Abstract

AIMS Overexpression ofc-myc protein has independent prognostic significance in a variety of primary and metastatic cutaneous melanomas which suggests a possible role for this gene in melanomagenesis. We have therefore examined the importance of this oncogene in uveal melanoma and studied the coexpression of two other gene products,Bcl-2 and p53, which might contribute to its effect.

METHODS The percentage of cells positive for nuclear c-mycexpression was estimated by flow cytometric analysis of nuclei extracted from paraffin blocks. The expression ofBcl-2 and p53protein was assessed by immunohistochemistry. A total of 71 tumours were studied and the results compared with survival with a mean follow up period of 6 years.

RESULTS c-mycwas expressed in >50% of the cells by 70% of the tumours, and was independently associated with improved survival in a Cox multiple regression model. Although Bcl-2 was expressed by the majority of the cells in 67% tumours, it was without effect on prognosis. None of the cases studied showed convincing positivity for p53. Analysis of coexpression showed that the best survival was seen inc-myc+/Bcl-2+ tumours and the worst inc-myc−/Bcl-2−tumours.

CONCLUSION The finding of improved rather than reduced survival inc-myc positive tumours is at variance with skin melanoma. There was no evidence to suggest thatc-myc was modulated by upregulation ofBcl-2 or p53inactivation/mutation. Although Bcl-2 is unlikely to have any effect on tumour growth or metastasis, it could contribute to the general lack of susceptibility to apoptosis in these tumours.