of the 48 cases studied. Immunoreactivity for p53 was seen in 83% of the benign and low-grade squamous intraepithelial lesions (SILs), in 73% of the high-grade SILs, and in 86% of the infiltrating squamous carcinomas. In high-grade SILs p53 staining was frequently observed in individual nuclei at various levels of the abnormal epithelium and in the basal layer of the adjacent epithelium, while in squamous metaplasia and low-grade SILs immunostaining for p53 was limited to the basal layer of the epithelium. p53 Was detected in a slightly higher percentage of HPV-positive than HPV-negative epithelia as determined by in situ hybridization. No correlation was observed between p53 immunoreactivity and HPV subtypes. p53 Protein and HPV were detected in anal lesions from a small group of human immunodeficiency virus-positive individuals. Antibodies currently available mainly demonstrate mutant forms of p53 protein that are associated with longer half-lives than the wild-type protein, but demonstration of p53 protein overexpression is not necessarily indicative of malignancy.

Anchor residue motifs of HLA class-I-binding peptides analyzed by the direct binding of synthetic peptides to HLA class I alpha chains

The binding characteristics of the primary anchor residue motifs reported for HLA-A2 (A*0201, A*0205) and HLA-B27 (B*2705) alleles were investigated by a direct binding assay of the pertinent synthetic peptides to HLA class I alpha chains derived from a panel of HLA homozygous B-cell lines of various HLA phenotypes, including four A2 subtypes. The assay is based on a serologic detection of the conformational change of HLA class I alpha chains induced by binding to specific peptides in the presence of beta 2m. It is applicable to test a large number of HLA allelic products and synthetic peptides. Assay data confirmed the high allele specificity of the anchor residue motifs tested, but also revealed the intra- and interlocus cross-reactivity of these motifs. In the case of A2 anchor motifs, not only a broad cross-reactivity within the A2 subgroup, but also cross-reactivities with A24, A26, A28, and A29 were observed. With B27 anchor motifs, an interlocus cross-reactivity with A3 and A31 was seen. Several peptides, even though they carried A2 or B27 major anchor residue motifs, failed to bind to the relevant alpha chains, suggesting that the presence of a primary anchor residue motif is necessary for HLA class-I-peptide binding but is not by itself sufficient to guarantee binding.

p53 gene mutations and 17p allelic deletions in hepatocellular carcinoma from Japan

BACKGROUND

p53 gene mutations at codon 249 have been reported in hepatocellular carcinoma (HCC) from China and South Africa, a phenomenon shown to be closely associated with food contamination by aflatoxin. There have been few reports, however, in regard to p53 gene mutations in HCC from other geographic areas.

METHODS

The authors analyzed 20 HCC from Japan for alteration of the p53 gene by restriction fragment length polymorphisms and for nucleic acid mutations by polymerase chain reaction with direct sequencing.

RESULTS

Alterations associated with the p53 gene were found in 6 of 20 HCC (30%). Allelic loss of chromosome 17p occurred in 5 of 14 informative (heterozygous) cases (36%). Mutations in the p53 gene were detected in three cases (15%), at codons 176 (exon 5), 236 (exon 7), and 294 (exon 8). These cases were different from the HCC cases from China and South Africa, where point mutations in the p53 gene were reported at the same codon 249 in half of the cases and where aflatoxin food contamination and hepatitis B virus infection are recognized risk factors of HCC. No p53 gene alterations were found in smaller HCC (< 3 cm) or at earlier stages.

CONCLUSIONS

In Japan, p53 gene alterations seem to be a late event in the progression of hepatocarcinogenesis, which is often associated with persistent infection by the hepatitis C or B virus, but not usually with exposure to aflatoxin.

p53 immunoreactivity in human malignant melanoma and dysplastic naevi

Expression of the tumour suppressor protein, p53, was determined in 77 cutaneous melanocytic lesions, and in five lymph node metastases from malignant melanoma, in an immunohistochemical study employing CM-1, an antiserum raised against recombinant human p53 protein. Because wild-type p53 protein is rapidly degraded in normal cells, p53 immunoreactivity suggests the presence of an abnormally stable p53 protein. This may occur through either post-translational mechanisms or gene mutation. A highly significant correlation was found between p53 immunoreactivity and malignancy in melanocytic lesions (P < 0.0001). Overall, p53 immunoreactivity was observed in 63% of tumour specimens examined, but not in benign melanocytic naevi, although occasional foci of weak nuclear p53 immunoreactivity were observed in a minority of dysplastic naevi and a solitary Spitz naevus. A significant correlation was also found between strong p53 immunoreactivity and malignant melanomas associated with a poor prognosis (P = 0.008). These data suggest an important role for p53 tumour suppressor protein in the biology of human cutaneous malignant melanoma.

