PKCε-mediated c-Met endosomal processing directs fluctuant c-Met-JNK-paxillin signaling for tumor progression of HepG2

Bioactive Products Targeting C-Met As Potential Antitumour Drugs

Mesenchymal‒epithelial transition factor (c-Met), a receptortyrosine kinase (RTK), plays a vital role in cell proliferation, migration and invasion, and tumour metastasis.

OBJECTIVE

With increasing duration of treatment, many tumours gradually develop drug resistance. Therefore, novel antitumour drugs need to be developed to treat patients with tumours. Targeting c-met inhibitors may be an effective treatment strategy.

METHODS

Scientific databases such as ScienceDirect, PubMed, the Wiley Online Library, and Social Sciences Citation Index were used to collect information. All the relevant literature was reviewed, and the available literature was screened. The upstream and downstream pathways of c-Met and their relevance to antitumour effects were searched based on the articles' title, abstract, and full text. The c-Met-targeting drugs with antitumour effects are summarized below. A "citation within a citation" or snowballing approach was used in this screening process to identify additional papers that may have been missed in the initial literature screening process. High-quality studies published in peer-reviewed journals were summarized and prioritized for citation in the review.

RESULTS

In recent years, research on small-molecule targeted drugs has developed rapidly. Many results have also been achieved in the synthesis and isolation of c-Met inhibitors from natural compounds and traditional Chinese medicines.

CONCLUSION

This article summarizes the developments in anti-c-Met drugs, which are synthesized and isolated from natural compounds and traditional Chinese medicine (TCM). This study provides primary resources for the development of c-Met inhibitors.

Unlocking c-MET: A comprehensive journey into targeted therapies for breast cancer

Breast cancer is the most common malignancy among women, posing a formidable health challenge worldwide. In this complex landscape, the c-MET (cellular-mesenchymal epithelial transition factor) receptor tyrosine kinase (RTK), also recognized as the hepatocyte growth factor (HGF) receptor (HGFR), emerges as a prominent protagonist, displaying overexpression in nearly 50% of breast cancer cases. Activation of c-MET by its ligand, HGF, secreted by neighboring mesenchymal cells, contributes to a cascade of tumorigenic processes, including cell proliferation, metastasis, angiogenesis, and immunosuppression. While c-MET inhibitors such as crizotinib, capmatinib, tepotinib and cabozantinib have garnered FDA approval for non-small cell lung cancer (NSCLC), their potential within breast cancer therapy is still undetermined. This comprehensive review embarks on a journey through structural biology, multifaceted functions, and intricate signaling pathways orchestrated by c-MET across cancer types. Furthermore, we highlight the pivotal role of c-MET-targeted therapies in breast cancer, offering a clinical perspective on this promising avenue of intervention. In this pursuit, we strive to unravel the potential of c-MET as a beacon of hope in the fight against breast cancer, unveiling new horizons for therapeutic innovation.

Insulin-like Growth Factor 2-Tagged Aptamer Chimeras (ITACs) Modular Assembly for Targeted and Efficient Degradation of Two Membrane Proteins

Overexpression of pathogenic membrane proteins drives abnormal proliferation and invasion of tumor cells. Various strategies to durably knockdown membrane proteins with heterobifunctional degraders have been successfully developed, including LYTAC, KineTAC, and AbTAC. However, challenges including complicated synthetic procedures and the inability to simultaneously degrade multiple pathogenic proteins still exist. Herein, we developed insulin-like growth factor 2 (IGF2)-tagged aptamer chimeras (ITACs) that link the cell-surface lysosome-targeting receptor IGF2R and membrane proteins of interest (POIs) based on specific recognition of aptamers to the POIs and high-affinity binding of IGF2 to IGF2R. We demonstrated that ITACs exhibit robust degradation efficiency of various membrane proteins in multiple cell lines. Furthermore, systematic studies revealed that a moderate cell-surface IGF2R level is responsible for the excellent degradation performance of ITACs. Importantly, we further established a modular assembly strategy that allows assembly of one IGF2 with two aptamers with precise stoichiometry (dITACs), enabling cooperative and simultaneous degradation of two membrane proteins. This work provides an efficient and facile target membrane protein degradation platform and will shed light on the treatment of diseases related to the overexpression of membrane proteins.

