Opposing effects of protein kinase Calpha and protein kinase Cepsilon on collagen expression by human lung fibroblasts are mediated via MEK/ERK and caveolin-1 signaling

The roles of MEK, ERK, the epsilon and alpha isoforms of protein kinase C (PKC), and caveolin-1 in regulating collagen expression were studied in normal lung fibroblasts. Knocking down caveolin-1 gave particularly striking results. A 70% decrease caused a 5-fold increase in MEK/ERK activation and collagen expression. The combined data reveal a branched signaling pathway. In its central portion MEK activates ERK, leading to increased collagen expression. Two branches converge on MEK/ERK. In one, increased PKCepsilon leads to MEK/ERK activation. In another, increased PKCalpha induces caveolin-1 expression, which in turn inhibits MEK/ERK activation and collagen expression. Lung fibroblasts from scleroderma patients with pulmonary fibrosis showed altered signaling. Consistent with their overexpression of collagen, scleroderma lung fibroblasts contain more activated MEK/ERK and less caveolin-1 than normal lung fibroblasts. Because cutaneous fibrosis is the hallmark of scleroderma, we also studied dermal fibroblasts. As in lung, there was more activated MEK/ERK in cells from scleroderma patients than in control cells, and MEK inhibition decreased collagen expression. However, the distinctive levels of PKCepsilon, PKCalpha, and caveolin-1 in lung and dermal fibroblasts from scleroderma patients and control subjects indicate that the links between these signaling proteins and MEK/ERK must function differently in the four cell types. Finally, we confirmed the relevance of these signaling cascades in vivo. The combined results demonstrate that a branched signaling pathway involving MEK, ERK, PKCepsilon, PKCalpha, and caveolin-1 regulates collagen expression in normal lung tissue and is perturbed during fibrosis.     

Neuroendocrine differentiation contributes to radioresistance development and metastatic potential increase in non-small cell lung cancer

Radiation treatment induces neuroendocrine differentiation (NED) in non-small cell lung cancer (NSCLC) A549 and H157 cells, so higher NE-like features in radioresistant A549 (A549R26-1) and H157 (H157R24-1) cells are observed than in parental cells. We detected higher NED marker expressions in A549R26-1 cell-derived tumors than in A549 cell-derived tumors. In mechanism studies, we found that NED induction in A549R26-1 and H157R24-1 cells was accompanied by increased intracellular cAMP and IL-6 levels. Treatment of radioresistant lung cancer cells with the inhibitor (SQ22536) of adenylate cyclase (AC) which is the enzyme responsible for the cAMP production, or the neutralizing antibody (Ab) of IL-6, resulted in decreased NE-like features in radioresistant lung cancer cells. In addition, we found MEK/Erk is the signaling pathway that triggers the cAMP- and IL-6-mediated NED induction in radioresistant lung cancer cells. Also, we found that MEK/Erk signaling pathway inhibition decreased NED in radioresistant cells. Radioresistant lung cancer cells exhibiting high NE-like features also showed higher radioresistance and higher metastatic potential than parental cells. When we inhibited cAMP-, or IL-6-mediated pathways, or the downstream MEK/Erk signaling pathway, radiosensitivity of radioresistant lung cancer cells was significantly increased and their metastatic potential was significantly reduced. In in vivo mouse studies, reducing NED by treating mice with the MEK/Erk inhibitor increased radiosensitivity. Immunohistochemical staining of tumor tissues lowered expressions of the NED/epithelial-mesenchymal transition (EMT)/metastatic markers when mice were treated with the MEK/Erk inhibitor.     

