Gene Summary

Gene:PAK4; p21 (RAC1) activated kinase 4
Summary:PAK proteins, a family of serine/threonine p21-activating kinases, include PAK1, PAK2, PAK3 and PAK4. PAK proteins are critical effectors that link Rho GTPases to cytoskeleton reorganization and nuclear signaling. They serve as targets for the small GTP binding proteins Cdc42 and Rac and have been implicated in a wide range of biological activities. PAK4 interacts specifically with the GTP-bound form of Cdc42Hs and weakly activates the JNK family of MAP kinases. PAK4 is a mediator of filopodia formation and may play a role in the reorganization of the actin cytoskeleton. Multiple alternatively spliced transcript variants encoding distinct isoforms have been found for this gene. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:serine/threonine-protein kinase PAK 4
Source:NCBIAccessed: 30 August, 2019


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 30 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 30 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: PAK4 (cancer-related)

Won SY, Park JJ, Shin EY, Kim EG
PAK4 signaling in health and disease: defining the PAK4-CREB axis.
Exp Mol Med. 2019; 51(2):11 [PubMed] Free Access to Full Article Related Publications
p21-Activated kinase 4 (PAK4), a member of the PAK family, regulates a wide range of cellular functions, including cell adhesion, migration, proliferation, and survival. Dysregulation of its expression and activity thus contributes to the development of diverse pathological conditions. PAK4 plays a pivotal role in cancer progression by accelerating the epithelial-mesenchymal transition, invasion, and metastasis. Therefore, PAK4 is regarded as an attractive therapeutic target in diverse types of cancers, prompting the development of PAK4-specific inhibitors as anticancer drugs; however, these drugs have not yet been successful. PAK4 is essential for embryonic brain development and has a neuroprotective function. A long list of PAK4 effectors has been reported. Recently, the transcription factor CREB has emerged as a novel effector of PAK4. This finding has broad implications for the role of PAK4 in health and disease because CREB-mediated transcriptional reprogramming involves a wide range of genes. In this article, we review the PAK4 signaling pathways involved in prostate cancer, Parkinson's disease, and melanogenesis, focusing in particular on the PAK4-CREB axis.

Brix DM, Tvingsholm SA, Hansen MB, et al.
Release of transcriptional repression via ErbB2-induced, SUMO-directed phosphorylation of myeloid zinc finger-1 serine 27 activates lysosome redistribution and invasion.
Oncogene. 2019; 38(17):3170-3184 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
HER2/ErbB2 activation turns on transcriptional processes that induce local invasion and lead to systemic metastasis. The early transcriptional changes needed for ErbB2-induced invasion are poorly understood. Here, we link ErbB2 activation to invasion via ErbB2-induced, SUMO-directed phosphorylation of a single serine residue, S27, of the transcription factor myeloid zinc finger-1 (MZF1). Utilizing an antibody against MZF1-pS27, we show that the phosphorylation of S27 correlates significantly (p < 0.0001) with high-level expression of ErbB2 in primary invasive breast tumors. Phosphorylation of MZF1-S27 is an early response to ErbB2 activation and results in increased transcriptional activity of MZF1. It is needed for the ErbB2-induced expression of MZF1 target genes CTSB and PRKCA, and invasion of single-cells from ErbB2-expressing breast cancer spheroids. The phosphorylation of MZF1-S27 is preceded by poly-SUMOylation of K23, which can make S27 accessible to efficient phosphorylation by PAK4. Based on our results, we suggest for an activation mechanism where phosphorylation of MZF1-S27 triggers MZF1 dissociation from its transcriptional repressors such as the CCCTC-binding factor (CTCF). Our findings increase understanding of the regulation of invasive signaling in breast cancer by uncovering a detailed biological mechanism of how ErbB2 activation can rapidly lead to its invasion-promoting target gene expression and invasion.

Liu Y, Jiao D, Tian Z
MicroRNA‑663 inhibits the proliferation and invasion of clear cell renal cell carcinoma cells by directly targeting PAK4.
Mol Med Rep. 2019; 19(1):711-718 [PubMed] Related Publications
Accumulating evidence has demonstrated that microRNAs (miRNAs) are key gene regulators and are abnormally expressed in clear cell renal cell carcinoma (ccRCC). The dysregulation of miRNAs has been implicated in the initiation and progression of ccRCC. Therefore, identification of ccRCC‑associated miRNAs may facilitate the determination of promising therapeutic targets for anti‑cancer treatment. In the present study, miRNA‑663 (miR‑663) expression was downregulated in ccRCC tissues and cell lines. Functional experiments suggested that restoration of miR‑663 expression inhibited the proliferation and invasion of ccRCC cells. In addition, p21 activated kinase 4 (PAK4) was validated as a direct target of miR‑663 in ccRCC cells. PAK4 was upregulated in ccRCC tissues, and the expression level of PAK4 was inversely correlated with the miR‑663 expression level. PAK4 restoration partially attenuated the suppressive roles of miR‑663 overexpression on the proliferation and invasion of ccRCC cells. The present results provide novel insight into the mechanism underlying the occurrence and development of ccRCC, suggesting that the miR‑663/PAK4 axis may be a novel therapeutic target for treatment of patients with ccRCC.

