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Intratumorous heterogeneity for RAS mutations in a treatment-naïve colorectal tumour
Sebastian Lunke1, Belinda Lee2, Sevastjan Kranz3
1Department of Pathology, University of Melbourne, Melbourne, Victoria, Australia.
Abstract:
Activating mutations in KRAS and NRAS genes in patients with colorectal cancer (CRC) are associated with a lack of response to treatment with anti-epidermal growth factor receptor (EGFR) therapies. Mutations in these genes are thought to be mutually exclusive, however reports have described CRCs with two activating rat sarcoma (RAS) mutations. This has fuelled discussion about whether these mutations are the result of intratumorous heterogeneity, or if they are co-occurring in the same cancer cell clone. We present a case of a colorectal tumour with three RAS mutations detected during routine diagnostic testing. Further detailed analysis with laser capture microdissection and next generation sequencing excluded the possibility of all three mutations being present in the same clone, presenting the highest resolution evidence of intratumorous heterogeneity of RAS mutations to date.
Insights
Colorectal tumors can have multiple RAS gene mutations. This study found three RAS mutations in one tumor, proving they arise from different cells, not one clone.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Activating mutations in KRAS and NRAS genes predict poor response to anti-EGFR therapies in colorectal cancer (CRC).
- RAS mutations are typically considered mutually exclusive within a single tumor.
- Intratumorous heterogeneity of RAS mutations is debated, with implications for treatment strategies.
Observation:
- A colorectal tumor sample revealed three distinct RAS gene mutations during routine diagnostics.
- Advanced techniques, including laser capture microdissection and next-generation sequencing, were employed for detailed analysis.
- The study investigated the clonal origin of multiple RAS mutations within the tumor.
Findings:
- Analysis confirmed that the three detected RAS mutations were not present in the same cancer cell clone.
- This finding provides strong evidence against co-occurrence within a single clone.
- The results demonstrate significant intratumorous heterogeneity of RAS mutations.
Implications:
- This case offers the highest resolution evidence to date of intratumorous heterogeneity for RAS mutations in colorectal cancer.
- Understanding RAS mutation heterogeneity is crucial for accurate patient stratification and optimizing anti-EGFR therapy selection.
- Further research into the clonal evolution and clinical significance of heterogeneous RAS mutations in CRC is warranted.
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