Prognostic significance of PAK4 expression in gastric cancer

Expression Patterns of PAK4 and PHF8 Are Associated with the Survival of Gallbladder Carcinoma Patients

Background: PAK4 and PHF8 are involved in cancer progression and are under evaluation as targets for cancer therapy. However, despite extensive studies in human cancers, there are limited reports on the roles of PAK4 and PHF8 in gallbladder cancers. Methods: Immunohistochemical expression of PAK4 and PHF8 and their prognostic significance were evaluated in 148 human gallbladder carcinomas. Results: PAK4 expression was significantly associated with PHF8 expression in gallbladder carcinomas. Positive expression of nuclear PAK4, cytoplasmic PAK4, nuclear PHF8, and cytoplasmic PHF8 were significantly associated with shorter overall survival and relapse-free survival in univariate analysis. Multivariate analysis showed that nuclear PAK4 expression and nuclear PHF8 expression were independent predictors of overall survival and relapse-free survival in gallbladder carcinomas. Furthermore, coexpression of nuclear PAK4 and nuclear PHF8 predicted shorter overall survival (p < 0.001) and relapse-free survival (p < 0.001) of gallbladder carcinoma in multivariate analysis. Conclusions: This study suggests that the individual and coexpression patterns of PAK4 and PHF8 as the prognostic indicators for gallbladder carcinoma patients.

p21-Activated Kinase: Role in Gastrointestinal Cancer and Beyond

Simple Summary

Gastrointestinal tumors are the most common tumors with a high mortality rate worldwide. Numerous protein kinases have been studied in anticipation of finding viable tumor therapeutic targets, including PAK. PAK is a serine/threonine kinase that plays an important role in the malignant phenotype of tumors. The function of PAK in tumors is highlighted in cell proliferation, survival, motility, tumor cell plasticity and the tumor microenvironment, therefore providing a new possible target for clinical tumor therapy. Based on the current research works of PAK, we summarize and analyze the PAK features and signaling pathways in cells, especially the role of PAK in gastrointestinal tumors, thereby hoping to provide a theoretical basis for both the future studies of PAK and potential tumor therapeutic targets.

Abstract

Gastrointestinal tumors are the most common tumors, and they are leading cause of cancer deaths worldwide, but their mechanisms are still unclear, which need to be clarified to discover therapeutic targets. p21-activating kinase (PAK), a serine/threonine kinase that is downstream of Rho GTPase, plays an important role in cellular signaling networks. According to the structural characteristics and activation mechanisms of them, PAKs are divided into two groups, both of which are involved in the biological processes that are critical to cells, including proliferation, migration, survival, transformation and metabolism. The biological functions of PAKs depend on a large number of interacting proteins and the signaling pathways they participate in. The role of PAKs in tumors is manifested in their abnormality and the consequential changes in the signaling pathways. Once they are overexpressed or overactivated, PAKs lead to tumorigenesis or a malignant phenotype, especially in tumor invasion and metastasis. Recently, the involvement of PAKs in cellular plasticity, stemness and the tumor microenvironment have attracted attention. Here, we summarize the biological characteristics and key signaling pathways of PAKs, and further analyze their mechanisms in gastrointestinal tumors and others, which will reveal new therapeutic targets and a theoretical basis for the clinical treatment of gastrointestinal cancer.

The significance of PAK4 in signaling and clinicopathology: A review

P21-activated protein kinases (PAKs) are thought to be at the center of tumor signaling pathways. As a representative member of the group II PAK family, P21-activated protein kinase 4 (PAK4) plays an important role in the development of tumors, with several biological functions such as participating in oncogenic transformation, promoting cell division, resisting aging and apoptosis, regulating cytoskeleton and adhesion, as well as suppressing antitumor immune responses. PAK4 is also crucial in biological processes, including the occurrence, proliferation, survival, migration, invasion, drug resistance, and immune escape of tumor cells. It is closely related to poor prognosis and tumor-related pathological indicators, which have significant clinical and pathological significance. Therefore, this article offers a review of the structure, activation, and biological functions of PAK4 and its clinical and pathological importance. This overview should be of assistance for future research on PAK4 and tumors and provide new ideas for tumor treatment and prognostic evaluation of patients.