Park JJ, Park MH, Oh EH, et al.
The p21-activated kinase 4-Slug transcription factor axis promotes epithelial-mesenchymal transition and worsens prognosis in prostate cancer.
Oncogene. 2018; 37(38):5147-5159 [PubMed] Related Publications
Epithelial-mesenchymal transition (EMT) facilitates cancer invasion and metastasis and thus accelerates cancer progression. p21-activated kinase 4 (PAK4) is a critical regulator of prostate cancer (PC) progression. Here, we report that PAK4 activation promotes PC progression through the EMT regulator Slug. We find that phosphorylated PAK4

Rane CK, Minden A
P21 activated kinase signaling in cancer.
Semin Cancer Biol. 2019; 54:40-49 [PubMed] Related Publications
The p21 Activated Kinases (PAKs) are a family of serine threonine kinases, that consist of 6 members, PAKs 1-6, which are positioned at an intersection of multiple signaling pathways implicated in oncogenesis. The PAKs were originally identified as protein kinases that function downstream of the Ras related Rho GTPases Cdc42 and Rac. PAK1 and PAK4, which belong to Group I and Group II PAKs, respectively, are most often associated with tumorigenesis. On account of their well characterized roles in cancer, several small molecule inhibitors are being developed to inhibit the PAKs, and there is interest in investigating their efficacy as either first line or adjuvant treatments for cancer. Studies to delineate PAK regulated signaling pathways as well as the long term effects of PAK overexpression on gene expression are beginning to shed light on the mechanism by which PAK proteins may lead to cancer when they are overexpressed or activated. This review will describe the association between PAK expression in cancer, with a focus on PAK1 and PAK4, which are most often associated with the disease. The current understanding of the molecular mechanisms by which the PAKs operate in cancer will be discussed. We will also review some of the potential drug candidates, and discuss which of them are currently being tested for their efficacy in cancer treatments.

Zeng B, Shi W, Tan G
MiR-199a/b-3p inhibits gastric cancer cell proliferation via down-regulating PAK4/MEK/ERK signaling pathway.
BMC Cancer. 2018; 18(1):34 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
BACKGROUND: Gastric cancer (GC) is one of the most frequent malignant tumors and the molecular mechanism underlying its proliferation remains far from completely understood. Although accumulating evidence shows that abnormal expression of microRNA (miRNA) is involved in tumorigenesis, the role of specific miRNAs involved in GC remains elusive. MiR-199a/b-3p functions as a tumor suppressor in diverse cancers, but its expression, function, and mechanism in GC remain unclear. Our aim is to explore miR-199a/b-3p expression and its role in regulating GC cell proliferation.
METHODS: Real-time PCR was performed to determine miR-199a/b-3p expression in GC tissues and normal adjacent tissues as well as normal gastric mucosal cell line GES-1 and GC cell lines MGC-803 and SGC-7901. MTT assay and Western blot were performed to determine cell proliferation and expression of PAK4, p-MEK and p-ERK, respectively. MiR-199a/b-3p mimics-transfected assay and PAK-specific siRNA assay were performed to determine their function in cell proliferation, respectively. GC xenograft nude mice were used to determine miR-199a/b-3p function in cell proliferation.
RESULTS: MiR-199a/b-3p expression was significantly decreased in GC tissues and GC cell lines MGC-803 and SGC-7901. MiR-199a/b-3p over-expression and PAK4 silencing inhibited cell proliferation and diminished the activation of p-MEK and p-ERK in MGC-803 and SGC-7901 cells, and miR-199a/b-3p over-expression reduced PAK4 expression. MiR-199a/b-3p over-expression suppressed MGC-803 cell growth and PAK4 expression in nude mice.
CONCLUSIONS: miR-199a/b-3p inhibits GC cell proliferation via down-regulating PAK4/MEK/ERK signaling pathway and may be a novel prognostic biomarker and a potential therapeutic target for GC patients.

Cosset É, Ilmjärv S, Dutoit V, et al.
Glut3 Addiction Is a Druggable Vulnerability for a Molecularly Defined Subpopulation of Glioblastoma.
Cancer Cell. 2017; 32(6):856-868.e5 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
While molecular subtypes of glioblastoma (GBM) are defined using gene expression and mutation profiles, we identify a unique subpopulation based on addiction to the high-affinity glucose transporter, Glut3. Although Glut3 is a known driver of a cancer stem cell phenotype, direct targeting is complicated by its expression in neurons. Using established GBM lines and patient-derived stem cells, we identify a subset of tumors within the "proneural" and "classical" subtypes that are addicted to aberrant signaling from integrin αvβ3, which activates a PAK4-YAP/TAZ signaling axis to enhance Glut3 expression. This defined subpopulation of GBM is highly sensitive to agents that disrupt this pathway, including the integrin antagonist cilengitide, providing a targeted therapeutic strategy for this unique subset of GBM tumors.

Li Z, Li X, Xu L, et al.
Inhibition of neuroblastoma proliferation by PF-3758309, a small-molecule inhibitor that targets p21-activated kinase 4.
Oncol Rep. 2017; 38(5):2705-2716 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Neuroblastoma is the most common extracranial solid childhood tumor. Despite the availability of advanced multimodal therapy, high-risk patients still have low survival rates. p21-activated kinase 4 (PAK4) has been shown to regulate many cellular processes in cancer cells, including migration, polarization and proliferation. However, the role of PAK4 in neuroblastoma remains unclear. In the present study, we demonstrated that PAK4 was overexpressed in neuroblastoma tissues and was correlated with tumor malignance and prognosis. To investigate the function of PAK4 in neuroblastoma, we used a small-molecule inhibitor that targets PAK4, that is, PF-3758309. Our results showed that PF-3758309 significantly induced cell cycle arrest at the G1 phase and apoptosis in neuroblastoma cell lines. Meanwhile, the inhibition of PAK4 by PF-3758309 increased the expression of CDKN1A, BAD and BAK1 and decreased the expression of Bcl-2 and Bax. In addition, we screened the target genes of PAK4 by PCR array and found that 23 genes were upregulated (including TP53I3, TBX3, EEF1A2, CDKN1A, IFNB1 and MAPK8IP2) and 20 genes were downregulated (including TNFSF8, Bcl2-A1, Bcl2L1, SOCS3, BIRC3 and NFKB1) after PAK4 inhibition by PF-3758309. Moreover, PAK4 was found to regulate the cell cycle and apoptosis via the ERK signaling pathway. In conclusion, the present study demonstrated, for the first time, the expression and function of PAK4 in neuroblastomas and the inhibitory effect of PF-3758309, which deserves further investigation as an alternative strategy for neuroblastoma treatment.

