Integrated Ionization Approach for RRLC−MS/MS-based Metabonomics: Finding Potential Biomarkers for Lung Cancer

Abstract

An integrated ionization approach of electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) combining with rapid resolution liquid chromatography mass spectrometry (RRLC-MS) has been developed for performing global metabonomic analysis on complex biological samples. This approach was designed to overcome the low ionization efficiencies of endogenous metabolites due to diverse physicochemical properties as well as ion suppression, and obtain comprehensive metabolite profiles in LC-MS analysis. Ionization capability and applicability were manifested by improved ionization efficiency and enlarged metabolite coverage in analysis on typical urinary metabolite standards and urine samples from healthy volunteers. The method was validated by the limit of detection and precision. When applied to the global metabonomic studies of lung cancer, more comprehensive biomarker candidates were obtained to reflect metabolic traits between healthy volunteers and lung cancer patients, including 74 potential biomarkers in positive ion mode and 59 in negative ion mode. Taking identical potential biomarkers of any two or three ionization methods into account, analysis using ESI-MS in positive (+) and negative (-) ion mode contributed to 70 and 64% of the total potential biomarkers, respectively. The biomarker discovery capability of (+/-) APCI-MS accounted for 45 and 42% of the overall; meanwhile (+/-) APPI-MS amounted for 39 and 54%. These results indicated that potential biomarkers with vital biological information could be missed if only a single ionization method was used. Furthermore, 11 potential biomarkers were identified including amino acids, nucleosides, and a metabolite of indole. They revealed elevated amino acid and nucleoside metabolism as well as protein degradation in lung cancer patients. This proposed approach provided a more comprehensive picture of the metabolic changes and further verified identical biomarkers that were obtained simultaneously using different ionization methods.

Urinary metabolomic study of non‐small cell lung carcinoma based on ultra high performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry

“…Taurine, hippuric acid, and carnitine were included in HMDB database as lung cancer-related biomarkers and were also reported by Yang et al [26]. Tyrosine was reported as potential biomarker of lung cancer by An et al [27] and its phosphorylated derivative was also found in our work. Uric acid concentration was found upregulated in urine samples from cancer group.…”

UPLC-based metabonomic applications for discovering biomarkers of diseases in clinical chemistry

“…Eleven potential biomarkers including amino acids, nucleosides and indole were identified. The study revealed elevated amino acid and nucleoside metabolism as well as protein degradation in patients with lung cancer [55]. Previous studies indicated increased urinary aromatic amino acids that might be caused by derangement of protein metabolism in cancer patients [56].…”

Metabolomics for tumor marker discovery and identification based on chromatography–mass spectrometry

“…Review MS-based metabolomic platforms are increasingly applied to the screening of tumor markers and have been used in recent years for colorectal cancer [39][40][41][42][43][44][45][46], lung cancer [47][48][49][50][51][52][53], papillary thyroid carcinoma [54], oral cancer [55,56] and pancreatic cancer [57]. Here, due to space limitations, the authors review the development of metabolomics in the discovery of tumor markers only for specific malignancies with high incidence, including primary liver cancer, gynecologic cancer and genitourinary cancer.…”