Fig 1.

Identification of a compound with 1.9-fold elevated levels in prediagnostic lung cancer sera as N¹,N¹²-diacetylspermine (DAS). (A) Relative intensity of DAS (originally an unknown with mass-to-charge ratio [m/z] of 287.2437) in metabolomics data in prediagnostic lung cancer versus matched controls. Bars indicate mean and standard deviation. (B) Chemical structure of DAS. (C) Top panel shows total ion chromatogram of serum from a participant later diagnosed with lung cancer, showing peaks for (1) creatinine, (2) diacyl lipids, (3) lysophosphatidylcholine lipids, (4) acetylcarnitine, and (5) carnitine. Gradient profile is indicated in red. Extracted ion chromatogram for DAS (m/z, 287.24) in serum from a participant later diagnosed with lung cancer (middle panel) and for synthetic DAS (bottom panel). (D) Quadruple time-of-flight (QTOF) collision-induced dissociation (tandem mass spectrometry [MS/MS]) at 20 V of the unknown ion (m/z, 287.24) isolated from prediagnostic lung cancer serum (top panel) and QTOF MS/MS at 20 V of synthetic DAS (bottom panel).