Abstract 368: Validation of reliable assay methods for glutathione quantitation and glutathione s-transferase activity in cancer patients
Citation: European Journal of Cancer Vol 38, Suppl. 7, November 2002, page 109
E. Ferruzzi1, R. Franceschini1, G. Cazzolato2, C. Geroni3, C. Fowst4, N. Tradati5, U. Pastorino6, J. Tursi4, R. Dittadi1, M. Gion1
1Venice General Hospital, Regional Centre of Biological Markers, Venice, Italy; 2Venice General Hospital, "P.Avogaro" Laboratory - Regional Centre for the St, Venice, Italy; 3Pharmacia Corporation, Oncology - External Research, Nerviano (MI), Italy; 4Pharmacia Corporation, Clinical Oncology, Nerviano (MI), Italy; 5European Institute of Oncology, Thoracic Surgery, Milan, Italy; 6European Institute of Oncology, Head and Neck Surgery, Milan, Italy
Glutathione s-transferases (GST) are members of a superfamily of enzymes that catalyze the reaction of electrophilic compounds with glutathione (GSH) to form inactive conjugates. These enzymes are of great importance in cancer biology since their levels have been correlated with resistance to cytotoxic drugs such as alkylating agents, platinum compounds and anthracyclines. Conversely, recently has been published that a DNA minor groove binder is activated by the GST/GSH systems (Geroni et al, Cancer Res. 2002). GST distribution in cancer patients has been extensively investigated but mixed data have been reported. The objectives of this study were primarily to validate robust and reliable assays for GSH/GST detection, suitable for routine clinical use and to explore the correlation between blood and tissue levels for both. Matched blood and tissue samples (normal and malignant) from 52 cancer patients (NSCLC and SCCHN) were investigated. GSH concentration and GST activity were measured by an enzymatic assay. GST content was also analysed by HPLC. Moreover, since the existence of regions of tissue heterogeneity is well documented within the tumor, multiple samples from seven cancer specimens have been analysed. Data were evaluated for either intra- and inter-patient variability to verify whether GSH/GST exhibit heterogeneity in samples from different areas of the same specimen. Both GST activity and GSH levels were higher in cancer than in normal tissue. The difference was statistically significant in NSCLC (p=0.0004 and p=0.0002, respectively for GSH and GST) and borderline in SCCHN (p=0.03 and p=0.02, respectively for GSH and GST). Moreover GSH levels in whole blood showed a highly significant correlation with GST activity in matched cancer samples in both malignancies (p=0.003, r=0.53 in NSCLC, p<0.0001, r=0.89 in SCCHN). The strong correlation found between GST activity in cancer tissue and GSH level in whole blood indicates that GSH could have a clinical relevance as a surrogate marker of GST activity in tumor tissue and should be further investigated. However, tissue heterogeneity analysis suggested that GSH and GST levels could be linked to tissue variability in both normal and tumour tissues. Since statistical analysis indicates that heterogeneity is a true biological fact rather than an analytical artefact, it is recommended to have a larger sample of tumor tissue for GSH and GST biochemical analysis to confirm the validity of GSH as biomarker. |