Tamoxifen inhibits tumor cell invasion and metastasis in mouse melanoma through suppression of PKC/MEK/ERK and PKC/PI3K/Akt pathways

In melanoma, several signaling pathways are constitutively activated. Among these, the protein kinase C (PKC) signaling pathways are activated through multiple signal transduction molecules and appear to play major roles in melanoma progression. Recently, it has been reported that tamoxifen, an anti-estrogen reagent, inhibits PKC signaling in estrogen-negative and estrogen-independent cancer cell lines. Thus, we investigated whether tamoxifen inhibited tumor cell invasion and metastasis in mouse melanoma cell line B16BL6. Tamoxifen significantly inhibited lung metastasis, cell migration, and invasion at concentrations that did not show anti-proliferative effects on B16BL6 cells. Tamoxifen also inhibited the mRNA expressions and protein activities of matrix metalloproteinases (MMPs). Furthermore, tamoxifen suppressed phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt through the inhibition of PKCα and PKCδ phosphorylation. However, other signal transduction factor, such as p38 mitogen-activated protein kinase (p38MAPK) was unaffected. The results indicate that tamoxifen suppresses the PKC/mitogen-activated protein kinase kinase (MEK)/ERK and PKC/phosphatidylinositol-3 kinase (PI3K)/Akt pathways, thereby inhibiting B16BL6 cell migration, invasion, and metastasis. Moreover, tamoxifen markedly inhibited not only developing but also clinically evident metastasis. These findings suggest that tamoxifen has potential clinical applications for the treatment of tumor cell metastasis.     

Flavanone and 2'-OH flavanone inhibit metastasis of lung cancer cells via down-regulation of proteinases activities and MAPK pathway

Flavanones richly exist in citrus and have been well characterized to have various bioactive properties. However, the anti-metastasis properties of flavanones remain unclear. The anti-metastatic effects of six flavanones including flavanone, 2'-OH flavanone, 4'-OH flavanone, 6-OH flavanone, naringin, and naringenin were investigated in lung cancer cells. Despite little influence on cell viability, flavanone and 2'-OH flavanone markedly inhibited the invasion, motility, and cell-matrix adhesion of A549 cells. This was associated with a reduced expression of matrix metalloproteinase (MMP)-2 and urokinase-type plasminogen activator (u-PA) in treated cells. Treatment with flavanone and 2'-OH flavanone also potently attenuated the phosphorylations of extracellular signal-regulated kinase 1/2 (ERK 1/2) and p38(MAPK), as well as the activations of NF-kappaB and AP-1. The reduced expressions of MMP-2 and u-PA, as well as inhibition of cell invasion were obtained in the cultures treated with U0126 (ERK 1/2 inhibitor) and SB203580 (p38(MAPK) inhibitor). Thus, the inhibitory effects of flavanone and 2'-OH flavanone on the expression of MMP-2 and u-PA may be at least partly through inactivation of ERK 1/2 and p38(MAPK) signaling pathways. Finally, oral administration of flavanone and 2'-OH flavanone were evidenced by its inhibition on the metastasis of A549 cells and Lewis lung carcinoma (LLC) cells in vivo. In conclusion, flavanone and 2'-OH flavanone perturb the invasion and metastasis of lung cancer cells, thereby constituting an adjuvant treatment for metastasis control.     

RANKL increases migration of human lung cancer cells through intercellular adhesion molecule-1 up-regulation

Invasion of distant tissues by tumor cells is the primary cause of therapeutic failure in the treatment of malignant lung cancer cells. Receptor activator of nuclear factor-κB ligand (RANKL) and its receptor, RANK, play a key role in osteoclastogenesis and tumor metastasis. Intercellular adhesion molecule-1 (ICAM-1, also called CD54), a member of the immunoglobulin supergene family, is an inducible surface glycoprotein that mediates adhesion-dependent cell-to-cell interactions. The effects of RANKL on cell migration and ICAM-1 expression in human lung cancer cells are largely unknown. We found that RANKL directed the migration and increased ICAM-1 expression in human lung cancer (A549) cells. Pretreatment of A549 cells with the MAPK kinase (MEK) inhibitor PD98059 or U0126 inhibited RANKL-mediated migration and ICAM-1 expression. Stimulation of cells with RANKL increased the phosphorylation of MEK and extracellular signal-regulating kinase (ERK). In addition, an NF-κB inhibitor (PDTC) and IκB protease inhibitor (TPCK) also inhibited RANKL-mediated cell migration and ICAM-1 up-regulation. Taken together, these results suggest that the RANKL and RANK interaction acts through MEK/ERK, which in turn activates NF-κB, resulting in the activation of ICAM-1 and contributing to the migration of human lung cancer cells.     

