p21-activated kinase 4 regulates ovarian cancer cell proliferation, migration, and invasion and contributes to poor prognosis in patients. Proc Natl Acad Sci U S A. 2010;107:18622-18627. [PMID: 20926745 DOI: 10.1073/pnas.0907481107]

The Role of the p21-Activated Kinase Family in Tumor Immunity

The p21-activated kinases (PAKs) are a group of evolutionarily conserved serine/threonine protein kinases and serve as a downstream target of the small GTPases Rac and Cdc42, both of which belong to the Rho family. PAKs play pivotal roles in various physiological processes, including cytoskeletal rearrangement and cellular signal transduction. Group II PAKs (PAK4-6) are particularly closely linked to human tumors, such as breast and pancreatic cancers, while Group I PAKs (PAK1-3) are indispensable for normal physiological functions such as cardiovascular development and neurogenesis. In recent years, the association of PAKs with diseases like cancer and the rise of small-molecule inhibitors targeting PAKs have attracted significant attention. This article focuses on the analysis of PAKs' role in tumor progression and immune infiltration, as well as the current small-molecule inhibitors of PAKs and their mechanisms.

Design, synthesis and biological evaluation of novel benzimidazole-derived p21-activited kinase 4 (PAK4) inhibitors bearing a 4-(4-methylpiperazin-1-yl)phenyl scaffold as potential antitumor agents

A series of novel 6-(4-(4-methylpiperazin-1-yl)phenyl)-1H-benzo[d]imidazole-based p21-activited kinase 4 (PAK4) inhibitors were designed and synthesized based on the structure of lead compound GNE-2861 and that of anticancer inhibitors reported in our previous studies. All target compounds so designed were preliminarily screened in vitro for anti-tumor potency through kinase inhibitory assays and MTT assays, which revealed that most compounds exhibited significant inhibitory effects on PAK4 enzyme as well as prominent antiproliferative activities against four cancer cell models (A549, NCI-H1975, MDA-MB-231 and SK-BR-3) and low damage to healthy cells. In particular, the hit compound 12i was identified as the most effective and rather selective compound both at the enzyme and cellular level. Meanwhile, molecular docking and dynamic studies disclosed that compound 12i could bind to PAK4 stably via multiple interactions applied between the compound and the enzyme. Further mechanism studies indicated that compound 12i could inhibit the proliferation and suppress the migratory potential of MDA-MB-231 cells by inhibiting the phosphorylation of PAK4 and LIMK1, arresting cell cycle in the G0/G1 phase, inducing apoptosis and promoting ROS production. Notably, compound 12i could effectively inhibit triple-negative breast cancer (TNBC) growth with little toxicity in the MDA-MB-231 cell xenograft model. Taken together, in vitro and in vivo results demonstrated that compound 12i possessed high drug potential as an inhibitor of PAK4 to inhibit the growth and metastasis of TNBC.

PAK4 Is Involved in the Stabilization of PD-L1 and the Resistance to Doxorubicin in Osteosarcoma and Predicts the Survival of Diagnosed Patients

PAK4 and PD-L1 have been suggested as novel therapeutic targets in human cancers. Moreover, PAK4 has been suggested to be a molecule closely related to the immune evasion of cancers. Therefore, this study evaluated the roles of PAK4 and PD-L1 in the progression of osteosarcomas in 32 osteosarcomas and osteosarcoma cells. In human osteosarcomas, immunohistochemical positivity for the expression of PAK4 (overall survival, p = 0.028) and PD-L1 (relapse-free survival, p = 0.002) were independent indicators for the survival of patients in a multivariate analysis. In osteosarcoma cells, the overexpression of PAK4 increased proliferation and invasiveness, while the knockdown of PAK4 suppressed proliferation and invasiveness. The expression of PAK4 was associated with the expression of the molecules related to cell cycle regulation, invasion, and apoptosis. PAK4 was involved in resistance to apoptosis under a treatment regime with doxorubicin for osteosarcoma. In U2OS cells, PAK4 was involved in the stabilization of PD-L1 from ubiquitin-mediated proteasomal degradation and the in vivo infiltration of immune cells such as regulatory T cells and PD1-, CD4-, and CD8-positive cells in mice tumors. In conclusion, this study suggests that PAK4 is involved in the progression of osteosarcoma by promoting proliferation, invasion, and resistance to doxorubicin and stabilized PD-L1 from proteasomal degradation.

Tumorigenic role of Pak4 in ovarian cancer and its correlation with immune infiltration

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.

Targeting PAK4 reverses cisplatin resistance in NSCLC by modulating ER stress

Chemoresistance poses a significant impediment to effective treatments for non-small-cell lung cancer (NSCLC). P21-activated kinase 4 (PAK4) has been implicated in NSCLC progression by invasion and migration. However, the involvement of PAK4 in cisplatin resistance is not clear. Here, we presented a comprehensive investigation into the involvement of PAK4 in cisplatin resistance within NSCLC. Our study revealed enhanced PAK4 expression in both cisplatin-resistant NSCLC tumors and cell lines. Notably, PAK4 silencing led to a remarkable enhancement in the chemosensitivity of cisplatin-resistant NSCLC cells. Cisplatin evoked endoplasmic reticulum stress in NSCLC. Furthermore, inhibition of PAK4 demonstrated the potential to sensitize resistant tumor cells through modulating endoplasmic reticulum stress. Mechanistically, we unveiled that the suppression of the MEK1-GRP78 signaling pathway results in the sensitization of NSCLC cells to cisplatin after PAK4 knockdown. Our findings establish PAK4 as a promising therapeutic target for addressing chemoresistance in NSCLC, potentially opening new avenues for enhancing treatment efficacy and patient outcomes.

p21-activated kinase 4 counteracts PKA-dependent lipolysis by phosphorylating FABP4 and HSL

Adipose tissue lipolysis is mediated by cAMP-protein kinase A (PKA)-dependent intracellular signalling. Here, we show that PKA targets p21-activated kinase 4 (PAK4), leading to its protein degradation. Adipose tissue-specific overexpression of PAK4 in mice attenuates lipolysis and exacerbates diet-induced obesity. Conversely, adipose tissue-specific knockout of Pak4 or the administration of a PAK4 inhibitor in mice ameliorates diet-induced obesity and insulin resistance while enhancing lipolysis. Pak4 knockout also increases energy expenditure and adipose tissue browning activity. Mechanistically, PAK4 directly phosphorylates fatty acid-binding protein 4 (FABP4) at T126 and hormone-sensitive lipase (HSL) at S565, impairing their interaction and thereby inhibiting lipolysis. Levels of PAK4 and the phosphorylation of FABP4-T126 and HSL-S565 are enhanced in the visceral fat of individuals with obesity compared to their lean counterparts. In summary, we have uncovered an important role for FABP4 phosphorylation in regulating adipose tissue lipolysis, and PAK4 inhibition may offer a therapeutic strategy for the treatment of obesity.

