P21-activated Kinase Inhibitor Research Articles

Neuronal PLPP/CIN exaggerates the immune response of hippocampal microglia to LPS challenge dependent on PAK1-NF-κB-COX-2 signaling pathway

Recently, we have reported that pyridoxal-5′-phosphate phosphatase/chronophin (PLPP/CIN) selectively dephosphorylates neurofibromin 2 (NF2, also known as merlin) at serine (S) 10 site. Since NF2 inhibits p21-activated kinase 1 (PAK1)-mediated nuclear factor-κB (NF-κB) activation, in the present study, we investigated the role of PLPP/CIN-mediated NF2 S10 dephosphorylation in lipopolysaccharide (LPS)-induced neuroinflammation and explored its related signaling pathways in the mouse hippocampus. PLPP/CIN overexpression increased NF2 S10 dephosphorylation and PAK1 S204 autophosphorylation under physiological condition, which were reversed by PLPP/CIN deletion. Following LPS injection, PLPP/CIN overexpression exacerbated microglial activation, although microglial PLPP/CIN expression was undetectable. In addition, PLPP/CIN overexpression enhanced PAK1 and NF-κB phosphorylations, and upregulated cyclooxygenase-2 (COX-2) and prostaglandin E synthase 2 (PTGES2) expressions in CA1 neurons. PLPP/CIN overexpression also augmented microglial interleukin-1β induction. PLPP/CIN ablation and 1,1′-dithiodi-2-naphthtol (IPA-3, a PAK1 inhibitor) pretreatment ameliorated these LPS-induced neuroinflammatory responses. These findings indicate that PLPP/CIN-mediated NF2 S10 dephosphorylation may facilitate PAK1-NF-κB-COX-2-PTGES2 signaling pathway in CA1 neurons, which would subsequently exaggerate immune response of microglia following LPS treatment. Therefore, our findings suggest that this PLPP/CIN-mediated neuron-microglia interaction may play an important role in the pathogenesis of inflammation-related neurological diseases.

Design, synthesis and pharmacological evaluation of 1,2,3,4-tetrahydrobenzofuro[2,3-c]pyridine derivatives as p21-activated kinase 4 inhibitors for treatment of pancreatic cancer

The p21-activated kinase 4 (PAK4), a key regulator of malignancy, is negatively correlated with immune infiltration and has become an emergent drug target of cancer therapy. Given the lack of high efficacy PAK4 inhibitors, we herein reported the identification of a novel inhibitor 13 bearing a tetrahydrobenzofuro[2,3-c]pyridine tricyclic core and possessing high potency against MIA PaCa-2 and Pan02 cell lines with IC50 values of 0.38 and 0.50 μmol/L, respectively. This compound directly binds to PAK4 in a non-ATP competitive manner. In the mouse Pan02 model, compound 13 exhibited significant tumor growth inhibition at a dose of 100 mg/kg, accompanied by reduced levels of PAK4 and its phosphorylation together with immune infiltration in mice tumor tissue. Overall, compound 13 is a novel allosteric PAK4 inhibitor with a unique tricyclic structural feature and high potency both in vitro and in vivo, thus making it worthy of further exploration.

PAK4 phosphorylates and inhibits AMPKα to control glucose uptake

Our recent studies have identified p21-activated kinase 4 (PAK4) as a key regulator of lipid catabolism in the liver and adipose tissue, but its role in glucose homeostasis in skeletal muscle remains to be explored. In this study, we find that PAK4 levels are highly upregulated in the skeletal muscles of diabetic humans and mice. Skeletal muscle-specific Pak4 ablation or administering the PAK4 inhibitor in diet-induced obese mice retains insulin sensitivity, accompanied by AMPK activation and GLUT4 upregulation. We demonstrate that PAK4 promotes insulin resistance by phosphorylating AMPKα2 at Ser491, thereby inhibiting AMPK activity. We additionally show that skeletal muscle-specific expression of a phospho-mimetic mutant AMPKα2S491D impairs glucose tolerance, while the phospho-inactive mutant AMPKα2S491A improves it. In summary, our findings suggest that targeting skeletal muscle PAK4 may offer a therapeutic avenue for type 2 diabetes.

