Tryptophan intake and pancreatic cancer: findings from a case-control study.

BACKGROUND: Pancreatic cancer is a leading cause of cancer-related death worldwide. Tryptophan plays a vital role in cell growth and maintenance as a building block of protein and coordination of organismal responses to environmental and dietary cues. Animal model study showed that dietary tryptophan improved treatment response in those who received chemotherapy or immune checkpoint inhibitors. Limited data are available assessing the association between tryptophan intake and risk of pancreatic cancer. We aimed to evaluate this association in a case-control study in Vietnam. METHODS: We analyzed data from a case-control study, including 3759 cancer cases and 2995 control subjects of whom 37 with pancreatic cancer cases. Tryptophan intake was derived from food frequency questionnaire. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for different levels of tryptophan intake with pancreatic cancer risk. RESULTS: Overall, tryptophan intake was inversely associated with pancreatic cancer risk in a dose-dependent manner. The ORs and 95% CIs of pancreatic cancer were 0.51 (0.29-0.92) for continuous scale, 0.27 (0.10-0.73) for tertile 2 and 0.34 (0.11-1.06) for tertile 3, compared with tertile 1 (the lowest intake) (Ptrend = 0.02). In stratified analysis, this inverse association pattern was present among those with BMI < 23 kg/m2 and ever drinkers. CONCLUSION: A diet with a higher intake of tryptophan was significantly associated with a lower incidence of pancreatic cancer among Vietnamese population. These suggest that dietary modification may be an effective strategy for primary prevention of pancreatic cancer development.

Interferon-Gamma Increases the Immune Modulation of Umbilical Cord-Derived Mesenchymal Stem Cells but Decreases Their Chondrogenic Potential.

INTRODUCTION: The pro-inflammatory cytokine interferon-gamma (IFN-γ) is reported to be an agent that boosts the immune modulation of mesenchymal stem cells (MSCs). However, the effects of IFN-γ on the chondrogenic potential of treated MSCs have not been evaluated in depth. This study aimed to evaluate the effects of IFN-γ on the immune modulation and chondrogenic potential of human umbilical cord-derived MSCs (hUC-MSCs). METHODS: UC-MSCs were isolated and expanded following published protocols. They were characterized as MSCs before their use in further experiments. The UC-MSCs were treated with IFN-γ at 10 ng/mL for 48 h. Changes in phenotype were investigated based on changes in MSC markers, immunomodulatory genes (TGF-ß, IL-4, and IDO) for immune modulation, and cartilage-related genes during the induction of differentiation (Col1a2, Col2a1, Sox9, Runx2, and Acan) for chondrogenic potential. RESULTS: IFN-γ-treated UC-MSCs maintained MSC markers and exhibited decreased expression of transcriptional regulatory factors in chondrogenesis (Sox9 and Runx2) and the extracellular matrix-specific genes Col1a2 and Acan but not Col2a1 compared to non-treated cells (p < 0.05). Furthermore, the immunomodulatory capability of IFN-γ-treated UC-MSCs was clearly revealed through their increased expression of IDO and IL-4 and decreased expression of TGF-ß compared to non-treated cells (p < 0.05). CONCLUSION: This study demonstrated that UC-MSCs treated with IFN-γ at 10 ng/mL had reduced expression of chondrocyte-specific genes; however, they maintained multi-lineage differentiation and exhibited immunomodulatory properties.

CXCL5 knockdown attenuated gemcitabine resistance of pancreatic cancer through regulation of cancer cells and tumour stroma.

Chemoresistance is one of the major causes to the poor prognosis of pancreatic cancer (PC). Gemcitabine alone and gemcitabine-based therapies are mostly used for the treatment of PC. Gemcitabine resistance becomes the focus of chemotherapy. C-X-C motif chemokine 5 (CXCL5), a member of the C-X-C chemokine family, acts through C-X-C chemokine receptor type 2 (CXCR2). A high level of CXCL5 is associated with worse prognosis in PC patients and increased suppressive immune cell infiltration. Increased expression of CXCL5 is also found in gemcitabine-treated PC cells. To investigate the role of CXCL5 in PC response to gemcitabine, CXCL5 knockdown (KD) PC cells were generated and its effect on cancer cell response to gemcitabine in vitro and in vivo was studied. The mechanisms involved were also explored by determining the changes in the tumour microenvironment (TME) and protein profile of the CXCL5 KD cells using immune-staining and proteomic analysis. The results showed that CXCL5 expression were increased in all PC cell lines tested and in gemcitabine-resistant tumour tissue, that CXCL5 KD suppressed PC growth and sensitized PC cell response to gemcitabine and that CXCL5 KD stimulated the activation of stromal cells in TME. We conclude that CXCL5 promotes gemcitabine resistance by affecting TME and cancer cells.