Design, synthesis and anticancer activity evaluation of 4-(3-1H-indazolyl)amino quinazoline derivatives as PAK4 inhibitors

A novel series of 4-(3-1H-indazolyl)amino quinazoline derivatives were developed as PAK4 inhibitors based on a scaffold hopping strategy. Compounds 27e, 27g, 27i and 27j were found to exhibit potent inhibitory activity against PAK4 (IC50 = 10, 13, 11 and 9 nM, respectively). Subsequent cellular assay demonstrated that compound 27e possessed the strongest antiproliferative activity against A549 cells with an IC50 value of 0.61 μM, a little bit better than PF-3758309. Further anticancer mechanistic investigation revealed that compound 27e significantly induced apoptosis of A549 cells in a concentration-dependent manner and blocked the cell cycle at phase G0/G1. A docking model between compound 27e and PAK4 was proposed to elucidate its possible binding modes. As a promising PAK4 inhibitor, compound 27e may serve as a candidate for the development of novel PAK4-targeted anticancer drug.

miR-224-5p acts as a tumour suppressor and reverses the resistance to BRAF inhibitor in melanoma through directly targeting PAK4 to block the MAPK pathway

miR-224-5p has been shown to play both an oncogene and tumour suppressor role in many human tumours. However, the role and molecular mechanism of miR-224-5p in cutaneous melanoma remains unclear. miR-224-5p levels were downregulated in melanoma tissue, and low miR-224-5p expression was an independent risk factor for melanoma patients. miR-224-5p blocked proliferation, epithelial-to-mesenchymal transition (EMT), invasion, migration in BRAF wild-type melanoma cell, and overcome acquired BRAFi resistance in VMF-resistant melanoma cells. miR-224-5p exerted its role by directly repressing PAK4 to block the downstream CRAF/MEK/ERK pathways. We demonstrated that miR-224-5p inhibited melanoma growth and metastasis in vivo though xenograft tumor and pulmonary metastasis assay. Thus, miR-224-5p/PAK4-mediated CRAF/MEK/ERK pathways have therapeutic potential in melanoma treatment.

Molecular biology of microRNA-342 during tumor progression and invasion

Cancer is considered as one of the main causes of human deaths and health challenges in the world. Various factors are involved in the high death rate of cancer patients, including late diagnosis and drug resistance that result in treatment failure and tumor recurrence. Invasive diagnostic methods are one of the main reasons of late tumor detection in cancer patients. Therefore, it is necessary to investigate the molecular tumor biology to introduce efficient non-invasive markers. MicroRNAs (miRNAs) are involved in regulation of the cellular mechanisms such as cell proliferation, apoptosis, and migration. MiRNAs deregulations have been also frequently shown in different tumor types. Here, we discussed the molecular mechanisms of miR-342 during tumor growth. MiR-342 mainly functions as a tumor suppressor by the regulation of transcription factors and signaling pathways such as WNT, PI3K/AKT, NF-kB, and MAPK. Therefore, miR-342 mimics can be used as a reliable therapeutic strategy to inhibit the tumor cells growth. The present review can also pave the way to introduce the miR-342 as a non-invasive diagnostic/prognostic marker in cancer patients.

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.

Combination of PAKs inhibitors IPA-3 and PF-3758309 effectively suppresses colon carcinoma cell growth by perturbing DNA damage response

PURPOSE

PAKs proteins are speculated as new promising targets for cancer therapy due to their central role in many oncogenic pathways. Because PAKs proteins are very significant during carcinogenesis, we aimed to investigate the hypothesis that inhibition of PAKs with IPA-3 and PF-3758309 treatment could synergistically reduce colon carcinoma cell growth.

MATERIALS AND METHODS

The cytotoxic effects of both drugs were determined by a cell viability assay. Cell cycle and apoptosis were analyzed by flow cytometry. The effects of inhibitor drugs on marker genes of apoptosis, autophagy, cell cycle, and DNA damage were tested via immunoblotting.

RESULTS AND CONCLUSIONS

We found out the synergistic effect of these drugs in pair on five colon cancer cell lines. Combined treatment with IPA-3+PF-3758309 in SW620 and Colo 205 cells markedly suppressed colon formation and induced apoptosis, cell cycle arrest, and autophagy compared with treatment with each drug alone. Additionally, this combination sensitized colon cancer cells to ionizing radiation that resulted in inhibition of cell growth.

SIGNIFICANCE

Collectively, our findings show for the first time that cotreatment of IPA-3 with PF-3758309 exhibits superior inhibitory effects on colon carcinoma cell growth via inducing DNA damage-related cell death and also enforces a cell cycle arrest.

Remodeling of the tumor microenvironment through PAK4 inhibition sensitizes tumors to immune checkpoint blockade

PAK4 inhibition can sensitize tumors to immune checkpoint blockade (ICB) therapy, however, the underlying mechanisms remain unclear. We report that PAK4 inhibition reverses immune cell exclusion by increasing the infiltration of CD8 T cells and CD103+ dendritic cells (DCs), a specific type of DCs that excel at cross-presenting tumor antigens and constitute a source of CXCL10. Interestingly, in melanoma clinical datasets, PAK4 expression levels negatively correlate with the presence of CCL21, the ligand for CCR7 expressed in CD103+ DCs. Furthermore, we extensively characterized the transcriptome of PAK4 knock out (KO) tumors, in vitro and in vivo, and established the importance of PAK4 expression in the regulation of the extracellular matrix, which can facilitate immune cell infiltration. Comparison between PAK4 wild type (WT) and KO anti-PD-1 treated tumors revealed how PAK4 deletion sensitizes tumors to ICB from a transcriptomic perspective. In addition, we validated genetically and pharmacologically that inhibition of PAK4 kinase activity is sufficient to improve anti-tumor efficacy of anti-PD-1 blockade in multiple melanoma mouse models. Therefore, this study provides novel insights into the mechanism of action of PAK4 inhibition and provides the foundation for a new treatment strategy that aims to overcome resistance to PD-1 blockade by combining anti-PD-1 with a small molecule PAK4 kinase inhibitor.