Synergistic effect of PAK and Hippo pathway inhibitor combination in NF2-deficient Schwannoma.

Neurofibromatosis type 2 is a genetic disorder that results in the formation and progressive growth of schwannomas, ependymomas, and/or meningiomas. The NF2 gene encodes the Merlin protein, which links cell cortical elements to the actin cytoskeleton and regulates a number of key enzymes including Group I p21-activated kinases (PAKs), the Hippo-pathway kinase LATS, and mTORC. While PAK1 and PAK2 directly bind Merlin and transmit proliferation and survival signals when Merlin is mutated or absent, inhibition of Group 1 PAKs alone has not proven sufficient to completely stop the growth of NF2-deficient meningiomas or schwannomas in vivo, suggesting the need for a second pathway inhibitor. As the Hippo pathway is also activated in NF2-deficient cells, several inhibitors of the Hippo pathway have recently been developed in the form of YAP-TEAD binding inhibitors. These inhibitors prevent activation of pro-proliferation and anti-apoptotic Hippo pathway effectors. In this study, we show that PAK inhibition slows cell proliferation while TEAD inhibition promotes apoptotic cell death. Finally, we demonstrate the efficacy of PAK and TEAD inhibitor combinations in several NF2-deficient Schwannoma cell lines.

PAK4 inhibition augments anti-tumour effect by immunomodulation in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common malignant tumours, warranting novel treatments. Here, we examined the therapeutic efficacy of inhibiting p21 activated kinase 4 (PAK4) in OSCC and determined its immunomodulatory effect by focusing on the enhancement of anti-tumour effects. We examined PAK4 expression in OSCC cells and human clinical samples and analysed the proliferation and apoptosis of OSCC cells following PAK4 inhibition in vitro. We also investigated the effects of in vivo administration of a PAK4 inhibitor on immune cell distribution and T-cell immune responses in OSCC tumour-bearing mice. PAK4 was detected in all OSCC cells and OSCC tissue samples. PAK4 inhibitor reduced the proliferation of OSCC cells and induced apoptosis. PAK4 inhibitor significantly attenuated tumour growth in mouse and was associated with increased proportions of IFN-γ-producing CD8+ T-cells. Furthermore, PAK4 inhibitor increased the number of dendritic cells (DCs) and up-regulated the surface expression of various lymphocyte co-stimulatory molecules, including MHC-class I molecules, CD80, CD83, CD86, and CD40. These DCs augmented CD8+ T-cell activation upon co-culture. Our results suggest that PAK4 inhibition in OSCC can have direct anti-tumour and immunomodulatory effects, which might benefit the treatment of this malignancy.

Inhibition of P21-activated kinases 1 and 4 synergistically suppresses the growth of pancreatic cancer by stimulating anti-tumour immunity

