Discovery and Qualification of Serum Protein Biomarker Candidates for Cholangiocarcinoma Diagnosis

Cholangiocarcinoma (CCA) is a major
health problem in northeastern
Thailand. The majority of CCA cases are clinically silent and difficult
to detect at an early stage. Although abdominal ultrasonography (US)
can detect premalignant periductal fibrosis (PDF), this method is
not suitable for screening populations in remote areas. With the goal
of developing a blood test for detecting CCA in the at-risk population,
we carried out serum protein biomarker discovery and qualification.
Label-free shotgun proteomics was performed on depleted serum samples
from 30 participants (n = 10 for US-normal, US-PDF,
and CCA groups). Of 40 protein candidates selected using multiple
reaction monitoring on 90 additional serum samples (n = 30 per group), 11 discriminatory proteins were obtained using
supervised multivariate statistical analysis. We further evaluated
3 candidates using ELISA and immunohistochemistry (IHC). S100A9, thioredoxin
(TRX), and cadherin-related family member 2 (CDHR2) were significantly
different between CCA and normal, and CCA and PDF groups when measured
in an additional 247 serum samples (P < 0.0001).
By IHC, TRX and CDHR2 were detected in the cytoplasm and nucleus of
CCA and inflammatory cells. S100A9 was detected in the infiltrating
tumor stroma immune cells. Proteomics discovery and qualification
in depleted sera revealed promising biomarker candidates for CCA diagnosis.