CORO1C, a novel PAK4 binding protein, recruits phospho-PAK4 at serine 99 to the leading edge and promotes the migration of gastric cancer cells

Gastric cancer is one of the malignant tumors in the world. PAK4 plays an important role in the occurrence and development of gastric cancer, especially in the process of invasion and metastasis. Here we discover that CORO1C, a member of coronin family that regulates microfilament and lamellipodia formation, recruits cytoplasmic PAK4 to the leading edge of gastric cancer cells by C-terminal extension (CE) domain of CORO1C (353-457 aa). The localization of PAK4 on the leading edge of the cell depends on two necessary conditions: the phosphorylation of PAK4 on serine 99 and the binding to the CE domain of CORO1C. Unphosphorylated PAK4 on serine 99 is closely associated with microtubules by PAK4/GEF-H1/Tctex-1 complex. Once phosphorylated, PAK4 is released from microtubule, and then is recruited by CORO1C to the leading edge and regulates the CORO1C/RCC2 (regulator of chromosome condensation 2) complex, leading to the migration of gastric cancer cells. Our results reveal a new mechanism by which PAK4 regulates the migration potential of gastric cancer cells through microtubule-microfilament cross talk.

Interfering with pak4 Protein Expression Affects Osteosarcoma Cell Proliferation and Migration

Purpose

A number of studies have discovered various roles of PAK4 in human tumors, including osteosarcoma. However, the exact role of PAK4 in osteosarcoma and its mechanism have yet to be determined. Therefore, this study focused on interrogating the PAK4 effect on the proliferation and migration ability of osteosarcoma and its underlying mechanisms.

Materials and Methods

Western blot and QRT-PCR were utilized to quantify the PAK4 relative protein and mRNA levels. To measure cellular viability and mobility, the MTT and wound-healing assays were preferred.

Results

With the adenovirus-mediated overexpression of PAK4, the proliferation and migration of U2-OS and MG-63 osteosarcoma cells were stimulated. Furthermore, a liposome-mediated knockout of PAK4 will inhibit osteosarcoma cells from proliferating. In terms of mechanism, we observed the positive correlation of PAK4 expression with expression of P21, CyclinD1, CyclinE1, CDK2, and CDK6, which drives G0/G1 to the G2/M phase transition. PAK4 can also activate Erk expression in OS cells and induce EMT.

Conclusion

Interfering with PAK4 protein expression has been shown to affect osteosarcoma proliferation and migration.

Nuplazid suppresses esophageal squamous cell carcinoma growth in vitro and in vivo by targeting PAK4

Background

Due to the high recurrence and low 5-year survival rates of esophageal squamous cell carcinoma (ESCC) after treatment, the discovery of novel drugs for recurrence chemoprevention is of particular importance.

Methods

We screened the FDA-approved drug library and found that Nuplazid, an atypical antipsychotic that acts as an effective 5-HT 2 A receptor inverse agonist, could potentially exert anticancer effects in vitro and in vivo on ESCC.

Results

Pull-down results indicated that Nuplazid binds with p21-activated kinase 4 (PAK4), and a kinase assay showed that Nuplazid strongly suppressed PAK4 kinase activity. Moreover, Nuplazid exhibited inhibitory effects on ESCC in vivo.

Conclusions

Our findings indicate that Nuplazid can suppress ESCC progression through targeting PAK4.