Human papillomaviruses, tumour suppressor genes and cervical cancer

There is now a considerable body of evidence that links HPV infection with anogenital squamous carcinoma, particularly for specific 'high risk' HPV types (HPV16 and 18) and invasive carcinoma of the cervix. Recent advances in the molecular study of these viruses have elucidated some potential mechanisms by which they may contribute to the development of these diseases. In this review we concentrate on the interactions of 2 of the HPV encoded proteins, E6 and E7, with cellular tumour suppressor gene products. We provide a model of how these interactions may be important in tumourigenesis and draw together current knowledge of this exciting and rapidly evolving field.

Neoplasia of the ampulla of Vater. Ki-ras and p53 mutations

Eleven tumors of the ampulla of Vater (5 stage IV and 2 stage II adenocarcinomas, 1 stage II papillary carcinoma, 1 neuroendocrine carcinoma, and 2 adenomas, one with foci of carcinoma) were examined for Ki-ras and p53 gene mutations by single-strand conformation polymorphism analysis and direct sequencing of polymerase chain reaction-amplified DNA fragments. Ki-ras mutations were found in one adenocarcinoma and in the adenoma with foci of carcinoma, both involving mainly the intraduodenal bile duct component of the ampulla. Seven cases showed p53 gene mutations: four advanced-stage adenocarcinomas, the papillary carcinoma, the neuroendocrine carcinoma, and the adenoma with foci of carcinoma. Nuclear accumulation of p53 protein was immunohistochemically detected in the morphologically high-grade areas of the five cancers harboring a p53 gene missense point mutation. The adenomas, the two frame shift-mutated cancers, and the adenomatous and low-grade cancer areas of mutated carcinomas were immunohistochemically negative. Our data suggest that in ampullary neoplasia 1) p53 mutations are common abnormalities associated with the transformation of adenomas and low-grade cancers into morphologically high-grade carcinomas, and 2) Ki-ras mutations are relatively less frequent and might be restricted to tumors originating from the bile duct component of the ampulla.

p53 and the Li-Fraumeni syndrome

The Li-Fraumeni familial cancer syndrome was initially described in 1969 in a retrospective epidemiologic review of more than 600 pediatric sarcoma patients. The clinical definition of the syndrome has been refined in the last two decades by prospective analyses of several families. Despite these exhaustive studies, the gene or genes responsible for the unusual constellation of tumors in these families remained elusive until 1990, when it was demonstrated that germline abnormalities of the p53 tumor suppressor gene could account for the occurrence of cancer in many classic Li-Fraumeni families. Identification of the molecular events that yield this phenotype has led many researchers to pursue several lines of investigation to improve our understanding of the significance of such alterations. We discuss the clinical, epidemiologic, genetic, and biologic aspects of the association between p53 and the Li-Fraumeni family cancer syndrome.

HLA class I binding of synthetic nonamer peptides carrying major anchor residue motifs of HLA-B27 (B*2705)-binding peptides

Eight nonamer peptides that comply with the major anchor residue motifs (the combination of amino acid residues at positions 2 and 9), R - K and R - R, of HLA-B27 (B*2705)-binding peptides were synthesized and tested for their direct binding to HLA class I alpha chains by the HLA class I alpha chain refolding assay previously described. One was a known B27 (B*2705)-binding heat shock protein peptide, HSP89 alpha (201-209), and the other seven were derived from the sequence of wild-type P53, a human tumor suppressor protein. A total of 36 HLA class I allospecificities were tested. HSP89 alpha (201-209) and two P53 peptides, P53 (362-370) and P53 (378-386), all possessing the motif R - K, bound strongly to B27 (B*2705) alpha chains. A weak binding was seen for P53 (272-280) and P53 (334-342), both showing the motif R - R. Most of these B27-binding peptides were found to bind to A3 alpha chains as well. In addition, P53 (173-181) and P53 (334-342), both with the R - R motif, showed substantial binding with A31 alpha chains. All the peptides carrying the motif R - K also showed weak binding with A31 alpha chains. The remaining two peptides, P53 (201-209) and P53 (282-290), with the motif R - R, did not show significant binding with any of the alpha chains tested. This study demonstrates both the specificity of peptide binding to a given HLA allelic product and the occurrence of cross-peptide-binding between the allelic products of different HLA loci.