PAK4 expression is associated with the prognosis in non-small cell lung cancer

This study attempted to determine the expression of p21-activated kinase 4 (PAK4) in non-small cell lung cancer (NSCLC) tissues and the normal lung tissues. The correlation between PAK4 expression and prognosis of NSCLC patients was also evaluated in the present study. The expression level of PAK4 was measured by high-performance liquid chromatography method. Chi-square test was adopted to explore the relationship of PAK4 expression and clinical features. Kaplan-Meier survival curves were plotted to delineate the overall survival rate of NSCLC patients. Cox regression analysis was performed to evaluate the prognostic significance of PAK4 expression in NSCLC. The PAK4 expression in NSCLC tissue samples was significantly higher than that in normal lung tissues (P<0.001) and shared significant correlation with Eastern Cooperative Oncology Group score, histological type, and distant metastasis (P<0.05). Survival curve revealed that NSCLC patients with high PAK4 expression had relatively higher mortality than those with low PAK4 expression (P = .001). Cox regression analysis explained that PAK4 expression was associated with the prognosis of NSCLC patients (P = .024; HR, 3.104; 95% CI, 1.164-8.278). In a word, PAK4 was highly expressed in NSCLC tissues and could act as a prognostic factor for NSCLC patients.

p21-activated kinase 4 inhibition protects against liver ischemia/reperfusion injury: Role of nuclear factor erythroid 2-related factor 2 phosphorylation

BACKGROUND AND AIMS

p21-activated kinase 4 (PAK4), an oncogenic protein, has emerged as a promising target for anticancer drug development. Its role in oxidative stress conditions, however, remains elusive. We investigated the effects of PAK4 signaling on hepatic ischemia/reperfusion (I/R) injury.

APPROACH AND RESULTS

Hepatocyte- and myeloid-specific Pak4 knockout (KO) mice and their littermate controls were subjected to a partial hepatic I/R (HIR) injury. We manipulated the catalytic activity of PAK4, either through genetic engineering (gene knockout, overexpression of wild-type [WT] or dominant-negative kinase) or pharmacological inhibitor, coupled with a readout of nuclear factor erythroid 2-related factor 2 (Nrf2) activity, to test the potential function of PAK4 on HIR injury. PAK4 expression was markedly up-regulated in liver during HIR injury in mice and humans. Deletion of PAK4 in hepatocytes, but not in myeloid cells, ameliorated liver damages, as demonstrated in the decrease in hepatocellular necrosis and inflammatory responses. Conversely, the forced expression of WT PAK4 aggravated the pathological changes. PAK4 directly phosphorylated Nrf2 at T369, and it led to its nuclear export and proteasomal degradation, all of which impaired antioxidant responses in hepatocytes. Nrf2 silencing in liver abolished the protective effects of PAK4 deficiency. A PAK4 inhibitor protected mice from HIR injury.

CONCLUSIONS

PAK4 phosphorylates Nrf2 and suppresses its transcriptional activity. Genetic or pharmacological suppression of PAK4 alleviates HIR injury. Thus, PAK4 inhibition may represent a promising intervention against I/R-induced liver injury.

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.

Synthesis of selective PAK4 inhibitors for lung metastasis of lung cancer and melanoma cells

The p21 activated kinase 4 (PAK4) is serine/threonine protein kinase that is critical for cancer progression. Guided by X-ray crystallography and structure-based optimization, we report a novel subseries of C-3-substituted 6-ethynyl-1H-indole derivatives that display high potential and specificity towards group II PAKs. Among these inhibitors, compound 55 exhibited excellent inhibitory activity and kinase selectivity, displayed superior anti-migratory and anti-invasive properties against the lung cancer cell line A549 and the melanoma cell line B16. Compound 55 exhibited potent in vivo antitumor metastatic efficacy, with over 80% and 90% inhibition of lung metastasis in A549 or B16-BL6 lung metastasis models, respectively. Further mechanistic studies demonstrated that compound 55 mitigated TGF-β1-induced epithelial-mesenchymal transition (EMT).

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.

The role of PAK4 in the immune system and its potential implication in cancer immunotherapy

The p21 activated kinases (PAKs) are known to play a role in the regulation of cell morphology and functions. Among the various members of PAKs family, only the PAK4 protein has been shown to be overexpressed in cancer cells and its upregulation was associated with tumor development. Indeed, several studies have shown that PAK4 overexpression is implicated in carcinogenesis by different mechanisms including promotion of cell proliferation, invasion and migration, protection of cells from apoptosis, stimulation of the tumor-specific anchorage-independent cell growth and regulation of the cytoskeletal organisation and adhesion. Moreover, high PAK4 protein levels have been observed in several solid tumors and have been shown able to enhance cancer cell resistance to many treatments especially chemotherapy. Interestingly, it has been recently demonstrated that PAK4 downregulation can inhibit the PD-1/PD-L1 immune regulatory pathway. Taken together, these findings not only implicate PAK4 in oncogenic transformation and in prediction of tumor response to treatment but also suggest its role as an attractive target for immunotherapy. In the current review we will summarize the different mechanisms of PAK4 implication in tumor development, describe its role as a regulator of the immune response and as a potential novel target for cancer immunotherapy.

Drug discovery targeting p21-activated kinase 4 (PAK4): a patent review

Introduction: The Ser/Thr protein kinase PAK4 is a downstream regulator of Cdc42, mediating cytoskeleton remodeling, and cell motility, and inhibiting apoptosis and transcriptional regulation. Nowadays, efforts in PAK4 inhibitor development are focusing on improving inhibitory selectivity, cellular potency, and in vivo pharmacokinetic properties, and identifying the feasibility of immunotherapy combination in oncology therapy.Areas covered: This review summarized the development of PAK4 inhibitors that reported on patents in the past two decades. According to their binding features, these inhibitors were classified into type I, type I 1/2, and PAMs. Their designing ideas and SAR were elucidated in this review. Moreover, synergistic therapy of PAK4 inhibitors with PD-1/PD-L1 or CAR-T were also summarized .Expert opinion: In the past years, preclinical and clinical studies of PAK4 inhibitors ended in failure due to poor selectivity, cellular activity, or pharmacokinetic issues. There are researchers questioning the reliability of PAK4 as a drug target, particularly PAK4-related therapy is concerned with the distinguishment of the non-kinase functions and catalytic functions triggered by PAK4 phosphorylation. Meanwhile, synergistic effects of PAK4 inhibitors with PD-1/PD-L1 and CAR-T immunotherapy shed light for the development of PAK4 inhibitors.

hsa-miR-199a-3p Inhibits Motility, Invasiveness, and Contractility of Ovarian Endometriotic Stromal Cells

