Differential expression of vinculin between weakly and highly metastatic B16-melanoma cell lines

Detecting normal and cancer skin cells via glycosylation and adhesion signatures: A path to enhanced microfluidic phenotyping

Recruiting circulating cells based on interactions between surface receptors and corresponding ligands holds promise for capturing cells with specific adhesive properties. Our study investigates the adhesion of skin cells to specific lectins, particularly focusing on advancements in lectin-based biosensors with diagnostic potential. We explore whether we can successfully capture normal skin (melanocytes and keratinocytes) and melanoma (WM35, WM115, WM266-4) cells in a low-shear flow environment by coating surfaces with lectins. Specifically, we coated surfaces with Dolichos biflorus (DBA) and Maackia Amurensis (MAL) lectins, which were used to detect and capture specific skin cells from the flow of cell mixture. Alterations in glycan expression (confirmed by fluorescent microscopy) demonstrated that DBA binds predominantly to normal skin cells, while MAL interacts strongly with melanoma cells. Assessing adhesion under static and dynamic low-shear stress conditions (up to 30 mPa) underscores the reliability of DBA and MAL as markers for discriminating specific cell type. Melanocytes and keratinocytes adhere to DBA-coated surfaces, while melanoma cells prefer MAL-coated surfaces. A comprehensive analysis encompassing cell shape, cytoskeleton, and focal adhesions shows the independence of our approach from the inherent characteristics of cells, thus demonstrating its robustness. Our results carry practical implications for lectin-biosensor designs, emphasizing the significance of glycan-based discrimination of pathologically altered cells. Combined with microfluidics, it demonstrates the value of cell adhesion as a discriminant of cancer-related changes, with potential applications spanning diagnostics, therapeutic interventions, and advanced biomedical technologies.

High expression of Talin-1 is associated with tumor progression and recurrence in melanoma skin cancer patients

BACKGROUND

Talin-1 as a component of multi-protein adhesion complexes plays a role in tumor formation and migration in various malignancies. This study investigated Talin-1 in protein levels as a potential prognosis biomarker in skin tumors.

METHODS

Talin-1 was evaluated in 106 skin cancer (33 melanomas and 73 non-melanomas skin cancer (NMSC)) and 11 normal skin formalin-fixed paraffin-embedded (FFPE) tissue samples using immunohistochemical technique on tissue microarrays (TMAs). The association between the expression of Talin-1 and clinicopathological parameters, as well as survival outcomes, were assessed.

RESULTS

Our findings from data minings through bioinformatics tools indicated dysregulation of Talin-1 in mRNA levels for skin cancer samples. In addition, there was a statistically significant difference in Talin-1 expression in terms of intensity of staining, percentage of positive tumor cells, and H-score in melanoma tissues compared to NMSC (P = 0.001, P < 0.001, and P < 0.001, respectively). Moreover, high cytoplasmic expression of Talin-1 was found to be associated with significantly advanced stages (P = 0.024), lymphovascular invasion (P = 0.023), and recurrence (P = 0.006) in melanoma cancer tissues. Our results on NMSC showed a statistically significant association between high intensity of staining and the poor differentiation (P = 0.044). No significant associations were observed between Talin-1 expression levels and survival outcomes of melanoma and NMSC patients.

CONCLUSION

Our observations showed that higher expression of Talin1 in protein level may be significantly associated with more aggressive tumor behavior and advanced disease in patients with skin cancer. However, further studies are required to find the mechanism of action of Talin-1 in skin cancers.