Centchroman suppresses breast cancer metastasis by reversing epithelial–mesenchymal transition via downregulation of HER2/ERK1/2/MMP-9 signaling

Metastatic spread during carcinogenesis worsens disease prognosis and accelerates the cancer progression. Therefore, newer therapeutic options with higher specificity toward metastatic cancer are required. Centchroman (CC), a female oral contraceptive, has previously been reported to possess antiproliferative and proapoptotic activities in human breast cancer cells. Here, we investigated the effect of CC-treatment against breast cancer metastasis and associated molecular mechanism using in vitro and in vivo models. CC significantly inhibited the proliferation of human and mouse mammary cancer cells. CC-treatment also inhibited migration and invasion capacities of highly metastatic MDA-MB-231 and 4T1 cells, at sub-IC₅₀ concentrations. Inhibition of cell migration and invasion was found to be associated with the reversal of epithelial-to-mesenchymal transition (EMT) as observed by the upregulation of epithelial markers and downregulation of mesenchymal markers as well as decreased activities of matrix metalloproteinases. Experimental EMT induced by exposure to TGFβ/TNFα in nontumorigenic human mammary epithelial MCF10A cells was also reversed by CC as evidenced by morphological changes and modulation in the expression levels of EMT-markers. CC-mediated inhibition of cellular migration was, at least partially, mediated through inhibition of ERK1/2 signaling, which was further validated by using MEK1/2 inhibitor (PD0325901). Furthermore, CC-treatment resulted in suppression of tumor growth and lung metastasis in 4T1-syngeneic mouse model. Collectively, our findings suggest that CC-treatment at higher doses specifically induces cellular apoptosis and inhibits cellular proliferation; whereas at lower doses, it inhibits cellular migration and invasion. Therefore, CC could further be developed as an effective drug candidate against metastatic breast cancer.     

Apo-10’-lycopenoic acid inhibits cancer cell migration and angiogenesis and induces peroxisome proliferator-activated receptor γ

ScopeWe have previously shown that apo-10’-lycopenoic acid (ALA), a derivative of lycopene through cleavage by carotene-9’,10’-oxygenase, inhibits tumor progression and metastasis in both liver and lung cancer animal models. The underlying mechanism remains unknown. We hypothesized that ALA inhibits cancer cell motility and angiogenesis by up-regulating peroxisome proliferator-activated receptor γ (PPARγ) which is involved in controlling angiogenesis, tumor progression and metastasis.Methods and resultsALA treatment, in dose-dependent manner, was effective at inhibiting migration and invasion of liver and lung cancer cells (HuH7 and A549) in both Transwell and wound-healing models, as well as suppressing actin remodeling and ruffling/lamellipodia formation in HuH7 and immortalized lung BEAS-2B cells. ALA treatment resulted in suppression of angiogenesis in both tube formation and aortic ring assays and inhibition of matrix metalloproteinase-2 expression and activation in both HuH7 and A549 cells. Additionally, ALA dose-dependently increased the mRNA expression and protein levels of PPARγ in human THLE-2 liver cells.ConclusionALA inhibits cancer cell motility and angiogenesis and induces PPARγ expression, which could be one of the potential mechanisms for ALA protecting against tumor progression.     

SSeCKS/Gravin/AKAP12 Inhibits Cancer Cell Invasiveness and Chemotaxis by Suppressing a Protein Kinase C- Raf/MEK/ERK Pathway