It is suggested that aberrantly expressed microRNAs are involved in the pathogenesis of endometriosis. Our previous study demonstrated that expression of the microRNA hsa-miR-199a-3p is attenuated in human endometriotic cyst stromal cells (ECSCs). The current study aimed to define the roles of hsa-miR-199a-3p in the development of endometriosis. ECSCs and normal endometrial stromal cells (NESCs) were isolated from ovarian endometrioma and normal endometrial tissues, respectively. We evaluated the effect of transfected hsa-miR-199a-3p on the migration, invasion, and contractility of ECSCs using Transwell migration assays, in vitro wound healing assays, Transwell invasion assays, and collagen gel contraction assays. We also examined the downstream target of hsa-miR-199a-3p with an online public database search and luciferase reporter assay. Expression of hsa-miR-199a-3p in ECSCs was significantly lower than that in NESCs, whereas the expression of p21-activated kinase 4 (PAK4) mRNA was significantly higher. Transfection of hsa-miR-199a-3p inhibited the migration, invasion, and contractility of ECSCs via inhibition of PAK4 mRNA expression. PAK4 was confirmed to be the direct target of hsa-miR-199a-3p. Transfection of PAK4 small interfering RNA and the PAK4 inhibitor PF-3758309 also inhibited ECSC migration, invasion, and contractility. These findings suggest that hsa-miR-199a-3p may act as a tumor suppressor in endometriosis development. Attenuation of hsa-miR-199a-3p expression was favorable for ECSCs to acquire the highly invasive, motile, and contractile characteristics of endometriotic cells and is involved in the development of endometriosis. Accordingly, PAK4 inhibitors may be promising for the treatment of endometriosis.

miR-425 regulates ovarian cancer proliferation, metastasis, and apoptosis by repressing PAK4 expression

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.

High ARHGEF2 (GEF-H1) Expression is Associated with Poor Prognosis Via Cell Cycle Regulation in Patients with Pancreatic Cancer

BACKGROUND

Pancreatic cancer has an extremely poor prognosis, even after curative resection. Treatment options for pancreatic cancer remain limited, therefore new therapeutic targets are urgently needed. We searched for genes predictive of poor prognosis in pancreatic cancer using a public database and validated the survival impact of the selected gene in a patient cohort.

METHODS

We used a public database to search for genes associated with early pancreatic cancer recurrence. As a validation cohort, 201 patients who underwent radical resection in our institution were enrolled. Expression of the target gene was evaluated using immunohistochemistry (IHC). We evaluated growth and invasiveness using small interfering RNAs, then performed pathway analysis using gene set enrichment analysis.

RESULTS

We extracted ARHGEF2 from GSE21501 as a gene with a high hazard ratio (HR) for early recurrence within 1 year. The high ARHGEF2 expression group had significantly poorer recurrence-free survival (RFS) and poorer overall survival (OS) than the low ARHGEF2 expression group. Multivariate analysis demonstrated that high ARHGEF2 expression was an independent poor prognostic factor for RFS (HR 1.92) and OS (HR 1.63). In vitro, ARHGEF2 suppression resulted in reduced cell growth and invasiveness. Bioinformatic analysis revealed that ARHGEF2 expression was associated with MYC, G2M, E2F, and CDC25A expression, suggesting that c-Myc and cell cycle genes are associated with high ARHGEF2 expression. IHC revealed a positive correlation between ARHGEF2 and c-Myc expression.

CONCLUSIONS

High ARHGEF2 expression is associated with cell cycle progression, and predicts early recurrence and poor survival in patients with pancreatic cancer.

Targeting PAK4 Inhibits Ras-Mediated Signaling and Multiple Oncogenic Pathways in High-Risk Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most prevalent pediatric soft-tissue sarcoma. Multimodal treatment, including surgery and traditional chemotherapy with radiotherapy, has contributed to improvements in overall survival rates. However, patients with recurrent or metastatic disease have 5-year survival rates of less than 30%. One reason for the lack of therapeutic advancement is identification and targeting of critical signaling nodes. p21-activated kinases (PAK) are a family of serine/threonine kinases downstream of multiple critical tumorigenic receptor tyrosine kinase receptors and oncogenic regulators, including IGFR and RAS signaling, that significantly contribute to aggressive malignant phenotypes. Here, we report that RMS cell lines and tumors exhibit enhanced PAK4 expression levels and activity, which are further activated by growth factors involved in RMS development. Molecular perturbation of PAK4 in multiple RMS models in vitro and in vivo resulted in inhibition of RMS development and progression. Fusion-positive and -negative RMS models were sensitive to two PAK4 small-molecule inhibitors, PF-3758309 and KPT-9274, which elicited significant antitumor and antimetastatic potential in several primary and metastatic in vivo models, including a relapsed RMS patient-derived xenograft model. Transcriptomic analysis of PAK4-targeted tumors revealed inhibition of the RAS-GTPase, Hedgehog, and Notch pathways, along with evidence of activation of antitumor immune response signatures. This PAK4-targeting gene signature showed prognostic significance for patients with sarcoma. Overall, our results show for the first time that PAK4 is a novel and viable therapeutic target for the treatment of high-risk RMS. SIGNIFICANCE: These data demonstrate a novel oncogenic role for PAK4 in rhabdomyosarcoma and show that targeting PAK4 activity is a promising viable therapeutic option for advanced rhabdomyosarcoma.

Data mining of human plasma proteins generates a multitude of highly predictive aging clocks that reflect different aspects of aging

We previously identified 529 proteins that had been reported by multiple different studies to change their expression level with age in human plasma. In the present study, we measured the q-value and age coefficient of these proteins in a plasma proteomic dataset derived from 4263 individuals. A bioinformatics enrichment analysis of proteins that significantly trend toward increased expression with age strongly implicated diverse inflammatory processes. A literature search revealed that at least 64 of these 529 proteins are capable of regulating life span in an animal model. Nine of these proteins (AKT2, GDF11, GDF15, GHR, NAMPT, PAPPA, PLAU, PTEN, and SHC1) significantly extend life span when manipulated in mice or fish. By performing machine-learning modeling in a plasma proteomic dataset derived from 3301 individuals, we discover an ultra-predictive aging clock comprised of 491 protein entries. The Pearson correlation for this clock was 0.98 in the learning set and 0.96 in the test set while the median absolute error was 1.84 years in the learning set and 2.44 years in the test set. Using this clock, we demonstrate that aerobic-exercised trained individuals have a younger predicted age than physically sedentary subjects. By testing clocks associated with 1565 different Reactome pathways, we also show that proteins associated with signal transduction or the immune system are especially capable of predicting human age. We additionally generate a multitude of age predictors that reflect different aspects of aging. For example, a clock comprised of proteins that regulate life span in animal models accurately predicts age.

