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Biomedical subjects

C C Bird

Publications and source records attributed to C C Bird.

At least 37 records · Page 2Linked to original sources
PubMed1994

A study of stabilisation of p53 protein versus point mutation in colorectal carcinoma.

Abnormalities of the p53 tumour suppressor gene occur in many types of cancer including approximately 60% of colorectal carcinomas. This study investigates in 47 colorectal carcinomas the relationship between stabilised p53 protein detected by immunocytochemistry (ICC), and p53 mutation. 27 cases stained positively with the antibody PAb1801. Sequencing of exons 5-8 revealed 19 mutations in 18 of these cases (one tumour contained two different mutations). A rapid, non-radioactive method was developed to screen for mutations in this region of the gene involving Single Strand Conformational Polymorphism analysis (SSCP) and a MspI restriction digestion. This screen detected 17/19 (89%) of the sequenced mutations, and a further four mutations in 20 PAb1801 negative cases that were confirmed by sequencing. Reproducibility of ICC in detecting stabilised protein was assessed by restaining the 47 cases with the antibody DO7 after pre-treatment to optimise detection. Fewer cases were negative with DO7 although overall concordance with PAb1801 was good. A substantial proportion of carcinomas with stabilised p53 as detected by ICC do not contain mutations in exons 5-8, whilst some mutations (the majority in exon 6) are not associated with stabilisation.

Base Sequence↗
PubMed1994

p53 dependence of early apoptotic and proliferative responses within the mouse intestinal epithelium following gamma-irradiation.

p53 is now well characterized as a tumour suppressor gene, with loss of normal p53 function being recorded as the commonest genetic event associated with human malignancy. In particular, its involvement with tumorigenesis within the intestine is well established. Normal p53 function has been shown to be crucial for the induction of apoptosis in tumour cell lines, murine thymocytes and murine haematopoietic cells following DNA damage. To elucidate further the role of p53 in the cellular response to DNA damage we have investigated the response to gamma-irradiation of crypt cells in vivo from the small and large intestine of mice bearing a constitutive p53 deletion. Four hours after gamma-irradiation, a time point at which wild type crypt cells show abundant apoptosis, crypt cells from p53-deficient mice differed in that they were completely resistant to the induction of apoptosis. The p53 dose dependence of this phenomenon was clearly shown by the intermediate level of apoptosis observed in p53 heterozygotes. Analysis of the mitotic index and the bromodeoxyuridine labelling index showed that two other responses of wild type crypts to gamma-irradiation, namely the G2 block and the reduction in bromodeoxyuridine incorporation, were both largely intact in p53 deficient animals. These observations demonstrate that p53 function is essential for a major component of the normal response to gamma-irradiation induced DNA damage in intestinal mucosal cells, and suggest that p53 deficiency permits a population of cells bearing DNA damage to escape the normal process of deletion.

Animals↗
PubMed1994

Tumour incidence, spectrum and ploidy in mice with a large deletion in the p53 gene.

In human tumourigenesis the tumour suppressor gene most commonly affected by mutation, inactivation or allele loss is p53. Loss of p53 function is associated both with failure to maintain a normal diploid status and inability to delete cells by apoptosis following DNA damage. To investigate further the role of p53 we have generated mice carrying a large deletion within the gene. All animals homozygous for this deletion develop spontaneous tumours, predominantly lymphomas, by the age of 6 months. 10% of heterozygotes develop a range of neoplasms, with a lower predisposition towards lymphoma, by 9 months. Both tumour incidence and spectrum in heterozygotes differ from those previously reported in another p53 mutant stock, suggesting either difference in exposure to carcinogens between the two stocks, or a role for modulating genes within different genetic backgrounds. Tumours showed frequent loss of diploid status, and the majority of those arising in heterozygotes showed loss of the wild type allele. These findings are consistent with the concept that p53 acts as a tumour suppressor by preventing the propagation of DNA damage to daughter cells.