SSeCKS/Gravin/AKAP12 (“SSeCKS”) encodes a cytoskeletal protein that regulates G₁ → S progression by scaffolding cyclins, protein kinase C (PKC) and PKA. SSeCKS is down-regulated in many tumor types including prostate, and when re-expressed in MAT-LyLu (MLL) prostate cancer cells, SSeCKS selectively inhibits metastasis by suppressing neovascularization at distal sites, correlating with its ability to down-regulate proangiogenic genes including Vegfa. However, the forced re-expression of VEGF only rescues partial lung metastasis formation. Here, we show that SSeCKS potently inhibits chemotaxis and Matrigel invasion, motility parameters contributing to metastasis formation. SSeCKS suppressed serum-induced activation of the Raf/MEK/ERK pathway, resulting in down-regulation of matrix metalloproteinase-2 expression. In contrast, SSeCKS had no effect on serum-induced phosphorylation of the Src substrate, Shc, in agreement with our previous data that SSeCKS does not inhibit Src kinase activity in cells. Invasiveness and chemotaxis could be restored by the forced expression of constitutively active MEK1, MEK2, ERK1, or PKCα. SSeCKS suppressed phorbol ester-induced ERK1/2 activity only if it encoded its PKC binding domain (amino acids 553–900), suggesting that SSeCKS attenuates ERK activation through a direct scaffolding of conventional and/or novel PKC isozymes. Finally, control of MLL invasiveness by SSeCKS is influenced by the actin cytoskeleton: the ability of SSeCKS to inhibit podosome formation is unaffected by cytochalasin D or jasplakinolide, whereas its ability to inhibit MEK1/2 and ERK1/2 activation is nullified by jasplakinolide. Our findings suggest that SSeCKS suppresses metastatic motility by disengaging activated Src and then inhibiting the PKC-Raf/MEK/ERK pathways controlling matrix metalloproteinase-2 expression and podosome formation.     

Bone morphogenetic protein-2-induced transformation involves the activation of mammalian target of rapamycin

Bone morphogenetic protein-2 (BMP-2) is an evolutionary conserved protein that is essential for embryonic development. BMP-2 is highly expressed in approximately 98% of human lung carcinomas with little expression in normal lung tissues. BMP-2 has been shown to enhance mobility, invasiveness, and metastasis of cancer cell lines. During development, BMP-2 induces the proto-oncogene phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway to regulate stem cell differentiation. We show that BMP-2 induces the phosphorylation of mTOR in A549 and H1299 lung cancer cell lines, which is attenuated by the PI3K antagonists LY-294002 and wortmannin. p70S6 kinase, which is a direct downstream target of mTOR, is also regulated by BMP-2 in lung cancer cell lines. We find that BMP-2 induces cyclin E in A549 and H1299 cells, which is mediated by the PI3K/mTOR signaling pathway. The regulation of cyclin E by BMP-2 occurs through a Smad 1/5-independent mechanism. Forced expression of BMP-2 in A549 cells (A549/BMP-2) induces transformation as shown by an increase in foci formation. The mTOR antagonist, rapamycin, prevented foci formation of the A549/BMP-2 cells. This study provides evidence that BMP-2-mediated transformation of lung cancer cells involves the activation of the PI3K/mTOR signaling pathway.     

Erlotinib inhibits colon cancer metastasis through inactivation of TrkB-dependent ERK signaling pathway

The distal metastasis is the main cause of death in patients with colon cancer. Tyrosine receptor kinase B (TrkB) and ERK signals may be the potential targets for the treatment of colon cancer metastasis. This study aims to investigate whether erlotinib inhibits distant metastasis of colon cancer by regulating TrkB and ERK signaling pathway. Human colon adenocarcinoma cell lines (SW480 and Caco-2) pretreated with exogenous C-X-C motif chemokine ligand 8 (CXCL8) were used to assess the suppressive effect of erlotinib on tumor metastasis, including anoikis, epithelial-mesenchymal transformation (EMT), migration, and invasion. Through TrkB overexpression, Akt suppression, and ERK suppression, the roles of TrkB, Akt, and ERK in erlotinib-induced metastasis inhibition of colon cancer cells were explored. The results showed that erlotinib alleviated CXCL8-induced metastasis of the colon cancer cells. Overexpression of TrkB in colon cancer cells eliminated the effect of erlotinib on anoikis, inhibition of EMT, migration, and invasion, and downregulation of p-ERK and p-Akt. Furthermore, the inhibition of ERK activation instead of Akt activation was found to participate in erlotinib-mediated metastasis resistance, including anoikis, inhibition of EMT, migration, and invasion. In conclusion, erlotinib inhibits colon cancer cell anoikis resistance, EMT, migration, and invasion by inactivating TrkB-dependent ERK signaling pathway.     

