PI3K/Akt pathway mutations in retinoblastoma.

PURPOSE: Many malignancies are known to be associated with abnormal activation of the PI3K-AKT pathway. Recently, a somatic mutation in the AKT1 gene (E17K) was identified in a small proportion of human tumors. This mutation activated AKT1 by means of abnormal membrane recruitment and stimulated downstream signaling. This study was designed to analyze AKT1 mutations in retinoblastoma and gain insights into the role PI3K-AKT pathway plays in the development of this tumor.
METHODS: Twenty-four samples of retinoblastoma from children were analyzed for mutations in the AKT1, PTEN and K-RAS genes, using a chip-based matrix-assisted laser desorption-time-of-flight (MALDI-TOF) mass spectrometer. Mutations in the PIK3CA gene were analyzed in 16 retinoblastoma samples using direct sequencing.
RESULTS: These results show that the mutation E17K/AKT1 was not detected in the 24 samples of retinoblastoma analyzed. K-RAS mutations were identified in two samples. There were no mutations in any of the other genes analyzed by a mass array system. On direct sequencing of 16 samples for the PIK3CA gene, one sample showed gain of function mutation in exon 9. In another sample, a genetic polymorphism of unknown significance (rs17849079) was detected in exon 20.
CONCLUSIONS: Although the PI3K-AKT pathway is known to be dysregulated in retinoblastoma, the low frequency of oncogenic mutations in the AKT1, PIK3CA, and PTEN genes, suggests a different activating mechanism.