SPOP mutation in prostate cancers in Korean population: Variation in its mutation frequency among ethnic groups

Speckle-type POZ protein, SPOP, mediates SRC-3 oncogene ubiquitination and proteolysis in human cancer. Frequent SPOP mutation is observed in exome sequencing of prostate cancer (Pca) in western population. We performed SPOP mutation analysis and investigated its protein expression of PCa in Korean population. We selected 108 cases of prostatectomy specimen for PCa at Samsung Medical Center in Seoul, Korea from 1995 to 2006. All cases were sequenced by Sanger sequencing to analyze SPOP somatic mutations in paraffin-embedded tissue. In addition, we also applied SPOP immunohistochemistry (IHC) on the tissue microarray blocks for 108 cases. All cases were successfully sequenced. Three missense mutations, p.Phe102Cys in one case and double mutation with p.Phe125Val and p.Glu145 Lys in another case, were identified (1.85%). p.Phe102Cys and p.Phe125Val have been previously reported in the literature; however, p.Glu145 Lys was newly discovered in this study. All but one case were successfully stained with IHC. Thirty two (32.7%) out of 107 cases showed SPOP expression loss and loss of SPOP expression was not correlated with mutation status. In conclusion, we identified three missense mutations including double mutation in 108 PCa in Korean population. The incidence (2/108, 1.85%) is lower than previous studies which had done in western population.