Detection of polyol accumulation in a new ovarian carcinoma cell line, CABA I: a(1)H NMR study

Abstract

Ovarian carcinomas represent a major form of gynaecological malignancies, whose treatment consists mainly of surgery and chemotherapy. Besides the difficulty of prognosis, therapy of ovarian carcinomas has reached scarce improvement, as a consequence of lack of efficacy and development of drug-resistance. The need of different biochemical and functional parameters has grown, in order to obtain a larger view on processes of biological and clinical significance. In this paper we report novel metabolic features detected in a series of different human ovary carcinoma lines, by (1)H NMR spectroscopy of intact cells and their extracts. Most importantly, a new ovarian adenocarcinoma line CABA I, showed strong signals in the spectral region between 3.5 and 4.0 p.p.m., assigned for the first time to the polyol sorbitol (39+/-11 nmol/10(6) cells). (13)C NMR analyses of these cells incubated with [1-(13)C]-D-glucose demonstrated labelled-sorbitol formation. The other ovarian carcinoma cell lines (OVCAR-3, IGROV 1, SK-OV-3 and OVCA432), showed, in the same spectral region, intense resonances from other metabolites: glutathione (up to 30 nmol/10(6) cells) and myo-inositol (up to 50 nmol/10(6) cells). Biochemical and biological functions are suggested for these compounds in human ovarian carcinoma cells, especially in relation to their possible role in cell detoxification mechanisms during tumour progression.

Figure 1

(A) ¹H NMR spectrum (400.1 MHz) of intact human ovarian carcinoma cells CABA I, with assignment of signals due to N⁺(CH₃)₃ from choline-containing compounds (‘Cho’-peak) and sorbitol; (B) expanded spectral ‘CH-region’ in CABA I cell extract; (C) sorbitol standard solution.

Figure 2

2D ¹H COSY experiment on intact CABA I cells. Some relevant cross-peak assignments are indicated. For further details see text.

Scheme 1

Biochemical reactions of glucose metabolising pathways

Figure 3

(A) ¹³C NMR spectrum (100.6 MHz) of ethanolic extract of CABA I cells, following incubation with [1-¹³C]-D-glucose; (B) 2D ¹H/¹³C HETCOR analysis of the same sample (expanded regions); the arrows indicate ¹H/¹³C cross-peaks from sorbitol.

Figure 4

Representative ¹H NMR spectra (400.1 MHz) of different intact human ovarian cancer cell lines with some peak assignments. N⁺(CH₃)₃ from choline-containing compounds (‘Cho’-peak); (CH₂)_n and CH₃ from mobile lipids.

Figure 5

¹H NMR spectra of ethanolic extracts of ovarian cancer cell lines. PCho=phosphocholine.

Figure 6

2D ¹H COSY experiments on intact SK-OV-3 cells. Some relevant cross-peak assignments are indicated. For further details see text.