Cytoskeleton alterations in melanoma: aberrant expression of cortactin, an actin-binding adapter protein, correlates with melanocytic tumor progression

Copper nitroprusside analogue nanoparticles against melanoma: detailed in vitro and in vivo investigation

Melanoma is the most invasive and lethal form of skin cancer that arises from the malignant transformation of specialized pigment-producing cell melanocytes. Nanomedicine represents an important prospect to mitigate the difficulties and provide significant benefits to cure melanoma. In the present study, we investigated in vitro and in vivo therapeutic efficacies of copper nitroprusside analogue nanoparticles (abbreviated as CuNPANP) towards melanoma. Initially, in vitro anti-cancer activities of CuNPANP towards melanoma cells (B16F10) were evaluated by several experiments such as [methyl-3H]-thymidine incorporation assay, cell cycle and apoptosis assays using FACS analysis, ROS generation using DCFDA, DHE and DAF2A reagents, internalization of nanoparticles through ICP-OES analysis, co-localization of the nanoparticles using confocal microscopy, JC-1 staining to investigate the mitochondrial membrane potential (MMP) and immunofluorescence studies to analyze the expressions of cytochrome-c, Ki-67, E-cadherin as well as phalloidin staining to analyze the cytoskeletal integrity. Further, the in vivo therapeutic effectiveness of the nanoparticles was established towards malignant melanoma by inoculating B16F10 cells in the dorsal right abdomen of C57BL/6J mice. The intraperitoneal administration of CuNPANP inhibited tumor growth and increased the survivability of melanoma mice. The in vivo immunofluorescence studies (Ki-67, CD-31, and E-cadherin) and TUNEL assay further support the anti-cancer and apoptosis-inducing potential of CuNPANP, respectively. Finally, various signaling pathways and molecular mechanisms involved in anti-cancer activities were further evaluated by Western blot analysis. The results altogether indicated the potential use of copper-based nanomedicines for the treatment of malignant melanoma.

Requirement of Site-Specific Tyrosine Phosphorylation of Cortactin in Retinal Neovascularization and Vascular Leakage

BACKGROUND

Retinal neovascularization is a major cause of vision impairment. Therefore, the purpose of this study is to investigate the mechanisms by which hypoxia triggers the development of abnormal and leaky blood vessels.

METHODS

A variety of cellular and molecular approaches as well as tissue-specific knockout mice were used to investigate the role of Cttn (cortactin) in retinal neovascularization and vascular leakage.

RESULTS

We found that VEGFA (vascular endothelial growth factor A) stimulates Cttn phosphorylation at Y421, Y453, and Y470 residues in human retinal microvascular endothelial cells. In addition, we observed that while blockade of Cttn phosphorylation at Y470 inhibited VEGFA-induced human retinal microvascular endothelial cell angiogenic events, suppression of Y421 phosphorylation protected endothelial barrier integrity from disruption by VEGFA. In line with these observations, while blockade of Cttn phosphorylation at Y470 negated oxygen-induced retinopathy-induced retinal neovascularization, interference with Y421 phosphorylation prevented VEGFA/oxygen-induced retinopathy-induced vascular leakage. Mechanistically, while phosphorylation at Y470 was required for its interaction with Arp2/3 and CDC6 facilitating actin polymerization and DNA synthesis, respectively, Cttn phosphorylation at Y421 leads to its dissociation from VE-cadherin, resulting in adherens junction disruption. Furthermore, whereas Cttn phosphorylation at Y470 residue was dependent on Lyn, its phosphorylation at Y421 residue required Syk activation. Accordingly, lentivirus-mediated expression of shRNA targeting Lyn or Syk levels inhibited oxygen-induced retinopathy-induced retinal neovascularization and vascular leakage, respectively.

CONCLUSIONS

The above observations show for the first time that phosphorylation of Cttn is involved in a site-specific manner in the regulation of retinal neovascularization and vascular leakage. In view of these findings, Cttn could be a novel target for the development of therapeutics against vascular diseases such as retinal neovascularization and vascular leakage.

Mathematical Modelling of Cervical Precancerous Lesion Grade Risk Scores: Linear Regression Analysis of Cellular Protein Biomarkers and Human Papillomavirus E6/E7 RNA Staining Patterns

The current practice of determining histologic grade with a single molecular biomarker can facilitate differential diagnosis but cannot predict the risk of lesion progression. Cancer is caused by complex mechanisms, and no single biomarker can both make accurate diagnoses and predict progression risk. Modelling using multiple biomarkers can be used to derive scores for risk prediction. Mathematical models (MMs) may be capable of making predictions from biomarker data. Therefore, this study aimed to develop MM–based scores for predicting the risk of precancerous cervical lesion progression and identifying precancerous lesions in patients in northern Thailand by evaluating the expression of multiple biomarkers. The MMs (Models 1–5) were developed in the test sample set based on patient age range (five categories) and biomarker levels (cortactin, p16INK4A, and Ki–67 by immunohistochemistry [IHC], and HPV E6/E7 ribonucleic acid (RNA) by in situ hybridization [ISH]). The risk scores for the prediction of cervical lesion progression (“risk biomolecules”) ranged from 2.56–2.60 in the normal and low–grade squamous intraepithelial lesion (LSIL) cases and from 3.54–3.62 in cases where precancerous lesions were predicted to progress. In Model 4, 23/86 (26.7%) normal and LSIL cases had biomolecule levels that suggested a risk of progression, while 5/86 (5.8%) cases were identified as precancerous lesions. Additionally, histologic grading with a single molecular biomarker did not identify 23 cases with risk, preventing close patient monitoring. These results suggest that biomarker level–based risk scores are useful for predicting the risk of cervical lesion progression and identifying precancerous lesion development. This multiple biomarker–based strategy may ultimately have utility for predicting cancer progression in other contexts.

