(P 185) PHARMACOLOGICAL INHIBITION OF GLYOXALASE-1 AS NOVEL THERAPEUTIC STRATEGY TO POTENTIATE TRABECTEDIN ANTI-TUMOR EFFECT IN SOFT TISSUE SARCOMA PRECLINICAL MODELS

Objective: Trabectedin is a marine anticancer agent that induces long-lasting objective remissions and tumor control in about 20% of patients with pretreated/resistant soft-tissue sarcoma (STS). Thus, the identification of novel therapeutic strategies to increase trabectedin efficacy is an unmet clinical need. We performed an in silico analysis using two public datasets (GSEA M5190 and TCGA SARC) to identify genes that were modulated by trabectedin exposure in several STS cell lines and, simultaneously, associated with prognosis in STS patients (Figure 1). Among the potential targets, glyoxalase-1 (Glo1) was the only druggable by the already available compound S-p-bromobenzylglutathione cyclopentyl diester (BBGC) also suitable for in vivo use. Previous evidences reported the anti-tumor activity of BBGC able to repress specifically Glo1-overexpressing human tumors.

Methods: The effect of trabectedin, doxorubicin and gemcitabine, alone or in combination with BBGC, was evaluated on HT1080 fibrosarcoma cell line, SW872 liposarcoma cell line, SK-LMS-1 leiomyosarcoma cell line and 402-91 WT/ET myxoid-liposarcoma cell lines sensitive and resistant trabectedin, respectively, by MTT viability assay. Synergy analysis was calculated using SynergyFinder web application (version 3.0). Apoptosis was analyzed by flow cytometry using Annexin V antibody and propidium iodide. HT-1080 fibrosarcoma orthotopic murine model was obtained injecting 1x107 HT-1080 cells into gastroecnemius muscle of athymic nude-foxn1 nu/nu (female).

Results: Data showed a strong synergistic effect between trabectedin and BBGC in HT1080, SW872 and SK-LMS-1 cell lines (Synergy score HT1080: 30.395; Synergy score SW872: 57.318; Synergy score SK-LMS-1: 38.058) (Figure 2). Intriguingly, in 402-91 trabectedin resistent cells characterized by higher Glo-1 protein levels compared to sensitive cells, we found an increased synergist effect (Synergy score 402-91 ET: 37.218; Synergy score 402-91 WT: 13.662) in terms of cell viability and apoptosis (Figure 3). This strong synergistic effect was not observed using BBGC in combination with doxorubicin or gemcitabine across the STS cell lines tested (Figure 2) suggesting a potential direct involvement of Glo1 in trabectedin acquired resistance mechanisms. Confirmatory results were obtained in in vivo murine models where the combination BBGC (200mg/kg) with trabectedin (0.1mg/kg) significantly increased the antitumor effect as compared with tractedin as single agent (p ≤0.014, from Day 2 to 7; p ≤0.001, from Day 14 to 16) (Figure 4).

Conclusion: Our results identify a new potential target to potentiate the efficacy of trabectedin and potentially overcome resistance mechanism. The availability of the specific Glo-1 inhibitor, BBGC, could accelerate its potential translational in clinical practice.

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