Quantitative analysis of prostate metabolites using ¹H HR‐MAS spectroscopy

Abstract

A method was developed to quantify prostate metabolite concentrations using (1)H high-resolution magic angle spinning (HR-MAS) spectroscopy. T(1) and T(2) relaxation times (in milliseconds) were determined for the major prostate metabolites and an internal TSP standard, and used to optimize the acquisition and repetition times (TRs) at 11.7 T. At 1 degrees C, polyamines (PAs; T(1mean) = 100 +/- 13, T(2mean) = 30.8 +/- 7.4) and citrate (Cit; T(1mean) = 237 +/- 39, T(2mean) = 68.1 +/- 8.2) demonstrated the shortest relaxation times, while taurine (Tau; T(1mean) = 636 +/- 78, T(2mean) = 331 +/- 71) and choline (Cho; T(1mean) = 608 +/- 60, T(2mean) = 393 +/- 81) demonstrated the longest relaxation times. Millimolal metabolite concentrations were calculated for 60 postsurgical tissues using metabolite and TSP peak areas, and the mass of tissue and TSP. Phosphocholine plus glycerophosphocholine (PC+GPC), total choline (tCho), lactate (Lac), and alanine (Ala) concentrations were higher in prostate cancer ([PC+GPC](mean) = 9.34 +/- 6.43, [tCho](mean) = 13.8 +/- 7.4, [Lac](mean) = 69.8 +/- 27.1, [Ala](mean) = 12.6 +/- 6.8) than in healthy glandular ([PC+GPC](mean) = 3.55 +/- 1.53, P < 0.01; [tCho](mean) = 7.06 +/- 2.36, P < 0.01; [Lac](mean) = 46.5 +/- 17.4, P < 0.01; [Ala](mean) = 8.63 +/- 4.91, P = 0.051) and healthy stromal tissues ([PC+GPC](mean) = 4.34 +/- 2.46, P < 0.01; [tCho](mean) = 7.04 +/- 3.10, P < 0.01; [Lac](mean) = 45.1 +/- 18.6, P < 0.01; [Ala](mean) = 6.80 +/- 2.95, P < 0.01), while Cit and PA concentrations were significantly higher in healthy glandular tissues ([Cit](mean) = 43.1 +/- 21.2, [PAs](mean) = 18.5 +/- 15.6) than in healthy stromal ([Cit](mean) = 16.1 +/- 5.6, P < 0.01; [PAs](mean) = 3.15 +/- 1.81, P < 0.01) and prostate cancer tissues ([Cit](mean) = 19.6 +/- 12.7, P < 0.01; [PAs](mean) = 5.28 +/- 5.44, P < 0.01). Serial spectra acquired over 12 hr indicated that the degradation of Cho-containing metabolites was minimized by acquiring HR-MAS data at 1 degree C compared to 20 degrees C.

Efforts to resolve the contradictions in early diagnosis of prostate cancer: a comparison of different algorithms of sarcosine in urine

“…3 With regard to the application of metabolomics in cancer diagnostics, PCa demonstrated a different metabolic profile characterized by high glycolytic products, total choline-containing compounds and phosphocholine levels. 21 In addition, prostatic fluid from men with PCa, exhibited reduced citrate and increased spermine levels, which correlated well with Gleason score, and outperformed PSA in cancer diagnosis. 22,23 Not limited to the field of PCa diagnosis, metabolomics is also providing essential information about tumorigenesis, cancer diagnosis in other tumors, cancer prognosis, therapeutic evaluation and revealing new therapeutic targets.…”

TE = 32 ms vs TE = 100 ms echo‐time 1H‐magnetic resonance spectroscopy in prostate cancer: Tumor metabolite depiction and absolute concentrations in tumors and adjacent tissues

“…(1), the metabolite concentration in normal tissue is from the matched prostate voxel, f is the tumor fraction of the voxel, and the metabolite concentration inside tumor is assumed to be 30% of that in the normal tissue 7…”

“…In ex vivo prostate tumor extracts the concentrations of metabolites from the glandular secretions (citrate and spermine) are reduced compared with normal prostate tissue, while that of the cell membrane precursor choline is increased 7. Unfortunately, quantifying metabolite signals from in vivo prostate spectra is challenging due to the inherently small signals present at clinical field strengths.…”

Citrate – new functions for an old metabolite

“…A ratio ≥ 0.86 is associated with a definite prostate cancer (Scheidler et al, 1999). Another technique, magic angle spinning nuclear magnetic resonance, is more sensitive in detecting significant decrease of citrate and polyamine levels directly in intact tissue (Swanson et al, 2006).…”