A Meta-Analysis Study to Infer Voltage-Gated K+ Channels Prognostic Value in Different Cancer Types

Potassium channels are often highly expressed in cancer cells with respect to healthy ones, as they provide proliferative advantages through modulating membrane potential, calcium homeostasis, and various signaling pathways. Among potassium channels, Shaker type voltage-gated Kv channels are emerging as promising pharmacological targets in oncology. Here, we queried publicly available cancer patient databases to highlight if a correlation exists between Kv channel expression and survival rate in five different cancer types. By multiple gene comparison analysis, we found a predominant expression of KCNA2, KCNA3, and KCNA5 with respect to the other KCNA genes in skin cutaneous melanoma (SKCM), uterine corpus endometrial carcinoma (UCEC), stomach adenocarcinoma (STAD), lung adenocarcinoma (LUAD), and lung squamous cell carcinoma (LUSC). This analysis highlighted a prognostic role of KCNA3 and KCNA5 in SKCM, LUAD, LUSC, and STAD, respectively. Interestingly, KCNA3 was associated with a positive prognosis in SKCM and LUAD but not in LUSC. Results obtained by the analysis of KCNA3-related differentially expressed genes (DEGs); tumor immune cell infiltration highlighted differences that may account for such differential prognosis. A meta-analysis study was conducted to investigate the role of KCNA channels in cancer using cancer patients’ datasets. Our study underlines a promising correlation between Kv channel expression in tumor cells, in infiltrating immune cells, and survival rate.

Dematin inhibits glioblastoma malignancy through RhoA-mediated CDKs downregulation and cytoskeleton remodeling

Glioblastoma multiforme (GBM) is well known as a highly aggressive brain tumor subtype. Here, we show that overexpression (OE) of dematin actin-binding protein (DMTN) inhibits GBM proliferation and invasion by affecting cell cycle regulation and actin remodeling, respectively. RT-qPCR, western blotting, and immunohistochemical (IHC) staining demonstrated a significant reduction in DMTN expression in gliomas, especially in high-grade gliomas (HGG) compared with normal brains, which correlates with worse survival in HGG patients. Functional studies revealed inhibitory effects of DMTN on tumor proliferation and migratory capacities. The attenuation in tumor proliferative ability upon DMTN OE was accompanied by RhoA suppression and CDK1, CDK2, CDK4, and cyclin D1 downregulation, while RhoA rescue restored the proliferative phenotype. Meanwhile, overexpression of DMTN produced profoundly disorganized stress fibers, which led to impaired tumor invasion. Furthermore, DMTN overexpression produced substantial suppression of tumor growth upon subcutaneous and intracranial implantation in mice, and this was accompanied by significantly reduced vinculin expression and Ki67 positivity. Taken together, these findings demonstrate the role of DMTN in regulating GBM cell proliferation, actin cytoskeleton, and cell morphology and identify DMTN as a vital tumor suppressor in GBM progression.

Actin-Binding Proteins as Potential Biomarkers for Chronic Inflammation-Induced Cancer Diagnosis and Therapy

Actin-binding proteins (ABPs), by interacting with actin, regulate the polymerization, depolymerization, bundling, and cross-linking of actin filaments, directly or indirectly, thereby mediating the maintenance of cell morphology, cell movement, and many other biological functions. Consequently, these functions of ABPs help regulate cancer cell invasion and metastasis when cancer occurs. In recent years, a variety of ABPs have been found to be abnormally expressed in various cancers, indicating that the detection and interventions of unusual ABP expression to alter this are available for the treatment of cancer. The early stages of most cancer development involve long-term chronic inflammation or repeated stimulation. This is the case for breast cancer, gastric cancer, lung cancer, prostate cancer, liver cancer, esophageal cancer, pancreatic cancer, melanoma, and colorectal cancer. This article discusses the relationship between chronic inflammation and the above-mentioned cancers, emphatically introduces relevant research on the abnormal expression of ABPs in chronic inflammatory diseases, and reviews research on the expression of different ABPs in the above-mentioned cancers. Furthermore, there is a close relationship between ABP-induced inflammation and cancer. In simple terms, abnormal expression of ABPs contributes to the chronic inflammation developing into cancer. Finally, we provide our viewpoint regarding these unusual ABPs serving as potential biomarkers for chronic inflammation-induced cancer diagnosis and therapy, and interventions to reverse the abnormal expression of ABPs represent a potential approach to preventing or treating the corresponding cancers.

The Plasma Membrane Ca2+ Pump PMCA4b Regulates Melanoma Cell Migration through Remodeling of the Actin Cytoskeleton

Simple Summary

Earlier we demonstrated that the plasma membrane Ca²⁺ pump PMCA4b inhibits migration and metastatic activity of BRAF mutant melanoma cells, however, the exact mechanism has not been fully understood. Here we demonstrate that PMCA4b acted through actin cytoskeleton remodeling in generating a low migratory melanoma cell phenotype resulting in increased cell–cell connections, lamellipodia and stress fiber formation. Both proper trafficking and calcium transporting activity of the pump were essential to complete these tasks indicating that controlling Ca²⁺ concentration levels at specific plasma membrane locations such as the cell front played a role. Our findings suggest that PMCA4b downregulation is likely one of the mechanisms that leads to the perturbed cancer cell cytoskeleton organization resulting in enhanced melanoma cell migration and metastasis.

