Tumor mutation burden
The invention provides methods for determining the mutation burden of a tumor by assaying tumor DNA that is representative of genetic loci that are themselves representative of genetics of the tumor. The assayed tumor DNA may be itself agnostic as to loci, so long as it is representative of loci that are representative of tumor mutation burden. The invention provides for assays in which the tumor DNA being sequenced or tested can be something other than, and possibly less than, a full panel of oncogenes that is expected to stand for a tumor's mutational load.
1. A method of analyzing a tumor, the method comprising:
obtaining a representative sample of a tumor, the sample comprising tumor DNA;
performing an enrichment of a target nucleic acid in the representative sample by introducing a Cas endonuclease and associated guide RNA to bind and protect the target nucleic acid in the tumor DNA that is representative of mutations in the tumor in a sequence-specific manner, and degrading unprotected nucleic acids with an exonuclease;
sequencing the target nucleic acid to identify mutations;
associating the identified mutations with a tumor mutation burden (TMB) of the tumor; and
reporting the TMB based on the identified mutations.
2. The method of claim 1 , wherein the representative sample comprises tissue obtained by tumor biopsy.
3. The method of claim 1 , further comprising isolating the target nucleic acid from the representative sample without targeting known, specified tumor biomarkers.
4. The method of claim 1 , wherein the target nucleic acid comprises one or more DNA fragments at least a few kilobases in length.
5. The method of claim 1 , further comprising demonstrating that the target nucleic acid is representative of the tumor DNA.
6. The method of claim 5 , wherein the demonstrating includes a genome-wide association study.
7. The method of claim 1 , wherein the target nucleic acid does not include any portion of any oncogene.
8. The method of claim 1 , wherein identifying the mutations includes determining differences between the target nucleic acid and matched normal DNA.
9. The method of claim 8 , wherein determining differences between the target nucleic acid and the matched normal DNA comprises:
sequencing the target nucleic acid and the matched normal DNA to produce tumor sequences and normal sequences; and
aligning the tumor sequences to the normal sequences.
10. The method of claim 9 , further comprising aligning the tumor sequences or the normal sequences to a reference genome, and further wherein the differences include bases and small indels in the tumor DNA that are unmatched at homologous portions of the normal DNA and the reference genome.
11. The method of claim 1 , wherein the tumor DNA comprises one or more housekeeping genes.
12. The method of claim 1 , wherein the target nucleic acid comprises fewer than one million bases of DNA.
13. The method of claim 1 , wherein the representative sample comprises plasma comprising cell-free DNA from the patient, and wherein the tumor DNA is circulating tumor DNA from the sample.