Quantitative assay for six potential breast cancer biomarker peptides in human serum by liquid chromatography coupled to tandem mass spectrometry

Abstract: An assay to quantify several possible breast cancer peptide biomarkers in human serum has been developed and validated, using liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). The peptides include bradykinin, Hyp3-bradykinin, des-Arg9-bradykinin and fragments of fibrinogen α-chain (Fib-α[605–629]), inter-α-trypsin inhibitor heavy chain 4 (ITIH4[666–687]) and complement component 4a (C4a[1337–1350]). Ile13-ITIH4[666–687], d20-C4a[1337–1350] and Sar-D-Phe8-des-Arg9-bradykinin were used as internal standards. Bovine plasma, with 2mM captopril and 2mM d-l-mercaptoethanol-3-guanidino-ethylthiopropanoic acid (MEGETPA) to prevent rapid degradation of the bradykinins, was used as analyte-free matrix. Recoveries for solid-phase extraction (SPE) on mixed-mode weak cation exchange sorbents were between 62 and 90%. Multiple reaction monitoring (MRM) on a triple quadrupole mass spectrometer equipped with a heated electrospray source (H-ESI), operating in the positive ion-mode, was used for detection. The assay was fully validated and stabilities of the peptides were extensively explored. Bradykinin (10–500ng/ml), Hyp3-bradykinin (4–200ng/ml), des-Arg9-bradykinin (2–100ng/ml), Fib-α[605–629] (120–3000ng/ml), ITIH4[666–687] (0.4–10ng/ml) and C4a[1337–1350] (1–25ng/ml) were simultaneously quantified with deviations from the nominal concentrations below 22% and intra- and inter-assay precisions below 15 and 20%, respectively, for all peptides at all concentrations. The method has been successfully applied to several serum samples from breast cancer patients and matched controls. [Copyright &y& Elsevier]