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Digital PCR-Based Method for Detecting CDKN2A Loss in Brain Tumours
Shlomo Tsuriel1, Victoria Hannes2, Asala Hasona2,3
1Institute of Pathology, Tel-Aviv Sourasky Medical Center, 62431, Tel-Aviv, Israel. shlomots@tlvmc.gov.il.
Introduction:
CDKN2A is a key tumour suppressor gene and loss of CDKN2A can be found in many tumours. In astrocytoma grade IV, CDKN2A is deleted in more than 50% of tumours. In many instances, low-grade gliomas with homozygous loss of CDKN2A behave like high grade tumours. The available techniques for CDKN2A loss are laborious, expensive, unreliable, or unavailable in most pathology institutes. Therefore, although it is essential for accurate brain tumour diagnosis, the routine diagnosis does not include testing for CDKN2A deletion.
Methods:
We developed a digital polymerase chain reaction (dPCR) assay for CDKN2A loss detection. The assay is based on counting the copy number of CDKN2A gene and of a reference gene on the same chromosome. It was tested for the detection limit with regard to tumour content and minimal DNA quantity. It was then tested on 24 clinical samples with known CDKN2A status. Additionally, we tested 44 gliomas with unknown CDKN2A status.
Results:
We found that the newly developed assay is reliable in tissue with more than 50% tumour content and more than 0.4 ng of DNA. The validation cohort showed complete concordance, and we were able to detect homozygous loss in 16 gliomas with unknown CDKN2A status.
Discussion:
The method presented can give a fast, cost-effective, clinically reliable evaluation of CDKN2A loss in tissue with more than 50% tumour content. Its ability to work with old samples and with low amounts of DNA makes it the favoured assay in cases where other techniques fail.
Insights
A new digital PCR assay reliably detects CDKN2A loss in brain tumors, crucial for accurate diagnosis. This cost-effective method works with limited DNA and old samples, improving glioma classification.
Area of Science:
- Oncology
- Molecular Diagnostics
- Genetics
Background:
- CDKN2A is a critical tumor suppressor gene frequently lost in high-grade astrocytomas.
- Loss of CDKN2A in low-grade gliomas can lead to aggressive tumor behavior.
- Current methods for detecting CDKN2A loss are often impractical for routine pathology.
Purpose of the Study:
- To develop and validate a digital PCR (dPCR) assay for reliable CDKN2A deletion detection.
- To establish the assay's performance characteristics regarding tumor content and DNA quantity.
- To assess the clinical utility of the dPCR assay in glioma diagnosis.
Main Methods:
- Developed a dPCR assay quantifying CDKN2A gene copy number relative to a reference gene.
- Determined assay sensitivity using varying tumor content and DNA amounts.
- Validated the assay on clinical samples with known and unknown CDKN2A deletion status.
Main Results:
- The dPCR assay demonstrated reliability in samples with >50% tumor content and >0.4 ng DNA.
- Complete concordance was observed in the validation cohort.
- Homozygous CDKN2A loss was detected in 16 previously uncharacterized gliomas.
Conclusions:
- The dPCR assay provides a fast, cost-effective, and clinically reliable method for evaluating CDKN2A loss.
- The assay's ability to use degraded DNA and small sample amounts makes it valuable for challenging cases.
- This assay can significantly improve the accuracy of brain tumor diagnosis and classification.
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