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Richard F Kefford

Publications and source records attributed to Richard F Kefford.

16 recordsLinked to original sources
PubMed2006

High-risk melanoma susceptibility genes and pancreatic cancer, neural system tumors, and uveal melanoma across GenoMEL.

GenoMEL, comprising major familial melanoma research groups from North America, Europe, Asia, and Australia has created the largest familial melanoma sample yet available to characterize mutations in the high-risk melanoma susceptibility genes CDKN2A/alternate reading frames (ARF), which encodes p16 and p14ARF, and CDK4 and to evaluate their relationship with pancreatic cancer (PC), neural system tumors (NST), and uveal melanoma (UM). This study included 466 families (2,137 patients) with at least three melanoma patients from 17 GenoMEL centers. Overall, 41% (n = 190) of families had mutations; most involved p16 (n = 178). Mutations in CDK4 (n = 5) and ARF (n = 7) occurred at similar frequencies (2-3%). There were striking differences in mutations across geographic locales. The proportion of families with the most frequent founder mutation(s) of each locale differed significantly across the seven regions (P = 0.0009). Single founder CDKN2A mutations were predominant in Sweden (p.R112_L113insR, 92% of family's mutations) and the Netherlands (c.225_243del19, 90% of family's mutations). France, Spain, and Italy had the same most frequent mutation (p.G101W). Similarly, Australia and United Kingdom had the same most common mutations (p.M53I, c.IVS2-105A>G, p.R24P, and p.L32P). As reported previously, there was a strong association between PC and CDKN2A mutations (P < 0.0001). This relationship differed by mutation. In contrast, there was little evidence for an association between CDKN2A mutations and NST (P = 0.52) or UM (P = 0.25). There was a marginally significant association between NST and ARF (P = 0.05). However, this particular evaluation had low power and requires confirmation. This GenoMEL study provides the most extensive characterization of mutations in high-risk melanoma susceptibility genes in families with three or more melanoma patients yet available.

Adult↗
PubMed2006

Physical and functional interaction of the p14ARF tumor suppressor with ribosomes.

Alterations in the p14(ARF) tumor suppressor are frequent in many human cancers and are associated with susceptibility to melanoma, pancreatic cancer, and nervous system tumors. In addition to its p53-regulatory functions, p14(ARF) has been shown to influence ribosome biogenesis and to regulate the endoribonuclease B23, but there remains considerable controversy about its nucleolar role. We sought to clarify the activities of p14(ARF) by studying its interaction with ribosomes. We show that p14(ARF) and B23 interact within the nucleolar 60 S preribosomal particle and that this interaction does not require rRNA. In contrast to previous reports, we found that expression of p14(ARF) does not significantly alter ribosome biogenesis but inhibits polysome formation and protein translation in vivo. These results suggest a ribosome-dependent p14(ARF) pathway that regulates cell growth and thus complements p53-dependent p14(ARF) functions.

Cell Cycle↗
PubMed2006

Features associated with germline CDKN2A mutations: a GenoMEL study of melanoma-prone families from three continents.

BACKGROUND: The major factors individually reported to be associated with an increased frequency of CDKN2A mutations are increased number of patients with melanoma in a family, early age at melanoma diagnosis, and family members with multiple primary melanomas (MPM) or pancreatic cancer. METHODS: These four features were examined in 385 families with > or =3 patients with melanoma pooled by 17 GenoMEL groups, and these attributes were compared across continents. RESULTS: Overall, 39% of families had CDKN2A mutations ranging from 20% (32/162) in Australia to 45% (29/65) in North America to 57% (89/157) in Europe. All four features in each group, except pancreatic cancer in Australia (p = 0.38), individually showed significant associations with CDKN2A mutations, but the effects varied widely across continents. Multivariate examination also showed different predictors of mutation risk across continents. In Australian families, > or =2 patients with MPM, median age at melanoma diagnosis < or =40 years and > or =6 patients with melanoma in a family jointly predicted the mutation risk. In European families, all four factors concurrently predicted the risk, but with less stringent criteria than in Australia. In North American families, only > or =1 patient with MPM and age at diagnosis < or =40 years simultaneously predicted the mutation risk. CONCLUSIONS: The variation in CDKN2A mutations for the four features across continents is consistent with the lower melanoma incidence rates in Europe and higher rates of sporadic melanoma in Australia. The lack of a pancreatic cancer-CDKN2A mutation relationship in Australia probably reflects the divergent spectrum of mutations in families from Australia versus those from North America and Europe. GenoMEL is exploring candidate host, genetic and/or environmental risk factors to better understand the variation observed.

