ARTICLE
Auteur(s) : Mark A Barber, Heidi CE Welch
Inositide Laboratory, The Babraham Institute, Babraham Research
Campus, Cambridge CB2 4AT, UK
Cell polarisation and migration
Most of our knowledge of the signalling pathways and cytoskeletal
regulation involved in eukaryotic cell migration comes from studies
on leukocytes and Dictyostelium discoideum, which are fast
migrating cells [1, 2]. Apart from leukocytes, most cells in the
human body are immotile, except during development and wound
healing. Cell migration during the latter processes is orders of
magnitude slower than neutrophil chemotaxis and, importantly,
non-leukocytes move while attached to one-another. During cancer
progression, subsets of tumour cells change from an immotile to
motile status, which can eventually lead to invasion and
metastasis. During early cancer progression, cells move while
attached to others. Progressively, as cell-cell adhesions are lost,
some of the cancer cells start to undergo individual cell
migration. They develop through an intermediate, mesenchymal stage
to an amoeboid mode of migration that resembles leukocyte
migration. Although different in many important aspects, all cell
migration requires similar events of cytoskeletal remodelling,
regulated by Rho family GTPases [3]. In this review we will
concentrate on the types of migration typical for leukocytes and
amoeboid-stage cancer cells.
To migrate, cells first establish a polarised morphology. Upon
detection of a chemoattractant by specific cell surface receptors,
a directional signal is transduced to the cell that activates and
relocates signalling molecules, resulting in the reorganisation of
the actomyosin-based cytoskeleton. This transforms the cell from a
spherical resting state to an asymmetrical polarised shape with a
leading and a trailing edge. Cell migration is dependent upon
formation of protrusions at the leading edge and translocation of
the cell body by actomyosin contractile forces at the sides and
back of the cell. Chemotaxis is the directed migration of cells up
a chemoattractant gradient. Within the gradient, chemoattractant
concentrations can differ by as little as 1 % along the length
of a cell [4], necessitating a steeper internal gradient of
signalling molecules, defining areas for cell-body extension at the
leading edge and contraction at the posterior. However, gradients
are not necessary for migration per se, as cells are able to
polarise and migrate in random directions even when exposed to
uniform concentrations of chemoattractant, showing that they can
self-organise their morphology for movement. Key signalling
molecules regulating cell polarisation and migration are
phosphoinositide 3-kinase (PI3K) and the Rho family of small
GTPases. PI3K activity defines the leading edge of the cell,
whereas Rho family GTPases regulate the cytoskeletal remodelling
during polarisation. Both PI3K and Rho family GTPases are required
for efficient cell migration [1]( (figure 1) ).
PI3K in polarisation and migration
In rapidly migrating leukocytes, and at least some types of motile
cancer cells [5], the initial step leading to polarisation and cell
migration is the activation of G-protein coupled cell surface
receptors by chemoattractants. During polarisation, the
chemoattractant receptors remain evenly distributed on the cell
membrane [6] and heterotrimeric G proteins immediately downstream
of the receptors show only a weak preference for the leading edge
[7], while further downstream signalling molecules display strong
asymmetrical distributions. Currently, PI3K activation is the first
detectable asymmetrical event, as visualised by translocation of
GFP-tagged probes for the lipid products of PI3K activity to the
cell membrane facing the chemoattractant source [8]. While
localised activation of PI3K defines the leading edge of the cell
[9, 10], it is currently not known how this localisation is
regulated.
PI3K synthesises the lipid second messenger
PI(3,4,5)P3 (or PIP3) at the inner surface of
the plasma membrane by phosphorylating the integral membrane lipid
PI(4,5)P2. PIP3 is produced by two classes of
PI3Ks, class 1A (PI3Kα, β and δ) and class 1B (PI3Kγ), which are
regulated by protein tyrosine kinases and Gβγ subunits,
respectively [2], with both classes being also activated by Ras.
Pharmacological inhibitors and genetic manipulation of PI3Ks have
shown these enzymes to be pivotal regulators of both polarisation
and cell migration. The pharmacological inhibitors wortmannin and
LY294002 reduce polarity and motility in neutrophils,
Dictyostelium, and in fact almost all eukaryotic cell types
studied, although in many studies residual polarity and motility
was found [2, 11-13]. Deletion of two class 1 PI3Ks from
Dictyostelium reduces polarity, speed of migration, and
directionality of migration [14]. Mouse neutrophils that lack the
PI3K subunit p110γ also display a reduced ability to polarise and
migrate in chemoattractant gradients, with directionality being
especially poor [15-18]. Chemotaxis of T lymphocytes in response to
various chemokines is reduced in p110γ-/- mice, whereas
that of B lymphocytes is reduced in p110δ-/- mice [19].
The synthesis of PIP3 is thus an important early
response in polarisation and chemotaxis, but it is currently not
clear to what extent it is necessary in different systems. Judging
by the different levels of reduction in chemotaxis found upon
inhibition of PI3K in different studies, the relative importance of
PIP3 may vary between cell types. Nevertheless,
PIP3 is sufficient for leukocyte polarisation and
chemotaxis; the addition of cell-permeable analogues of
PIP3 into neutrophils and neutrophil-like cell lines
stimulates cell polarisation and migration [20, 21].
The asymmetric distribution of PIP3 in chemotaxing
leukocytes seems to be maintained through spatially and temporally
controlled positive feedback and negative regulation. Positive
feedback is thought to operate through PIP3, stimulating
further production of PIP3. Evidence for this comes from
the finding that the polarised neutrophil morphology induced by
exogenous PIP3 is blocked by wortmannin and LY294002
[20, 21]. A likely mechanism for this positive feedback involves
Rho GTPases (which can act both up and downstream of PI3K; see
below). Inactivation of the Rho-GTPases Rac, Rho and/or Cdc42 with
different Clostridium toxins and dominant-negative mutants inhibits
the membrane translocation of GFP-tagged probes for the lipid
products of PI3Ks. This revealed that Rac is most likely the GTPase
responsible for mediating positive feedback at the leading edge [8,
21-23]. The second leg of the positive feedback loop, the
generation of more PIP3 downstream of Rac activation, is
less well defined. Evidence for sequential activation of different
types of PI3Ks in human neutrophils comes from the use of new
isoform-specific inhibitors. These have shown that fMLP-dependent
PIP3-generation is bi-phasic, with the first phase
generated by PI3Kγ and the second phase being dependent on the
first, and generated by PI3Kδ [24]. However, the contribution of
different types of PI3Ks in any positive feedback mechanisms
involved in polarisation and migration, and the mechanism of how
Rac would link them, is still unclear.