Alleles↗
PubMed1993

Thymocyte apoptosis induced by p53-dependent and independent pathways.

Death by apoptosis is characteristic of cells undergoing deletion during embryonic development, T- and B-cell maturation and endocrine-induced atrophy. Apoptosis can be initiated by various agents and may be a result of expression of the oncosuppressor gene p53 (refs 6-8). Here we study the dependence of apoptosis on p53 expression in cells from the thymus cortex. Short-term thymocyte cultures were prepared from mice constitutively heterozygous or homozygous for a deletion in the p53 gene introduced into the germ line after gene targeting. Wild-type thymocytes readily undergo apoptosis after treatment with ionizing radiation, the glucocorticoid methylprednisolone, or etoposide (an inhibitor of topoisomerase II), or after Ca(2+)-dependent activation by phorbol ester and a calcium ionophore. In contrast, homozygous null p53 thymocytes are resistant to induction of apoptosis by radiation or etoposide, but retain normal sensitivity to glucocorticoid and calcium. The time-dependent apoptosis that occurs in untreated cultures is unaffected by p53 status. Cells heterozygous for p53 deletion are partially resistant to radiation and etoposide. Our results show that p53 exerts a significant and dose-dependent effect in the initiation of apoptosis, but only when it is induced by agents that cause DNA-strand breakage.

Animals↗
PubMed1993

A PCR approach to discriminate between integrated and episomal HPV DNA in small clinical specimens.

HPV infection has long been implicated in the development of cervical carcinoma. There is strong evidence for association of high-risk HPV types 16 and 18 with cervical intraepithelial neoplasia (CIN) grades 2 and 3, and integration of viral DNA of these types into the host genome has been suggested to play an important role in progression to invasive cervical carcinoma. However, the existing techniques for detection of integrated DNA in clinical specimens are time-consuming and require large amounts of template DNA, often unavailable for small premalignant CIN lesions. In this study, a novel, two stage PCR assay was designed to discriminate between integrated and episomal HPV 16 DNA. The first stage was designed to determine whether intact HPV genomes were present. This initial PCR analysis of the entire viral genome in eight segments was successfully applied to authentic human cervical cancers. The second stage consisted of an ANCHOR-PCR-based analysis, developed specifically to discriminate between integrated and episomal HPV DNA, that was successfully tested with cloned HPV containing plasmids used to mimic both episomal and integrated viral DNA. Further optimization and validation will be required for application of the second stage to clinical specimens. The entire assay was developed to be applicable to small colposcopic biopsies or cervical scrape samples, representative of those acquired in routine clinical investigation of CIN 2 or CIN 3, in which determination of the physical state of HPV DNA may provide prognostically valuable information.

Base Sequence↗
PubMed1993

Human papillomavirus type 18 associates with more advanced cervical neoplasia than human papillomavirus type 16.

A type-specific, sensitive, polymerase chain reaction-based assay for human papillomavirus (HPV) types 6b, 11, 16, 18, and 33 was applied to 47 cervical carcinomas, 60 cases of cervical intraepithelial neoplasia (CIN), and 24 samples of histologically normal cervix. As expected, the combined incidence of the common high-risk genital HPVs (types 16 and 18) was high in carcinomas (79%) and CIN 2/3 (60%), low in CIN 1 (25%), and nonexistent in the normal controls. Analysis of the data by viral type and pathology revealed statistically significant differences that consistently pointed to an association of HPV 18 with more advanced disease than HPV 16. This was exemplified by calculation of the relative HPV frequency in squamous cancers and CIN 2/3 lesions, which gave cancer to CIN prevalence ratios of 1.2 for HPV 16 and 2.3 for HPV 18, a twofold difference suggesting the possibility that there is a greater risk of progression or a more rapid transition to malignancy associated with HPV 18. Furthermore, HPV 16 was associated with 2.5-fold more cancers showing squamous differentiation (58%) than HPV 18 (23%), but both types showed an identical prevalence of 41% in the clinically more sinister adenocarcinomas, indicating that there may be an association between HPV type and cancer cell differentiation.