Australia↗
PubMed2006

The ARF tumour suppressor.

The ARF tumour suppressor is a product of the INK4a/ARF locus; a sequence that is frequently altered in human cancer. ARF is upregulated by oncogenic stimuli and is a critical regulator of p53 stability through interactions with the mdm2 and ARF-BP1/Mule ubiquitin ligases. Cellular stress signals liberate ARF from the nucleolus where it is bound to B23/nucleophosmin. This nucleolar location of ARF may serve as a reservoir for the rapid induction of p53, but may also serve to co-ordinate effects on cell cycle, survival and growth. The biological functions of ARF interactions with other binding partners remain uncertain, but ARF-mediated sumoylation may represent a unifying effector pathway.

Amino Acid Sequence↗
PubMed2005

The melanoma-associated 24 base pair duplication in p16INK4a is functionally impaired.

Melanoma-associated germline mutations affecting the tumor suppressor and cyclin-dependent kinase (CDK) inhibitor, CDKN2A/p16INK4a, have been identified in over 100 melanoma-prone families worldwide. To predict the melanoma risk for carriers of specific mutations, mutant p16INK4a can be tested in biochemical and cellular assays. In most cases, p16INK4a mutations with predicted disease relation, due to segregation with melanoma, are functionally impaired in such assays. The N-terminal 24 base pair duplication of CDKN2A, however, encodes a p16INK4a variant previously shown to have wild-type function, despite segregating with melanoma in at least 5 melanoma families. To clarify whether the duplication mutation has a cell cycle regulatory defect or behaves like wild-type p16INK4a, we reanalyzed the cell cycle-inhibitory activity of this mutation. Stable cell clones of the p16-null WMM1175 melanoma cell line inducible for ectopic p16INK4a were used in this study. In these cells, p16INK4a expression can be controlled at physiologic levels. Our results show that in comparison to wild-type p16INK4a, the duplication mutant induced weaker S-phase inhibition and cells expressing this mutant form of p16INK4a retained colony formation ability. We also show that the cell cycle-regulatory defect of the p16INK4a duplication mutant was associated with decreased inhibition of pRb phosphorylation even though it retained significant binding to CDK4.

Base Pairing↗
PubMed2005

p14ARF interacts with the SUMO-conjugating enzyme Ubc9 and promotes the sumoylation of its binding partners.

The p14ARF tumour suppressor regulates a series of cell cycle regulatory proteins to promote cell cycle arrest in response to abnormal hyperproliferative growth stimuli. p14ARF alterations are common in human cancers and, when inherited, confer susceptibility to cutaneous melanoma. We now propose that the mechanism of p14ARF action may involve the covalent modification of its binding partners with the small ubiquitin-related protein SUMO-1. In particular, we demonstrate that p14ARF interacts with the SUMO E2 conjugating enzyme, Ubc9 and enhances the sumoylation of its binding partners, hdm2, E2F-1, HIF-1alpha, TBP-1 and p120E4F. Furthermore, p14ARF-induced sumoylation is abrogated by a subset of melanoma-associated p14ARF mutations. These results provide a mechanism for p14ARF action through a common modification of diverse binding partners.

Adenovirus E4 Proteins↗
PubMed2005

Enforced expression of p14ARF induces p53-dependent cell cycle arrest but not apoptosis.

Expression of the p14ARF tumour suppressor is induced by hyperproliferative signals produced by RAS, MYC and other oncogenes. p14ARF quenches inappropriate mitogenic signaling by activating the p53 pathway, and the frequent loss of p14ARF in human cancer diminishes the duration and level of the p53 response. Consistent with this role, p14ARF accumulation can induce potent cell cycle arrest, but its role in promoting apoptosis has not been well established. Therefore we investigated the effects of p14ARF on the survival and growth of several human cell types. To avoid the toxicity associated with adenoviral-based vectors, we established inducible expression of p14ARF in p53-intact and p53-deficient human cell lines. As expected, transient and inducible expression of p14ARF induced rapid cell cycle arrest only in tumour cells expressing intact p53. Further, p14ARF expression did not promote apoptosis in primary human fibroblasts, or in any human tumour cell line tested, irrespective of p53 status. Instead, p14ARF expression sensitized cells to apoptosis in the presence of inhibitors of topoisomerase II (adriamycin) and transcription (DRB). Thus, loss of p14ARF would be an important step in the selection of apoptotic resistant tumour cells.

