Biomedical subjects

C C Bird

Publications and source records attributed to C C Bird.

At least 19 recordsLinked to original sources

PubMed1999

Heterogeneity studies identify a subset of sporadic colorectal cancers without evidence for chromosomal or microsatellite instability.

Two apparently independent mechanisms of instability are recognized in colorectal cancer, microsatellite instability and chromosomal instability. Evidence from colorectal cancer cell lines indicates the presence of either, or both, types of instability in the vast majority. Here, we sought to determine the prevalence of such instability in primary sporadic colorectal cancers. Microsatellite instability was established by demonstration of ovel clonal, nongerm-line alleles in at least two of four tested loci. Chromosomal abnormalities were identified by comparative genomic hybridization (CGH) and flow cytometric analysis of nuclear DNA content. Tumours harbouring chromosomal instability were distinguished from those with stable but aneuploid karyotypes by comparing chromosomal defects at multiple sites throughout each cancer. This analysis allowed assessment of both the number of chromosomal abnormalities and their heterogeneity throughout the tumour. The results confirm that microsatellite instability is consistently associated with multiple, repeated changes in microsatellites throughout the growth of the affected colorectal carcinomas. There were also several carcinomas in which major structural or numerical abnormalities in chromosomes had clearly continued to arise during tumour growth. However, a substantial subset of tumours showed neither microsatellite instability nor multiple, major chromosomal abnormalities. We suggest that the development of a proportion of colorectal cancers proceeds via a different pathway of carcinogenesis not associated with either of the currently recognized forms of genomic instability.

Aged↗

PubMed1999

Apoptosis and carcinogenesis.

Apoptosis has long been known to be effected through a common sequence of structural changes, despite the wide variety of initiating stimuli. These common structural events appear to depend upon activation of a set of enzymes (caspases) which direct a strongly conserved, terminal effector pathway. The regulation of this pathway, and in particular its coupling to DNA damage, appears to be critical in maintaining at low levels the number of mutated cells within tissues. The frequency with which tumours (experimental and human) bear deficiency in p53 or MSH-2 repair function may indicate the importance of these proteins in coupling DNA damage to apoptosis.

Animals↗

PubMed1998

Pathologists dislike sound? Evaluation of a computerised training microscope.

AIM: To evaluate the use of multimedia enhancements, using a computerised microscope, in the training of microscope skills. METHODS: The HOME microscope provides facilities to highlight features of interest in conjunction with either text display or aural presentation. A pilot study was carried out with 10 individuals, eight of whom were at different stages of pathology training. A tutorial was implemented employing sound or text, and each individual tested each version. Both the subjective impressions of users and objective measurement of their patterns of use were recorded. RESULTS: Although both versions improved learning, users took longer to work through the aural than the text version; 90% of users preferred the text only version, including all eight individuals involved in pathology training. CONCLUSIONS: Pathologists appear to prefer visual rather than aural input when using teaching systems such as the HOME microscope and sound does not give added value to the training experience.

Attitude of Health Personnel↗

PubMed1997

Renal allograft recipients with high susceptibility to cutaneous malignancy have an increased prevalence of human papillomavirus DNA in skin tumours and a greater risk of anogenital malignancy.