BackgroundPancreatic ductal adenocarcinoma (PDA) is one of the most lethal types of cancer, and KRAS oncogene occurs in over 90% of cases. P21-activated kinases (PAK), containing six members (PAK1 to 6), function downstream of KRAS. PAK1 and PAK4 play important roles in carcinogenesis, but their combinational effect remains unknown. In this study, we have determined the effect of dual inhibition of PAK1 and PAK4 in PDA progression using knockout (KO) cancer cell lines.MethodsMurine wild-type (WT) and PAK1KO pancreatic cancer cell lines were isolated from PAK1+/+ and PAK1−/− KPC (LSL-KrasG12D/+; LSL-Trp53 R172H/+; Pdx-1-Cre) mice. KPC PAK4KO and KPC PAK1&4 KO cell lines were generated from KPC WT and KPC PAK1KO cell lines respectively using the CRISPR-CAS9 gene knockout technique. PAK WT and KO cell lines were used in mouse models of pancreatic tumours. Cells and tumour tissue were also used in flow cytometry and proteomic studies. A human PDA tissue microarray was stained by immunohistochemistry.ResultsDouble knock out of PAK1 and PAK4 caused complete regression of tumour in a syngeneic mouse model. PAK4KO inhibited tumour growth by stimulating a rapid increase of cytotoxic CD8+ T cell infiltration. PAK1KO synergistically with PAK4KO increased cytotoxic CD8+ T cell infiltration and stimulated a sustained infiltration of CD8+ T cells at a later phase to overcome the immune evasion in the PAK4KO tumour. The human PDA tissue microarray study showed the important role of PAK1 and PAK4 in intra-tumoral T-cell function.ConclusionOur results demonstrated that dual inhibition of PAK1 and PAK4 synergistically suppressed PDA progression by stimulating cytotoxic CD8 + T cell response.

Antagonistic actions of PAK1 and NF2/Merlin drive myelin membrane expansion in oligodendrocytes.

In the central nervous system, the formation of myelin by oligodendrocytes (OLs) relies on the switch from the polymerization of the actin cytoskeleton to its depolymerization. The molecular mechanisms that trigger this switch have yet to be elucidated. Here, we identified P21-activated kinase 1 (PAK1) as a major regulator of actin depolymerization in OLs. Our results demonstrate that PAK1 accumulates in OLs in a kinase-inhibited form, triggering actin disassembly and, consequently, myelin membrane expansion. Remarkably, proteomic analysis of PAK1 binding partners enabled the identification of NF2/Merlin as its endogenous inhibitor. Our findings indicate that Nf2 knockdown in OLs results in PAK1 activation, actin polymerization, and a reduction in OL myelin membrane expansion. This effect is rescued by treatment with a PAK1 inhibitor. We also provide evidence that the specific Pak1 loss-of-function in oligodendroglia stimulates the thickening of myelin sheaths in vivo. Overall, our data indicate that the antagonistic actions of PAK1 and NF2/Merlin on the actin cytoskeleton of the OLs are critical for proper myelin formation. These findings have broad mechanistic and therapeutic implications in demyelinating diseases and neurodevelopmental disorders.

PAK1 inhibition increases TRIM21-induced PD-L1 degradation and enhances responses to anti-PD-1 therapy in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) is a common malignancy with a 5-year survival <10 %. Immunosuppressive tumor microenvironment (TME) plays a critical role in the progression of PDA. In recent years, programmed death-ligand 1 (PD-L1)/programmed cell death protein-1 (PD-1) blockade has emerged as a potent anti-tumor immunotherapy, while is yet to achieve significant clinical benefits for PDA patients. P21-Activated kinase 1 (PAK1) is highly upregulated in PDA and has been reported to be involved in the regulation of anti-tumor immunity. This study aims to investigate the combined effect of PAK1 inhibition and anti-PD-1 therapy on PDA and the underlying mechanisms. We have shown that PAK1 expression positively correlated with PD-L1 in PDA patients, and that inhibition of PAK1 downregulated PD-L1 expression of PDA cells. More importantly, we have demonstrated that PAK1 competed with PD-L1 in binding to tripartite motif-containing protein 21 (TRIM21), a ubiquitin E3 ligase, resulting in less ubiquitination and degradation of PD-L1. Moreover, PAK1 inhibition promoted CD8+ T cells activation and infiltration. In a murine PDA model, the combination of PAK1 inhibition and anti-PD-1 therapy showed significant anti-tumor effects compared with the control or monotherapy. Our results indicated that the combination of PAK1 inhibition and anti-PD-1 therapy would be a more effective treatment for PDA patients.

