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Abstract Background Ovarian cancer is the most common cause of gynecological cancer death. Pak4 has been proved to be tumorigenic in many types of cancers, but its role in ovarian cancer is still not clarified. Methods In this study, we used immunohistochemistry to investigate into Pak4 expression in different histological types of ovarian cancer. TIMER, TISCH2, GEPIA, ualcan, KM plotter, GSCA and GeneMANIA were used to identify the prognostic roles and gene regulation networks of Pak4 in ovarian cancer. Immune infiltration levels were investigated using TIMER database. Results Pak4 was highly expressed in ovarian cancers, regardless of different FIGO stages and histological grades. Single cell sequencing database proved that Pak4 was highly expressed in malignant ovarian cancer cells. Pak4 level was significantly correlated with different histological types of ovarian cancer. Pak4 expression was negatively connected with OS and PFS of ovarian cancer patients. Functions of Pak4 and its interacted genes were mainly involved in protein serine/threonine kinase activity, regulation of actin filament-based process and regulation of cytoskeleton organization. Pak4 level was negatively correlated with immune biomarkers of B cell infiltration (p = 2.39e-05), CD8 + T cell infiltration (p = 1.51e-04), neutrophil (p = 1.74e-06) and dendritic cell (p = 4.41e-08). Close correlation was found between Pak4 expression and T cell exhaustion (p

Background: Ovarian cancer is the most common cause of gynecological cancer death. Pak4 has been proved to be tumorigenic in many types of cancers, but its role in ovarian cancer is still not clarified. Methods: In this study, we used immunohistochemistry to investigate into Pak4 expression in different histological types of ovarian cancer. TIMER, TISCH2, GEPIA, ualcan, KM plotter, GSCA and GeneMANIA were used to identify the prognostic roles and gene regulation networks of Pak4 in ovarian cancer. Immune infiltration levels were investigated using TIMER database. Results: Pak4 was highly expressed in ovarian cancers, regardless of different FIGO stages and histological grades. Single cell sequencing database proved that Pak4 was highly expressed in malignant ovarian cancer cells. Pak4 level was significantly correlated with different histological types of ovarian cancer. Pak4 expression was negatively connected with OS and PFS of ovarian cancer patients. Functions of Pak4 and its interacted genes were mainly involved in protein serine/threonine kinase activity, regulation of actin filament-based process and regulation of cytoskeleton organization. Pak4 level was negatively correlated with immune biomarkers of B cell infiltration (p = 2.39e-05), CD8 + T cell infiltration (p = 1.51e-04), neutrophil (p = 1.74e-06) and dendritic cell (p = 4.41e-08). Close correlation was found between Pak4 expression and T cell exhaustion (p < 0.05). Conclusions: Our results demonstrated the expression level, gene interaction networks and immune infiltration levels of Pak4 in ovarian cancer. And the results revealed role of Pak4 in tumorigenesis and the possibility to be a potential immunotherapeutic target. [ABSTRACT FROM AUTHOR]

Background: Familial non-medullary thyroid carcinoma (FNMTC) is a genetically predisposed disease with unclear genetic mechanisms. This makes research on susceptibility genes important for the diagnosis and treatment options. Methods: This study included a five-member family affected by papillary thyroid carcinoma. The candidate genes were identified through whole-exome sequencing and Sanger sequencing in family members, other FNMTC patients, and sporadic non-medullary thyroid carcinoma patients. The pathogenicity of the mutation was predicted using in silico tools. Cell phenotype experiments in vitro and models of lung distant metastasis in vivo were conducted to confirm the characteristics of the mutation. Transcriptome sequencing and mechanistic validation were employed to compare the disparities between PAK4 wild-type (WT) and PAK4 mutant (MUT) cell lines. Results: This mutation alters the protein structure, potentially increasing instability by affecting hydrophobicity, intra-molecular hydrogen bonding, and phosphorylation sites. It specifically promotes phosphorylated PAK4 nuclear translocation and expression in thyroid tissue and cell lines. Compared with the WT cells line, PAK4 I417T demonstrates enhanced proliferation, invasiveness, accelerated cell division, and inhibition of cell apoptosis in vitro. In addition, it exhibits a significant propensity for metastasis in vivo. It activates tumor necrosis factor signaling through increased phosphorylation of PAK4, JNK, NFκB, and c-Jun, unlike the WT that activates it via the PAK4-NFκ-MMP9 axis. In addition, PAK4 MUT protein interacts with matrix metalloproteinase (MMP)3 and regulates MMP3 promoter activity, which is not observed in the WT. Conclusions: Our study identified PAK4: c.T1250C: p.I417T as a potential susceptibility gene for FNMTC. The study concludes that the mutant form of PAK4 exhibits oncogenic function, suggesting its potential as a novel diagnostic molecular marker for FNMTC. [ABSTRACT FROM AUTHOR]

Objective: To investigate the relationship between p21-activated kinase (PAK) 4, PAK5 protein expression and epithelial-mesenchymal transition (EMT), clinicopathological features and prognosis in non-small cell lung cancer (NSCLC). Methods: 100 NSCLC patients who were admitted to our hospital from January 2018 to December 2019 were selected, collect surgically excised cancer tissue and adjacent tissue samples, the expressions of PAK4, PAK5 and EMT-related proteins [E-cadherin (E-Cad), N-cadherin (N-Cad) and vimentin (VIM)] in NSCLC tissues and tissues adjacent to cancer were detected by immunohistochemistry. The relationship between the expression of PAK4 and PAK5 proteins and the pathological features of NSCLC patients and the correlation with EMT-related proteins were analyzed. Patients were divided into positive/negative expression group according to the expression of PAK4and PAK5 in NSCLC tissues. Survival curves of NSCLC patients with positive/negative expression of PAK4 and PAK5 were drawn by K-M method, and the influencing factors of death in NSCLC patients were analyzed by multivariate Cox regression analysis. Results: Compared with tissues adjacent to cancer, positive expression rates of PAK4, PAK5, N-Cad and VIM proteins in NSCLC tissues were increased, positive expression rate of E-Cad protein was decreased (P＜0.05). Two column correlation analysis showed that, PAK4 and PAK5 were negatively correlated with the positive expression rate of E-Cad protein in NSCLC tissues, there was a positive correlation between the positive expression rate of N-Cad and VIM protein (all P＜0.001). The positive expression rates of PAK4 and PAK5 protein in NSCLC patients with different differentiation degree, TNM stage and lymph node metastasis were compared, the difference was statistically significant (P＜0.05). The 3-year overall survival rate of 100 NSCLC patients was 56.00 % (56/100). K-M survival curve analysis showed that, overall survival rate of PAK4 and PAK5 positive expression group was lower than that of negative expression group (P＜0.05). Multivariate Cox regression analysis showed that, poor differentiation, TNM stage IIIA, lymph node metastasis and positive expression of PAK4 and PAK5 proteins were independent risk factors for death in NSCLC patients (P＜0.05). Conclusion: The expression of PAK4 and PAK5 proteins in NSCLC tissue increases, which is relate to EMT, differentiation, TNM stage, lymph node metastasis and prognosis, may become a new target for the diagnosis and treatment of NSCLC. [ABSTRACT FROM AUTHOR]

Summary: Background: Finding the oncogene, which was able to inhibit tumor cells intrinsically and improve the immune answers, will be the future direction for renal cancer combined treatment. Following patient sample analysis and signaling pathway examination, we propose p21-activated kinase 4 (PAK4) as a potential target drug for kidney cancer. PAK4 exhibits high expression levels in patient samples and plays a regulatory role in the immune microenvironment. Methods: Utilizing AI software for peptide drug design, we have engineered a specialized peptide proteolysis targeting chimera (PROTAC) drug with selectivity for PAK4. To address challenges related to drug delivery, we developed a nano-selenium delivery system for efficient transport of the peptide PROTAC drug, termed PpD (PAK4 peptide degrader). Findings: We successfully designed a peptide PROTAC drug targeting PAK4. PpD effectively degraded PAK4 with high selectivity, avoiding interference with other homologous proteins. PpD significantly attenuated renal carcinoma proliferation in vitro and in vivo. Notably, PpD demonstrated a significant inhibitory effect on tumor proliferation in a fully immunocompetent mouse model, concomitantly enhancing the immune cell response. Moreover, PpD demonstrated promising tumor growth inhibitory effects in mini-PDX and PDO models, further underscoring its potential for clinical application. Interpretation: This PAK4-targeting peptide PROTAC drug not only curtails renal cancer cell proliferation but also improves the immune microenvironment and enhances immune response. Our study paves the way for innovative targeted therapies in the management of renal cancer. Funding: This work is supported by Research grants from non-profit organizations, as stated in the Acknowledgments.