Bromodomain and extraterminal protein-targeted probe enables tumour visualisation in vivo using positron emission tomography.

Bromodomain and extraterminal (BET) proteins, a family of epigenetic regulators, have emerged as important oncology drug targets. BET proteins have not been targeted for molecular imaging of cancer. Here, we report the development of a novel molecule radiolabelled with positron emitting fluorine-18, [18F]BiPET-2, and its in vitro and preclinical evaluation in glioblastoma models.

Vitamin D intake and gastric cancer in Viet Nam: a case-control study.

BACKGROUND: Most recent laboratory studies have suggested a promising role of vitamin D and its analogs as novel chemotherapeutic agents for cancer treatment. However, epidemiological evidence, especially regarding the effects of vitamin D on gastric cancer is still inconsistent. OBJECTIVES: Our research aimed to evaluate the associations between vitamin D intake and the risk of developing gastric cancer through a case-control study in North Vietnam. METHODS: We accessed databases of the previous completed case-control studies to derive 1182 incident gastric cancer cases and 2995 hospital controls selected from hospitals in Hanoi from 2003 to 2019. Vitamin D intake was computed by multiplying the food frequency intake with nutrient content based on the Viet Nam Food Composition Tables. Data were collected through face-to-face interviews by trained interviewers using the validated semi-quantitative food frequency and demographic lifestyle questionnaires. The odds ratio and 95% confidence interval (OR and 95%CI) were estimated using unconditional logistic regression analysis. RESULTS: We observed a continual decline in gastric cancer risk according to the level-up of vitamin D intake in both genders, men, and women [Fifth vs. bottom quintile, OR, 95%CI: 0.68 (0.53, 0.86), OR, 95%CI: 0.72 (0.53, 0.97), OR, 95%CI: 0.58 (0.38, 0.89), respectively. Per increment quintile, the statistically significant decreased risk was seen by 7% in men and 13% in women. The significant inverse association between vitamin D intake remained in the subgroups of ever and never tobacco smoking; negative and positive H. pylori infection. CONCLUSION: The findings suggested that sufficient vitamin D intake was associated with a lower risk of Gastric Cancer in the Vietnamese population.

Radiolabelling and preclinical characterization of 89Zr-Df-radiolabelled bispecific anti-PD-L1/TGF-ßRII fusion protein bintrafusp alfa.

PURPOSE: Τhis study aimed to optimize the 89Zr-radiolabelling of bintrafusp alfa investigational drug product and controls, and perform the in vitro and in vivo characterization of 89Zr-Df-bintrafusp alfa and 89Zr-Df-control radioconjugates. METHODS: Bintrafusp alfa (anti-PD-L1 human IgG1 antibody fused to TGF-ß receptor II (TGF-ßRII), avelumab (anti-PD-L1 human IgG1 control antibody), isotype control (mutated inactive anti-PD-L1 IgG1 control antibody), and trap control (mutated inactive anti-PD-L1 human IgG1 fused to active TGF-ßRII) were chelated with p-isothiocyanatobenzyl-desferrioxamine (Df). After radiolabelling with zirconium-89 (89Zr), radioconjugates were assessed for radiochemical purity, immunoreactivity, antigen binding affinity, and serum stability in vitro. In vivo biodistribution and imaging studies were performed with PET/CT to identify and quantitate 89Zr-Df-bintrafusp alfa tumour uptake in a PD-L1/TGF-ß-positive murine breast cancer model (EMT-6). Specificity of 89Zr-Df-bintrafusp alfa was assessed via a combined biodistribution and imaging experiment in the presence of competing cold bintrafusp alfa (1 mg/kg). RESULTS: Nanomolar affinities for PD-L1 were achieved with 89Zr-Df-bintrafusp alfa and 89Zr-avelumab. Biodistribution and imaging studies in PD-L1- and TGF-ß-positive EMT-6 tumour-bearing BALB/c mice demonstrated the biologic similarity of 89Zr-Df-bintrafusp alfa and 89Zr-avelumab indicating the in vivo distribution pattern of bintrafusp alfa is driven by its PD-L1 binding arm. Competition study with 1 mg of unlabelled bintrafusp alfa or avelumab co-administered with trace dose of 89Zr-labelled bintrafusp alfa demonstrated the impact of dose and specificity of PD-L1 targeting in vivo. CONCLUSION: Molecular imaging of 89Zr-Df-bintrafusp alfa biodistribution was achievable and allows non-invasive quantitation of tumour uptake of 89Zr-Df-bintrafusp alfa, suitable for use in bioimaging clinical trials in cancer patients.