Polymeric nanofiber leveraged co-delivery of anti-stromal PAK1 inhibitor and paclitaxel enhances therapeutic effects in stroma-rich 3D spheroid models

The role of tumor stroma in solid tumors has been widely recognized in cancer progression, metastasis and chemoresistance. Cancer-associated fibroblasts (CAFs) play a crucial role in matrix remodeling and promoting cancer cell stemness and resistance via reciprocal crosstalk. Residual tumor tissue after surgical removal as well as unresectable tumors face therapeutic challenges to achieve curable outcome. In this study, we propose to develop a dual delivery approach by combining p21-activated kinase 1 (PAK1) inhibitor (FRAX597) to inhibit tumor stroma and chemotherapeutic agent paclitaxel (PTX) to kill cancer cells using electrospun nanofibers. First, the role of the PAK1 pathway was established in CAF differentiation, migration and contraction using relevant in vitro models. Second, polycaprolactone polymer-based nanofibers were fabricated using a uniaxial electrospinning technique to incorporate FRAX597 and/or PTX, which showed a uniform texture and a prolonged release of both drugs for 16 days. To test nanofibers, stroma-rich 3D heterospheroid models were set up which showed high resistance to PTX nanofibers compared to stroma-free homospheroids. Interestingly, nanofibers containing PTX and FRAX597 showed strong anti-tumor effects on heterospheroids by reducing the growth and viability by > 90 % compared to either of single drug-loaded nanofibers. These effects were reflected by reduced intra-spheroidal expression levels of collagen 1 and α-smooth muscle actin (α-SMA). Overall, this study provides a new therapeutic strategy to inhibit the tumor stroma using PAK1 inhibitor and thereby enhance the efficacy of chemotherapy using nanofibers as a local delivery system for unresectable or residual tumor. Use of 3D models to evaluate nanofibers highlights these models as advanced in vitro tools to study the effect of controlled release local drug delivery systems before animal studies.

Simultaneous inhibition of PI3K and PAK in preclinical models of neurofibromatosis type 2-related schwannomatosis

Neurofibromatosis Type 2 (NF2)-related schwannomatosis is a genetic disorder that causes development of multiple types of nervous system tumors. The primary and diagnostic tumor type is bilateral vestibular schwannoma. There is no cure or drug therapy for NF2. Recommended treatments include surgical resection and radiation, both of which can leave patients with severe neurological deficits or increase the risk of future malignant tumors. Results of our previous pilot high-throughput drug screen identified phosphoinositide 3-kinase (PI3K) inhibitors as strong candidates based on loss of viability of mouse merlin-deficient Schwann cells (MD-SCs). Here we used novel human schwannoma model cells to conduct combination drug screens. We identified a class I PI3K inhibitor, pictilisib and p21 activated kinase (PAK) inhibitor, PF-3758309 as the top combination due to high synergy in cell viability assays. Both single and combination therapies significantly reduced growth of mouse MD-SCs in an orthotopic allograft mouse model. The inhibitor combination promoted cell cycle arrest and apoptosis in mouse merlin-deficient Schwann (MD-SCs) cells and cell cycle arrest in human MD-SCs. This study identifies the PI3K and PAK pathways as potential targets for combination drug treatment of NF2-related schwannomatosis.

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.

Pharmacological Inhibition of PAK1 for the Treatment of NF2-Associated Vestibular Schwannoma