Adenocarcinoma↗
PubMed1993

Cervical carcinoma: low frequency of allele loss at loci implicated in other common malignancies.

Twenty cervical carcinomas were examined for loss of heterozygosity (LOH) using 22 RFLP markers, which mapped to regions of putative oncosuppressor gene loci, identified as candidates in other common solid tumours. Allele losses were identified in six of the eight chromosomal arms examined, but at a significantly lower frequency than that reported in other common solid tumours. No association was observed between allele losses at any chromosomal location and the presence or integration of 'high risk' types of HPV determined by a sensitive, specific PCR method. HPV 16, 18 or 33 were found in the majority (75%) of these tumours. We have looked at only a limited subset of chromosomal regions, but the results, so far, imply that carcinoma of the cervix may arise by different molecular events than other common solid tumours, and support the view that one of the distinctive events may be infection with HPV. Alternatively, similar molecular events may be occurring, but in regions of the genome not yet identified as targets in other solid tumours.

Alleles↗
PubMed1993

PCR analysis of the upstream regulatory region of human papillomavirus genomes in cervical intraepithelial neoplasia and cervical carcinoma.

AIMS: To test whether human papillomavirus (HPV) variants with large scale sequence alterations to the upstream regulatory region are present in cervical intraepithelial neoplasias (CIN) and cervical carcinomas. METHODS: New PCR based assays were designed specifically to detect large scale insertion/deletion alterations in the upstream regulatory region of HPV 16 and 18. The assays were applied to 24 cases of CIN and 34 cases of cervical carcinoma previously shown to contain these two high risk HPV types. RESULTS: No large scale sequence alterations were found in any of the HPV containing CIN or carcinomas. CONCLUSIONS: These negative findings suggest that major upstream regulatory region variants of HPV 16 and 18 do not contribute to most cervical neoplasms.

Base Sequence↗
PubMed1993

Deletion mapping in colorectal cancer of a putative tumour suppressor gene in 8p22-p21.3.

Although previous studies of acquired loss of heterozygosity (LOH) in colorectal tumours have suggested that a tumour suppressor gene may lie within the short arm of chromosome 8, its precise localisation remains to be determined. To obtain a more accurate positional map 120 colorectal cancers were examined with eight chromosome 8 polymorphic markers comprising both restriction fragment length polymorphisms and microsatellite polymorphisms based on (CA)n repeats. 91 cases were informative and LOH was detected in 47 (51%). The markers most commonly sited within the lost region mapped to the lipoprotein lipase gene (LPL) at chromosome 8p22. From study of tumours showing break-points within 8p, a common region of deletion was established extending centromerically from LPL to the ankyrin 1 gene (ANK1) which is mapped to 8p21.1-11.2. This overlaps with common deleted regions observed in other studies of colorectal tumours (8p23.1-p21.3) and bladder tumours (8p21-q11.2). Taken together, the results in colorectal cancer delineate a region in 8p22-p21.3 where the putative tumour suppressor gene must lie. The chromosome 8p deletions appear to be independent of those involving 5q and 17p in the same tumours. No relationship was found between the presence of 8p deletion and site or stage of the tumour, or the sex or age of the patient at diagnosis.

Animals↗
PubMed1993

Stabilised p53 facilitates aneuploid clonal divergence in colorectal cancer.

