Downregulation of p57kip² promotes cell invasion via LIMK/cofilin pathway in human nasopharyngeal carcinoma cells

ABL1 and Cofilin1 promote T-cell acute lymphoblastic leukemia cell migration

The fusion gene of ABL1 is closely related to tumor proliferation, invasion, and migration. It has been reported recently that ABL1 itself is required for T-cell acute lymphoblastic leukemia (T-ALL) cell migration induced by CXCL12. Further experiments revealed that ABL1 inhibitor Nilotinib inhibited leukemia cell migration induced by CXCL12, indicating the possible application of Nilotinib in T-ALL leukemia treatment. However, the interacting proteins of ABL1 and the specific mechanisms of their involvement in this process need further investigation. In the present study, ABL1 interacting proteins were characterized and their roles in the process of leukemia cell migration induced by CXCL12 were investigated. Co-immunoprecipitation in combination with mass spectrometry analysis identified 333 proteins that interact with ABL1, including Cofilin1. Gene ontology analysis revealed that many of them were enriched in the intracellular organelle or cytoplasm, including nucleic acid binding components, transfectors, or co-transfectors. Kyoto Encyclopedia of Genes and Genomes analysis showed that the top three enriched pathways were translation, glycan biosynthesis, and metabolism, together with human diseases. ABL1 and Cofilin1 were in the same complex. Cofilin1 binds the SH3 domain of ABL1 directly; however, ABL1 is not required for the phosphorylation of Cofilin1. Molecular docking analysis shows that ABL1 interacts with Cofilin1 mainly through hydrogen bonds and ionic interaction between amino acid residues. The mobility of leukemic cells was significantly decreased by Cofilin1 siRNA. These results demonstrate that Cofilin1 is a novel ABL1 binding partner. Furthermore, Cofilin1 participates in the migration of leukemia cells induced by CXCL12. These data indicate that ABL1 and Cofilin1 are possible targets for T-ALL treatment.

Increased intracellular Cl- concentration improves airway epithelial migration by activating the RhoA/ROCK Pathway

In the airway, Cl- is the most abundant anion and is critically involved in transepithelial transport. The correlation of the abnormal expression and activation of chloride channels (CLCs), such as cystic fibrosis transmembrane conductance regulators (CFTRs), anoctamin-1, and CLC-2, with cell migration capability suggests a relationship between defective Cl- transport and epithelial wound repair. However, whether a correlation exists between intracellular Cl- and airway wound repair capability has not been explored thus far, and the underlying mechanisms involved in this relationship are not fully defined. Methods: In this work, the alteration of intracellular chloride concentration ([Cl-]i) was measured by using a chloride-sensitive fluorescent probe (N-[ethoxycarbonylmethyl]-6-methoxyquinolium bromide). Results: We found that clamping with high [Cl-]i and 1 h of treatment with the CLC inhibitor CFTR blocker CFTRinh-172 and chloride intracellular channel inhibitor IAA94 increased intracellular Cl- concentration ([Cl-]i) in airway epithelial cells. This effect improved epithelial cell migration. In addition, increased [Cl-]i in cells promoted F-actin reorganization, decreased cell stiffness, and improved RhoA activation and LIMK1/2 phosphorylation. Treatment with the ROCK inhibitor of Y-27632 and ROCK1 siRNA significantly attenuated the effects of increased [Cl-]i on LIMK1/2 activation and cell migration. In addition, intracellular Ca2+ concentration was unaffected by [Cl-]i clamping buffers and CFTRinh-172 and IAA94. Conclusion: Taken together, these results suggested that Cl- accumulation in airway epithelial cells could activate the RhoA/ROCK/LIMK cascade to induce F-actin reorganization, down-regulate cell stiffness, and improve epithelial migration.

Development of novel therapeutics for the treatment of glaucoma based on actin-binding kinase inhibition – in silico approach

QSAR modeling with computer-aided drug design were used for the in silico development of novel therapeutics for glaucoma treatment.