Neurofibromatosis Type 2 (NF2) is an autosomal-dominant genetic disorder characterized by loss of Merlin, a tumor suppressor in Schwann cells, resulting in pathognomonic bilateral vestibular schwannoma, among other complications. Depletion of Merlin results in pathologic elevation of p21-activated kinase 1 (PAK1), which promotes tumor cell proliferation, survival, and motility. Previous studies investigating the Nf2flox/flox; PAK1-/-; Postn-Cre+ genetically engineered mouse model (GEMM) revealed that PAK1 genetic knockout in Nf2-cKO mice mitigated tumor size and preserved hearing. This study builds upon this previous work to identify efficacious therapeutic agents that target PAK1. In vitro dose response curves evaluated the efficacy of five PAK inhibitors in merlin-deficient immortalized Schwann cells (MS03). Dose response curves revealed variable IC50s among the five PAK inhibitors tested. Synergy screensrevealed synergy between PAK inhibitors NVS-PAK1-1 or BGJ-398 and selumetinib, a MEK inhibitor FDA-approved for the treatment of NF1. Colony formation assays revealed robust inhibition with NVS-PAK1-1 in combination with VS6766, a RAF/MEK inhibitor currently being evaluated in clinical trial in other cancers. Western blot analysis revealed marked decrease in downstream effectors of PAK1, including phospho-ERK1/2 in cells treated with BGJ-398, NVSPAK1-1, and PAKi plus selumetinib. Together, these findings suggest that inhibition of PAK1 and MEK pathways may be an efficacious therapeutic strategy for the treatment of NF2- associated vestibular schwannoma. Establishing reproducibility of these results in cells derived from human vestibular schwannoma is necessary to continue investigating pharmacological PAK1 and MEK inhibition. Further studies are needed to verify tolerability and therapeuticefficacy of PAK1 and MEK pharmacological inhibition in vivo.

FRAX486, a PAK inhibitor, overcomes ABCB1-mediated multidrug resistance in breast cancer cells.

The overexpression of P-glycoprotein (P-gp/ABCB1) is a leading cause of multidrug resistance (MDR). Hence, it is crucial to discover effective pharmaceuticals that counteract ABCB1-mediated multidrug resistance. FRAX486 is a p21-activated kinase (PAK) inhibitor. The objective of this study was to investigate whether FRAX486 can reverse ABCB1-mediated multidrug resistance, while also exploring its mechanism of action. The CCK8 assay demonstrated that FRAX486 significantly reversed ABCB1-mediated multidrug resistance. Furthermore, western blotting and immunofluorescence experiments revealed that FRAX486 had no impact on expression level and intracellular localization of ABCB1. Notably, FRAX486 was found to enhance intracellular drug accumulation and reduce efflux, resulting in the reversal of multidrug resistance. Docking analysis also indicated a strong affinity between FRAX486 and ABCB1. This study highlights the ability of FRAX486 to reverse ABCB1-mediated multidrug resistance and provides valuable insights for its clinical application.

PAK in Pancreatic Cancer-Associated Vasculature: Implications for Therapeutic Response.

Angiogenesis has been associated with numbers of solid tumours. Anti-angiogenesis drugs starve tumours of nutrients and oxygen but also make it difficult for a chemo reagent to distribute into a tumour, leading to aggressive tumour growth. Anti-angiogenesis drugs do not appear to improve the overall survival rate of pancreatic cancer. Vessel normalisation is merging as one of the new approaches for halting tumour progression by facilitating the tumour infiltration of immune cells and the delivery of chemo reagents. Targeting p21-activated kinases (PAKs) in cancer has been shown to inhibit cancer cell growth and improve the efficacy of chemotherapy. Inhibition of PAK enhances anti-tumour immunity and stimulates the efficacy of immune checkpoint blockades. Inhibition of PAK also improves Car-T immunotherapy by reprogramming the vascular microenvironment. This review summarizes current research on PAK's role in tumour vasculature and therapeutical response, with a focus on pancreatic cancer.

