Open Access Research article

14-3-3 zeta is a molecular target in guggulsterone induced apoptosis in Head and Neck cancer cells

Muzafar A Macha1, Ajay Matta2, SS Chauhan1, KW Michael Siu2 and Ranju Ralhan234567*

Author Affiliations

1 Department of Biochemistry, All India Institute of Medical Sciences, New Delhi-110029, India

2 Department of Chemistry and Centre for Research In Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3

3 Department of Chemistry and Centre for Research In Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3

4 Joseph and Mildred Sonshine Family Centre for Head and Neck Diseases and Department of Otolaryngology - Head and Neck Surgery, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario, Canada M5G 1X5

5 Alex and Simona Shnaider Laboratory of Molecular Oncology, Mount Sinai Hospital, Toronto, Ontario, Canada, M5G 1X5

6 Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada, M5G 1X5

7 Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Toronto, Ontario, Canada M5G 2N2

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BMC Cancer 2010, 10:655  doi:10.1186/1471-2407-10-655

Published: 30 November 2010

Abstract

Background

The five-year survival rates for head and neck squamous cell carcinoma (HNSCC) patients are less than 50%, and the prognosis has not improved, despite advancements in standard multi-modality therapies. Hence major emphasis is being laid on identification of novel molecular targets and development of multi-targeted therapies. 14-3-3 zeta, a multifunctional phospho-serine/phospho-threonine binding protein, is emerging as an effector of pro-survival signaling by binding to several proteins involved in apoptosis (Bad, FKHRL1 and ASK1) and may serve as an appropriate target for head and neck cancer therapy. Herein, we determined effect of guggulsterone (GS), a farnesoid X receptor antagonist, on 14-3-3 zeta associated molecular pathways for abrogation of apoptosis in head and neck cancer cells.

Methods

Head and neck cancer cells were treated with guggulsterone (GS). Effect of GS-treatment was evaluated using cell viability (MTT) assay and apoptosis was verified by annexin V, DNA fragmentation and M30 CytoDeath antibody assay. Mechanism of GS-induced apoptosis was determined by western blotting and co-IP assays using specific antibodies.

Results

Using in vitro models of head and neck cancer, we showed 14-3-3 zeta as a key player regulating apoptosis in GS treated SCC4 cells. Treatment with GS releases BAD from the inhibitory action of 14-3-3 zeta in proliferating HNSCC cells by activating protein phosphatase 2A (PP2A). These events initiate the intrinsic mitochondrial pathway of apoptosis, as revealed by increased levels of cytochrome c in cytoplasmic extracts of GS-treated SCC4 cells. In addition, GS treatment significantly reduced the expression of anti-apoptotic proteins, Bcl-2, xIAP, Mcl1, survivin, cyclin D1 and c-myc, thus committing cells to apoptosis. These events were followed by activation of caspase 9, caspase 8 and caspase 3 leading to cleavage of its downstream target, poly-ADP-ribose phosphate (PARP).

Conclusion

GS targets 14-3-3 zeta associated cellular pathways for reducing proliferation and inducing apoptosis in head and neck cancer cells, warranting its investigation for use in treatment of head and neck cancer.