In addition to positive feedback on PI3K activity, asymmetric
PIP3 accumulation is maintained by actively excluding it
from the trailing edge through regulation by phosphatases. The
phosphoinositide phosphatases PTEN and SHIP catalyse the conversion
of PIP3 into PI(4,5)P2 and
PI(3,4)P2, respectively, thus acting as negative
regulators of PI3K activity [25, 26]. During polarisation, PTEN is
indirectly activated by RhoA and Cdc42. Cdc42 is activated by PIXα
in a complex containing Gβγ subunits and PAK, immediately
downstream of receptor activation [27]. Active Cdc42 is required to
localise RhoA; and active RhoA at the back of the cell activates
Rock, which then phosphorylates and activates PTEN [28]( (figure 1) ). SHIPs
role in cell migration was demonstrated by overexpression of
constitutively active SHIP inhibiting chemotaxis of Jurkat T-cells
[29] and SHIP-/- mice exhibiting excessive myeloid
infiltration into major organs [26].
PI3K signals at the membrane are interpreted by a large group of
proteins that bind PIP3 and translocate and/or become
activated in the process. Although Rac is a key effector of PI3K in
the establishment of cell polarity and migration, it is not a
direct target of PIP3. The identity of the enzyme(s)
that link PIP3 formation to the activation of Rac in the
process of polarisation and migration is currently not known (see
below). However, many known direct targets of PI3K activity, such
as PDK/PKB and WAVE2, are directly activated and/or translocate
through PIP3-binding during polarisation and migration,
and contribute to these complex cellular responses [30].
RAC in polarisation and migration
Active Rac stimulates actin polymerisation by binding, via
intermediates, to WAVE2, a member of the WASP family. WAVE2 binds
to monomeric G-actin and the Arp2/3 complex, the latter catalysing
actin polymerisation [31]. Rac activation at the leading edge is
the key determinant of where actin polymerisation occurs during
polarisation and results in lamellipodial protrusions in the
direction of migration. Recently, Hem-1 has been identified as an
important scaffold protein for the formation of Rac-containing
multiprotein complexes at the leading edge that are crucial for
polarisation and migration of neutrophil-like HL60 cells [32].
Three isoforms of Rac have been identified. Rac1 is ubiquitously
expressed, Rac2 is in haematopoietic cells, and Rac3 is found in
the nervous system. Both leukocyte isoforms of Rac, Rac1 and Rac2,
are required for chemotaxis, and both play common and unique roles.
In human neutrophils, Rac2 is the predominant isoform, whereas in
mice, Rac1 and Rac2 are expressed at similar levels [33]. In
humans, the dominant-negative Rac2 mutation D57N causes severe
recurrent bacterial infections, with neutrophils unable to be
recruited to sites of infection [34, 35]. Isolated D57N-Rac2
neutrophils cannot chemotax in response to chemoattractant [34,
35]. In Rac2-/- mice, neutrophil adhesion, polarisation
and chemotaxis are so severely impaired that Rac2-/-
neutrophils are practically immotile [33, 36–39]. In contrast,
mouse neutrophils with a conditional Rac1 deficiency can move, but
with poor directionality [37, 40, 41]. It was thus proposed that
Rac2 provides the molecular motor for migration through actin
remodelling, whereas Rac1 is responsible for gradient detection and
localisation [40]. Furthermore, the use of chimeric Rac isoforms
has identified the C-terminal polybasic domain as sufficient for
determining Rac isoform specificity in murine neutrophil chemotaxis
[41].
GEFS in polarisation and migration
Rho GTPases cycle between active (GTP bound) and inactive (GDP
bound) states and have an inherent ability to catalyse their own
inactivation by hydrolysing GTP to GDP. Their activity is directly
modulated by three classes of proteins: guanine-nucleotide exchange
factors (GEFs) that catalyse GDP/GTP exchange; GTPase-activating
proteins (GAPs) that accelerate the hydrolysis of GTP to GDP; and
GDP dissociation inhibitors (GDIs) that prevent exchange of GDP for
GTP [42]. GEFs are the critical mediators of Rho GTPase activation,
as they remove the GDP, allowing GTP from an excess free GTP pool
to bind [43]. As mentioned above, Rac activation by PIP3
during cell polarisation must be relayed via intermediary proteins.
It is likely that the key intermediate is a
PIP3-sensitive GEF.
Classical GEFs belong to the Dbl protein family and are
characterised by a catalytic DH domain in tandem with a PH domain
[43]. PH domain affinity for PIP3 provides an obvious
mechanism for GEFs (and therefore GTPase signalling) to be
regulated by PI3K activity. Several Dbl-family GEFs are able to
bind PIP3, including P-Rex1, Sos1, Tiam1, and Vav1. The
Rac specific GEF P-Rex1 is highly abundant in human neutrophils and
activated directly by PIP3 and Gβγ binding [44], so it
has generally been assumed to be a key target of PI3K during
chemotaxis. However, the generation of P-Rex1-/- mice
has shown that, while P-Rex1 is an important regulator of ROS
formation, it is not necessary for chemoattractant-dependent actin
remodelling, polarisation or chemotaxis in neutrophils, although it
does modulate these responses to some extent [45, 46].
Vav1-/- neutrophils have a similar phenotype, with a
minor role for Vav1 in fMLP-induced chemotaxis [47]. An involvement
of the unusual Rac-GEF Swap70 (unusual because the PH domain is on
the ‘wrong’ side of the DH domain) in cell migration has been shown
in SCF-stimulated mast cells from Swap70-/- mice
[48].
In addition to Dbl-family GEFs, CDM family proteins also
activate small GTPases, through a mechanism that is still not
completely understood but involves complex-formation with the
adaptor proteins Elmo and Crk. They regulate actin-polymerisation
related cell responses including spreading, phagocytosis and
migration in organisms ranging from invertebrates to humans.
DOCK180 is the most-studied member of this family. It has recently
been shown that DOCK180 can bind PIP3 through its DHR-1
domain [49]. PIP3-binding to DHR-1 is essential for the
translocation of DOCK180 protein complex from the cytoplasm to the
plasma membrane. Additionally, PIP3-binding is essential
for inducing actin remodelling, and mutants lacking the DHR-1
domain associate with actin-polymerases and increase cellular
Rac-GTP but are unable to trigger polymerisation [49]. Importantly,
another member of the CDM family, DOCK2, has been shown to be
essential for T and B lymphocyte migration (but not monocyte
migration) in response to various chemokines [50, 51]. Hence it
seems more than likely, that members of the CDM family will be
proven before long to a general link between
PIP3-formation and Rac activation in leukocyte
chemotaxis ( (figure
2) ).