Abstract

We demonstrated that the plasma membrane Ca²⁺ ATPase PMCA4b inhibits migration and metastatic activity of BRAF mutant melanoma cells. Actin dynamics are essential for cells to move, invade and metastasize, therefore, we hypothesized that PMCA4b affected cell migration through remodeling of the actin cytoskeleton. We found that expression of PMCA4b in A375 BRAF mutant melanoma cells induced a profound change in cell shape, cell culture morphology, and displayed a polarized migratory character. Along with these changes the cells became more rounded with increased cell–cell connections, lamellipodia and stress fiber formation. Silencing PMCA4b in MCF-7 breast cancer cells had a similar effect, resulting in a dramatic loss of stress fibers. In addition, the PMCA4b expressing A375 cells maintained front-to-rear Ca²⁺ concentration gradient with the actin severing protein cofilin localizing to the lamellipodia, and preserved the integrity of the actin cytoskeleton from a destructive Ca²⁺ overload. We showed that both PMCA4b activity and trafficking were essential for the observed morphology and motility changes. In conclusion, our data suggest that PMCA4b plays a critical role in adopting front-to-rear polarity in a normally spindle-shaped cell type through F-actin rearrangement resulting in a less aggressive melanoma cell phenotype.

PRMT5 promotes cancer cell migration and invasion through the E2F pathway

The pRb-E2F pathway is a critical point of regulation in the cell cycle and loss of control of the pathway is a hallmark of cancer. E2F1 is the major target through which pRb exerts its effects and arginine methylation by PRMT5 plays a key role in dictating E2F1 activity. Here we have explored the functional role of the PRMT5-E2F1 axis and highlight its influence on different aspects of cancer cell biology including viability, migration, invasion and adherence. Through a genome-wide expression analysis, we identified a distinct set of genes under the control of PRMT5 and E2F1, including some highly regulated genes, which influence cell migration, invasio and adherence through a PRMT5-dependent mechanism. Most significantly, a coincidence was apparent between the expression of PRMT5 and E2F1 in human tumours, and elevated levels of PRMT5 and E2F1 correlated with poor prognosis disease. Our results suggest a causal relationship between PRMT5 and E2F1 in driving the malignant phenotype and thereby highlight an important pathway for therapeutic intervention.

Exoenzyme C3 transferase lowers actin cytoskeleton dynamics, genomic stability and survival of malignant melanoma cells under UV-light stress

Actin cytoskeleton remodeling is the major motor of cytoskeleton dynamics driving tumor cell adhesion, migration and invasion. The typical RhoA, RhoB and RhoC GTPases are the main regulators of actin cytoskeleton dynamics. The C3 exoenzyme transferase from Clostridium botulinum is a toxin that causes the specific ADP-ribosylation of Rho-like proteins, leading to its inactivation. Here, we examine what effects the Rho GTPase inhibition and the consequent actin cytoskeleton instability would have on the emergence of DNA damage and on the recovery of genomic stability of malignant melanoma cells, as well as on their survival. Therefore, the MeWo cell line, here assumed as a melanoma cell line model for the expression of genes involved in the regulation of the actin cytoskeleton, was transiently transfected with the C3 toxin and subsequently exposed to UV-radiation. Phalloidin staining of the stress fibers revealed that actin cytoskeleton integrity was strongly disrupted by the C3 toxin in association with reduced melanoma cells survival, and further enhanced the deleterious effects of UV light. MeWo cells with actin cytoskeleton previously perturbed by the C3 toxin still showed higher levels and accumulation of UV-damaged DNA (strand breaks and cyclobutane pyrimidine dimers, CPDs). The interplay between reduced cell survival and impaired DNA repair upon actin cytoskeleton disruption can be explained by constitutive ERK1/2 activation and an inefficient phosphorylation of DDR proteins (γH2AX, CHK1 and p53) caused by C3 toxin treatment. Altogether, these results support the general idea that actin network help to protect the genome of human cells from damage caused by UV light through unknown molecular mechanisms that tie the cytoskeleton to processes of genomic stability maintenance.

Arp2/3-Branched Actin Maintains an Active Pool of GTP-RhoA and Controls RhoA Abundance

Small GTPases regulate cytoskeletal dynamics, cell motility, and division under precise spatiotemporal control. Different small GTPases exhibit cross talks to exert feedback response or to act in concert during signal transduction. However, whether and how specific cytoskeletal components' feedback to upstream signaling factors remains largely elusive. Here, we report an intriguing finding that disruption of the Arp2/3-branched actin specifically reduces RhoA activity but upregulates its total protein abundance. We further dissect the mechanisms underlying these circumstances and identify the altered cortactin/p190RhoGAP interaction and weakened CCM2/Smurf1 binding to be involved in GTP-RhoA reduction and total RhoA increase, respectively. Moreover, we find that cytokinesis defects induced by Arp2/3 inhibition can be rescued by activating RhoA. Our study reveals an intricate feedback from the actin cytoskeleton to the small GTPase. Our work highlights the role of Arp2/3-branched actin in signal transduction aside from its function in serving as critical cytoskeletal components to maintain cell morphology and motility.