Pancreatic Ductal Adenocarcinoma (PDAC) remains one of the most difficult to treat cancers. Gemcitabine is still the standard of care treatment for PDAC but with modest survival benefit and well reported resistance. Here we explored potential of inhibiting p21 activated kinase 4 (PAK4), a downstream protein of KRAS oncogenic pathway, in combination with Gemcitabine in PDAC cells. PAK4 inhibition by KPT-9274 led to significant potentiation of Gemcitabine activity in PDAC cells, with an increase in apoptosis, DNA damage and cell cycle arrest. At molecular level, PAK4 inhibition dose dependently inhibited Gemcitabine-induced β-catenin, c-JUN and Ribonucleotide Reductase subunit 2 (RRM2) levels. PAK4 inhibition further inhibited levels of phosphorylated ERK (p-ERK); Gemcitabine-induced phosphorylated AKT (p-AKT), phosphorylated and total c-Myc. These results suggest possible role of β-catenin, p-ERK and p-AKT, key effector proteins of Wnt/β-catenin, MAPK and PI3K pathways respectively, in sensitisation of Gemcitabine activity with PAK4 inhibition. Our data unravel probable molecular mechanisms behind combination of PAK4 inhibition with Gemcitabine to counter PDAC, which may be unequivocally proved further with knock down of PAK4. Our findings provide a strong rationale to exploit the combination therapy of Gemcitabine and PAK4 inhibitor for PDAC at pre-clinical and clinical levels.

Introduction: The actin regulatory protein, cofilin plays a key signaling role in many cells for numerous cellular responses including in proliferation, development, motility, migration, secretion and growth. In the pancreas it is important in islet insulin secretion, growth of pancreatic cancer cells and in pancreatitis. However, there are no studies on its role or activation in pancreatic acinar cells. Methods: To address this question, we studied the ability of CCK to activate cofilin in pancreatic acinar cells, AR42J cells and CCK1-R transfected Panc-1 cells, the signaling cascades involved and its effect on enzyme secretion and MAPK activation, a key mediator of pancreatic growth. Results: CCK (0.3 and 100 nM), TPA, carbachol, Bombesin, secretin and VIP decreased phospho-cofilin (i.e., activate cofilin) and both phospho-kinetic and inhibitor studies of cofilin, LIM kinase (LIMK) and Slingshot Protein Phosphatase (SSH1) demonstrated these conventional activators of cofilin were not involved. Serine phosphatases inhibitors (calyculin A and okadaic acid), however inhibited CCK/TPA-cofilin activation. Studies of various CCK-activated signaling cascades showed activation of PKC/PKD, Src, PAK4, JNK, ROCK mediated cofilin activation, but not PI3K, p38, or MEK. Furthermore, using both siRNA and cofilin inhibitors, cofilin activation was shown to be essential for CCK-mediated enzyme secretion and MAPK activation. Conclusion: These results support the conclusion that cofilin activation plays a pivotal convergent role for various cell signaling cascades in CCK mediated growth/enzyme secretion in pancreatic acini. [ABSTRACT FROM AUTHOR]

p21-Activated kinase 4 (PAK4), one of the serine/threonine kinases activated by Rho-family GTPases, has been widely studied as an oncogenic protein that is overexpressed in many types of cancers. In our recent study, PAK4 upregulation was observed in mice exhibiting hepatic ischaemia-reperfusion (I/R) and in liver transplantation patients. Liver I/R injury was also attenuated in Pak4 KO mice. Herein, we report a novel series of pyrazolo[3,4-d]pyrimidine derivatives of type I ½ PAK4 inhibitors. The most potent compound SPA7012 was evaluated to determine the pharmacological potential of PAK4 inhibitor in I/R injury in mice. Mice with I/R injury showed typical patterns of liver damage, as demonstrated by increases in serum levels of aminotransferases and proinflammatory cytokines, hepatocellular necrosis and apoptosis, and inflammatory cell infiltration, relative to sham mice. Conversely, intraperitoneal administration of SPA7012 dramatically attenuated biochemical and histopathologic changes. Mechanistically, stabilisation of nuclear factor-erythroid 2-related factor 2 (Nrf2), a master regulator of anti-oxidative response, was observed following SPA7012 treatment. SPA7012 treatment in primary hepatocytes also attenuated hypoxia-reoxygenation-induced apoptotic cell death and inflammation. Together, these results provide experimental evidence supporting the use of PAK4 inhibitors for alleviation of I/R-induced liver damage.

Abstract Background Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. P21 activated kinase 4 (PAK4) and Breast cancer anti-estrogen resistance 3 (BCAR3) have been reported to be involved in numerous aspects in tumorous progression. In this study, we propose to screen multi-targeted microRNAs. (miRNAs), which simultaneously inhibit neoplastic evolution through suppressing the transcription of target genes. Methods MTT and Colony formation assays measured cell’s viability and proliferation. Scratch wound and Transwell assays detected the ability in migration and invasion for SW116 cells. The multi-targeted microRNAs of PAK4 and BCAR3 were predicted using bioinformatics analysis and verified by conducting dual luciferase reporter assay, western blot and qRT-PCR that could detect the expression levels of miR-199a/b-3p. Results The knockdown of PAK4 significantly impeded proliferation and colony formation of SW1116 cells when the knockdown of BCAR3 hindered migration and invasion of SW1116 cells. MiR-199a/b-3p directly targeted the 3'-UTR of PAK4 and BCAR3, further effected proliferation, colony formation, migration, and invasion of SW1116 cells. PAK4 or BCAR3 overexpression could partially reversed inhibitory effects of miR-199a/b-3p. Conclusions These results provided a new multi-targeted cite for cancerous suppressant to improve the prognosis of CRC inpatients.

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. [ABSTRACT FROM AUTHOR]

Background: Oral squamous carcinoma (OSCC), the most common head and neck malignancy, has a strong propensity for malignant proliferation and metastasis, which will decrease the survival of patients. P21-activated kinase 4 (PAK4), a classical serine/threonine protein kinase with multiple cellular functions, has an essential role in cancer cell migration and invasion. Here, we elucidated the function and possible molecular mechanisms of the effect of PAK4 on the biological behaviors of OSCC. Methods: The expression of genes and protein was detected by real-time PCR and western blotting. We used oral squamous carcinoma cell lines, Tca8117, Cal 27, SCC 4, and SCC 9 for validation of our cell function data. Flow cytometry, 3D cultures, and clone formation assay were used to detect proliferation of cells. RNA sequencing and bioinformatic analysis was performed to determine the potential function of PAK4. Results: Immunohistochemistry, western blotting and real-time PCR demonstrated that PAK4 expression was up-regulated in OSCC tissues. Overexpression of PAK4 promoted the proliferation, migration and invasion of OSCC cell lines. RNA sequencing (RNA-seq) for the transcriptome-wide analysis of differential gene expression followed by bioinformatic analysis was performed to determine the potential function of PAK4. Based on the KEGG enrichment analysis and GO analysis of differential expression genes (DEGs) we found that PAK4 promotes the cell-cycle machinery, which associated with 44 regulated genes, thereby promoting cancer cell differentiation. Conclusions: This study demonstrates that the PAK4 regulates the biological behaviors of OSCC by PI3K–AKT signaling pathway, and these findings might provide a novel strategy for OSCC treatment. [ABSTRACT FROM AUTHOR]