Mao K, Lei D, Zhang H, You C
MicroRNA-485 inhibits malignant biological behaviour of glioblastoma cells by directly targeting PAK4.
Int J Oncol. 2017; 51(5):1521-1532 [PubMed] Related Publications
Glioblastoma (GBM), which is characterised by rapid growth, cellular heterogeneity, angiogenesis, extensive invasion, hypoxia and necrosis, is the most common histological subtype of glioma in adults. MicroRNA (miRNA) dysregulation is a common feature of human cancers, including GBM. Previous studies have suggested that miRNAs are a novel class of regulatory molecules in various human cancers. Therefore, miRNAs may be investigated as a novel candidate and screening tool in the clinical diagnosis, therapy and prognosis of GBM. Recent accumulating evidence has demonstrated that miRNA‑485 (miR‑485) is involved in the development and progression of several types of human cancers. However, the expression level, exact role and underlying mechanisms of miR‑485 in GBM remain unclear. In this study, miR‑485 was downregulated in both GBM tissue specimens and cell lines. miR‑485 overexpression inhibited GBM cell proliferation, colony formation, migration and invasion; increased apoptosis in vitro; and reduced tumour growth in vivo. In addition, p21‑activated kinase 4 (PAK4) was demonstrated to be a direct and functional target of miR‑485 in GBM. Furthermore, PAK4 was upregulated in GBM tissues and negatively correlated with miR‑485 expression. Moreover, PAK4 knockdown exhibited a similar effect to miR‑485 overexpression in GBM cells. Enforced expression of PAK4 rescued miR‑485 tumour‑suppressor functions in GBM cells. miR‑485 inhibited the activation of the AKT and ERK signalling pathways in GBM. These results indicate that miR‑485 acts as a tumour suppressor in GBM by, at least partially, directly targeting PAK4 and regulating the AKT and ERK signalling pathways. Thus, miR‑485 may be a potential target for the treatment of patients with GBM.

He W, Zhao Z, Anees A, et al.
p21-Activated Kinase 4 Signaling Promotes Japanese Encephalitis Virus-Mediated Inflammation in Astrocytes.
Front Cell Infect Microbiol. 2017; 7:271 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Japanese encephalitis virus (JEV) targets central nervous system, resulting in neuroinflammation with typical features of neuronal death along with hyper activation of glial cells. Exploring the mechanisms responsible for the JEV-caused inflammatory response remains a pivotal area of research. In the present study, we have explored the function of p21-activated kinase 4 (PAK4) in JEV-mediated inflammatory response in human astrocytes. The results showed that JEV infection enhances the phosphorylation of PAK4 in U251 cells and mouse brain. Knockdown of PAK4 resulted in decreased expression of inflammatory cytokines that include tumor necrosis factor alpha, interleukin-6, interleukin-1β, and chemokine (C-C motif) ligand 5 and interferon β upon JEV infection, suggesting that PAK4 signaling promotes JEV-mediated inflammation. In addition, we found that knockdown of PAK4 led to the inhibition of MAPK signaling including ERK, p38 MAPK and JNK, and also resulted in the reduced nuclear translocation of NF-κB and phosphorylation of AP-1. These results demonstrate that PAK4 signaling actively promotes JEV-mediated inflammation in human astrocytes via MAPK-NF-κB/AP-1 pathway, which will provide a new insight into the molecular mechanism of the JEV-induced inflammatory response.

Lu X, Wang H, Su Z, et al.
MicroRNA-342 inhibits the progression of glioma by directly targeting PAK4.
Oncol Rep. 2017; 38(2):1240-1250 [PubMed] Related Publications
Glioma is an extremely aggressive and lethal type of brain tumour that originates from glial cells. MicroRNA (miRNA) dysregulation has been implicated in the occurrence and progression of many human cancers, including glioma. Thus, some specific miRNAs are potential therapeutic targets for glioma diagnosis, therapy and prognosis. MicroRNA-342 (miR‑342) has been reported to be abnormally expressed in various types of cancer. However, the precise roles of miR‑342 in glioma remain unknown. The present study showed that miR‑342 is relatively downregulated in glioma tissues and cell lines compared with that in adjacent normal tissues and normal human astrocytes. We observed that low miR‑342 expression levels are correlated with advanced WHO grades and low KPS scores of glioma patients. In addition, the results of the functional assays demonstrated that miR‑342 overexpression inhibits the proliferation and invasion of glioma cells and induces apoptosis. Further investigation revealed that P21 activated kinases 4 (PAK4) is a direct target of miR‑342 in glioma. PAK4 was significantly upregulated in glioma tissues and inversely correlated with miR‑342 expression. Moreover, PAK4 knockdown can mimic the effects of miR‑342 on glioma cell proliferation, invasion and apoptosis. Notably, restoration of expression of PAK4 reversed the suppressive effects induced by the miR‑342 in the glioma cells. The upregulation of miR‑342 inactivated the AKT and ERK pathways in glioma. These findings may contribute to the understanding of the molecular mechanism underlying the carcinogenesis and progression of glioma, and to provide novel therapeutic target for the treatment of glioma patients.