Fibronectin promotes nasopharyngeal cancer cell motility and proliferation

Nasopharyngeal cancer (NPC) is an Epstein-Barr virus (EBV)-associated carcinoma. Fibronectin is regarded as a prognosticator in NPC and its involvement in cell motility has been reported in EBV infection and viral latent membrane protein 1 (LMP1) overexpression NPC cell lines. However, its malignant potential in NPC cell lines without harbouring the EBV genome has not been investigated. We investigatd and compared among four NPC cell lines, and the results revealed a positive association between fibronectin levels and NPC cell motility as well as proliferation. Studies of antibody neutralization, exogenous addition, overexpression, and RNA interference confirmed a migration role of fibronectin in NPC cells involving integrin α5, Src, Rac1, and Cdc42, implying a mesenchymal-like cell movement. Furthermore, hypoxia-inducible factor-1α (HIF-1α) and transforming growth factor-β1 (TGF-β1) were identified as alternative activators of fibronectin expression and NPC cell migration. Besides cell migration, studies of RNA interference also showed a stimulatory effect of fibronectin in NPC cell proliferation. Mechanistic studies further revealed a subsequent reduction of HIF-1α, TGF-β1, cyclin D1, β-catenin, vimentin, and Slug together with decreased Src and Akt phosphorylation after fibronectin knockdown. Parallel studies in a xenograft tumor mice model further showed that tumor growth correlated well with elevation of circulating fibronectin and activation of the identified intracellular signaling molecules. The results of our study highlight a role of fibronectin in NPC cell motility and proliferation in concerted action with HIF-1α and TGF-β1 possibly through linking molecules Src and Akt. Fibronectin overexpression and autoantibody are known to have potential prognostic value in patients with NPC. Our findings shed light on the biochemical and molecular mechanisms underlying the pathogenic role of fibronectin in this disease.

Cellular localization of the cell cycle inhibitor Cdkn1c controls growth arrest of adult skeletal muscle stem cells

Adult skeletal muscle maintenance and regeneration depend on efficient muscle stem cell (MuSC) functions. The mechanisms coordinating cell cycle with activation, renewal, and differentiation of MuSCs remain poorly understood. Here, we investigated how adult MuSCs are regulated by CDKN1c (p57^kip2), a cyclin-dependent kinase inhibitor, using mouse molecular genetics. In the absence of CDKN1c, skeletal muscle repair is severely impaired after injury. We show that CDKN1c is not expressed in quiescent MuSCs, while being induced in activated and proliferating myoblasts and maintained in differentiating myogenic cells. In agreement, isolated Cdkn1c-deficient primary myoblasts display differentiation defects and increased proliferation. We further show that the subcellular localization of CDKN1c is dynamic; while CDKN1c is initially localized to the cytoplasm of activated/proliferating myoblasts, progressive nuclear translocation leads to growth arrest during differentiation. We propose that CDKN1c activity is restricted to differentiating myoblasts by regulated cyto-nuclear relocalization, coordinating the balance between proliferation and growth arrest.

c-Abl tyrosine kinase regulates neutrophil crawling behavior under fluid shear stress via Rac/PAK/LIMK/cofilin signaling axis

The excessive recruitment and improper activation of polymorphonuclear neutrophils (PMNs) often induces serious injury of host tissues, leading to inflammatory disorders. Therefore, to understand the molecular mechanism on neutrophil recruitment possesses essential pathological and physiological importance. In this study, we found that physiological shear stress induces c-Abl kinase activation in neutrophils, and c-Abl kinase inhibitor impaired neutrophil crawling behavior on ICAM-1. We further identified Vav1 was a downstream effector phosphorylated at Y174 and Y267. Once activated, c-Abl kinase regulated the activity of Vav1, which further affected Rac1/PAK1/LIMK1/cofilin signaling pathway. Here, we demonstrate a novel signaling function and critical role of c-Abl kinase during neutrophil crawling under physiological shear by regulating Vav1. These findings provide a promising treatment strategy for inflammation-related disease by inactivation of c-Abl kinase to restrict neutrophil recruitment.