The Drosophila protein, Nausicaa, regulates lamellipodial actin dynamics in a Cortactin-dependent manner

Drosophila CG10915 is an uncharacterized protein coding gene with sequence similarity to human Cortactin-binding protein 2 (CTTNBP2) and Cortactin-binding protein 2 N-terminal-like (CTTNBP2NL). Here, we have named this gene Nausicaa (naus) and characterize it through a combination of quantitative live-cell total internal reflection fluorescence microscopy, electron microscopy, RNAi depletion and genetics. We found that Naus co-localizes with F-actin and Cortactin in the lamellipodia of Drosophila S2R+ and D25c2 cells and this localization is lost following Cortactin or Arp2/3 depletion or by mutations that disrupt a conserved proline patch found in its mammalian homologs. Using permeabilization activated reduction in fluorescence and fluorescence recovery after photobleaching, we find that depletion of Cortactin alters Naus dynamics leading to a decrease in its half-life. Furthermore, we discovered that Naus depletion in S2R+ cells led to a decrease in actin retrograde flow and a lamellipodia characterized by long, unbranched filaments. We demonstrate that these alterations to the dynamics and underlying actin architecture also affect D25c2 cell migration and decrease arborization in Drosophila neurons. We present the hypothesis that Naus functions to slow Cortactin's disassociation from Arp2/3 nucleated branch junctions, thereby increasing both branch nucleation and junction stability.

Overexpression and Tyr421-phosphorylation of cortactin is induced by three-dimensional spheroid culturing and contributes to migration and invasion of pancreatic ductal adenocarcinoma (PDAC) cells

BACKGROUND

The nucleation-promoting factor cortactin is expressed and promotes tumor progression and metastasis in various cancers. However, little is known about the biological role of cortactin in the progression of pancreatic ductal adenocarcinoma (PDAC).

METHODS

Cortactin and phosphorylated cortactin (Y421) were investigated immunohistochemically in 66 PDAC tumor specimens. To examine the functional role of cortactin in PDAC, we modulated cortactin expression by establishing two cortactin knockout cell lines (Panc-1 and BxPC-3) with CRISPR/Cas9 technique. Cortactin knockout was verified by immunoblotting and immunofluorescence microscopy and functional effects were determined by cell migration and invasion assays. A proteomic screening approach was performed to elucidate potential binding partners of cortactin.

RESULTS

Immunohistochemically, we observed higher cortactin expression and Tyr421-phosphorylation in PDAC metastases compared to primary tumor tissues. In PDAC cell lines Panc-1 and BxPC-3, knockdown of cortactin impaired migration and invasion, while cell proliferation was not affected. Three-dimensional spheroid culturing as a model for collective cell migration enhanced cortactin expression and Tyr421-phosphorylation. The activation of cortactin as well as the migratory capacity of PDAC cells could significantly be reduced by dasatinib, a Src family kinase inhibitor. Finally, we identified gelsolin as a novel protein interaction partner of cortactin in PDAC.

CONCLUSION

Our data provides evidence that cohesive cell migration induces cortactin expression and phosphorylation as a prerequisite for the gain of an invasive, pro-migratory phenotype in PDAC that can effectively be targeted with dasatinib.

Loci-specific differences in blood DNA methylation in HBV-negative populations at risk for hepatocellular carcinoma development

Late onset of clinical symptoms in hepatocellular carcinoma (HCC) results in late diagnosis and poor disease outcome. Approximately 85% of individuals with HCC have underlying liver cirrhosis. However, not all cirrhotic patients develop cancer. Reliable tools that would distinguish cirrhotic patients who will develop cancer from those who will not are urgently needed. We used the Illumina HumanMethylation450 BeadChip microarray to test whether white blood cell DNA, an easily accessible source of DNA, exhibits site-specific changes in DNA methylation in blood of diagnosed HCC patients (post-diagnostic, 24 cases, 24 controls) and in prospectively collected blood specimens of HCC patients who were cancer-free at blood collection (pre-diagnostic, 21 cases, 21 controls). Out of 22 differentially methylated loci selected for validation by pyrosequencing, 19 loci with neighbouring CpG sites (probes) were confirmed in the pre-diagnostic study group and subjected to verification in a prospective cirrhotic cohort (13 cases, 23 controls). We established for the first time 9 probes that could distinguish HBV-negative cirrhotic patients who subsequently developed HCC from those who stayed cancer-free. These probes were identified within regulatory regions of BARD1, MAGEB3, BRUNOL5, FXYD6, TET1, TSPAN5, DPPA5, KIAA1210, and LSP1. Methylation levels within DPPA5, KIAA1210, and LSP1 were higher in prospective samples from HCC cases vs. cirrhotic controls. The remaining probes were hypomethylated in cases compared with controls. Using blood as a minimally invasive material and pyrosequencing as a straightforward quantitative method, the established probes have potential to be developed into a routine clinical test after validation in larger cohorts.

Hematopoietic lineage cell-specific protein 1 immunoreactivity indicates an increased risk of poor overall survival in patients with ovarian carcinoma