PAK4 methylation by the methyltransferase SETD6 attenuates cell adhesion

P21-activated kinase 4 (PAK4), a member of serine/threonine kinases family is over-expressed in numerous cancer tumors and is associated with oncogenic cell proliferation, migration and invasion. Our recent work demonstrated that the SET-domain containing protein 6 (SETD6) interacts with and methylates PAK4 at chromatin in mammalian cells, leading to activation of the Wnt/β-catenin signaling pathway. In our current work, we identified lysine 473 (K473) on PAK4 as the primary methylation site by SETD6. Methylation of PAK4 at K473 activates β-catenin transcriptional activity and inhibits cell adhesion. Specific methylation of PAK4 at K473 also attenuates paxillin localization to focal adhesions leading to overall reduction in adhesion-related features, such as filopodia and actin structures. The altered adhesion of the PAK4 wild-type cells is accompanied with a decrease in the migrative and invasive characteristics of the cells. Taken together, our results suggest that methylation of PAK4 at K473 plays a vital role in the regulation of cell adhesion and migration.

Elevating EGFR-MAPK program by a nonconventional Cdc42 enhances intestinal epithelial survival and regeneration

The regulatory mechanisms enabling the intestinal epithelium to maintain a high degree of regenerative capacity during mucosal injury remain unclear. Ex vivo survival and clonogenicity of intestinal stem cells (ISCs) strictly required growth response mediated by cell division control 42 (Cdc42) and Cdc42-deficient enteroids to undergo rapid apoptosis. Mechanistically, Cdc42 engaging with EGFR was required for EGF-stimulated, receptor-mediated endocytosis and sufficient to promote MAPK signaling. Proteomics and kinase analysis revealed that a physiologically, but nonconventionally, spliced Cdc42 variant 2 (V2) exhibited stronger MAPK-activating capability. Human CDC42-V2 is transcriptionally elevated in some colon tumor tissues. Accordingly, mice engineered to overexpress Cdc42-V2 in intestinal epithelium showed elevated MAPK signaling, enhanced regeneration, and reduced mucosal damage in response to irradiation. Overproducing Cdc42-V2 specifically in mouse ISCs enhanced intestinal regeneration following injury. Thus, the intrinsic Cdc42-MAPK program is required for intestinal epithelial regeneration, and elevating this signaling cascade is capable of initiating protection from genotoxic injury.

The REGγ inhibitor NIP30 increases sensitivity to chemotherapy in p53-deficient tumor cells

A major challenge in chemotherapy is chemotherapy resistance in cells lacking p53. Here we demonstrate that NIP30, an inhibitor of the oncogenic REGγ-proteasome, attenuates cancer cell growth and sensitizes p53-compromised cells to chemotherapeutic agents. NIP30 acts by binding to REGγ via an evolutionarily-conserved serine-rich domain with 4-serine phosphorylation. We find the cyclin-dependent phosphatase CDC25A is a key regulator for NIP30 phosphorylation and modulation of REGγ activity during the cell cycle or after DNA damage. We validate CDC25A-NIP30-REGγ mediated regulation of the REGγ target protein p21 in vivo using p53-/- and p53/REGγ double-deficient mice. Moreover, Phosphor-NIP30 mimetics significantly increase the growth inhibitory effect of chemotherapeutic agents in vitro and in vivo. Given that NIP30 is frequently mutated in the TCGA cancer database, our results provide insight into the regulatory pathway controlling the REGγ-proteasome in carcinogenesis and offer a novel approach to drug-resistant cancer therapy.

Pancreatic neuroendocrine tumors: Therapeutic challenges and research limitations

Pancreatic neuroendocrine tumors (PNETs) are known to be the second most common epithelial malignancy of the pancreas. PNETs can be listed among the slowest growing as well as the fastest growing human cancers. The prevalence of PNETs is deceptively low; however, its incidence has significantly increased over the past decades. According to the American Cancer Society's estimate, about 4032 (> 7% of all pancreatic malignancies) individuals will be diagnosed with PNETs in 2020. PNETs often cause severe morbidity due to excessive secretion of hormones (such as serotonin) and/or overall tumor mass. Patients can live for many years (except for those patients with poorly differentiated G3 neuroendocrine tumors); thus, the prevalence of the tumors that is the number of patients actually dealing with the disease at any given time is fairly high because the survival is much longer than pancreatic ductal adenocarcinoma. Due to significant heterogeneity, the management of PNETs is very complex and remains an unmet clinical challenge. In terms of research studies, modest improvements have been made over the past decades in the identification of potential oncogenic drivers in order to enhance the quality of life and increase survival for this growing population of patients. Unfortunately, the majority of systematic therapies approved for the management of advanced stage PNETs lack objective response or at most result in modest benefits in survival. In this review, we aim to discuss the broad challenges associated with the management and the study of PNETs.

Multifaceted p21 in carcinogenesis, stemness of tumor and tumor therapy

Cancer cells possess metabolic properties that are different from those of benign cells. p21, encoded by CDKN1A gene, also named p21^Cip1/WAF1, was first identified as a cyclin-dependent kinase regulator that suppresses cell cycle G1/S phase and retinoblastoma protein phosphorylation. CDKN1A (p21) acts as the downstream target gene of TP53 (p53), and its expression is induced by wild-type p53 and it is not associated with mutant p53. p21 has been characterized as a vital regulator that involves multiple cell functions, including G1/S cell cycle progression, cell growth, DNA damage, and cell stemness. In 1994, p21 was found as a tumor suppressor in brain, lung and colon cancer by targeting p53 and was associated with tumorigenesis and metastasis. Notably, p21 plays a significant role in tumor development through p53-dependent and p53-independent pathways. In addition, expression of p21 is closely related to the resting state or terminal differentiation of cells. p21 is also associated with cancer stem cells and acts as a biomarker for such cells. In cancer therapy, given the importance of p21 in regulating the G1/S and G2 check points, it is not surprising that p21 is implicated in response to many cancer treatments and p21 promotes the effect of oncolytic virotherapy.

LINC01224 Exhibits Cancer-Promoting Activity in Epithelial Ovarian Cancer Through microRNA-485-5p-Mediated PAK4 Upregulation

Purpose

Long intergenic non-protein coding RNA 1224 (LINC01224) plays vital roles in the tumorigenesis and progression of hepatocellular carcinoma. Here, we determined LINC01224 expression in epithelial ovarian cancer (EOC) tissues and cells. We also assessed the effects of LINC01224 knockdown on the malignant phenotype of EOC cells both in vitro and in vivo. Furthermore, the detailed molecular mechanisms underlying the oncogenic actions of LINC01224 in EOC cells were elucidated.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect LINC01224 expression in EOC tissues and cells. EOC cells were transfected with small interfering RNAs, and cell proliferation, apoptosis, migration, and invasion were assessed using Cell Counting Kit-8 assay, flow cytometry, cell migration assays, and cell invasion assays, respectively. Using tumor xenografts, the effects of LINC01224 silencing on EOC tumor growth were analyzed in vivo. The mechanism underlying LINC01224 regulation of malignant processes in EOC cells was explored using bioinformatics, RNA immunoprecipitation assay, qRT-PCR, Western blotting, and rescue experiments.