Adhesion strength and anti-tumor agents regulate vinculin of breast cancer cells

The onset and progression of cancer are strongly associated with the dissipation of adhesion forces between cancer cells, thus facilitating their incessant attachment and detachment from the extracellular matrix (ECM) to move toward metastasis. During this process, cancer cells undergo mechanical stresses and respond to these stresses with membrane deformation while inducing protrusions to invade the surrounding tissues. Cellular response to mechanical forces is inherently related to the reorganization of the cytoskeleton, the dissipation of cell–cell junctions, and the adhesion to the surrounding ECM. Moreover, the role of focal adhesion proteins, and particularly the role of vinculin in cell attachment and detachment during migration, is critical, indicating the tight cell–ECM junctions, which favor or inhibit the metastatic cascade. The biomechanical analysis of these sequences of events may elucidate the tumor progression and the potential of cancer cells for migration and metastasis. In this work, we focused on the evaluation of the spreading rate and the estimation of the adhesion strength between breast cancer cells and ECM prior to and post-treatment with anti-tumor agents. Specifically, different tamoxifen concentrations were used for ER⁺ breast cancer cells, while even concentrations of trastuzumab and pertuzumab were used for HER2⁺ cells. Analysis of cell stiffness indicated an increased elastic Young’s modulus post-treatment in both MCF-7 and SKBR-3 cells. The results showed that the post-treatment spreading rate was significantly decreased in both types of breast cancer, suggesting a lower metastatic potential. Additionally, treated cells required greater adhesion forces to detach from the ECM, thus preventing detachment events of cancer cells from the ECM, and therefore, the probability of cell motility, migration, and metastasis was confined. Furthermore, post-detachment and post-treatment vinculin levels were increased, indicating tighter cell–ECM junctions, hence limiting the probability of cell detachment and, therefore, cell motility and migration.

Complete Model of Vinculin Suggests the Mechanism of Activation by Helical Super-Bundle Unfurling

To shed light onto the activation mechanism of vinculin, we carried out a detailed refinement of chicken vinculin and compared it to the human protein which is greater than 95% identical. Refinement resulted in a complete and significantly improved model. This model includes important elements such as a pro-rich strap region (PRR) and C-terminus. The conformation of the PRR stabilized by its inter- and intra-molecular contacts shows a dynamic, but relatively stable motif that constitutes a docking platform for multiple molecules. The contact of the C-terminus with the PRR suggests that phosphorylation of Tyr1065 might control activation and membrane binding. Improved electron densities showed the presence of large solvent molecules such as phosphates/sulfates and a head-group of PIP2. The improved model allowed for a computational stability analysis to be performed by the program Corex/Best which located numerous hot-spots of increased and decreased stability. Proximity of the identified binding sites for regulatory partners involved in inducing or suppressing the activation of vinculin to the unstable elements sheds new light onto the activation pathway and differential activation. This stability analysis suggests that the activation pathway proceeds by unfurling of the super-bundle built from four bundles of helices without separation of the Vt region (840-1066) from the head. According to our mechanism, when activating proteins bind at the strap region a separation of N and C terminal bundles occurs, followed by unfurling of the super-bundle and flattening of the general shape of the molecule, which exposes the interaction sites for binding of auxiliary proteins.

Combined Toxicity of Gas Plasma Treatment and Nanoparticles Exposure in Melanoma Cells In Vitro

Despite continuous advances in therapy, cancer remains a deadly disease. Over the past years, gas plasma technology emerged as a novel tool to target tumors, especially skin. Another promising anticancer approach are nanoparticles. Since combination therapies are becoming increasingly relevant in oncology, both gas plasma treatment and nanoparticle exposure were combined. A series of nanoparticles were investigated in parallel, namely, silica, silver, iron oxide, cerium oxide, titanium oxide, and iron-doped titanium oxide. For gas plasma treatment, the atmospheric pressure argon plasma jet kINPen was utilized. Using three melanoma cell lines, the two murine non-metastatic B16F0 and metastatic B16F10 cells and the human metastatic B-Raf mutant cell line SK-MEL-28, the combined cytotoxicity of both approaches was identified. The combined cytotoxicity of gas plasma treatment and nanoparticle exposure was consistent across all three cell lines for silica, silver, iron oxide, and cerium oxide. In contrast, for titanium oxide and iron-doped titanium oxide, significantly combined cytotoxicity was only observed in B16F10 cells.