Degradation of cofilin is regulated by Cbl, AIP4 and Syk resulting in increased migration of LMP2A positive nasopharyngeal carcinoma cells

Expression of cofilin is directly associated with metastatic activity in many tumors. Here, we studied the role of Latent Membrane Protein 2 A (LMP2A) of Epstein-Barr Virus (EBV) in the accumulation of cofilin observed in nasopharyngeal cancer (NPC) tumor cells. We used LMP2A transformed NPC cell lines to analyze cofilin expression. We used mutation analysis, ectopic expression and down-regulation of Cbl, AIP4 and Syk in these cell lines to determine the effect of the LMP2A viral protein on cofilin degradation and its role in the assembly of a cofilin degrading protein complex. The LMP2A of EBV was found to interfer with cofilin degradation in NPC cells by accelerating the proteasomal degradation of Cbl and Syk. In line with this, we found significantly higher cofilin expression in NPC tumor samples as compared to the surrounding epithelial tissues. Cofilin, as an actin severing protein, influences cellular plasticity, and facilitates cellular movement in response to oncogenic stimuli. Thus, under relaxed cellular control, cofilin facilitates tumor cell movement and dissemination. Interference with its degradation may enhance the metastatic potential of NPC cells.

Interplay of N-Cadherin and matrix metalloproteinase 9 enhances human nasopharyngeal carcinoma cell invasion

BACKGROUND

N-cadherin is a trans-membrane adhesion molecule associated with advanced carcinoma progression and poor prognosis. The effect of N-cadherin on matrix metalloproteinase 9 (MMP-9) regulation is implicated in human nasopharyngeal carcinoma (NPC) cell invasion.

METHODS AND RESULTS

Exposure of NPC cells to phorbol-12-myristate-13-acetate (PMA) or macrophage conditioned media (CM) upregulated MMP-9 and N-cadherin cleavage, which resulted in NPC cell invasion. MMP-9 cleaved the extracellular domain of N-cadherin, which was further cleaved by γ-secretase with PMA or macrophage-CM treatment. The extracellular cleavage of N-cadherin was inhibited with treatment with an MMP inhibitor and MMP-9 siRNA, whereas the intracellular cleavage of N-cadherin was inhibited by treatment with a γ-secretase inhibitor (γI), which resulted in enhanced accumulation of N-cadherin C-terminal fragment (CTF1, ~40 kDa). CTF2/N-cad (CTF2), a product of the γ-secretase cleavage of N-cadherin, was released and translocated into the nuclear compartment in PMA-treated cells. Moreover, CTF2 enhanced the effect of PMA-mediated MMP-9 gene expression as assessed by treatment with γI or overexpression with exogenous CTF2. Additionally, siRNA silencing of N-cadherin decreased PMA-mediated MMP-9 expression and cell invasion. The outside-in signaling effect of MMP-9 in macrophage CM- or PMA-treated cell cultures significantly enhanced NPC cell invasion via N-cadherin cleavage.

CONCLUSION

Extracellular and intracellular cleavage of N-cadherin might be involved in elevated MMP-9 expression enhancing tumor cell invasion. Furthermore, N-cadherin-affected tumor progression might be via enhanced MMP-9 signaling in a cross-talk regulatory mechanism. N-cadherin might contribute to the invasive characteristics of carcinoma cells by upregulating MMP-9, thereby leading to increased aggressive metastasis.

The role of cytoplasmic p57 in invasion of hepatocellular carcinoma

Background

Our previous research suggested that p57 downregulation could accelerate the growth and invasion of hepatocellular carcinoma in vitro and in vivo.

