PIK3CA Mutations in Hepatocellular Carcinoma in Korea

PURPOSE: Phosphatidylinositol 3-kinases/AKT pathway plays a pivotal role in hepatocellular carcinoma (HCC). Mutant PIK3CA, encoding the p110a catalytic subunit, stimulates the AKT pathway and promotes cell growth in various cancers. PIK3CA mutation rate has been usually reported as low frequency (<5%) in HCC except one report from Korea with 35.6%. Therefore, we investigated the frequency of PIK3CA mutations in Korean HCC patients. MATERIALS AND METHODS: We sequenced exons1, 3, 4, 6, 7, 8, 9, 19 and 20 of PIK3CA in 268 HCC tumor tissue samples by Sanger method and pyrosequencing assay. RESULTS: In this study, the mutations were not detected in exons3, 6, 8, and 19, and detected 1 at unknown SNP in exon1 and exon4, 2 at unknown SNP in exon7, 2 at unknown SNP in exon20. However, 1 at unknown SNP, 1 at G1635T and surprisingly all samples at A1634Cin exon9 were detected by Sanger method. Additional experiments with normal tissue, cloning experiments and a pyrosequencing assay revealed that the double peak at A1634C of exon9 is a pseudogene, not true mutation. The mutations found in this study were all different and small numbers, therefore, we cannot conclude specific relationship between clinical characteristics of HCC and mutation of PIK3CA. CONCLUSION: Our study suggests that the rate of PIK3CA mutation in the Korea population is in fact similar to the rates seen elsewhere in the world.

Novel EGFR-TK Inhibitor EKB-569 Inhibits Hepatocellular Carcinoma Cell Proliferation by AKT and MAPK Pathways

Epidermal growth factor receptor (EGFR)-targeted therapies have been effective in some cancers, but not in hepatocellular carcinoma (HCC). The aim of this study was to investigate the drug potential to overcome multi-drug resistance in HCC cells. Thirteen drug-sensitive HCC cells were assessed using the CCK-8 assay. G0-G1 arrest was measured by FACS. Western blot analysis was used to detect the key enzymes in both the Ras/Raf and PI3K pathways. When establishing the IC50 of HCC to several drugs, including EKB-569, sorafenib, erlotinib, gefitinib, pazopanib, and brivanib, SK-Hep1 cells treated with EKB-569 have shown the highest (72.8%-86.4%) G0-G1 arrest and decreased the phosphorylation of AKT and ERK at the protein level. We found that EKB-569 had higher efficacy in HCC, compared to first generation, reversible EGFR-TK inhibitors. Furthermore, the combination of sorafenib and EKB-569 showed a synergistic effect to inhibit proliferation of SNU-475, previously the most resistant cell to EGFR-TKIs. Therefore, novel EKB-569 in combination with sorafenib may be able to overcome HCC resistance to EGFR-TK inhibitors.