Gastric Cancer: Identification of microRNAs Inhibiting Druggable Targets and Mediating Efficacy in Preclinical In Vivo Models

In addition to chemotherapy, targeted therapies have been approved for treatment of locally advanced and metastatic gastric cancer. The therapeutic benefit is significant but more durable responses and improvement of survival should be achieved. Therefore, the identification of new targets and new approaches for clinical treatment are of paramount importance. In this review, we searched the literature for down-regulated microRNAs which interfere with druggable targets and exhibit efficacy in preclinical in vivo efficacy models. As druggable targets, we selected transmembrane receptors, secreted factors and enzymes. We identified 38 microRNAs corresponding to the criteria as outlined. A total of 13 miRs target transmembrane receptors, nine inhibit secreted proteins and 16 attenuate enzymes. These microRNAs are targets for reconstitution therapy of gastric cancer. Further target validation experiments are mandatory for all of the identified microRNAs.

PB-10, a thiazolo[4,5-d] pyrimidine derivative, targets p21-activated kinase 4 in human colorectal cancer cells

Targeting p21-activated kinase 4 (PAK4) is a potential therapeutic strategy against human colorectal cancer (CRC). In this study, we synthesized a series of novel thiazolo[4,5-d]pyrimidine derivatives (PB-1-12) and identified PB-10 (PAK4 IC₅₀ = 15.12 μM) as a potential and potent PAK4 inhibitor. Our results showed that PB-10 significantly suppressed the proliferation and colony formation of human CRC cells. PB-10 also arrested HCT-116 CRC cells at sub G0/G1 phase while promoting the expression of proapoptotic proteins. In addition, PB-10 inhibited migration, invasion, and adhesion as well as the PAK4 downstream signaling pathway in HCT-116 cells. Molecular docking analysis showed possible binding modes between PB-10 and PAK4. Our study provides a novel compound that may block the PAK4 signaling in CRC cells.

MicroRNA‑663 inhibits the proliferation and invasion of clear cell renal cell carcinoma cells by directly targeting PAK4

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.

A mandatory role of nuclear PAK4-LIFR axis in breast-to-bone metastasis of ERα-positive breast cancer cells

The mechanism of estrogen receptor alpha (ERα)-positive breast cancer-associated bone metastasis is poorly understood. In this article, we report that nuclear p21-activated kinase 4 (nPAK4) is a novel repressor of ERα-mediated transactivation in a 17β-estradiol (E2)-dependent manner and promotes PAK4–ERα axis-mediated bone metastasis by targeting leukemia inhibitory factor receptor (LIFR) in ERα-positive breast cancer. An evaluation of clinical breast cancer samples revealed that nPAK4 is linked to ERα expression and appears to be associated with a poor prognosis in bone metastatic breast cancer. PAK4 bound and co-translocated with ERα from the cytoplasm to the nucleus upon stimulation with E2. nPAK4 enhanced the invasive potential of ERα-positive breast cancer cells in vitro and promoted breast cancer metastasis in vivo. Mechanistically, nPAK4 promoted the metastasis of ERα-positive breast cancer cells by targeting LIFR, a bone metastasis suppressor. Strikingly, the nuclear accumulation of PAK4 might promote aggressive phenotypes, highlighting nPAK4 as a novel predictive biomarker for ERα-positive breast cancer bone metastasis.

p21-activated kinase 4 as a switch between caspase-8 apoptosis and NF-κB survival signals in response to TNF-α in hepatocarcinoma cells

PAK4 is overexpressed in a variety of human cancers and considered a promising candidate for therapeutic target. However, its functions remain poorly understood, especially in liver carcinogenesis which could be triggered by inflammation. In the present study, endogenous PAK4 was knockdown using siRNA in HepG2 and SK-Hep1 cells. The two cell lines performed reduced cell viability, altered cell cycle composed of decreased S and arrest in G2, and apoptosis. Meanwhile, expression of NF-κB p65 in the nuclei and caspase-8 activity did not show significant differences from control. However, after treating cells with TNF-α, an inflammatory cytokine, we investigated repressed nuclear expression and localization of NF-κB p65, and induced apoptosis with increased caspase-8 activity in PAK4-knockdown cells. The findings revealed that ablation of PAK4 inhibited cell viability via blocking cell cycle and progressing apoptosis. The apoptosis was partially dependent upon caspase-8 concomitant with attenuated NF-κB survival signal due to stimulus of TNF-α. It suggests that PAK4 as target is a switch between caspase-8 apoptosis and NF-κB survival signals induced by TNF-α in hepatocarcinoma cells.