Protein kinase C epsilon promotes de novo lipogenesis and tumor growth in prostate cancer cells by regulating the phosphorylation and nuclear translocation of pyruvate kinase isoform M2

Protein kinase C epsilon (PKCε) belongs to a family of serine/threonine kinases that control cell proliferation, differentiation and survival. Aberrant PKCε activation and overexpression is a frequent feature of numerous cancers. However, its role in regulation of lipid metabolism in cancer cells remains elusive. Here we report a novel function of PKCε in regulating of prostate cancer cell proliferation by modulation of PKM2-mediated de novo lipogenesis. We show that PKCε promotes de novo lipogenesis and tumor cell proliferation via upregulation of lipogenic enzymes and lipid contents in prostate cancer cells. Mechanistically, PKCε interacts with NABD (1-388) domain of C-terminal deletion on pyruvate kinase isoform M2 (PKM2) and enhances the Tyr105 phosphorylation of PKM2, leading to its nuclear localization. Moreover, forced expression of mutant Tyr105 (Y105F) or PKM2 inhibition suppressed de novo lipogenesis and cell proliferation induced by overexpression of PKCε in prostate cancer cells. In a murine tumor model, inhibitor of PKM2 antagonizes lipogenic enzymes expression and prostate cancer growth induced by overexpression of PKCε in vivo. These data indicate that PKCε is a critical regulator of de novo lipogenesis, which may represent a potential therapeutic target for the treatment of prostate cancer.

Hepatitis B virus compartmentalization and single-cell differentiation in hepatocellular carcinoma

Single-cell RNA-Seq unravels heterogeneity and compartmentalization of both hepatitis B virus and cancer identifying new candidate pathways for viral hepatocarcinogenesis.

Chronic hepatitis B virus (HBV) infection is a major cause of hepatocellular carcinoma (HCC) world-wide. The molecular mechanisms of viral hepatocarcinogenesis are still partially understood. Here, we applied two complementary single-cell RNA-sequencing protocols to investigate HBV–HCC host cell interactions at the single cell level of patient-derived HCC. Computational analyses revealed a marked HCC heterogeneity with a robust and significant correlation between HBV reads and cancer cell differentiation. Viral reads significantly correlated with the expression of HBV-dependency factors such as HLF in different tumor compartments. Analyses of virus-induced host responses identified previously undiscovered pathways mediating viral carcinogenesis, such as E2F- and MYC targets as well as adipogenesis. Mapping of fused HBV–host cell transcripts allowed the characterization of integration sites in individual cancer cells. Collectively, single-cell RNA-Seq unravels heterogeneity and compartmentalization of both, virus and cancer identifying new candidate pathways for viral hepatocarcinogenesis. The perturbation of pro-carcinogenic gene expression even at low HBV levels highlights the need of HBV cure to eliminate HCC risk.

Structural and Functional Insight Into the Glycosylation Impact Upon the HGF/c-Met Signaling Pathway

Upon interactions with its specific ligand hepatocyte growth factor (HGF), the c-Met signal is relayed to series of downstream pathways, exerting essential biological roles. Dysregulation of the HGF-c-Met signaling pathway has been implicated in the onset, progression and metastasis of various cancers, making the HGF-c-Met axis a promising therapeutic target. Both c-Met and HGF undergo glycosylation, which appears to be biologically relevant to their function and structural integrity. Different types of glycoconjugates in the local cellular environment can also regulate HGF/c-Met signaling by distinct mechanisms. However, detailed knowledge pertaining to the glycosylation machinery of the HGF-c-Met axis as well as its potential applications in oncology research is yet to be established. This mini review highlights the significance of the HGF-c-Met signaling pathway in physiological and pathological context, and discusses the molecular mechanisms by which affect the glycosylation of the HGF-c-Met axis. Owing to the crucial role played by glycosylation in the regulation of HGF/c-Met activity, better understanding of this less exploited field may contribute to the development of novel therapeutics targeting glycoepitopes.

The Function of the HGF/c-Met Axis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, leading to a large global cancer burden. Hepatocyte growth factor (HGF) and its high-affinity receptor, mesenchymal epithelial transition factor (c-Met), are closely related to the onset, progression, and metastasis of multiple tumors. The HGF/c-Met axis is involved in cell proliferation, movement, differentiation, invasion, angiogenesis, and apoptosis by activating multiple downstream signaling pathways. In this review, we focus on the function of the HGF/c-Met axis in HCC. The HGF/c-Met axis promotes the onset, proliferation, invasion, and metastasis of HCC. Moreover, it can serve as a biomarker for diagnosis and prognosis, as well as a therapeutic target for HCC. In addition, it is closely related to drug resistance during HCC treatment.

