Fig. 2

Metabolic differences between non-cancer epithelium (NCE), stroma, and cancer identified by orthogonalized partial least squares discrimination analysis (OPLS-DA). The first OPLS-DA latent variable is the main separator between the different tissue types (indicated by left and right arrows) and are represented on the x-axis, while the y-axis represents the variable importance on the projection (VIP) score for each mass. VIP > 1 for a variable is considered an important influence on the model and is indicated as a red dotted line. For visual purposes, the loading scores in a have been reversed. Identified metabolites and lipids are shown as blue and green circles, respectively. ACho = acetylcholine, ADP = adenosine diphosphate, AMP = adenosine monophosphate, ATP = adenosine triphosphate, BCt = butyryl-L-carnitine, GPE = glycerophoshpoethanolamine, HBCt = hydroxybutyrylcarnitine, NAA = N-acetylaspartate, LPC = lysophosphatidylcholines, PCho = phosphocholine, PE = phosphoethanolamines, PE = phosphatidylethanolamines, PC = phosphatidylcholines, PG = phosphatidylglycerols, PI = phosphatidylinositols, PS = phosphatidylserine, and SM = sphingomyelin. The particular phospholipids and their chain-composition can be identified by the number and found in Supplementary Table S4