Results

LINC01224 expression was upregulated in EOC tissues and cells. LINC01224 upregulation was correlated to tumor size, the International Federation of Gynecology and Obstetrics stage, and lymph node metastasis. LINC01224 depletion in EOC cells suppressed cell proliferation, migration, and invasion and facilitated cell apoptosis in vitro. LINC01224 downregulation also hindered EOC tumor growth in vivo. Mechanistically, LINC01224 served as a competing endogenous RNA for microRNA-485-5p (miR-485-5p) and consequently increased p21-activated kinase 4 (PAK4) expression in EOC cells. Furthermore, miR-485-5p inhibition or PAK4 upregulation significantly abrogated the effects of LINC01224 depletion in EOC cells.

Conclusion

LINC01224/miR-485-5p/PAK4 formed a competing endogenous RNA network regulating the aggressive behavior of EOC. Therefore, targeting this pathway may be an attractive therapeutic strategy for EOC.

PAK4 phosphorylating RUNX1 promotes ERα-positive breast cancer-induced osteolytic bone destruction

The biological function of nuclear PAK4 in ERα-positive breast cancer osteolytic bone destruction remains unclear. Here, we find that the nuclear PAK4 promotes osteoclastogenesis and tumor-induced osteolysis via phosphorylating RUNX1. We show that nuclear PAK4 interacts with and phosphorylates RUNX1 at Thr-207, which induces its localization from the nucleus to the cytoplasm and influences direct interaction with SIN3A/HDAC1 and PRMT1. Furthermore, we reveal that RUNX1 phosphorylation by PAK4 at Thr-207 promotes osteolytic bone destruction via targeting downstream genes related to osteoclast differentiation and maturation. Importantly, we verify changes in RUNX1 subcellular localization when nuclear PAK4 is positive in breast cancer bone metastasis tissues. Functionally, we demonstrate that RUNX1 phosphorylation promotes osteolytic bone maturation and ERα-positive breast cancer-induced osteolytic bone damage in the mouse model of orthotopic breast cancer bone metastasis. Our results suggest PAK4 can be a therapeutic target for ERα-positive breast cancer osteolytic bone destruction.

PDK1 promotes ovarian cancer metastasis by modulating tumor-mesothelial adhesion, invasion, and angiogenesis via α5β1 integrin and JNK/IL-8 signaling

Ovarian cancer is the most lethal gynecological malignancies owing to the lack of definitive symptoms until development of widespread metastases. Identification of novel prognostic and therapeutic targets is therefore an urgent need to improve survival. Here, we demonstrated high expression of the mitochondrial gatekeeping enzyme, pyruvate dehydrogenase kinase 1 (PDK1), in both clinical samples and cell lines of ovarian cancer. PDK1 expression was significantly associated with metastasis, reduced chemosensitivity, and poor overall and disease-free survival, and further highlighted as an independent prognostic factor. Silencing of PDK1 retarded lactate production, ovarian cancer cell adhesion, migration, invasion, and angiogenesis, and consequently metastasis, concomitant with decreased α5β1 integrin expression. Phospho-kinase array profiling and RNA sequencing analyses further revealed reduction of JNK activation and IL-8 expression in PDK1-depleted cells. Conversely, PDK1 overexpression promoted cell adhesion via modulation of α5β1 integrins, along with cell migration, invasion, and angiogenesis through activation of JNK/IL-8 signaling. PDK1 depletion additionally hindered tumor growth and dissemination in nude mice in vivo. Importantly, PDK1 levels were upregulated upon treatment with conditioned medium from omental tissues, which in turn promoted metastasis. Our findings suggest that PDK1, which is regulated by the tumor microenvironment, controls lactate production and promotes ovarian cancer cell metastasis via modulation of α5β1 integrin and JNK/IL-8 signaling. To our knowledge, this is the first report to demonstrate an association between PDK1 and survival in patients with ovarian cancer, supporting its efficacy as a valuable prognostic marker and therapeutic molecular target for the disease.

PAK4, a target of miR-9-5p, promotes cell proliferation and inhibits apoptosis in colorectal cancer

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.

Off-target toxicity is a common mechanism of action of cancer drugs undergoing clinical trials

Ninety-seven percent of drug-indication pairs that are tested in clinical trials in oncology never advance to receive U.S. Food and Drug Administration approval. While lack of efficacy and dose-limiting toxicities are the most common causes of trial failure, the reason(s) why so many new drugs encounter these problems is not well understood. Using CRISPR-Cas9 mutagenesis, we investigated a set of cancer drugs and drug targets in various stages of clinical testing. We show that-contrary to previous reports obtained predominantly with RNA interference and small-molecule inhibitors-the proteins ostensibly targeted by these drugs are nonessential for cancer cell proliferation. Moreover, the efficacy of each drug that we tested was unaffected by the loss of its putative target, indicating that these compounds kill cells via off-target effects. By applying a genetic target-deconvolution strategy, we found that the mischaracterized anticancer agent OTS964 is actually a potent inhibitor of the cyclin-dependent kinase CDK11 and that multiple cancer types are addicted to CDK11 expression. We suggest that stringent genetic validation of the mechanism of action of cancer drugs in the preclinical setting may decrease the number of therapies tested in human patients that fail to provide any clinical benefit.

Nonconserved miR-608 suppresses prostate cancer progression through RAC2/PAK4/LIMK1 and BCL2L1/caspase-3 pathways by targeting the 3'-UTRs of RAC2/BCL2L1 and the coding region of PAK4

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.

Hexokinase 2 Regulates Ovarian Cancer Cell Migration, Invasion and Stemness via FAK/ERK1/2/MMP9/NANOG/SOX9 Signaling Cascades

Metabolic reprogramming is a common phenomenon in cancers. Thus, glycolytic enzymes could be exploited to selectively target cancer cells in cancer therapy. Hexokinase 2 (HK2) converts glucose to glucose-6-phosphate, the first committed step in glucose metabolism. Here, we demonstrated that HK2 was overexpressed in ovarian cancer and displayed significantly higher expression in ascites and metastatic foci. HK2 expression was significantly associated with advanced stage and high-grade cancers, and was an independent prognostic factor. Functionally, knockdown of HK2 in ovarian cancer cell lines and ascites-derived tumor cells hindered lactate production, cell migration and invasion, and cell stemness properties, along with reduced FAK/ERK1/2 activation and metastasis- and stemness-related genes. 2-DG, a glycolysis inhibitor, retarded cell migration and invasion and reduced stemness properties. Inversely, overexpression of HK2 promoted cell migration and invasion through the FAK/ERK1/2/MMP9 pathway, and enhanced stemness properties via the FAK/ERK1/2/NANOG/SOX9 cascade. HK2 abrogation impeded in vivo tumor growth and dissemination. Notably, ovarian cancer-associated fibroblast-derived IL-6 contributed to its up-regulation. In conclusion, HK2, which is regulated by the tumor microenvironment, controls lactate production and contributes to ovarian cancer metastasis and stemness regulation via FAK/ERK1/2 signaling pathway-mediated MMP9/NANOG/SOX9 expression. HK2 could be a potential prognostic marker and therapeutic target for ovarian cancer.

