A recombinant cell-permeable p53 fusion protein is selectively
stabilized under hypoxia and inhibits tumor cell growth
Yu Zhao
a
, Junhua Wu
a
, Shaoping Wu
b
, Peiyuan Jia
a
, Ying Tong
b
, Xumin Wu
b
, Yuxia Wang
a,
*
a
Beijing Institute of Pharmacology and Toxicology, 27, Taiping Road, Haidian District, Beijing 100850, China
b
Beijing Center of Disease Prevention and Control, Beijing 100031, China
article info
Article history:
Received 5 January 2009
Received in revised form 15 January 2009
Accepted 18 January 2009
Keywords:
TAT
Hypoxia-inducible factor-1
a
Oxygen-dependent degradation domain
p53
Hypoxia
Cancer therapy
Solid tumors
abstract
More than 50% of human tumors contain a mutation in p53. Over 90% of tumors are solid
tumors. Solid tumors have low oxygenated regions, called hypoxic regions where the
tumor cells are more resistant to radio- and chemo-therapy than their well-oxygenated
counterparts. In this study, we constructed a cell-permeable p53 fusion protein with
selective stability in the hypoxic region. The fusion protein contained the TAT peptide
for transduction across membranes, the oxygen-dependent degradation domain of
hypoxia-inducible factor-1alpha and wild-type p53. This protein was effectively delivered
into tumor cells where it exerted anticancer activity leading to the inhibition of cancer cell
growth in vitro and the reduction of tumor weight in vivo. Hence, the fusion protein can be
a novel protein drug for antitumor therapies, especially for hypoxic tumor cells.
Ó 2009 Elsevier Ireland Ltd. All rights reserved.
1. Introduction
The p53 tumor suppressor protein serves as an efficient
guardian against cancers. Over 50% of human tumors har-
bor a dysfunctional p53 caused by genetic mutation or
deletion [1]. Wild-type p53 is capable of preventing tumor
formation and progression via multiple mechanisms [2,3].
The major pathway relies on its transcriptional activity to
up-regulate numerous downstream genes associated with
cell-cycle arrest, senescence, autophagy, and apoptosis
[4–8]. Dysfunctional p53 not only fails to act as a tumor
suppressor, but also plays a key role in accelerating tumor-
igenesis. Mutant p53 proteins possess novel oncogenic
activities both in tissue culture and in experimental animal
models [9]. Thus, p53 has been a target for anticancer
treatment and reagents have been developed for the resto-
ration of p53 function in tumor cells [10]. However, their
utility is limited by poor permeability and low targeting-
delivery.
More than 90% of human tumors are solid tumors. Low-
oxygenated regions, called hypoxic regions, are present in
solid tumors [11]. In these regions, the oxygen tension is
low and the cancer cells adaptive to hypoxia are resistant
to conventional radiotherapy and chemotherapy [12]. Fur-
thermore, hypoxic tumor cells are predisposed to a more
malignant phenotype. Hypoxia-inducible factor-1 (HIF-1)
is a transcription factor that activates gene expression in
a hypoxic environment [13,14]. In oxygenated cells, the
HIF-1
a
subunits are rapidly destroyed via ubiquitylation
by the von Hippel-Lindau tumor suppressor E3 ligase com-
plex [15]. However, in hypoxic cells degradation of HIF-1
a
is suppressed, leading to transcriptional activation of tar-
get genes. Moreover, the full length oxygen-dependent
degradation domain of HIF-1
a
(ODD) as well as its mini-
mum domain (557–574) are capable of inducing expres-
sion of a fusion partner in a hypoxic environment [16,17].
For efficient delivery of therapeutic proteins, various
protein transduction domains have been used [18,19].
0304-3835/$ - see front matter Ó 2009 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.canlet.2009.01.030
* Corresponding author.
E-mail address: wangyuxia1962@hotmail.com (Y. Wang).
Cancer Letters 279 (2009) 101–107
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Cancer Letters
journal homepage: www.elsevier.com/locate/canlet