Cannabinoids Inhibited Pancreatic Cancer via P-21 Activated Kinase 1 Mediated Pathway.

The anti-cancer effects of cannabinoids including CBD (Cannabidiol) and THC ((-)-trans-∆9-tetrahydrocannabinol) have been reported in the case of pancreatic cancer (PC). The connection of these cannabinoids to KRas oncogenes that mutate in more than 90% of PC, and their effects on PD-L1, a key target of immune checkpoint blockade, have not been thoroughly investigated. Using cell lines and mouse models of PC, the effects of CBD and THC on cancer growth, the interaction between PC cells and a stromal cell, namely pancreatic stellate cells (PSCs), and the mechanism(s) involved were determined by cell-based assays and mouse study in vivo. CBD and THC inhibited the proliferation of PC, PSC, and PSC-stimulated PC cells. They also suppressed pancreatic tumour growth in mice. Furthermore, CBD and/or THC reduced the expression of PD-L1 by either PC or PSC cells. Knockout of p-21 activated kinase 1 (PAK1, activated by KRas) in PC and PSC cells and, in mice, dramatically decreased or blocked these inhibitory effects of CBD and/or THC. These results indicated that CBD and THC exerted their inhibitions on PC and PSC via a p-21 activated kinase 1 (PAK1)-dependent pathway, suggesting that CBD and THC suppress Kras activated pathway by targeting PAK1. The inhibition by CBD and THC of PD-L1 expression will enhance the immune checkpoint blockade of PC.

Inhibition of PAK1 suppresses pancreatic cancer by stimulation of anti-tumour immunity through down-regulation of PD-L1.

Immunotherapies have not yielded significant clinical benefits for pancreatic ductal adenocarcinoma (PDA) because of the existence of an immunosuppressive tumour microenvironment (TME) characterized by a desmoplastic stroma containing infiltrated immune cells and activated pancreatic stellate cells (PSCs). This study aims to investigate the involvement of PAK1 in anti-tumour immunity. In PDA patients, low PAK1 expression, low activation of PSC and high CD8+ T cell/PAK1 ratios correlated with longer overall survival. In a murine PDA model, PAK1 knockout increased intra-tumoral CD4+ and CD8+ T cells, inhibited PSCs activation and extended survival. Inhibition of PAK1 reduced PSC-stimulated PDA cell proliferation and migration, blocked PSC-mediated protection of PDA cells from killing by cytotoxic lymphocytes and decreased intrinsic and PSC-stimulated PD-L1 expression in PDA cells, which further sensitized PDA cells to cytotoxic lymphocytes. Inhibition of PAK1 stimulates anti-tumour immunity by increasing intra-tumoral CD4+ and CD8+ T cells, and by sensitizing PDA cells to killing by cytotoxic lymphocytes via down-regulation of intrinsic and PSC-stimulated PD-L1 expression. PAK1 inhibitors, especially in combination with immune checkpoint inhibitors may result in improved efficacy of immunotherapy of PDA.

PAK inhibition by PF-3758309 enhanced the sensitivity of multiple chemotherapeutic reagents in patient-derived pancreatic cancer cell lines.

