Our results show that glutathione and cysteine in the host circulation are used by MCA sarcomas. The significant reduction in tumor utilization of serum glutathione after treatment with AT-125, a GGTP inhibitor, indicates that GGTP is important in tumor glutathione metabolism.

In extremity soft tissue sarcoma, glutathione concentration and GGTP activity are significantly elevated in patients with high-grade and metastatic sarcomas. In addition, there is a trend for increased glutathione levels in tumors previously exposed to doxorubicin-based chemotherapy. Glutathione may play a role in soft tissue sarcoma chemoresistance.