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Absence of PIK3CA hotspot mutations in hepatocellular carcinoma in Japanese patients

Y Tanaka1, F Kanai, M Tada

  • 1Department of Gastroenterology, Graduate School of Medicine, University of Tokyo, Japan.

Oncogene
|December 7, 2005
PubMed

Insights

A study investigating PIK3CA hotspot mutations in Japanese hepatocellular carcinoma (HCC) found none. Unexpected sequences resembling a PIK3CA pseudogene were detected in both cancerous and non-cancerous tissues.

Area of Science:

  • Oncology
  • Molecular Biology
  • Genetics

Background:

  • The phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) gene is frequently somatically mutated in various cancers.
  • PIK3CA mutations are reported in an estimated 35.6% of hepatocellular carcinoma (HCC) cases, suggesting its oncogenic role.

Purpose of the Study:

  • To determine the frequency of PIK3CA hotspot mutations in Japanese HCC patients.
  • To investigate unexpected findings during PIK3CA mutation analysis in HCC samples.

Main Methods:

  • Sequencing of exons 9 and 20 of the PIK3CA gene in 47 clinical HCC samples.
  • Analysis of PCR chromatograms for abnormal migration patterns.
  • PCR amplification, cloning, and sequencing to identify anomalous DNA sequences.

Main Results:

  • No PIK3CA hotspot mutations were detected in any of the 47 Japanese HCC samples.
  • Abnormally migrating waves in PCR chromatograms from 13 samples were identified as a mix of wild-type PIK3CA and a sequence from a PIK3CA pseudogene on chromosome 22q11.2.
  • These anomalies were also present in non-cancerous liver tissue, indicating they are not HCC-specific mutations.

Conclusions:

  • The frequency of PIK3CA hotspot mutations in Japanese HCC patients may be lower than previously reported.
  • The observed anomalies are likely due to the presence of a PIK3CA pseudogene, not somatic mutations driving HCC.
  • Further investigation is needed to clarify the role of PIK3CA alterations in HCC pathogenesis in this population.

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