Abstract 220: 14-3-3 zeta downregulation sensitizes head and neck cancer cells to chemotherapeutic agents

Abstract

Abstract Introduction. Advancements in treatment modalities have not translated into marked improvement in the prognosis of Head and Neck squamous cell carcinoma (HNSCC) patients. Major emphasis is being laid on designing new therapeutic strategies for more effective disease management. Recently, using iTRAQ-labeling and liquid chromatography-mass spectrometry (MS), we identified a panel of biomarkers, including 14-3-3 zeta and 14-3-3 sigma in HNSCC and oral pre-malignant lesions. Retrospective study of HNSCC revealed correlation of increased expression of both these biomarkers with poor disease prognosis. Herein, we report preliminary results on determining the potential of 14-3-3 zeta as a molecular target for HNSCC therapy. Methods. Small interfering RNA (siRNA) targeting 14-3-3 zeta was used to down-regulate its expression in head and neck cancer cell lines (SCC4 / HSC2). Transient transfection of siRNAs targeting 14-3-3 zeta in these cultured cells was done using LipofectAMINE 2000. The chemosensitivity of transfected cells was determined by measuring the cell death using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Flow cytometry-based cell cycle analysis, Annexin V dye binding assay and TUNEL assay. Results: Knockdown of 14-3-3 zeta showed reduced cell viability and G2/M arrest in head and neck cancer cells transfected with 14-3-3 zeta siRNA (100 nM, 48 hours). Importantly, doxorubicin / cisplatin treatment of 14-3-3 zeta siRNA transfected head and neck cancer cells (SCC4 / HSC2), showed increased cell death at lower doses in comparison to cells treated with doxorubicin or cisplatin alone. Increased sub-G0 phase was observed in SCC4 cells (showing reduced 14-3-3 zeta expression) on treatment with any of these chemotherapeutic agents. Annexin V staining and TUNEL assay revealed increased apoptosis. Western blot analysis showed cleaved caspase 9 and caspase 3, confirming the induction of apoptosis. Conclusions: Our results showed that 14-3-3 zeta downregulation sensitizes head and neck cancer cells to chemotherapeutic agents by induction of apoptosis. We propose that down-regulation of 14-3-3 zeta may serve as a novel strategy to improve the efficacy of chemotherapeutic agents in the management of head and neck cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 220.