Adenoviridae↗
PubMed2004

Deletion mapping suggests that the 1p22 melanoma susceptibility gene is a tumor suppressor localized to a 9-Mb interval.

Loss of the short arm of chromosome 1 is frequently observed in many tumor types, including melanoma. We recently localized a third melanoma susceptibility locus to chromosome band 1p22. Critical recombinants in linked families localized the gene to a 15-Mb region between D1S430 and D1S2664. To map the locus more finely we have performed studies to assess allelic loss across the region in a panel of melanomas from 1p22-linked families, sporadic melanomas, and melanoma cell lines. Eighty percent of familial melanomas exhibited loss of heterozygosity (LOH) within the region, with a smallest region of overlapping deletions (SRO) of 9 Mb between D1S207 and D1S435. This high frequency of LOH makes it very likely that the susceptibility locus is a tumor suppressor. In sporadic tumors, four SROs were defined. SRO1 and SRO2 map within the critical recombinant and familial tumor region, indicating that one or the other is likely to harbor the susceptibility gene. However, SRO3 may also be significant because it overlaps with the markers with the highest 2-point LOD score (D1S2776), part of the linkage recombinant region, and the critical region defined in mesothelioma. The candidate genes PRKCL2 and GTF2B, within SRO2, and TGFBR3, CDC7, and EVI5, in a broad region encompassing SRO3, were screened in 1p22-linked melanoma kindreds, but no coding mutations were detected. Allelic loss in melanoma cell lines was significantly less frequent than in fresh tumors, indicating that this gene may not be involved late in progression, such as in overriding cellular senescence, necessary for the propagation of melanoma cells in culture.

Base Sequence↗
PubMed2003

Frequent loss of heterozygosity targeting the inactive X chromosome in melanoma.

After previous preliminary observations of paradoxical deletion events affecting the inactive X chromosome in melanoma, we have surveyed the X chromosome for deletions using 23 polymorphic microsatellite markers in 28 informative (female XX) metastatic melanomas. Ten tumors (36%) showed at least one loss of heterozygosity (LOH) event, and in two cases an entire chromosome showed LOH at all informative loci. Four distinct X chromosome smallest regions of overlap can be resolved. An 18.6-Mb region on the p arm involving 9 of 28 (32%) samples lies between the markers DXS1061 and DXS1068. An equally frequently deleted smallest region of overlap straddled the centromere, bounded by DX1204 on the p arm and DXS983 14.6 Mb away in Xq11-12. One tumor potentially defines this region more tightly to a 10.6-Mb smallest region of overlap bounded by DXS1190 and DXS981 that contains the androgen receptor (AR) gene. A 6.2-Mb deleted region can be defined between the markers DXS8051 and DXS9902 in 8 of 28 (28%) tumors. An additional, less frequently deleted region of 25.7 Mb was found on distal Xq between the markers DXS1212 and DXS1193 in 5 of 28 (18%) tumors. X inactivation analysis of five tumors with LOH, using the AR exon 1 CAG repeat, showed that in each case, the inactive, hypermethylated allele was the one deleted. Analysis of copy number in this region by quantitative PCR showed restoration to disomy and, in one case, trisomy at AR.

Adult↗
PubMed2003

Localization of a novel melanoma susceptibility locus to 1p22.

Over the past 20 years, the incidence of cutaneous malignant melanoma (CMM) has increased dramatically worldwide. A positive family history of the disease is among the most established risk factors for CMM; it is estimated that 10% of CMM cases result from an inherited predisposition. Although mutations in two genes, CDKN2A and CDK4, have been shown to confer an increased risk of CMM, they account for only 20%-25% of families with multiple cases of CMM. Therefore, to localize additional loci involved in melanoma susceptibility, we have performed a genomewide scan for linkage in 49 Australian pedigrees containing at least three CMM cases, in which CDKN2A and CDK4 involvement has been excluded. The highest two-point parametric LOD score (1.82; recombination fraction [theta] 0.2) was obtained at D1S2726, which maps to the short arm of chromosome 1 (1p22). A parametric LOD score of 4.65 (theta=0) and a nonparametric LOD score of 4.19 were found at D1S2779 in nine families selected for early age at onset. Additional typing yielded seven adjacent markers with LOD scores >3 in this subset, with the highest parametric LOD score, 4.95 (theta=0) (nonparametric LOD score 5.37), at D1S2776. Analysis of 33 additional multiplex families with CMM from several continents provided further evidence for linkage to the 1p22 region, again strongest in families with the earliest mean age at diagnosis. A nonparametric ordered sequential analysis was used, based on the average age at diagnosis in each family. The highest LOD score, 6.43, was obtained at D1S2779 and occurred when the 15 families with the earliest ages at onset were included. These data provide significant evidence of a novel susceptibility gene for CMM located within chromosome band 1p22.