Aim

To evaluate the role of cytoplasmic p57 and its regulatory mechanism during hepatocellular carcinoma invasion.

Methods

We examined the subcellular localization of p57 by immunohistochemistry in 45 pairs of cancerous tissues and adjacent non-cancerous tissues. Moreover, we generated stable p57 knockdown hepatoma cell lines to investigate the mechanism of cytoplasmic p57-mediated regulation of invasion by immunoprecipitation, confocal immunofluorescence microscopy and western blot of nuclear and cytoplasmic extracts.

Results

Our results showed that cytoplasmic expression of p57 was reduced in specimens from patients with capsular invasion and metastasis (P < 0.05). Moreover, the level of p-cofilin was decreased in the group lacking cytoplasmic p57 expression (P < 0.05). Co-expression of p57 and p-cofilin was reduced in specimens from patients with tumors at later stages (III + IV), tumors showing capsular invasion and metastatic tumors. We further observed that p57 downregulation decreased the assembly of p57 and LIM domain kinase 1 and its kinase activity, subsequently reducing the level of p-cofilin in the cytoplasm.

Conclusions

Cytoplasmic p57 might be a key regulator in hepatocellular carcinoma invasion via the LIM domain kinase 1/p-cofilin pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-015-0319-x) contains supplementary material, which is available to authorized users.

Targeting CDK11 in osteosarcoma cells using the CRISPR-Cas9 system

Osteosarcoma is the most common type primary malignant tumor of bone. Patients with regional osteosarcoma are routinely treated with surgery and chemotherapy. In addition, many patients with metastatic or recurrent osteosarcoma show poor prognosis with current chemotherapy agents. Therefore, it is important to improve the general condition and the overall survival rate of patients with osteosarcoma by identifying novel therapeutic strategies. Recent studies have revealed that CDK11 is essential in osteosarcoma cell growth and survival by inhibiting CDK11 mRNA expression with RNAi. Here, we apply the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 system, a robust and highly efficient novel genome editing tool, to determine the effect of targeting endogenous CDK11 gene at the DNA level in osteosarcoma cell lines. We show that CDK11 can be efficiently silenced by CRISPR-Cas9. Inhibition of CDK11 is associated with decreased cell proliferation and viability, and induces cell death in osteosarcoma cell lines KHOS and U-2OS. Furthermore, the migration and invasion activities are also markedly reduced by CDK11 knockout. These results demonstrate that CRISPR-Cas9 system is a useful tool for the modification of endogenous CDK11 gene expression, and CRISPR-Cas9 targeted CDK11 knockout may be a promising therapeutic regimen for the treatment of osteosarcoma.

A mechanistic role for the chromatin modulator, NAP1L1, in pancreatic neuroendocrine neoplasm proliferation and metastases

Background

The chromatin remodeler NAP1L1, which is upregulated in small intestinal neuroendocrine neoplasms (NENs), has been implicated in cell cycle progression. As p57^Kip2 (CDKN1C), a negative regulator of proliferation and a tumor suppressor, is controlled by members of the NAP1 family, we tested the hypothesis that NAP1L1 may have a mechanistic role in regulating pancreatic NEN proliferation through regulation of p57^Kip2.

Results

NAP1L1 silencing (siRNA and shRNA/lipofectamine approach) decreased proliferation through inhibition of mechanistic (mammalian) target of rapamycin pathway proteins and their phosphorylation (p < 0.05) in the pancreatic neuroendocrine neoplasm cell line BON in vitro (p < 0.0001) and resulted in significantly smaller (p < 0.05) and lighter (p < 0.05) tumors in the orthotopic pancreatic NEN mouse model. Methylation of the p57^Kip2 promoter was decreased by NAP1L1 silencing (p < 0.05), and expression of p57^Kip2 (transcript and protein) was upregulated. For methylation of the p57^Kip2 promoter, NAP1L1 bound directly to the promoter (−164 to +21, chromatin immunoprecipitation). In 43 pancreatic NEN samples (38 primaries and 5 metastasis), NAP1L1 was over-expressed in metastasis (p < 0.001), expression which was inversely correlated with p57^Kip2 (p < 0.01) on mRNA and protein levels. Menin was not differentially expressed.