Lu SX, Zhang CZ, Luo RZ, et al.
Zic2 promotes tumor growth and metastasis via PAK4 in hepatocellular carcinoma.
Cancer Lett. 2017; 402:71-80 [PubMed] Related Publications
The dysregulation of transcription factors contributes to the unlimited growth of cancer cells. Zic2 has been shown to be crucial to the progression of human cancers. However, its role in hepatocellular carcinoma (HCC) remains unclear. Our data showed that Zic2 expression gradually increased from normal to cancer to metastatic tissues. Zic2 overexpression promoted, whereas Zic2 knockdown inhibited, cell proliferation and migration in vitro as well as tumor growth and metastasis in vivo. Gene microarray results indicated that PAK4 was a potential target of Zic2. The knockdown of Zic2 decreased, whereas Zic2 re-expression increased, the expression of PAK4. ChIP and luciferase assays indicated that Zic2 directly bound to the PAK4 promoter and modulated its activity. PAK4 interference attenuated Zic2-mediated cell growth via modulating the Raf/MEK/ERK pathway. In a cohort of 615 patients, Zic2 was positively correlated with PAK4 and associated with worse overall and disease-free survival. Multivariate analyses revealed that Zic2 and PAK4 were independent indicators of a poor outcome in HCC. In addition, Zic2 expression was inversely correlated with miR-1271 expression. Re-introduction of miR-1271 attenuated Zic2-promoted cell proliferation and migration. Taken together, our findings suggest that the newly identified miR-1271/Zic2/PAK4 axis plays an important role in HCC progression and may serve as a potential therapeutic target for HCC.

Kesanakurti D, Maddirela D, Banasavadi-Siddegowda YK, et al.
A novel interaction of PAK4 with PPARγ to regulate Nox1 and radiation-induced epithelial-to-mesenchymal transition in glioma.
Oncogene. 2017; 36(37):5309-5320 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Tumor recurrence in glioblastoma (GBM) is, in part, attributed to increased epithelial-to-mesenchymal transition (EMT) and enhanced tumor cell dissemination in adjacent brain parenchyma after ionizing radiation (IR). EMT is associated with aggressive behavior, increased stem-like characteristics and treatment resistance in malignancies; however, the underlying signaling mechanisms that regulate EMT are poorly understood. We identified grade-dependent p21-activated kinases 4 (PAK4) upregulation in gliomas and further determined its role in mesenchymal transition and radioresistance. IR treatment significantly elevated expression and nuclear localization of PAK4 in correlation with induction of reactive oxygen species (ROS) and mesenchymal transition in GBM cells. Stable PAK4 overexpression promoted mesenchymal transition by elevating EMT marker expression in these cells. Of note, transcription factor-DNA-binding arrays and chromatin immunoprecipitation experiments identified the formation of a novel nuclear PAK4/PPARγ complex which was recruited to the promoter of Nox1, a peroxisome proliferator-activated receptor gamma (PPARγ) target gene. In addition, IR further elevated PAK4/PPARγ complex co-recruitment to Nox1 promoter, and increased Nox1 expression and ROS levels associated with mesenchymal transition in these cells. Conversely, specific PAK4 downregulation decreased PPARγ-mediated Nox1 expression and suppressed EMT in IR-treated cells. In vivo orthotopic tumor experiments showed inhibition of growth and suppression of IR-induced PPARγ and Nox1 expression by PAK4 downregulation in tumors. Our results provide the first evidence of a novel role for PAK4 in IR-induced EMT and suggest potential therapeutic efficacy of targeting PAK4 to overcome radioresistance in gliomas.

Brown AL, Foster KL, Lupo PJ, et al.
DNA methylation of a novel PAK4 locus influences ototoxicity susceptibility following cisplatin and radiation therapy for pediatric embryonal tumors.
Neuro Oncol. 2017; 19(10):1372-1379 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Background: Ototoxicity is a common adverse side effect of platinum chemotherapy and cranial radiation therapy; however, individual susceptibility is highly variable. Therefore, our objective was to conduct an epigenome-wide association study to identify differentially methylated cytosine-phosphate-guanine (CpG) sites associated with ototoxicity susceptibility among cisplatin-treated pediatric patients with embryonal tumors.
Methods: Samples were collected for a discovery cohort (n = 62) and a replication cohort (n = 18) of medulloblastoma and primitive neuroectodermal tumor patients. Posttreatment audiograms were evaluated using the International Society of Paediatric Oncology (SIOP) Boston Ototoxicity Scale. Genome-wide associations between CpG methylation and ototoxicity were examined using multiple linear regression, controlling for demographic and treatment factors.
Results: The mean cumulative dose of cisplatin was 330 mg/m2 and the mean time from end of therapy to the last available audiogram was 6.9 years. In the discovery analysis of 435233 CpG sites, 6 sites were associated with ototoxicity grade (P < 5 × 10-5) after adjusting for confounders. Differential methylation at the top CpG site identified in the discovery cohort (cg14010619, PAK4 gene) was replicated (P = 0.029) and reached genome-wide significance (P = 2.73 × 10-8) in a combined analysis. These findings were robust to a sensitivity analysis evaluating other potential confounders.
Conclusions: We identified and replicated a novel CpG methylation loci (cg14010619) associated with ototoxicity severity. Methylation at cg14010619 may modify PAK4 activity, which has been implicated in cisplatin resistance in malignant cell lines.

