Cancer Res Treat.  2015 Jan;47(1):78-89. 10.4143/crt.2013.127.

Identification of Hypoxanthine and Phosphoenolpyruvic Acid as Serum Markers of Chemoradiotherapy Response in Locally Advanced Rectal Cancer

• Kim K
• Yeo SG
• Yoo BC

• KMID: 2380393
• DOI: http://doi.org/10.4143/crt.2013.127

Abstract

PURPOSE
Patients show variable responses to chemoradiotherapy (CRT), which is generally administered before surgery for locally advanced rectal cancer (LARC). The aim of this study was to identify molecular markers predictive of CRT responses by analysis of low-mass ions (LMIs) in serum of LARC patients.
MATERIALS AND METHODS
LMIs (< 1,000 m/z) in serum obtained before CRT from 73 LARC (cT3-4) patients were profiled using matrix-assisted laser desorption/ionization mass spectrometry. LMIs with higher weighting factors in discriminating CRT responses were selected using principal components analysis and discriminant analysis. Selected LMIs were identified using the Human Metabolome Database. The concentrations of identified LMIs were determined by colorimetric enzyme assay, and compared according to post-CRT pathological stage (ypStage) or Dworak's tumor regression grade (TRG).
RESULTS
The nine highest-ranking LMIs were selected. Among them, two LMIs with 137.08 and 169.04 m/z were identified as hypoxanthine (HX) and phosphoenolpyruvic acid (PEP), respectively. Higher HX concentration was observed in patients with ypStage 0-1 compared to ypStage 2-4 (p=0.034) or ypStage 3-4 (p=0.030); a similar difference was observed between TRG 4-3 and TRG 1 (p=0.035). HX > 16.0 muM showed significant association with ypStage 0-1 or TRG 4-3 than ypStage 3-4 (p=0.009) or TRG 1 (p=0.024), respectively. In contrast, a significantly lower concentration of PEP was observed in TRG 4-3 compared with TRG 2-1 (p=0.012).
CONCLUSION
Findings of this study demonstrated that serum concentrations of HX and PEP, identified using LMI profiling, may be useful for predicting the CRT response of LARC patients before treatment.

Keyword

Metabolite; Hypoxanthine; Phosphoenolpyruvate; Rectal neoplasms; Chemoradiotherapy; Low-mass ions

MeSH Terms

Biological Markers*
Chemoradiotherapy*
Enzyme Assays
Humans
Hypoxanthine*
Ions
Mass Spectrometry
Metabolome
Phosphoenolpyruvate
Rectal Neoplasms*
Biological Markers
Hypoxanthine
Ions
Phosphoenolpyruvate

Figure

• 

  Fig. 1. Principal components analysis and discriminant analysis (PCA-DA) of low-mass-ions (LMIs). Sera from rectal cancer patients were divided into five classifications according to their chemoradiotherapy (CRT) responses. Chloroform/methanol extracts of sera were analyzed by matrix assisted laser desorption/ionization-mass spectrometry. Information (i.e., massto-charge [m/z] and mass peak intensity) on LMIs in the mass spectra was used for PCA-DA. Left panels (A-E) show the results of PCA-DA in each CRT response classification. Right panels (A-E) show the loading score (weighting factor) of each individual LMI in the five classifications. TRG, tumor regression grade.

• 

  Fig. 2. Identification of low-mass-ions (LMIs) linked to the chemoradiotherapy (CRT) response in rectal cancer patients. (A) Nine LMIs were selected by principal components analysis and discriminant analysis as candidate metabolites significantly linked to the CRT response classification, and the classifications linked to each LMI are indicated as a yellow box. No single LMI was linked to all five classifications. (B) Response (normalized peak intensities) of LMIs with 137.05 and 169.04 m/z according to CRT responses. The response of LMIs with 137.05 m/z was higher in ypStage 0-1 compared to that of ypStage2-4 (classification II) or 3-4 (classification IV). LMIs with 169.04 m/z showed a lower response in ypStage 0 and tumor regression grade (TRG) 4-3 compared to that of ypStage1-4 (classification I) and TRG 2-1 (classification III), respectively. (C) Candidate metabolites with 137.07±0.05 and 169.04±0.05 m/z in a positivemode mass detection. The Human Metabolome Database was searched for identification of hypoxanthine and phosphoenolpyruvic acid as metabolites with 137.07±0.05 and 169.04±0.05 m/z, respectively.

• 

  Fig. 3. Box plot showing the levels of hypoxanthine (HX) and xanthine (X) according to pathological chemoradiotherapy responses (A-E). Significantly higher levels of HX (left panel) and its oxidative product, X (right panel), were observed in ypStage 0-1 than in ypStage2-4 (B) or 3-4 (D). This significant increase was also observed in tumor regression grade (TRG) 4-3 compared to TRG 1 (E).

• 

  Fig. 4. Box plot showing the levels of phosphoenolpyruvic acid (PEP) according to pathological chemoradiotherapy response (A-E). Significantly lower levels of PEP were observed in tumor regression grade (TRG) 4-3 than in TRG 2-1 (C), and the difference between the PEP levels ypStage 0 and ypStage 1-4 was marginally significant (A).

Reference

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