Renal allograft recipients (RARs) have a well-documented increased incidence of viral warts and cutaneous neoplasia, particularly those with long graft life and high sun exposure. A clinicopathological survey of 69 RARs in south-east Scotland, with follow-up periods of up to 28 years after transplantation, revealed marked variation in patient susceptibility to cutaneous malignancy with concomitant variation in HPV prevalence. Skin cancers were found in 34 patients. Eight patients showed high susceptibility [defined as more than four intraepidermal carcinomas (IECs) or invasive squamous cell carcinomas (SCCs)] 42 had intermediate susceptibility (1-3 IECs or SCCs, or >3 keratoses) and 18 had low susceptibility (< or = 3 keratoses and no cancers). SCCs, IECs and keratoses from the high-susceptibility group were found to have greater prevalences of human papillomavirus (HPV) DNA (56%, 45% and 50% respectively), than SCCs (0%) and IECs (33%) from intermediate-susceptibility RARs and keratoses (36%) from the combined intermediate- and low-susceptibility groups and compared with a group of immunocompetent controls (27%, 20% and 15% respectively). No differences in p53 protein accumulation, determined immunohistochemically, were observed in tumours from the three groups. Categorization of RARs by susceptibility to cutaneous malignancy provides clinically useful information, as significantly more high-susceptibility patients (38%) developed aggressive, potentially lethal anogenital or cutaneous squamous cell cancers than did patients in the intermediate group (5%, P=0.005) or the low-susceptibility group (0%).

Adult↗

PubMed1996

Microsatellite instability and the role of hMSH2 in sporadic colorectalcancer.

Microsatellite instability (MSI) occurs in most tumours from patients with hereditary non-polyposis colorectal cancer (HNPCC) and in around 17% of sporadic colorectal cancers. Germline defects in mismatch repair (MMR) genes are responsible for the majority of large HNPCC families, with hMSH2 accounting for at least 50%. MMR gene defects also occur in a small proportion of sporadic colorectal tumours with MSI. Here we report a systematic analysis of mismatch repair deficiency in 215 Scottish patients with sporadic colorectal tumours. We found that 16.4% of tumours exhibited MSI; survival analysis by Cox proportional hazards method showed a substantial survival advantage for patients with tumours showing MSI, independent of other prognostic factors. Tumours with MSI were screened for hMSH2 mutations and although 61% were found to have alterations, of these only 1/24 was exonic. The majority of these changes were reductions in length at intronic mononucleotide tracts and we postulate that these alterations are the result of a genetic defect elsewhere, although they may compromise hMSH2 function as a second step in tumourigenesis. Our findings indicate that instability confers an improved prognosis in colorectal cancer and, despite the fact that these two groups of tumours share similar biological characteristics, the genetic basis of HNPCC and sporadic colorectal cancer with MSI is different.

Base Sequence↗

PubMed1996

Ki-ras mutations in adenomas: a characteristic of cancer-bearing colorectal mucosa.

Activating mutations in the Ki-ras2 oncogene are frequently observed in sporadic colorectal adenomas and their incidence is reported to rise in large and tubulovillous adenomas to values close to those in carcinomas. This study shows that this property is a feature of adenomas growing in large bowel that has already demonstrated its propensity to engender malignant tumours: i.e., bowel in which there is a synchronous carcinoma. Adenomas from cancer-free bowel do not share this high incidence of Ki-ras mutations. This difference in mutation incidence between adenomas from cancer-free and cancer-bearing patients does not appear to derive from sampling bias relative to adenoma size, site, or patient age, nor is it found in another gene (APC) known to be of importance in adenoma formation. Large, dysplastic adenomas from cancer-bearing bowel, however, are particularly liable to carry Ki-ras mutations when they arise in patients over 70 years old. The observations suggest that the role of Ki-ras mutations may be more subtle than merely enhancing adenoma growth. Adenoma cells of cancer-prone individuals may suffer more mutational events than those in persons selected as cancer-free.

Adenoma↗

PubMed1995

17q allele loss is associated with lymph node metastasis in locally aggressive human colorectal cancer.

A consecutive series of 87 colorectal tumours were studied for loss of a polymorphic probe on chromosome 17q and of the 64 informative cases, 13 (20 per cent) showed loss of heterozygosity (LOH). Examples of LOH were found in carcinomas of all stages and in a large non-invasive adenoma. There was no correlation between 17q LOH and patient age, sex, standard clinicopathological variables (differentiation and nature of tumour margin), DNA ploidy, or tumour site, nor was 17q LOH associated with 17p LOH defined at four loci adjacent to p53. However, comparison of Dukes' B and C carcinomas revealed that tumours which had metastasized to regional lymph nodes at the time of primary surgery were significantly more likely to have lost this 17q allele. Clinical follow-up of this cohort of patients showed no significant difference in survival between patients whose tumours had lost or retained 17q. Thus, we conclude that 17q allele loss is associated with lymph node metastasis in locally aggressive colorectal tumours but probably not with blood-borne metastasis.