Hematopoietic lineage cell-specific protein 1 (HS1) is a 75-kDa intracellular protein that is expressed primarily in hematopoietic cells. Several previous studies have demonstrated the association between HS1 expression and a poor prognosis in hematopoietic malignancies; however, in solid tumors, no studies not been reported. The present study examined the distribution and expression of HS1 in human epithelial ovarian carcinoma (EOC) to determine its clinical significance. Paraffin sections were obtained from EOC tissues and immunostained with HS1 antibody, and then the staining intensities were evaluated. Overall survival (OS) was determined using the Kaplan-Meier estimator method, and multivariate analysis was performed using the Cox proportional hazards analysis. In total, 195 patients with EOC (median age, 56 years) were enrolled into the present study. HS1 immunoreactivity was categorized based on expression levels: Low (89/195; 45.6%) and high (106/195; 54.4%). Results demonstrated no association between expression level(s) and any clinicopathological parameter including age, International Federation of Gynecology and Obstetrics (FIGO) staging, type of chemotherapy or type of surgery received. The 5-year OS rates of patients who demonstrated low (n=89) and high (n=106) HS1 expression were 90.4 and 66.7%, respectively. The OS times for patients with high HS1 expression were significantly shorter compared with those for patients exhibiting low HS1 expression (P=0.0065). Results obtained from the multivariate analysis demonstrated that the FIGO stage and the amount of HS1 expressed were significant independent prognostic markers for poorer OS (hazard ratio, 3.539; 95% confidence interval, 1.221-12.811; P=0.0187). High HS1 expression levels may serve as a useful biomarker in patients with EOC who are likely to exhibit an unfavorable clinical outcome.

Cortactin function in invadopodia

Actin remodeling plays an essential role in diverse cellular processes such as cell motility, vesicle trafficking or cytokinesis. The scaffold protein and actin nucleation promoting factor Cortactin is present in virtually all actin-based structures, participating in the formation of branched actin networks. It has been involved in the control of endocytosis, and vesicle trafficking, axon guidance and organization, as well as adhesion, migration and invasion. To migrate and invade through three-dimensional environments, cells have developed specialized actin-based structures called invadosomes, a generic term to designate invadopodia and podosomes. Cortactin has emerged as a critical regulator of invadosome formation, function and disassembly. Underscoring this role, Cortactin is frequently overexpressed in several types of invasive cancers. Herein we will review the roles played by Cortactin in these specific invasive structures.

The Arp2/3 Regulatory System and Its Deregulation in Cancer

The Arp2/3 complex is an evolutionary conserved molecular machine that generates branched actin networks. When activated, the Arp2/3 complex contributes the actin branched junction and thus cross-links the polymerizing actin filaments in a network that exerts a pushing force. The different activators initiate branched actin networks at the cytosolic surface of different cellular membranes to promote their protrusion, movement, or scission in cell migration and membrane traffic. Here we review the structure, function, and regulation of all the direct regulators of the Arp2/3 complex that induce or inhibit the initiation of a branched actin network and that controls the stability of its branched junctions. Our goal is to present recent findings concerning novel inhibitory proteins or the regulation of the actin branched junction and place these in the context of what was previously known to provide a global overview of how the Arp2/3 complex is regulated in human cells. We focus on the human set of Arp2/3 regulators to compare normal Arp2/3 regulation in untransformed cells to the deregulation of the Arp2/3 system observed in patients affected by various cancers. In many cases, these deregulations promote cancer progression and have a direct impact on patient survival.

ATG5 Mediates a Positive Feedback Loop between Wnt Signaling and Autophagy in Melanoma

Autophagy mediates resistance to various anticancer agents. In melanoma, resistance to targeted therapy has been linked to expression of Wnt5A, an intrinsic inhibitor of β-catenin, which also promotes invasion. In this study, we assessed the interplay between Wnt5A and autophagy by combining expression studies in human clinical biopsies with functional analyses in cell lines and mouse models. Melanoma cells with high Wnt5A and low β-catenin displayed increased basal autophagy. Genetic blockade of autophagy revealed an unexpected feedback loop whereby knocking down the autophagy factor ATG5 in Wnt5A^high cells decreased Wnt5A and increased β-catenin. To define the physiologic relevance of this loop, melanoma cells with different Wnt status were treated in vitro and in vivo with the potent lysosomotropic compound Lys05. Wnt5A^high cells were less sensitive to Lys05 and could be reverted by inducing β-catenin activity. Our results suggest the efficacy of autophagy inhibitors might be improved by taking the Wnt signature of melanoma cells into account. Cancer Res; 77(21); 5873-85. ©2017 AACR.

Pro-invasive Effect of Proto-oncogene PBF Is Modulated by an Interaction with Cortactin

CONTEXT

Metastatic disease is responsible for the majority of endocrine cancer deaths. New therapeutic targets are urgently needed to improve patient survival rates.

OBJECTIVE

The proto-oncogene PTTG1-binding factor (PBF/PTTG1IP) is overexpressed in multiple endocrine cancers and circumstantially associated with tumor aggressiveness. This study aimed to understand the role of PBF in tumor cell invasion and identify possible routes to inhibit its action. Design, Setting, Patients, and Interventions: Thyroid, breast, and colorectal cells were transfected with PBF and cultured for in vitro analysis. PBF and cortactin (CTTN) expression was determined in differentiated thyroid cancer and The Cancer Genome Atlas RNA-seq data.

PRIMARY OUTCOME MEASURE

Pro-invasive effects of PBF were evaluated by 2D Boyden chamber, 3D organotypic, and proximity ligation assays.

RESULTS

Our study identified that PBF and CTTN physically interact and co-localize, and that this occurs at the cell periphery, particularly at the leading edge of migrating cancer cells. Critically, PBF induces potent cellular invasion and migration in thyroid and breast cancer cells, which is entirely abrogated in the absence of CTTN. Importantly, we found that CTTN is over-expressed in differentiated thyroid cancer, particularly in patients with regional lymph node metastasis, which significantly correlates with elevated PBF expression. Mutation of PBF (Y174A) or pharmacological intervention modulates the PBF: CTTN interaction and attenuates the invasive properties of cancer cells.

