Targeting glutathione-S transferase enzymes in musculoskeletal sarcomas: a promising therapeutic strategy

Recent studies have indicated that targeting glutathione-S-transferase (GST) isoenzymes may be a promising novel strategy to improve the efficacy of conventional chemotherapy in the three most common musculoskeletal tumours: osteosarcoma, Ewing's sarcoma, and rhabdomyosarcoma. By using a panel of 15 drug-sensitive and drug-resistant human osteosarcoma, Ewing's sarcoma, and rhabdomyosarcoma cell lines, the efficay of the GST-targeting agent 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX) has been assessed and related to GST isoenzymes expression (namely GSTP1, GSTA1, GSTM1, and MGST). NBDHEX showed a relevant in vitro activity on all cell lines, including the drug-resistant ones and those with higher GSTs levels. The in vitro activity of NBDHEX was mostly related to cytostatic effects, with a less evident apoptotic induction. NBDHEX positively interacted with doxorubicin, vincristine, cisplatin but showed antagonistic effects with methotrexate. In vivo studies confirmed the cytostatic efficay of NBDHEX and its positive interaction with vincristine in Ewing's sarcoma cells, and also indicated a positive effect against the metastatisation of osteosarcoma cells. The whole body of evidence found in this study indicated that targeting GSTs in osteosarcoma, Ewing's sarcoma and rhabdomyosarcoma may be an interesting new therapeutic option, which can be considered for patients who are scarcely responsive to conventional regimens.

Modulation of the GSTT1 activity by the GSTM1 phenotype in a sample of Italian farm-workers

Glutathione S-transferase (GST) isozymes catalyze nucleophilic attack by reduced Glutathione (GSH) on a variety of electrophilic compounds and play a central role in biotransformation of xenobiotics (Hayes et al., Annu Rev Pharmacol Toxicol 45:51-88, 2005). We performed a case-control study to evaluate the GSTM1 and GSTT1 polymorphisms and to investigate if exposure to pesticides conditions the GSTT1 activity level in 115 healthy controls and 90 farm-workers exposed to pesticides. Polymorphisms were investigated using a GSTM1 or a GSTT1-specific PCR. Enzyme activity was measured by means of DCM as co-substrate, as described by Bruhn et al. (Biochem Pharmacol 56:1189-1193, 1998). There was no significant difference between the farm-workers and the healthy controls regarding the distribution of various alleles of the GSTM1 and GSTT1 genes and the GSTT1 enzyme activity. In farm-workers, the GSTM1 null genotype was associated with a significant increase of GSTT1 activity, suggesting a regulative mechanism common to GSTM1 and GSTT1 enzymes after exposure to xenobiotics.