Adenoma↗

PubMed1995

Human papillomavirus type 18 is associated with less apoptosis in fibroblast tumours than human papillomavirus type 16.

In human cervical neoplasia human papillomavirus (HPV) type 18 has a higher cancer/cervical intraepithelial neoplasia (CIN) prevalence ratio than HPV 16. Fibrosarcomas derived from rat fibroblasts transfected with HPV 16 or 18 genomes showed increased apoptosis compared with controls. However, HPV 18 was associated with significantly less apoptosis than HPV 16, affording one possible explanation for the more rapidly progressive cervical neoplasia associated with HPV 18.

Animals↗

PubMed1995

Mutation of the p53 gene precedes aneuploid clonal divergence in colorectal carcinoma.

To establish whether p53 mutation precedes or follows clonal divergence in human colorectal carcinomas, 17 tumours were analysed at multiple sites (2-5 each) for single-strand conformation polymorphisms (SSCP) within exons 5-8 of the p53 gene. A previous study had demonstrated subclones of differing DNA ploidy in these tumours, but all showed immunocytochemical evidence for p53 stabilisation, using the monoclonal antibody PAb 1801. Mutations within exons 5-8 of p53 were identified by the presence of an abnormally migrating band in 10 of the 17 carcinomas: five in exon 5, four in exon 7 and one in exon 8. In each of these positive cases, samples from different parts of the carcinoma showed identical gel migration patterns in SSCP analysis. Similarly, the remaining seven tumours were concordant for absence of band shift across all samples of each tumour. Six SSCP-positive cases contained multiple populations differing in DNA ploidy, while four were homogeneously diploid or aneuploid throughout. Very similar proportions were observed in the SSCP-negative cases. In four positive tumours the mutation was confirmed by sequencing or through alteration of nucleotide-specific restriction enzyme cleavage. Identical mutations appeared in every sample from the same tumour. The results provide unequivocal evidence that the same mutant allele of p53 is present throughout each tumour bearing a mutation, regardless of the clonal variation identified by analysis of DNA ploidy. We conclude that in colorectal tumorigenesis mutation of p53 occurs as a single event which precedes and may facilitate the aneuploid clonal divergence of carcinomas.

Alleles↗

PubMed1994

Loss of heterozygosity in cervical carcinoma: subchromosomal localization of a putative tumor-suppressor gene to chromosome 11q22-q24.

Infection of cervical epithelial cells with so-called "aggressive" subtypes of human papilloma virus (HPV) appears to be an important factor in the etiology of cervical carcinoma. However, mounting evidence suggests that additional genetic changes are required for progression to an invasive carcinoma. Functional studies have shown that human chromosome 11 contains a gene or genes capable of suppressing tumorigenicity in cell lines derived from different histopathological types of cervical carcinoma, suggesting that aberration of this gene(s) may represent at least one of the additional changes required for tumorigenic progression. To identify the likely chromosomal position of this gene(s), we have carried out a systematic genetic analysis of chromosome 11 in the primary tumors of 32 patients with cervical carcinoma. Sixteen highly polymorphic markers, 10 of which were based on simple sequence repeats typed by PCR, were used to compare matched DNA samples from noninvolved tissue and portions of tumor tissue highly enriched for neoplastic cells by the cryostat-sectioning technique. Of the 32 patients examined, 14 (44%) demonstrated clonal genetic alterations resulting in loss of heterozygosity for one or more markers. Seven of the clonal genetic alterations on chromosome 11 were specific to the long arm, and the overlap between these and other allelic deletions suggests that a suppressor gene(s) relevant to cervical carcinoma maps to chromosome 11q22-q24.