Immunohistochemical analysis of p53 protein overexpression in normal, premalignant, and malignant tissues of the cervix uteri

Two hundred and thirty-eight cervical lesions ranging from normal to malignant were examined for overexpression of p53 protein. Whereas p53 protein was identified in 62 per cent of invasive squamous cell carcinomas, 11 per cent of invasive adenocarcinomas, and 7 per cent of squamous cell carcinomas in situ, no staining was found in adenocarcinoma in situ, dysplastic tissue, condyloma, and normal tissue. In 9 per cent of the positive cases of invasive squamous cell carcinomas, 5-50 per cent of the tumour cells were immunoreactive for p53 protein, whereas the other positive specimens were characterized by only rare p53-positive cells. We conclude that in invasive cervical carcinomas widespread overexpression of p53 protein is unusual, but occasional positive nuclei can be found frequently. Furthermore, our results indicate that altered expression of p53 protein may be involved in the progression of cervical carcinomas.

A human putative lymphocyte G0/G1 switch gene homologous to a rodent gene encoding a zinc-binding potential transcription factor

G0S24 is a member of a set of genes (putative G0/G1 switch regulatory genes) that are expressed transiently within 1-2 hr of the addition of lectin or cycloheximide to human blood mononuclear cells. Comparison of a full-length cDNA sequence with the corresponding genomic sequence reveals an open reading frame of 326 amino acids, distributed across two exons. Potential phosphorylation sites include the sequence PSPTSPT, which resembles an RNA polymerase II repeat reported to be a target of the cell cycle control kinase cdc2. Comparison of the derived protein sequence with those of rodent homologs allows classification into three groups. Group 1 contains G0S24 and the rat and mouse TIS11 genes (also known as TTP, Nup475, and Zfp36). Members of this group have three tetraproline repeats. Groups 1 and 2 have a serine-rich region and an "arginine element" (RRLPIF) at the carboxyl terminus. All groups contain cysteine- and histidine-rich putative zinc finger domains and a serine-phenylalanine "SFS" domain similar to part of the large subunit of eukaryotic RNA polymerase II. Comparison of group 1 human and mouse genomic sequences shows high conservation in the 5' flank and exons. A CpG island suggests expression in the germ line. G0S24 has potential sites for transcription factors in the 5' flank and intron; these include a serum response element. Protein and genomic sequences show similarities with those of a variety of proteins involved in transcription, suggesting that the G0S24 product has a similar role.

Regulation of the specific DNA binding function of p53

The DNA binding activity of p53 is required for its tumor suppressor function; we show here that this activity is cryptic but can be activated by cellular factors acting on a C-terminal regulatory domain of p53. A gel mobility shift assay demonstrated that recombinant wild-type human p53 binds DNA sequence specifically only weakly, but a monoclonal antibody binding near the C terminus activated the cryptic DNA binding activity stoichiometrically. p53 DNA binding could be activated by a C-terminal deletion of p53, mild proteolysis of full-length p53, E. coli dnaK (which disrupts protein-protein complexes), or casein kinase II (and coincident phosphorylation of a C-terminal site on p53). Activation of p53 DNA binding may be critical in regulation of its ability to arrest cell growth and thus its tumor suppressor function.

Alterations in the levels of expression of specific cellular genes in adenovirus-infected and -transformed cells

There is increasing evidence that changes in the transcriptional program of cellular genes in virus-transformed cells can contribute to virus transformation. It is, therefore, important to study altered expression patterns of cellular genes in adenovirus-infected and -transformed cells. We have used 40 different cellular genes or gene segments as hybridization probes to analyze the cytoplasmic RNA from adenovirus type 2 (Ad2)-infected KB cells, from Ad5-transformed human cells (293) or from several Ad2- or adenovirus type 12 (Ad12)-transformed hamster cell lines. Many of the genes probed were not expressed in human or hamster cells. Transcription of the ADPRT and the heat shock protein 70 genes was increased in Ad2-infected KB cells and in 293 cells. In Ad2-infected KB cells, c-myc gene transcription was decreased. In 293 cells and in three adenovirus-transformed hamster cell lines (T637, BHK21-Ad2E1A-E1B, and BHK21-Ad2 HindIII-G), the transcription of the c-jun gene was increased, whereas c-myc transcription was decreased in the latter two cell lines. The data presented here demonstrate that, among 40 different mammalian gene probes, alterations in steady state levels of RNA were detected for five of these genes. These results suggest major alterations in transcription patterns in adenovirus-infected and -transformed cells.

p53 gene mutations in gastric and esophageal cancers

The presence of point mutation of the p53 gene in exons 5, 6, 7, and 8 was examined in 10 cases of gastric adenocarcinoma and 5 cases of esophageal squamous cell carcinoma by polymerase chain reaction and direct nucleotide sequencing. Mutations of the p53 gene were found in 5 cases of gastric cancer and 4 cases of esophageal cancer. The mutations in the stomach cancers consisted of four missence mutations (exons 5 and 8) and one frame shift (exon 7). In the esophageal cancers, three missence mutations (exons 6, 7, and 8) and one point mutation within the splice donor site of intron 5 were found. Of the seven missence mutations in the two cancers, five showed the transition from G to A and two from G to T. All these changes occurred in the highly conserved region of the p53 protein. These results suggest that mutations of the p53 gene are genetic events in the pathogenesis of gastric adenocarcinoma and esophageal squamous cell carcinoma.