Mutations in the p53 tumour suppressor gene are amongst the most frequent genetic abnormalities acquired in tumours. Recent studies in vitro suggest that mutant p53 destabilises the genome and facilitates development of aneuploidy. Here, in a study of 83 colorectal carcinomas, we demonstrate that alterations in p53 (detected by immunocytochemical stabilisation) precede and apparently facilitate divergence of aneuploid sub-clones. Aneuploidy in these tumours (but not those with normal p53) is predominantly in the subtetraploid range, suggesting that endoreduplication is important in its origin. This association with a specific phase of carcinoma progression is not shared by other commonly acquired genetic abnormalities in these tumours. These observations highlight the critical role of p53 in the regulation of abnormal chromosome replication and afford an explanation for the association between p53 abnormalities, aneuploidy and biological aggression in cancer.

Adenoma↗
PubMed1992

Recombinant DNA technology and its diagnostic applications.

As yet recombinant DNA technology does not appear to have widespread diagnostic application in pathology. However, it does have a useful role to play in specific circumstances in at least three main areas: a it can provide precise diagnostic information about genetic diseases, allowing appropriate counselling, and indicating future directions for research on therapeutic intervention, e.g. gene therapy; b micro-organisms can be identified more sensitively and specifically, in fresh or fixed tissue samples, and their genomes can be analysed in fine detail, providing information relevant to the aetiology, epidemiology and pathogenesis of many diseases; c in tumour pathology the main application so far has been to resolve diagnostic problems associated with leukaemias and lymphomas, when other diagnostic procedures have been inconclusive. Specific chromosomal translocations, involving recognized genes, are particularly amenable to diagnosis by these means. Diagnostic applications to solid tumours are yet to be identified, although significant insights into tumorigenesis have been obtained, and these may ultimately lead to the development of useful markers for prognostic and therapeutic purposes.

Base Sequence↗
PubMed1992

Prognostic significance of tumor deoxyribonucleic acid content in surgically resected small-cell carcinoma of lung.

The prognostic role of deoxyribonucleic acid flow cytometry was investigated in 53 cases of surgically resected small-cell lung cancer. Deoxyribonucleic acid aneuploidy was detected in 26 patients (49.1%), the remaining tumors being either diploid or tetraploid. Patients with aneuploid tumors had a significantly reduced 2-year survival (38.5%) when compared with patients with diploid or tetraploid tumors (70.3%; p less than 0.05). This finding was independent of tumor stage on multiple logistic regression analysis. Diploid or tetraploid deoxyribonucleic acid content was associated with a particularly good 2-year survival (85%) in N0 or N1 disease. Tumor deoxyribonucleic acid ploidy should be taken into account in planning of management and assessment of prognosis in small-cell lung cancer.

Carcinoma, Small Cell↗
PubMed1991

HPV in full thickness cervical biopsies: high prevalence in CIN 2 and CIN 3 detected by a sensitive PCR method.

A new type-specific, sensitive, non-radioactive assay is described for the detection of human papillomavirus (HPV) DNA in tissues. Sequences within the E6 gene were amplified by the polymerase chain reaction (PCR), using primer pairs which clearly distinguish HPV types, including those with close sequence homology such as 6b and 11. The amplified DNA products were identified by non-radioactive oligonucleotide hybridization and restriction endonuclease mapping, and the method was sufficiently sensitive to detect between 3 and 5 SiHa cells (each containing 1-2 copies of HPV 16 DNA) amongst 10,000 non-HPV-containing cells. Frozen and archival paraffin sections were equally acceptable substrates for the reaction. The assay was applied to frozen sections of full thickness cervical epithelium from 60 cases of cervical intraepithelial neoplasia (CIN) and 24 normal cervical controls. HPV DNA was detected in 60 per cent of cases of CIN 3 and CIN 2, in 25 per cent of cases of CIN 1, and in none of the normal controls. Prevalence of HPV 16 was similar (approximately 50 per cent) in both CIN 2 and CIN 3, and in the whole series HPV 16 was almost five-fold more common than HPV 18. Low-risk HPV types were present in 5 per cent of CIN 1, but 0 per cent of CIN 2 and CIN 3 biopsies. The data emphasize the biological similarity of CIN 2 and CIN 3 lesions, and their divergence from CIN 1.