He LF, Xu HW, Chen M, et al.
Activated-PAK4 predicts worse prognosis in breast cancer and promotes tumorigenesis through activation of PI3K/AKT signaling.
Oncotarget. 2017; 8(11):17573-17585 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
The p21-activated kinase 4 (PAK4) is sufficient to transform noncancerous mammary epithelial cells and to form tumors in the mammary glands of mice. The accumulated information suggests that PAK4 might be an oncogenic protein in breast cancer. In this study, we sought to identify the role for PAK4 in breast cancer progression. Immunohistochemical study revealed that high PAK4 expression is associated with larger tumor size, lymph node metastasis, and advanced stage cancer in 93 invasive breast carcinoma patients. Moreover, high PAK4 expression was significantly associated with poor overall and disease-free survival. PAK4 remained an independent adverse prognosticator after univariate and multivariate analysis. Ectopic expression of wild-type PAK4 in MDA-MB-231 cells activated PI3K/AKT signaling and resulted in the enhancement of the cell proliferation, migration, and invasion, whereas PAK4-induced effects were blocked by the PAK4 kinase inhibitor PF- 3758309, PAK4 siRNAs or the PI3K inhibitor LY294002. Furthermore, a kinase-active PAK4 (S474E) strongly induced PI3K/AKT activation, and promoted proliferation, migration and invasion in breast cancer cells. A kinase-inactive PAK4 KD (K350A/K351A) did partially upregulate PI3K/AKT, and promoted invasive phenotype. Taken together, these findings suggest that PAK4-activated PI3K/AKT signaling is both kinase-dependent and -independent, which contributes to breast cancer progression. Thus, our results imply that dual inhibition of PAK4 and PI3K/AKT signaling might be a potential therapeutic approach for breast cancer therapy.

King H, Thillai K, Whale A, et al.
PAK4 interacts with p85 alpha: implications for pancreatic cancer cell migration.
Sci Rep. 2017; 7:42575 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
It has been reported that p21-activated kinase 4 (PAK4) is amplified in pancreatic cancer tissue. PAK4 is a member of the PAK family of serine/threonine kinases, which act as effectors for several small GTPases, and has been specifically identified to function downstream of HGF-mediated c-Met activation in a PI3K dependent manner. However, the functionality of PAK4 in pancreatic cancer and the contribution made by HGF signalling to pancreatic cancer cell motility remain to be elucidated. We now find that elevated PAK4 expression is coincident with increased expression levels of c-Met and the p85α subunit of PI3K. Furthermore, we demonstrate that pancreatic cancer cells have a specific motility response to HGF both in 2D and 3D physiomimetic organotypic assays; which can be suppressed by inhibition of PI3K. Significantly, we report a specific interaction between PAK4 and p85α and find that PAK4 deficient cells exhibit a reduction in Akt phosphorylation downstream of HGF signalling. These results implicate a novel role for PAK4 within the PI3K pathway via interaction with p85α. Thus, PAK4 could be an essential player in PDAC progression representing an interesting therapeutic opportunity.

Rane C, Senapedis W, Baloglu E, et al.
A novel orally bioavailable compound KPT-9274 inhibits PAK4, and blocks triple negative breast cancer tumor growth.
Sci Rep. 2017; 7:42555 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Breast cancer is a heterogeneous disease consisting of several subtypes. Among these subtypes, triple negative breast cancer is particularly difficult to treat. This is due to a lack of understanding of the mechanisms behind the disease, and consequently a lack of druggable targets. PAK4 plays critical roles in cell survival, proliferation, and morphology. PAK4 protein levels are high in breast cancer cells and breast tumors, and the gene is often amplified in basal like breast cancers, which are frequently triple negative. PAK4 is also overexpressed in other types of cancer, making it a promising drug target. However, its inhibition is complicated by the fact that PAK4 has both kinase-dependent and -independent functions. Here we investigate a new clinical compound KPT-9274, which has been shown to inhibit PAK4 and NAMPT. We find that KPT-9274 (and its analog, KPT-8752) can reduce the steady state level of PAK4 protein in triple negative breast cancer cells. These compounds also block the growth of the breast cancer cells in vitro, and stimulate apoptosis. Most importantly, oral administration of KPT-9274 reduces tumorigenesis in mouse models of human triple negative breast cancer. Our results indicate that KPT-9274 is a novel therapeutic option for triple negative breast cancer therapy.

Fulciniti M, Martinez-Lopez J, Senapedis W, et al.
Functional role and therapeutic targeting of p21-activated kinase 4 in multiple myeloma.
Blood. 2017; 129(16):2233-2245 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Dysregulated oncogenic serine/threonine kinases play a pathological role in diverse forms of malignancies, including multiple myeloma (MM), and thus represent potential therapeutic targets. Here, we evaluated the biological and functional role of p21-activated kinase 4 (PAK4) and its potential as a new target in MM for clinical applications. PAK4 promoted MM cell growth and survival via activation of MM survival signaling pathways, including the MEK-extracellular signal-regulated kinase pathway. Furthermore, treatment with orally bioavailable PAK4 allosteric modulator (KPT-9274) significantly impacted MM cell growth and survival in a large panel of MM cell lines and primary MM cells alone and in the presence of bone marrow microenvironment. Intriguingly, we have identified FGFR3 as a novel binding partner of PAK4 and observed significant activity of KPT-9274 against t(4;14)-positive MM cells. This set of data supports PAK4 as an oncogene in myeloma and provide the rationale for the clinical evaluation of PAK4 modulator in myeloma.