PI3K signalling in cancer
PI3K signalling is important for cell growth, survival, and
division, as well as cell motility, via many different pathways
that include, apart from the Rho GTPases, immediate effectors such
as PDK/PKB and further downstream effectors like mTor, GSK, and BAD
[52]. All of these pathways underlie the ability of PI3K to
contribute to oncogenesis as a tumour promoter. Overexpression of
PI3K has been identified in several types of cancers, mainly
ovarian and cervical cancers [53, 54]. However, more recently it
has been shown that somatic mutations in PIK3CA, the gene that
encodes the catalytic subunit p110α of PI3K, are extremely common
in a wide range of solid human cancers [55]. Cancer-specific
mutations are found in two major hot-spots and impart increased
lipid kinase activity when compared to wild-type protein. The
oncogenic potential of these mutated forms have been confirmed
in vitro [55] and in vivo [56]. The well-characterised
PI3K inhibitors wortmannin and LY294002 show tumour inhibiting
activity in vitro and in vivo [57-60]. Interestingly
though, inhibition of tumour growth does not always correlate with
inhibition of PI3K activity, suggesting that these compounds are
able to suppress tumourigenic activity outside of their specified
targets [59, 61]. Both compounds are very limited in their clinical
applicability due to poor solubility and high toxicity. LY294002
was less toxic and displayed greatest potential when used in
combination with chemotherapy in mouse models [62, 63]. The
combination of PI3K inhibitors with chemotherapy may be most useful
in cases were traditional chemotherapy treatments are no longer
effective. The wortmannin derivative, PX-866, is more potent and
less toxic than its parent compound and has inhibited the
in vivo growth of a range of human tumour xenografts [64]. A
general lack of specificity in PI3K inhibitors makes it doubtful
that these compounds will achieve a sufficient therapeutic index in
clinical trials. Inhibition of signalling components downstream of
PI3K has generated much more promising therapeutic leads. Several
inhibitors directed against the PI3K effectors PDK1/PKB and mTOR
are at various stages of clinical trials. These inhibitors are
active in a range of tissue types suggesting that targeting the
PI3K-mTOR pathway may be a suitable target against a range of
cancer types [65].
As a negative regulator of PI3K activity, PTEN is a potent
tumour suppressor and loss of PTEN expression is seen in many
cancer types [66]. Through the dephosphorylation of
PIP3, PTEN inhibits, among other pathways, activation
and phosphorylation of PDK1 and therefore its downstream activation
of PKB. Inhibition of PKB acts to stimulate apoptosis and blocks
progression of the cell cycle at the G1–S interphase [66]. Hence,
reconstitution of PTEN activity is an important method for
inhibiting tumour growth downstream of PI3K activity.
Overexpression of PTEN in transgenic mice has been shown to reduce
Wnt induced mammary hyperplasia [67]. Reconstitution of active PTEN
through an adenoviral vector abolished bladder carcinomas in
PTEN-/- mice and transiently suppressed tumour growth in
wild-type PTEN expressing mice [68]. Non-viral delivery of active
PTEN suppressed PKB phosphorylation and induced apoptosis in a
mouse lung cancer model [69], while adenoviral delivery of PTEN is
able to induce apoptosis in colorectal cancer cells and xenografts
[70, 71].
RAC signalling in cancer
Rho GTPases are implicated in cancer progression by promoting
invasion and metastasis through their regulation of cell migration.
Mutations of Rho GTPase genes in cancers are rare, but deregulated
expression of Rho GTPases has been identified in a range of human
cancers (table 1( Table 1 )).
Information on the role of Rac in cancer progression is sparse.
In colorectal tumours, an overexpressed splice variant of Rac1,
Rac1b, was identified [72]. The Rac1b splice variant contains an
additional 19 amino acids, functions in a way similar to
constitutively active Rac1 [72], and can transform cultured
fibroblasts. The only animal model for Rac involvement in cancer
progression is a Rac3-/- mouse, crossed with mice
containing the BCR-ABL fusion oncogene [73]. Lymphoblasts of mice
expressing this fusion gene contain a constitutively active form of
the Rac-GEF Vav and develop acute lymphoblastic leukaemia as a
result. Female mice lacking Rac3 expression are protected against
leukaemia development and out-live mice with functional Rac3,
suggesting an involvement for Rac3 in B-cell lymphoma [73].
Other Rho family GTPases have also been implicated in cancer
progression. RhoC overexpression is used as a tissue biomarker for
aggressive breast carcinomas [74]. Two mouse models for the role of
RhoC in cancer exist. In the first, RhoC was retrovirally
transduced into murine lung cancer cells and these were
intrapulmonarily inoculated into syngeneic mice [75]. Metastases in
lymph nodes were significantly enhanced while the growth of the
primary tumours in the lung was the same [75]. The second mouse
model is the recently generated RhoC-/- mouse crossed
with a Polyoma Middle T transgenic mouse. Development of the
expected mammary adenocarcinomas was unaffected, but RhoC was
essential for tumour cell motility and metastatic cell survival,
and RhoC-deficiency resulted in the development of lung metastases
[76]. A fusion between the genes for RhoH and LAZ3 was identified
in patients suffering from non-Hodgkin’s lymphoma [77]. This fusion
event produces a single mRNA transcript, but it is unclear if the
RhoH portion of the fusion product is responsible for inducing
oncogenic behaviour [77]. Recent experiments have identified RhoH
as a negative regulator of growth, possibly through suppressing
Rac-mediated signalling. Reduction of RhoH expression using siRNA
increases proliferation, migration, and survival of haematopoietic
progenitor cells [78], thus suggesting that the oncogenic activity
of the RhoH-LAZ3 fusion could be mediated through negatively
regulating RhoH activity.
Table 1 Involvement of Rho family GTPases, GEFs and
GAPS in cancer
|
Rho family GTPase /GEF/GAP
|
Cancer type
|
Modification
|
References
|
|
Rac1
|
Breast
|
Overexpression
|
[95]
|
|
Oral squamous cell carcinoma
|
Overexpression
|
[96]
|
|
Rac1b
|
Breast, colon
|
Overexpression
|
[97]
|
|
Rac2
|
Breast
|
Overexpression
|
[98]
|
|
Rac3
|
Brain
|
Overexpression
|
[99]
|
|
Breast
|
Hyperactivity
|
[73]
|
|
Bcr/Abl induced B-lineage lymphoma (in mice)
|
Hyperactivity
|
|
|
Cdc42
|
Breast
|
Overexpression
|
[98]
|
|
RhoA
|
Breast
|
Overexpression
|
[98, 100–102]
|
|
Squamous cell carcinoma
|
Overexpression
|
[103]
|
|
Lung, colon, testis
|
Overexpression
|
[104]
|
|
Bladder
|
Overexpression
|
[105]
|
|
RhoB
|
Several
|
Loss
|
[106]
|
|
Lung
|
Loss
|
[107]
|
|
RhoC
|
Lung (human)
|
Overexpression
|
[108]
|
|
Lung (in mice)
|
|
[76, 109, 110]
|
|
RhoE
|
Prostate
|
Loss
|
[111]
|
|
RhoG
|
Breast
|
Overexpression
|
[112]
|
|
RhoH
|
Hodgkins lymphoma
|
Rearrangement/
|
[77]
|
|
Multiple myeloma
|
Deregulation
|
[113]
|
|
Diffuse large B-cell lymphoma
|
Point mutations
|
|
|
Tiam1 (Rac-GEF)
|
Ras-induced skin tumour (in mice)
|
Hyperactivity
|
[91]
|
|
P-Rex1 (Rac-GEF)
|
PDGF-induced glioma (in mice)
|
Insertional mutagenesis Overexpression
|
[87]
|
|
|
[88]
|
|
Vav1 (Rac-GEF)
|
Pancreatic adenocarcinoma
|
Overexpression
|
[82]
|
|
Neuroblastoma
|
Overexpression
|
[83]
|
|
β-PIX (Rac, Cdc42-GEF
|
Breast
|
Overexpression
|
[84]
|
|
LARG (Rho-GEF)
|
Acute myeloid leukemia
|
Fusion to MLL
|
[85, 86]
|
|
p190RhoGAP
|
PDGF-induced glioma (in mice)
|
Loss
|
[114]
|
|
Insertional mutagenesis
|
[87]
|
|
DLC-1 (RhoA and Cdc42-GAP)
|
Liver
|
Loss; Methylation
|
[115]
|
|
DLC-2 (RhoA and Cdc42-GAP)
|
Liver
|
Loss
|
[116]
|
|
ARHGAP8 (Rho-GAP?)
