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Published on: November 5, 2019
Clinical application of oligonucleotide probe array for full-length gene sequencing of TP53 in colon cancer
Yasuo Takahashi1, Yukimoto Ishii, Toshihito Nagata
1Medical Research Center, Nihon University School of Medicine, Tokyo, Japan.
Objective:
TP53 mutations are the most frequent genetic alterations in colon cancer. We studied whether the recently developed oligonucleotide microarray technique, GeneChip p53 assay, can be applied to sensitive detection of TP53 gene mutations in surgical specimens from colon cancer patients.
Methods:
TP53 gene mutations in exons 2-11 in 20 colon cancers and the corresponding histopathologically normal mucosa at the surgical margins were assessed by GeneChip p53 assay, and the results were further evaluated by direct sequencing of the involved exon or by mutant-allele-specific amplification (MASA). The expression of TP53 protein was also evaluated immunohistochemically and the result was compared with the gene alteration.
Results:
The GeneChip p53 assay detected TP53 mutations in 65% of primary cancers; 61% of the mutations were within the evolutionarily conserved regions, and 46% of the mutations were within the zinc-binding domains (regions of loop 2 and loop 3). Direct sequencing confirmed these mutations. Immunohistochemical examination detected TP53 protein overexpression in 47% of primary cancers, but this protein did not accumulate with all types of TP53 mutations. In addition, the GeneChip assay detected a mutation identical to that in the primary tumor in 2 samples from the surgical margins, and MASA confirmed both mutations, implying the presence of occult cancer cells.
Conclusion:
The GeneChip p53 assay is sufficiently sensitive to detect TP53 mutations in surgical specimens from colon cancers and may be applicable to screening examination in clinical laboratories as a routine procedure.
Insights
The GeneChip p53 assay effectively detects TP53 gene mutations in colon cancer specimens. This sensitive method shows promise for routine clinical screening of colon cancer patients.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- TP53 mutations are prevalent in colon cancer.
- Accurate detection of these mutations is crucial for diagnosis and treatment.
Purpose of the Study:
- To evaluate the sensitivity and applicability of the GeneChip p53 assay for detecting TP53 gene mutations in colon cancer surgical specimens.
- To compare mutation detection with TP53 protein expression.
Main Methods:
- Assessed TP53 gene mutations in exons 2-11 of 20 colon cancers and adjacent normal mucosa using the GeneChip p53 assay.
- Validated findings with direct sequencing and mutant-allele-specific amplification (MASA).
- Evaluated TP53 protein expression via immunohistochemistry.
Main Results:
- The GeneChip p53 assay identified TP53 mutations in 65% of primary colon cancers, with many in conserved functional domains.
- Direct sequencing confirmed assay results.
- TP53 protein overexpression was observed in 47% of cancers, but did not correlate with all mutation types.
- The assay detected occult tumor cells in surgical margins.
Conclusions:
- The GeneChip p53 assay demonstrates high sensitivity for detecting TP53 mutations in colon cancer surgical specimens.
- This technique is suitable for routine screening in clinical laboratories.
- The findings highlight the assay's potential for identifying minimal residual disease.