Aboukameel A, Muqbil I, Senapedis W, et al.
Novel p21-Activated Kinase 4 (PAK4) Allosteric Modulators Overcome Drug Resistance and Stemness in Pancreatic Ductal Adenocarcinoma.
Mol Cancer Ther. 2017; 16(1):76-87 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
The p21-activated kinase 4 (PAK4) is a key downstream effector of the Rho family GTPases and is found to be overexpressed in pancreatic ductal adenocarcinoma (PDAC) cells but not in normal human pancreatic ductal epithelia (HPDE). Gene copy number amplification studies in PDAC patient cohorts confirmed PAK4 amplification making it an attractive therapeutic target in PDAC. We investigated the antitumor activity of novel PAK4 allosteric modulators (PAM) on a panel of PDAC cell lines and chemotherapy-resistant flow-sorted PDAC cancer stem cells (CSC). The toxicity and efficacy of PAMs were evaluated in multiple subcutaneous mouse models of PDAC. PAMs (KPT-7523, KPT-7189, KPT-8752, KPT-9307, and KPT-9274) show antiproliferative activity in vitro against different PDAC cell lines while sparing normal HPDE. Cell growth inhibition was concurrent with apoptosis induction and suppression of colony formation in PDAC. PAMs inhibited proliferation and antiapoptotic signals downstream of PAK4. Co-immunoprecipitation experiments showed disruption of PAK4 complexes containing vimentin. PAMs disrupted CSC spheroid formation through suppression of PAK4. Moreover, PAMs synergize with gemcitabine and oxaliplatin in vitro KPT-9274, currently in a phase I clinical trial (; NCT02702492), possesses desirable pharmacokinetic properties and is well tolerated in mice with the absence of any signs of toxicity when 200 mg/kg daily is administered either intravenously or orally. KPT-9274 as a single agent showed remarkable antitumor activity in subcutaneous xenograft models of PDAC cell lines and CSCs. These proof-of-concept studies demonstrated the antiproliferative effects of novel PAMs in PDAC and warrant further clinical investigations. Mol Cancer Ther; 16(1); 76-87. ©2016 AACR.

Kumar R, Sanawar R, Li X, Li F
Structure, biochemistry, and biology of PAK kinases.
Gene. 2017; 605:20-31 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
PAKs, p21-activated kinases, play central roles and act as converging junctions for discrete signals elicited on the cell surface and for a number of intracellular signaling cascades. PAKs phosphorylate a vast number of substrates and act by remodeling cytoskeleton, employing scaffolding, and relocating to distinct subcellular compartments. PAKs affect wide range of processes that are crucial to the cell from regulation of cell motility, survival, redox, metabolism, cell cycle, proliferation, transformation, stress, inflammation, to gene expression. Understandably, their dysregulation disrupts cellular homeostasis and severely impacts key cell functions, and many of those are implicated in a number of human diseases including cancers, neurological disorders, and cardiac disorders. Here we provide an overview of the members of the PAK family and their current status. We give special emphasis to PAK1 and PAK4, the prototypes of groups I and II, for their profound roles in cancer, the nervous system, and the heart. We also highlight other family members. We provide our perspective on the current advancements, their growing importance as strategic therapeutic targets, and our vision on the future of PAKs.

Thillai K, Lam H, Sarker D, Wells CM
Deciphering the link between PI3K and PAK: An opportunity to target key pathways in pancreatic cancer?
Oncotarget. 2017; 8(8):14173-14191 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
The development of personalised therapies has ushered in a new and exciting era of cancer treatment for a variety of solid malignancies. Yet pancreatic ductal adenocarcinoma (PDAC) has failed to benefit from this paradigm shift, remaining notoriously refractory to targeted therapies. Chemotherapy is the cornerstone of management but can offer only modest survival benefits of a few months with 5-year survival rates rarely exceeding 3%. Despite these disappointing statistics, significant strides have been made towards understanding the complex biology of pancreatic cancer, with deep genomic sequencing identifying novel genetic aberrations and key signalling pathways. The PI3K-PDK1-AKT pathway has received great attention due to its prominence in carcinogenesis. However, efforts to target several components of this network have resulted in only a handful of drugs demonstrating any survival benefit in solid tumors; despite promising pre-clinical results. p-21 activated kinase 4 (PAK4) is a gene that is recurrently amplified or overexpressed in PDAC and both PAK4 and related family member PAK1, have been linked to aberrant RAS activity, a common feature in pancreatic cancer. As regulators of PI3K, PAKs have been highlighted as a potential prognostic marker and therapeutic target. In this review, we discuss the biology of pancreatic cancer and the close interaction between PAKs and the PI3K pathway. We also suggest proposals for future research that may see the development of effective targeted therapies that could finally improve outcomes for this disease.

Yang MQ, Elnitski L
A Systems Biology Comparison of Ovarian Cancers Implicates Putative Somatic Driver Mutations through Protein-Protein Interaction Models.
PLoS One. 2016; 11(10):e0163353 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Ovarian carcinomas can be aggressive with a high mortality rate (e.g., high-grade serous ovarian carcinomas, or HGSOCs), or indolent with much better long-term outcomes (e.g., low-malignant-potential, or LMP, serous ovarian carcinomas). By comparing LMP and HGSOC tumors, we can gain insight into the mechanisms underlying malignant progression in ovarian cancer. However, previous studies of the two subtypes have been focused on gene expression analysis. Here, we applied a systems biology approach, integrating gene expression profiles derived from two independent data sets containing both LMP and HGSOC tumors with protein-protein interaction data. Genes and related networks implicated by both data sets involved both known and novel disease mechanisms and highlighted the different roles of BRCA1 and CREBBP in the two tumor types. In addition, the incorporation of somatic mutation data revealed that amplification of PAK4 is associated with poor survival in patients with HGSOC. Thus, perturbations in protein interaction networks demonstrate differential trafficking of network information between malignant and benign ovarian cancers. The novel network-based molecular signatures identified here may be used to identify new targets for intervention and to improve the treatment of invasive ovarian cancer as well as early diagnosis.