The effect of parity, tumor latency and transplantation on the activation ofint loci in mmtv-induced, transplanted C3H mammary pre-neoplasias and their tumors

Mouse mammary tumor virus (MMTV) infection of mammary glands results in proviral insertion into host DNA and activation of cellular genes. Clonal expansion of cells bearing insertional mutations results in hyperplastic alveolar nodules (HAN) and tumors. HAN, transplanted into epithelium-cleared mammary fat pads, form hyperplastic alveolar outgrowths (HOGs). Previous work indicates the commonly MMTV-activated genes wnt-1 and int-2 are rarely affected in HOGs and HOG-derived tumors. To determine the basis of the dichotomy between the frequency of wnt/int gene activation in HOG-derived tumors and tumors from breeders of the identical inbred mouse strain, we compared the activation of wnt-1, int-2 and int-3 in tumors from virgin and breeding C3H mice, in consecutive primary tumors arising in individual C3H breeders and in C3H HOGs at early passages. Activation of wnt-1 or int-2 was rare in HOG-derived tumors (6% and 0%) compared with primary tumors in breeders (52% and 14%). int-3 was never found to be activated. wnt-1 was activated in the same percentage of primary tumors from virgins as from breeders. int-2 was activated only in tumors from breeders. wnt-1 activation also did not correlate with shorter tumor latency in multiple tumors from individual breeders. wnt-1 RNA was not detected in HOGs at early transplant generations, however, low levels of wnt-1 RNA were variably found in the epithelium of virgin mammary glands. We cannot explain why C3H HOGs and their derivative tumors develop without wnt-1 expression when the majority of C3H primary mammary tumors possess an MMTV-activated wnt-1 gene.

Overexpression of p53 protein in basal cell carcinomas of human skin

Basal cell carcinoma (BCC) of the skin is the most common human cancer, but its molecular-genetic pathogenesis is unclear. In many other types of cancer, mutations of the tumor-suppressor gene p53 occur frequently and may lead to overexpression of a long-lived mutant form of p53 protein. In this study, overexpression of p53 protein was detected immunohistochemically in 30 (83%) of 36 specimens of BCC of the head and neck. The same regions of tumor typically were reactive both with a monoclonal antibody (PAb240) specific for the mutant protein and with one (PAb1801) directed against an epitope common to both wild-type and mutant p53 protein. Keratinocytes of chronically sun-exposed epidermis adjacent to BCCs also focally overexpressed p53 protein in the majority of cases, whereas those of sun-protected buttock skin did not. Mutation of p53 may form an important part of the pathogenetic sequence in a majority of cases of BCC.

Germline mutations of the p53 tumor-suppressor gene in children and young adults with second malignant neoplasms

BACKGROUND

Acquired mutations in the p53 tumor-suppressor gene have been detected in several human cancers, including colon, breast, and lung cancer. Inherited mutations (transmitted through the germline) of this gene can underlie the Li-Fraumeni syndrome, a rare familial association of breast cancer in young women, childhood sarcomas, and other malignant neoplasms. We investigated the possibility that p53 mutations in the germline are associated with second primary cancers that arise in children and young adults who would not be considered as belonging to Li-Fraumeni families.

METHODS

Genomic DNA was extracted from the blood leukocytes of 59 children and young adults with a second primary cancer. The polymerase chain reaction, in combination with denaturant-gel electrophoresis and sequencing, was used to identify p53 gene mutations.

RESULTS

Mutations of p53 that changed the predicted amino acid sequence were identified in leukocyte DNA from 4 of the 59 patients (6.8 percent). In three cases, the mutations were identical to ones previously found in the p53 gene. The fourth mutation was the first germline mutation to be identified in exon 9, at codon 325. Analysis of leukocyte DNA from close relatives of three of the patients indicated that the mutations were inherited, but cancer had developed in only one parent at the start of the study.

CONCLUSIONS

These findings identify an important subgroup of young patients with cancer who carry germline mutations in the p53 tumor-suppressor gene but whose family histories are not indicative of the Li-Fraumeni syndrome. The early detection of such mutations would be useful not only in treating these patients, but also in identifying family members who may be at high risk for the development of tumors.

