Development of a Correlative Strategy To Discover Colorectal Tumor Tissue Derived Metabolite Biomarkers in Plasma Using Untargeted Metabolomics

Abstract

The metabolic profiling of biofluids using untargeted metabolomics provides a promising choice to discover metabolite biomarkers for clinical cancer diagnosis. However, metabolite biomarkers discovered in biofluids may not necessarily reflect the pathological status of tumor tissue, which makes these biomarkers difficult to reproduce. In this study, we developed a new analysis strategy by integrating the univariate and multivariate correlation analysis approach to discover tumor tissue derived (TTD) metabolites in plasma samples. Specifically, untargeted metabolomics was first used to profile a set of paired tissue and plasma samples from 34 colorectal cancer (CRC) patients. Next, univariate correlation analysis was used to select correlative metabolite pairs between tissue and plasma, and a random forest regression model was utilized to define 243 TTD metabolites in plasma samples. The TTD metabolites in CRC plasma were demonstrated to accurately reflect the pathological status of tumor tissue and have great potential for metabolite biomarker discovery. Accordingly, we conducted a clinical study using a set of 146 plasma samples from CRC patients and gender-matched polyp controls to discover metabolite biomarkers from TTD metabolites. As a result, eight metabolites were selected as potential biomarkers for CRC diagnosis with high sensitivity and specificity. For CRC patients after surgery, the survival risk score defined by metabolite biomarkers also performed well in predicting overall survival time (p = 0.022) and progression-free survival time (p = 0.002). In conclusion, we developed a new analysis strategy which effectively discovers tumor tissue related metabolite biomarkers in plasma for cancer diagnosis and prognosis.

Integrating Two-Dimensional Gas and Liquid Chromatography-Mass Spectrometry for Untargeted Colorectal Cancer Metabolomics: A Proof-of-Principle Study

“…In the past several years, a number of global metabolomic studies on CRC have been published. These studies utilized diverse biological specimens, including blood (plasma/serum) as the most common type [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ], followed by tissue [ 27 , 39 , 40 , 41 , 42 ], feces [ 39 , 40 , 43 ], and urine [ 44 , 45 ], while others aimed specifically to detect volatile metabolites in breath and in other types of biospecimens [ 21 , 46 ]. To our knowledge, only two of these were prospective studies where biospecimens were collected before cancer development [ 26 , 34 ], aiming to identify etiological pathways.…”

“…Because metabolic profiles are highly dependent on the choice of the matrix [ 27 ], the comparison across different types of biospecimens is not informative. Blood is the most widely used clinical specimens.…”

“…Each study applied heterogeneous criteria for differential abundance between cases and controls, yielding the number of differential metabolites ranging from 5 [ 30 ] to 72 [ 31 ]. More recently published studies identified nearly or over 600 named metabolites [ 26 , 28 ], while another recent paper reported a vast number of differentially present metabolites, i.e., 693, in plasma of CRC cases compared with polyp patients [ 27 ]. It should be noted that the number of annotated metabolites is affected by many factors, including sample treatments, bioanalytical platforms used for analysis, and the methods of data analysis.…”

“…Based on metabolic pathway analysis, we found five biological pathways were affected by disease history. Among these, alanine, aspartate, glutamate, and β-alanine metabolism pathways are also reported to be dysregulated in both CRC tissue and blood by others [ 25 , 27 , 41 , 43 ]. These two metabolic pathways and the TCA cycle are known to be central to fulfill increased energy consumption and increased anabolic activities to sustain cellular growth and proliferation [ 49 ].…”

“…Up-regulation of β-alanine metabolism pathway has been noted in both CRC tissue and plasma by Wang et al [ 27 ]. Besides CRC, increased β-alanine activity was positively associated with an aggressive type of estrogen receptor-negative breast cancer in both tumor tissues and established cell lines [ 50 , 51 ].…”