Hydrogen peroxide inducible clone-5 sustains NADPH oxidase-dependent reactive oxygen species-c-jun N-terminal kinase signaling in hepatocellular carcinoma

Target therapy aiming at critical molecules within the metastatic signal pathways is essential for prevention of hepatocellular carcinoma (HCC) progression. Hic-5 (hydrogen peroxide inducible clone-5) which belongs to the paxillin superfamily, can be stimulated by a lot of metastatic factors, such as transforming growth factor (TGF-β), hepatocyte growth factor (HGF), and reactive oxygen species (ROS). Previous studies implicated Hic-5 cross-talks with the ROS-c-jun N-terminal kinase (JNK) signal cascade in a positive feedback manner. In this report, we addressed this issue in a comprehensive manner. By RNA interference and ectopic Hic-5 expression, we demonstrated Hic-5 was essential for activation of NADPH oxidase and ROS generation leading to activation of downstream JNK and c-jun transcription factor. This was initiated by interaction of Hic-5 with the regulator and adaptor of NADPH oxidase, Rac1 and Traf4, respectively, which may further phosphorylate the nonreceptor tyrosine kinase Pyk2 at Tyr881. On the other hand, promoter activity assay coupled with deletion mapping and site directed mutagenesis strategies demonstrated the distal c-jun and AP4 putative binding regions (943–1126 bp upstream of translational start site) were required for transcriptional activation of Hic-5. Thus Hic-5 was both downstream and upstream of NADPH oxidase-ROS-JNK-c-jun cascade. This signal circuit was essential for regulating the expression of epithelial mesenchymal transition (EMT) factors, such as Snail, Zeb1, E-cadherin, and matrix metalloproteinase 9, involved in HCC cell migration and metastasis. Due to the limited expression of Hic-5 in normal tissue, it can be a promising therapeutic target for preventing HCC metastasis.

PIM1 kinase promotes cell proliferation, metastasis and tumor growth of lung adenocarcinoma by potentiating the c-MET signaling pathway

The proto-oncogene PIM1 plays essential roles in proliferation, survival, metastasis and drug resistance in hematopoietic and solid tumors. Although PIM1 has been shown to be associated with lymph node metastasis and poor prognosis in non-small cell lung cancer, its underlying molecular mechanisms in this context are still unclear. Here we show that PIM1 is frequently overexpressed in lung adenocarcinomas, and its expression level is associated with c-MET expression and poor clinical outcome. We further demonstrate that PIM1 may regulate c-MET expression via phosphorylation of eukaryotic translation initiation factor 4B (eIF4B) on S406. Depletion of PIM1 decreased cell proliferation, migration, invasion and colony formation in vitro, as well as reduced tumor growth in vivo. And these effects were partially abrogated by restoring of c-MET expression. Our study implicates a promising therapeutic approach in lung adenocarcinoma patients with PIM1 and c-MET overexpression.

Crosstalk of protein kinase C ε with Smad2/3 promotes tumor cell proliferation in prostate cancer cells by enhancing aerobic glycolysis

Protein kinase C ε (PKCε) has emerged as an oncogenic protein kinase and plays important roles in cancer cell survival, proliferation, and invasion. It is, however, still unknown whether PKCε affects cell proliferation via glucose metabolism in cancer cells. Here we report a novel function of PKCε that provides growth advantages for cancer cells by enhancing tumor cells glycolysis. We found that either PKCε or Smad2/3 promoted aerobic glycolysis, expression of the glycolytic genes encoding HIF-1α, HKII, PFKP and MCT4, and tumor cell proliferation, while overexpression of PKCε or Smad3 enhanced aerobic glycolysis and cell proliferation in a protein kinase D- or TGF-β-independent manner in PC-3M and DU145 prostate cancer cells. The effects of PKCε silencing were reversed by ectopic expression of Smad3. PKCε or Smad3 ectopic expression-induced increase in cell growth was antagonized by inhibition of lactate transportation. Furthermore, interaction of endogenous PKCε with Smad2/3 was primarily responsible for phosphorylation of Ser213 in the Samd3 linker region, and resulted in Smad3 binding to the promoter of the glycolytic genes, thereby promoting cell proliferation. Forced expression of mutant Smad3 (S213A) attenuated PKCε-stimulated protein overexpression of the glycolytic genes. Thus, our results demonstrate a novel PKCε function that promotes cell growth in prostate cancer cells by increasing aerobic glycolysis through crosstalk between PKCε and Smad2/3.

