Baicalein Inhibits the Growth of Transplanted Esophageal Cancer in Mice and the Effect on the Expression of PAK4.

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

Frondoside A from sea cucumber and nymphaeols from Okinawa propolis: Natural anti-cancer agents that selectively inhibit PAK1 in vitro.

A sulfated saponin called "Frondoside A" (FRA) from sea cucumber and ingredients from Okinawa propolis (OP) have been previously shown to suppress the PAK1-dependent growth of A549 lung cancer as well as pancreatic cancer cells. However, the precise molecular mechanism underlying their anti-cancer action still remains to be clarified. In this study, for the first time, we found that both FRA and OP directly inhibit PAK1 in vitro in a selective manner (far more effectively than two other oncogenic kinases, LIMK and AKT). Furthermore, at least two major anti-cancer ingredients of OP, nymphaeols A and C, also directly inhibit PAK1 in vitro in a selective manner. To the best of our knowledge, FRA is the first marine compound that selectively inhibits PAK1. Likewise, these nymphaeols are the first propolis ingredients that selectively inhibit PAK1.

Both triazolyl ester of ketorolac (15K) and YM155 inhibit the embryonic angiogenesis in ovo (fertilized eggs) via their common PAK1-survivin/VEGF signaling pathway.

15 K is 1,2, 3-triazolyl ester of ketorolac, an old pain-killer, that blocks PAK1 by its R-form and inhibits COX-2 by its S-form. Mainly due to a robust increase in cell-permeability, 15K is over 500 times more potent than ketorolac in both anti-cancer and anti-PAK1 activities in cell culture with IC50 around 24 nM. However, 15K has no anti-AKT activity. Angiogenesis requires at least the kinase PAK1, and perhaps the kinase AKT as well, and is essential for a robust growth of solid tumors. Thus, in this study, we examined the potential antiangiogenic activity of 15K both in ovo and cell culture, prior to its in vivo (xenograft) anti-cancer activity test. The IC50 of 15K against the embryonic angiogenesis in ovo in CAM (chorioallantoic membrane) assay is around 1 nmol/egg. Surprizingly, however, 15K failed to inhibit the tube formation of HUVECs (human umbilical vein endothelial cells) in cell culture even at high as 150 µM. In an attempt to solve this mystery, we tested both in ovo as well as HUVECs-based anti-angiogenic activity of a potent survivin-suppressor called YM155, which blocks PAK1, in addition to AKT. YM155 is slightly more potent than 15K in CAM assay with IC50 around 0.5 nmol/egg, and apparenty inhibits the tube formation of HUVECs with IC50 around 18 nM. According to a few previous findings with the direct PAK1-inhibitor frondoside A (FRA), the tube formation of HUVECs depends solely on PAK1. Thus, the failure of 15K to affect their tube formation is most likely due to their drug (15K)-resistance. Furthermore, unlike FRA, YM155 killed HUVECs with IC50 around 18 nM, clearly indicating that AKT is essential for survival of HUVECs, instead of their tube formation.

Liposome-mediated delivery of the p21 activated kinase-1 (PAK-1) inhibitor IPA-3 limits prostate tumor growth in vivo.

P21 activated kinases-1 (PAK-1) is implicated in various diseases. It is inhibited by the small molecule 'inhibitor targeting PAK1 activation-3' (IPA-3), which is highly specific but metabolically unstable. To address this limitation we encapsulated IPA-3 in sterically stabilized liposomes (SSL). SSL-IPA-3 averaged 139nm in diameter, polydispersity index (PDI) of 0.05, and a zeta potential of -28.1, neither of which changed over 14days; however, the PDI increased to 0.139. Analysis of liposomal IPA-3 levels demonstrated good stability, with 70% of IPA-3 remaining after 7days. SSL-IPA-3 inhibited prostate cancer cell growth in vitro with comparable efficacy to free IPA-3. Excitingly, only a 2day/week dose of SSL-IPA-3 was needed to inhibit the growth of prostate xenografts in vivo, while a similar dose of free IPA-3 was ineffective. These data demonstrate the development and clinical utility of a novel liposomal formulation for the treatment of prostate cancer.

MiR-224 promotes proliferation and migration of gastric cancer cells through targeting PAK4.

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

Effect of omega-3 polyunsaturated fatty acids on the cytoskeleton: an open-label intervention study.