Clonal p53 mutation in primary cervical cancer: association with human-papillomavirus-negative tumours

Analyses of cancer cell lines and of anal cancers suggest an inverse correlation between infection with human papillomavirus (HPV) and somatic mutation of the p53 tumour-suppressor gene. We have investigated this association in primary cervical tumours. Tumour-tissue samples from 28 women with primary cancer of the cervix were analysed for presence of HPV sequences and for somatic mutations of the p53 gene. Southern blot analysis and the polymerase chain reaction (PCR) showed that 25 of the tumours contained HPV sequences; 20 were HPV16 positive and 5 HPV18 positive. 17 tumours subjected to restriction fragment length polymorphism analysis for the short arm of chromosome 17 showed no evidence of allelic deletion. Sequencing of the entire coding region of the p53 gene by asymmetric PCR detected heterozygous point mutations in only 3 HPV-negative tumours. By contrast, in 21 HPV-positive cancers the p53 sequence was wild-type throughout. Our data indicate that loss of wild-type p53 function is important in the pathology of cervical cancer and that in the absence of an HPV-encoded gene product that mediates loss of p53 function, somatic mutation of the gene is required. This pattern of p53 mutation may partly explain the apparently worse prognosis of HPV-negative cervical cancers.

Loss of the 17p chromosomal region in a metastatic carcinoma of the prostate

Genetic alterations of multiple loci that serve as markers for the induction and progression of disease have been identified in several adenocarcinomas, but not in adenocarcinoma of the prostate. To determine if similar genetic alterations occur in prostate carcinoma and could serve as markers for the extent of clinical disease, we have examined 23 predominantly moderately-differentiated, localized prostate carcinomas and one prostatic dysplasia for changes in the structure and copy number of ten selected genes. These genes include 1) those important to androgen metabolism in the prostate, the androgen receptor and steroid 5 alpha reductase genes; 2) those that map to the 10q (PLAU) and 7q (MET) chromosomal regions found deleted in some prostate carcinomas, and 3) proto-oncogenes (ERBB2, INT2, and MYC) and tumor suppressor gene loci (RB1, TP53 and D17S5) found altered in adenocarcinomas of the breast, colon and lung. Gene alterations were detected in one specimen, a lymph node metastasis from a poorly differentiated tumor. This specimen exhibited loss of heterozygosity for two loci putatively active in tumor suppression, TP53 and D17S5, on the short arm of chromosome 17. This study indicates that gross genetic alterations were not evident and could not be used as markers of tumor development in well- or moderately-differentiated, localized lesions, but that loss of the 17p region may be a useful marker for advanced carcinomas in the prostate.

Molecular events in late stages of T-cell functional maturation

Peripheral blood lymphocytes activated with either the calcium ionophore A23187 or the combination of anti-CD2 monoclonal antibodies, 9.6 + VIT13, undergo blast formation and proliferation but do not develop cytolytic activity. These proliferating blasts, referred to as pre-effector blasts because they do not yet express cytolytic function, respond to stimulation with interleukin-2 (IL-2) by further proliferation and development of cytolytic activity, i.e. they become effector cells. Pre-effector blasts activated with 9.6 + VIT13, but not A23187-activated pre-effector blasts, also respond to stimulation with interferon-gamma (IFN-gamma) by becoming cytolytic effector cells. This report examines gene expression (by Northern blot analysis) in pre-effector blasts and during the transition from the pre-effector to the effector stage. The data presented here provide further support for the concept that A23187 activation drives T cells to become dividing blasts that are appropriately referred to as 'pre-effector' cells in that these blasts do not express transcripts for granzyme A or perforin mRNA but are driven by IL-2 to do so in parallel with the acquisition of cytotoxic function. Cells are apparently driven by 9.6 + VIT13 to a later stage of functional maturation than by A23187 activation; 9.6 + VIT13-activated pre-effector blasts express mRNA for both granzyme A and perforin, even though these blasts do not express cytolytic activity. Activation via A23187 results in lower expression of the proto-oncogene c-myb relative to that found in either 9.6 + VIT13 or OKT3-activated cells.

Detection of multiallele polymorphisms within gene sequences by GC-clamped denaturing gradient gel electrophoresis

The ability to efficiently detect DNA polymorphisms is essential for the completion of a high-resolution polymorphic linkage map of the human genome. Currently the most informative polymorphisms are the multiallelic dinucleotide repeat polymorphisms. However, many gene sequences lack an associated dinucleotide repeat sequence. We used GC-clamped denaturing gradient gel electrophoresis to screen for DNA polymorphisms in the following six gene sequences: MCC, p53, prealbumin (transthyretin), rhodopsin, S-antigen, and TGF-alpha. A single-base sequence polymorphism was identified in each of these gene sequences. Some of these polymorphisms were multiallelic and highly informative. Our results demonstrate the value of denaturing gradient gel electrophoresis for both identifying and analyzing human DNA polymorphisms. The ability to detect highly informative polymorphisms within gene sequences will greatly contribute to a gene-based polymorphic linkage map.