Adolescent↗
PubMed2003

Is there a role for genetic testing in patients with melanoma?

Autosomal dominant inheritance of mutations in the locus or the gene may confer a high risk of cutaneous melanoma development. The penetrance of mutations is influenced by UV exposure. Inherited variants in the melanocortin-1 receptor also confer increased risk of cutaneous melanoma. Features associated with increased genetic susceptibility to cutaneous melanoma include the presence of multiple affected first-degree relatives on one side of the family, multiple primary melanomas in the same individual, earlier age of onset, and the presence of multiple atypical nevi, but none of these factors reliably predicts for the presence of mutations. It is currently premature to offer predictive DNA testing for melanoma outside of defined research protocols. This is because of (1). the low likelihood of finding mutations in known melanoma susceptibility genes, even in more than 60% of melanoma-prone kindreds; (2). the broad confidence limits on current estimates of lifetime penetrance of mutations and the wide variation in this penetrance with locality; (3). a high "background" incidence of melanoma in non-mutation carriers in melanoma-prone families; (4). current uncertainties about the factors determining the functionality and phenotypic expression of the trait among carriers of these mutations (penetrance), even if found; and (5). the lack of proved efficacy of melanoma prevention and surveillance strategies, even for mutation carriers. Rather than singling out those deemed to be at high risk because of family history, all patients carrying risk factors for cutaneous melanoma should be subject to stringent programs of sun protection and skin surveillance.

ADP-Ribosylation Factors↗
PubMed2002

Association of p14ARF with the p120E4F transcriptional repressor enhances cell cycle inhibition.

The p14(ARF) tumor suppressor is a key regulator of cellular proliferation and is frequently inactivated in human cancer. This tumor suppressor functions in the p53 and pRb cell cycle regulatory pathways and can effectively activate both pathways to induce growth arrest or cell death. We now report that p14(ARF) forms a complex with the E1A-regulated transcriptional repressor, p120(E4F). p120(E4F) contacts p14(ARF) and p53 to form a ternary complex in vivo and enhances p14(ARF)-induced G(2) cell cycle arrest in a p53-dependent manner. We suggest that the interaction of p14(ARF) and p120(E4F) forms an important link between the p14(ARF) and p53 tumor suppressor proteins, both of which exhibit enhanced cell cycle inhibitory activity in the presence of this transcriptional repressor.

Adenovirus E4 Proteins↗
PubMed2002

Targeting molecular mechanisms in cancer.

Malignant disease is characterized by the disregulated growth of transformed cells. In recent years, dramatic insight into the molecular mechanisms of this phenomenon have come from basic cancer research. Detailed knowledge of the molecular pathology of cancer allows therapeutic agents to be designed that specifically target aberrant cellular processes. There are currently a number of targeted treatment strategies being evaluated. In the future, it is likely that this mechanistic approach will have a significant impact on clinical oncology and the diagnostic evaluation of tumours.

Animals↗
PubMedDate not supplied

Cutaneous melanoma.

Episodic exposure of fair-skinned individuals to intense sunlight is thought to be responsible for the steadily increasing melanoma incidence worldwide over recent decades. Rarely, melanoma susceptibility is increased more than tenfold by heritable mutations in the cell cycle regulatory genes CDKN2A and CDK4. Effective treatment requires early diagnosis followed by surgical excision with adequately wide margins. Sentinel lymph node biopsy provides accurate staging, but no published results are yet available from clinical trials designed to assess the therapeutic efficacy of early complete regional node dissection in those with metastatic disease in a sentinel node. Magnetic resonance spectroscopy is one technique under investigation for non-invasive, in-situ assessment of sentinel nodes. Localised metastatic disease is best treated surgically. No postoperative adjuvant therapy is of proven value for improving overall survival, although numerous clinical trials of vaccines and cytokines are in progress. Medical therapies have contributed little to the control of established metastatic disease, but molecular pathways recently identified as being central to melanoma growth and apoptosis are under intense investigation for their potential as therapeutic targets.

Combined Modality Therapy↗