INKA2, a novel p53 target that interacts with the serine/threonine kinase PAK4

The p53 protein is a tumour suppressor and transcription factor that regulates the expression of target genes involved in numerous stress responses systems. In this study, we designed a screening strategy using DNA damage-induced mouse and human transcriptome data to identify novel downstream targets of p53. Our method selected genes with an induced expression in multiple organs of X-ray-irradiated p53 wild-type mice. The expression of inka box actin regulator 2 gene, known as Inka2, was upregulated in 12 organs when p53 expression was induced. Similarly, INKA2 was induced in a p53-dependent manner at both the mRNA and protein level in human cells treated with adriamycin. Reporter assays confirmed that p53 directly regulated INKA2 through an intronic binding site. The overexpression of INKA2 produced a slight decrease in cancer cell growth in the colony formation assay. Moreover, the analysis of The Cancer Genome Atlas (TCGA) data revealed a decreased INKA2 expression in tumour samples carrying p53 mutations compared with p53 wild-type samples. In addition, significantly higher levels of DNA methylation were observed in the INKA2 promoter in tumour samples, concordant with the reduced INKA2 expression in tumour tissues. These results demonstrate the potential of INKA2 as a cancer cell growth inhibitor. Furthermore, INKA2 protein interacts with the serine/threonine-protein kinase, p21 (RAC1) activated kinase (PAK)4, which phosphorylates β-catenin to prevent ubiquitin-proteasomal degradation. As β-catenin was downregulated in a stable INKA2-expressing cell line, the findings of this study suggest that INKA2 is a novel, direct downstream target of p53 that potentially decreases cell growth by inhibiting the PAK4-β-catenin pathway.

Mbt/PAK4 together with SRC modulates N-Cadherin adherens junctions in the developing Drosophila eye

Tissue morphogenesis is accompanied by changes of adherens junctions (AJ). During Drosophila eye development, AJ reorganization includes the formation of isolated N-Cadherin AJ between photoreceptors R3/R4. Little is known about how these N-Cadherin AJ are established and maintained. This study focuses on the kinases Mbt/PAK4 and SRC, both known to alter E-Cadherin AJ across phyla. Drosophila p21-activated kinase Mbt and the non-receptor tyrosine kinases Src64 and Src42 regulate proper N-Cadherin AJ. N-Cadherin AJ elongation depends on SRC kinase activity. Cell culture experiments demonstrate binding of both Drosophila SRC isoforms to N-Cadherin and its subsequent tyrosine phosphorylation. In contrast, Mbt stabilizes but does not bind N-Cadherin in vitro. Mbt is required in R3/R4 for zipping the N-Cadherin AJ between these cells, independent of its kinase activity and Cdc42-binding. The mbt phenotype can be reverted by mutations in Src64 and Src42. Because Mbt neither directly binds to SRC proteins nor has a reproducible influence on their kinase activity, the conclusion is that Mbt and SRC signaling converge on N-Cadherin. N-Cadherin AJ formation during eye development requires a proper balance between the promoting effects of Mbt and the inhibiting influences of SRC kinases.

Summary: N-Cadherin adherens junction formation in the Drosophila larval eye imaginal disc is controlled by the combined functions of the p21-activated kinase Mbt/PAK4 and the kinases Src64 and Src42.

A novel PAK4-CEBPB-CLDN4 axis involving in breast cancer cell migration and invasion

Claudin-4 (CLDN4), a crucial member of tight junction proteins, is aberrantly expressed in breast cancer cells and contributes to cell migration and invasion. However, the mechanisms controlling CLDN4 expression in breast cancer are poorly understood. Here, we reported that CLDN4 expression correlated positively with p21-activated kinase 4 (PAK4) expression in human breast cancer tissues. Knockdown of PAK4 in MDA-MB-231 and ZR-75-30 cells suppressed CLDN4 expression and significantly inhibited cell migration and invasion. Conversely, restoration of CLDN4 expression in PAK4-knockdown cells reversed the inhibition of migration and invasion. We identified CCAAT/enhancer-binding protein β (CEBPB) as a novel transcriptional regulator of CLDN4 and confirmed that CEBPB bound to the -1093 to -991 bp region of the CLDN4 promoter. Importantly, we found that PAK4 enhanced CEBPB phosphorylation on Thr-235. In summary, we showed that PAK4-mediated CEBPB activation upregulated CLDN4 expression to promote breast cancer cell migration and invasion. Our results might contribute to understanding the mechanisms of CLDN4 regulation and suggest PAK4-CEBPB-CLDN4 axis as a potential therapeutic target for breast cancer.

Development and validation of an immune gene-set based Prognostic signature in ovarian cancer

BACKGROUND

Ovarian cancer (OV) is the most lethal gynecological cancer in women. We aim to develop a generalized, individualized immune prognostic signature that can stratify and predict overall survival for ovarian cancer.

METHODS

The gene expression profiles of ovarian cancer tumor tissue samples were collected from 17 public cohorts, including 2777 cases totally. Single sample gene set enrichment (ssGSEA) analysis was used for the immune genes from ImmPort database to develop an immune-based prognostic score for OV (IPSOV). The signature was trained and validated in six independent datasets (n = 519, 409, 606, 634, 415, 194).

FINDINGS

The IPSOV significantly stratified patients into low- and high-immune risk groups in the training set and in the 5 validation sets (HR range: 1.71 [95%CI: 1.32-2.19; P = 4.04 × 10-5] to 2.86 [95%CI: 1.72-4.74; P = 4.89 × 10-5]). Further, we compared IPSOV with nine reported ovarian cancer prognostic signatures as well as the clinical characteristics including stage, grade and debulking status. The IPSOV achieved the highest mean C-index (0.625) compared with the other signatures (0.516 to 0.602) and clinical characteristics (0.555 to 0.583). Further, we integrated IPSOV with stage, grade and debulking, which showed improved prognostic accuracy than clinical characteristics only.