The cell motility of smooth muscle cells (SMCs) is essential for vascular and internal organ development and tissue regeneration in response to damage. Cell migration requires dynamic changes in the actin-cytoskeleton via the p-21 activated kinase (Pak)-Cofilin signaling cascade, which is the central axis of the actin filaments. We previously identified that the Inka2 gene was preferentially expressed in the central nervous system (CNS) and revealed that Inka2 directly binds Pak4 to suppress its kinase activity, thereby regulating actin de-polymerization in dendritic spine formation of the forebrain neurons. However, its physiological significance outside the CNS remains unclear. Here we determined the Inka2 expression profile in various organs using in situ hybridization analysis and lacZ staining on Inka2 flox/+ mice. Robust Inka2 expression was consistently detected in the SMCs of many peripheral organs, including the arteries, esophagus, stomach, intestine, and bladder. The scratch assay was used on primary cultured SMCs and revealed that Inka2 −/− SMC exhibits accelerated cell migration ability without a change in the cell proliferation rate. Inka2 −/− SMCs displayed Cofilin activation/phosphorylation, a downstream molecule of Pak4 signal cascade. These results suggest that Inka2 regulates SMC motility through modulating actin reorganization as the endogenous inhibitor of Pak4. • Smooth muscle tissue strongly expresses the Inka2 gene. • Inka2 −/− smooth muscle cells exhibit accelerated cell migration ability. • Pak-Cofilin signaling cascade is elevated in Inka2 −/− smooth muscle cells. [ABSTRACT FROM AUTHOR]

We studied the mechanism underlying the effect of baicalein on the growth of transplanted esophageal cancer in NOG mice and its effect on the expression of PAK4. For that purpose, we developed a new model of transplanted esophageal cancer (human esophageal cancer OE19 cells (107 cells/ml) were inoculated to NOG mice). Three experimental groups with transplanted esophageal cancer cells received baicalein in different doses (1, 1.5, and 2 mg/kg). In 32 days, the tumors were resected, and the expression of PAK4 and the level of activated PAK4 were assayed by reverse transcription PCR and Western blotting, respectively. The results showed a dose-depending anti-tumor effect of baicalein on the transplanted esophageal cancer in NOG mice: this effect of baicalein (determined by the size and weight of the tumor) increased with increasing the dose of the substance. Furthermore, the anti-tumor effect of baicalein was also confirmed by reduction of PAK4 expression. Thus, baicalein can inhibit tumor growth by inhibiting activation of PAK4. Therefore, our results showed that baicalein could inhibit the growth of esophageal cancer cells by inhibiting the activity of PAK4, which can be an important mechanism of its antitumor effect. [ABSTRACT FROM AUTHOR]

The overexpression of p21-activated kinase 4 (PAK4) is associated with a variety of cancers. In this paper, the binding modes and inhibitory mechanisms of four 7H-pyrrolo[2,3-d]pyrimidine competitive inhibitors of PAK4 were investigated at the molecular level, mainly using molecular dynamics simulations and binding free energy calculations. The results show that the inhibitors had strong interactions with the hinge region, the β-sheets, and the residues with charged side chains around the 4-substituent. The terminal amino group of the inhibitor 5n was different from the other three, which could cause the enhancement of hydrogen bonds or electrostatic interactions formed with the surrounding residues. Thus, inhibitor 5n had the strongest inhibition capacity. The different halogen atoms on the 2-substituents of the inhibitors 5h, 5g, and 5e caused differences in the positions of the 2-benzene rings and affected the interactions of the hinge region. It also affected to some extent the orientations of the 4-imino groups and consequently their affinities for the surrounding charged residues. The combined results lead to the weakest inhibitory capacity of inhibitor 5e. [ABSTRACT FROM AUTHOR]

Introduction: The actin regulatory protein, cofilin plays a key signaling role in many cells for numerous cellular responses including in proliferation, development, motility, migration, secretion and growth. In the pancreas it is important in islet insulin secretion, growth of pancreatic cancer cells and in pancreatitis. However, there are no studies on its role or activation in pancreatic acinar cells.Methods: To address this question, we studied the ability of CCK to activate cofilin in pancreatic acinar cells, AR42J cells and CCK1-R transfected Panc-1 cells, the signaling cascades involved and its effect on enzyme secretion and MAPK activation, a key mediator of pancreatic growth.Results: CCK (0.3 and 100 nM), TPA, carbachol, Bombesin, secretin and VIP decreased phospho-cofilin (i.e., activate cofilin) and both phospho‐kinetic and inhibitor studies of cofilin, LIM kinase (LIMK) and Slingshot Protein Phosphatase (SSH1) demonstrated these conventional activators of cofilin were not involved. Serine phosphatases inhibitors (calyculin A and okadaic acid), however inhibited CCK/TPA-cofilin activation. Studies of various CCK‐activated signaling cascades showed activation of PKC/PKD, Src, PAK4, JNK, ROCK mediated cofilin activation, but not PI3K, p38, or MEK. Furthermore, using both siRNA and cofilin inhibitors, cofilin activation was shown to be essential for CCK-mediated enzyme secretion and MAPK activation.Conclusion: These results support the conclusion that cofilin activation plays a pivotal convergent role for various cell signaling cascades in CCK mediated growth/enzyme secretion in pancreatic acini.

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.

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.

p21 activated kinase 4 (PAK4) along with PAK5 and PAK6 are members of the type II family of PAKs. From the type II family, PAK4 is being assessed as an expansively investigated area. PAK4 acts as a serine/threonine kinase in response to Rho GTPases, while interaction partners and substrates are rapidly extended, implying a diverse range of cellular functions regulated by PAK4, including cell cycle progression, proliferation, survival, cell adhesion, motility, neuronal development, and immune defense. Thus, altered expression and function of PAK4 imparts numerous pathological conditions. The overexpressed and, in some cases, amplified PAK4 gene is revealed to be associated with a diverse range of cancers. Ongoing findings explain how PAK4 is involved in cancer progression, promoting cancer cell growth, survival, and metastasis with the corresponding activation and signaling schemes. Meanwhile, upstream activating and downstream effector molecules are increasingly identified to elucidate the exact mode of action on the cancer progression role of PAK4. A plethora of approaches targeting PAK4 is continuing to assess the potentiality of inhibitors to eradicate the growth and metastasis of cancers overexpressing PAK4. Here, we summarize the findings on the role of PAK4 and its signaling pathways promoting cancers and examine PAK4 as a promising target for multitype cancers.

Purpose: Acute respiratory distress syndrome (ARDS) is a prevalent illness in intensive care units. Extracellular vesicles and particles released from activated alveolar macrophages (AMs) assist in ARDS lung injury and the inflammatory process through mechanisms that are unclear. This study investigated the role of AM-derived secretory autophagosomes (SAPs) in lung injury and microRNA (MiR)-199a-3p-regulated inflammation associated with ARDS in vitro and in a murine model. Methods: The ARDS model in mouse was established by intratracheal LPS lipopolysaccharide (LPS) injection. The agomirs or antagomirs of MiR-199a-3p were injected into the caudal vein to figure out whether MiR-199a-3p could influence ARDS inflammation and lung injury, whereas the mimics or inhibitors of MiR-199a-3p, siRNA of Rab8a, or PAK4 inhibitor were transfected or applied to RAW264.7 cells to evaluate the mechanism of SAP release. Culture supernatants of RAW264.7 cells treated with LPS or bronchoalveolar lavage fluid from mice were collected for the isolation of SAPs. Results: We found that MiR-199a-3p was over-expressed in the lungs of ARDS mice. The MiR-199a-3p antagomir alleviated, whereas the MiR-199a-3p agomir exacerbated LPS-induced inflammation in mice by promoting AM-derived SAP secretion. In addition, MiR-199a-3p over-expression exacerbated LPS-induced ARDS via activating Rab8a, and Rab8a silencing significantly suppressed the promoting influence of the MiR-199a-3p mimic on SAP secretion. Furthermore, MiR-199a-3p mimic activated Rab8a by directly inhibiting PAK4 expression. Conclusion: The novel finding of this study is that MiR-199a-3p participated in the regulation of SAP secretion and the inflammatory process via targeting of PAK4/Rab8a, and is a potential therapeutic candidate for ARDS treatment. [ABSTRACT FROM AUTHOR]