Involvement of multiple chromosome 17p loci in medulloblastoma tumorigenesis

Loss of heterozygosity for sequences located on chromosome 17p in several tumor types is often associated with mutations in the tumor suppressor gene p53. We previously showed consistent deletion of chromosome 17p12-13.1 in medulloblastoma, a common childhood brain tumor. Using denaturing gradient gel electrophoresis and direct sequencing, we have detected p53 mutations in only two of 20 medulloblastoma specimens. Moreover, additional RFLP studies of these 20 specimens showed loss of heterozygosity at a more distal and distinct site, 17p13.3. Deletion of 17p almost invariably signified a negative prognosis. Our results suggest that p53 mutations may contribute to the pathogenesis of medulloblastoma in relatively few cases. The consistent deletion of other discrete loci on 17p suggests that additional or alternative tumor suppressor genes may contribute to the tumor's phenotype.

Missense mutations and a deletion of the p53 gene in human gastric cancer

To investigate the molecular pathogenesis of human gastric cancers the p53 gene, a suppressor oncogene, was analyzed in 12 human gastric cell lines. Southern blot and Northern blot analysis revealed a total deletion of p53 gene in KATO-III cells but no major abnormality of p53 gene in other cell lines. By the use of the reverse-transcriptase polymerase chain reaction and direct sequencing 7 cell lines showed point mutations of p53 gene resulting in amino-acid substitutions. Most of them were rare mutations which had not been observed in other types of cancers. One of these mutations was also detected through the use of PCR and oligomer-specific hybridization. Six out of 7 cell lines with mutations of p53 gene also lost one allele of chromosome 17p. Immunoblotting of cell lysates with an antibody specific to p53 demonstrated the absence of p53 protein in KATO-III cell. By contrast, the high levels of the p53 protein were observed in 5 cell lines all of which contained mutations of p53 gene. These results further suggest that the inactivation of p53 gene may play an important role in the transformation of gastric cells to the malignant phenotype. KATO-III cells might be a good model for studying the significance of the loss of p53 gene in cellular transformation.

Mutational analysis of a dominant oncogene (c-Ki-ras-2) and a tumor suppressor gene (p53) in hamster lung tumorigenesis

In human lung cancers, alterations of both a dominant oncogene (ras) and a tumor suppressor gene (p53) have been identified. Polymerase chain reaction (PCR) analysis of mRNA was used to amplify the c-Ki-ras-2 and p53 genes from Syrian golden hamsters. The PCR products were confirmed by predicted-size analysis, probing with nonradioactive (biotin-labeled) oligonucleotides, and direct sequencing. Lung tumors were produced in hamsters by repeated injections of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Of six tumors examined, three (50%) had mutations in codon 12 of Ki-ras. Examination of the conserved regions of p53 revealed no mutations. We conclude that NNK-induced carcinogenesis in the hamster results in characteristic alterations of Ki-ras but may not necessarily involve the p53 gene.

Low nucleotide diversity in man

The nucleotide diversity (pi) in humans is studied by using published cDNA and genomic sequences that have been carefully checked for sequencing accuracy. This measure of genetic variability is defined as the number of nucleotide differences per site between two randomly chosen sequences from a population. A total of more than 75,000 base pairs from 49 loci are compared. The DNA regions studied are the 5' and 3' untranslated regions and the amino acid coding regions. The coding regions are divided into nondegenerate sites (i.e., sites at which all possible changes are nonsynonymous), twofold degenerate sites (i.e., sites at each of which one of the three possible changes is synonymous) and fourfold degenerate sites (i.e., sites at which all three possible changes are synonymous). The pi values estimated are, respectively, 0.03 and 0.04% for the 5' and 3' UT regions, and 0.03, 0.06 and 0.11% for nondegenerate, twofold degenerate and fourfold degenerate sites. Since the highest pi value is only 0.11%, which is about one order of magnitude lower than those in Drosophila populations, the nucleotide diversity in humans is very low. The low diversity is probably due to a relatively small long-term effective population size rather than any severe bottleneck during human evolution.

