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The novel tumour suppressor gene ING1 is overexpressed in human melanoma cell lines
E I Campos1, K-J J Cheung, A Murray
1Department of Medicine, Division of Dermatology, Vancouver Hospital and Health Sciences Centre, University of British Columbia, Vancouver, BC, Canada.
Background:
Epidemiological evidence indicates that exposure to ultraviolet (UV) radiation is directly linked to the increase of both incidence and mortality of melanoma. However, the genetic changes caused by UV radiation that lead to melanoma formation remain poorly understood. Recently, a potential tumour suppressor gene ING1 (inhibitor of growth 1) was shown to inhibit cell growth and induce apoptosis in the presence of p53. We have demonstrated that the expression of ING1 is induced after UV irradiation and that ING1 enhances the repair of UV-damaged DNA.
Objectives:
To investigate if ING1 plays a role in melanoma formation.
Methods:
We examined p33ING1 expression levels in 14 melanoma cell lines.
Results:
We found that p33ING1 is overexpressed at both mRNA and protein levels in melanoma cell lines compared with normal melanocytes. Single-strand conformation polymorphism (SSCP) analysis showed band shifting in two melanoma cell lines. DNA sequencing confirmed that there were nucleotide alterations in the ING1 gene in Sk-mel-24 and Sk-mel-110 cell lines. Two silent nucleotide alterations in exon 1a were detected in Sk-mel-110. In Sk-mel-24, the A-->G nucleotide alteration at codon 260 resulted in an amino acid change from Asn to Ser, while seven other nucleotide alterations were silent. To determine if the silent nucleotide alterations in these two melanoma cell lines were due to polymorphism, SSCP analysis of ING1 gene was performed in 25 healthy volunteers. No band shift was observed in the SSCP analysis, suggesting that the nucleotide alterations in the melanoma cell lines are unlikely to be due to polymorphism.
Conclusions:
Taken together, our data demonstrate that ING1 is overexpressed, but infrequently mutated, in melanoma cell lines.
Insights
The inhibitor of growth 1 (ING1) gene is overexpressed in melanoma cell lines, suggesting a role in melanoma development. Mutations in ING1 are rare, indicating overexpression is the primary mechanism in these cell lines.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Ultraviolet (UV) radiation is a known risk factor for melanoma, but the underlying genetic mechanisms are unclear.
- The tumor suppressor gene inhibitor of growth 1 (ING1) inhibits cell growth and promotes apoptosis.
- ING1 expression increases after UV irradiation and aids in DNA repair.
Purpose of the Study:
- To investigate the role of ING1 in melanoma formation.
- To analyze ING1 expression and mutation status in melanoma cell lines.
Main Methods:
- Examined p33ING1 mRNA and protein expression in 14 melanoma cell lines.
- Utilized single-strand conformation polymorphism (SSCP) and DNA sequencing to detect alterations in the ING1 gene.
- Assessed ING1 gene polymorphism in healthy volunteers.
Main Results:
- p33ING1 was overexpressed in melanoma cell lines compared to normal melanocytes.
- Nucleotide alterations in the ING1 gene were identified in two melanoma cell lines (Sk-mel-24 and Sk-mel-110).
- One alteration in Sk-mel-24 caused an amino acid change (Asn to Ser); other alterations were silent and unlikely due to polymorphism.
Conclusions:
- ING1 is overexpressed in melanoma cell lines.
- Mutations in ING1 occur infrequently in melanoma cell lines.
- Overexpression, rather than mutation, appears to be the significant alteration of ING1 in melanoma.