Applications of Nanomaterials for Theranostics of Melanoma

Melanoma is an aggressive form of skin cancer with a very high mortality rate. Early diagnosis of the disease, the utilization of more potent pharmacological agents, and more effective drug delivery systems are essential to achieve an optimal treatment plan. The applications of nanotechnology to improve therapeutic efficacy and early diagnosis for melanoma treatment have received great interest among researchers and clinicians. In this review, we summarize the recent progress of utilizing various nanomaterials for theranostics of melanoma. The key importance of using nanomaterials for theranostics of melanoma is to improve efficacy and reduce side effects, ensuring safe implementation in clinical use. As opposed to conventional in vitro diagnostic methods, in vivo medical imaging technologies have the advantages of being a type of non-invasive, real-time monitoring. Several common nanoparticles, including ultrasmall superparamagnetic iron oxide nanoparticles, silica nanoparticles, and carbon-based nanoparticles, have been applied to deliver chemotherapeutic agents for the theranostics of melanoma. The application of nanomaterials for theranostics in molecular imaging (MRI, PET, US, OI, etc.) plays an important role in targeting drug delivery of melanoma, by monitoring the distribution site of the molecular imaging probe and the therapeutic drug in the body in real-time. Hence, it is worthwhile to anticipate the approval of these nanomaterials for theranostics in molecular imaging by the US Food and Drug Administration in clinical trials.

Identification of very small cancer stem cells expressing hallmarks of pluripotency in B16F10 melanoma cells and their reoccurrence in B16F10-derived clones

Melanoma is characterized by high heterogeneity and plasticity, most likely due to the presence of mutated melanocyte stem cells or immature progenitor cells in the skin that serves as precursors to melanoma. In the present study, for the first time, we identified rare cells in the murine melanoma B16F10, and human A2058 and SK-MEL-28 cell lines that express pluripotency markers, including Oct4, Nanog, Sox2 and a marker of melanoma cancer cells (ALDH1/2). These cells are very small with round morphology and they grow onto melanoma cells, thereby demonstrating feeder layer dependence similar to that of other pluripotent cells. These cells underwent self-renewal, symmetric and asymmetric division. We called these cells murine very small cancer stem cells (VSCSC). VSCSC were also found in B16F10-derived clones after 3-5 consecutive passages, where they occur as single cells or as small colonies, nevertheless, always using melanoma cells as feeders. These cells formed melanospheres enriched with Oct4-and ALDH1/2-positive cells. We also evaluated the possible effect of VSCSC that presented in the parental cell line (B16F10) and in clones based on their functional characteristics. We found that VCSCS present in the B16F10 cell line reappearing in their clones were required for continuous tumor growth and were responsible for melanoma cell heterogeneity and plasticity rather than directly affecting functional characteristics of melanoma cells. Our data, together with those of previous reports suggested the existence of melanoma-competent melanocyte stem cells, which corroborate the hypothesis of the existence of tumor-initiating cells and cancer stem cell hierarchies, at least in melanoma.

Correlation of histopathologic characteristics to protein expression and function in malignant melanoma

Background

Metastatic melanoma is still one of the most prevalent skin cancers, which upon progression has neither a prognostic marker nor a specific and lasting treatment. Proteomic analysis is a versatile approach with high throughput data and results that can be used for characterizing tissue samples. However, such analysis is hampered by the complexity of the disease, heterogeneity of patients, tumors, and samples themselves. With the long term aim of quest for better diagnostics biomarkers, as well as predictive and prognostic markers, we focused on relating high resolution proteomics data to careful histopathological evaluation of the tumor samples and patient survival information.

Patients and methods

Regional lymph node metastases obtained from ten patients with metastatic melanoma (stage III) were analyzed by histopathology and proteomics using mass spectrometry. Out of the ten patients, six had clinical follow-up data. The protein deep mining mass spectrometry data was related to the histopathology tumor tissue sections adjacent to the area used for deep-mining. Clinical follow-up data provided information on disease progression which could be linked to protein expression aiming to identify tissue-based specific protein markers for metastatic melanoma and prognostic factors for prediction of progression of stage III disease.

Results

In this feasibility study, several proteins were identified that positively correlated to tumor tissue content including IF6, ARF4, MUC18, UBC12, CSPG4, PCNA, PMEL and MAGD2. The study also identified MYC, HNF4A and TGFB1 as top upstream regulators correlating to tumor tissue content. Other proteins were inversely correlated to tumor tissue content, the most significant being; TENX, EHD2, ZA2G, AOC3, FETUA and THRB. A number of proteins were significantly related to clinical outcome, among these, HEXB, PKM and GPNMB stood out, as hallmarks of processes involved in progression from stage III to stage IV disease and poor survival.

