KRAS insertions in colorectal cancer: what do we know about unusual KRAS mutations?

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• KRAS mutations are established negative predictors of anti-EGFR therapy response in colorectal cancer (CRC).
• Common KRAS mutations involve codons 12, 13, and 61; however, KRAS insertions are infrequently reported and poorly understood regarding RAS pathway activation.
• Limited data on KRAS insertion frequency and nucleotide additions hinders patient management for those with these mutations.

Purpose of the Study:

• To report on KRAS insertions in colorectal cancer (CRC).
• To characterize the frequency and type of KRAS insertions in CRC.
• To discuss a specific case of KRAS insertion and its diagnostic implications.

Main Methods:

• Pyrosequencing and Sanger sequencing were utilized to detect KRAS and BRAF mutations in paraffin-embedded CRC samples.
• Immunohistochemistry was employed to assess mismatch repair protein expression.

Main Results:

• A GGT insertion between codons 12 and 13 (c.36_37insGGT;p.G12_G13insG) was identified in a CRC patient.
• KRAS insertions were found to be rare in CRC, with c.36_37insGGT being the most frequent type observed.
• The study highlights the diagnostic and clinical challenges associated with identifying and interpreting KRAS insertions.

Conclusions:

• KRAS gene insertions in CRC pose diagnostic and clinical challenges due to unusual sequencing findings.
• The clinical impact of KRAS insertions remains largely unknown, necessitating further investigation.
• Improved understanding and detection methods for KRAS insertions are crucial for optimizing colorectal cancer patient management.