CK2 inhibitor CX4945 induces sequential inactivation of proteins in the signaling pathways related with cell migration and suppresses metastasis of A549 human lung cancer cells

Casein kinase 2 (CK2) is known to be involved in various cellular processes such as cell cycle, apoptosis and proliferation. It has been reported that the inhibition of CK2 induced by recently developed small molecule CX4945 shows anti-cancer effects including anti-proliferation and anti-angiogenesis in several different cancers including prostate cancer. Here we report that migration and invasion of A549 human lung cancer cells are suppressed by the inhibition of CK2 induced by CX4945. We found that CX4945 sequentially attenuates the proteins in PI3K/Akt and MAPK pathways, two signaling pathways related with cell migration. This sequential control of signal pathways inhibits the expression of membrane type 1-matrix metalloproteinase and this leads to the selective attenuation of one of the gelatinases, MMP-2, which can degrade components of extracellular matrix, and metastasis of A549 human lung cancer cell.     

Integrin αvβ6 Promotes Lung Cancer Proliferation and Metastasis through Upregulation of IL-8–Mediated MAPK/ERK Signaling

Lung cancer is notorious for high morbidity and mortality around the world. Interleukin (IL)-8, a proinflammatory chemokine with tumorigenic and proangiogenic effects, promotes lung cancer cells growth and migration and contributes to cell aggressive phenotypes. Integrin αvβ6 is a receptor of transmembrane heterodimeric cell surface adhesion, and its overexpression correlates with poor survival from non–small cell lung cancer. However, the cross talk between αvβ6 and IL-8 in lung cancer has not been characterized so far. Herein, human lung cancer samples were analyzed, and it revealed that the immunohistochemical and mRNA expression of integrin αvβ6 was significantly correlated with the expression of IL-8. Furthermore, in vitro, integrin αvβ6 increased cell proliferation, migration, and invasion by impairing the expressions of MMP-2 and MMP-9 and inhibited cell apoptosis in human lung cancer cells A549 and H460. In addition, integrin αvβ6 upregulated IL-8 expression through activating MAPK/ERK signaling. The in vivo experiment showed that integrin αvβ6 promoted tumor growth in xenograft model mice by accelerating tumor volume and reducing apoptosis. Meanwhile, lung metastasis model experiment suggested that integrin αvβ6 stimulated tumor metastasis with the increase of lung/total weight and tumor nodules. Simultaneously, integrin αvβ6 upregulated IL-8 expression detected by both Western blots and immunohistochemistry, along with the activation of MAPK/ERK signaling. Overall, these data suggested that, in vitro and in vivo, integrin αvβ6 promoted lung cancer proliferation and metastasis, at least in part, through upregulation of IL-8–mediated MAPK/ERK signaling. Thus, the inhibition of integrin αvβ6 and IL-8 may be the key for the treatment of lung cancer.     