Adolescent↗
PubMed1991

MCC, a candidate familial polyposis gene in 5q.21, shows frequent allele loss in colorectal and lung cancer.

MCC is a gene located within human chromosome band 5q.21 that shows somatically acquired mutations in colorectal cancer, and may be identical to the gene responsible for inheritance of familial adenomatous polyposis. Here we demonstrate that alleles contiguous with or within MCC are deleted in a high proportion of sporadic colorectal carcinomas. Of 106 carcinomas that were informative concurrently at close-flanking sites both centromeric and telomeric to MCC, 41.5% showed acquired allele loss contiguous with MCC. Evidence is presented to show that the true frequency of loss of MCC alleles is higher still. In contrast, allele losses in chromosome 5 that were incompatible with involvement of MCC were very rare (2% of a total series of 201 informative tumours). Interstitial deletion was the commonest mechanism of allele loss, and L5.71-3, a probe known to include coding sequences of MCC, marks the most consistently deleted site. Moreover mapping of chromosome breakpoints with six probes within 5q.21 sited the common critical deletion in a 2.5 Mb region which included L5.71-3. However use of L5.71-3 itself suggested that critical deleted regions may lie on either side of the probed sequence. The simplest explanation for this unexpected finding is that MCC itself is the essential deleted gene, the lost exons lying sometimes centromeric to, sometimes telomeric to and occasionally within the region detected by L5.71-3. Tumours in which MCC-related alleles were lost by interstitial deletion were in general larger than those with other mechanisms of acquired homozygosity (e.g. mitotic recombination), but there were no other obvious associations with clinicopathological features. Between 20% and 25% of lung cancers also showed acquired allele losses contiguous with MCC. The significance of this observation is still to be determined, as lung tumours show allele losses at many other sites, but the specificity of the probes used in this study does establish that the 5q.21 losses in these tumours are compatible with involvement of MCC.

Adenomatous Polyposis Coli↗
PubMed1991

p53 expression in colorectal tumors.

The expression of the nuclear phosphoprotein p53 was studied immunohistochemically in a series of 150 benign and malignant colorectal tumors. Using monoclonal antibody PAb1801, tumors divided unequivocally into two groups on the basis of immunohistochemistry. Forty of the carcinomas (46.5%) showed positive staining but only 4 of the adenomas (8.7%) were positive (P less than 0.001). The few positive adenomas always showed moderate or severe dysplasia. Metaplastic polyps (n = 9) and small familial adenomatous polyposis-related adenomas (n = 9) were uniformly negative. Carcinomas with p53 expression did not differ from those without in terms of site, differentiation or the prognostic indicators of Dukes' stage, DNA ploidy, or tumor histology. The improved morphologic resolution available in periodate lysine paraformaldehyde dichromate (PLPD)-fixed, paraffin-embedded tissue permitted several conclusions to be made: p53 is confined to neoplastic nuclei; staining in positive tumors is heterogeneous and often more marked at the infiltrative margins; and staining intensity is dramatically reduced in mitotic cells. It is concluded that expression of immunohistochemically detectable p53 (probably representing mutated forms of the protein) occurs in some adenomas around the time of transition to carcinoma. Therefore there is an association with the appearance of infiltrative behavior but not with degree of tumor progression (including metastasis) at the time of resection.

Adenomatous Polyposis Coli↗
PubMed1990

Intratumoral heterogeneity of DNA content in lung cancer.

Heterogeneity of DNA content was analyzed in 208 samples from 20 resected lung tumors. Only one carcinoma was homogeneously diploid, but the others had DNA aneuploidy in at least some tissue samples. Eighteen tumors (90%) had varying degrees of heterogeneity of DNA content. Over half of these could have been mislabeled as diploid if the tumors had not been widely sampled. The importance of adequate sampling in assessing ploidy status of lung tumors is emphasized.

Adenocarcinoma↗