Conclusion

In this feasibility study, promising results show the feasibility of relating proteomics to histopathology and clinical outcome, and insight thus can be gained into the molecular processes driving the disease. The combined analysis of histological features including the sample cellular composition with protein expression of each metastasis enabled the identification of novel, differentially expressed proteins. Further studies are necessary to determine whether these putative biomarkers can be utilized in diagnostics and prognostic prediction of metastatic melanoma.

New insights into vinculin function and regulation

Vinculin is a cytoplasmic actin-binding protein enriched in focal adhesions and adherens junctions that is essential for embryonic development. Much is now known regarding the role of vinculin in governing cell-matrix adhesion. In the past decade that the crystal structure of vinculin and the molecular details for how vinculin regulates adhesion events have emerged. The recent data suggests a critical function for vinculin in regulating integrin clustering, force generation, and strength of adhesion. In addition to an important role in cell-matrix adhesion, vinculin is also emerging as a regulator of apoptosis, Shigella entry into host cells, and cadherin-based cell-cell adhesion. A close inspection of this work reveals that there are similarities between vinculin's role in focal adhesions and these processes and also some intriguing differences.

Focal adhesion plaque associated cytoskeletons are involved in the invasion and metastasis of human colorectal carcinoma

The protein and mRNA expression of focal adhesion plaque associated cytoskeletons, including talin, vinculin, paxillin, and tensin, was studied using immunofluorescence in combination with confocal laser scanning microscopy and fluorescent quantitative polymerase chain reaction in 41 matched samples of human normal colorectal mucosae, primary colorectal adenocarcinomas, and 19 separate lymph node metastases. All specimens showed expression. The results showed talin, vinculin, tensin, and paxillin expression were correlated with carcinogenesis, invasion, and metastasis of colorectal carcinoma (CRC). Talin, vinculin, and tensin underwent downregulation while paxillin went up. So these cytoskeletons may play bidirectional regulating roles during the progression of CRC.

Vinculin regulates cell-surface E-cadherin expression by binding to beta-catenin

Vinculin was identified as a component of adherens junctions 30 years ago, yet its function there remains elusive. Deletion studies are consistent with the idea that vinculin is important for the organization of cell-cell junctions. However, this approach removes vinculin from both cell-matrix and cell-cell adhesions, making it impossible to distinguish its contribution at each site. To define the role of vinculin in cell-cell junctions, we established a powerful short hairpin-RNA-based knockdown/substitution model system that perturbs vinculin preferentially at sites of cell-cell adhesion. When this system was applied to epithelial cells, cell morphology was altered, and cadherin-dependent adhesion was reduced. These defects resulted from impaired E-cadherin cell-surface expression. We have investigated the mechanism for the effects of vinculin and found that the reduced surface E-cadherin expression could be rescued by introduction of vinculin, but not of a vinculin A50I substitution mutant that is defective for beta-catenin binding. These findings suggest that an interaction between beta-catenin and vinculin is crucial for stabilizing E-cadherin at the cell surface. This was confirmed by analyzing a beta-catenin mutant that fails to bind vinculin. Thus, our study identifies vinculin as a novel regulator of E-cadherin function and provides important new insight into the dynamic regulation of adherens junctions.

Suppression of cancer phenotypes through a multifunctional actin-binding protein, calponin, that attacks cancer cells and simultaneously protects the host from invasion

Quantitative and/or qualitative alteration of actin cytoskeletal molecules, involved in the regulation of cellular dynamic functions, should be intimately related with cancer phenotypes. Based on several lines of experimental evidence from our group, and others, this report proposes a strategy to simultaneously attack cancer cells and protect the host from cancer invasion, with one molecule. Calponin h1, an actin-stabilizing protein that is also intimately related to signal transduction, is very often suppressed in vascular smooth muscle cells of malignant human tumors and in mesothelial cells by coexisting cancer cells. We generated mice deficient for calponin h1, exhibiting fragility in blood vessels and peritoneal membranes. Hematogenous cancer metastasis occurred more easily in the calponin h1-deficient mice than in wild-type mice, and the peritoneal dissemination was extremely enhanced. The fragility was rescued by the exogenous introduction of the calponin h1 gene into mesothelial cells of the peritoneum. Furthermore, calponin h1 gene transfer into several transformed cell lines resulted in a suppression of malignancy. The peritoneal dissemination of intraperitoneally-injected B16-F10 cells was suppressed by the calponin h1 gene, given to target both cancer cells and the mesothelial cells of the host. The multifunctional nature of the molecule, as a machinery player of cytoskeleton and mediator of signal transduction, probably resulted in a favorable recipient-discriminating effect on cancerous and normal cells. Thus, we believe that if we use adequate multifunctional molecules for therapy, it is possible to simultaneously suppress cancer phenotypes and protect normal cells from the attack of cancer cells.

