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N K Hayward

Publications and source records attributed to N K Hayward.

At least 73 records · Page 4Linked to original sources
PubMed1994

p53 gene in hepatocellular carcinomas from Australia.

The p53 protein is now well established as a crucial player in regulation of cell growth. Mutations arising in the coding sequences of its gene have been demonstrated in a wide variety of human tumors, including hepatocellular carcinoma (HCC). Our previous studies have shown that codon 249 mutations, the most common mutation of the p53 gene in HCCs, did not occur in our group of patients. To examine the prevalence of p53 mutations in other areas of the p53 gene, PCR and direct sequencing were carried out on these samples covering the four highly conserved regions of the gene between exons 5 and 8. Liver samples were obtained from both HBV+ and HBV- patients in a variety of ethnic groups. Primers to the flanking regions of exon 5, 6, 7, and 8 were used in PCR to amplify these exons. Following purification, the products were sequenced in both directions by cycle sequencing. In 15 HCCs examined, no mutations in these exons of the p53 gene were found. This suggests a less important role for p53 in development of HCC in this group of patients than in patients from other areas of the world.

Australia↗
PubMed1994

Refined localization of the melanoma (MLM) gene on chromosome 9p by analysis of allelic deletions.

Various lines of evidence including linkage analysis, frequent homozygous and heterozygous deletions in melanoma DNAs, and the finding of a patient with multiple primary melanomas who harbours a 5p/9p translocation involving loss of several 9p markers, have indicated that the 9p22-p13 region harbours a gene important for the development of melanoma (MLM). We have used eight short tandem repeat polymorphism (STRP) markers mapping to this region to look for allelic losses in DNA from melanoma biopsies and cell lines. Heterozygous losses were found in 8/14 (57%) fresh melanoma biopsy DNAs with the smallest region of overlap (SRO) being between IFNA and D9S169. In addition, when DNA from 30 melanoma cell lines was studied, four cell lines (13%) were found to be homozygously deleted for various 9p markers. Two of these cell lines define the borders of overlapping homozygous deletions within a 4cM region of 9p21 between IFNA and D9S171. Moreover, a further 14 melanoma cell lines were hemizygous for the IFNA/D9S171/D9S126 region. These data support the hypothesis that the MLM gene acts as a tumour suppressor, and provide a refinement of its localization on 9p.

Alleles↗
PubMed1992

UV induction of transforming growth factor alpha in melanoma cell lines is a posttranslational event.

Low, mitogenic fluences of UVC (3.7-5.6 Jm-2) have previously been shown to cause increases of radioimmunoassayable transforming growth factor alpha (TGF alpha) in the medium and cells of cultures of melanocytes, melanoma lines, and HeLa cells (Ellem, K.A.O., Cullinan, M., Baumann, K.C., Dunstan, A.: Carcinogenesis 9:797-801, 1988). Here the cellular mechanism of this increase is explored by Northern blotting to detect any changes in TGF alpha mRNA levels, and the use of inhibitors of macromolecular synthesis to attempt to block the increase in TGF alpha protein. We were unable to detect any increase in TGF alpha mRNA levels attributable to UVC between 2 and 24 hours after irradiation. Inhibition of DNA synthesis (arabinosylcytosine, 10 microM), RNA synthesis (actinomycin D, 3 micrograms/ml; DRB 93 microM), or protein synthesis (cycloheximide, 10 micrograms/ml) failed to prevent the UVC induced increase in TGF alpha. We conclude that the UVC induction of TGF alpha is by a posttranslational mechanism. There was considerable discordance between the amount of TGF alpha protein and its mRNA in cultures of 15 different melanoma cell lines, which again emphasized that posttranscriptional mechanisms modulate the release of immunodetectable TGF alpha. We also found that the inhibitors themselves were capable of inducing an increase in TGF alpha in MM229 cultures. This suggests that the inhibitors and UV may effect the increase by a common mechanism, perhaps the activation of cell surface proteases as suggested for other stimuli (e.g., Pandiella, A., and Massagué, J.: Proc. Natl. Acad. Sci., USA 88:1726-1730, 1991) and that the response may be part of a global response to perturbation of DNA synthesis.

Cell Death↗
PubMed1992

Exclusion of the familial melanoma locus (MLM) from the PND/D1S47 and MYCL1 regions of chromosome arm 1p in 7 Australian pedigrees.