Zhong N, Shi S, Wang H, et al.
Silencing Aurora-A with siRNA inhibits cell proliferation in human lung adenocarcinoma cells.
Int J Oncol. 2016; 49(3):1028-38 [PubMed] Related Publications
Aurora kinase A (AURKA) is an oncogenic serine/threonine kinase, it plays important roles in tumorigenesis and chemoresistance. In this study, we investigated the expression of AURKA in lung adenocarcinoma tissues, the role of small interference RNA targeting AURKA on growth, cell cycle, and apoptosis of lung adenocarcinoma cell lines in vitro. The AURKA is highly expressed in lung adenocarcinoma tissues and human lung adenocarcinoma cell lines. Lentivirus-mediated short hairpin RNA (shRNA) was used to knock down AURKA expression in human lung adenocarcinoma cell lines H1299 and A549. The results indicated that depletion of AURKA could inhibit cell growth, cause cell cycle arrest and apoptosis. The potential mechanisms of AURKA inhibition induced cell cycle arrest and apoptosis are associated with downregulated RAF-1, CCND2, CCND3, CDK4, PAK4, EGFR and upregulated WEE1 expression. Furthermore, AURKA knockdown cooperated with vincristine (VCR) to repress A549 cell proliferation. Therefore, AURKA plays important roles in the proliferation of human lung adenocarcinoma cells, which suggests that AURKA could be a promising tool for lung adenocarcinoma therapy.

Xia M, Wei J, Tong K
MiR-224 promotes proliferation and migration of gastric cancer cells through targeting PAK4.
Pharmazie. 2016; 71(8):460-464 [PubMed] Related Publications
Although recent studies have shown the important role and overexpression of miR-224 in several tumors, its function in gastric cancer has not yet been defined. In the present study, we tried to confirm the result of microRNAs microarray and further investigated the functions of miR-224 in gastric cancer, and tried to find new downstream targets of miR-224. In this study, the level of miR-224 was measured in gastric cancer cells with the normal human gastric epithelial cell. The effects of miR-224 of on proliferation, migration, and target protein expression were evaluated by CCK8 assay, colony assay, transwell migration assay, western blotting. In addition, luciferase reporter plasmid was constructed to demonstrate the direct target of miR-224. Overexpression of miR-224 was detected in the gastric cancer cells, especially in SCG-7901. Exogenous miR-224 expression promoted the proliferation and migration of gastric cells and abrogating expression of miR-224 suppressed proliferation, and migration of SCG-7901 cells in vitro. Luciferase assays revealed that miR-224 directly targeted the 3'UTR of p21-activated kinase 4 (PAK4). The present study provides an experimental foundation for miR-224 as a potential tumor suppressor that may decrease PAK4 expression to inhibit gastric cancer cells and that in the future, targeting of this miRNA may provide a novel strategy for the diagnosis and treatment of patients with this lethal disease.

Sanlorenzo M, Vujic I, Posch C, et al.
Oncogenic KIT mutations in different exons lead to specific changes in melanocyte phospho-proteome.
J Proteomics. 2016; 144:140-7 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
UNLABELLED: Mutations in the proto-oncogene c-KIT (KIT) are found in several cancers, and the site of these mutations differs markedly between cancer types. We used site directed mutagenesis to induce KIT(559), KIT(642) and KIT(816) mutations in primary human melanocytes (PHM) and we investigated the impact of each mutation on KIT function. We studied canonical KIT-signaling pathways by immunoblotting, and we used stable isotope labeling by amino acids in cell culture (SILAC) and kinase prediction models to identify kinases differently activated in respective mutants. We validated our results with the analysis of phosphorylation levels of selected substrates for each kinase. We concluded that CK1 ε and δ are more active in cell clones harboring KIT(559) and KIT(642) mutations, whereas PAK4 is more active in clones with KIT(816) mutation. Our findings might help to develop further therapeutic options for tumors with specific KIT mutations in different domains.
BIOLOGICAL SIGNIFICANCE: Different types of cancers harbor mutations in the oncogene KIT. The use of small molecules inhibitors directly targeting KIT had a limited success in the treatment of patients with KIT mutant cancers. Our study describes specific phospho-proteome changes due to different KIT mutations, and provides targets of further therapeutic options.

Jiang YY, Lin DC, Mayakonda A, et al.
Targeting super-enhancer-associated oncogenes in oesophageal squamous cell carcinoma.
Gut. 2017; 66(8):1358-1368 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
OBJECTIVES: Oesophageal squamous cell carcinoma (OSCC) is an aggressive malignancy and the major histological subtype of oesophageal cancer. Although recent large-scale genomic analysis has improved the description of the genetic abnormalities of OSCC, few targetable genomic lesions have been identified, and no molecular therapy is available. This study aims to identify druggable candidates in this tumour.
DESIGN: High-throughput small-molecule inhibitor screening was performed to identify potent anti-OSCC compounds. Whole-transcriptome sequencing (RNA-Seq) and chromatin immunoprecipitation sequencing (ChIP-Seq) were conducted to decipher the mechanisms of action of CDK7 inhibition in OSCC. A variety of in vitro and in vivo cellular assays were performed to determine the effects of candidate genes on OSCC malignant phenotypes.
RESULTS: The unbiased high-throughput small-molecule inhibitor screening led us to discover a highly potent anti-OSCC compound, THZ1, a specific CDK7 inhibitor. RNA-Seq revealed that low-dose THZ1 treatment caused selective inhibition of a number of oncogenic transcripts. Notably, further characterisation of the genomic features of these THZ1-sensitive transcripts demonstrated that they were frequently associated with super-enhancer (SE). Moreover, SE analysis alone uncovered many OSCC lineage-specific master regulators. Finally, integrative analysis of both THZ1-sensitive and SE-associated transcripts identified a number of novel OSCC oncogenes, including PAK4, RUNX1, DNAJB1, SREBF2 and YAP1, with PAK4 being a potential druggable kinase.
CONCLUSIONS: Our integrative approaches led to a catalogue of SE-associated master regulators and oncogenic transcripts, which may significantly promote both the understanding of OSCC biology and the development of more innovative therapies.