CONCLUSION

Our results demonstrate a unique role for PBF in regulating CTTN function to promote endocrine cell invasion and migration, as well as identify a new targetable interaction to block tumor cell movement.

Cortactin contributes to the tumorigenicity of colorectal cancer by promoting cell proliferation

Cortactin is a scaffolding protein that regulates Arp2/3-mediated actin polymerization. We showed in a previous study that cortactin was highly expressed in human stage II-III colorectal cancer (CRC) tissues. In the present study, using colony formation and CCK-8 assays, we showed that overexpression of cortactin accelerated the proliferation of CRC cells. Flow cytometric assays revealed that cortactin promoted G1/S phase cell cycle transition. Later, we constructed the phosphorylation mutation of cortactin at the Tyr421 residue. Colony formation and CCK-8 assays showed that cortactin/Tyr421A lost its ability to promote cell proliferation. Western blot analysis indicated that cortactin activated cyclin D1, but not cortactin/Tyr421A. Further study in nude mice revealed that there was a greater decrease in both tumor volume and tumor weight in animals injected with SW480/cortactin/Tyr421A cells than in those injected with SW480/cortactin/WT cells. Thus, the present study demonstrates that the cortactin Tyr421 residue is required to promote cell proliferation both in vitro and in vivo.

Inhibitory effect of quercetin on epithelial to mesenchymal transition in SK-MEL-28 human melanoma cells defined by in vitro analysis on 3D collagen gels

Considering the emerging concept of complementary and alternative medicine under the paucity of effective treatment for melanoma, we aimed to understand the effect of quercetin (Qu) on collagen I-induced epithelial-mesenchymal transition (EMT) in melanoma cells. To investigate the effect of Qu in melanoma cells, we used multiple methods, including real-time reverse transcription polymerase chain reaction, migration assay, and wound healing assay. We found that EMT was altered by Qu in melanoma cells. Qu-treated cells exhibited decreased migration and invasion activities. Mechanistically, a high expression of epithelial markers and a decrease in the expression of mesenchymal markers were found to be associated with reversal of EMT in melanoma cells. Time-dependent apoptosis was observed in Qu-treated melanoma cells, which was further confirmed by the upregulation in the protein levels of Caspase 3, a proapoptotic marker. Thus, our findings suggest Qu as a promising dietary compound under the new complementary and alternative medicine category of therapeutic drugs in the chemoprevention of melanoma.

HSP70 Inhibition Limits FAK-Dependent Invasion and Enhances the Response to Melanoma Treatment with BRAF Inhibitors

The stress-inducible chaperone protein HSP70 (HSPA1) is implicated in melanoma development, and HSP70 inhibitors exert tumor-specific cytotoxic activity in cancer. In this study, we documented that a significant proportion of melanoma tumors express high levels of HSP70, particularly at advanced stages, and that phospho-FAK (PTK2) and BRAF are HSP70 client proteins. Treatment of melanoma cells with HSP70 inhibitors decreased levels of phospho-FAK along with impaired migration, invasion, and metastasis in vitro and in vivo Moreover, the HSP70 inhibitor PET-16 reduced levels of mutant BRAF, synergized with the BRAF inhibitor PLX4032 in vitro, and enhanced the durability of response to BRAF inhibition in vivo Collectively, these findings provide strong support for HSP70 inhibition as a therapeutic strategy in melanoma, especially as an adjuvant approach for overcoming the resistance to BRAF inhibitors frequently observed in melanoma patients. Cancer Res; 76(9); 2720-30. ©2016 AACR.

MTSS1 suppresses cell migration and invasion by targeting CTTN in glioblastoma

Glioblastomas (GBMs) are the highest grade of primary brain tumors with astrocytic similarity and are characterized dispersal of tumor cell. Metastasis suppressor 1 (MTSS1) play an important role in cancer metastasis. Recent studies indicating that MTSS1 as a potential tumor suppressor and its reduced expression associated with poor prognosis in many cancer types. However, the relationship with the prognosis of patients and the molecular mechanism of MTSS1 renders a tumor suppressor effect in GBM is unknown. Here, we showed that low MTSS1 gene expression is associated with poor outcomes in patients with GBM. Overexpression of MTSS1 in U-87 MG cells exhibited inhibited glioma cell growth, colony formation, migration and invasion. Mechanistically, we found that high MTSS1 expression in U-87 MG reduced expression of CTTN. These results implicate that the role of MTSS1 suppresses cell migration and invasion by inhibiting expression of CTTN and as a prognosis biomarker in GBM.

Movers and shakers: cell cytoskeleton in cancer metastasis

Metastasis is responsible for the greatest number of cancer deaths. Metastatic disease, or the movement of cancer cells from one site to another, is a complex process requiring dramatic remodelling of the cell cytoskeleton. The various components of the cytoskeleton, actin (microfilaments), microtubules (MTs) and intermediate filaments, are highly integrated and their functions are well orchestrated in normal cells. In contrast, mutations and abnormal expression of cytoskeletal and cytoskeletal-associated proteins play an important role in the ability of cancer cells to resist chemotherapy and metastasize. Studies on the role of actin and its interacting partners have highlighted key signalling pathways, such as the Rho GTPases, and downstream effector proteins that, through the cytoskeleton, mediate tumour cell migration, invasion and metastasis. An emerging role for MTs in tumour cell metastasis is being unravelled and there is increasing interest in the crosstalk between key MT interacting proteins and the actin cytoskeleton, which may provide novel treatment avenues for metastatic disease. Improved understanding of how the cytoskeleton and its interacting partners influence tumour cell migration and metastasis has led to the development of novel therapeutics against aggressive and metastatic disease.