BACKGROUND: Omega-3 polyunsaturated fatty acids (n-3 PUFAs) show beneficial effects on cardiovascular health and cognitive functions, but the underlying molecular mechanisms are not completely understood. Because of the fact that cytoskeleton dynamics affect almost every cellular process, the regulation of cytoskeletal dynamics could be a new pathway by which n-3 PUFAs exert their effects on cellular level. METHODS: A 12-week open-label intervention study with 12 healthy men was conducted to determine the effects of 2.7 g/d n-3 PUFA on changes in mRNA expression of cytoskeleton-associated genes by quantitative real-time PCR in whole blood. Furthermore, the actin content in red blood cells was analyzed by immunofluorescence imaging. RESULTS: N-3 PUFA supplementation resulted in a significant down-regulation of cytoskeleton-associated genes, in particular three GTPases (RAC1, RHOA, CDC42), three kinases (ROCK1, PAK2, LIMK), two Wiskott-Aldrich syndrome proteins (WASL, WASF2) as well as actin related protein 2/3 complex (ARPC2, ARPC3) and cofilin (CFL1). Variability in F-actin content between subjects was high; reduced actin content was only reduced within group evaluation. CONCLUSIONS: Reduced cytoskeleton-associated gene expression after n-3 PUFA supplementation suggests that regulation of cytoskeleton dynamics might be an additional way by which n-3 PUFAs exert their cellular effects. Concerning F-actin, this analysis did not reveal unmistakable results impeding a generalized conclusion.

P21-activated kinase 1 (PAK1) as a therapeutic target in BRAF wild-type melanoma.

BACKGROUND: Although remarkable clinical response rates in melanoma have been observed using vemurafenib or dabrafenib in patients with tumors carrying oncogenic mutations in BRAF, a substantial unmet medical need remains for the subset of patients with wild-type BRAF tumors. METHODS: To investigate the role of p21-activated kinases (PAKs) in melanoma, we determined PAK1 genomic copy number and protein expression for a panel of human melanoma tissues. PAK1 was inhibited in vitro and in vivo using RNA interference or PF-3758309 inhibitor treatment in a panel of melanoma cell lines with known BRAF and RAS (rat sarcoma) genotype to better understand its role in melanoma cell proliferation and migration. Tumorigenesis was assessed in vivo in female NCR nude mice and analyzed with cubic spline regression and area under the curve analyses. All statistical tests were two-sided. RESULTS: Strong cytoplasmic PAK1 protein expression was prevalent in melanomas (27%) and negatively associated with activating mutation of the BRAF oncogene (P < .001). Focal copy number gain of PAK1 at 11q13 was also observed in 9% of melanomas (n = 87; copy number ≥ 2.5) and was mutually exclusive with BRAF mutation (P < .005). Selective PAK1 inhibition attenuated signaling through mitogen-activated protein kinase (MAPK) as well as cytoskeleton-regulating pathways to modulate the proliferation and migration of BRAF wild-type melanoma cells. Treatment of BRAF wild-type melanomas with PF-3758309 PAK inhibitor decreased tumor growth for SK-MEL23 and 537MEL xenografts (91% and 63% inhibition, respectively; P < .001) and MAPK pathway activation in vivo. CONCLUSIONS: Taken together, our results provide evidence for a functional role of PAK1 in BRAF wild-type melanoma and therapeutic use of PAK inhibitors in this indication.

Pak1 as a novel therapeutic target for antihypertrophic treatment in the heart.

BACKGROUND: Stress-induced hypertrophic remodeling is a critical pathogenetic process leading to heart failure. Although many signal transduction cascades are demonstrated as important regulators to facilitate the induction of cardiac hypertrophy, the signaling pathways for suppressing hypertrophic remodeling remain largely unexplored. In this study, we identified p21-activated kinase 1 (Pak1) as a novel signaling regulator that antagonizes cardiac hypertrophy. METHODS AND RESULTS: Hypertrophic stress applied to primary neonatal rat cardiomyocytes (NRCMs) or murine hearts caused the activation of Pak1. Analysis of NRCMs expressing constitutively active Pak1 or in which Pak1 was silenced disclosed that Pak1 played an antihypertrophic role. To investigate the in vivo role of Pak1 in the heart, we generated mice with a cardiomyocyte-specific deletion of Pak1 (Pak1(cko)). When subjected to 2 weeks of pressure overload, Pak1(cko) mice developed greater cardiac hypertrophy with attendant blunting of JNK activation compared with controls, and these knockout mice underwent the transition into heart failure when prolonged stress was applied. Chronic angiotensin II infusion also caused increased cardiac hypertrophy in Pak1(cko) mice. Moreover, we discovered that the Pak1 activator FTY720, a sphingosine-like analog, was able to prevent pressure overload-induced hypertrophy in wild-type mice without compromising their cardiac functions. Meanwhile, FTY720 failed to exert such an effect on Pak1(cko) mice, suggesting that the antihypertrophic effect of FTY720 likely acts through Pak1 activation. CONCLUSIONS: These results, for the first time, establish Pak1 as a novel antihypertrophic regulator and suggest that it may be a potential therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Isoliquiritigenin 2'-methyl ether induces growth inhibition and apoptosis in oral cancer cells via heme oxygenase-1.