Familial melanoma (MLM) is sometimes found associated with the dysplastic nevus syndrome (DNS). Considerable controversy exists over the possible assignment of a cutaneous malignant melanoma/dysplastic nevus gene, designated CMM, to the distal short arm of chromosome 1, linked to the PND and D1S47 loci. To date, no support for linkage of MLM alone to these markers has been found; likewise no study has been able to exclude the entire region between PND and D1S47 from linkage to MLM. We have carried out linkage studies between markers on 1p and MLM in seven Australian kindreds; three of these are the largest reported worldwide. We have been able to exclude localization of an MLM gene from a 40-cM region that spans the interval between D1S47 and PND and extends approximately 15 cM on either side of these markers. In addition, we can exclude a region of about 20 cM around the MYCL1/D1S57 loci.

Atrial Natriuretic Factor↗
PubMed1992

Linkage mapping of melanoma (MLM) using 172 microsatellite markers.

The incidence of malignant melanoma is currently increasing faster than any other cancer and in 5-12% of cases occurs in a familial context in which the disease cosegregates as an autosomal dominant trait. To identify the location of genes that predipose individuals to familial melanoma (MLM), we have carried out linkage analysis in three large Australian melanoma pedigrees using 172 microsatellite markers spread across all autosomes. Three additional smaller families were typed for 70 of the same markers. In five of the six families we found lod scores between 1.0 and 2.3, which may provide evidence for the location of melanoma genes in proximity to some of these markers. If this turns out to be the case, these data potentially demonstrate that MLM is genetically heterogeneous since there was no marker for which all families gave significantly high LODs. These data provide the foundation for an exclusion map for melanoma and, more importantly, high-light areas of the genome for others to substantiate the potential positions of some of the genes that may be responsible for susceptibility to MLM.

Chromosome Mapping↗
PubMed1991

Loss of somatic heterozygosity in hepatocellular carcinoma.

Loss of tumor suppressor genes is involved in the mechanism of tumorigenesis of many solid tumors. We tested 9 hepatitis B virus (HBV)-positive and 10 HBV-negative hepatocellular carcinomas for loss of somatic heterozygosity using 14 polymorphic probes mapping to chromosomes 4, 11, 13, and 17. Losses were found on all chromosome arms tested. The highest frequency of loss was observed at the D13S1 locus (67%) at band 13q12. Losses were also observed at three other loci on 13q. Twenty-one % of informative cases showed loss on 17p using the probe pYNZ22 which maps near the p53 locus. Losses on 4q were infrequent with 17% found at one locus and no loss at two others. The retinoblastoma gene and the locus on 17p were only inactivated in our HBV-negative tumors, although the numbers were too small for statistical significance. For all loci tested, we found no significant differences in the frequency of losses with HBV status, ethnic background, cirrhosis, grade of tumor, or presence of hemochromatosis.

Adult↗
PubMed1991

Single base mutation in the hormone binding domain of the thyroid hormone receptor beta gene in generalised thyroid hormone resistance demonstrated by single stranded conformation polymorphism analysis.

Thyroid hormone resistance is a syndrome of considerable clinical heterogeneity. Three mutations in the c-erb A beta gene encoding the human beta thyroid hormone receptor have been described in different kindreds. We report here, in a family affected with peripheral thyroid hormone resistance, a unique point mutation in the ligand binding domain of the c-erb A beta gene resulting in histidine replacement of an arginine residue at position 438. The region in which the mutation occurred was identified by single stranded conformation polymorphism analysis and confirmed by subcloning and sequencing of the mutant alleles from each of the affected members. Binding of tri-iodothyronine to isolated nuclei from family members was normal suggesting the mechanism of thyroid hormone resistance in this family is not mediated by abnormal binding of ligand and receptor.

Adult↗
PubMed1991

Loss of allelic heterozygosity on distal chromosome 1p in Merkel cell carcinoma. A marker of neural crest origins?

The location of genes involved in tumor evolution has been inferred from experiments in which loss of constitutional heterozygosity has been detected in tumor DNA at high frequency in specific chromosome regions. For example, cytogenetic and molecular abnormalities on chromosome 1p have been reported in tumors such as malignant melanoma and neuroblastoma which arise in cells derived from embryonic neural crest tissue. To extend these observations, we have examined tumor DNA from three cases of Merkel cell carcinoma for evidence of loss of constitutional heterozygosity on the short arm of chromosome 1. In all three cases, heterozygous allelic deletions of varying extent on distal chromosome 1p were detected in tumor DNA. Comparisons with neural crest tumors suggest that loss of heterozygosity on distal chromosome 1p in Merkel cell tumors may be a marker of neural crest origin.