Loss of opioid binding protein/cell adhesion molecule-like gene expression in gastric cancer

Previous studies have reported that the expression of the opioid binding protein/cell adhesion molecule-like (OPCML) gene was frequently downregulated in various of types of cancer. However, little is known regarding the expression of the OPCML gene in gastric cancer. The present study identified that OPCML was downregulated in the gastric cancer SGC7901, KATO III, MKN45, MKN74, SNU1, AGS, N87 and a gastric mucosa cell line GES1, compared with normal gastric tissues by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). To investigate whether the downregulation of OPCML was due to promoter hypermethylation, the methylation of the OPCML promoter was assessed by methylation-specific polymerase chain reaction. Hypermethylation of the OPCML promoter was observed in the gastric cancer MKN45 cell lines, but was not as evident in normal gastric tissue. The methylation inhibitor 5-aza-2'-deoxycytidine was used to remove the methylation of the OPCML gene promoter, following which the expression of OPCML was restored. In addition, the function of the OPCML gene was studied in vitro, and it was found that the restoration expression of OPCML could lead to the suppression of cell growth. In conclusion, the present study has shown that OPCML, which acts as a tumor suppressor, was silenced in gastric cancer cell lines via aberrant hypermethylation of the promoter CpG islands, which may provide a novel molecular approach for the early diagnosis of gastric cancer.

MiR-199a/b-3p inhibits gastric cancer cell proliferation via down-regulating PAK4/MEK/ERK signaling pathway

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.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3949-2) contains supplementary material, which is available to authorized users.

[The expression of moesin, p21-activated kinase 4 (PAK 4), matrix metalloproteinases (MMP 2, MMP 9), and CD34 in the eutopic and ectopic endometrium in adenomyosis]

OBJECTIVE

To investigate the expression of moesin, p21-activated kinase 4 (PAK 4), matrix metalloproteinases (MMP 2, MMP 9), and CD34 in the eutopic and ectopic endometrium in different forms of adenomyosis.

MATERIAL AND METHODS

Fifty uteri removed for diffuse adenomyosis and for adenomyomas were examined in reproductive-aged (n=25) and premenopausal (n=25) women. A comparison group included 20 uteri removed for intramural and subserosal fibroids in reproductive-aged and premenopausal women. The investigators performed histological and immunohistochemical (using antibodies to moesin, PAK 4, MMP 2, MMP 9, and CD34) examinations of the eutopic and ectopic endometrium.

RESULTS

Different forms of adenomyosis were characterized by the irregular border of the endometrium and myometrium due to that there were multiple foci of ingrowth of the basal layer of the endometrium through the terminal plate into the myometrium. In both diffuse adenomyosis and adenomyomas, the basal layer of the eutopic and ectopic endometrium differed many (3-8.5) times, showing the higher expression of the enzymes in the epithelial and stromal cells, which affected their invasive activity (moesin, PAK 4, MMP 2 and MMP 9), and the increased number of CD34 cells in its stroma. At the same time, there were no statistically significant differences in their expression in the basal layer of the eutopic and ectopic endometrium in diffuse adenomyosis and adenomyomas.

CONCLUSION

The findings favor the theory of the pathogenesis of adenomyosis due to the invasion of the eutopic endometrium into the myometrium.

