Oncogenic PIK3CA mutations in colorectal cancers and polyps

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Oncogenic PIK3CA mutations drive colorectal cancer via AKT signaling, impacting apoptosis and invasion.
• A potential synergy between PIK3CA and KRAS mutations may influence treatment resistance, though findings are conflicting.

Purpose of the Study:

• To investigate PIK3CA mutation frequency in relation to other molecular features in colorectal tumorigenesis.
• To clarify the association between PIK3CA mutations and KRAS mutations in advanced colorectal cancer.

Main Methods:

• Assessed PIK3CA mutations using high-resolution melt analysis in 829 colorectal cancer samples and 426 polyps.
• Correlated mutations with clinicopathological and molecular features, including KRAS, BRAF, MGMT methylation, and CIMP.
• Examined exon-specific mutations (Exon 9 and Exon 20) independently.

Main Results:

• PIK3CA mutation positively correlated with KRAS mutation, MGMT methylation, and CIMP.
• Exon 9 mutations linked to KRAS mutation, MGMT methylation, and CIMP-Low.
• Exon 20 mutations associated with serrated pathway features, BRAF mutation, microsatellite instability, and CIMP-High or Low.
• PIK3CA mutations were found in tubulovillous adenomas.

Conclusions:

• PIK3CA mutations exhibit distinct associations with molecular subtypes of colorectal cancer.
• These findings offer insights into the molecular drivers of traditional and serrated colorectal tumorigenesis pathways.