The endogenous progesterone metabolite, 5a-pregnane-3,20-dione, decreases cell-substrate attachment, adhesion plaques, vinculin expression, and polymerized F-actin in MCF-7 breast cancer cells

Tumorous human breast tissue readily converts progesterone to 5alpha-pregnane-3,20-dione (5alphaP), and this metabolite has been shown to stimulate proliferation and to decrease adhesion of MCF-7 breast cancer cells. To determine the mechanisms of action of 5alphaP on cell adhesion, MCF-7 cells were grown without or with 5alphaP (10(-9)-10(-5) M), and the effects on cell and nuclear morphology, adhesion plaques, vinculin and actin expression, actin polymerization, and microfilament distribution were examined by immunohistochemistry, morphometry (using confocal microscopy and digital computer imaging analysis), and Western blotting. Treatment of cells with 10(-9)-10(-6) M 5alphaP resulted in dose-dependent decreases in cell area, cell-to-cell contacts, and attachment to the substratum, and increases in variation in nuclear area. These changes in the 5alphaP-treated cells were accompanied by decreases in vinculin-containing adhesion plaques, vinculin expression, polymerized actin stress fibers, and decreases in insoluble and increases in soluble actin fractions. The results suggest that the observed decreases in adhesion and increases in cell proliferation following 5alphaP treatment may be owing to depolymerization of actin and decreased expression of actin and vinculin. We conclude that the endogenous progesterone metabolite, 5alphaP, may be involved in promoting breast neoplasia and metastasis by affecting adhesion and cytoskeletal molecules.

A phospholipase D and protein kinase C inhibitor blocks the spreading of murine mammary adenocarcinoma cells altering f-actin and beta1-integrin point contact distribution

Spreading is a critical process involved in motility and growth of tumor cells during the metastatic cascade. Focal adhesion kinase, src-proteins and PKC have been reported to participate in the regulation of cytoskeleton organization in both normal and transformed cells during spreading. The role of other signaling enzymes such as PLD and PAP has not been studied during spreading in tumor cells. We now show that the spreading of murine mammary adenocarcinoma LM3 cells was significantly reduced by n-butanol, a PLD and PKC inhibitor, with a maximal inhibition of 54% (p < 0.001) in both the presence and absence of serum, as measured by phase-contrast microscopy. PMA only stimulated cell spreading over the control in the absence of serum and n-butanol inhibition was completely reversed by PMA treatment in both conditions. PA, the product of PLD activity, stimulated LM3 cell spreading and the same effect was observed with staurosporine. Spreading was enhanced when cells were seeded on collagen-IV- or fibronectin-coated surfaces and n-butanol could inhibit both integrin-derived signals. Cell spreading inhibition correlated with the absence of f-actin bundles and fewer beta1-integrin point contacts as determined by double immunofluorescence microscopy. In addition, n-butanol inhibited the proliferation of LM3 cells in the presence of serum (p < 0.01). These results suggest that beta1-integrin and f-actin/point contact assembly, involved in spreading and proliferation, require the participation of PLD-PKC regulatory pathways in LM3 cells.