Exploiting the pluripotent properties of embryonic stem cells (ESCs) holds great promise for regenerative medicine. Nevertheless, directing ESC differentiation into specialized cell lineages requires intricate control governed by both intrinsic and extrinsic factors along with the actions of specific signaling networks. Here, we reveal the involvement of the p21-activated kinase 4 (Pak4), a serine/threonine kinase, in sustaining murine ESC (mESC) pluripotency. Pak4 is highly expressed in R1 ESC cells compared with embryonic fibroblast cells and its expression is progressively decreased during differentiation. Manipulations using knockdown and overexpression demonstrated a positive relationship between Pak4 expression and the clonogenic potential of mESCs. Moreover, ectopic Pak4 expression increases reprogramming efficiency of Oct4-Klf4-Sox2-Myc-induced pluripotent stem cells (iPSCs) whereas Pak4-knockdown iPSCs were largely incapable of generating teratomas containing mesodermal, ectodermal and endodermal tissues, indicative of a failure in differentiation. We further establish that Pak4 expression in mESCs is transcriptionally driven by the core pluripotency factor Nanog which recognizes specific binding motifs in the Pak4 proximal promoter region. In turn, the increased levels of Pak4 in mESCs fundamentally act as an upstream activator of the Akt pathway. Pak4 directly binds to and phosphorylates Akt at Ser473 with the resulting Akt activation shown to attenuate downstream GSK3β signaling. Thus, our findings indicate that the Nanog-Pak4-Akt signaling axis is essential for maintaining mESC self-renewal potential with further importance shown during somatic cell reprogramming where Pak4 appears indispensable for multi-lineage specification. Graphical Abstract [ABSTRACT FROM AUTHOR]

INTRODUCTION:Sustained proliferative signaling and de-regulated cellular bioenergetics are two of the chief hallmarks of cancer. Alterations in the Ras pathway and its downstream effectors are among the major drivers for uncontrolled cell growth in many cancers. The GTPases are one of the signaling molecules that activate crucial signal transducing pathways downstream of Ras through several effector proteins. The GTPases (GTP bound) interact with several effectors and modulate a number of different biological pathways including those that regulate cytoskeleton, cellular motility, cytokinesis, proliferation, apoptosis, transcription and nuclear signaling. Similarly, the altered glycolytic pathway, the so-called 'Warburg effect', rewires tumor cell metabolism to support the biosynthetic requirements of uncontrolled proliferation. There exists strong evidence for the critical role of the glycolytic pathway's rate limiting enzymes in promoting immunosuppression. Areas covered: We review the emerging roles of GTPase effector proteins particularly the p21 activated kinase 4 (PAK4) and nicotinamide biosynthetic pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT) as signaling molecules in immune surveillance and the immune response. Expert opinion: In this expert opinion article we highlight the recent information on the role of GTPases and the metabolic enzymes on the immune microenvironment and propose some unique immune therapeutic opportunities.

Abstract Background Skeletal muscle regeneration is an adaptive response to injury that is crucial to the maintenance of muscle mass and function. A p21‐activated kinase 4 (PAK4) serine/threonine kinase is critical to the regulation of cytoskeletal changes, cell proliferation, and growth. However, PAK4's role in myoblast differentiation and regenerative myogenesis remains to be determined. Methods We used a mouse model of myotoxin (notexin)‐induced muscle regeneration. In vitro myogenesis was performed in the C2C12 myoblast cell line, primary myoblasts, and primary satellite cells. In vivo overexpression of PAK4 or kinase‐inactive mutant PAK4S474A was conducted in skeletal muscle to examine PAK4's kinase‐dependent effect on muscle regeneration. The regeneration process was evaluated by determining the number and size of multinucleated myofibres and expression patterns of myogenin and eMyHC. To explore whether PAK4 inhibition improves muscle regeneration, mice were injected intramuscularly with siRNA that targeted PAK4 or orally administered with a chemical inhibitor of PAK4. Results p21‐activated kinase 4 was highly expressed during the myoblast stage, but expression gradually and substantially decreased as myoblasts differentiated into myotubes. PAK4 overexpression, but not kinase‐inactive mutant PAK4S474A overexpression, significantly impeded myoblast fusion and MyHC‐positive myotube formation in C2C12 cells, primary myoblasts, and satellite cells (P

PurposeAcute respiratory distress syndrome (ARDS) is a prevalent illness in intensive care units. Extracellular vesicles and particles released from activated alveolar macrophages (AMs) assist in ARDS lung injury and the inflammatory process through mechanisms that are unclear. This study investigated the role of AM-derived secretory autophagosomes (SAPs) in lung injury and microRNA (MiR)-199a-3p-regulated inflammation associated with ARDS in vitro and in a murine model.MethodsThe ARDS model in mouse was established by intratracheal LPS lipopolysaccharide (LPS) injection. The agomirs or antagomirs of MiR-199a-3p were injected into the caudal vein to figure out whether MiR-199a-3p could influence ARDS inflammation and lung injury, whereas the mimics or inhibitors of MiR-199a-3p, siRNA of Rab8a, or PAK4 inhibitor were transfected or applied to RAW264.7 cells to evaluate the mechanism of SAP release. Culture supernatants of RAW264.7 cells treated with LPS or bronchoalveolar lavage fluid from mice were collected for the isolation of SAPs.ResultsWe found that MiR-199a-3p was over-expressed in the lungs of ARDS mice. The MiR-199a-3p antagomir alleviated, whereas the MiR-199a-3p agomir exacerbated LPS-induced inflammation in mice by promoting AM-derived SAP secretion. In addition, MiR-199a-3p over-expression exacerbated LPS-induced ARDS via activating Rab8a, and Rab8a silencing significantly suppressed the promoting influence of the MiR-199a-3p mimic on SAP secretion. Furthermore, MiR-199a-3p mimic activated Rab8a by directly inhibiting PAK4 expression.ConclusionThe novel finding of this study is that MiR-199a-3p participated in the regulation of SAP secretion and the inflammatory process via targeting of PAK4/Rab8a, and is a potential therapeutic candidate for ARDS treatment.

Background: Colorectal cancer (CRC) is one of the leading causes of cancer-related death worldwide. P21 activated kinase 4 (PAK4) and Breast cancer anti-estrogen resistance 3 (BCAR3) have been reported to be involved in numerous aspects in tumorous progression. In this study, we propose to screen multi-targeted microRNAs. (miRNAs), which simultaneously inhibit neoplastic evolution through suppressing the transcription of target genes. Methods: MTT and Colony formation assays measured cell's viability and proliferation. Scratch wound and Transwell assays detected the ability in migration and invasion for SW116 cells. The multi-targeted microRNAs of PAK4 and BCAR3 were predicted using bioinformatics analysis and verified by conducting dual luciferase reporter assay, western blot and qRT-PCR that could detect the expression levels of miR-199a/b-3p. Results: The knockdown of PAK4 significantly impeded proliferation and colony formation of SW1116 cells when the knockdown of BCAR3 hindered migration and invasion of SW1116 cells. MiR-199a/b-3p directly targeted the 3'-UTR of PAK4 and BCAR3, further effected proliferation, colony formation, migration, and invasion of SW1116 cells. PAK4 or BCAR3 overexpression could partially reversed inhibitory effects of miR-199a/b-3p. Conclusions: These results provided a new multi-targeted cite for cancerous suppressant to improve the prognosis of CRC inpatients. [ABSTRACT FROM AUTHOR]