BACKGROUND/OBJECTIVE: Pancreatic ductal adenocarcinoma (PDA) remains the most lethal malignancy due to lack of an effective treatment. P21-activated kinases (PAKs) play a key role not only in cell proliferation and migration, but also in mediating chemo-resistance in PDA. The aim of this study was to investigate the combined effect of a PAK inhibitor PF-3758309 with multiple chemotherapeutic reagents on a panel of patient-derived PDA cell lines, and potential mechanisms involved. METHODS: Cells were treated with PF-3758309 plus or minus gemcitabine, 5-fluorouracil (5-FU) or abraxane, and cell growth was determined using a cell proliferation assay kit. Protein expression profiles were measured by Western blot. PDA cells were subcutaneously injected into the flanks of SCID mice which were then treated with saline, gemcitabine, PF-3758309, gemcitabine plus PF-3758309 or abraxane. Tumour growth was measured by volume and weight. RESULTS: PAK1 was correlated with CK19 expression, and PAK4 with α-SMA and palladin expression. Combination of PF-3758309 with 5-FU, gemcitabine or abraxane further suppressed cell growth of patient-derived PDA cell lines in vitro. The combination of PF-3758309 with gemcitabine maximally inhibited tumour growth in vivo by suppressing cell proliferation. PF-3758309 inhibited the expression of HIF-1α, palladin and α-SMA both in vitro and in vivo. CONCLUSIONS: PAK inhibitor PF-3758309 can enhance anti-tumour effects of multiple chemotherapeutic reagents on a panel of patient-derived PDA cell lines. Combination of PF-3758309 with gemcitabine achieves comparable efficacy to combination of gemcitabine with abraxane, and thus provides a potential targeted therapy in the management of PDA.

Inhibition of p21 activated kinase enhances tumour immune response and sensitizes pancreatic cancer to gemcitabine.

Pancreatic ductal adenocarcinoma (PDA) is one of the major types of cancer that exhibit high mortality worldwide because of the late diagnosis and the lack of effective treatment. Immunotherapy appears to be ineffective in PDA treatment due to the existence of a unique immune-suppressive microenvironment in PDA. Gemcitabine-based therapy is still the most commonly used chemotherapy to treat PDA patients with only marginal increased survival rates. This prompted us to continue the search for more effective therapy for PDA treatment. The effects of p21 activated kinases (PAKs) on tumour immune response and gemcitabine response were examined in PDA. An orthotopic murine PDA model, in which pancreatic cancer cells were injected to the tail of pancreas, was used. The mice were treated with PAK inhibitor, PF­3758309, plus or minus gemcitabine. Tumour growth was measured by volume and weight. Tumour immune response was determined by flow cytometry analysis of splenic cells and immunohistochemical staining of intratumoural lymphocytes. Inhibition of PAKs by PF­3758309, not only suppressed tumour growth, but also stimulated tumour immune response by increasing the numbers of splenic and intratumoural T lymphocytes. Furthermore, inhibition of PAKs decreased PDA cell growth synergistically with gemcitabine in vitro and in vivo. The dual effects of inhibition of PAKs make PAK-targeted therapy more potent for the treatment of PDA. The combination of PAK inhibitors with gemcitabine may be a more effective therapeutic approach in PDA treatment.

Depletion of p21-activated kinase 1 up-regulates the immune system of APC∆14/+ mice and inhibits intestinal tumorigenesis.

BACKGROUND: P21-activated kinase 1 (PAK1) stimulates growth and metastasis of colorectal cancer (CRC) through activation of multiple signalling pathways. Up-regulation of CRC stem cell markers by PAK1 also contributes to the resistance of CRC to 5-fluorouracil. The aim of this study was to investigate the effect of PAK1 depletion and inhibition on the immune system and on intestinal tumour formation in APC∆14/+ mice. METHODS: The PAK1 KO APC∆14/+ mice were generated by cross-breeding of PAK1 KO mice with APC∆14/+ mice. Splenic lymphocytes were analysed by flow cytometry, and immunohistochemical staining. The numbers of intestinal tumours were counted. Blood cells were also counted. RESULTS: Compared to APC+/+ mice, the numbers of both T- and B- lymphocytes were reduced in the spleen of APC∆14/+ mice. Depletion of PAK1 in APC∆14/+ mice increased the numbers of splenic T- and B- lymphocytes and decreased the numbers of intestinal tumours. Treatment of APC∆14/+ mice with PF-3758309, a PAK inhibitor reduced the numbers of intestinal tumours and increased the numbers of blood lymphocytes. CONCLUSION: Depletion of active PAK1 up-regulates the immune system of APC∆14/+ mice and suppresses intestinal tumour development. These observations suggest an important role for PAK1 in the immune response to tumours.

