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Murine melanomas accelerated by a single UVR exposure carry photoproduct footprints but lack UV signature C>T mutations in critical genes

Citation

Mukhopadhyay, P and Ferguson, B and Muller, HK and Handoko, HY and Walker, GJ, Murine melanomas accelerated by a single UVR exposure carry photoproduct footprints but lack UV signature C>T mutations in critical genes, Oncogene ISSN 0950-9232 (2015) [Contribution to Refereed Journal]

DOI: doi:10.1038/onc.2015.386

Abstract

Ultraviolet radiation (UVR) exposure increases malignant melanoma (MM) risk, but in the context of acute, not cumulative exposure. C>T and CC>TT changes make up the overwhelming majority of single base substitutions (SBS) in MM DNA, as both precursor melanocytes and melanocytic lesions have incurred incidental exposures to sunlight. To study the mutagenic mechanisms by which acute sunburn accelerates MM, we sequenced the exomes of spontaneous and neonatal UVB-induced Cdk4-R24C::Tyr-NRASQ61K mouse MMs. UVR-induced MMs carried more SBSs than spontaneous MMs, but the levels of genomic instability, reflected by translocations and copy number changes, were not different. C>T/G>A was the most common SBS in spontaneous and UVR-induced MMs, only modestly increased in the latter. However, they tended to occur at the motif A/GpCpG (reflecting C>T transition due to spontaneous deamination of cytosine at CpG) in spontaneous MMs, and T/CpCpC/T (reflecting the effects of pyrimidine dimers on either side of the mutated C) in UVR-induced MMs. Unlike MMs associated with repetitive exposures, we observed no CC>TT changes. In addition, we also found UVR 'footprints' at T>A/A>Ts (at NpTpT) and T>C/A>G (at CpTpC). These footprints are also present in MMs from a chronic UVR mouse model, and in some human MMs, suggesting that they may be minor UVR signature changes. We found few significantly somatically mutated genes (~6 per spontaneous and 15 per UVR-induced melanoma) in addition to the Cdk4 and NRAS mutations already present. Trp53 was the most convincing recurrently mutated gene; however, in the UVR-induced MMs no Trp53 mutations were at C>T/G>A, suggesting that it was probably mutated during tumour progression, not directly induced by UVR photoproducts. The very low load of recurrent mutations convincingly induced by classical UVB-induced dimer photoproducts may support a role for cell extrinsic mechanisms, such as photoimmunosuppression and inflammation in driving MM after acute UVB exposure.Oncogene advance online publication,

Item Details

Item Type:Contribution to Refereed Journal
Research Division:Medical and Health Sciences
Research Group:Oncology and Carcinogenesis
Research Field:Cancer Genetics
Objective Division:Health
Objective Group:Clinical Health (Organs, Diseases and Abnormal Conditions)
Objective Field:Cancer and Related Disorders
Author:Muller, HK (Professor Konrad Muller)
ID Code:106089
Year Published:2015
Web of Science® Times Cited:5
Deposited By:Medicine (Discipline)
Deposited On:2016-01-28
Last Modified:2016-02-11
Downloads:0

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