|
Colorectal cancer
|
Overexpression
|
[117]
|
|
ARHGAP9 (Rho-GAP?)
|
PDGF induced glioma (in mice)
|
Insertional mutagenesis
|
[87]
|
GEF signalling in cancer
Several GEFs for Rho family GTPases have been shown to have
transforming potential in cultured cells as a result of activating
point mutations or deletion of auto-inhibitory sequences. Such
mutations have been documented, for example, for Dbl [79], LARG
[80] and Tiam1 [81]. As with the RhoGTPases, several of their GEFs
have been found to be overexpressed in human cancers (and their
GAPs lost), while mutations in cancers are rare (table 1). The
Rac-GEF Vav1 is overexpressed in human pancreatic adenocarcinomas
and neuroblastomas and the Rac-GEF β-PIX is overexpressed in breast
cancer [82-84]. Fusion of the MLL gene to other genes is common in
acute leukaemias, and the gene for the Rho-GEF LARG is found fused
to MLL in acute myeloid leukaemia [85, 86]. P-Rex1 has recently
emerged as a potential tumour promoter from a screen for
cancer-causing genes using insertional mutagenesis through
retroviral tagging in mouse brain and was found to be upregulated
in these brain [87, 88].
There are now quite a few animal models available for the study
of GEFs of Rho family GTPases, although disappointingly none of
these have so far been used to investigate potential roles of GEFs
in cancer, with the notable exception of Tiam1. The Rac-GEF Tiam1
was originally identified in an in vitro screen for genes that
promote T-lymphoma invasion and metastasis [89]. Overexpression of
Tiam1 correlates with the grade of human breast cancer and the
metastatic potential of human breast carcinoma cell lines in nude
mice [90]. Tiam1-/- mice are relatively resistant to
Ras-induced skin tumours, which would agree with a role for
Tiam/Rac in cancer formation, however those tumours that do develop
are more aggressive [91]. Altogether, the role of Tiam1 in cancers
is not straightforward as, in cell culture, Tiam1 often induces
adhesion instead of migration [90]. Interestingly, a common adaptor
of CDM-family GEFs, Crk, was recently knocked-down in a human
ovarian cancer cell line [92]. Injection of these Crk knockdown
tumour cells into nude mice lead to smaller-than expected tumours,
suggesting the possibility that CDM proteins could regulate tumour
formation [92].
PI3K, RAC and GEF signalling in cancer cell migration
Our knowledge of the roles of PI3K, Rac and Rac-GEF signalling in
cancer cell migration is currently mainly extrapolated from our
knowledge of their pivotal roles in cell migration generally [5].
From the manipulation of PI3K, Rac or Rac-GEF activities in cancer
cell lines, and from the few relevant animal models that have been
examined for cancer-related phenotypes so far, it seems that these
enzymes play the same roles in cancer cell migration as in the
migration of non-cancerous cells.
As noted above, broad inhibitors of PI3K and/or Rac signalling
are practically unusable in cancer therapy as the pathways
regulated by PI3K and Rac are too vast, making these inhibitors
highly toxic, and those inhibitors that look most promising at the
moment target PI3K downstream-effectors involved in cell growth and
survival. A possible avenue for future anti-invasion and
anti-metastasis drug development might come from the exploitation
of many recent studies showing Rac and Rac-GEFs to be in complex
with different sets of proteins for different cellular processes
[32, 93, 94]. If we could develop small molecule inhibitors that
specifically interrupt PI3K, Rac-GEF and/or Rac activation when in
complex with proteins required for polarisation and cell migration,
we might be able to target invasion and metastasis, and although
these would likely also inhibit leukocyte migration, they might
eliminate many of the toxic side-effects of broader inhibitors.
Acknowledgements
This work was funded by a Career Development Award from the Medical
Research Council.
References
1 Fenteany G, Glogauer M. Cytoskeletal remodeling in
leukocyte function. Curr Opin Hematol 2004; 11: 15-24.
2 Merlot S, Firtel RA. Leading the way: Directional
sensing through phosphatidylinositol 3-kinase and other signaling
pathways. J Cell Sci 2003; 116(Pt 17): 3471-8.
3 Yamazaki D, Kurisu S, Takenawa T. Regulation of
cancer cell motility through actin reorganization. Cancer Sci 2005;
96: 379-86.
4 Zigmond SH. Ability of polymorphonuclear leukocytes to
orient in gradients of chemotactic factors. J Cell Biol 1977; 75(2
Pt 1): 606-16.
5 Mareel M, Leroy A. Clinical, cellular, and molecular
aspects of cancer invasion. Physiol Rev 2003; 83: 337-76.
6 Servant G, Weiner OD, Neptune ER,
Sedat JW, Bourne HR, et al. Dynamics of a
chemoattractant receptor in living neutrophils during chemotaxis.
Mol Biol Cell 1999; 10: 1163-78.
7 Jin T, Zhang N, Long Y, Parent CA,
Devreotes PN, et al. Localization of the G protein
betagamma complex in living cells during chemotaxis. Science 2000;
287: 1034-6.
8 Servant G, Weiner OD, Herzmark P, Balla T,
Sedat JW, Bourne HR, et al. Polarization of
chemoattractant receptor signaling during neutrophil chemotaxis.
Science 2000; 287: 1037-40.
9 Rickert P, Weiner OD, Wang F, Bourne HR,
Servant G, et al. Leukocytes navigate by compass: roles
of PI3Kgamma and its lipid products. Trends Cell Biol 2000; 10:
466-73.
10 Procko E, McColl SR. Leukocytes on the move with
phosphoinositide 3-kinase and its downstream effectors. Bioessays
2005; 27: 153-63.