Up-regulation of stem cell markers by P21-activated kinase 1 contributes to 5-fluorouracil resistance of colorectal cancer.

Cancer stem cells (CSC) are tumorigenic and resistant to chemotherapy. In colorectal cancer (CRC), CSCs have been identified by the expression of specific markers, including CD44, Bmi1 and Nanog. Although p21-activated kinase 1 (PAK1), acting downstream of Ras, stimulates Wnt/ß-catenin signaling and is known to play an important role in CRC development and progression, the role of PAK1 in the expression of CSC markers has not previously been investigated. The effect of PAK1 over-expression, knockdown or inhibition on the expression or alteration (in the case of CD44) of CSC markers in human CRC cell lines was measured by immunofluorescence and Western blotting. The effect of PAK1 modulation on tumorigenesis, and on resistance to treatment with 5-fluorouracil (5-FU), was measured by sphere formation in vitro and by growth of xenografted tumors in vivo. The results show that PAK1 activity correlated with the expression of CSC markers and the CD44 isoform profile, and with tumor growth both in vitro and in vivo. Furthermore PAK overexpression partially overcame the inhibition of CRC growth by 5-FU, and PAK inhibition was synergistic with 5-FU treatment. Our findings lay the foundation for a combination therapy in which PAK1 inhibitors targeting CSCs may be combined with conventional 5-FU-based chemotherapy for the treatment of CRC.

Glaucarubinone Combined with Gemcitabine Improves Pancreatic Cancer Survival in an Immunocompetent Orthotopic Murine Model.

BACKGROUND: Pancreatic cancer continues to have a poor survival rate with an urgent need for improved treatments. Glaucarubinone, a natural product first isolated from the seeds of the tree Simarouba glauca, has recently been recognized as having anti-cancer properties that may be particularly applicable to pancreatic cancer. METHODS: The effect of glaucarubinone on the growth and migration of murine pancreatic cancer cells was assessed by 3H-thymidine incorporation assay. The survival impact of glaucarubinone alone and in combination with gemcitabine chemotherapy was assessed using an immunocompetent orthotopic murine model of pancreatic cancer. RESULTS: Glaucarubinone inhibited the growth of the murine pancreatic cancer cell lines LM-P and PAN02. Treatment with either glaucarubinone or gemcitabine reduced proliferation in vitro and the combination was synergistic. The combination treatment improved survival two-fold compared to gemcitabine treatment alone (p = 0.046) in PAN02 cells. CONCLUSIONS: The synergistic inhibition by glaucarubinone and gemcitabine observed in vitro and the improved survival in vivo suggest that glaucarubinone may be a useful adjunct to current chemotherapy regimens.

Mid-term results of Ponseti management for an idiopathic congenital clubfoot at a single center in Vietnam.

Despite the increasing popularity of the Ponseti method for the treatment of idiopathic congenital clubfeet, the relapse rate and sequela after the initial correction of manipulating and casting remain high. This study presents a scale to evaluate the relapse and identify the factors correlated with the relapse and latest follow-up mid-term results. A total of 101 children (newborn to 12 months), 142 idiopathic congenital clubfeet, were recruited for this study following treatment with the Ponseti method at the Hospital for Traumatology and Orthopaedics (Ho Chi Minh City, Vietnam) with a follow-up period of a minimum of 2 years. The clubfeet were then classified and evaluated during casting, for initial correction, and for relapse according to Diméglio's score. Next, the latest follow-up results were evaluated according to Richards' classification. The initial correction was successful in 95.8% (perfect: 74.0%, acceptable: 21.8%); 6.6% developed relapses and relapse-related factors were the initial correction and bracing program. The latest follow-up results are good in 74.7%, fair in 22.5%, and poor in 2.8%, and correlated with the age of presentation and the follow-up period in both univariate and multivariate analysis. On the basis of a precise evaluation of the relapse, this study indicates that the initial correction classified by the author on the basis of Diméglio's score and bracing compliance affect relapse. In addition, early treatment after birth and continuous long-term follow-up to appropriately manage the sequelae are essential to obtain the latest follow-up results as expected.