Advanced glycation end products promote intervertebral disc degeneration by transactivation of matrix metallopeptidase genes

Examine the mechanism by which advanced glycation end products (AGEs) induce intervertebral disc degeneration (IDD) in C57BL/6J mice. Matrix metallopeptidase (MMP) gene mRNA levels were assessed using RT-qPCR. Immunoprecipitation and co-immunoprecipitation were performed to identify the transcriptional complex regulating MMP expression due to AGEs. The preventive effects of inhibitors targeting this complex were tested in mice on high AGE diets. IDD and AGE accumulation were evident in mice on high-AGE diets (HAGEs), persisting across dietary shifts but absent in mice exclusively on low-AGE diets. Molecularly, HAGEs activated p21-activated kinase 1 (PAK1), prompting peroxisome proliferator-activated receptor gamma coactivator-related protein 1 (PPRC1) phosphorylation. Ubiquitin-specific protease 12 (USP12) interacted with the phosphorylated PPRC1 (pPPRC1), safeguarding it from proteasomal degradation. This pPPRC1, in collaboration with two histone acetyltransferases p300/CREB-binding protein (CBP) and a transcription factor activator protein 1(AP1), enhanced the expression of 12 MMP genes (MMP1a/1b/3/7/9/10/12/13/16/19/23/28). In vitro AGE exposure on nucleus pulposus and annulus fibrosus cells replicated this gene activation pattern, driven by the PAK1/pPPRC1-p300/CBP-AP1 pathway. The application of PAK1, p300, and AP1 inhibitors reduced pPPRC1-p300/CBP-AP1 binding to MMP promoters, diminishing their expression. These inhibitors effectively thwarted IDD in HAGE mice. Our results revealed that HAGEs instigate IDD via the PAK1/pPPRC1-p300/CBP-AP1 signaling pathway. This insight can guide therapeutic strategies to slow IDD progression in prediabetic/diabetic patients.

PAK4 inhibition significantly potentiates Gemcitabine activity in PDAC cells via inhibition of Wnt/β-catenin, p-ERK/MAPK and p-AKT/PI3K pathways

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.

Toward Ameliorating Insulin Resistance: Targeting a Novel PAK1 Signaling Pathway Required for Skeletal Muscle Mitochondrial Function.

The p21-activated kinase 1 (PAK1) is required for insulin-stimulated glucose uptake in skeletal muscle cells. However, whether PAK1 regulates skeletal muscle mitochondrial function, which is a central determinant of insulin sensitivity, is unknown. Here, the effect of modulating PAK1 levels (knockdown via siRNA, overexpression via adenoviral transduction, and/or inhibition of activation via IPA3) on mitochondrial function was assessed in normal and/or insulin-resistant rat L6.GLUT4myc and human muscle (LHCN-M2) myotubes. Human type 2 diabetes (T2D) and non-diabetic (ND) skeletal muscle samples were also used for validation of the identified signaling elements. PAK1 depletion in myotubes decreased mitochondrial copy number, respiration, altered mitochondrial structure, downregulated PGC1α (a core regulator of mitochondrial biogenesis and oxidative metabolism) and PGC1α activators, p38 mitogen-activated protein kinase (p38MAPK) and activating transcription factor 2 (ATF2). PAK1 enrichment in insulin-resistant myotubes improved mitochondrial function and rescued PGC1α expression levels. Activated PAK1 was localized to the cytoplasm, and PAK1 enrichment concurrent with p38MAPK inhibition did not increase PGC1α levels. PAK1 inhibition and enrichment also modified nuclear phosphorylated-ATF2 levels. T2D human samples showed a deficit for PGC1α, and PAK1 depletion in LHCN-M2 cells led to reduced mitochondrial respiration. Overall, the results suggest that PAK1 regulates muscle mitochondrial function upstream of the p38MAPK/ATF2/PGC1α-axis pathway.

Targeting P21-activated kinase suppresses proliferation and enhances chemosensitivity in T-cell lymphoblastic lymphoma.