Introduction: Long intergenic non-protein-coding RNA 1296 (LINC01296), a newly identified lncRNA, can function as an oncogenic driver to promote the development of multiple carcinomas. However, the effect of LINC01296 on oral squamous cell carcinoma (OSCC) is still unclear.Material and methods: We determined the expression and role of LINC01296 in OSCC tissues and cell lines. The cell viability, migration and invasion were determined by MTT, wound healing assay and transwell assay, respectively. Flow cytometry was used for detecting cell cycle and apoptosis. The interaction and association between LINC01296, microRNA-485-5p (miR-485-5p) and p21 (RAC1) activated kinase 4 (PAK4) were analyzed by RNA immunoprecipitation (RIP) and luciferase reporter assays. The xenograft mouse model was established to detect the effect of LINC01296 on OSCC tumor growth.Results: Our study showed that LINC01296 was over-expressed in OSCC tissues and cell lines. The level of LINC01296 was positively correlated with the patient's tumor node metastasis (TNM) stage and nodal invasion. Knockdown of LINC01296 effectively inhibits cell viability, migration and invasion but promotes cell apoptosis in vitro. The in vivo experiment showed that LINC01296 knockdown inhibited OSCC tumor growth. The following analysis indicated that LINC01296 acted as a ceRNA for miR-485-5p, and PAK4 was identified as a direct target of miR-485-5p. Furthermore, we found that the effects of LINC01296 on OSCC progression were through regulating the expression of PAK4/p-MEK/p-ERK via sponging miR-485-5p.Conclusions: LINC01296 promote the cell cycle, proliferation, migration and invasion, and inhibit apoptosis of OSCC cells through activating the MAPK/ERK signaling pathway via sponging miR-485-5p to regulate PAK4 expression. These results suggested that the LINC01296/miR-485-5p/PAK4 axis was closely associated with OSCC progression. Our study provides a new insight into the molecular pathogenesis of OSCC, and may supply novel biomarkers for diagnosis and therapy of OSCC. [ABSTRACT FROM AUTHOR]

Purpose: Knowledge on the potential association between differential gene expression and risk of gastrointestinal stromal tumors (GISTs) is currently limited. We used bioinformatics tools to identify differentially expressed genes in GIST samples and the related signaling pathways of these genes. Patients and Methods: The GSE136755 dataset was obtained from the GEO database and differentially expressed genes (CENPA, CDK1, TPX2, CCNB1, CCNA2, BUB1, AURKA, KIF11, NDC80) were screened using String and Cytoscape bioinformatics tools. Then, three groups of eight patients at high, intermediate and low risk of GIST were selected from patients diagnosed with GIST by immunohistochemistry in our hospital from October 2020 to March 2021. Differential expression of CDK1 and BUB1 was verified by comparing the amount of expressed p21-Activated kinase 4 (PAK4) protein in pathological sections. Results: SPSS26.0 analysis showed that the expression level of PAK4 in GISTs was significantly higher than in normal tissues and paratumoral tissues and there was significant difference among the three groups of patients (P < 0.01). PAK4 levels in paratumoral and normal tissues were negligible with no significant difference between the tissues. Conclusion: CENPA, CDK1, TPX2, CCNB1, CCNA2, BUB1, AURKA, KIF11 and NDC80 gene expression can be used as biomarkers to assess the risk of gastrointestinal stromal tumors whereby expression increases gradually with the increased risk of GIST formation. The genes encode proteins that regulate the division, proliferation and apoptosis of gastrointestinal stromal tumors mainly through PI3K/AKT, MARK, P53, WNT and other signaling pathways. [ABSTRACT FROM AUTHOR]

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.

The overexpression of p21-activated kinase 4 (PAK4) is associated with a variety of cancers. In this paper, the binding modes and inhibitory mechanisms of four 7H-pyrrolo[2,3-d]pyrimidine competitive inhibitors of PAK4 were investigated at the molecular level, mainly using molecular dynamics simulations and binding free energy calculations. The results show that the inhibitors had strong interactions with the hinge region, the β-sheets, and the residues with charged side chains around the 4-substituent. The terminal amino group of the inhibitor 5n was different from the other three, which could cause the enhancement of hydrogen bonds or electrostatic interactions formed with the surrounding residues. Thus, inhibitor 5n had the strongest inhibition capacity. The different halogen atoms on the 2-substituents of the inhibitors 5h, 5g, and 5e caused differences in the positions of the 2-benzene rings and affected the interactions of the hinge region. It also affected to some extent the orientations of the 4-imino groups and consequently their affinities for the surrounding charged residues. The combined results lead to the weakest inhibitory capacity of inhibitor 5e.

The intrinsic inductive properties of atoms or functional groups depend on the chemical properties of either electron-withdrawing groups (EWGs) or electron-donating groups (EDGs). This study aimed to evaluate in silico methods to determine whether changes in chemical properties of the compound by single atomic substitution affect the biological activity of target proteins and whether the results depend on the properties of the functional groups. We found an imidazo[4,5-b]pyridine-based PAK4 inhibitor, compound 1, as an initial hit compound with the well-defined binding mode for PAK4. In this study, we used both experimental and in silico methods to investigate the effect of atomic substitution on biological activity to optimize the initial hit compound. In biological assays, in the case of EWG, as the size of the halogen atom became smaller and the electronegativity increased, the biological activity IC50 value ranged from 5150 nM to inactive; in the case of EDG, biological activity was inactive. Furthermore, we analyzed the interactions of PAK4 with compounds, focusing on the hinge region residues, L398 and E399, and gatekeeper residues, M395 and K350, of the PAK4 protein using molecular docking studies and fragment molecular orbital (FMO) methods to determine the differences between the effect of EWG and EDG on the activity of target proteins. These results of the docking score and binding energy did not explain the differences in biological activity. However, the pair-interaction energy obtained from the results of the FMO method indicated that there was a difference in the interaction energy between the EWG and EDG in the hinge region residues, L398 and E399, as well as in M395 and K350. The two groups with different properties exhibited opposite electrostatic energy and charge transfer energy between L398 and E399. Additionally, we investigated the electron distribution of the parts interacting with the hinge region by visualizing the molecular electrostatic potential (MEP) surface of the compounds. In conclusion, we described the properties of functional groups that affect biological activity using an in silico method, FMO. [ABSTRACT FROM AUTHOR]

Aim: To explore the biological function of miR‐425/PAK4 axis in proliferation, metastasis, and apoptosis of ovarian cancer (OC) cells. Methods: qRT‐PCR and Western blot were adopted to examine miR‐425 and PAK4 expressions in OC tissues and cell lines. Cell counting kit‐8 (CCK‐8) and BrdU assays were applied to detect the proliferation ability of OC cells, and Transwell assay was adopted to assess the migration and invasion of OC cells. Flow cytometry was employed to evaluate the apoptosis of OC cells. The interaction between miR‐425 and PAK4 was predicted and verified by bioinformatics analysis and dual luciferase reporter gene assay, respectively. Results: miR‐425 was reduced in OC tissues and cell lines, and its underexpression was in evident correlation with the shorter overall survival time of OC patients. miR‐425 impeded OC cell proliferation, migration, and invasion, and accelerated apoptosis. Additionally, PAK4 was validated as the target of miR‐425, and the cotransfection of PAK4 reversed the antitumor effect of miR‐425. Conclusion: miR‐425 suppresses the proliferation, migration, and invasion of OC cells and enhances apoptosis via inhibiting PAK4, and it is expected to be a prognostic indicator and therapeutic target for the patients with OC. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Over 95% of Pancreatic ductal adenocarcinomas (PDA) carry mutations in the oncogene KRas which has been proven to be a difficult drug target. P21-activated kinase 4 (PAK4), acts downstream of KRas, and is overexpressed in PDA contributing to its growth and chemoresistance, and thus becomes an attractive therapeutic target. We have developed a new PAK4 inhibitor, PAKib and tested its effect on pancreatic cancer (PC) cell growth in vitro and in a syngeneic mouse model of PC. PAKib suppressed PC cell growth by inducing cell death and cycle arrest. PAKib inhibited PC growth and enhanced the inhibition by gemcitabine of PC in cell culture and in PC mouse model. PAKib acted through multiple signaling pathways involved in cell cycle checkpoints, apoptosis, cell junction, and focal adhesion. These proof-of-concept studies demonstrated the anti-cancer effect of PAKib alone and in combination with gemcitabine and warrant a further clinical investigation.