Inhibition of tumor cell haptotaxis by sodium D-glucaro-delta-lactam (ND2001)

We used the Boyden chamber system to investigate the mechanism by which the antimetastatic agent sodium D-glucaro-delta-lactam (ND2001) inhibits tumor cell invasion, and by establishing what ND2001 did not achieve, we were able to pinpoint the areas in which it was successful as an inhibitor. ND2001 did not inhibit cell adhesion of a highly metastatic B16 melanoma variant (the B16 variant) to the reconstituted basal membrane Matrigel, nor did it affect the production or activity of basal membrane-degrading type i.v. collagenase, but, in the Boyden chamber, ND2001 inhibited cell migration of the B16 variant toward a chemoattractant, laminin, on the lower surface of a Matrigel-free filter set (haptotaxis). Lewis lung carcinoma (3LL) cells that had been treated with ND2001 also exhibited hardly any haptotaxis, although the cells showed no alteration in behavior during cell adhesion to Matrigel. Since ND2001 did succeed in inhibiting the pulmonary metastases of the B16 variant and 3LL, we infer that inhibition of the metastases by ND2001 in these tumors is likely to be due to the inhibition of haptotactic migration.

Medical aspects of the actin cytoskeleton

The actin cytoskeleton is affected in many disease states. The mechanisms by which altered structure or expression of actin or of actin-binding proteins cause specific defects are beginning to emerge. Notable recent findings concern the roles in tumor suppression of proteins that link actin to the cell membrane, the specific functions of actin isoforms in cells with a developed contractile apparatus, and the variety of complications caused by release of filamentous actin into extracellular fluids.

Intracellular localization and biochemical function of variant beta-actin, which inhibits metastasis of B16 melanoma

We analyzed the biochemical nature of beta m-actin protein found in mouse B16 melanoma. When we carried out immunostaining with the antibody specific to beta m-actin, filamentous immunofluorescence was observed in B16-F1, a low-metastatic cell line expressing beta m-actin, but not in highly metastatic B16-F10 that did not express beta m-actin. When a purified actin fraction containing beta m-actin was polymerized and immunoprecipitated with anti-beta m-actin antibody, the immunoprecipitate contained beta m-, beta- and gamma-actin. This indicated that the beta m-actin was incorporated into an actin filament together with beta- and gamma-actin in vitro, and this phenomenon was consistently suggested by cellular double immunostaining with anti-beta m-actin and common anti-actin antibody. When the actin fraction containing beta m-actin under a regular depolymerizing condition was subjected to immuno-adsorption assay using anti-beta m antibody and protein-A Sepharose, the immunoadsorbed aggregates contained beta m-, beta- and gamma-actin. This indicates that the actin fraction was not completely depolymerized and contained beta m-actin-containing oligomers, which were too small to be precipitated with anti-beta m-actin antibody alone. The incomplete depolymerization of the beta m-actin-containing fraction was also suggested by the much lower DNase 1 inhibition activity of the beta m-actin-containing fraction than that of beta- and gamma-actin fraction. Furthermore, a DNase 1 binding assay showed that cytoplasmic supernatant prepared from B16-F1 under a low-ionic condition contained less monomeric actin than the cytoplasmic preparation from B16-F10. These results suggested that beta m-actin protein in B16 melanoma probably inhibits the dynamic conversion between the monomeric and polymerized forms of actin, leading to a decrease in cell motility and consequently the suppression of invasiveness and metastasis.

A variant actin (beta m) reduces metastasis of mouse B16 melanoma

We recently reported an acidic actin co-expressed with beta and gamma actin in mouse B16 melanoma, whose expression was inversely correlated with the metastatic potential. The cDNA for this actin is slightly different from the hitherto recognized mouse beta actin cDNA, and we designated it beta m actin. In order to directly investigate the effects of beta m actin on metastasis, we transfected the beta m actin cDNA into a re-cloned B16-BL6 cell line which is more invasive than the highly metastatic cell line, B16-F10; we have already reported the suppressive effect of beta m actin on the invasiveness of B16-F10. Here we report on the decline in the metastatic ability of beta m-transfected cells. In the beta m-transfected B16-BL6 cell line, we observed an increase in the organization of actin stress fibers, accompanied by a decrease in metastasis to the lung, in the invasion of collagen gels, in in vivo invasiveness, and in cell migration on a glass plate covered with colloidal gold particles. We observed no correlation of beta m actin expression either with cell attachment to Matrigel, or with type-IV collagenase expression. These results suggest that beta m actin can play a role in reducing the invasiveness of mouse B16 melanoma, most probably through decreasing cell motility, which may thus result in suppression of the metastatic ability of cells.