T-cell lymphoblastic lymphoma (T-LBL) is a highly aggressive non-Hodgkin lymphoma with a poor prognosis. P21-activated kinase (PAK) is a component of the gene expression-based classifier that can predict the prognosis of T-LBL. However, the role of PAK in T-LBL progression and survival remains poorly understood. Herein, we found that the expression of PAK1 was significantly higher in T-LBL cell lines (Jurkat, SUP-T1, and CCRF-CEM) compared to the human T-lymphoid cell line. Moreover, PAK2 mRNA level of 32 relapsed T-LBL patients was significantly higher than that of 37 cases without relapse (P = .012). T-LBL patients with high PAK1 and PAK2 expression had significantly shorter median RFS than those with low PAK1 and PAK2 expression (PAK1, P = .028; PAK2, P = .027; PAK1/2, P = .032). PAK inhibitors, PF3758309 (PF) and FRAX597, could suppress the proliferation of T-LBL cells by blocking the G1/S cell cycle phase transition. Besides, PF could enhance the chemosensitivity to doxorubicin in vitro and in vivo. Mechanistically, through western blotting and RNA sequencing, we identified that PF could inhibit the phosphorylation of PAK1/2 and downregulate the expression of cyclin D1, NF-κB and cell adhesion signaling pathways in T-LBL cell lines. These findings suggest that PAK might be associated with T-LBL recurrence and further found that PAK inhibitors could suppress proliferation and enhance chemosensitivity of T-LBL cells treated with doxorubicin. Collectively, our present study underscores the potential therapeutic effect of inhibiting PAK in T-LBL therapy.

Perspectives on the Role of P21-Activated Kinase 1 (PAK1) in the Intestinal Anti-inflammatory and Antitumor Potential of Artepillin C.

The Brazilian biodiversity may bring new perspectives to the therapy of Inflammatory Bowel Diseases (IBD) and intestinal cancer. The effect of Brazilian Green Propolis in reducing ulcerative colitis in mice has already been described, as well as high amounts of the prenylated compound Artepellin C (ARC). The search for new pharmacological targets for IBD is also advancing. Among possibilities is the p21-activated kinase (PAK1), overexpressed and activated in the intestinal mucosa during IBD and colitis-associated colorectal cancer (CAC). PAK 1 contributes to tissue inflammation by reducing the expression of peroxisome proliferator-activated receptor type γ (PPAR47) and increasing activation of nuclear factor (NF)-κB. At least in vitro, inhibition of PAK1 has been reported to mitigate NF-κB-mediated inflammation in intestinal cells and ARC inhibits PAK1 activation. Given this pharmacological potential of ARC and the role of PAK1 in IBD and CAC, this perspective collected information that encourages future research to test the hypothesis that ARC can maintain intestinal integrity under the inflammatory and neoplastic stimulus and that inhibition of PAK1/NF-κB signaling and favoring PPAR-γ activity is pivotal in this action. Therefore, future studies employing in vitro and in vivo steps, using murine and human enterocytes and rodents submitted to ulcerative colitis and CAC models are incentivized by the data gathered here, favor retirar essas palavras: mostly in vitro studies, before clinical trials. Therefore, the perspective presented here points to an interesting path in the search for a drug useful in inflammatory and neoplastic intestinal diseases, which may have ARC as a prototype, acting on a target not yet explored clinically.

PAK1 contributes to cerebral ischemia/reperfusion injury by regulating the blood-brain barrier integrity

Globally, stroke is one of the leading causes of death and significant contributors to disability. Gaining a thorough comprehension of the underlying pathogenic processes is essential for stroke treatment and prevention. In this study, we investigated the role of p21-activated kinase 1 (PAK1) in stroke by using oxygen-glucose deprivation (OGD) and transient middle cerebral artery occlusion and reperfusion (tMCAO/R) models. We reported that focal ischemia and reperfusion affect the PAK1 expression and activity levels. We further demonstrated that PAK1 is responsible for the endothelial hyperpermeability that occurs in the early stages of ischemia and reperfusion. Additionally, inhibition of PAK1 was discovered to alleviate blood-brain barrier disruption and protect against brain injury induced by tMCAO/R. Mechanistically, we provide the evidence that PAK1 regulates the formation of stress fibers and expression of surface junctional proteins. Together, our findings reveal a pathogenic function of PAK1 in stroke.