Conclusion

NAP1L1 is over-expressed in pancreatic neuroendocrine neoplasm metastases and epigenetically promotes cell proliferation through regulation of p57^Kip2 promoter methylation.

Theoretical study on the interaction of pyrrolopyrimidine derivatives as LIMK2 inhibitors: insight into structure-based inhibitor design

LIM kinases (LIMKs), downstream of Rho-associated protein kinases (ROCKs) and p21-activated protein kinases (PAKs), are shown to be promising targets for the treatment of cancers. In this study, the inhibition mechanism of 41 pyrrolopyrimidine derivatives as LIMK2 inhibitors was explored through a series of theoretical approaches. First, a model of LIMK2 was generated through molecular homology modeling, and the studied inhibitors were docked into the binding active site of LIMK2 by the docking protocol, taking into consideration the flexibility of the protein. The binding poses predicted by molecular docking for 17 selected inhibitors with different bioactivities complexed with LIMK2 underwent molecular dynamics (MD) simulations, and the binding free energies for the complexes were predicted by using the molecular mechanics/generalized born surface area (MM/GBSA) method. The predicted binding free energies correlated well with the experimental bioactivities (r(2) = 0.63 or 0.62). Next, the free energy decomposition analysis was utilized to highlight the following key structural features related to biological activity: (1) the important H-bond between Ile408 and pyrrolopyrimidine, (2) the H-bonds between the inhibitors and Asp469 and Gly471 which maintain the stability of the DFG-out conformation, and (3) the hydrophobic interactions between the inhibitors and several key residues (Leu337, Phe342, Ala345, Val358, Lys360, Leu389, Ile408, Leu458 and Leu472). Finally, a variety of LIMK2 inhibitors with a pyrrolopyrimidine scaffold were designed, some of which showed improved potency according to the predictions. Our studies suggest that the use of molecular docking with MD simulations and free energy calculations could be a powerful tool for understanding the binding mechanism of LIMK2 inhibitors and for the design of more potent LIMK2 inhibitors.

Leptin activates RhoA/ROCK pathway to induce cytoskeleton remodeling in nucleus pulposus cells

Hyperleptinemia is implicated in obesity-associated lumbar disc degeneration. Nevertheless, the effect of leptin on the intracellular signaling of nucleus pulposus cells is not clear. The current study sought to delineate the possible involvement of the RhoA/ROCK pathway in leptin-mediated cytoskeleton reorganization in nucleus pulposus cells. Nucleus pulposus cells isolated from scoliosis patients were treated with 10 ng/mL of leptin. Fluorescent resonance energy transfer analysis was used to determine the activation of RhoA signaling in nucleus pulposus cells. The protein expression of LIMK1 and cofilin-2 were analyzed by western blot analysis. F-actin cytoskeletal reorganization was assessed by rhodamine-conjugated phalloidin immunoprecipitation. Leptin induced F-actin reorganization and stress fiber formation in nucleus pulposus cells, accompanied by localized RhoA activation and phosphorylation of LIMK1 and cofilin. The RhoA inhibitor C3 exoenzyme or the ROCK inhibitor Y-27632 potently attenuated the effects of leptin on F-actin reorganization and stress fiber formation. Both inhibitors also prevented leptin-induced phosphorylation of LIMK1 and cofilin-2. Our study demonstrated that leptin activated the RhoA/ROCK/LIMK/cofilin-2 cascade to induce cytoskeleton reorganization in nucleus pulposus cells. These findings may provide novel insights into the pathogenic mechanism of obesity-associated lumbar disc degeneration.