INTERPRETATION

The proposed clinical-immune signature is a promising biomarker for estimating overall survival in ovarian cancer. Prospective studies are needed to further validate its analytical accuracy and test the clinical utility. FUND: This work was supported by National Key Research and Development Program of China, National Natural Science Foundation of China and Natural Science Foundation of the Jiangsu Higher Education Institutions of China.

Bioinformatic analysis of next‑generation sequencing data to identify dysregulated genes in fibroblasts of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal fibrotic lung disease with an increasing global burden. It is hypothesized that fibroblasts have a number of functions that may affect the development and progression of IPF. However, the present understanding of cellular and molecular mechanisms associated with fibroblasts in IPF remains limited. The present study aimed to identify the dysregulated genes in IPF fibroblasts, elucidate their functions and explore potential microRNA (miRNA)-mRNA interactions. mRNA and miRNA expression profiles were obtained from IPF fibroblasts and normal lung fibroblasts using a next-generation sequencing platform, and bioinformatic analyses were performed in a step-wise manner. A total of 42 dysregulated genes (>2 fold-change of expression) were identified, of which 5 were verified in the Gene Expression Omnibus (GEO) database analysis, including the upregulation of neurotrimin (NTM), paired box 8 (PAX8) and mesoderm development LRP chaperone, and the downregulation of ITPR interacting domain containing 2 and Inka box actin regulator 2 (INKA2). Previous data indicated that PAX8 and INKA2 serve roles in cell growth, proliferation and survival. Gene Ontology analysis indicated that the most significant function of these 42 dysregulated genes was associated with the composition and function of the extracellular matrix (ECM). A total of 60 dysregulated miRNAs were also identified, and 1,908 targets were predicted by the miRmap database. The integrated analysis of mRNA and miRNA expression data, combined with GEO verification, finally identified Homo sapiens (hsa)-miR-1254-INKA2 and hsa-miR-766-3p-INKA2 as the potential miRNA-mRNA interactions in IPF fibroblasts. In summary, the results of the present study suggest that dysregulation of PAX8, hsa-miR-1254-INKA2 and hsa-miR-766-3p-INKA2 may promote the proliferation and survival of IPF fibroblasts. In the functional analysis of the dysregulated genes, a marked association between fibroblasts and the ECM was identified. These data improve the current understanding of fibroblasts as key cells in the pathogenesis of IPF. As a screening study using bioinformatics approaches, the results of the present study require additional validation.

Effects of Xiaoyaosan on the Hippocampal Gene Expression Profile in Rats Subjected to Chronic Immobilization Stress

Objective: This study examined the effect of Xiaoyaosan and its anti-stress mechanism in rats subjected to chronic immobilization stress at the whole genome level. Methods: Rat whole genome expression chips (Illumina) were used to detect differences in hippocampal gene expression in rats from the control group (CN group), model group (M group) and Xiaoyaosan group (XYS group) that were subjected to chronic immobilization stress. The Gene Ontology terms and signaling pathways that were altered in the hippocampus gene expression profile were analyzed. The network regulating the transcription of the differentially expressed genes was also established. To verify the results from the gene chips, real-time quantitative polymerase chain reaction was used to determine the expression of the GABRA1, FADD, CRHR2, and CDK6 genes in hippocampal tissues. In situ hybridization (ISH) and immunohistochemistry were used to determine the expression of the GABRA1 and CRHR2 genes and proteins, respectively. Results: Compared with the CN group, 566 differentially expressed genes were identified in the M group. Compared with the M group, 544 differentially expressed genes were identified in the XYS group. In the M and XYS groups, multiple significantly upregulated or downregulated genes functioned in various biological processes. The cytokine receptor interaction pathway was significantly inhibited in the hippocampus of the model group. The actin cytoskeleton regulation pathway was significantly increased in the hippocampus of the XYS group. The inhibition of hippocampal cell growth was the core molecular event of network regulating the transcription of the differentially expressed genes in the model group. Promotion of the regeneration of hippocampal neurons was the core molecular event of the transcriptional regulatory network in the XYS group. The levels of the GABRA1, FADD, CRHR2 and CDK6 mRNAs, and proteins were basically consistent with the results obtained from the gene chip. Conclusion: XYS may have the ability of resistance to stress, enhancement immunity and promotion nerve cell regeneration by regulating the expression of multiple genes in numerous pathways and repaired the stress-induced impairments in hippocampal structure and function by inducing cytoskeletal reorganization. These results may provide the possible target spots in the treatment of stress in rats with XYS.

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.

A random forest classifier predicts recurrence risk in patients with ovarian cancer

Ovarian cancer (OC) is associated with a poor prognosis due to difficulties in early detection. The aims of the present study were to construct a recurrence risk prediction model and to reveal important OC genes or pathways. RNA sequencing data was obtained for 307 OC samples, and the corresponding clinical data were downloaded from The Cancer Genome Atlas database. Additionally, two validation datasets, GSE44104 (20 recurrent and 40 non-recurrent OC samples) and GSE49997 (204 OC samples), were obtained from the Gene Expression Omnibus database. Differentially expressed genes were screened using the differential expression via distance synthesis algorithm, followed by gene ontology enrichment analysis and weighted gene coexpression network analysis (WGCNA). Furthermore, subnetwork analysis was conducted for the protein-protein interaction (PPI) network using the BioNet package. Finally, a random forest classifier was constructed based on the subnetwork nodes, and its reliability was validated using the GSE44104 and GSE49997 validation datasets. A total of 44 upregulated and 117 downregulated genes were identified in the recurrent samples. Enrichment analysis indicated that cytochrome P450 family 17 subfamily A member 1 (CYP17A1) was associated with ‘positive regulation of steroid hormone biosynthetic processes’. WGCNA identified turquoise and grey modules that were significantly correlated with status and prognosis. A significant PPI subnetwork containing 16 nodes was also identified, including: Transcription factor GATA-4; fibroblast growth factor 9; aromatase; 3β-hydroxysteroid dehydrogenase/δ5-4-isomerase type 2; corticosteroid 11β-dehydrogenase isozyme 1; CYP17A1; pituitary homeobox 2; left-right determination factor 1; homeobox protein ARX; estrogen receptor β; steroidogenic factor 1; forkhead box protein L2; myocardin; steroidogenic acute regulatory protein mitochondrial; vesicular inhibitory amino acid transporter; and twist-related protein 1. A random forest classifier was constructed using the subnetwork nodes as feature genes, which exhibited a 92% true positive rate when classifying recurrent and non-recurrent OC samples. The classifying efficiency of the random forest classifier was validated using the two other independent datasets. Overall, 44 upregulated and 117 downregulated genes associated with OC recurrence were identified. Furthermore, the 16 subnetwork node genes that were identified may be important molecules in OC recurrence.