Strong enhancement by IGF1-R antagonists of hepatocellular carcinoma cell migration inhibition by Sorafenib and/or vitamin K1

PURPOSE

Emerging evidence indicates that combining Sorafenib with vitamin K1 (VK1) may result in a synergistic inhibition of hepatocellular carcinoma (HCC) cell migration and proliferation. Despite this synergy, its benefits may be limited due to drug resistance resulting from cross-talk with the tumor microenvironment. Insulin-like growth factor-1 (IGF1) signaling acts as an important modulator of HCC cell growth, motility and drug resistance. Therefore, we aimed to explore the effects of Sorafenib in combination with VK1 and/or IGF1-R antagonists on HCC cells.

METHODS

Scratch wound migration assays were performed to assess the motility of HCC-derived PLC/PRF/5, HLF and Hep3B cells. The synergistic, additive or antagonistic effects of Sorafenib, VK1 and IGF1-R antagonists on HCC cell motility were assessed using CompuSyn software. The effects mediated by these various compounds on HCC cytoskeleton organization were evaluated using DyLight 554 Phalloidin staining. Proliferation and migration-associated signaling pathways were analyzed in PLC/PRF/5 cells using Erk1/2 and Akt activation kits and Western blotting (Mek, JNK, Akt, Paxillin and p38), respectively.

RESULTS

The effects of the IGF1-R antagonists GSK1838705A and OSI-906 on HCC cell migration inhibition after Sorafenib and/or VK1 administration, individually or in combination, were evaluated. We found a synergistic effect in PLC/PRF/5, HLF and Hep3B cells for combinations of fixed doses of GSK1838705A or OSI-906 together with different doses of Sorafenib and/or VK1. The levels of synergy were found to be stronger at higher Sorafenib and/or VK1 concentrations and lower or absent at lower concentrations, with some variation among the different cell lines tested. In addition, we found that in PLC/PRF/5 and HLF cells IGF1-R blockage strongly enhanced the reduction and redistribution of F-actin induced by Sorafenib and/or VK1 through alterations in the phosphorylation levels of some of the principal proteins involved in the MAPK signaling cascade, which is essential for cell migration.

CONCLUSIONS

Our results indicate that modulation of the efficacy of Sorafenib through combinations with VK1 and/or IGF1-R antagonists results in synergistic inhibition of HCC cell migration.

The MBNL3 splicing factor promotes hepatocellular carcinoma by increasing PXN expression through the alternative splicing of lncRNA-PXN-AS1

Understanding the roles of splicing factors and splicing events during tumorigenesis would open new avenues for targeted therapies. Here we identify an oncofetal splicing factor, MBNL3, which promotes tumorigenesis and indicates poor prognosis of hepatocellular carcinoma patients. MBNL3 knockdown almost completely abolishes hepatocellular carcinoma tumorigenesis. Transcriptomic analysis revealed that MBNL3 induces lncRNA-PXN-AS1 exon 4 inclusion. The transcript lacking exon 4 binds to coding sequences of PXN mRNA, causes dissociation of translation elongation factors from PXN mRNA, and thereby inhibits PXN mRNA translation. In contrast, the transcript containing exon 4 preferentially binds to the 3' untranslated region of PXN mRNA, protects PXN mRNA from microRNA-24-AGO2 complex-induced degradation, and thereby increases PXN expression. Through inducing exon 4 inclusion, MBNL3 upregulates PXN, which mediates the pro-tumorigenic roles of MBNL3. Collectively, these data demonstrate detailed mechanistic links between an oncofetal splicing factor, a splicing event and tumorigenesis, and establish splicing factors and splicing events as potential therapeutic targets.

The Therapeutic Targeting of HGF/c-Met Signaling in Hepatocellular Carcinoma: Alternative Approaches

The poor prognosis of hepatocellular carcinoma (HCC), one of the most devastating cancers worldwide, is due to frequent recurrence and metastasis. Among the metastatic factors in the tumor microenvironment, hepatocyte growth factor (HGF) has been well known to play critical roles in tumor progression, including HCC. Therefore, c-Met is now regarded as the most promising therapeutic target for the treatment of HCC. However, there are still concerns about resistance and the side effects of using conventional inhibitors of c-Met, such as tyrosine kinase inhibitors. Recently, many alternative strategies of c-Met targeting have been emerging. These include targeting the downstream effectors of c-Met, such as hydrogen peroxide-inducible clone 5 (Hic-5), to block the reactive oxygen species (ROS)-mediated signaling for HCC progression. Also, inhibition of endosomal regulators, such as PKCε and GGA3, may perturb the c-Met endosomal signaling for HCC cell migration. On the other hand, many herbal antagonists of c-Met-dependent signaling, such as saponin, resveratrol, and LZ-8, were identified. Taken together, it can be anticipated that more effective and safer c-Met targeting strategies for preventing HCC progression can be established in the future.

