Combinatorial DNA screening
The present disclosure relates to methods for detecting unique genetic signatures derived from markers such as, for example, mutations, somatic or germ-line, in nucleic acids obtained from biological samples. The sensitivity of the methods provides for detection of mutations associated with a disease, e.g., cancer mutations, or with inherited disease, e.g., an autosomal recessive disease, in a noninvasive manner at ultra-low proportions of sequences carrying mutations to sequences carrying normal, e.g., non-cancer sequences, or a reference sequence, e.g., a human reference genome.
1. A method for detecting circulating tumor DNA in a fluid sample, comprising:
(a) obtaining a tumor sample and a non-tumor sample from in the fluid sample cancer patient
(b) sequencing genomic DNA from the tumor sample and sequencing genomic DNA from the non-tumor sample, thereby obtaining sequences of genomic DNA from the tumor sample and sequences of genomic DNA from the non-tumor sample;
(c) aligning the sequences of genomic DNA from the tumor sample to a reference human genome that is not from the patient thereby obtaining a set of tumor-specific mutations and further obtaining from the set of tumor-specific mutations a set of tumor-specific somatic mutation sequences that are present in the sequences of genomic DNA from the tumor sample but not present in the sequences of genomic DNA from the non-tumor sample;
(d) obtaining a fluid sample from the cancer patient;
(e) enriching a fraction of DNA from the fluid sample by:
(i) extracting DNA from the fluid sample to obtain cell-free DNA (cfDNA) fragments;
(ii) producing, from the extracted cfDNA fragments, an enriched fraction of DNA comprising fragments of circulating tumor DNA (ctDNA) by:
(A) contacting the extracted cfDNA fragments with a plurality of oligonucleotide probes that bind to a patient-specific signature panel, wherein each oligonucleotide probe comprises a nucleic acid sequence that is capable of hybridizing to a target sequence comprising one of the tumor-specific somatic mutation sequences a subset of somatic mutations or a corresponding unmutated sequence;
(B) selectively enriching the extracted cfDNA fragments with the plurality of oligonucleotide probes, thereby isolating the fraction of DNA;
wherein the patient-specific signature panel comprises greater than 10 tumor-specific somatic mutations present in the tumor sample of the patient;
(f) sequencing the fraction of DNA, thereby obtaining a plurality of sequence reads; and
(g) detecting the presence or absence of the ctDNA, wherein the presence of one or more sequence reads in the plurality of sequence reads corresponding to one or more of the tumor-specific somatic mutation sequences indicates the presence of ctDNA in the fluid sample.
2. The method of claim 1 , wherein sequencing genomic DNA from the tumor sample and sequencing genomic DNA from the non-tumor sample comprises whole genome sequencing or targeted sequencing.
3. The method of claim 2 , wherein the targeted sequencing comprises sequencing introns, exons, or a combination thereof.
4. The method of claim 2 , wherein sequencing genomic DNA from the tumor sample of the patient and sequencing genomic DNA from the non-tumor sample of the patient comprises whole genome sequencing.
5. The method of claim 1 , further comprising repeating (d)-(g) of the method at one or more times during a treatment.
6. The method of claim 1 , further comprising repeating (d)-(g) of the method at one or more times following completion of treatment.
7. The method of claim 1 , wherein the tumor-specific somatic mutations comprise one or more mutations selected from SNPs, insertions, deletions, and translocations.
8. The method of claim 1 , wherein the fluid sample is a blood sample.
9. The method of claim 1 , wherein the fluid sample is a blood plasma sample.
10. A method for detecting circulating tumor DNA (ctDNA) in a fluid sample from a patient, comprising:
(a) obtaining a tumor sample and a non-tumor sample from the patient
(b) sequencing genomic DNA from the tumor sample and sequencing genomic DNA from the non-tumor sample, thereby obtaining sequences of genomic DNA from the tumor sample and sequences of genomic DNA from the non-tumor sample;
(c) aligning the sequences of genomic DNA from the tumor sample to a reference human genome that is not from the patient, thereby obtaining a set of tumor-specific mutations and further obtaining from the set of tumor-specific mutations a set of tumor-specific somatic mutation sequences that are present in the sequences of genomic DNA from the tumor sample but not present in the sequences of genomic DNA from the non-tumor sample;
(d) extracting cell-free DNA (cfDNA) fragments from a fluid sample obtained from a patient;
(e) contacting the extracted cfDNA fragments with a plurality of oligonucleotide probes that bind to a patient-specific signature panel,
wherein each oligonucleotide probe in the plurality comprises a nucleic acid sequence that is capable of hybridizing to a target sequence comprising one of a predetermined subset comprising greater than 10 of the tumor-specific somatic mutation sequences present in the tumor sample obtained from the patient, and
(f) enriching a fraction of cfDNA corresponding to the patient-specific signature panel from the extracted cfDNA fragments by:
(i) hybrid capture-based enrichment;
(ii) PCR-target enrichment; or
(iii) on-sequencer enrichment;
(g) sequencing the enriched fraction of cfDNA thereby obtaining a plurality of sequence reads; and
(h) detecting the presence or absence of ctDNA in the enriched fraction of cfDNA, wherein the presence of one or more sequence reads in the plurality of sequence reads corresponding to one or more of the tumor-specific somatic mutation sequences indicates the presence of ctDNA in the fluid sample.
11. The method of claim 10 , wherein the sequencing in (b) comprises whole genome sequencing or targeted sequencing.
12. The method of claim 11 , wherein the targeted sequencing comprises sequencing introns, exons, or a combination thereof.
13. The method of claim 10 , further comprising repeating (d)-(h) of the method at one or more times during a treatment.
14. The method of claim 10 , wherein the predetermined set of tumor-specific somatic mutations comprise one or more mutations selected from SNPs, insertions, deletions, and translocations.
15. The method of claim 10 , wherein the fluid sample is a blood sample.
16. The method of claim 10 , wherein the fluid sample is a blood plasma sample.
17. The method of claim 1 , wherein the patient-specific signature panel comprises greater than 50 tumor-specific somatic mutations present in a tumor sample obtained from the patient.
18. The method of claim 10 , wherein the predetermined subset comprises greater than 50 tumor-specific somatic mutations present in a tumor sample obtained from the patient.