Melanoma inhibitor of apoptosis protein is expressed differentially in melanoma and melanocytic naevus, but similarly in primary and metastatic melanomas

Background: Malignant melanoma is highly resistant to current treatments. The inhibitor of apoptosis protein (IAP) family member, melanoma IAP (ML-IAP), is overexpressed in some melanoma cell lines, rendering them resistant to apoptotic signals. Targeting ML-IAP is a promising approach to treating melanoma. However, the status of ML-IAP expression in human melanoma tissues and the difference in expression between melanoma and melanocytic naevus are not known. Aims: To investigate these issues. Methods: ML-IAP expression in 48 archived patient samples ( 34 melanomas and 14 dermal naevi) was assessed by immunohistochemistry and by in situ hybridisation and reverse transcription polymerase chain reaction (RT-PCR) assays developed for the study. Results: Expression of ML-IAP was detected in 47.6 - 70.6% ( 10 of 21 to 24 of 34) of the melanomas, varying with detection methods. The expression rate in melanoma was much higher than that in melanocytic naevus (10.0 - 21.4%; one of 10 to three of 14). No significant difference was seen between primary and secondary melanomas. ML- IAP expression rates assessed by the three methods were in agreement. Conclusions: The ML- IAP expression rate in archived melanoma tissues is around 50 - 70%, with no difference between primary and secondary melanomas. A small number of dermal naevi (similar to 20%) also expressed ML- IAP.