Abstract 4632: Probability of plasma amino acid concentration and its profile as a novel diagnostic marker for prostate cancer
Authors: Miyagi Yohei , Miura Takeshi , Moriyama Masatoshi , Ohta Junichi , Muramatsu Takahiko , Imaizumi Akira , Yamamoto Hiroshi , Yamakado Minoru , Okamoto Naoyuki 
Published: February 2011

Abstract
Introduction.
Although there is no doubt on a plausible significance of prostate-specific antigen (PSA) on prostate cancer (PCa) diagnosis and managements, PSA screening for cancer has several problems especially on (1) specificity to discriminate cancers from benign lesions such as hypertrophy or inflammation, and (2) sensitivity to some cancers which PSA production is low or missing. Under the present circumstances, combination of other biomarkers with PSA is a way to overcome these problems. On the other hand, plasma amino acid-concentration reflects metabolic status of the body. Although maintained in healthy humans, it is known to change in various pathologic conditions including liver dysfunction and cancers, and therefore one could speculate that the profile of the change could be a promising biomarker (“AminoIndex”) of various cancers. Additionally, recent advances in technologies enable us to easily evaluate plasma amino acid profiles of a great number of samples. In this study, the potential of plasma amino acid profiling for prostate cancer detection was investigated.
Subjects and Methods.
Plasma samples were collected from Japanese prostate cancer patients those were consulted to Kanagawa Cancer Center Hospital and Yokohama Municipal Citizens Hospital and finally diagnosed by histopathological examination of biopsy specimens. Those of Japanese healthy controls were collected from subjects who were undergone comprehensive medical examination at Mitsui Memorial Hospital. Plasma amino acid-concentrations were measured by LC-MS, and compared between PCa patients and healthy controls. A multivariate logistic regression function was applied to obtain the index to discriminate PCa patients from controls using changes of plasma amino acid-concentrations.
Results.
Plasma concentrations of several amino acids changed significantly in PCa patients compared to control subjects. In particular, plasma levels of proline, alanine, and asparagine were increased while those of valine, and tryptophan were decreased in PCa patients significantly. The predicted amino acid profile index (“AminoIndex”) composed with these significantly changed amino acids showed high discrimination performance between PCa patients and healthy controls with more than 70% of area under ROC curve. The obtained index discriminated both patients of poorly differentiated cancer and the early stage cancer from control, and was independent of both age and serum PSA level.
Conclusion and Perspectives.
In this study, we demonstrated that plasma amino acid profile was altered in prostate cancer patients and the calculated “AminoIndex” could be a novel promising tool for detection of prostate cancer. PCa screening by the “AminoIndex” in conjunction with PSA could be a promising way to decrease both false positive and false negative cases.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4632.