Identification of the PAK4 interactome reveals PAK4 phosphorylation of N-WASP and promotion of Arp2/3-dependent actin polymerization

p21-activated kinase 4 (PAK4) regulates cell proliferation, apoptosis, cell motility and F-actin remodeling, but the PAK4 interactome has not been systematically analyzed. Here, we comprehensively characterized the human PAK4 interactome by iTRAQ quantitative mass spectrometry of PAK4-immunoprecipitations. Consistent with its multiple reported functions, the PAK4 interactome was enriched in diverse protein networks, including the 14-3-3, proteasome, replication fork, CCT and Arp2/3 complexes. Because PAK4 co-immunoprecipitated most subunits of the Arp2/3 complex, we hypothesized that PAK4 may play a role in Arp2/3 dependent actin regulation. Indeed, we found that PAK4 interacts with and phosphorylates the nucleation promoting factor N-WASP at Ser484/Ser485 and promotes Arp2/3-dependent actin polymerization in vitro. Also, PAK4 ablation in vivo reduced N-WASP Ser484/Ser485 phosphorylation and altered the cellular balance between G- and F-actin as well as the actin organization. By presenting the PAK4 interactome, we here provide a powerful resource for further investigations and as proof of principle, we also indicate a novel mechanism by which PAK4 regulates actin cytoskeleton remodeling.

MicroRNA-342 inhibits the progression of glioma by directly targeting PAK4

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.

High expression of P21-activated kinase 5 protein is associated with poor survival in gastric cancer

P21-activated kinase 5 (PAK5), also termed PAK7, is one of the six members of the PAK family of serine/threonine kinases, which are downstream effectors in several cancer signaling pathways. PAK5 promotes neural outgrowth, contributes to microtubule stability and induces resistance to apoptosis. However, the clinical importance of PAK5 in gastric cancer has not been comprehensively investigated. In the present study, PAK5 expression was evaluated in gastric cancer tissue samples. Furthermore, the associations between high expression of PAK5, and clinicopathological features and prognosis were examined. PAK5 expression in primary gastric cancer specimens resected from 279 patients who underwent gastrectomy at the Tokyo Medical and Dental University Hospital was evaluated using immunohistochemistry. Of the 279 patients, 44 (15.8%) exhibited high PAK5 expression, which was significantly associated with the differentiated pathological type (differentiated vs. undifferentiated; P<0.001), depth of tumor invasion (T1 vs. T2-T4; P<0.001), lymph node metastasis (N0 vs. N1-N3; P<0.001), presence of distant metastasis or recurrence (present vs. absent; P=0.038), advanced tumor stage (I vs. II-IV; P=0.001) and worse disease-specific survival (P=0.013). In stage I-III disease, 38/254 (15.0%) patients exhibited high PAK5 expression, and high expression of PAK5 was significantly associated with relapse-free interval (P=0.044). PAK5 may serve an important role in tumor progression and influence the outcome of patients with gastric cancer.

P21 activated kinase 4 binds translation elongation factor eEF1A1 to promote gastric cancer cell migration and invasion

P21 activated kinase 4 (PAK4), as an effector of Cdc42, playing important roles in regulating the processes of cytoskeleton organization. PAK4 has been considered to be an oncogenic protein, which has strong relationship with gastric cancer metastasis. However, the mechanism of PAK4 in regulating gastric cancer metastasis is still not fully understood. In this study, using yeast two-hybrid system, we identified that the eukaryotic elongation factor 1 α1 (eEF1A1) is a new binding partner of PAK4. The interaction between PAK4 and eEF1A1 was confirmed by GST pull-down and co-immunoprecipitation. PAK4 co-localized with eEF1A1 in the cytoplasm of gastric cancer cells. Overexpression of PAK4 enhanced the expression level of eEF1A1 and vice versa. PAK4 and eEF1A1 could cooperate to promote gastric cancer cell migration and invasion. Furthermore, the expression of PAK4 and eEF1A1 in clinical gastric cancer samples were examined by western blotting and immunohistochemistry. Statistical analysis indicated that there was positive correlation between the expression of PAK4 and eEF1A1. This study demonstrated for the first time that PAK4 interacted with eEF1A1 to promote migration and invasion of gastric cancer cells, thereby providing new insights into the function of PAK4 and eEF1A1 in the progression of gastric cancer.

GL-1196 Suppresses the Proliferation and Invasion of Gastric Cancer Cells via Targeting PAK4 and Inhibiting PAK4-Mediated Signaling Pathways

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.