SPARCL1通过MEK/ERK信号通路调节非小细胞肺癌细胞的增殖、凋亡和侵袭

摘要 目的：分析富含半胱氨酸的酸性分泌蛋白类似蛋白1（SPARCL1）对非小细胞肺癌（NSCLC）细胞增殖、凋亡、侵袭的影响,并探讨分裂原活化抑制剂（MEK）/细胞外调节蛋白激酶（ERK）通路在其中发挥的作用。方法：收集2019年9月~2021年6月期间本院接受手术治疗的84例NSCLC患者癌组织与相应癌旁组织,实时定量逆转录聚合酶链反应（qRT-PCR）法测定并比较各组织以及正常肺上皮细胞HBEpiC、NSCLC细胞A549、HCC827、H1299、H292中SPARCL1 信使RNA（mRNA）表达水平,选取A549、HCC827培养并分组,分为对照组、NC siRNA组、SPARCL1 siRNA组、U0126组（MEK/ERK特异性抑制剂）、SPARCL1 siRNA加U0126组,细胞计数法（CCK8）以及平板克隆法测定A549、HCC827细胞增殖,流式细胞仪测定A549、HCC827细胞凋亡,Transwell小室法测定A549、HCC827细胞侵袭能力,蛋白质印迹法（western blot）检测SPARCL1、p-MEK、MEK、p-ERK1/2、ERK1/2蛋白表达。结果：SPARCL1在NSCLC组织中mRNA表达水平低于癌旁组织（P＜0.05）;与HBEpiC细胞相比,NSCLC细胞A549、HCC827、H1299、H292细胞中SPARCL1 mRNA表达水平降低（P＜0.05）;与对照组相比,SPARCL1 siRNA组A549、HCC827细胞SPARCL1 mRNA表达水平与蛋白表达、凋亡率降低（P＜0.05）,OD₄₅₀、克隆形成数、侵袭细胞数、p-MEK/MEK、p-ERK1/2/ERK1/2蛋白表达升高（P＜0.05）,U0126组A549、HCC827细胞SPARCL1 mRNA表达水平与蛋白表达、凋亡率升高（P＜0.05）,OD₄₅₀、克隆形成数、侵袭细胞数、p-MEK/MEK、p-ERK1/2/ERK1/2蛋白表达降低（P＜0.05）;与SPARCL1 siRNA组相比,SPARCL1 siRNA加U0126组A549、HCC827细胞SPARCL1 mRNA表达水平与蛋白表达、凋亡率升高（P＜0.05）,OD₄₅₀、克隆形成数、侵袭细胞数、p-MEK/MEK、p-ERK1/2/ERK1/2蛋白表达降低（P＜0.05）。结论：SPARCL1可能通过调控MEK/ERK通路影响NSCLC A549、HCC827细胞增殖、侵袭与凋亡。     

Interleukin-1beta-induced iNOS expression in human lung carcinoma A549 cells: involvement of STAT and MAPK pathways

For understanding of signaling molecules important in lung cancer growth and progression, IL-1beta effect was analyzed on iNOS expression and key signaling molecules in human lung carcinoma A549 cells and established the role of specific signaling molecules by using specific chemical inhibitors. IL-1beta exposure (10 ng/ml) induced strong iNOS expression in serum starved A549 cells. Detailed molecular analyses showed that IL-1beta increased expression of phosphorylated STAT1 (Tyr701 and Ser727) and STAT3 (Tyr705 and Ser727) both in total cell lysates and nuclear lysates. Further, IL-1beta exposure strongly activated MAPKs (ERK1/2, JNK1/2 and p38) and Akt as well as increased nuclear levels of NF-kappaB and HIF-1alpha in A549 cells. Use of specific chemical inhibitors for JAK1 kinase (piceatannol), JAK2 kinase (AG-490), MEK1/2 (PD98059) and JNK1/2 (SP600125) revealed that IL-1beta-induced iNOS expression involved signaling pathways in addition to JAK-STAT and ERK1/2-JNK1/2 activation. Overall, these results suggested that instead of specific pharmacological inhibitors, use of chemopreventive agents with broad spectrum efficacy to inhibit IL-1beta-induced signaling cascades and iNOS expression would be a better strategy towards lung cancer prevention and/or treatment.     

Tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone induces phosphorylation of mu- and m-calpain in association with increased secretion, cell migration, and invasion

