Discovery of SLC3A2 Cell Membrane Protein as a Potential Gastric Cancer Biomarker: Implications in Molecular Imaging

Despite decreasing incidence and mortality, gastric cancer
remains
the second leading cause of cancer-related deaths in the world. Successful
management of gastric cancer is hampered by lack of highly sensitive
and specific biomarkers especially for early cancer detection. Cell
surface proteins that are aberrantly expressed between normal and
cancer cells are potentially useful for cancer imaging and therapy
due to easy accessibility of these targets. Combining two-phase partition
and isobaric tags for relative and absolute quantification methods,
we compared the relative expression levels of membrane proteins between
noncancer and gastric cancer cells. About 33% of the data set was
found to be plasma membrane and associated proteins using this approach
(compared to only 11% in whole cell analysis), several
of which have never been previously implicated in gastric cancer.
Upregulation of SLC3A2 in gastric cancer cells was validated by immunoblotting
of a panel of 13 gastric cancer cell lines and immunohistochemistry
on tissue microarrays comprising 85 matched pairs of normal and tumor
tissues. Immunofluorescence and immunohistochemistry both confirmed
the plasma membrane localization of SLC3A2 in gastric cancer cells.
The data supported the notion that SLC3A2 is a potential biomarker
that could be exploited for molecular imaging-based detection of gastric
cancer.