Detection of Biomarkers with Solid-Phase Proximity Ligation Assay in Patients with Colorectal Cancer.
BACKGROUND
In the search for prognostic biomarkers, a significant amount of precious biobanked blood samples is needed for conventional analyses. Solid-phase proximity ligation assay (SP-PLA) is an analytic method with the ability to analyze many proteins at the same time in small amounts of plasma. The aim of this study was to explore the potential use of SP-PLA for biomarker validation in patients with colorectal cancer (CRC).


METHODS
Plasma samples from patients with stage I to IV CRC, with (n = 31) and without (n = 29) disease dissemination at diagnosis or later, were analyzed with SP-PLA using 35 antibodies targeting an equal number of proteins in 5-μl plasma samples. Carcinoembryonic antigen (CEA), analyzed earlier in this cohort using a different technology, was used as a reference.


RESULTS
A total of 21 of the 35 investigated proteins were detectable with SP-PLA. Patients in stage II to III with disseminated disease had lower plasma concentrations of HCC-4 (P = .025). Low plasma levels of tissue inhibitor of metalloproteinases-1 were seen in patients with disseminated disease stage II (P = .003). The level of CEA was higher in patients with disease dissemination compared with those without (P = .007).


CONCLUSIONS
SP-PLA has the ability to analyze many protein markers simultaneously in a small amount of blood. However, none of the markers selected for the present SP-PLA analyses gave better prognostic information than CEA.
Department of Surgical Science, University of Uppsala, Uppsala, Sweden. Electronic address: arezo_g@hotmail.com.
Lana
L
Ghanipour
Department of Immunology, Genetics and Pathology, Science for Life Laboratory, University of Uppsala, Uppsala, Sweden.
Spyros
S
Darmanis
Department of Immunology, Genetics and Pathology, Science for Life Laboratory, University of Uppsala, Uppsala, Sweden.
Ulf
U
Landegren
Department of Radiology, Oncology and Radiation Science, University of Uppsala, Uppsala, Sweden.
Bengt
B
Glimelius
Department of Surgical Science, University of Uppsala, Uppsala, Sweden.
Lars
L
Påhlman
Department of Surgical Science, University of Uppsala, Uppsala, Sweden.
Helgi
H
Birgisson