Group Ⅱ p21-activated kinases as therapeutic targets in gastrointestinal cancer

P21-activated kinases(PAKs) are central players in various oncogenic signaling pathways. The six PAK family members are classified into group Ⅰ(PAK1-3) and group Ⅱ(PAK4-6). Focus is currently shifting from group Ⅰ PAKs to group Ⅱ PAKs. Group Ⅱ PAKs play important roles in many fundamental cellular processes, some of which have particular significance in the development and progression of cancer. Because of their important functions, group Ⅱ PAKs have become popular potential drug target candidates. However, few group Ⅱ PAKs inhibitors have been reported, and most do not exhibit satisfactory kinase selectivity and "drug-like" properties. Isoform- and kinase-selective PAK inhibitors remain to be developed. This review describes the biological activities of group Ⅱ PAKs, the importance of group Ⅱ PAKs in the development and progression of gastrointestinal cancer, and smallmolecule inhibitors of group Ⅱ PAKs for the treatment of cancer.

PAK6、p53在膀胱癌中的表达及其临床意义

目的探讨P21活化激酶6(p21-activated kinase 6,PAK6)以及p53在膀胱癌中的表达及其临床意义。方法取膀胱癌患者85例作为膀胱癌组,并取其膀胱癌组织;取行膀胱部分切除或全部切除术患者35例为对照组,取其正常膀胱上皮组织。采用免疫组织化学法检测2组组织PAK6、p53蛋白阳性表达率。Biu-87组、T24组膀胱癌细胞和SV-HUC-1正常膀胱细胞分为Biu-87组、T24组和SV-HUC-1组,采用实时荧光定量PCR法检测3组细胞的PAK6、p53 mRNA表达水平。结果膀胱癌组PAK6蛋白阳性表达率低于对照组(P<0.05),膀胱癌组复发者PAK6蛋白阳性表达率低于原发者(P<0.05)。膀胱癌组PAK6蛋白阳性表达率在肿瘤数量、是否转移、病理分级以及临床分期上差异无统计学意义(P>0.05)。Biu-87组、T24组细胞PAK6 mRNA表达水平均低于SV-HUC-1组(P<0.05)。Biu-87组、T24组细胞p53 mRNA表达水平均高于SV-HUC-1组(P<0.05)。结论PAK6在膀胱癌细胞中以及膀胱癌组织中低表达,并且与膀胱癌的复发有着密切的联系,在膀胱癌发生发展中有抑制作用,PAK6可能会作为新的抑癌指标用以指导临床。p53在膀胱癌细胞与膀胱癌组织中高表达,与病理分级、临床分期等密切相关,具有评估膀胱癌预后的价值。

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.

Activation of Rac1-PI3K/Akt is required for epidermal growth factorinduced PAK1 activation and cell migration in MDA-MB-231 breast cancer cells

Epidermal growth factor （EGF） may increase cell motility, an event implicated in cancer cell invasion and metastasis. However, the underlying mechanisms for EGF-induced cell motility remain elusive. In this study, we found that EGF treatment could activate Ras-related C3 botulinum toxin substrate 1 （Racl）, PI3K/Akt and p21- actived kinase （PAK1） along with cell migration. Ectopic expression of PAK1 K299R, a dominant negative PAK1 mutant, could largely abolish EGF-induced cell migration. Blocking PI3K/Akt signalling with LY294002 or Akt siRNA remarkably inhibited both EGF-induced PAK1 activation and cell migration. Furthermore, expression of dominant-negative Racl （T17N） could largely block EGF-induced PI3K/Akt-PAK1 activation and cell migration. Interestingly, EGF could induce a significant production of ROS, and N-acetyl-L-cysteine, a scavenger of ROS which abolished the EGF-induced ROS generation, cell migration, as well as activation of PI3K/Akt and PAK, but not Racl. Our study demonstrated that EGF-induced cell migration involves a cascade of signalling events, including activation of Racl, generation of ROS and subsequent activation of PI3K/Akt and PAK1.

6-氯喹唑啉类PAK4抑制剂的设计合成及生物活性研究

目的设计合成6-氯喹唑啉类p21活化激酶4(PAK4)抑制剂,并对其酶抑制活性进行评价。方法以2-氨基-5-氯苯甲酸为起始原料,经过环合反应、氯代反应、两次芳香亲核取代反应制得6-氯-2-胺基-4-[(3,5-二(三氟甲基))苄基]胺基喹唑啉类化合物(A类);以取代的甲酸乙酯为起始原料,经过Claisen缩合反应、环合反应、取代反应制得6-氯-2-胺基-4-(1H-3-吡唑基)胺基喹唑啉类化合物(B类)。采用HTRF技术测试目标化合物对PAK4的体外酶抑制活性。结果与结论合成了22个6-氯喹唑啉类衍生物,目标化合物的结构经ESI-MS和1H-NMR谱确证;初步体外酶活性测试结果表明,A类化合物的活性弱于先导化合物Cl-02(N4-3,5-双三氟甲基苄基-N2-环己基喹唑啉-2,4-二胺),B类化合物的活性优于先导化合物Cl-02,其中有8个化合物在1μmol·L^-1时对PAK4的抑制率达到50%以上,具有进一步研究的价值。