Alleles↗

PubMed1994

p53 mutations in cervical carcinogenesis--low frequency and lack of correlation with human papillomavirus status.

p53 gene aberrations are common in human malignancies, and recent studies suggest that in cervical carcinoma p53 function is inactivated either by complex formation with human papillomavirus (HPV) E6 product or by gene mutation. Using polymerase chain reaction (PCR) followed by denaturing gradient gel electrophoresis (DGGE), we examined the mutational status of the four 'hotspot' regions of the p53 gene in 47 primary cervical carcinomas. HPV status was determined, also by PCR. In 20 of these cases, we examined for loss of heterozygosity (LOH) on chromosome 17p13. In the 47 carcinomas, and in a further 68 biopsy specimens from normal, premalignant and malignant cervix, we investigated aberrant immunocytochemical expression of p53. Immunocytochemically, abnormal p53 expression was detected in 13 of 115 cases (8/57 carcinomas). Somatic mutation in p53 was detected in 1 of 47 cervical carcinomas; 36 were positive for HPV 16, 18 or 33. A low level of allele loss (3 out of 20 cases) was detected on chromosome 17p, occurring in both HPV-positive and HPV-negative cases, and in cases with and without p53 mutations. We conclude that somatic mutation in the hotspot regions of the p53 gene occurs infrequently in cervical carcinomas; that immunocytochemically detectable levels of p53 are also infrequent; and that there is no consistent correlation between p53 mutational status, LOH on chromosome 17p or HPV status in these cancers.

Adenocarcinoma↗

PubMed1994

Deletion analysis of chromosome 8p in sporadic colorectal adenomas.

In order to assess the stage of colorectal tumorigenesis at which chromosome 8p loss of heterozygosity (LOH) occurs, 56 sporadic adenomas were examined for LOH at four polymorphic loci which show frequent LOH in carcinomas. LOH was found in only 5 out of 51 (9.8%) informative adenomas, whereas studies with the same markers in 85 informative carcinomas showed a LOH of 45%. The adenomas showing LOH were all in the 'high-risk' clinicopathological category, being 10 mm or more in diameter and showing tubulovillous architecture. It is concluded that the chromosome 8p locus is involved preferentially in the development of carcinomas rather than adenomas.

Adenoma↗

PubMed1994

Accumulation of p53 is associated with tumour progression in cutaneous lesions of renal allograft recipients.

Renal allograft recipients suffer from a markedly increased susceptibility to premalignant and malignant cutaneous lesions. Although various aetiological factors have been implicated, little is known of the associated genetic events. In this study we initially employed immunocytochemical techniques to investigate the prevalence and localisation of accumulated p53 in over 200 cutaneous biopsies (including 56 squamous cell carcinomas) from renal allograft recipients and immunocompetent controls. In renal allograft recipients accumulated p53 was present in 24% of uninvolved skin samples, 14% of viral warts, 41% of premalignant keratoses, 65% of intraepidermal carcinomas and 56% of squamous cell carcinomas [squamous cell carcinoma and intraepidermal carcinoma differed significantly from uninvolved skin (P < 0.005) and viral warts (P < 0.01)]. A similar trend was revealed in immunocompetent patients (an older, chronically sun-exposed population) but with lower prevalence of p53 immunoreactivity: 25% of uninvolved skin samples, 0% of viral warts, 25% of keratoses, 53% of intraepidermal carcinomas and 53% of squamous cell carcinomas. These differences were not statistically significant. Morphologically, p53 immunoreactivity strongly associated with areas of epidermal dysplasia and the abundance of staining correlated positively with the severity of dysplasia. These data suggest that p53 plays a role in skin carcinogenesis and is associated with progression towards the invasive state. No correlation was observed between accumulated p53 and the presence of human papillomavirus (HPV) DNA in any of the lesions. Single-strand conformational polymorphism analysis (exons 5-8) was used to determine the frequency of mutated p53 in 28 malignancies with varying degrees of immunopositivity. p53 mutations were found in 5/9 (56%) malignancies with p53 staining in > 50% of cells, reducing to 1/6 (17%) where 10-50% of cells were positively stained and none where < 10% of cells were stained. These data imply that factors other than p53 gene mutation play a part in accumulation of p53 in skin cancers.

