Tissue amino acid profiles are characteristic of tumor type, malignant phenotype, and tumor progression in pancreatic tumors

Abstract

Tissue amino acid profiles depend on the cell types and extracellular components that constitute the tissue, and their functions and activities. We aimed to characterize the tissue amino acid profiles in several types of pancreatic tumors and lesions. We examined tissue amino acid profiles in 311 patients with pancreatic tumors or lesions. We used newly developed LC-MS/MS methods to obtain the profiles, which were compared with clinicopathological data. Each tumor or lesion presented a characteristic tissue amino acid profile. Certain amino acids were markedly altered during the multistep pancreatic carcinogenesis and pancreatic ductal adenocarcinoma (PDAC) progression. A tissue amino acid index (TAAI) was developed based on the amino acids that were notably changed during both carcinogenesis and cancer progression. Univariate and multivariate survival analyses revealed that PDAC patients with a high TAAI exhibited a significantly shorter survival rate, and these findings were validated using a second cohort. We suggest that tissue amino acid profiles are characteristic for normal tissue type, tumor histological type, and pathological lesion, and are representative of the cancer grade or progression stage in multistep carcinogenesis and of malignant characteristics. The TAAI could serve as an independent prognosticator for patients with PDAC.

Figure 1

Characteristics of amino acid profile in normal and pancreatic cancer tissues. (a) Scheme of sample analysis. (b) Radar charts of amino acid concentration ratios in normal tissues, including liver, duodenum, colon, and pancreas. Data represent median of amino acid concentration ratios in each tissue type. (c) Ratio of amino acid concentrations in normal tissues and PDAC. Values are median + quartile range. *, **, ***, ****: P < 0.05, 0.01, 0.001, 0.0001 (Steel comparison test, versus normal pancreas). (d) Differences in amino acid concentrations between normal and diseased pancreatic tissues. *, **, ***, ****: P < 0.05, 0.01, 0.001.

Figure 2

Amino acid profiles of normal and diseased pancreatic tissues. (a) Radar charts of standardized amino acid profiles of normal and diseased pancreatic tissues from chronic pancreatitis (CP), intraductal papillary-mucinous neoplasm (IPMN), IPMN associated with invasive carcinoma (IPMC-IC), pancreatic ductal adenocarcinoma (PDAC), anaplastic carcinoma (ANA), acinar cell carcinoma (ACC), neuroendocrine tumor (NET) and solid-pseudopapillary neoplasm (SPN). Data shown are medians of z-scores calculated from the values of amino acid concentration ratios in each tissue type. (b) Hierarchical cluster analysis of median amino acid concentration ratios in each tissue type. (c) Three-dimensional scatter plots of PCA scores for each tissue.

Figure 3

The direct relation between tissue amino acid concentration and tissue components. Path analysis (multiple regression analysis) is performed using N (n = 7), CP (n = 10), and PDAC (n = 53). The direct relationship between tissue components and amino acid concentration is represented by means of low diagram. R² (coefficient of determination) is adjusted r-squared that the model explains all the variability of the response data around its mean. Path coefficients (standard partial regression coefficients) estimate the strength of the relationship between two variables. Tissue occupancy of each tissue component [Acn: Bcl-10 (331.3)⁺ acinar cells, Islet: Chromogranin A (CGA)⁺ islet cells, Duct: EMA⁺ or Cytokeratin (CK, AE1/AE3)⁺/Bcl-10⁻/CGA⁻ ductal epithelial cells in non-cancerous tissue, Mac: CD45⁺/CD68⁺ macrophages, Lym: CD45⁺/CD68⁻ lymphocytes, PDAC: EMA⁺ or CK⁺/Bcl-10⁻/CGA⁻ cancer cells, Fib: aniline blue⁺ area, Fat: SudanIII⁺ fat cells] is counted as the ratio of its area within the total area. Fib is omitted in calculation for inhibiting multicollinearity. ^∆, *, **, ***: P < 0.10, 0.05, 0.01, 0.001. For example, the tissue concentration of Thr is directly and significantly correlated with the volume of Acn positively and with the volume of Islet negatively. Their standard partial regression coefficients are 0.63 and −0.30, respectively. The R² (coefficient of determination) is 0.51, meaning 51% of the tissue Thr concentration is affected by these factors, Acn and Islet.

Figure 4

Changes in tissue amino acid concentrations during progression of pancreatic carcinogenesis. (a,b) Amino acids altered during the progression of multistep pancreatic carcinogenesis in (a), intraductal papillary-mucinous neoplasm (IPMN) with low grade dysplasia, alternatively intraductal papillary-mucinous adenoma (IPMA), IPMN with high grade dysplasia, alternatively intraductal papillary-mucinous carcinoma (IPMC), IPMN associated with invasive carcinoma (IPMC-IC), and pancreatic ductal adenocarcinoma (PDAC), and PDAC of various grades in (b). Box plots of amino acid concentration ratios are shown. (c) Kaplan-Meier survival curves showing comparison of overall survival (left panel) and disease-free survival (right panel) between high (red) and low (blue) of tissue amino acid index (TAAI) groups in cohort 1. P values were obtained from log-rank tests. The “×” and “+” represent censoring and failure, respectively.