LINKED ARTICLES

This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.

Melanoma risk loci as determinants of melanoma recurrence and survival

Background

Steadily high melanoma mortality rates urge for the availability of novel biomarkers with a more personalized ability to predict melanoma clinical outcomes. Germline risk variants are promising candidates for this purpose; however, their prognostic potential in melanoma has never been systematically tested.

Methods

We examined the effect of 108 melanoma susceptibility single nucleotide polymorphisms (SNPs), associated in recent GWAS with melanoma and melanoma-related phenotypes, on recurrence-free survival (RFS) and overall survival (OS), in 891 prospectively accrued melanoma patients. Cox proportional hazards models (Cox PH) were used to test the associations between 108 melanoma risk SNPs and RFS and OS adjusted by age at diagnosis, gender, tumor stage, histological subtype and other primary tumor characteristics.

Results

We identified significant associations for rs7538876 (RCC2) with RFS (HR = 1.48, 95% CI = 1.20-1.83, p = 0.0005) and rs9960018 (DLGAP1) with both RFS and OS (HR = 1.43, 95% CI = 1.07-1.91, p = 0.01, HR = 1.52, 95% CI = 1.09-2.12, p = 0.01, respectively) using multivariable Cox PH models. In addition, we developed a logistic regression model that incorporates rs7538876, rs9960018, primary tumor histological type and stage at diagnosis that has an improved discriminatory ability to classify 3-year recurrence (AUC = 82%) compared to histological type and stage alone (AUC = 78%).

Conclusions

We identified associations between melanoma risk variants and melanoma outcomes. The significant associations observed for rs7538876 and rs9960018 suggest a biological implication of these loci in melanoma progression. The observed predictive patterns of associated variants with clinical end-points suggest for the first time the potential for utilization of genetic risk markers in melanoma prognostication.

Expression of DIAPH1 is up-regulated in colorectal cancer and its down-regulation strongly reduces the metastatic capacity of colon carcinoma cells

In most cases, metastatic colorectal cancer is not curable, thus new approaches are necessary to identify novel targets for colorectal cancer therapy. Actin-binding-proteins (ABPs) directly regulate motility of metastasising tumor cells, and for cortactin an association with colon cancer metastasis has been already shown. However, as its depletion only incompletely inhibits metastasis, additional, more suitable cellular targets have to be identified. Here we analyzed expression of the ABPs, DIAPH1, VASP, N-WASP, and fascin in comparison with cortactin and found that, besides cortactin, DIAPH1 was expressed with the highest frequency (63%) in colorectal cancer. As well as cortactin, DIAPH1 was not detectable in normal colon tissue and expression of both proteins was positively correlated with metastasis of colorectal cancer. To analyse the mechanistic role of DIAPH1 for metastasis of colon carcinoma cells in comparison with cortactin, expression of the proteins was stably down-regulated in the human colon carcinoma cell lines HT-29, HROC-24 and HCT-116. Analysis of metastasis of colon carcinoma cells in SCID mice revealed that depletion of DIAPH1 reduced metastasis 60-fold and depletion of cortactin 16-fold as compared with control cells. Most likely the stronger effect of DIAPH1 depletion on colon cancer metastasis is due to the fact that in vitro knock down of DIAPH1 impaired all steps of metastasis; adhesion, invasion and migration while down-regulation of cortactin only reduced adhesion and invasion. This very strong reducing effect of DIAPH1 depletion on colon carcinoma cell metastasis makes the protein a promising therapeutic target for individualized colorectal cancer therapy.

Neutrophils Activate Tumoral CORTACTIN to Enhance Progression of Orohypopharynx Carcinoma

CORTACTIN is an actin-binding protein critically involved in cellular migration and invasion. Here, we investigated the role of CORTACTIN in the pathophysiology of orohypopharynx carcinoma – one of the major subtypes of head and neck cancer. To this end, we analyzed CORTACTIN expression in tumor tissues from 89 orohypopharynx carcinoma patients in relation to clinical parameters. We found that high tumoral CORTACTIN expression associated with poor survival, higher T-stage, and higher lymph node metastasis (N-stage) in these patients. Next, we combined the prognostic values of tumoral and stromal cell biological parameters in our patient cohort. We determined the potential interaction of tumoral CORTACTIN with tumor-infiltrating neutrophils, which have been previously linked to poor clinical outcome in orohypopharynx carcinoma patients with advanced disease. Interestingly, we found that patients with both high tumoral CORTACTIN expression and high neutrophilic infiltration had significantly worse clinical outcome than all other patients in our cohort. These findings suggest that tumoral CORTACTIN and tumor-infiltrating neutrophils might be functionally linked during progression of orohypopharynx carcinoma. In vitro, we showed that neutrophils released soluble factors which phosphorylated CORTACTIN in the tumor cells and promoted their migration. Furthermore, we demonstrated that strong CORTACTIN phosphorylation significantly correlated with strong neutrophilic infiltration in tumor tissues from orohypopharynx carcinoma patients. Taken together, our findings unravel a novel mechanism of tumor-stroma interaction, which might be relevant for a more accurate prognosis and improved therapeutic strategies in this tumor entity.