11 Wang F, Herzmark P, Weiner OD,
Srinivasan S, Servant G, Bourne HR, et al.
Lipid products of PI(3)Ks maintain persistent cell polarity and
directed motility in neutrophils. Nat Cell Biol 2002; 4: 513-8.
12 Niggli V, Keller H. The phosphatidylinositol
3-kinase inhibitor wortmannin markedly reduces chemotactic
peptide-induced locomotion and increases in cytoskeletal actin in
human neutrophils. Eur J Pharmacol 1997; 335: 43-52.
13 Chung CY, Funamoto S, Firtel RA. Signaling
pathways controlling cell polarity and chemotaxis. Trends Biochem
Sci 2001; 26: 557-66.
14 Funamoto S, Milan K, Meili R, Firtel RA,
et al. Role of phosphatidylinositol 3’ kinase and a downstream
pleckstrin homology domain-containing protein in controlling
chemotaxis in dictyostelium. J Cell Biol 2001; 153: 795-810.
15 Sasaki T, Irie-Sasaki J, Jones RG,
Oliveira-dos-Santos AJ, Stanford WL, Bolon B,
et al. Function of PI3Kgamma in thymocyte development, T cell
activation, and neutrophil migration. Science 2000; 287:
1040-6.
16 Li Z, Jiang H, Xie W, Zhang Z,
Smrcka AV, Wu D, et al. Roles of PLC-beta2 and
-beta3 and PI3Kgamma in chemoattractant-mediated signal
transduction. Science 2000; 287: 1046-9.
17 Hirsch E, Katanaev VL, Garlanda C,
Azzolino O, Pirola L, Silengo L, et al. Central
role for G protein-coupled phosphoinositide 3-kinase gamma in
inflammation. Science 2000; 287: 1049-53.
18 Hannigan M, Zhan L, Li Z, Ai Y,
Wu D, Huang CK, et al. Neutrophils lacking
phosphoinositide 3-kinase gamma show loss of directionality during
N-formyl-Met-Leu-Phe-induced chemotaxis. Proc Natl Acad Sci USA
2002; 99: 3603-8.
19 Reif K, Okkenhaug K, Sasaki T,
Penninger JM, Vanhaesebroeck B, Cyster JG,
et al. Cutting edge: differential roles for phosphoinositide
3-kinases, p110gamma and p110delta, in lymphocyte chemotaxis and
homing. J Immunol 2004; 173: 2236-40.
20 Niggli V. A membrane-permeant ester of
phosphatidylinositol 3,4, 5-trisphosphate (PIP(3)) is an activator
of human neutrophil migration. FEBS Lett 2000; 473: 217-21.
21 Weiner OD, Neilsen PO, Prestwich GD,
Kirschner MW, Cantley LC, Bourne HR, et al. A
PtdInsP(3)- and Rho GTPase-mediated positive feedback loop
regulates neutrophil polarity. Nat Cell Biol 2002; 4: 509-13.
22 Zheng Y, Bagrodia S, Cerione RA. Activation of
phosphoinositide 3-kinase activity by Cdc42Hs binding to p85. J
Biol Chem 1994; 269: 18727-30.
23 Srinivasan S, Wang F, Glavas S, Ott A,
Hofmann F, Aktories K, et al. Rac and Cdc42 play
distinct roles in regulating PI(3,4,5)P3 and polarity during
neutrophil chemotaxis. J Cell Biol 2003; 160: 375-85.
24 Condliffe AM, Davidson K, Anderson KE,
Ellson CD, Crabbe T, Okkenhaug K, et al.
Sequential activation of class IB and class IA PI3K is important
for the primed respiratory burst of human but not murine
neutrophils. Blood 2005; 106: 1432-40.
25 Tamura M, Gu J, Matsumoto K, Aota S,
Parsons R, Yamada KM, et al. Inhibition of cell
migration, spreading, and focal adhesions by tumor suppressor PTEN.
Science 1998; 280: 1614-7.
26 Helgason CD, Damen JE, Rosten P,
Grewal R, Sorensen P, Chapp, et al. Targeted
disruption of SHIP leads to hemopoietic perturbations, lung
pathology, and a shortened life span. Genes Dev 1998; 12:
1610-20.
27 Li Z, Hannigan M, Mo Z, Liu B, Lu W,
Wu Y, et al. Directional sensing requires G beta
gamma-mediated PAK1 and PIX alpha-dependent activation of Cdc42.
Cell 2003; 114: 215-27.
28 Li Z, Dong X, Wang Z, Liu W, Deng N,
Ding, et al. Regulation of PTEN by Rho small GTPases. Nat Cell
Biol 2005; 7: 399-404.
29 Wain CM, Westwick J, Ward SG. Heterologous
regulation of chemokine receptor signaling by the lipid phosphatase
SHIP in lymphocytes. Cell Signal 2005; 17: 1194-202.
30 Oikawa T, Yamaguchi H, Itoh T, Kato M,
Ijuin T, Yamazaki D, et al. PtdIns(3,4,5)P3 binding
is necessary for WAVE2-induced formation of lamellipodia. Nat Cell
Biol 2004; 6: 420-6.
31 Takenawa T, Miki H. WASP and WAVE family proteins:
key molecules for rapid rearrangement of cortical actin filaments
and cell movement. J Cell Sci 2001; 114(Pt 10): 1801-9.
32 Weiner OD, Rentel MC, Ott A, Brown GE,
Jedrychowski M, Yaffe MB, et al. Hem-1 complexes are
essential for Rac activation, actin polymerization, and myosin
regulation during neutrophil chemotaxis. PLoS Biol 2006; 4:
e38.
33 Li S, Yamauchi A, Marchal CC,
Molitoris JK, Quilliam LA, Dinauer MC, et al.
Chemoattractant-stimulated Rac activation in wild-type and
Rac2-deficient murine neutrophils: preferential activation of Rac2
and Rac2 gene dosage effect on neutrophil functions. J Immunol
2002; 169: 5043-51.
34 Ambruso DR, Knall C, Abell AN,
Panepinto J, Kurkchubasche A, Thurman G, et al.
Human neutrophil immunodeficiency syndrome is associated with an
inhibitory Rac2 mutation. Proc Natl Acad Sci USA 2000; 97:
4654-9.
35 Williams DA, Tao W, Yang F, Kim C,
Gu Y, Mansfield P, et al. Dominant negative mutation
of the hematopoietic-specific Rho GTPase, Rac2, is associated with
a human phagocyte immunodeficiency. Blood 2000; 96: 1646-54.
36 Roberts AW, Kim C, Zhen L, Lowe JB,
Kapur R, Petryniak B, et al. Deficiency of the
hematopoietic cell-specific Rho family GTPase Rac2 is characterized
by abnormalities in neutrophil function and host defense. Immunity
1999; 10: 183-96.
