Detecting cancer mutations and aneuploidy in chromosomal segments
The invention provides methods, systems, and computer readable medium for detecting ploidy of chromosome segments or entire chromosomes, for detecting single nucleotide variants and for detecting both ploidy of chromosome segments and single nucleotide variants. In some aspects, the invention provides methods, systems, and computer readable medium for detecting cancer or a chromosomal abnormality in a gestating fetus.
1. A method for determining the genetic mutations in a solid tumor from an individual, comprising:
A. determining whether an aneuploidy mutation is present by analyzing a sample of blood or a fraction thereof from the individual to determine a level of allelic imbalance for each of a plurality of chromosomes or chromosome segments known to exhibit aneuploidy in cancer by:
isolating circulating tumor DNA from a blood sample, serum sample, or plasma sample from the individual,
amplifying at least 1000 polymorphic loci relating to cancer-associated aneuploidy from each of the plurality of chromosomes or chromosome segments of the circulating tumor DNA to obtain amplicons,
generating nucleic acid sequence data for a set of polymorphic loci on each of the plurality of chromosomes or chromosome segments by performing high throughput DNA sequencing of the amplicons,
using the nucleic acid sequence data to generate phased allelic data for the set of polymorphic loci on each of the plurality of chromosomes or chromosome segments, and
determining the level of allelic imbalance for each of the plurality of chromosomes or chromosome segments using the phased allelic data, wherein a detectable allelic imbalance is indicative of an aneuploidy mutation in the solid tumor for each of the plurality of chromosomal segments; and
B. determining whether a single nucleotide variant is present in a plurality of single nucleotide variant loci known to be associated with cancer by:
isolating circulating tumor DNA from a blood sample, serum sample, or plasma sample from the individual,
amplifying a plurality of polymorphic loci relating to cancer-associated single nucleotide variance loci from each of the plurality of chromosomes or chromosome segments of the circulating tumor DNA to obtain amplicons, and
performing high throughput DNA sequencing of the amplicons, wherein the presence of the single nucleotide variant in the sample for any of the plurality of single nucleotide loci is indicative of the presence of the single nucleotide variant in the solid tumor, thereby determining the genetic mutations in the solid tumor.
2. A method according to claim 1 , wherein the method further comprises estimating one or more normal host cell haplotypes for the plurality of polymorphic loci for non-cancerous host cells and using the estimated normal host cell haplotypes to determine the level of allelic imbalance present at each of the plurality of chromosomes or chromosome segments.
3. A method according to claim 2 , wherein the method for determining whether an aneuploidy mutation is present is capable of detecting an average allelic imbalance equal to or greater than 0.45%.
4. A method according to claim 1 , wherein the nucleic acid sequence data for the set of polymorphic loci on each of the plurality of chromosomes or chromosome segments is corrected for allele amplification bias, ambient contamination, and genotype contamination before it is used to determine the ploidy of the chromosomes or chromosome segment for each of the plurality of chromosomal segments.
5. A method according to claim 1 , wherein the nucleic acid sequence data for the set of polymorphic loci on each of the plurality of chromosomes or chromosome segments is corrected for allele amplification bias before it is used to determine the ploidy of the plurality of chromosomes or chromosome segments.
6. A method according to claim 4 , wherein the high throughput DNA sequencing of the set of polymorphic loci on each of the plurality of chromosomes or chromosome segments is performed on a plurality of copies of a series of amplicons generated by a multiplex amplification reaction performed under limiting primer conditions, and wherein each amplicon of the series of amplicons spans at least one polymorphic loci of each set of polymorphic loci.
7. A method according to claim 1 , wherein the plurality of chromosomes or chromosome segments known to exhibit aneuploidy in cancer comprises all of the chromosomal segments identified in the TCGA or COSMIC data sets as being associated with copy number variation in cancer.
8. A method according to claim 1 , comprising generating nucleic acid sequence data for 1000 to 50,000 polymorphic loci known to exhibit aneuploidy in cancer.
9. A method according to claim 1 , comprising generating nucleic acid sequence data for 25,000 to 100,000 polymorphic loci known to exhibit aneuploidy in cancer.
10. A method according to claim 1 , wherein the level of allelic imbalance is determined by modeling expected allelic frequencies for sets of hypothesis where cells have homolog deletions or amplifications, and identifying the maximum likelihood hypothesis.
11. A method according to claim 10 , wherein a likelihood of each hypothesis is determined at each polymorphic loci on each of the plurality of chromosomes or chromosome segments using a Bayesian classifier based on a beta binomial model of expected and observed allele frequencies.
12. A method according to claim 1 , wherein the high throughput DNA sequencing of the plurality of single nucleotide variance loci is performed by sequencing a plurality of copies of a series of amplicons generated from a multiplex amplification reaction, and wherein each amplicon of the series of amplicons spans at least one single nucleotide variant loci of the plurality of single nucleotide variance loci.
13. A method according to claim 12 , wherein the multiplex amplification reaction of the single nucleotide variance loci are performed under limiting primer conditions.
14. A method according to claim 12 , wherein an efficiency and an error rate per cycle are determined for each amplification reaction of the multiplex amplification reaction of the single nucleotide variance loci, and the efficiency and the error rate are used to determine whether a single nucleotide variance at the set of single variance loci is present in the sample.
15. A method according to claim 1 , wherein determining whether a single nucleotide variant is present in the sample, comprises identifying a confidence value for each allele determination at each of the set of single nucleotide variance loci based at least in part on a depth of read for the loci.
16. A method according to claim 1 , wherein the plurality of single nucleotide variance sites comprises all of the single nucleotide variance sites identified in the TCGA and COSMIC data sets.
17. A method according to claim 13 , wherein the method is performed with a depth of read for the plurality of single nucleotide variance loci of at least 100,000, and is capable of detecting a single nucleotide variant with a limit of quantification of 0.1% of the copies of that loci in the sample.
18. A method according to claim 1 , comprising generating nucleic acid sequence data for 100 to 1000 single nucleotide variance loci known to be associated with cancer.
19. A method according to claim 1 , wherein the method further comprises determining whether the aneuploidy mutation is present in a biopsy sample from a tumor found in the individual and determining whether the single nucleotide variant is present in the biopsy sample, before determining whether an aneuploidy mutation is present by analyzing the sample of blood or a fraction thereof and before determining whether a single nucleotide variant is present from the plurality of single nucleotide variant loci by analyzing the sample of blood or a fraction thereof, and using the aneuploidy mutation detection and the single nucleotide variant detection from the biopsy sample, in the aneuploidy determination and/or the single nucleotide variance determination of the sample of blood or a fraction thereof.
20. A method according to claim 1 , wherein the method further comprises in addition to performing the method on the sample of blood or a fraction thereof from the individual, performing the method on a control sample made by spiking between 0.5% and 3.5% of DNA from a cell line having an aneuploidy of a control chromosomal segment known to be associated with cancer into a nucleic acid preparation from a matched cell line known to be disomic for the control chromosome or chromosomal segment.
21. A method according to claim 1 , wherein the circulating tumor cell is from breast cancer or ovarian cancer.
22. A method according to claim 1 , wherein the same plasma sample from the individual is analyzed to determine whether the aneuploidy mutation is present and to determine whether the single nucleotide variant is present.