In situ Validation of the Serum Metabolite Markers
The top 10 characteristic metabolites discovered in serum were further
analyzed at the tissue level. Frozen cryosections of intact OSCC tumor
tissues were prepared for DESI-MSI analysis. Then the spatial
distribution of target metabolites across the resected OSCC tissues were
mapped and compared. The in situ validation by DESI-MSI revealed
that 8 out of top 10 metabolites showed the same trends of change with
OSCC in tissue and serum. (Figure S1 ). Taking lysoPC(20:4) and
PC(34:6) as examples, the former one declined in the cancer region
compared to the negative contrast region whereas the latter one was
elevated in the cancer region and can specifically delineate the cancer
margin. The low expression of lysoPC(20:4) and high expression of
PC(34:6) in the cancer region were consistent with their trends in the
serum cohort analysis (Figs. 2D, 2E, and 2F ).