Paxillin: a crossroad in pathological cell migration

Paxilllin is a multifunctional and multidomain focal adhesion adapter protein which serves an important scaffolding role at focal adhesions by recruiting structural and signaling molecules involved in cell movement and migration, when phosphorylated on specific Tyr and Ser residues. Upon integrin engagement with extracellular matrix, paxillin is phosphorylated at Tyr31, Tyr118, Ser188, and Ser190, activating numerous signaling cascades which promote cell migration, indicating that the regulation of adhesion dynamics is under the control of a complex display of signaling mechanisms. Among them, paxillin disassembly from focal adhesions induced by extracellular regulated kinase (ERK)-mediated phosphorylation of serines 106, 231, and 290 as well as the binding of the phosphatase PEST to paxillin have been shown to play a key role in cell migration. Paxillin also coordinates the spatiotemporal activation of signaling molecules, including Cdc42, Rac1, and RhoA GTPases, by recruiting GEFs, GAPs, and GITs to focal adhesions. As a major participant in the regulation of cell movement, paxillin plays distinct roles in specific tissues and developmental stages and is involved in immune response, epithelial morphogenesis, and embryonic development. Importantly, paxillin is also an essential player in pathological conditions including oxidative stress, inflammation, endothelial cell barrier dysfunction, and cancer development and metastasis.

Alterations in transcription and protein expressions of HCC-related genes in HepG2 cells caused by microcystin-LR

Microcystin-LR (MC-LR) is the most common and toxic hepatotoxin and it could induce human hepatitis and hepatocellular carcinoma (HCC) via the route of drinking water. The aim of the present study was to determine the expressions of oncogenes c-fos, c-jun, c-myc, c-met, and N-ras and tumor suppressor gene PTEN in HepG2 cells following MC-LR-exposure to understand the possible mechanism of MC-LR-related human primary liver cancer. The results of qPCR and Western blotting showed that MC-LR-exposure at non- or sub-cytotoxic concentrations promoted the expressions of oncogenes c-fos, c-jun, c-myc, c-met, and N-ras while suppressed tumor-suppressor gene PTEN in HepG2 cells at both transcription and protein levels. This result suggests that HCC-related genes may be involved in human hepatitis and primary liver cancer caused by MC-LR. The work might be useful for evaluating the human health risk resulted from the long-term of MC-LR-exposure at low dose via drinking water route.

Hydrogen peroxide inducible clone-5 mediates reactive oxygen species signaling for hepatocellular carcinoma progression

One of the signaling components involved in hepatocellular carcinoma (HCC) progression is the focal adhesion adaptor paxillin. Hydrogen peroxide inducible clone-5 (Hic-5), one of the paralogs of paxillin, exhibits many biological functions distinct from paxillin, but may cooperate with paxillin to trigger tumor progression. Screening of Hic-5 in 145 surgical HCCs demonstrated overexpression of Hic-5 correlated well with intra- and extra-hepatic metastasis. Hic-5 highly expressed in the patient derived HCCs with high motility such as HCC329 and HCC353 but not in the HCCs with low motility such as HCC340. Blockade of Hic-5 expression prevented constitutive migration of HCC329 and HCC353 and HGF-induced cell migration of HCC340. HCC329Hic-5(−), HCC353Hic-5(−), HCC372Hic-5(−), the HCCs stably depleted of Hic-5, exhibited reduced motility compared with each HCC expressing Scramble shRNA. Moreover, intra/extrahepatic metastasis of HCC329Hic-5(−) in SCID mice greatly decreased compared with HCC329Scramble. On the other hand, ectopic Hic-5 expression in HCC340 promoted its progression. Constitutive and HGF-induced Hic-5 expression in HCCs were suppressed by the reactive oxygen species (ROS) scavengers catalase and dithiotheritol and c-Jun N-terminal kinase (JNK) inhibitor SP600125. On the contrary, depletion of Hic-5 blocked constitutive and HGF-induced ROS generation and JNK phosphorylation in HCCs. Also, ectopic expression of Hic-5 enhanced ROS generation and JNK phosphorylation. These highlighted that Hic-5 plays a central role in the positive feedback ROS-JNK signal cascade. Finally, the Chinese herbal derived anti-HCC peptide LZ-8 suppressed constitutive Hic-5 expression and JNK phosphorylation. In conclusion, Hic-5 mediates ROS-JNK signaling and may serve as a therapeutic target for prevention of HCC progression.

