Research Papers:

This article has been corrected. Correction in: Oncotarget. 2018; 9:37608-9.

Hypoxia/reoxygenation-experienced cancer cell migration and metastasis are regulated by Rap1- and Rac1-GTPase activation via the expression of thymosin beta-4

Jae-Wook Lee _, Yun-Kyoung Ryu, Young-Hoon Ji, Joo Hyun Kang and Eun-Yi Moon

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Oncotarget. 2015; 6:9820-9833. https://doi.org/10.18632/oncotarget.3218

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Jae-Wook Lee1,*, Yun-Kyoung Ryu1,*, Young-Hoon Ji2, Joo Hyun Kang3, Eun-Yi Moon1

1Department of Bioscience and Biotechnology, Sejong University, Seoul 143–747, Korea

2Research Center for Radiotherapy, Korea Institute of Radiological and Medical Science, Seoul 139–709, Korea

3Molecular Imaging Research Center, Korea Institute of Radiological and Medical Science, Seoul 139–709, Korea

*These authors have contributed equally to this work

Correspondence to:

Eun-Yi Moon, e-mail: [email protected], [email protected]

Keywords: thymosin beta-4, Rac1-GTPase, Rap1-GTPase, cancer cell migration, tumor metastasis

Received: September 28, 2014     Accepted: January 26, 2015     Published: March 23, 2015


Signaling by small guanosine triphosphatases (GTPase), Rap1/Rac1, is one of the major pathways controlling cancer cell migration and tumor metastasis. Thymosin beta-4 (Tβ4), an actin-sequestering protein, has been shown to increase migration of cancer cells. Episodes of hypoxia and re-oxygenation (H/R) are an important phenomenon in tumor microenvironment (TME).

We investigated whether Tβ4 could play as an intermediary to crosstalk between Rac1- and Rap1- GTPase activation under hypoxia/reoxygenation (H/R) conditions. Inhibition of Tβ4 expression using transcription activator-like effector nucleases (TALEN) significantly decreased lung metastasis of B16F10 cells. Rac1 and Rap1 activity, as well as cancer cell migration, increased following induction of Tβ4 expression in normoxia- or H/R-experienced cells, but were barely detectable in Tβ4-depleted cells. Rap1-regulated Rac1 activity was decreased by a dominant negative Rap1 (Rap1N17), and increased by 8-(4-chloro-phenylthio)-2′-O-methyladenosine-3′,5′-cyclic monophosphate (CPT), a Rap1 activator. In contrast, a Rac1-specific inhibitor, NSC23766, and dominant negative Rac1 (Rac1N17) enhanced Tβ4 expression and aberrant Rap1 activity. While NSC23766 and Rac1N17 incompletely inhibited tumor metastasis in vivo, and H/R-experienced cancer cell migration in vitro, more efficient attenuation of cancer cell migration was accomplished by simultaneous inactivation of Rap1 and Rac1 with Rap1N17 and Rac1N17, respectively.

These data suggest that a combination therapy targeting both Rap1 and Rac1 activity may be an effective method of inhibiting tumor metastasis.

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