Gene fusions and alternatively spliced junctions associated with breast cancer
The present invention relates to gene fusions and alternative spliced junctions associated with breast cancer. The present invention also relates to novel methods of identifying gene fusions and alternative spliced junctions in RNA sequencing data. The present invention further relates to predicting prognosis of a breast cancer patient based on the number of gene fusion events.
1. A method for identifying a gene fusion in a biological sample obtained from a human subject, wherein the biological sample is a formalin-fixed paraffin embedded (FFPE) sample, comprising:
obtaining a plurality of reads from RNA sequencing of the biological sample;
mapping a read to the human genome;
determining whether the read comprises a distant spliced junction;
selecting the read comprising a distant spliced junction;
identifying a candidate gene fusion comprising the distant spliced junction;
creating a first set of templates for the candidate gene fusion, wherein the first set of templates comprises:
(1) a fusion template comprising 50 base pairs (bp) of exonic sequence of a preserved region of a donor gene and 50 bp of exonic sequence of a preserved region of an acceptor gene,
(2) a donor template comprising 50 bp of exonic sequence of a preserved region of a donor gene and 50 bp of exonic sequence of a discarded region of a donor gene,
(3) an acceptor template comprising 50 bp of exonic sequence of a discarded region of an acceptor gene and 50 bp of exonic sequence of a preserved region of an acceptor gene,
(4) a donor genomic template comprising 50 bp upstream genomic sequence of a donor splicing site and 50 bp downstream genomic sequence of a donor splicing site, and
(5) an acceptor genomic template comprising 50 bp upstream genomic sequence of an acceptor splicing site and 50 bp downstream genomic sequence of an acceptor splicing site;
removing the candidate gene fusion if any of the first template set sequences are identical, but map to different genes in the human genome;
creating a second set of templates comprising:
(a) a fusion template comprising 150 bp of exonic sequence of a preserved region of a donor gene and 150 bp of exonic sequence of a preserved region of an acceptor gene,
(b) a donor template comprising 150 bp of exonic sequence of a preserved region of a donor gene and 150 bp of exonic sequence of a discarded region of a donor gene,
(c) an acceptor template comprising 150 bp of exonic sequence of a discarded region of an acceptor gene and 150 bp of exonic sequence of a preserved region of an acceptor gene,
(d) a donor genomic template comprising 150 bp upstream genomic sequence of a donor splicing site and 150 bp downstream genomic sequence of a donor splicing site, and
(e) an acceptor genomic template comprising 150 bp upstream genomic sequence of an acceptor splicing site and 150 bp downstream genomic sequence of an acceptor splicing site;
determining the homology between templates (b) and (c) and between templates (d) and (e);
removing the candidate gene fusion if templates (b) and (c) are homologous or if templates (d) and (e) are homologous; and
aligning a read obtained from RNA sequencing of the biological sample to the first set of templates;
selecting the read that maps to the fusion template of the first set of templates; and
identifying a gene fusion, wherein the gene fusion is identified by at least two non-duplicate reads that map to the fusion template of the first set of templates.
2. The method of claim 1 , further comprising preparing a report based on the identification of a gene fusion.
3. The method of claim 1 , wherein the read is a single end read.
4. The method of claim 1 , wherein the read is a paired-end read.
5. The method of claim 1 , wherein the read is at least 50 bases.
6. The method of claim 1 , wherein human subject is a cancer patient, and the cancer is selected from breast cancer, colon cancer, lung cancer, prostate cancer, hepatocellular cancer, gastric cancer, pancreatic cancer, cervical cancer, ovarian cancer, liver cancer, bladder cancer, cancer of the urinary tract, thyroid cancer, renal cancer, carcinoma, melanoma, and brain cancer.