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S. L. Lake, J. Dopierala, S. E. Coupland, B. E. Damato; Genetic Analysis of Conjunctival Melanoma by Multiplex Ligation-Dependent Probe Amplification (MLPA). Invest. Ophthalmol. Vis. Sci. 2009;50(13):5749.
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Conjunctival melanomas have a 10-year mortality rate of approximately 30%. Little is known about the molecular genetic changes occurring in these tumours. We aimed to identify the most common genetic aberrations occurring in conjunctival melanomas and to discuss how these compared with uveal and cutaneous melanomas.
DNA was extracted from 11 formalin-fixed, paraffin-embedded (FFPE) conjunctival melanomas using a modified Qiagen DNeasy Blood and Tissue kit (Qiagen, Crawley, UK). The MLPA P036D2 (Telomere) kit (MRC Holland, Amsterdam, The Netherlands) was applied to all samples. This uses sub-telomeric probes to asses copy number changes in all chromosome arms. The MLPA P027 (Uveal Melanoma) kit was applied to 8/11 samples. DNA from 5 histologically-normal FFPE tonsil tissues were used as controls in each experiment.
Amplification of 7p, 12p and 6p occurred in 7/11 (64%), 7/11(64%) and 5/11 (45%) conjunctival melanomas respectively. The only chromosome arm commonly to show loss was 4q, this abnormality occurring in 4/11 (36%) of tumours. Partial amplification of the MYC gene locus at 8q24.12 and of DDEF1 at 8q24.2 were observed in 6/8 (75%) and 7/8 (88%) tumours respectively.
The most common chromosomal abnormalities in conjunctival melanoma were gains of chromosome arms 6p, 7p and 12p, loss of 4q and gain of the MYC and DDEF1 loci on 8q. With the exception of chromosome 6p and 8q gains these abnormalities are different from those known to occur in uveal and cutaneous melanomas. Our results suggest conjunctival melanomas are genetically distinct from both uveal and cutaneous melanomas. Amplification of the MYC and DDEF1 gene regions on 8q are associated with metastatic disease in cutaneous and uveal melanomas respectively. Further investigation of the amplification of these important loci is therefore warranted in conjunctival melanomas.
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