Zhang J, Zhang HY, Wang J, et al.
GL-1196 Suppresses the Proliferation and Invasion of Gastric Cancer Cells via Targeting PAK4 and Inhibiting PAK4-Mediated Signaling Pathways.
Int J Mol Sci. 2016; 17(4):470 [PubMed] Article available free on PMC after 01/10/2019 Related Publications
Gastric cancer, which is the most common malignant gastrointestinal tumor, has jumped to the third leading cause of cancer-related mortality worldwide. It is of great importance to identify novel and potent drugs for gastric cancer treatment. P21-activated kinase 4 (PAK4) has emerged as an attractive target for the development of anticancer drugs in consideration of its vital functions in tumorigenesis and progression. In this paper, we reported that GL-1196, as a small molecular compound, effectively suppressed the proliferation of human gastric cancer cells through downregulation of PAK4/c-Src/EGFR/cyclinD1 pathway and CDK4/6 expression. Moreover, GL-1196 prominently inhibited the invasion of human gastric cancer cells in parallel with blockage of the PAK4/LIMK1/cofilin pathway. Interestingly, GL-1196 also inhibited the formation of filopodia and induced cell elongation in SGC7901 and BGC823 cells. Taken together, these results provided novel insights into the potential therapeutic strategy for gastric cancer.

Guo B, Li X, Song S, et al.
(-)-β-hydrastine suppresses the proliferation and invasion of human lung adenocarcinoma cells by inhibiting PAK4 kinase activity.
Oncol Rep. 2016; 35(4):2246-56 [PubMed] Related Publications
(-)-β-hydrastine is one of the main active components of the medicinal plant, Hydrastis canadensis, which is used in many dietary supplements intended to enhance the immune system. However, whether (-)-β-hydrastine affects the tumor signaling pathway remains unexplored. In the present study, we found that (-)-β-hydrastine inhibited the kinase activity of p21-activated kinase 4 (PAK4), which is involved in the regulation of cytoskeletal reorganization, cell proliferation, gene transcription, oncogenic transformation and cell invasion. In the present study, (-)-β-hydrastine suppressed lung adenocarcinoma cell proliferation by inhibiting expression of cyclin D1/D3 and CDK2/4/6, leading to cell cycle arrest at the G1 phase, in a PAK4 kinase-dependent manner. Moreover, inhibition of PAK4 kinase activity by (-)-β-hydrastine also promoted the early apoptosis of lung adenocarcinoma cells through the mitochondrial apoptosis pathway. In addition, (-)-β-hydrastine significantly suppressed the migration and invasion of human lung adenocarcinoma cells in conjunction with concomitant blockage of the PAK4/LIMK1/cofilin, PAK4/SCG10 and PAK4/MMP2 pathways. All of these data indicate that (-)-β-hydrastine, as a novel PAK4 inhibitor, suppresses the proliferation and invasion of lung adenocarcinoma cells. Taken together, these results provide novel insight into the development of a PAK4 kinase inhibitor and a potential therapeutic strategy for lung cancer.

Wang X, Lu Y, Feng W, et al.
A two kinase-gene signature model using CDK2 and PAK4 expression predicts poor outcome in non-small cell lung cancers.
Neoplasma. 2016; 63(2):322-9 [PubMed] Related Publications
Risk classification on the basis of specific genomic features can lead to more precise tailoring of treatment for cancer patients. Kinases are potential therapeutic targets and survival factors, but the predictive prognostic potentials of multi-kinase genes have seldom been investigated. In this study, with publicly available microarray data of non-small cell lung cancers (NSCLC), we identified two kinase genes cyclin-dependent kinase 2 (CDK2) and p21 protein (Cdc42/Rac)-activated kinase 4 (PAK4) significantly associated with poor outcome. Then we present a combined gene signature model using CDK2 and PAK4 that can stratify disease poor outcome independently of standard clinical prognostic factors. Next, the predictive robustness of this 2-gene classifier was in silico confirmed in an independent microarray dataset, and experimentally validated in a lung cancer cohort by immunohistochemistry. Therefore, in this study, we demonstrated that the CDK2-PAK4 kinase signature may be a useful prognostic indicator and potential target for NSCLC. We also propose that poor outcome subgroup stratified by this classifier may benefit from the recently developed CDK2 and PAK4 inhibitors.

Kobayashi K, Inokuchi M, Takagi Y, et al.
Prognostic significance of PAK4 expression in gastric cancer.
J Clin Pathol. 2016; 69(7):580-5 [PubMed] Related Publications
AIMS: p-21 activated kinase (PAK) 4, part of the six PAK families, plays an important role in growth factor signalling, cytoskeletal remodelling, gene transcription, cell proliferation and oncogenic transformation. However, the clinical significance of PAK4 in gastric cancer has yet to be fully elucidated. PAK4 expression was evaluated, and the correlations of PAK4 expression with clinicopathological features and outcomes in gastric cancer were examined.
METHODS: Gastric adenocarcinomas obtained from 217 patients who underwent gastrectomy were analysed. PAK4 expression was evaluated using immunohistochemical staining.
RESULTS: PAK4 overexpression was found in 95 (43.8%) of 217 tumours . High PAK4 expression was significantly correlated with clinicopathological variables related to tumour progression, including depth of invasion, metastatic lymph nodes, pathological stage, distant metastasis or recurrent disease. High PAK4 expression was significantly associated with poorer disease-specific survival (DSS) (p<0.001) and relapse-free survival (RFS) (p<0.001). On multivariable analysis, PAK4 was an independent prognostic factor for DSS (HR 2.5 (95% CI 1.4 to 4.7), p=0.003) and RFS (HR 2.8 (95% CI 1.4 to 5.6), p=0.004). Even in stage II and III disease, PAK4 was an independent prognostic factor for RFS (HR 2.2 (95% CI 1.1 to 4.5), p=0.029).
CONCLUSIONS: PAK4 may become a new prognostic factor in patients with gastric cancer.

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