Background: Skeletal muscle regeneration is an adaptive response to injury that is crucial to the maintenance of muscle mass and function. A p21‐activated kinase 4 (PAK4) serine/threonine kinase is critical to the regulation of cytoskeletal changes, cell proliferation, and growth. However, PAK4's role in myoblast differentiation and regenerative myogenesis remains to be determined. Methods: We used a mouse model of myotoxin (notexin)‐induced muscle regeneration. In vitro myogenesis was performed in the C2C12 myoblast cell line, primary myoblasts, and primary satellite cells. In vivo overexpression of PAK4 or kinase‐inactive mutant PAK4S474A was conducted in skeletal muscle to examine PAK4's kinase‐dependent effect on muscle regeneration. The regeneration process was evaluated by determining the number and size of multinucleated myofibres and expression patterns of myogenin and eMyHC. To explore whether PAK4 inhibition improves muscle regeneration, mice were injected intramuscularly with siRNA that targeted PAK4 or orally administered with a chemical inhibitor of PAK4. Results: p21‐activated kinase 4 was highly expressed during the myoblast stage, but expression gradually and substantially decreased as myoblasts differentiated into myotubes. PAK4 overexpression, but not kinase‐inactive mutant PAK4S474A overexpression, significantly impeded myoblast fusion and MyHC‐positive myotube formation in C2C12 cells, primary myoblasts, and satellite cells (P < 0.01). Conversely, PAK4 silencing led to an 8.7% and a 20.3% increase in the number of multinucleated larger myotubes in C2C12 cells and primary myoblasts. Further, in vivo overexpression of PAK4 by adenovirus injection to mice prior to and after myotoxin‐induced injury led to a 52.6% decrease in the number of eMyHC‐positive myofibres on Day 5 in tibialis anterior muscles as compared with those injected with control adenoviruses (P < 0.01), while Ad‐PAK4S474A showed comparable muscle regeneration parameters. PAK4‐induced repression of muscle regeneration coincided with an increase in phosphatase and tensin homologue (PTEN) expression and a decrease in phosphoinositide 3‐kinase‐Akt signalling. In contrast, PAK4 silencing reduced PTEN expression in mice. Consistent with these findings, prodrug of PAK4 inhibitor CZh‐226 (30 mg/kg) orally administered to mice repressed PTEN expression and accelerated myotube formation. Subsequent mechanistic studies revealed that PAK4 directly phosphorylates PPARγ at S273 to increase its transcription activity, thereby up‐regulating PTEN expression. Importantly, an analysis of the Genotype‐Tissue Expression database showed a positive correlation between PAK4 and PTEN in human skeletal muscle tissues (P < 0.01). Conclusions: p1‐activated kinase 4 is a new member of PPARγ kinase, and PAK4 inhibition may have a therapeutic role as an accelerant of muscle regeneration. [ABSTRACT FROM AUTHOR]

Abstract Background Increasing studies have demonstrated that long non-coding RNAs (lncRNAs) play an important role in tumor progression. However, the potential biological functions and clinical importance of Linc01234 in oral squamous cell carcinoma (OSCC) remain unclear. Methods We evaluated the expression profile and prognostic value of Linc01234 in OSCC tissues by RT-qPCR. Then, functional in vitro experiments were performed to investigate the effects of Linc01234 on tumor growth, migration and invasion in OSCC. Mechanistically, RT-qPCR, bioinformatic analysis and dual luciferase reporter assays were performed to identify a competitive endogenous RNA (ceRNA) mechanism involving Linc01234, miR-433-3p and PAK4. Results We found that Linc01234 was clearly upregulated in OSCC tissues and cell lines, and its level was positively associated with T stage, lymph node metastasis, differentiation and poor prognosis of patients with OSCC. Our results shown that Linc01234 inhibited cell proliferation and metastatic abilities in CAL27 and SCC25 cells following its knockdown. Mechanistic analysis indicated that Linc01234 may act as a ceRNA (competing endogenous RNA) of miR-433-3p to relieve the repressive effect of miR-433-3p on its target PAK4. Conclusions Our results indicated that Linc01234 promotes OSCC progression through the Linc01234/miR-433/PAK4 axis and might be a potential therapeutic target for OSCC.

Yanshu Li, 1–3 Shiheng Jia, 3, 4 Wei Dai 5, 6 1Key Laboratory of Cell Biology, Ministry of Public Health, China Medical University, Shenyang, Liaoning, People’s Republic of China; 2Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, Shenyang, Liaoning, People’s Republic of China; 3Department of Cell Biology, China Medical University, Shenyang, Liaoning, People’s Republic of China; 4Department of Clinical Medicine, China Medical University, Shenyang, Liaoning, People’s Republic of China; 5Department of Oromaxillofacial-Head and Neck Surgery, School of Stomatology, China Medical University, Shenyang, Liaoning, People’s Republic of China; 6Department of Oral and Maxillofacial Surgery, School and Hospital of Stomatology, China Medical University, Liaoning Provincial Key Laboratory of Oral Diseases, Shenyang, Liaoning, People’s Republic of ChinaCorrespondence: Wei DaiDepartment of Oral and Maxillofacial Surgery, School and Hospital of Stomatology, China Medical University, Liaoning Provincial Key Laboratory of Oral Diseases, Shenyang, Liaoning 110002, People’s Republic of ChinaTel +86 139 0988 4820Email daicmu@163.comObjective: Human oral squamous cell carcinoma (OSCC) is a major cause of mortality and morbidity worldwide. There is an urgent need to identify bioactive molecules and potential target genes that could inhibit carcinogenesis for OSCC therapy. Fisetin (3,7,3′,4′-tetrahydroxyflavone), a naturally occurring flavonoid, has been previously shown to have anti-proliferative activities in OSCC; however, its molecular mechanism is unknown.Methods: Colony formation, cell viability, Boyden chamber, wound healing, and tumor xenograft assays were used to detect the impact of fisetin on OSCC cells in vitro and in vivo. Western blot analysis was used to examine the corresponding protein expression.Results: Fisetin treatment significantly inhibited proliferation and promoted apoptosis by repressing PAK4 expression. Moreover, fisetin treatment attenuated cell migration by blocking PAK4 signaling pathways. In addition, the tumor xenograft showed anti-tumor growth effects of fisetin exposure in vivo.Conclusion: Fisetin may represent a potential therapeutic strategy for human OSCC by targeting PAK4 signaling pathways.Keywords: OSCC, fisetin, PAK4, PARP

Abstract Background Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. P21-activated kinase 4 (PAK4) and miR-9-5p have emerged as attractive therapeutic targets in several tumor types, but in CRC, the regulation of their biological function and their target association remain unclear. Methods The expression of PAK4 in CRC tissues was determined using quantitative real-time PCR and immunohistochemistry analyses. The targeted regulation between miR-9-5p and PAK4 was predicted and confirmed with bioinformatics analysis and the dual-luciferase reporter assay. Functional experiments, including the MTT assay and flow cytometry, were performed to investigate the impact of PAK4 knockdown and miR-9-5p overexpression on cell proliferation and apoptosis in CRC cells. Results We found that the expression of PAK4 was upregulated in CRC tissues. PAK4 knockdown significantly suppressed cell proliferation and promoted apoptosis in cells of the CRC cell lines HCT116 and SW1116. We also found that miR-9-5p directly targeted the 3′-UTR of PAK4 mRNA and negatively regulated its expression. The degree of downregulation of miR-9-5p inversely correlated with PAK4 expression. Intriguingly, enforced expression of miR-9-5p suppressed cell proliferation and promoted apoptosis. This could be partially reversed by PAK4 overexpression. Conclusion These results suggest that miR-9-5p targeting of PAK4 could have therapeutic potential for CRC treatment.