We previously reported that a chloroform extract of Caesalpinia sappan L. induces apoptosis in oral cancer cells but not in normal epithelial cell lines. In the present study, we explored the effects of a single compound isolated from C. sappan heartwood, isoliquiritigenin 2'-methyl ether (ILME), on cultured primary and metastatic oral cancer cell lines using MTT assays, fluorescence microscopy, flow cytometry, and Western blotting. ILME inhibited the growth of the oral cancer cells in a time- and dose-dependent manner. The major mechanism of growth inhibition was apoptosis induction, as shown by flow cytometric analysis of sub-G(1)-phase arrest and by annexin V-FITC and propidium iodide staining. ILME time-dependently activated NF-kappaB transcription factors, phospholated the MAP kinases JNK (c-Jun N-terminal kinase) and ERK (extracellular signal-regulated kinase). Furthermore, ILME treatment upregulated HO-1 expression though activation of Nrf2 (NF-E2-related factor 2) pathway, and induced the expression of heme oxygenase-1 (HO-1). Tin protoporphyrin, an HO-1 inhibitor, dose-dependently attenuated the growth-inhibitory effect of ILME and blocked ILME-induced expression of the p21 and p53 cell cycle-regulatory proteins. These results provide the first evidence that the anti-oral cancer effects of ILME may involve a mechanism in which HO-1 is upregulated via a pathway involving MAP kinases, NF-kappaB, and Nrf2. Thus, ILME could be considered to be a potential chemotherapeutic target for anti-oral cancer treatment strategies.

Arsenic alters vascular smooth muscle cell focal adhesion complexes leading to activation of FAK-src mediated pathways.

Chronic exposure to arsenic has been linked to tumorigenesis, cardiovascular disease, hypertension, atherosclerosis, and peripheral vascular disease; however, the molecular mechanisms underlying its pathological effects remain elusive. In this study, we investigated arsenic-induced alteration of focal adhesion protein complexes in normal, primary vascular smooth muscle cells. We demonstrate that exposure to environmentally relevant concentrations of arsenic (50 ppb As(3+)) can alter focal adhesion protein co-association leading to activation of downstream pathways. Co-associated proteins were identified and quantitated via co-immunoprecipitation, SDS-PAGE, and Western blot analysis followed by scanning densitometry. Activation of MAPK pathways in total cell lysates was evaluated using phosphor-specific antibodies. In our model, arsenic treatment caused a sustained increase in FAK-src association and activation, and induced the formation of unique signaling complexes (beginning after 3-hour As(3+) exposure and continuing throughout the 12-hour time course studied). The effects of these alterations were manifested as chronic stimulation of downstream PAK, ERK and JNK pathways. Past studies have demonstrated that these pathways are involved in cellular survival, growth, proliferation, and migration in VSMCs.

Antiproliferative and survival properties of PMA in MCF-7 breast cancer cell.

Although PKCs are assumed to be the main targets of phorbol esters (PMA), additional PMA effectors, such as chimaerins (a family of RacGTPase activating proteins) and RasGRP (exchange factor for Ras/Rap1), can counteract or strengthen the PKC pathways. In this study, we evaluated the proliferative behavior of PMA-treated MCF-7 breast cancer cell and found that: PMA induced growth arrest and inhibited cell death; PMA activated ERKs, which, in turn, induced p21; and inhibitors of ERK (PD98059) and PKC (GF109203X) prevented p21 induction and abolished the PMA survival effect. We conclude that PMA inhibits MCF-7 cell growth and simultaneously stimulates cell survival; both responses are linked to ERK-dependent and p53-independent p21 induction.