Adolescent↗

PubMed1994

Prevalence of human papillomavirus DNA in cutaneous neoplasms from renal allograft recipients supports a possible viral role in tumour promotion.

It is well established that renal allograft recipients (RARs) have an increased incidence of viral warts and premalignant and malignant cutaneous lesions, and the risk of their development increases in proportion to duration of graft survival. It has been postulated that, in addition to the effects of prolonged immunosuppression and previous sun exposure, human papillomaviruses (HPV) may also contribute to the carcinogenic process. In this study, the prevalence of HPV DNA was examined in a range of premalignant and malignant cutaneous tumours from 50 immunosuppressed patients (47 renal allograft recipients plus three cardiac allograft recipients) and 56 immunocompetent patients using Southern hybridisation as a low-stringency screening method and type-specific polymerase chain reaction (PCR) assays for eight HPV types. The combined results for renal allograft recipients show that HPV DNA was detectable in 79% of viral warts, 42% of premalignant keratoses, 33% of intraepidermal carcinomas, 43% of invasive squamous cell carcinomas and 16% of uninvolved skin specimens (squamous cell carcinomas/renal allograft recipients significantly different at P < 0.05 from uninvolved skin specimens/renal allograft recipients). In immunocompetent patients the pattern of HPV DNA prevalence was 100% for viral warts; 25% for keratoses, 23% for intraepidermal carcinomas, 22% for squamous cell carcinomas and 8% for uninvolved skin. No single HPV type predominated in tumour specimens from either group. More tumours were found to contain HPV DNA by Southern hybridisation analysis than PCR, indicating the presence of HPV types other than HPV 1, 2, 5, 6, 8, 11, 16 and 18 in some tumours. However, 'low cancer risk' HPV types 1, 2 and 6 as well as 'high cancer risk' HPV types 5 and 16 were specifically detected by PCR in a small number of neoplasms. These data suggest that multiple HPV types may contribute to cutaneous neoplasia in RARs and that they appear to act early in the process of carcinogenesis, perhaps by functioning as tumour promoters via stimulation of cell proliferation.

Adult↗

PubMed1994

Loss of heterozygosity of MCC is not associated with mutation of the retained allele in sporadic colorectal cancer.

The adenomatous polyposis coli (APC) gene, which transmits familial adenomatous polyposis, is frequently mutated in sporadic colorectal tumours. Acquired somatic mutations have also been reported in a second gene, mutated in colorectal cancer (MCC), which lies within 500 kb of APC on chromosome 5q21 and has thus been implicated in tumour development. Further evidence for an oncosuppressor gene other than APC on chromosome 5q comes from recent studies of lung, renal and hepatic cancers in which there is loss of heterozygosity of 5q21 but no somatic APC mutations. To investigate the relative importance of APC and MCC in sporadic colorectal cancer, we have assessed the extent of 5q21 allelic loss in 80 carcinomas. All informative tumours exhibiting allelic loss had deletions which included both APC and MCC. In 21 tumours with loss of heterozygosity in MCC we have screened the entire coding region of the gene for mutation of the retained allele and found no evidence for mutation. The data indicate that independent loss of MCC is a rare event, and that in cases where allele loss occurs mutation of the retained allele is uncommon. This suggests that MCC does not function as an independent tumour suppressor in the majority of colorectal cancers.

Alleles↗

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↗