Alleles↗
PubMed1991

Analysis of gene amplification in head-and-neck squamous-cell carcinoma.

The presence of gene amplification was determined in 66 fresh head-and-neck SCC specimens using a battery of 9 different probes. Amplification of at least one gene was found in 12 samples (18%), of which 7 were amplified at multiple loci (58%). We observed amplifications for EGFR (10% of samples) and c-myc (9%), as well as co-amplification of bcl-1/int-2 (7%). No amplifications were demonstrated for c-Ha-ras-1, TGF alpha, c-mos, c-erbB-2, or c-erbA-2. The incidence of proto-oncogene amplification in head-and-neck SCC patients is comparable to that reported for other solid tumours. There was no statistically significant difference in survival between patients with or without gene amplification. However, the presence of multiple amplifications in several patients with advanced primary tumours suggests that the accumulation of genetic changes may correlate more closely with tumour size than with inherent biologic aggression.

Adult↗
PubMed1989

Spontaneous and 4-nitroquinoline 1-oxide-induced G2 chromosome aberrations in lymphoblasts from familial melanoma patients.

Lymphoblastoid cell lines established from three unrelated kindreds with familial melanoma (FM) were cytogenetically analyzed for spontaneous and 4-nitroquinoline-1-oxide (4NQO)-induced chromosome aberrations. There were no significant differences between control, FM, or xeroderma pigmentosum (XP) cell lines for spontaneous aberrations. As a group, FM patients, as well as XP patients, had significantly higher 4NQO-induced aberrations than controls when metaphase cells were analyzed 2.5 hours after treatment during the G2 phase of the cell cycle. When selected cell lines were analyzed 18 hours after 4NQO treatment, the frequency of chromosome aberrations in FM cells returned to spontaneous levels, but XP cells retained significantly elevated aberration frequencies. The wide variability for chromosome aberrations within the control. FM relative, and FM patient groups during G2, however, indicated that analysis of total breakage rates alone would not be predictive of susceptibility to FM. Heterogeneity for carcinogen-induced chromosome breakage between some cancer-prone individuals and the possible significance of site-specific chromosome aberrations are discussed.

4-Nitroquinoline-1-oxide↗
PubMed1989

Origin of rare Ha-ras alleles: relationship of VTR length to a 5' polymorphic Xho I site.

Amongst the four common Ha-ras alleles in both controls and cancer patients, we detected the presence of a polymorphic Xho I site associated specifically with the 6.6 and 7.7 kb Bam HI fragments but absent from the 7.1 and 8.2 kb alleles, as recently reported by others. We have extended this study and report here, the consistent appearance of this Xho I site in unusual alleles close in size to the two common alleles of 6.6 and 7.7 kb, in control lymphoblastoid DNA samples in a variety of tumor DNAs. Unusual alleles grouped around the 7.1 and 8.2 kb common alleles on the other hand, did not possess the Xho I site. The consistent presence of the Xho I site polymorphism, in the unusual Ha-ras alleles surrounding the 6.6 and 7.7 kb common alleles and its absence in alleles around the 7.1 and 8.2 kb common alleles, suggests that the unusual ones are derived from the corresponding common alleles to which they are closest in size.

Alleles↗
PubMed1988

c-Ha-ras-1 alleles in bladder cancer, Wilms' tumour and malignant melanoma.

Polymorphism of the human c-Ha-ras-1 gene has been analysed in DNA from 168 individuals using the enzymes MspI and HpaII. In all, 35 bladder cancer patients, 28 melanoma patients, 22 Wilms' tumour patients, 24 first-degree relatives of Wilms' tumour or melanoma patients and 59 unaffected controls were studied. A total of 13 different fragment sizes was detected, 4 "common" and 9 "unusual". Of the latter, 4 were observed only in cancer patients or their first-degree relatives. The frequency of unusual alleles was significantly greater in bladder cancer patients and in the combined tumour group than in controls, thus providing support for the association of unique Ha-ras alleles and cancer. Some unaffected relatives of patients carried unusual alleles, and thus there is no absolute relationship between Ha-ras genotype and disease.

Alleles↗