Homologous Recombination Abnormalities Associated With BRCA1/2 Mutations as Predicted by Machine Learning of Targeted
Maher Albitar1, Hong Zhang1, Andrew Pecora2
1Genomic Testing Cooperative, Irvine, CA, USA.
Background:
Homologous recombination deficiency (HRD) is the hallmark of breast cancer gene 1/2 (BRCA1/2)-mutated tumors and the unique biomarker for predicting response to double-strand break (DSB)-inducing drugs. The demonstration of HRD in tumors with mutations in genes other than BRCA1/2 is considered the best biomarker of potential response to these DSB-inducer drugs.
Objectives:
We explored the potential of developing a practical approach to predict in any tumor the presence of HRD that is similar to that seen in tumors with BRCA1/2 mutations using next-generation sequencing (NGS) along with machine learning (ML).
Design:
We use copy number alteration (CNA) generated from routine-targeted NGS data along with a modified naïve Bayesian model for the prediction of the presence of HRD.
Methods:
The CNA from NGS of 434 targeted genes was analyzed using CNVkit software to calculate the log2 of CNA changes. The log2 values of various sequencing reads (bins) were used in ML to train the system on predicting tumors with BRCA1/2 mutations and tumors with abnormalities similar to those detected in BRCA1/2 mutations.
Results:
Using 31 breast or ovarian cancers with BRCA1/2 mutations and 84 tumors without mutations in any of 12 homologous recombination repair (HRR) genes, the ML demonstrated high sensitivity (90%, 95% confidence interval [CI] = 73%-97.5%) and specificity (98%, 95% CI = 90%-100%). Testing of 114 tumors with mutations in HRR genes other than BRCA1/2 showed 39% positivity for HRD similar to that seen in BRCA1/2. Testing 213 additional wild-type (WT) cancers showed HRD positivity similar to BRCA1/2 in 32% of cases. Correlation with proportional loss of heterozygosity (LOH) as determined using whole exome sequencing of 51 samples showed 90% (95% CI = 72%-97%) concordance. The approach was also validated in an independent set of 1312 consecutive tumor samples.
Conclusions:
These data demonstrate that CNA when combined with ML can reliably predict the presence of BRCA1/2 level HRD with high specificity. Using BRCA1/2 mutant cases as gold standard, this ML can be used to predict HRD in cancers with mutations in other HRR genes as well as in WT tumors.
Insights
This study developed a machine learning model using next-generation sequencing data to accurately predict homologous recombination deficiency (HRD) in tumors. The model shows high sensitivity and specificity, aiding in identifying potential responses to double-strand break-inducing drugs.
Area of Science:
- Oncology
- Genomics
- Bioinformatics
Background:
- Homologous recombination deficiency (HRD) is a key biomarker for predicting response to double-strand break (DSB)-inducing drugs, particularly in BRCA1/2-mutated cancers.
- Identifying HRD in tumors with mutations in other homologous recombination repair (HRR) genes or in wild-type (WT) tumors is crucial for expanding therapeutic options.
Purpose of the Study:
- To develop a practical, next-generation sequencing (NGS)-based approach using machine learning (ML) to predict HRD in any tumor.
- To establish a method for identifying HRD similar to that observed in BRCA1/2 mutations across diverse tumor types.
Main Methods:
- Utilized copy number alteration (CNA) data derived from targeted NGS of 434 genes.
- Employed a modified naïve Bayesian model for HRD prediction, training the ML system on CNA log2 values.
- Validated the approach using independent cohorts of breast, ovarian, and other wild-type cancers.
Main Results:
- The ML model achieved high sensitivity (90%) and specificity (98%) in predicting HRD.
- Demonstrated 39% HRD positivity in tumors with HRR gene mutations (excluding BRCA1/2) and 32% in WT cancers.
- Showed 90% concordance with loss of heterozygosity (LOH) and validated in over 1300 samples.
Conclusions:
- Copy number alterations combined with ML reliably predict BRCA1/2-level HRD with high specificity.
- The developed ML model can effectively predict HRD in cancers with non-BRCA1/2 HRR gene mutations and in WT tumors.
- This approach offers a promising tool for identifying patients who may benefit from DSB-inducing therapies.
Related Concept Videos
Mismatch Repair
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
Homologous Recombination
Crossing Over
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...