Nucleus accumbens-associated 1 contributes to cortactin deacetylation and augments the migration of melanoma cells

We investigated the prognostic significance and post-transcriptional acetylation-modification of cortactin (CTTN) via the nucleus accumbens-associated 1 (NACC1)-histone deacetylase 6 (HDAC6) deacetylation system in primary melanomas and melanoma cell lines. Overexpression of CTTN protein was observed in 56 (73%) of 77 stage I-IV melanomas, and was significantly correlated with tumor thickness, lymph node metastasis, distant metastasis, and disease outcome. The patients whose tumors exhibited CTTN overexpression had a poorer outcome than patients without this feature (P=0.028, log-rank test). NACC1 and CTTN proteins, but not HDAC6, were overexpressed in four melanoma cell lines in comparison with a primary culture of normal human epidermal melanocytes. Knockdown of both NACC1 and HDAC6 markedly downregulated the migration activity of all melanoma cell lines (P<0.05), and induced a gain of CTTN protein acetylation status. Confocal microscopy showed that hyperacetylation of CTTN modulated by depletion of both NACC1 and HDAC6 induced disappearance of CTTN protein at the leading edge of migrating cells, resulting in stabilization of the focal adhesion structure and development of actin stress fibers. These data suggest that the acetylation status of CTTN modulated by the NACC1-HDAC6 deacetylation system induces acceleration of melanoma cell migration activity via an actin-dependent cellular process, possibly contributing to aggressive behavior (invasion/metastasis) of the melanoma cells.

Nucleating actin for invasion

The invasion of cancer cells into the surrounding tissue is a prerequisite and initial step in metastasis, which is the leading cause of death from cancer. Invasive cell migration requires the formation of various structures, such as invadopodia and pseudopodia, which require actin assembly that is regulated by specialized actin nucleation factors. There is a large variety of different actin nucleators in human cells, such as formins, spire and Arp2/3-regulating proteins, and the list is likely to grow. Studies of the mechanisms of various actin nucleation factors that are involved in cancer cell function may ultimately provide new treatments for invasive and metastatic disease.

Cortactin: a multifunctional regulator of cellular invasiveness

Branched actin assembly is critical for a variety of cellular processes that underlie cell motility and invasion, including cellular protrusion formation and membrane trafficking. Activation of branched actin assembly occurs at various subcellular locations via site-specific activation of distinct WASp family proteins and the Arp2/3 complex. A key branched actin regulator that promotes cell motility and links signaling, cytoskeletal and membrane trafficking proteins is the Src kinase substrate and Arp2/3 binding protein cortactin. Due to its frequent overexpression in advanced, invasive cancers and its general role in regulating branched actin assembly at multiple cellular locations, cortactin has been the subject of intense study. Recent studies suggest that cortactin has a complex role in cellular migration and invasion, promoting both on-site actin polymerization and modulation of autocrine secretion. Diverse cellular activities may derive from the interaction of cortactin with site-specific binding partners.

Cortactin phosphorylated by ERK1/2 localizes to sites of dynamic actin regulation and is required for carcinoma lamellipodia persistence

Background

Tumor cell motility and invasion is governed by dynamic regulation of the cortical actin cytoskeleton. The actin-binding protein cortactin is commonly upregulated in multiple cancer types and is associated with increased cell migration. Cortactin regulates actin nucleation through the actin related protein (Arp)2/3 complex and stabilizes the cortical actin cytoskeleton. Cortactin is regulated by multiple phosphorylation events, including phosphorylation of S405 and S418 by extracellular regulated kinases (ERK)1/2. ERK1/2 phosphorylation of cortactin has emerged as an important positive regulatory modification, enabling cortactin to bind and activate the Arp2/3 regulator neuronal Wiskott-Aldrich syndrome protein (N-WASp), promoting actin polymerization and enhancing tumor cell movement.

Methodology/Principal Findings

In this report we have developed phosphorylation-specific antibodies against phosphorylated cortactin S405 and S418 to analyze the subcellular localization of this cortactin form in tumor cells and patient samples by microscopy. We evaluated the interplay between cortactin S405 and S418 phosphorylation with cortactin tyrosine phosphorylation in regulating cortactin conformational forms by Western blotting. Cortactin is simultaneously phosphorylated at S405/418 and Y421 in tumor cells, and through the use of point mutant constructs we determined that serine and tyrosine phosphorylation events lack any co-dependency. Expression of S405/418 phosphorylation-null constructs impaired carcinoma motility and adhesion, and also inhibited lamellipodia persistence monitored by live cell imaging.

Conclusions/Significance

Cortactin phosphorylated at S405/418 is localized to sites of dynamic actin assembly in tumor cells. Concurrent phosphorylation of cortactin by ERK1/2 and tyrosine kinases enables cells with the ability to regulate actin dynamics through N-WASp and other effector proteins by synchronizing upstream regulatory pathways, confirming cortactin as an important integration point in actin-based signal transduction. Reduced lamellipodia persistence in cells with S405/418A expression identifies an essential motility-based process reliant on ERK1/2 signaling, providing additional understanding as to how this pathway impacts tumor cell migration.

From melanocyte to metastatic malignant melanoma

Malignant melanoma is one of the most aggressive malignancies in human and is responsible for almost 60% of lethal skin tumors. Its incidence has been increasing in white population in the past two decades. There is a complex interaction of environmental (exogenous) and endogenous, including genetic, risk factors in developing malignant melanoma. 8–12% of familial melanomas occur in a familial setting related to mutation of the CDKN2A gene that encodes p16. The aim of this is to briefly review the microanatomy and physiology of the melanocytes, epidemiology, risk factors, clinical presentation, historical classification and histopathology and, more in details, the most recent discoveries in biology and genetics of malignant melanoma. At the end, the final version of 2009 AJCC malignant melanoma staging and classification is presented.