Mounting evidence indicates that cigarette smoking not only promotes tumorigenesis but also may increase the spread of cancer cells in the body. However, the intracellular mechanism(s) by which cigarette smoking promotes metastasis of human lung cancer remains enigmatic. Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is an important component in cigarette smoke and is formed by nitrosation of nicotine. mu- and m-calpain (calpain I and calpain II) are major members of the calpain family, which are ubiquitously expressed in both small cell lung cancer and non-small cell lung cancer cells. Our findings indicated that NNK potently induces phosphorylation of both mu- and m-calpain in association with their activation and increased migration as well as invasion of lung cancer cells. Treatment of cells with PD98059 blocked phosphorylation of m- and mu-calpain and resulted in suppression of NNK-induced cell migration and invasion. p44 MAPK/extracellular signal-regulated kinase 1 (ERK1) and p42 MAPK/ERK2 were activated by NNK, co-localized with mu- and m-calpain in cytoplasm, and directly phosphorylated mu- and m-calpain in vitro. These findings suggest a role for the ERK1/2 kinases as NNK-activated physiological calpain kinases. Specific knock-down of mu- and/or m-calpain expression by RNA interference blocked NNK-stimulated migration and invasion, suggesting that mu- and m-calpain may act as required targets in a NNK-induced metastatic signaling pathway. Furthermore, NNK promotes secretion of active mu- and m-calpain from lung cancer cells through vesicles, which may have the potential to cleave substrates in the extracellular matrix. Thus, NNK-induced cell migration and invasion may occur, at least in part, through a novel mechanism involving phosphorylation of calpains that leads to their activation and secretion, which may contribute to metastasis and/or progression of lung cancer.     

Rab11a通过PI3K/AKT和Ras/MEK/ERK信号通路调节胰腺癌细胞凋亡和侵袭

目的:探究Rab11a在胰腺癌中的表达模式及其对肿瘤生长和转移的影响。方法:通过免疫组织化学法、RT-PCR和Western blot检测60例胰腺癌患者的癌组织和癌旁组织中Rab11a的表达。通过对人胰腺癌细胞系PANC1转染靶向Rab11a的小干扰RNA或过表达Rab11a的pcDNA3.1质粒考察Rab11a对细胞增殖、凋亡、迁移和侵袭的影响。通过Western blot检测PANC1细胞中PI3K、AKT、Ras、MEK、ERK1/2和GSK3β的磷酸化水平。结果:胰腺癌组织中Rab11a的表达水平均高于癌旁组织(P<0.05)。Rab11a的表达水平与TNM分期和淋巴结转移有关(P<0.05)。CCK-8测试和细胞集落形成实验显示,下调Rab11a抑制了PANC1细胞的增殖(P<0.05)。流式细胞术显示,下调Rab11a促进了PANC1细胞的凋亡(P<0.05)。细胞划痕实验显示,下调Rab11a抑制了PANC1细胞的迁移能力(P<0.05)。Matrigel Transwell实验显示,下调Rab11a抑制了PANC1细胞的侵袭能力(P<0.05)。然而,上调Rab11a则促进了PANC1细胞的增殖、迁移和侵袭,并抑制了细胞凋亡(P<0.05)。蛋白质印迹分析显示,下调Rab11a抑制了PANC1细胞中PI3K/AKT和Ras/MEK/ERK信号通路的活化(P<0.05)。此外,应用PI3K/AKT和Ras/MEK/ERK信号通路的选择性抑制剂处理PANC1细胞可阻断Rab11a对细胞增殖的促进作用(P<0.05)。结论:Rab11a的高表达是胰腺癌预后恶化的潜在生物标志物。靶向抑制Rab11a可通过抑制PI3K/AKT和Ras/MEK/ERK信号通路来降低胰腺癌的生长和转移能力。     

Medulloblastoma sensitivity to 17-allylamino-17-demethoxygeldanamycin requires MEK/ERKM

ERBB2 increases the sensitivity of breast cancer cells to the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). This has been attributed to the disruption of ERBB3/ERBB2 heterodimers that maintain a crucial cell survival signal via phosphatidylinositol 3-kinase/AKT. ERBB2 confers a poor clinical outcome in medulloblastoma, the most common malignant pediatric brain tumor. Here, we show that medulloblastoma cell sensitivity to 17-AAG is directly related to ERBB2 expression level. Furthermore, overexpression of exogenous ERBB2 in these cells induces spontaneous homodimerization, further enhancing cell sensitivity to 17-AAG. In contrast to breast cancer cells, this increased sensitivity to 17-AAG does not result from cell dependence on AKT1 activity. Rather, we show that 17-AAG generates a dose- and time-dependent increase in MEK/ERK signaling that is required for the drug to inhibit the proliferation of medulloblastoma cells and that ERBB2 sensitizes medulloblastoma cells to 17-AAG by up-regulating basal MEK/ERK signaling. We further show that down-regulation of MEK1 activity markedly reduces the sensitivity of medulloblastoma, breast, and ovarian cancer cells to 17-AAG, whereas expression of a constitutively active MEK1 potentiates the activity of 17-AAG against these cells. Therefore, intact MEK/ERK signaling may be required for optimal 17AAG activity against a variety of tumor cell types. These data identify a new mechanism by which 17-AAG inhibits the proliferation of cancer cells. Defining the precise mode of action of these agents within specific tumor cell types will be crucial if this class of drugs is to be efficiently developed in the clinic.     

