Methods of identifying novel proteins and antigens in cancer cells
The present invention provides methods of identifying neopeptides in abnormal cells, with the methods comprising sequencing long-read messenger RNA (mRNA) isolated from the abnormal cells, identifying splice variants that could be generated from the sequenced long-read mRNA, determining if the abnormal cells contain neopeptides that correlate with the identified splice variants. The methods may also comprise identifying at least one neoantigen on the neopeptides that are present in the abnormal cells.
1. A method for identifying a neopeptide in or on a population of cells that is a marker of abnormal cells, the method comprising
a) sequencing long-read messenger RNA (mRNA) isolated from a first subset of the population cells,
b) identifying splice variants generated from the sequenced long-read mRNA,
c) determining in a second subset of the population of cells presence of neopeptides that are translated from the identified splice variants and determining the presence of the neopeptide in a population of normal cells, wherein a single identified splice variant translates to a single neopeptide,
wherein, the presence of the neopeptide in the second subset of the population cells and absence of the neopeptide in the normal cells is indicative that the neopeptide is a marker for abnormal cells;
wherein the neopeptide comprises a novel splice variant; and
wherein the population of cells is a population of cancer cells, and the population of normal cells is a population of non-cancer cells of the same tissue origin as the population of cells.
2. The method of claim 1 , wherein the long-read mRNA is at least 70 nucleotides in length.
3. The method of claim 2 , wherein the long-read mRNA is between about 150 nucleotides and 300 nucleotides in length.
4. The method of claim 3 , wherein the long-read mRNA is between about 300 nucleotides and 10,000 nucleotides in length.
5. The method of claim 1 , wherein the long-read mRNA has not been fragmented prior to sequencing.
6. The method of claim 1 , wherein the isolated mRNA is cytosolic mRNA.
7. The method of claim 6 , wherein the cytosolic mRNA comprises a poly-A tail.
8. The method of claim 1 , wherein determining the presence of the neopeptides comprises mass spectrometry.
9. The method of claim 1 , wherein determining the presence of the neopeptides comprises generating antibodies capable of specifically binding the neopeptides and determining if the antibodies bind to the neopeptides.
10. The method of claim 1 , further comprising identifying at least one neoantigen on the neopeptide that is present in the second subset of the population of cells.