Methods and materials for assessing homologous recombination deficiency
This document provides methods and materials involved in assessing samples (e.g., cancer cells) for the presence of homologous recombination deficiency (HRD) or an HRD signature. For example, methods and materials for determining whether or not a cell (e.g., a cancer cell) contains an HRD signature are provided. Materials and methods for identifying cells (e.g., cancer cells) having a deficiency in homology directed repair (HDR) as well as materials and methods for identifying cancer patients likely to respond to a particular cancer treatment regimen also are provided.
1. An in vitro method of detecting DNA from a patient responder to a cancer treatment regimen comprising a DNA damaging agent, anthracycline, topoisomerase I inhibitor, or PARP (poly ADP ribose polymerase) inhibitor, the method comprising:
(i) extracting DNA from a sample comprising a cancer cell;
(ii) contacting the DNA with at least 500 oligonucleotide probes corresponding to one or more single nucleotide polymorphism (SNPs);
(iii) genotyping, using a computer, a plurality of SNP loci in the DNA that hybridizes to the oligonucleotide probes in (ii), wherein the SNP loci are spaced about 25 kb to about 100 kb apart on one or more chromosome pairs other than the human X/Y sex chromosome pair; and
(iv) detecting, using a computer, DNA comprising a loss of heterozygosity (LOH) Region, DNA comprising a telomeric allelic imbalance (TAI) Region, and DNA comprising a large scale transition (LST) Region,
wherein each LOH Region is characterized by loss of heterozygosity with a length of about 1.5 or more megabases but shorter than the length of the whole chromosome containing the LOH Region as determined by the presence or absence of SNP loci in corresponding regions on the one or more chromosome pairs; and
wherein each TAI Region is characterized by allelic imbalance that extends to one of the subtelomeres, does not cross the centromere and is equal to or longer than a second length that is at least 1.5 megabases, and
wherein each LST region is characterized by copy number transition along the length of the chromosome located between two regions, each longer than a third length that is at least 5 megabases, after filtering out copy number transitions along the length of the chromosome located between two regions, each shorter than a fourth length that is at most 4 megabases.
2. The method of claim 1 , wherein the LOH, TAI, and LST Regions are determined in at least two pairs of human chromosomes.
3. The method of claim 1 , wherein the cancer cell is an ovarian cancer cell, a breast cancer cell, or esophageal cancer cell.
4. The method of claim 1 ,
wherein LOH Regions are defined as LOH Regions at least 15 megabases in length but less than either a complete chromosome or a complete chromosome arm,
wherein TAI Regions are defined as TAI Regions at least 11 megabases in length but not extending across a centromere, and
wherein LST Regions are defined as LST Regions at least 10 megabases in length.
5. The method of claim 1 , wherein the DNA damaging agent is cisplatin, carboplatin, oxalaplatin, or picoplatin, the anthracycline is epirubincin or doxorubicin, the topoisomerase I inhibitor is campothecin, topotecan, or irinotecan, or the PARP inhibitor is olaparib, or velapirib.
6. An in vitro method of detecting presence of DNA from a patient responder to a cancer treatment regimen comprising a platinum agent, the method comprising:
(i) extracting DNA from a sample comprising a cancer cell; and
(ii) contacting the DNA with at least 500 oligonucleotide probes comprising one or more single nucleotide polymorphism (SNPs);
(iii) genotyping, using a computer, a plurality of SNP loci in the DNA that hybridizes to the oligonucleotide probes in (ii), wherein the SNP loci are spaced about 25 kb to about 100 kb apart on one or more chromosome pairs other than the human X/Y sex chromosome pair; and
(iv) detecting, using a computer, DNA comprising a loss of heterozygosity (LOH) Region, DNA comprising a telomeric allelic imbalance (TAI) Region, and DNA comprising a large scale transition (LST) Region,
wherein each LOH Region is characterized by loss of heterozygosity with a length of about 1.5 or more megabases but shorter than the length of the whole chromosome containing the LOH Region as determined by the presence or absence of SNP loci in corresponding regions on the one or more chromosome pairs, and
wherein each TAI Region is characterized by allelic imbalance that extends to one of the subtelomeres, does not cross the centromere and is equal to or longer than a second length that is at least 1.5 megabases, and
wherein each LST region is characterized by comprises the number of copy number transition along the length of the chromosome located between two regions, each longer than a third length that is at least 5 megabases, after filtering out copy number transitions along the length of the chromosome located between two regions, each shorter than a fourth length that is at most 4 megabases.
7. The method of claim 6 , wherein the LOH, TAI, and LST Regions are determined in at least two pairs of human chromosomes.
8. The method of claim 6 ,
wherein LOH Regions are defined as LOH Regions at least 15 megabases in length but less than either a complete chromosome or a complete chromosome arm,
wherein TAI Regions are defined as TAI Regions at least 11 megabases in length but not extending across a centromere, and
wherein LST Regions are defined as LST Regions at least 10 megabases in length.
9. The method of claim 6 , wherein the sample is deficient in BRCA1 or BRCA2 if a deleterious mutation, loss of heterozygosity, or high methylation is detected in either BRCA1 or BRCA2 in the sample.
10. The method of claim 9 , wherein high methylation is detected if methylation is detected in at least 5% of BRCA1 or BRCA2 promoter CpGs analyzed.