Fucoidan from Seaweed Fucus vesiculosus Inhibits Migration and Invasion of Human Lung Cancer Cell via PI3K-Akt-mTOR Pathways

Background

Recently there has been an increased interest in the pharmacologically active natural products associated with remedies of various kinds of diseases, including cancer. Fucoidan is a polysaccharide derived from brown seaweeds and has long been used as an ingredient in some dietary supplement products. Although fucoidan has been known to have anti-cancer activity, the anti-metastatic effects and its detailed mechanism of actions have been poorly understood. Therefore, the aims of this study were to demonstrate the anti-metastatic functions of fucoidan and its mechanism of action using A549, a highly metastatic human lung cancer cell line.

Methods and Principal Findings

Fucoidan inhibits the growth of A549 cells at the concentration of 400 µg/ml. Fucoidan treatment of non-toxic dose (0–200 µg/ml) exhibits a concentration-dependent inhibitory effect on the invasion and migration of the cancer cell via decreasing its MMP-2 activity. To know the mechanism of these inhibitory effects, Western blotting was performed. Fucoidan treatment down-regulates extracellular signal-related kinase 1 and 2 (ERK1/2) and phosphoinositide 3-kinase (PI3K)–Akt–mammalian target of rapamycin (PI3K-Akt-mTOR) pathways. Furthermore, fucoidan decreases the cytosolic and nuclear levels of Nuclear Factor-kappa B (p65).

Conclusions/Significance

The present study suggests that fucoidan exhibits anti-metastatic effect on A549 lung cancer cells via the down-regulation of ERK1/2 and Akt-mTOR as well as NF-kB signaling pathways. Hence, fucoidan can be considered as a potential therapeutic reagent against the metastasis of invasive human lung cancer cells.     

B-RAF regulation of Rnd3 participates in actin cytoskeletal and focal adhesion organization

The actin cytoskeleton controls multiple cellular functions, including cell morphology, movement, and growth. Accumulating evidence indicates that oncogenic activation of the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 (MEK/ERK1/2) pathway is accompanied by actin cytoskeletal reorganization. However, the signaling events contributing to actin cytoskeleton remodeling mediated by aberrant ERK1/2 activation are largely unknown. Mutant B-RAF is found in a variety of cancers, including melanoma, and it enhances activation of the MEK/ERK1/2 pathway. We show that targeted knockdown of B-RAF with small interfering RNA or pharmacological inhibition of MEK increased actin stress fiber formation and stabilized focal adhesion dynamics in human melanoma cells. These effects were due to stimulation of the Rho/Rho kinase (ROCK)/LIM kinase-2 signaling pathway, cumulating in the inactivation of the actin depolymerizing/severing protein cofilin. The expression of Rnd3, a Rho antagonist, was attenuated after B-RAF knockdown or MEK inhibition, but it was enhanced in melanocytes expressing active B-RAF. Constitutive expression of Rnd3 suppressed the actin cytoskeletal and focal adhesion effects mediated by B-RAF knockdown. Depletion of Rnd3 elevated cofilin phosphorylation and stress fiber formation and reduced cell invasion. Together, our results identify Rnd3 as a regulator of cross talk between the RAF/MEK/ERK and Rho/ROCK signaling pathways, and a key contributor to oncogene-mediated reorganization of the actin cytoskeleton and focal adhesions.