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Small molecule inhibition of group I p21-activated kinases in breast cancer induces apoptosis and potentiates the activity of microtubule stabilizing agents

Ong, Christy C.; Gierke, Sarah; Pitt, Cameron; Sagolla, Meredith; Cheng, Christine K.; Zhou, Wei; Jubb, Adrian M.; Strickland, Laura; Schmidt, Maike; Duron, Sergio G.; Campbell, David A.; Zheng, Wei; Dehdashti, Seameen; Shen, Min; Yang, Nora; Behnke, Mark L/; Huang, Wenwei; McKew, John C; Chernoff, Jonathan; Forrest, William F.; Haverty, Peter M.; Chin, Suet-Feung; Rakha, Emad A.; Green, Andrew R.; Ellis, Ian O.; Caldas, Carlos; O�Brien, Thomas; Friedman, Lori S.; Koeppen, Hartmut; Rudolph, Joachim; Hoeflich, Klaus P.


Christy C. Ong

Sarah Gierke

Cameron Pitt

Meredith Sagolla

Christine K. Cheng

Wei Zhou

Adrian M. Jubb

Laura Strickland

Maike Schmidt

Sergio G. Duron

David A. Campbell

Wei Zheng

Seameen Dehdashti

Min Shen

Nora Yang

Mark L/ Behnke

Wenwei Huang

John C McKew

Jonathan Chernoff

William F. Forrest

Peter M. Haverty

Suet-Feung Chin

Professor of Breast Cancer Pathology

Carlos Caldas

Thomas O�Brien

Lori S. Friedman

Hartmut Koeppen

Joachim Rudolph

Klaus P. Hoeflich



Breast cancer, the most common cause of cancer-related deaths worldwide among women, is a molecularly and clinically heterogeneous disease. Extensive genetic and epigenetic profiling of breast tumors has recently revealed novel putative driver genes, including p21-activated kinase (PAK)1. PAK1 is a serine/threonine kinase downstream of small GTP-binding proteins, Rac1 and Cdc42, and is an integral component of growth factor signaling networks and cellular functions fundamental to tumorigenesis.


PAK1 dysregulation (copy number gain, mRNA and protein expression) was evaluated in two cohorts of breast cancer tissues (n = 980 and 1,108). A novel small molecule inhibitor, FRAX1036, and RNA interference were used to examine PAK1 loss of function and combination with docetaxel in vitro. Mechanism of action for the therapeutic combination, both cellular and molecular, was assessed via time-lapse microscopy and immunoblotting.


We demonstrate that focal genomic amplification and overexpression of PAK1 are associated with poor clinical outcome in the luminal subtype of breast cancer (P = 1.29 × 10−4 and P = 0.015, respectively). Given the role for PAK1 in regulating cytoskeletal organization, we hypothesized that combination of PAK1 inhibition with taxane treatment could be combined to further interfere with microtubule dynamics and cell survival. Consistent with this, administration of docetaxel with either a novel small molecule inhibitor of group I PAKs, FRAX1036, or PAK1 small interfering RNA oligonucleotides dramatically altered signaling to cytoskeletal-associated proteins, such as stathmin, and induced microtubule disorganization and cellular apoptosis. Live-cell imaging revealed that the duration of mitotic arrest mediated by docetaxel was significantly reduced in the presence of FRAX1036, and this was associated with increased kinetics of apoptosis.


Taken together, these findings further support PAK1 as a potential target in breast cancer and suggest combination with taxanes as a viable strategy to increase anti-tumor efficacy.


Ong, C. C., Gierke, S., Pitt, C., Sagolla, M., Cheng, C. K., Zhou, W., …Hoeflich, K. P. (2015). Small molecule inhibition of group I p21-activated kinases in breast cancer induces apoptosis and potentiates the activity of microtubule stabilizing agents. Breast Cancer Research, 17(1), Article 59.

Journal Article Type Article
Acceptance Date Mar 16, 2015
Online Publication Date Apr 23, 2015
Publication Date 2015-12
Deposit Date Oct 17, 2018
Publicly Available Date Oct 17, 2018
Journal Breast Cancer Research
Print ISSN 1465-5411
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 17
Issue 1
Article Number 59
Public URL
Publisher URL