Glaucarubinone inhibits colorectal cancer growth by suppression of hypoxia-inducible factor 1α and ß-catenin via a p-21 activated kinase 1-dependent pathway.

p-21-Activated kinase 1 (PAK1) enhances colorectal cancer (CRC) progression by stimulating Wnt/ß-catenin, ERK and AKT pathways. PAK1 also promotes CRC survival via up-regulation of hypoxia-inducible factor 1α (HIF-1α), a key player in cancer survival. Glaucarubinone, a quassinoid natural product, inhibits pancreatic cancer growth by down-regulation of PAK1. The aim of this study was to investigate the effect of glaucarubinone on CRC growth and metastasis, and the mechanism involved. Cell proliferation was measured in vitro by [(3)H]-thymidine incorporation and in vivo by volume of tumor xenografts. Protein concentrations were measured by Western blotting of cell extracts. We report here that glaucarubinone inhibited CRC growth both in vitro and in vivo. The potency of glaucarubinone as an inhibitor of cell proliferation was negatively correlated to PAK1 expression in CRC cells. Glaucarubinone suppressed the expression of HIF-1α and ß-catenin. Knockdown of PAK1 by shRNA enhanced inhibition by glaucarubinone while constitutively active PAK1 blocked the inhibitory effect. Our findings indicate that glaucarubinone inhibited CRC growth by down-regulation of HIF-1α and ß-catenin via a PAK1-dependent pathway.

Demonstration and biological significance of a gastrin-P21-activated kinase 1 feedback loop in colorectal cancer cells.

Gastrins, including amidated gastrin17 and glycine-extended gastrin17, are important growth factors in colorectal cancer (CRC). The p21-activated kinase 1 (PAK1) plays key roles in cellular processes including proliferation, survival, and motility, and in cell transformation and tumor progression. PAK1 expression increases with the progression of CRC, and knockdown of PAK1 blocks CRC cell growth and metastasis both in vitro and in vivo. The aim of this study was to determine the interaction between PAK1 and gastrins in CRC cells. PAK1 expression and activation were assayed by Western blots, and concentrations of gastrin mRNA and peptides by real-time PCR and radioimmunoassay, respectively. Proliferation of CRC cells was measured by (3)H-thymidine incorporation, and vascular endothelial growth factor : VEGF) secretion was measured by ELISA. Gastrins activated PAK1 via PI3K-dependent pathways. Activated PAK1 in turn mediated gastrin-stimulated activation of ß-catenin and VEGF secretion in CRC cells, as knockdown of PAK1 blocked stimulation of these cellular processes by gastrins. Downregulation of gastrin reduced the expression and activity of PAK1, but in contrast there was a compensatory increase in gastrins either when PAK1 was downregulated, or after treatment with a PAK inhibitor. Our results indicate that PAK1 is required for the stimulation of CRC cells by gastrins, and suggest the existence of an inhibitory feedback loop by which PAK1 downregulates gastrin production in CRC cells.

Glaucarubinone and gemcitabine synergistically reduce pancreatic cancer growth via down-regulation of P21-activated kinases.

Pancreatic cancer is one of the most lethal of human malignancies. Nearly 100% cases of pancreatic cancer carry mutations in KRas. P-21-activated kinases (PAKs) are activated by and act downstream of KRas. Glaucarubinone, a natural product first isolated from the seeds of the tree Simarouba glauca, was originally developed as an antimalarial drug, and has more recently been recognised as an anticancer agent. The aims of this study were to determine whether glaucarubinone, alone or in combination with the front-line chemotherapeutic agent gemcitabine, would inhibit the growth of pancreatic cancer cells in vitro or in vivo and the mechanism involved. Growth of the human pancreatic cancer cell lines PANC-1 and MiaPaCa-2 was measured by (3)H-thymidine incorporation in vitro, and by volume as xenografts in SCID mice. The expression and activities of the two serine/threonine kinases PAK1 and PAK4, which are key regulators of cancer progression, were measured by Western blotting. Here we report that glaucarubinone decreased proliferation and migration of pancreatic cancer cells in vitro, and reduced their growth as xenografts in vivo. Treatment with glaucarubinone and gemcitabine reduced proliferation in vitro and tumor growth in vivo more than treatment with either glaucarubinone or gemcitabine alone. Treatment with glaucarubinone reduced PAK1 and PAK4 activities, which were further decreased by the combination of glaucarubinone and gemcitabine. These results indicate that glaucarubinone reduced pancreatic cancer cell growth at least in part via inhibition of pathways involving PAK1 and PAK4. The synergistic inhibition by glaucarubinone and gemcitabine observed both in vitro and in vivo suggests that glaucarubinone may be a useful adjunct to current regimes of chemotherapy.