37 Gu Y, Filippi MD, Cancelas JA,
Siefring JE, Williams EP, Jasti AC, et al.
Hematopoietic cell regulation by Rac1 and Rac2 guanosine
triphosphatases. Science 2003; 302: 445-9.
38 Abdel-Latif D, Steward M, Macdonald DL,
Francis GA, Dinauer MC, Lacy P, et al. Rac2 is
critical for neutrophil primary granule exocytosis. Blood 2004;
104: 832-9.
39 Filippi MD, Harris CE, Meller J, Gu Y,
Zheng Y, Williams DA, et al. Localization of Rac2
via the C terminus and aspartic acid 150 specifies superoxide
generation, actin polarity and chemotaxis in neutrophils. Nat
Immunol 2004; 5: 744-51.
40 Sun CX, Downey GP, Zhu F, Koh AL,
Thang H, Glogauer M, et al. Rac1 is the small GTPase
responsible for regulating the neutrophil chemotaxis compass. Blood
2004; 104: 3758-65.
41 Yamauchi A, Marchal CC, Molitoris J,
Pech N, Knaus U, Towe J, et al. Rac GTPase
isoform-specific regulation of NADPH oxidase and chemotaxis in
murine neutrophils in vivo. Role of the C-terminal polybasic
domain. J Biol Chem 2005; 280: 953-64.
42 Ridley AJ. Rho family proteins: coordinating cell
responses. Trends Cell Biol 2001; 11: 471-7.
43 Schmidt A, Hall A. Guanine nucleotide exchange
factors for Rho GTPases: turning on the switch. Genes Dev 2002; 16:
1587-609.
44 Welch HC, Coadwell WJ, Ellson CD,
Ferguson GJ, Andrews SR, Erdjument-Bromage H,
et al. P-Rex1, a PtdIns(3,4,5)P3- and Gbetagamma-regulated
guanine-nucleotide exchange factor for Rac. Cell 2002; 108:
809-21.
45 Welch HC, Condliffe AM, Milne LJ,
Ferguson GJ, Hill K, Webb LM, et al. P-Rex1
regulates neutrophil function. Curr Biol 2005; 15: 1867-73.
46 Dong X, Bokoch Z, Guo G, Li CZ,
Wu D, et al. P-Rex1 is a primary Rac2 guanine nucleotide
exchange factor in mouse neutrophils. Curr Biol 2005; 15:
1874-9.
47 Kim C, Marchal CC, Penninger J,
Dinauer MC. The hemopoietic Rho/Rac guanine nucleotide
exchange factor Vav1 regulates
N-formyl-methionyl-leucyl-phenylalanine-activated neutrophil
functions. J Immunol 2003; 171: 4425-30.
48 Sivalenka RR, Jessberger R. SWAP-70 regulates
c-kit-induced mast cell activation, cell-cell adhesion, and
migration. Mol Cell Biol 2004; 24: 10277-88.
49 Cote JF, Motoyama AB, Bush JA, Vuori RK,
et al. A novel and evolutionarily conserved
PtdIns(3,4,5)P3-binding domain is necessary for DOCK180 signalling.
Nat Cell Biol 2005; 7: 797-807.
50 Fukui Y, Hashimoto O, Sanui T, Oono T,
Koga H, Abe M, et al. Haematopoietic cell-specific
CDM family protein DOCK2 is essential for lymphocyte migration.
Nature 2001; 412: 826-31.
51 Reif K, Cyster J. The CDM protein DOCK2 in
lymphocyte migration. Trends Cell Biol 2002; 12: 368-73.
52 Stephens L, Williams R, Hawkins P.
Phosphoinositide 3-kinases as drug targets in cancer. Curr Opin
Pharmacol 2005; 5: 357-65.
53 Ma YY, Wei SJ, Lin YC, Lung JC,
Chang TC, Whang-Peng J, et al. PIK3CA as an oncogene
in cervical cancer. Oncogene 2000; 19: 2739-44.
54 Shayesteh L, Lu Y, Kuo WL, Baldocchi R,
Godfrey T, Collins C, et al. PIK3CA is implicated as
an oncogene in ovarian cancer. Nat Genet 1999; 21: 99-102.
55 Samuels Y, Wang Z, Bardelli A,
Silliman N, Ptak J, Szabo S, et al. High
frequency of mutations of the PIK3CA gene in human cancers. Science
2004; 304: 554.
56 Bader AG, Kang S, Vogt PK. Cancer-specific
mutations in PIK3CA are oncogenic in vivo. Proc Natl Acad Sci USA
2006; 103: 1475-9.
57 Itoh N, Semba S, Ito M, Takeda H,
Kawata S, Yamakawa M, et al. Phosphorylation of
Akt/PKB is required for suppression of cancer cell apoptosis and
tumor progression in human colorectal carcinoma. Cancer 2002; 94:
3127-34.
58 Hu L, Zaloudek C, Mills GB, Gray J,
Jaffe RB, et al. In vivo and in vitro ovarian carcinoma
growth inhibition by a phosphatidylinositol 3-kinase inhibitor
(LY294002). Clin Cancer Res 2000; 6: 880-6.
59 Lemke LE, Paine-Murrieta GD, Taylor CW,
Powis G, et al. Wortmannin inhibits the growth of mammary
tumors despite the existence of a novel wortmannin-insensitive
phosphatidylinositol-3-kinase. Cancer Chemother Pharmacol 1999; 44:
491-7.
60 Schultz RM, Merriman RL, Andis SL,
Bonjouklian R, Grindey GB, Rutherford PG,
et al. In vitro and in vivo antitumor activity of the
phosphatidylinositol-3-kinase inhibitor, wortmannin. Anticancer Res
1995; 15: 1135-9.
61 Semba S, Itoh N, Ito M, Harada M,
Yamakawa M, et al. The in vitro and in vivo effects of
2-(4-morpholinyl)-8-phenyl-chromone (LY294002), a specific
inhibitor of phosphatidylinositol 3’-kinase, in human colon cancer
cells. Clin Cancer Res 2002; 8: 1957-63.
62 Bondar VM, Sweeney-Gotsch B, Andreeff M,
Mills GB, McConkey DJ, et al. Inhibition of the
phosphatidylinositol 3’-kinase-AKT pathway induces apoptosis in
pancreatic carcinoma cells in vitro and in vivo. Mol Cancer Ther
2002; 1: 989-97.
63 Hu L, Hofmann J, Lu Y, Mills GB,
Jaffe RB, et al. Inhibition of phosphatidylinositol
3’-kinase increases efficacy of paclitaxel in in vitro and in vivo
ovarian cancer models. Cancer Res 2002; 62: 1087-92.
64 Ihle NT, Williams R, Chow S, Chew W,
Berggren MI, Paine-Murrieta G, et al. Molecular
pharmacology and antitumor activity of PX-866, a novel inhibitor of
phosphoinositide-3-kinase signaling. Mol Cancer Ther 2004; 3:
763-72.