Background: Finding the oncogene, which was able to inhibit tumor cells intrinsically and improve the immune answers, will be the future direction for renal cancer combined treatment. Following patient sample analysis and signaling pathway examination, we propose p21-activated kinase 4 (PAK4) as a potential target drug for kidney cancer. PAK4 exhibits high expression levels in patient samples and plays a regulatory role in the immune microenvironment., Methods: Utilizing AI software for peptide drug design, we have engineered a specialized peptide proteolysis targeting chimera (PROTAC) drug with selectivity for PAK4. To address challenges related to drug delivery, we developed a nano-selenium delivery system for efficient transport of the peptide PROTAC drug, termed PpD (PAK4 peptide degrader)., Findings: We successfully designed a peptide PROTAC drug targeting PAK4. PpD effectively degraded PAK4 with high selectivity, avoiding interference with other homologous proteins. PpD significantly attenuated renal carcinoma proliferation in vitro and in vivo. Notably, PpD demonstrated a significant inhibitory effect on tumor proliferation in a fully immunocompetent mouse model, concomitantly enhancing the immune cell response. Moreover, PpD demonstrated promising tumor growth inhibitory effects in mini-PDX and PDO models, further underscoring its potential for clinical application., Interpretation: This PAK4-targeting peptide PROTAC drug not only curtails renal cancer cell proliferation but also improves the immune microenvironment and enhances immune response. Our study paves the way for innovative targeted therapies in the management of renal cancer., Funding: This work is supported by Research grants from non-profit organizations, as stated in the Acknowledgments., Competing Interests: Declaration of interests All other authors declare they have no competing interests., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Protein kinases and phosphatases regulate cellular processes by reversible phosphorylation and dephosphorylation events. CPPED1 is a recently identified serine/threonine protein phosphatase that dephosphorylates AKT1 of the PI3K-AKT signalling pathway. We previously showed that CPPED1 levels are down-regulated in the human placenta during spontaneous term birth. In this study, based on sequence comparisons, we propose that CPPED1 is a member of the class III phosphodiesterase (PDE) subfamily within the calcineurin-like metallophosphoesterase (MPE) superfamily rather than a member of the phosphoprotein phosphatase (PPP) or metal-dependent protein phosphatase (PPM) protein families. We used a human proteome microarray to identify 36 proteins that putatively interact with CPPED1. Of these, GRB2, PAK4 and PIK3R2 are known to regulate the PI3K-AKT pathway. We further confirmed CPPED1 interactions with PAK4 and PIK3R2 by coimmunoprecipitation analyses. We characterized the effect of CPPED1 on phosphorylation of PAK4 and PIK3R2 in vitro by mass spectrometry. CPPED1 dephosphorylated specific serine residues in PAK4, while phosphorylation levels in PIK3R2 remained unchanged. Our findings indicate that CPPED1 may regulate PI3K-AKT pathway activity at multiple levels. Higher CPPED1 levels may inhibit PI3K-AKT pathway maintaining pregnancy. Consequences of decreased CPPED1 expression during labour remain to be elucidated. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) is characterized by a progressive loss of dopamine-producing neurons in the midbrain, which results in decreased dopamine levels accompanied by movement symptoms. Oral administration of l-3,4-dihydroxyphenylalanine (L-dopa), the precursor of dopamine, provides initial symptomatic relief, but abnormal involuntary movements develop later. A deeper understanding of the regulatory mechanisms underlying dopamine homeostasis is thus critically needed for the development of a successful treatment. Here, we show that p21-activated kinase 4 (PAK4) controls dopamine levels. Constitutively active PAK4 (caPAK4) stimulated transcription of tyrosine hydroxylase (TH) via the cAMP response element-binding protein (CREB) transcription factor. Moreover, caPAK4 increased the catalytic activity of TH through its phosphorylation of S40, which is essential for TH activation. Consistent with this result, in human midbrain tissues, we observed a strong correlation between phosphorylated PAK4S474, which represents PAK4 activity, and phosphorylated THS40, which reflects their enzymatic activity. Our findings suggest that targeting the PAK4 signaling pathways to restore dopamine levels may provide a new therapeutic approach in PD. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD) provokes bradykinesia, resting tremor, rigidity and postural instability, and also non-motor symptoms such as depression, anxiety, sleep and cognitive impairments. Similar phenotypes can be induced in Drosophila melanogaster through modification of PD-relevant genes or the administration of PD-inducing toxins. Recent studies correlated deregulation of human p21-activated kinase 4 (PAK4) with PD, leaving open the question of a causative relationship of mutations in this gene for manifestation of PD symptoms. To determine whether flies lacking the PAK4 homolog Mushroom bodies tiny (Mbt) show PD-like phenotypes, we tested for a variety of PD criteria. Here, we demonstrate that mbt mutant flies show PD-like phenotypes including age-dependent movement deficits, reduced life expectancy and fragmented sleep. They also react to a stressful situation with higher immobility, indicating an influence of Mbt on emotional behavior. Loss of Mbt function has a negative effect on the number of dopaminergic protocerebral anterior medial (PAM) neurons, most likely caused by a proliferation defect of neural progenitors. The age-dependent movement deficits are not accompanied by a corresponding further loss of PAM neurons. Previous studies highlighted the importance of a small PAM subgroup for age-dependent PD motor impairments. We show that impaired motor skills are caused by a lack of Mbt in this PAM subgroup. In addition, a broader re-expression of Mbt in PAM neurons improves life expectancy. Conversely, selective Mbt knockout in the same cells shortens lifespan. We conclude that mutations in Mbt/PAK4 can play a causative role in the development of PD phenotypes.

Abstract The aim of this study is to investigate the functions and mechanisms of miR‐608 in prostate cancer (PCa). CISH and qRT‐PCR analysis demonstrated that miR‐608 was low expressed in PCa tissues and cells, which was partly attributed to the methylation of CpG island adjacent to the transcription start site (TSS) of miR‐608 gene. Intracellular miR‐608 overexpression inhibited in vivo PCa tumor growth, and suppressed PCa cell proliferation, G2/M transition, and migration in vitro, which was independent of EMT‐associated mechanisms. Then RAC2, a GTPase previously deemed hematopoiesis‐specific but now discovered to exist and play important roles in PCa, was verified by western blot and dual‐luciferase reporter assays to mediate the effects of miR‐608 through RAC2/PAK4/LIMK1/cofilin pathway. MiR‐608 also promoted the apoptosis of PCa cells through BCL2L1/caspase‐3 pathway by targeting the 3′‐UTR of BCL2L1. Moreover, PAK4, the downstream effector of RAC2, was found to be targeted by miR‐608 at the mRNA coding sequence (CDS) instead of the canonical 3′‐UTR. Knocking down RAC2, PAK4, or BCL2L1 with siRNAs reproduced the antiproliferative, mitosis‐obstructive, antimigratory and proapoptotic effects of miR‐608 in PCa cells, which could be attenuated by downregulating miR‐608. In conclusion, miR‐608 suppresses PCa progression, and its activation provides a new therapeutic option for PCa.

Introduction Long intergenic non-protein-coding RNA 1296 (LINC01296), a newly identified lncRNA, can function as an oncogenic driver to promote the development of multiple carcinomas. However, the effect of LINC01296 on oral squamous cell carcinoma (OSCC) is still unclear. Material and methods We determined the expression and role of LINC01296 in OSCC tissues and cell lines. The cell viability, migration and invasion were determined by MTT, wound healing assay and transwell assay, respectively. Flow cytometry was used for detecting cell cycle and apoptosis. The interaction and association between LINC01296, microRNA-485-5p (miR-485-5p) and p21 (RAC1) activated kinase 4 (PAK4) were analyzed by RNA immunoprecipitation (RIP) and luciferase reporter assays. The xenograft mouse model was established to detect the effect of LINC01296 on OSCC tumor growth. Results Our study showed that LINC01296 was over-expressed in OSCC tissues and cell lines. The level of LINC01296 was positively correlated with the patient’s tumor node metastasis (TNM) stage and nodal invasion. Knockdown of LINC01296 effectively inhibits cell viability, migration and invasion but promotes cell apoptosis in vitro. The in vivo experiment showed that LINC01296 knockdown inhibited OSCC tumor growth. The following analysis indicated that LINC01296 acted as a ceRNA for miR-485-5p, and PAK4 was identified as a direct target of miR-485-5p. Furthermore, we found that the effects of LINC01296 on OSCC progression were through regulating the expression of PAK4/p-MEK/p-ERK via sponging miR-485-5p. Conclusions LINC01296 promote the cell cycle, proliferation, migration and invasion, and inhibit apoptosis of OSCC cells through activating the MAPK/ERK signaling pathway via sponging miR-485-5p to regulate PAK4 expression. These results suggested that the LINC01296/miR-485-5p/PAK4 axis was closely associated with OSCC progression. Our study provides a new insight into the molecular pathogenesis of OSCC, and may supply novel biomarkers for diagnosis and therapy of OSCC.

