Identification of EFEMP2 as a Serum Biomarker for the Early Detection of Colorectal Cancer with Lectin Affinity Capture Assisted Secretome Analysis of Cultured Fresh Tissues

Early diagnosis plays a decisive role in the outcome
of colorectal
cancer (CRC) therapy. The ex vivo culture of fresh CRC tissues and
paired normal colorectal tissues provides a feasible way to explore
potential serum biomarkers for CRC early detection under near-physiological
conditions. In the present work, we applied a lectin affinity based
approach to enrich and increase the detection number of secreted proteins
in the conditioned media of cultured tissues. The captured proteins
were then analyzed by the proteomic strategy of one-dimensional gel
electrophoresis coupled to liquid chromatography–tandem mass
spectrometry. By quantification with label-free spectral counting,
we found 123 differentially expressed secreted proteins (DESPs) with
68 DESPs up-regulated in CRC tissues. EFEMP2, one of the top 10 up-regulated
DESPs, was further validated by immunohistochemistry at tissue level
and enzyme-linked immunosorbent assay at serum level. We found the
expression level of EFEMP2 was dramatically increased in CRC patients,
even at the early stage. Moreover, the diagnostic accuracy of EFEMP2
was superior to the established CRC biomarker carcinoembryonic antigen
evidenced by the area under the receiver operating characteristic
curve for the two biomarkers were 0.923 and 0.728, respectively. These
results indicated EFEMP2 is a promising serum biomarker for CRC early
detection.