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PIK3CA mutation status in Japanese lung cancer patients
Osamu Kawano1, Hidefumi Sasaki, Katsuhiko Endo
1Department of Surgery II, Nagoya City University Medical School, Nagoya, Japan.
Abstract:
Somatic mutations of the PIK3CA (phosphatidylinostitol 3-kinase catalytic subunit) gene have been found in human cancer patients. Previous reports suggested that about 4% of lung cancers harbored PIK3CA gene mutations. However, the clinico-pathological background for PIK3CA gene mutations has not yet been investigated in lung cancer. We have genotyped the PIK3CA gene in Japanese lung cancer patients. The study included 235 lung cancer cases surgically removed in Nagoya City University Hospital. The two PIK3CA mutation hot spots (exon 9 and exon 20) were analyzed by real time polymerase chain reaction (PCR)-based assay. The data were confirmed by direct sequencing. In exon 9, somatic mutation was found in eight patients (3.4%). The mutation included three E542K (G1624A), three E545K (G1633A), one E542Q (G1624C), and one Q546K (C1636A). However, in exon 20, there was no mutation in our lung cancer patients. PIK3CA mutations were not correlated with gender (women versus men, p=0.4162), age (< or =60 versus >60, p=0.8027), or smoking status of the lung cancers (never versus smoker, p=0.5666). PIK3CA mutation incidence was significantly lower in adenocarcinoma (2/135, 1.5%) than in squamous cell carcinoma (5/77, 6.5%, p=0.0495). Among eight patients with a PIK3CA mutation, three patients also harbored an EGFR somatic mutation. PIK3CA gene mutations were rare in lung cancer; rarer in adenocarcinoma. Further functional analyses of the PIK3CA mutations are warranted to study if they could be the target of therapy for the lung cancer.
Insights
Somatic mutations in the PIK3CA gene are rare in lung cancer, particularly in adenocarcinoma. These PIK3CA mutations were not linked to patient demographics or smoking history.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Somatic mutations in the phosphatidylinositol 3-kinase catalytic subunit (PIK3CA) gene are observed in various human cancers.
- Previous studies indicated approximately 4% of lung cancers harbor PIK3CA mutations, but their clinical and pathological associations remain underexplored.
Purpose of the Study:
- To investigate the prevalence and clinico-pathological characteristics of PIK3CA gene mutations in Japanese lung cancer patients.
- To analyze mutation hotspots in exons 9 and 20 of the PIK3CA gene.
Main Methods:
- Genotyping of PIK3CA gene hotspots (exons 9 and 20) in 235 surgically resected Japanese lung cancer cases.
- Analysis using real-time polymerase chain reaction (PCR)-based assay, with data confirmed by direct sequencing.
Main Results:
- Somatic mutations in PIK3CA exon 9 were identified in 8 patients (3.4%), including E542K, E545K, E542Q, and Q546K variants.
- No mutations were detected in PIK3CA exon 20.
- PIK3CA mutations showed no significant correlation with gender, age, or smoking status.
- Mutation incidence was significantly lower in adenocarcinoma (1.5%) compared to squamous cell carcinoma (6.5%, p=0.0495).
- Three patients with PIK3CA mutations also had EGFR somatic mutations.
Conclusions:
- PIK3CA gene mutations are infrequent in lung cancer, with a notably lower incidence in adenocarcinoma.
- The findings suggest PIK3CA mutations in lung cancer are not strongly associated with common clinico-pathological factors.
- Further functional studies are needed to determine the therapeutic potential of targeting PIK3CA mutations in lung cancer.