TP53 gene mutations and 17p deletions in human astrocytomas

Astrocytomas, including the most malignant form, glioblastoma multiforme, are the most frequent and deadly primary tumors of the human nervous system. Recent molecular genetic analyses of astrocytomas have demonstrated frequent chromosome 17 deletions involving the telomeric region of the short arm (17p12-pter). This region contains a candidate tumor suppressor gene, TP53, which has recently been implicated in the etiology of a broad array of human cancers. To study the possible role of TP53 in astrocytoma development, 24 randomly chosen human astrocytic tumors were examined for genomic TP53 sequence aberrations using primer-directed DNA amplification in conjunction with direct sequencing. Five of the 11 grade III astrocytomas (glioblastoma multiforme), but only one of seven grade II astrocytomas (anaplastic astrocytoma) and none of either the grade I astrocytomas or oligodendrogliomas demonstrated distinct point mutations involving the TP53 gene. These data suggest that TP53 mutations may play a role in astrocytoma development and are predominantly associated with higher grade tumors.

Mutation in the TP53 gene in colorectal carcinoma detected by polymerase chain reaction

The human TP53 gene is a possible tumor suppressor since TP53 gene mutations are observed in greater than 70% of sporadic colorectal carcinoma DNAs. In genomic DNAs from seven colon cancer cell samples, a 405 base pair DNA fragment containing exon 5, intron 5, and exon 6 of the TP53 gene was amplified by polymerase chain reaction and analyzed for mutations. One sample [human colon cancer (HCC) 278] was found to have a TP53 mutation altering the amino acid glutamine 167 in exon 5. A deletion of 2 bases changed glutamine 167 (CAG) to alanine (GCA) and the resulting frame-shift produced an in-frame stop codon at amino acid 179. While the normal TP53 gene gives rise to a 53 kD protein, the estimated size of this mutant TP53 protein if expressed would be approximately 20 kD.

Loss of heterozygosity for chromosome 22 DNA sequences in human meningioma

Monosomy of chromosome 22 in meningioma was the first consistent cytogenetic anomaly reported for a solid tumor. Although most meningiomas are isolated sporadic lesions, multiple and familial occurrences have been reported, usually in cases of documented neurofibromatosis 2 (NF2). Previous reports have placed the NF2 locus on chromosome 22, flanked by the markers D22S1 and D22S28. We report a restriction fragment-length polymorphism study of 16 meningiomas conducted using chromosome 22 probes. None of the patients had clinical findings or a family history of NF2, although two of them eventually developed multiple intracranial meningiomas. Detectable loss of chromosome 22 sequences was observed in 50% of informative patients. Deletion mapping of tumors with preserved sequences showed that the loss of chromosome 22 DNA overlapped the region previously linked to NF2, but also included a sequence distal to the NF2 locus. These results suggest that the oncogenesis of human meningioma involves inactivation of a chromosome 22 locus that may be in close proximity to the gene for NF2.

Genetic mechanisms of tumor suppression by the human p53 gene

Mutations of the gene encoding p53, a 53-kilodalton cellular protein, are found frequently in human tumor cells, suggesting a crucial role for this gene in human oncogenesis. To model the stepwise mutation or loss of both p53 alleles during tumorigenesis, a human osteosarcoma cell line, Saos-2, was used that completely lacked endogenous p53. Single copies of exogenous p53 genes were then introduced by infecting cells with recombinant retroviruses containing either point-mutated or wild-type versions of the p53 cDNA sequence. Expression of wild-type p53 suppressed the neoplastic phenotype of Saos-2 cells, whereas expression of mutated p53 conferred a limited growth advantage to cells in the absence of wild-type p53. Wild-type p53 was phenotypically dominant to mutated p53 in a two-allele configuration. These results suggest that, as with the retinoblastoma gene, mutation of both alleles of the p53 gene is essential for its role in oncogenesis.

A chemical mismatch cleavage method useful for the detection of point mutations in the p53 gene in lung cancer

Point mutations in genes can be etiologic of pulmonary diseases, as in the case of the inherited disorders alpha-1-antitrypsin deficiency and cystic fibrosis or in the context of dominant and recessive oncogenes in lung cancer. Various methodologies have been developed to screen for single-base mutations. These techniques include direct DNA sequencing, RNase protection, denaturing gradient gel electrophoresis, and chemical mismatch cleavage. The latter method offers the advantages of rapid and efficient analysis of genomic or cDNA and is thus ideally suited to screening applications. Furthermore, all possible single-base changes can theoretically be detected. In the present work, chemical mismatch cleavage was utilized to detect mutations in the p53 gene in small cell and non-small cell lung cancer. This technique was modified by using a two-step, hemi-nested PCR procedure for preparation of target genomic DNAs permitting an expanded target size for analysis. Evaluation by chemical mismatch cleavage of eight p53 cDNAs derived from lung tumors shown to have different mutations by DNA sequencing correctly detected the presence of a point mutation in all instances. Analysis of six additional tumor genomic DNAs with defined mutations in the corresponding p53 cDNAs accurately confirmed the mutation at the level of the genome. The technique also identified codon 72 and intron 6 polymorphisms. Using the intron 6 polymorphism, loss of heterozygosity at the p53 locus in tumor DNA was readily detected by chemical mismatch cleavage. Finally, utilizing this technique for scanning analysis of the p53 gene of uncharacterized lung tumor DNAs, additional mutations were identified in a prospective manner which were confirmed by sequence analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Deletion mapping of the medulloblastoma locus on chromosome 17p