65 Granville CA, Memmott RM, Gills JJ,
Dennis PA, et al. Handicapping the race to develop
inhibitors of the phosphoinositide 3-kinase/Akt/mammalian target of
rapamycin pathway. Clin Cancer Res 2006; 12(3 Pt 1): 679-89.
66 Chu EC, Tarnawski AS. PTEN regulatory functions in
tumor suppression and cell biology. Med Sci Monit 2004; 10:
RA235-RA241.
67 Zhao H, Cui Y, Dupont J, Sun H,
Hennighausen L, Yak S, et al. Overexpression of the
tumor suppressor gene phosphatase and tensin homologue partially
inhibits wnt-1-induced mammary tumorigenesis. Cancer Res 2005; 65:
6864-73.
68 Tanaka M, Grossman HB. In vivo gene therapy of
human bladder cancer with PTEN suppresses tumor growth,
downregulates phosphorylated Akt, and increases sensitivity to
doxorubicin. Gene Ther 2003; 10: 1636-42.
69 Kim HW, Park IK, Cho CS, Lee KH,
Beck Jr. GR, Colburn NH, et al. Aerosol
delivery of glucosylated polyethylenimine/phosphatase and tensin
homologue deleted on chromosome 10 complex suppresses Akt
downstream pathways in the lung of K-ras null mice. Cancer Res
2004; 64: 7971-6.
70 Saito Y, Swanson X, Mhashilkar AM,
Oida Y, Schrock R, Branch CD, et al.
Adenovirus-mediated transfer of the PTEN gene inhibits human
colorectal cancer growth in vitro and in vivo. Gene Ther 2003; 10:
1961-9.
71 Saito Y, Gopalan B, Mhashilkar AM,
Roth JA, Chada S, Zumstein, et al.
Adenovirus-mediated PTEN treatment combined with caffeine produces
a synergistic therapeutic effect in colorectal cancer cells. Cancer
Gene Ther 2003; 10: 803-13.
72 Jordan P, Brazao R, Boavida MG,
Gespach C, Chastre E, et al. Cloning of a novel
human Rac1b splice variant with increased expression in colorectal
tumors. Oncogene 1999; 18: 6835-9.
73 Cho YJ, Zhang B, Kaartinen V, Haataja L,
de Curtis I, Groffen J, et al. Generation of rac3
null mutant mice: role of Rac3 in Bcr/Abl-caused lymphoblastic
leukemia. Mol Cell Biol 2005; 25: 5777-85.
74 Kleer CG, Griffith KA, Sabel MS,
Gallagher G, van Golen KL, Wu ZF, et al.
RhoC-GTPase is a novel tissue biomarker associated with
biologically aggressive carcinomas of the breast. Breast Cancer Res
Treat 2005; 93: 101-10.
75 Ikoma T, Takahashi T, Nagano S, Li YM,
Ohno Y, Ando K, et al. A definitive role of RhoC in
metastasis of orthotopic lung cancer in mice. Clin Cancer Res 2004;
10: 1192-200.
76 Hakem A, Sanchez-Sweatman O, You-Ten A,
Duncan G, Wakeham A, Khokha R, et al. RhoC is
dispensable for embryogenesis and tumor initiation but essential
for metastasis. Genes Dev 2005; 19: 1974-9.
77 Preudhomme C, Roumier C, Hildebrand MP,
Dallery-Prudhomme E, Lantoine D, Lai JL, et al.
Nonrandom 4p13 rearrangements of the RhoH/TTF gene, encoding a
GTP-binding protein, in non-Hodgkin’s lymphoma and multiple
myeloma. Oncogene 2000; 19: 2023-32.
78 Gu Y, Jasti AC, Jansen M, Siefring JE,
et al. RhoH, a hematopoietic-specific Rho GTPase, regulates
proliferation, survival, migration, and engraftment of
hematopoietic progenitor cells. Blood 2005; 105: 1467-75.
79 Bi F, Debreceni B, Zhu K, Salani B,
Eva A, Zheng Y, et al. Autoinhibition mechanism of
proto-Dbl. Mol Cell Biol 2001; 21: 1463-74.
80 Chikumi H, Barac A, Behbahani B, Gao Y,
Teramoto H, Zheng Y, et al. Homo- and
hetero-oligomerization of PDZ-RhoGEF, LARG and p115RhoGEF by their
C-terminal region regulates their in vivo Rho GEF activity and
transforming potential. Oncogene 2004; 23: 233-40.
81 van Leeuwen FN, van der Kammen RA, Habets GG,
Collard JG, et al. Oncogenic activity of Tiam1 and Rac1
in NIH3T3 cells. Oncogene 1995; 11: 2215-21.
82 Fernandez-Zapico ME, Gonzalez-Paz NC, Weiss E,
Savoy DN, Molina JR, Fonseca R, et al. Ectopic
expression of VAV1 reveals an unexpected role in pancreatic cancer
tumorigenesis. Cancer Cell 2005; 7: 39-49.
83 Hornstein I, Pikarsky E, Groysman M,
Amir G, Peylan-Ramu N, Katzav S, et al. The
haematopoietic specific signal transducer Vav1 is expressed in a
subset of human neuroblastomas. J Pathol 2003; 199: 526-33.
84 Ahn SJ, Chung KW, Lee RA, Park IA,
Lee SH, Park DE, et al. Overexpression of betaPix-a
in human breast cancer tissues. Cancer Lett 2003; 193: 99-107.
85 Tyybakinoja A, Saarinen-Pihkala U, Elonen E,
Knu S, et al. Amplified, lost, and fused genes in
11q23-25 amplicon in acute myeloid leukemia, an array-CGH study.
Genes Chromosomes Cancer 2006; 45: 257-64.
86 Kourlas PJ, Strout MP, Becknell B,
Veronese ML, Croce CM, Theil KS, et al.
Identification of a gene at 11q23 encoding a guanine nucleotide
exchange factor: evidence for its fusion with MLL in acute myeloid
leukemia. Proc Natl Acad Sci USA 2000; 97: 2145-50.
87 Johansson FK, Brodd J, Eklof C,
Ferletta M, Hesselager G, Tiger, et al.
Identification of candidate cancer-causing genes in mouse brain
tumors by retroviral tagging. Proc Natl Acad Sci USA 2004; 101:
11334-7.
88 Johansson FK, Goransson H, Westermark B.
Expression analysis of genes involved in brain tumor progression
driven by retroviral insertional mutagenesis in mice. Oncogene
2005; 24: 3896-905.
89 Habets GG, Scholtes EH, Zuydgeest D, van der
Kammen RA, Stam JC, Berns A, et al.
Identification of an invasion-inducing gene, Tiam-1, that encodes a
protein with homology to GDP-GTP exchangers for Rho-like proteins.
