Abstract A31: Induction of autophagy's mechanism in laryngeal squamous cancer cells by Trisenox.

Abstract

Abstract Introduction: A major problem in cancer treatment is the development of resistance to multiple chemotherapeutic agents. Laryngeal cancer is one of the most common worldwide malignancies of head and neck. Despite extensive research into molecular changes in laryngeal carcinogenesis, reliable molecular markers with predictive and prognostic value are still lacking. Trisenox is indicated for induction of remission and consolidation in patients with acute promyelocytic leukemia (APL), but is not applied at the clinical practice yet. However, many studies have demonstrated their effects in solid tumors. Among the numerous mechanisms implicated in chemoresistance, glutathione (GSH) and associated enzymes play a pivotal function in hematopoietic and solid tumors. Several studies report that depletion of GSH by L-buthionine-sulfoximine (BSO) sensitizes tumor cells to chemotherapeutic-ROS inducers such as Cisplatin and Trisenox. Our previous studies showed the combination of Trisenox and BSO, an important GSH-inhibitor, was synergistic and reduced the Laryngeal Squamous Carcinoma Cell line Hep-2 cell viability up to 60%. However, the mechanism of Trisenox-death induction is poorly understood. Here we investigated the pathway involved in the cytotoxic effect mediated by the combined BSO and Trisenox treatment in Hep-2 lineage. Materials and Methods: The Laryngeal Squamous Carcinoma Cell line Hep-2 were maintained in RPMI culture medium and previously incubated with BSO. After 24h, the cells were treated with 1.0 and 4.0μM Trisenox for 72h. Acridine Orange assay was used through flow cytometer and imunnofluorescence to evidence the autophagic vacuoles. To evaluate the autophagic induction, we used 3-Metil-Adenine (3-MA), a known autophagy-inhibitor, in combination with Trisenox and BSO. Results: We observed that the BSO potentiates the Trisenox-autophagic induced acid vesicules formation assessed by acridine orange in both flow cytometer and immunofluorescence assays. In addition, previous treatment with 3-MA inhibited up to 20% of the cytotoxic effect of 1.0 and 4.0μM Trisenox. Conclusion: This study showed that BSO enhances the Trisenox-cytotoxic effects in laryngeal tumor cells through autophagic mechanisms. Trisenox might represent an attractive basis for laryngeal squamous cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A31.