Exogenous Reelin modifies the migratory behavior of neurons depending on cortical location

Malformations of cortical development can arise when projection neurons generated in the germinal zones fail to migrate properly into the cortical plate. This process is critically dependent on the Reelin glycoprotein, which when absent leads to an inversion of cortical layers and blurring of borders. Reelin has other functions including supporting neuron migration and maintaining their trajectories; however, the precise role on glial fiber-dependent or -independent migration of neurons remains controversial. In this study, we wish to test the hypothesis that migrating cortical neurons at different levels of the cortical wall have differential responses to Reelin. We exposed neurons migrating across the cortical wall to exogenous Reelin and monitored their migratory behavior using time-lapse imaging. Our results show that, in the germinal zones, exogenous Reelin retarded neuron migration and altered their trajectories. This behavior is in contrast to the response of neurons located in the intermediate zone (IZ), possibly because Reelin receptors are not expressed in this zone. In the reeler cortex, Reelin receptors are expressed in the IZ and exposure to exogenous Reelin was able to rescue the migratory defect. These studies demonstrate that migrating neurons have nonequivalent responses to Reelin depending on their location within the cortical wall.

Integrin-binding protein nischarin interacts with tumor suppressor liver kinase B1 (LKB1) to regulate cell migration of breast epithelial cells

Biallelic inactivation of LKB1, a serine/threonine kinase, has been detected in 30% of lung adenocarcinomas, and inhibition of breast tumor growth has been demonstrated. We have identified the tumor suppressor, Nischarin, as a novel binding partner of LKB1. Our mapping analysis shows that the N terminus of Nischarin interacts with amino acids 44-436 of LKB1. Time lapse microscopy and Transwell migration data show that the absence of both Nischarin and LKB1 from an invasive breast cancer cell line (MDA-MB-231) enhances migration as measured by increased distance and speed of migrating cells. Our data suggest that this is a result of elevated PAK1 and LIMK1 phosphorylation. Moreover, the absence of Nischarin and LKB1 increased tumor growth in vivo. Consistent with this, the percentage of S phase cells was increased, as demonstrated by flow cytometry and enhanced cyclin D1. The absence of Nischarin and LKB1 also led to a dramatic increase in the formation of lung metastases. Our studies, for the first time, demonstrate functional interaction between LKB1 and Nischarin to inhibit cell migration and breast tumor progression. Mechanistically, we show that these two proteins together regulate PAK-LIMK-Cofilin and cyclin D1/CDK4 pathways.

Downregulation of p57 accelerates the growth and invasion of hepatocellular carcinoma

p57 is a multifunctional protein involved in the regulation of tumor formation and development; however, the biological role of p57 in the pathogenesis of hepatocellular carcinoma (HCC) is poorly understood. To explore the role of p57 in the development of HCC, we examined p57 messenger RNA (mRNA) and protein levels in HCC tissues and adjacent non-cancerous tissues by immunohistochemistry, real-time polymerase chain reaction and western blot analysis. Moreover, we generated stable p57 knockdown HCC cell lines to investigate the impact of p57 downregulation on the growth and invasion of HCC in vitro and in vivo. Our results showed that p57 mRNA and protein levels were significantly decreased in human HCC tissues. In addition, this reduction in p57 expression was associated with increased tumor size, more advanced TNM stages, the presence of capsule invasion and extrahepatic metastasis and decreased overall survival time. In human HCC cell lines, p57 downregulation increased the expression of cyclin D1 and CDK2 and enhanced the activities of CDK4/cyclin D1 and CDK2/cyclin E complexes, resulting in increased cellular proliferation and growth of xenografts. Furthermore, p57 downregulation accelerated the invasion of HCC cells in vitro and in vivo by controlling the activity of LIMK1. In conclusion, the downregulation of p57 accelerates the growth and invasion of HCC, indicating that p57 is an important tumor suppressor in HCC. Based on these findings, p57 may be a potential target for HCC prevention and therapy.