Absence of mutations in the pleckstrin homology (PH) domain of protein kinase B (PKB/Akt) in malignant melanoma

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During recent years it has become evident that protein kinase B (PKB)/Akt plays an important role in oncogenic transformation. The gene for PKB/Akt has been found to be overexpressed in certain human tumours and a viral fusion protein gains transforming capacity. Recruitment to the plasma membrane is mandatory for the physiological activation of PKB/Akt; this shift from cytoplasm to the membrane is achieved by the N-terminal pleckstrin homology (PH) domain. We attempted to find out whether mutations of this domain were present in human malignant melanoma. RNA from 18 primary melanoma lesions of different sizes and histological subtypes and two melanoma metastases from 20 Caucasian patients were used for reverse transcription and subsequent polymerase chain reaction (PCR) amplification of the PH domain of PKB/Akt α. Cycle sequencing of the purified PCR products showed that mutations of the PH domain of PKB/Akt were absent in all 20 melanoma specimens. In virtual Northern hybridizations PKB/Akt showed a low expression in both melanomas and acquired melanocytic naevi; however, no overexpression of PKB/Akt was detected. Thus in human melanoma PH domain mutations of PKB/Akt do not play a major role in melanoma carcinogenesis.

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