Metabolomic characterization of ovarian tumors by ex vivo magnetic resonance spectroscopy
Feng-Hua Ma1, Jin-Wei Qiang2, Guo-Fu Zhang1, Ya-Min Rao3, Hai-Min Li4, and Song-Qi Cai4

1Department of Radiology, Obstetrics & Gynecology Hospital, Shanghai Medical College,Fudan University., Shanghai, China, People's Republic of, 2Department of Radiology, Jinshan Hospital, Shanghai Medical College,Fudan University, Shanghai, China, People's Republic of, 3Department of Radiology, Obstetrics& Gynecology Hospital, Shanghai Medical College, Fudan University, Shanghai, China, People's Republic of, 4Department of Radiology, Jinshan Hospital, Shanghai Medical College, Fudan University, Shanghai, China, People's Republic of

Synopsis

Coherent results obtained by ex vivo and in vivo measurements allow the translation of biomarker findings from studies of tissue specimens (ex vivo) to those of patients (in vivo), and therefore it is important to establish how well correlated these metabolic profiles are. Such correlation has been evaluated for brain tumors, prostate cancer and cervical cancer, but without comparison of ovarian tumors. In this study we try to investigate the relationship between the Cho/Cr from in vivo MRS and the Cho/TSP of ex vivo MRS from tissue samples and the potential to bridge molecular and imaging diagnostics.

Purpose: To investigate the feasibility of ex vivo proton magnetic resonance spectroscopy (ex vivo MRS) analysis of tumor specimens, and to evaluate the relationship between the techniques of in vivo MRS and ex vivo MRS for discriminating between different histological types of ovarian tumors.

Materials and methods: Two-hundred and fourty-two patients with surgically and histologically proven adnexal tumors underwent conventional MR imaging and 1H-MRS. Multi-voxel 2D-chemical shift imaging (CSI) was performed using the point resolved spectroscopy. Resonance peak integrals of choline (Cho), N-acetyl aspartate (NAA), creatine (Cr), lactate (Lac), and lipid (Lip) were analyzed and the Cho/Cr, NAA/Cr, Lac/Cr and Lip/Cr ratios were recorded. After surgery, thirty-eight ovarian tumor specimens were obtained and underwent ex vivo MRS. Ovarian tumor tissues (about 50 mg) were extracted using a tissue lyser (QIAGEN TissueLyser II, Germany). Supernatant for each sample was collected after 3 extracting procedures and each supernatant (550 μl) was transferred into a 5 mm NMR tube for ex vivo MRS analysis. All ex vivo spectra were acquired by a Bruker AVANCE III 600 MHz spectrometer and one 1H-spectrum was acquired with a standard NOESYGPPR1D pulse sequence. All the spectra were processed using the software package Mnova 5.3.1, including Fourier transform, phase correction, baseline correction, displaying the full spectrum of each sample (-5 ppm ~ 14 ppm). The spectral regions containing unwanted signals were discarded and the peak integrals of the metabolites in the remaining regions were recorded and compared to the referring integrals of the trimethylsilyl 2,2,3,3-tetradeuteropropionic acid (TSP). The peak integrals and relative concentration of different metabolites with TSP were compared using one-way ANOVA and the relationship between the in vivo Cho/Cr ratio and ex vivo tCho/TSP ratio was evaluated by Spearman correlation analysis.

Results: With the increases of malignancy, the retalative concentration of choline compounds (tCho), Taurine (Tau), myo-inositol (myo-Inos) also increased. Significant differences were found in tCho between any two groups and only found between benign and malignant tumors in Tau and myo-Inos (P＜0.05). The retalative concentration of β-Glucose (β-Glu) decreased in borderline and malignant tumors, and significant differences were found between benign and borderline tumors, between benign and malignant tumors (P=0.011，0.000，respectively). The relative concentration of Glycine (Gly), Alanine (Ala), Lactate+Threonine (Lac+Thr), N- acetyl aspartate (NAA) was highest in borderline tumors. Significant differences were found in Ala between any two groups and only found between benign and malignant tumors in Gly, Lac+Thr and NAA. There was no statistically significant difference between borderline and malignant tumors in Gly, Lac+Thr and NAA (P=0.134, 0.205, 0.256). With the increase of malignancy, the Cho/Cr ratio in in vivo MRS and the tCho/TSP ratio in ex vivo MRS showed a corresponding increase and a significant correlation (r=0.849) were found between in vivo and ex vivo metabolite ratio.

Conclusions: Ex vivo MRS can display biological metabolic characteristics of different pathological types of ovarian tumors and more types of metabolites were detected in ex vivo MRS than in vivo MRS. A significant correlation was found between the Cho/Cr ratio in in vivo MRS and the Cho/TSP ratio in ex vivo MRS of the same tumor.

Acknowledgements

No acknowledgement found.

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Figures

Figure 1 Comparison of the relative concentration of metabolites

Figure 2 Left ovarian thecacom tumors. Figure A-B is ex vivo spectra of 1.0 ~ 3.6 ppm from the extract specimens. Figure C is the amplificated spectrum of Cho (3.20 ppm). On both ex-vivo spectra (C) and in-vivo MRS (D), Cho peak showed no significantly increased (Cho/TSP=0.70, Cho/Cr=3.7).

Figure 3 Right ovarian high-grade serous carcinoma. Figure A-B is ex vivo spectra of 1.0 ~ 3.6 ppm from the extract specimens. On both ex-vivo spectra (C) and in-vivo MRS (D), Cho peak Cho peak were seen significantly increased ( Cho / TSP = 3.46, Cho / Cr = 9.52).

Figure 4 Right ovarian clear cell carcinoma. Figure A-B is ex vivo spectra of 1.0 ~ 3.6 ppm from the extract specimens. On both ex-vivo spectra (C) and in-vivo MRS (D), Cho peak Cho peak were seen significantly increased (Cho/TSP=3.46, Cho/Cr=13.10).

Figure 5 Scatter Plot of in vivo ratio of Cho/Cr and ex vivo ratio of Cho/TSP. A significant correlation were found between in vivo and ex vivo metabolite ratio. (r = 0.849, P = 0.000).



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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