The Bcl-2 Homology Domain 3 Mimetic Gossypol Induces Both Beclin 1-dependent and Beclin 1-independent Cytoprotective Autophagy in Cancer Cells*

[Guest guest]

BlankThe Bcl-2 Homology Domain 3 Mimetic Gossypol Induces Both Beclin

1-dependent and Beclin 1-independent Cytoprotective Autophagy in Cancer Cells*

1.. Ping Gao‡§,

2.. Chantal Bauvy¶,

3.. Sylvie Souquère?,

4.. Giovanni Tonelli¶,

5.. Lei Liu‡,

6.. Yushan Zhu**,

7.. Zhenzhen Qiao**,

8.. a Bakula‡‡,

9.. Tassula Proikas-Cezanne‡‡,

10.. Gérard Pierron?,

11.. Patrice Codogno¶,

12.. Quan Chen‡‡‡,1 and

13.. am Mehrpour¶,2

+ Author Affiliations

1.. From the ‡Joint Laboratory of Apoptosis and Cancer Biology, The State Key

Laboratory of Biomembrane and Membrane Biotechnology, Chinese Academy of

Sciences, Beijing 100101, China,

2.. ¶INSERM U984, Université Paris-Sud, F-92296 Chatenay Malabry, France,

3.. ?CNRS-UPR, Institut André Lwoff, Laboratorie de Réplication de l'Acide

Désoxyribonucléique et Ultrastructure du Noyau, Villejuif, France,

4.. the ‡‡Autophagy Laboratory, Department of Molecular Biology, Institute for

Cell Biology, University of Tübingen, Tübingen, Germany,

5.. the §Graduate School of the Chinese Academy of Sciences, Beijing 100049,

China, and

6.. the **College of Life Sciences, Nankai University, Tinajin 30007, China

1.. 1 To whom correspondence may be addressed: The Laboratory of Apoptosis and

Cancer Biology, IOZ, Chinese Academy of Sciences, Beijing 100101, China. Tel.:

86-10-6480-7321; E-mail: chenq@....

2.. 2 To whom correspondence may be addressed: INSERM U984, Faculté de

Pharmacie, Université Paris-Sud, 5 rue Baptiste Clément, 92296 Chatenay

Malabry, France. Tel.: 336-63-43-15-62; Fax: 331-46-83-58-44; E-mail:

mehrpourmaryam@....

Abstract

Gossypol, a natural Bcl-2 homology domain 3 mimetic compound isolated from

cottonseeds, is currently being evaluated in clinical trials. Here, we provide

evidence that gossypol induces autophagy followed by apoptotic cell death in

both the MCF-7 human breast adenocarcinoma and HeLa cell lines. We first show

that knockdown of the Bcl-2 homology domain 3-only protein Beclin 1 reduces

gossypol-induced autophagy in MCF-7 cells, but not in HeLa cells. Gossypol

inhibits the interaction between Beclin 1 and Bcl-2 (B-cell leukemia/lymphoma

2), antagonizes the inhibition of autophagy by Bcl-2, and hence stimulates

autophagy. We then show that knockdown of Vps34 reduces gossypol-induced

autophagy in both cell lines, and consistent with this, the phosphatidylinositol

3-phosphate-binding protein WIPI-1 is recruited to autophagosomal membranes.

Further, Atg5 knockdown also reduces gossypol-mediated autophagy. We conclude

that gossypol induces autophagy in both a canonical and a noncanonical manner.

Notably, we found that gossypol-mediated apoptotic cell death was potentiated by

treatment with the autophagy inhibitor wortmannin or with small interfering RNA

against essential autophagy genes (Vps34, Beclin 1, and Atg5). Our findings

support the notion that gossypol-induced autophagy is cytoprotective and not

part of the cell death process induced by this compound.