The intrinsic inductive properties of atoms or functional groups depend on the chemical properties of either electron-withdrawing groups (EWGs) or electron-donating groups (EDGs). This study aimed to evaluate in silico methods to determine whether changes in chemical properties of the compound by single atomic substitution affect the biological activity of target proteins and whether the results depend on the properties of the functional groups. We found an imidazo[4,5-b]pyridine-based PAK4 inhibitor, compound 1, as an initial hit compound with the well-defined binding mode for PAK4. In this study, we used both experimental and in silico methods to investigate the effect of atomic substitution on biological activity to optimize the initial hit compound. In biological assays, in the case of EWG, as the size of the halogen atom became smaller and the electronegativity increased, the biological activity IC50 value ranged from 5150 nM to inactive; in the case of EDG, biological activity was inactive. Furthermore, we analyzed the interactions of PAK4 with compounds, focusing on the hinge region residues, L398 and E399, and gatekeeper residues, M395 and K350, of the PAK4 protein using molecular docking studies and fragment molecular orbital (FMO) methods to determine the differences between the effect of EWG and EDG on the activity of target proteins. These results of the docking score and binding energy did not explain the differences in biological activity. However, the pair-interaction energy obtained from the results of the FMO method indicated that there was a difference in the interaction energy between the EWG and EDG in the hinge region residues, L398 and E399, as well as in M395 and K350. The two groups with different properties exhibited opposite electrostatic energy and charge transfer energy between L398 and E399. Additionally, we investigated the electron distribution of the parts interacting with the hinge region by visualizing the molecular electrostatic potential (MEP) surface of the compounds. In conclusion, we described the properties of functional groups that affect biological activity using an in silico method, FMO.

Exosomes play important role in tumor microenvironment, and mediate the crosstalk between pancreatic cancer (PC) cells and matrix components including pancreatic stellate cells (PSCs) to regulate pancreatic cancer progression. Here we isolated primary PSCs from PC patients, and demonstrated that PSC-derived exosomes could be internalized by PC cells to promote cell proliferation. Furthermore, we identified that miR-5703 in the exosomes acted as a driver of cell proliferation and its inhibitor suppressed the function of exosomes to promote PC cell proliferation. miR-5703 directly bound to the 3'UTR of CMTM4 and downregulated its expression. CMTM4 knockdown promoted PC cell proliferation, while overexpression of CMTM4 suppressed PC cell proliferation both in vivo and in vitro. Mechanistically, we revealed that CMTM4 suppressed PI3K/Akt pathway via downregulating PAK4. In conclusion, our results suggest that PSC-derived exosomal miR-5703 could target CMTM4 in PC cells and promote cell proliferation due to PAK4 activated PI3K/Akt pathway. [ABSTRACT FROM AUTHOR]

Normal cells exposed to cancer-causing events respond by triggering cellular senescence, a stress response which halts cell proliferation and constitutes a protective anti-cancer barrier. We have uncovered a previously unknown signaling pathway implicating p21-activated kinase 4 (PAK4) in the control of senescence in breast cancer, via the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) subunit RELB and the CCAAT-enhancer-binding protein beta (C/EBPβ).

Abstract 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.

Diffuse large B-cell lymphoma (DLBCL), grade 3b follicular lymphoma (FL), and mantle cell lymphoma (MCL) are aggressive non-Hodgkin’s lymphomas (NHL). Cure rates are suboptimal and novel treatment strategies are needed to improve outcomes. Here, we show that p21-activated kinase 4 (PAK4) and nicotinamide phosphoribosyl transferase (NAMPT) is critical for lymphoma subsistence. Dual targeting of PAK4-NAMPT by the Phase I small molecule KPT-9274 suppressed cell proliferation in DLBCL, FL, and MCL. Growth inhibition was concurrent with apoptosis induction alongside activation of pro-apoptotic proteins and reduced pro-survival markers. We observed NAD suppression, ATP reduction, and consequent cellular metabolic collapse in lymphoma cells due to KPT-9274 treatment. KPT-9274 in combination with standard-of-care chemotherapeutics led to superior inhibition of cell proliferation. In vivo, KPT-9274 could markedly suppress the growth of WSU-DLCL2 (DLBCL), Z-138, and JeKo-1 (MCL) sub-cutaneous xenografts, and a remarkable increase in host life span was shown, with a 50% cure of a systemic WSU-FSCCL (FL) model. Residual tumor analysis confirmed a reduction in total and phosphorylated PAK4 and activation of the pro-apoptotic cascade. This study, using various preclinical experimental models, demonstrates the therapeutic potential of targeting PAK4-NAMPT in DLBCL, FL, and MCL. The orally bioavailable, safe, and efficacious PAK4-NAMPT dual inhibitor KPT-9274 warrants further clinical investigation.

PAK4 is the only member of the Group II p21-activated kinases (PAKs) present in rat pancreatic acinar cells and is activated by gastrointestinal hormones/neurotransmitters stimulating PLC/cAMP and by various pancreatic growth factors. However, little is known of the role of PAK4 activation in cellular signaling cascades in pancreatic acinar cells. In the present study, we examined the role of PAK4's participation in five different cholecystokinin-8 (CCK-8)-stimulated signaling pathways (PI3K/Akt, MAPK, focal adhesion kinase, GSK3, and β-catenin), which mediate many of its physiological acinar-cell effects, as well as effects in pathophysiological conditions. To define PAK4's role, the effect of two different PAK4 inhibitors, PF-3758309 and LCH-7749944, was examined under experimental conditions that only inhibited PAK4 activation and not activation of the other pancreatic PAK, Group I PAK2. The inhibitors' effects on activation of these five signaling cascades by both physiological and pathophysiological concentrations of CCK, as well as by 12-O-tetradecanoylphobol-13-acetate (TPA), a PKC-activator, were examined. CCK/TPA activation of focal adhesion kinases(PYK2/p125FAK) and the accompanying adapter proteins (paxillin/p130CAS), Mek1/2, and p44/42, but not c-Raf or other MAPKs (JNK/p38), were mediated by PAK4. Activation of PI3K/Akt/p70s6K was independent of PAK4, whereas GSK3 and β-catenin stimulation was PAK4-dependent. These results, coupled with recent studies showing PAK4 is important in pancreatic fluid/electrolyte/enzyme secretion and acinar cell growth, show that PAK4 plays an important role in different cellular signaling cascades, which have been shown to mediate numerous physiological and pathophysiological processes in pancreatic acinar cells. NEW & NOTEWORTHY In pancreatic acinar cells, cholecystokinin (CCK) or 12-O-tetradecanoylphobol-13-acetate (TPA) activation of focal adhesion kinases (p125FAK,PYK2) and its accompanying adapter proteins, p130CAS/paxillin; Mek1/2, p44/42, GSK3, and β-catenin are mediated by PAK4. PI3K/Akt/p70s6K, c-Raf, JNK, or p38 pathways are independent of PAK4 activation. [ABSTRACT FROM AUTHOR]

Background: Increasing studies have demonstrated that long non-coding RNAs (lncRNAs) play an important role in tumor progression. However, the potential biological functions and clinical importance of Linc01234 in oral squamous cell carcinoma (OSCC) remain unclear.Methods: We evaluated the expression profile and prognostic value of Linc01234 in OSCC tissues by RT-qPCR. Then, functional in vitro experiments were performed to investigate the effects of Linc01234 on tumor growth, migration and invasion in OSCC. Mechanistically, RT-qPCR, bioinformatic analysis and dual luciferase reporter assays were performed to identify a competitive endogenous RNA (ceRNA) mechanism involving Linc01234, miR-433-3p and PAK4.Results: We found that Linc01234 was clearly upregulated in OSCC tissues and cell lines, and its level was positively associated with T stage, lymph node metastasis, differentiation and poor prognosis of patients with OSCC. Our results shown that Linc01234 inhibited cell proliferation and metastatic abilities in CAL27 and SCC25 cells following its knockdown. Mechanistic analysis indicated that Linc01234 may act as a ceRNA (competing endogenous RNA) of miR-433-3p to relieve the repressive effect of miR-433-3p on its target PAK4.Conclusions: Our results indicated that Linc01234 promotes OSCC progression through the Linc01234/miR-433/PAK4 axis and might be a potential therapeutic target for OSCC. [ABSTRACT FROM AUTHOR]