MiR-32-5p aggravates intestinal epithelial cell injury in pediatric enteritis induced by Helicobacter pylori

BACKGROUND Pediatric enteritis is one of the infectious diseases in the digestive system that causes a variety of digestive problems,including diarrhea,vomiting,and bellyache in children.Clinically,Helicobacter pylori(H.pylori)infection is one of the common factors to cause pediatric enteritis.It has been demonstrated that aberrant expression of microRNAs(miRNAs)is found in gastrointestinal diseases caused by H.pylori,and we discovered a significant increase of miR-32-5p in H.pylori-related pediatric enteritis.However,the exact role of miR-32-5p in it is still unknown.AIM To investigate the role of aberrant miR-32-5p in pediatric enteritis induced by H.pylori.METHODS MiR-32-5p expression was detected by quantitative real time-polymerase chain reaction.The biological role of miR-32-5p in H.pylori-treated intestinal epithelial cells was evaluated by Cell Counting Kit-8 assay and flow cytometry.The potential target of miR-32-5p was predicted with TargetScanHuman and verified by luciferase assay.The downstream mechanism of miR-32-5p was explored by using molecular biology methods.RESULTS We found that miR-32-5p was overexpressed in serum of H.pylori-induced pediatric enteritis.Further investigation revealed that H.pylori infection promoted the death of intestinal epithelial cells,and increased miR-32-5p expression.Moreover,miR-32-5p mimic further facilitated apoptosis and inflammatory cytokine secretion of intestinal epithelial cells.Further exploration revealed that SMAD family member 6(SMAD6)was the direct target of miR-32-5p,and SMAD6 overexpression partially rescued cell damage induced by H.pylori.The following experiments showed that miR-32-5p/SMAD6 participated in the apoptosis of intestinal epithelial cells induced by transforming growth factor-β-activated kinase 1(TAK1)-p38 activation under H.pylori infection.CONCLUSION Our work uncovered the crucial role of aberrant expression of miR-32-5p in H.pylori–related pediatric enteritis,and suggested that the TAK1-p38 pathway is involved in it.

Expression and role of PAK6 after spinal cord injury in adult rat

Objective： To observe p21-activated kinase 6 （PAK6） expression and its possible role after spinal cord injury （SCI） in adult rat.Methods： Sprague-Dawley rats were subjected to spinal cord injury. To explore the pathological and physiological significance of PAK6, the expression patterns and distribution of PAK6 were observed by Western blot, immunohistochemistry and immunofluorescence.Results： Western blot analysis showed PAK6 protein level was significantly up-regulated on day 2 and day 4,then reduced and had no up-regulation till day 14. Immunohistochemistry analysis showed that the expression of PAK6 was significantly increased on day 4 compared with the control group. Besides, double immunofluorescence staining showed PAK6 was primarily expressed in the neurons and astrocytes in the control group. While after injury, the expression of PAK6 was increased significantly in the astrocytes and neurons, and the astrocytes were largely proliferated. We also examined the expression of proliferating cell nuclear antigen （PCNA） and found its change was correlated with the expression of PAK6. Importantly, double immunofluorescence staining revealed that cell proliferation evaluated by PCNA appeared in many PAK6-expressing cells on day 4 after injury.Conclusion： The up-regulation of PAK6 in the injured spinal cord may be associated with glial proliferation.

PAK1 is a novel cardiac protective signaling molecule

We review here the novel cardiac protective effects of the multifunctional enzyme, p21-aetivated kinase 1 （PAK1）, a member of a serine/threonine protein kinase family. Despite the large body of evidence from studies in noncardiac tissue indicating that PAK1 activity is key in the regulation of a number of cellular functions, the role of PAK1 in the heart has only been revealed over the past few years. In this review, we assemble an overview of the recent findings on PAKI signaling in the heart, particularly its cardiac protective effects. We present a model for PAK1 signaling that provides a mechanism for specifically affecting cardiac cellular processes in which regulation of protein phosphorylation states by protein phosphatase 2A （PP2A） predominates. We discuss the anti-adrenergic and antihypertrophic cardiac protective effects of PAK1, as well as its role in maintaining ventricular Ca2＋ homeostasis and electrophysiological stability under physiological, β-adrenergic and hypertrophic stress conditions.