Cell 1994; 77: 537-49.
90 Minard ME, Kim LS, Price JE, Gallick GE,
et al. The role of the guanine nucleotide exchange factor
Tiam1 in cellular migration, invasion, adhesion and tumor
progression. Breast Cancer Res Treat 2004; 84: 21-32.
91 Malliri A, van der Kammen RA, Clark K, van der
Valk M, Michiels F, Collard JG, et al. Mice
deficient in the Rac activator Tiam1 are resistant to Ras-induced
skin tumours. Nature 2002; 417: 867-71.
92 Linghu H, Tsuda M, Makino Y, Sakai M, Watanabe T, Ichihara,
et al. Involvement of adaptor protein Crk in malignant feature of
human ovarian cancer cell line MCAS. Oncogene 2006 (in press).
93 Buchsbaum RJ, Connolly BA, Feig LA.
Interaction of Rac exchange factors Tiam1 and Ras-GRF1 with a
scaffold for the p38 mitogen-activated protein kinase cascade. Mol
Cell Biol 2002; 22: 4073-85.
94 Innocenti M, Frittoli E, Ponzanelli I,
Falck JR, Brachmann SM, Di Fiore PP, et al.
Phosphoinositide 3-kinase activates Rac by entering in a complex
with Eps8, Abi1, and Sos-1. J Cell Biol 2003; 160: 17-23.
95 Schnelzer A, Prechtel D, Knaus U,
Dehne K, Gerhard M, Graeff, et al. Rac1 in human
breast cancer: overexpression, mutation analysis, and
characterization of a new isoform, Rac1b. Oncogene 2000; 19:
3013-20.
96 Liu SY, et al. Overexpression of Rac-1 small GTPase
binding protein in oral squamous cell carcinoma. J Oral Maxillofac
Surg 2004; 62: 702-7.
97 Matos P, Collard JG, Jordan P. Tumor-related
alternatively spliced Rac1b is not regulated by Rho-GDP
dissociation inhibitors and exhibits selective downstream
signaling. J Biol Chem 2003; 278: 50442-8.
98 Fritz G, Just I, Kaina B. Rho GTPases are
over-expressed in human tumors. Int J Cancer 1999; 81: 682-7.
99 Mira JP, Benard V, Groffen J, Sanders LC,
Knaus UG, et al. Endogenous, hyperactive Rac3 controls
proliferation of breast cancer cells by a p21-activated
kinase-dependent pathway. Proc Natl Acad Sci USA 2000; 97:
185-9.
100 Adamson P, Paterson HF, Hall A. Intracellular
localization of the P21rho proteins. J Cell Biol 1992; 119:
617-27.
101 Michaelson D, Silletti J, Murphy G,
D’Eustachio P, Rush M, Philips MR, et al.
Differential localization of Rho GTPases in live cells: regulation
by hypervariable regions and RhoGDI binding. J Cell Biol 2001; 152:
111-26.
102 Wang HR, Zhang Y, Ozdamar B,
Ogunjimi AA, Alexandrova E, Thomsen GH, et al.
Regulation of cell polarity and protrusion formation by targeting
RhoA for degradation. Science 2003; 302: 1775-9.
103 Abraham MT, Kuriakose MA, Sacks PG,
Yee H, Chiriboga L, Bearer EL, et al.
Motility-related proteins as markers for head and neck squamous
cell cancer. Laryngoscope 2001; 111: 1285-9.
104 Kamai T, Tsujii T, Arai K, Takagi K,
Asami H, Ito Y, et al. The rho/rho-kinase pathway is
involved in the progression of testicular germ cell tumour. BJU Int
2002; 89: 449-53.
105 Kamai T, Tsujii T, Arai K, Takagi K,
Asami H, Ito Y, et al. Significant association of
Rho/ROCK pathway with invasion and metastasis of bladder cancer.
Clin Cancer Res 2003; 9: 2632-41.
106 Ridley AJ. Rho proteins and cancer. Breast Cancer Res
Treat 2004; 84: 13-9.
107 Mazieres J, Antonia T, Daste G,
Muro-Cacho C, Berchery D, Tillement V, et al.
Loss of RhoB expression in human lung cancer progression. Clin
Cancer Res 2004; 10: 2742-50.
108 Shikada Y, Yoshino I, Okamoto T,
Fukuyama S, Kameyama T, Maehara Y, et al.
Higher expression of RhoC is related to invasiveness in non-small
cell lung carcinoma. Clin Cancer Res 2003; 9: 5282-6.
109 Ikoma T, Takahashi T, Nagano S, Li YM,
Ohno Y, Ando K, et al. A definitive role of RhoC in
metastasis of orthotopic lung cancer in mice. Clin Cancer Res 2004;
10: 1192-200.
110 Clark EA, Golub TR, Lander ES, Hynes RO,
et al. Genomic analysis of metastasis reveals an essential
role for RhoC. Nature 2000; 406: 532-5.
111 Bektic J, Pfeil K, Berger AP, Ramoner R,
Pelzer A, Schafer G, et al. Small G-protein RhoE is
underexpressed in prostate cancer and induces cell cycle arrest and
apoptosis. Prostate 2005; 64: 332-40.
112 Jiang WG, Watkins G, Lane J, Cunnick GH,
Douglas-Jones A, Mokbel K, et al. Prognostic value
of rho GTPases and rho guanine nucleotide dissociation inhibitors
in human breast cancers. Clin Cancer Res 2003; 9: 6432-40.
113 Pasqualucci L, Neumeister P, Goossens T,
Nanjangud G, Chaganti RS, Kuppers R, et al.
Hypermutation of multiple proto-oncogenes in B-cell diffuse
large-cell lymphomas. Nature 2001; 412: 341-6.
114 Wolf RM, Draghi N, Liang X, Dai C,
Uhrbom L, Eklof C, et al. p190RhoGAP can act to
inhibit PDGF-induced gliomas in mice: a putative tumor suppressor
encoded on human chromosome 19q13.3. Genes Dev 2003; 17:
476-87.
115 Wong CM, Lee JM, Ching YP, Jin DY,
Ng IO, et al. Genetic and epigenetic alterations of DLC-1
gene in hepatocellular carcinoma. Cancer Res 2003; 63: 7646-51.
116 Ching YP, Wong CM, Chan SF, Leung TH,
Ng DC, Jin JY, et al. Deleted in liver cancer (DLC)
2 encodes a RhoGAP protein with growth suppressor function and is
underexpressed in hepatocellular carcinoma. J Biol Chem 2003; 278:
10824-30.
117 Johnstone CN, Castellvi-Bel S, Chang LM,
Bessa X, Nakagawa H, Harada H, et al. ARHGAP8
is a novel member of the RHOGAP family related to
ARHGAP1/CDC42GAP/p50RHOGAP: mutation and expression analyses in
colorectal and breast cancers. Gene 2004; 336: 59-71.
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