Isochromosome 17q has previously been observed consistently in cytogenetic studies of medulloblastoma, the most common posterior fossa neoplasm in children. We performed a restriction fragment length polymorphism (RFLP) investigation of medulloblastoma which showed a loss of chromosome 17p sequences in 45% of these tumors. This finding was predictive of a poor clinical response to treatment. A contiguous panel of markers permitted mapping of the deletion to 17p12-p13.1, the same chromosomal region for which loss of alleles has been shown in tumor specimens from patients with colon cancer, and the same region to which the p53 gene has been mapped. This suggests that medulloblastoma is associated with a recessive oncogene on chromosome 17p that may be involved in the genesis of several embryologically unrelated neoplasms and that the absence of this gene in tumor tissue has prognostic significance.

A splicing mutation accounts for the lack of p53 gene expression in a CML blast crisis cell line: a novel mechanism of p53 gene inactivation

Alterations of the p53 anti-oncogene have recently been found to occur frequently in the blast crisis of chronic myelocytic leukaemia. The p53 gene may be altered by gross structural alterations or by point mutations in the coding sequence. We now report a novel mechanism of gene inactivation in a blast crisis cell line where a mutation in a splice donor site at the 5' end of the fifth intron of the gene interrupts RNA processing and gene expression.

AccII polymorphism of the p53 gene

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Increased expression of mutant forms of p53 oncogene in primary lung cancer

Primary lung cancer samples of the major histological types were examined for expression of the tumor suppressor gene p53 by immunohistochemistry. Abnormalities in p53 expression were found in 28 of 40 carcinomas, 14 of 17 squamous tumours showing abnormal p53 expression, whereas no expression of p53 was detectable in 7 carcinoid tumours or in 10 normal lung samples. Direct evidence for homozygous expression of mutant p53 mRNA in representative carcinomas was obtained by means of an asymmetric polymerase chain reaction mRNA sequencing strategy, which allowed sequencing without any cloning step. All the mutations were G to T transversions resulting in mis-sense mutations in aminoacids highly conserved in evolution. Mutation of the p53 gene is the most frequently identified genetic change in human lung cancer; these findings suggest that simple immunohistological methods can provide strong evidence of such mutation.

A variation in the structure of the protein-coding region of the human p53 gene

An extensive analysis of genomic DNA preparations from a number of normal and malignant tissues revealed BglII site polymorphism of the human p53 gene. Approximately 10% of p53 gene alleles were found to contain an additional BglII site localized in a region of intron I. This allelic form of p53 gene was also responsible for p53 protein having altered electrophoretic mobility. Molecular cloning and sequencing of both the alleles of p53 gene revealed a base-pair change in codon 72 causing arginine----proline substitution in the allele with the additional BglII site. Both variants of the p53 gene may occur in homozygous state and are therefore functional.

The physical map of Mus musculus chromosome 11 reveals evolutionary relationships with different syntenic groups of genes in Homo sapiens

The physical localization of sequences homologous to three cloned genes was determined by in situ hybridization to metaphase chromosomes. Previous work had assigned the skeletal myosin heavy chain gene cluster (Myh), the functional locus for the cellular tumor antigen p53 (Trp53-1), and the cellular homologue of the viral erb-B oncogene (Erbb) to Mus musculus chromosome 11 (MMU11). Our results provide regional assignments of Myh and Trp53-1 to chromosome bands B2----C, and of Erbb to bands A1----A4. Taken together with in situ mapping of three other loci on MMU 11 (Hox-2 homeobox-containing gene cluster, the Sparc protein, and the Colla-1 collagen gene), which have been reported elsewhere, these data allowed us to construct a physical map of MMU11 and to compare it with the linkage map of this chromosome. The map positions of the homologous genes on human chromosomes suggest evolutionary relationships of distinct regions of MMU11 with six different human chromosome arms: 1p, 5q, 7p, 16p, 17p, and 17q. The delineation of conserved chromosome regions has important implications for the understanding of karyotype evolution in mammalian species and for the development of animal models of human genetic diseases.