P21-activated kinase 1 promotes colorectal cancer survival by up-regulation of hypoxia-inducible factor-1α.

P21 activated kinase 1 (PAK1) enhances colorectal cancer (CRC) progression by stimulating Wnt/ß-catenin and Ras oncogene, which promote CRC survival via stimulation of hypoxia-inducible factor 1α (HIF-1α). The aim of this study was to assess the mechanism involved in the stimulation by PAK1 of CRC survival. PAK1 promoted CRC cell survival by up-regulation of HIF-1α. PAK1 was over-expressed and hyper-activated in tumors of ApcΔ(14/+) mice, which was correlated with over-expression of HIF-1α and ß-catenin. Inhibition of PAK1 decreased tumor growth and the expression of HIF-1α and ß-catenin in tumors of ApcΔ(14/+) mice, and suppressed xenograft tumor survival in SCID mice. These findings indicate that PAK1 stimulates CRC survival by up-regulation of HIF-1α.

p-21-Activated kinase 1 mediates gastrin-stimulated proliferation in the colorectal mucosa via multiple signaling pathways.

Gastrins, including amidated (Gamide) and glycine-extended (Ggly) forms, function as growth factors for the gastrointestinal mucosa. The p-21-activated kinase 1 (PAK1) plays important roles in growth factor signaling networks that control cell motility, proliferation, differentiation, and transformation. PAK1, activated by both Gamide and Ggly, mediates gastrin-stimulated proliferation and migration, and activation of ß-catenin, in gastric epithelial cells. The aim of this study was to investigate the role of PAK1 in the regulation by gastrin of proliferation in the normal colorectal mucosa in vivo. Mucosal proliferation was measured in PAK1 knockout (PAK1 KO) mice by immunohistochemistry. The expression of phosphorylated and unphosphorylated forms of the signaling molecules PAK1, extracellular signal-regulated kinase (ERK), and protein kinase B (AKT), and the expression of ß-catenin and its downstream targets c-Myc and cyclin D1, were measured in gastrin knockout (Gas KO) and PAK1 KO mice by Western blotting. The expression and activation of PAK1 are decreased in Gas KO mice, and these decreases are associated with reduced activation of ERK, AKT, and ß-catenin. Proliferation in the colorectal mucosa of PAK1 KO mice is reduced, and the reduction is associated with reduced activation of ERK, AKT, and ß-catenin. In compensation, antral gastrin mRNA and serum gastrin concentrations are increased in PAK1 KO mice. These results indicate that PAK1 mediates the stimulation of colorectal proliferation by gastrins via multiple signaling pathways involving activation of ERK, AKT, and ß-catenin.

P-21 activated kinase 1 knockdown inhibits ß-catenin signalling and blocks colorectal cancer growth.

The p21-activated kinase 1 (PAK1) plays important roles in cell growth, motility, and transformation. The aims of this study were to delineate the signalling mechanisms downstream of PAK1, and to investigate the importance of PAK1 for colorectal cancer (CRC) growth and metastasis in vivo. PAK1 knockdown in human CRC cell lines inhibited ß-catenin expression, ß-catenin/TCF4 transcriptional activity, and the expression of c-Myc. In mouse models PAK1 knockdown suppressed the growth and metastasis of human CRC cells by decreasing proliferation and increasing apoptosis. Our findings demonstrate for the first time the crucial role of PAK1 in CRC progression in vivo.