Quantitative Analysis of Single Amino Acid Variant Peptides Associated with Pancreatic Cancer in Serum by an Isobaric Labeling Quantitative Method

Single
amino acid variations are highly associated with many human
diseases. The direct detection of peptides containing single amino
acid variants (SAAVs) derived from nonsynonymous single nucleotide
polymorphisms (SNPs) in serum can provide unique opportunities for
SAAV associated biomarker discovery. In the present study, an isobaric
labeling quantitative strategy was applied to identify and quantify
variant peptides in serum samples of pancreatic cancer patients and
other benign controls. The largest number of SAAV peptides to date
in serum including 96 unique variant peptides were quantified in this
quantitative analysis, of which five variant peptides showed a statistically
significant difference between pancreatic cancer and other controls
(p-value < 0.05). Significant differences in the
variant peptide SDNCEDTPEAGYFAVAVVK from serotransferrin were detected between pancreatic cancer
and controls, which was further validated by selected reaction monitoring
(SRM) analysis. The novel biomarker panel obtained by combining α-1-antichymotrypsin
(AACT), Thrombospondin-1 (THBS1) and this variant peptide showed an
excellent diagnostic performance in discriminating pancreatic cancer
from healthy controls (AUC = 0.98) and chronic pancreatitis (AUC =
0.90). These results suggest that large-scale analysis of SAAV peptides
in serum may provide a new direction for biomarker discovery research.