Regulation of the MET oncogene: molecular mechanisms

The MET oncogene is a predictive biomarker and an attractive therapeutic target for various cancers. Its expression is regulated at multiple layers via various mechanisms. It is subject to epigenetic modifications, i.e. DNA methylation and histone acetylation. Hypomethylation and acetylation of the MET gene have been associated with its high expression in some cancers. Multiple transcription factors including Sp1 and Ets-1 govern its transcription. After its transcription, METmRNA is spliced into multiple species in the nucleus before being transported to the cytoplasm where its translation is modulated by at least 30 microRNAs and translation initiation factors, e.g. eIF4E and eIF4B. METmRNA produces a single chain pro-Met protein of 170 kDa which is cleaved into α and β chains. These two chains are bound together through disulfide bonds to form a heterodimer which undergoes either N-linked or O-linked glycosylation in the Golgi apparatus before it is properly localized in the membrane. Upon interactions with its ligand, i.e. hepatocyte growth factor (HGF), the activity of Met kinase is boosted through various phosphorylation mechanisms and the Met signal is relayed to downstream pathways. The phosphorylated Met is then internalized for subsequent degradation or recycle via proteasome, lysosome or endosome pathways. Moreover, the Met expression is subject to autoregulation and activation by other EGFRs and G-protein coupled receptors. Since deregulation of the MET gene leads to cancer and other pathological conditions, a better understanding of the MET regulation is critical for Met-targeted therapeutics.

Spatio-Temporal Parameters of Endosomal Signaling in Cancer: Implications for New Treatment Options

The endo/lysosomal system in cells provides membranous platforms to assemble specific signaling complexes and to terminate signal transduction, thus, is essential for physiological signaling. Endocytic organelles can significantly extend signaling of activated cell surface receptors, and may additionally provide distinct locations for the generation of specific signaling outputs. Failures of regulation at different levels of endocytosis, recycling, degradation as well as aberrations in specific endo/lysosomal signaling pathways, such as mTORC1, might lead to different diseases including cancer. Therefore, a better understanding of spatio‐temporal compartmentalization of sub‐cellular signaling might provide an opportunity to interfere with aberrant signal transduction in pathological processes by novel combinatorial therapeutic approaches. J. Cell. Biochem. 117: 836–843, 2016. © 2015 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals Inc.

Augmentation of invadopodia formation in temozolomide-resistant or adopted glioma is regulated by c-Jun terminal kinase-paxillin axis

Temozolomide (TMZ) is one of the few effective anticancer agents against gliomas. However, acquisition of TMZ resistance or adaptation by gliomas is currently a crucial problem, especially increased invasiveness which is critical for the determination of clinical prognosis. This study investigated the molecular regulatory mechanisms of TMZ resistance in gliomas involved in invasiveness, particularly invadopodia formation, a molecular complex formed at the invasive front to cause extracellular matrix degradation during cellular local invasion. The TMZ-resistant clone of the U343 MG human glioma cell line (U343-R cells) was established. U343-R cells demonstrated higher invadopodia formation compared with U343 cells without TMZ resistance (U343-Con cells). Immunoblot analysis of DNA damage-related mitogen-activated protein kinase signals found increased phosphorylation of c-Jun terminal kinase (JNK) and higher activation of its downstream signaling in U343-R cells compared with U343-Con cells. Treatment of U343-R cells with specific inhibitors of JNK or siRNA targeting JNK suppressed up-regulation of invadopodia formation. In addition, paxillin, one of the known JNK effectors which is phosphorylated and affects cell migration, was phosphorylated at serine 178 in JNK activity-dependent manner. Expression of paxillin with mutation of the serine 178 phosphorylation site in U343-R cells blocked invadopodia formation. The present findings suggest that increased formation of invadopodia in U343-R cells is mediated by hyperactivation of JNK-paxillin signaling, and both JNK and paxillin might become targets of novel therapies against TMZ-resistant gliomas.