Abstract 2868: Use of methionine metabolites in predicting recurrent prostate cancer affordably
Authors: Choudhury Diptiman , Haldar Subhash , Bhowmick Neil A. 
Published: May 2015

Abstract
Prostate cancer is often an over-treated disease due to our inability to distinguish its indolent & aggressive manifestations. Aggressive prostate cancer is characterized by its ability to survive & proliferate at hypoxic & nutrient deficient conditions in local or distant sites of metastasis. Metastatic progression is associated with recurrent disease following local therapeutic intervention. Cancer cells can utilize sulfur as terminal electron acceptor instead of oxygen in the generation of ATP under anaerobic conditions. Accordingly, we have previously demonstrated that patients with recurrent prostate cancer following prostatectomy have elevated sulfur containing amino acids, homocysteine (p value = 0.003), cystathionine (p value = 0.04), & cysteine (p value &lt; 0.0001), detectable in serum. Gleason grade & clinical stage of the recurrent & non-recurrent patients were not statistically (n = 58). A primary lack of diagnostic use of these factors lies in its high cost & difficulty for high throughput analysis. We have developed a unique technique to convert & detect the three biomarkers as a single end product. Since, the level of all this individual type of amino acids is elevated in recurrent disease, the conversion of homocysteine & cystathionine to cysteine can be achieved by ex vivo incubation with cystathionine beta syntheses (CBS) & cystathionine gamma lyase (CGL), respectively. We achieved &gt; 80% enzyme conversion of homocysteine & cystathionine. Helicobacter pylori CBS & CGL had been cloned & expressed in E. coli after codon optimization & purified using N-terminal cellulose binding domain (Clostridium thermocellum). Following incubation, samples were filtered & incubated with polymer-coated gold-nanorods & Cu2+ at room temperature. Subsequent absorption spectrum analysis demonstrated a sharp red-shift of longitudinal plasmon peaks in a concentration linearly dependent on the concentration of free cysteine (0 - 100 µM; R2 &gt; 0.94). The plasmon peak shift took place due to end to joining of gold-nanorods resulting formation of linear chains, validated by transmission electron microscopic visualization. The translation of the method of our findings was determined by measuring cysteine in mice xenografted with metastatic prostate tumors. Cysteine measurements were correlated to tumor progression by longitudinal monitoring of luciferase labeled tumor (ARCAPM) bioluminescent detection. Finally, 60 annotated serum samples of prostate cancer patients were analyzed retrospectively. The serum was collected prior to prostatectomy & outcomes followed up to five years following prostatectomy. Biochemically recurrent & non-recurrent subjects were successfully distinguished using this modified gold nano-rod technique. The advantages of this system over the existing methods include: its adaptability to high throughput analysis, economical, minimal sample requirement (∼200 µl), & reduced technical complexity.
Citation Format: Diptiman Choudhury, Subhash Haldar, Neil A. Bhowmick. Use of methionine metabolites in predicting recurrent prostate cancer affordably. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2868. doi:10.1158/1538-7445.AM2014-2868