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The current situation with regard to human melanoma and genetic inferences
1Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Herston, Australia.
Abstract:
A melanoma predisposition gene has been identified. This gene, CDKN2, maps to chromosome 9p21-p22 and encodes p16, an inhibitor of cyclin-dependent kinases 4 and 6. CDKN2 has been found to be inactivated by homozygous deletion or intragenic mutation at high frequency in a diverse range of tumors and tumor cell lines, including those derived from melanomas. Now a number of CDKN2 mutations have been found in the germline of affected members of melanoma kindreds, and biochemical analysis of the mutant proteins has confirmed that they are functionally compromised. Unexpectedly, no germline CDKN2 mutations have been found in about half of the melanoma families that appear to be linked to 9p. Regulatory mutations outside of the coding region are being sought in these families. A number of other kindreds do not appear linked to 9p, hence the search continues for a second melanoma susceptibility gene.
Insights
A newly identified gene, CDKN2, is linked to melanoma predisposition. Mutations in this gene are found in some melanoma families, but others suggest a second susceptibility gene may exist.
Area of Science:
- Genetics
- Oncology
- Molecular Biology
Background:
- Melanoma is a significant skin cancer with a genetic component.
- The CDKN2 gene, encoding the p16 protein, is a known inhibitor of cell cycle progression.
- Previous studies indicated CDKN2's role in various cancers, including melanoma.
Purpose of the Study:
- To investigate the role of the CDKN2 gene in melanoma predisposition.
- To identify germline mutations in CDKN2 within melanoma-prone families.
- To explore potential genetic factors beyond CDKN2 in families not linked to chromosome 9p.
Main Methods:
- Gene mapping to chromosome 9p21-p22.
- Analysis of CDKN2 gene for homozygous deletions and intragenic mutations in tumors.
- Germline mutation screening in affected individuals from melanoma kindreds.
- Biochemical analysis of mutant p16 proteins.
Main Results:
- The CDKN2 gene, encoding p16, was identified and mapped to chromosome 9p21-p22.
- CDKN2 inactivation (deletion or mutation) is frequent in melanoma cell lines and tumors.
- Germline CDKN2 mutations were found in some melanoma families, confirming functional compromise.
- Approximately half of 9p-linked melanoma families lacked detectable germline CDKN2 mutations.
Conclusions:
- CDKN2 is a major melanoma predisposition gene, with germline mutations explaining susceptibility in some families.
- The absence of CDKN2 mutations in certain families suggests the involvement of other genetic factors, potentially including regulatory mutations or a second susceptibility gene.
- Further research is needed to identify additional melanoma susceptibility genes.