Adenoviral gene transfer of beta3 integrin subunit induces conversion from radial to vertical growth phase in primary human melanoma

Synthesis and Biological Evaluation of Cyclobutane-Based β3 Integrin Antagonists: A Novel Approach to Targeting Integrins for Cancer Therapy

The Arg-Gly-Asp (RGD)-binding family of integrin receptors, and notably the β3 subfamily, are key to multiple physiological processes involved in tissue development, cancer proliferation, and metastatic dissemination. While there is compelling preclinical evidence that both αvβ3 and αIIbβ3 are important anticancer targets, most integrin antagonists developed to target the β3 integrins are highly selective for αvβ3 or αIIbβ3. We report the design, synthesis, and biological evaluation of a new structural class of ligand-mimetic β3 integrin antagonist. These new antagonists combine a high activity against αvβ3 with a moderate affinity for αIIbβ3, providing the first evidence for a new approach to integrin targeting in cancer.

Therapeutic targeting of anoikis resistance in cutaneous melanoma metastasis

The acquisition of resistance to anoikis, the cell death induced by loss of adhesion to the extracellular matrix, is an absolute requirement for the survival of disseminating and circulating tumour cells (CTCs), and for the seeding of metastatic lesions. In melanoma, a range of intracellular signalling cascades have been identified as potential drivers of anoikis resistance, however a full understanding of the process is yet to be attained. Mechanisms of anoikis resistance pose an attractive target for the therapeutic treatment of disseminating and circulating melanoma cells. This review explores the range of small molecule, peptide and antibody inhibitors targeting molecules involved in anoikis resistance in melanoma, and may be repurposed to prevent metastatic melanoma prior to its initiation, potentially improving the prognosis for patients.

Aptamer-based Advances in Skin Cancer Research

Cancer diseases have been one of the biggest health threats for the last two decades. Approximately 9% of all diagnosed cancers are skin cancers, including melanoma and non-melanoma. In all cancer cases, early diagnosis is essential to achieve efficient treatment. New solutions and advanced techniques for rapid diagnosis are constantly being sought. Aptamers are single-stranded RNA or DNA synthetic sequences or peptides, which offer novel possibilities to this area of research by specifically binding selected molecules, the so-called cancer biomarkers. Nowadays, they are widely used as diagnostic probes in imaging and targeted therapy. In this review, we have summarized the recently made advances in diagnostics and treatment of skin cancers, which have been achieved by combining aptamers with basic or modern technologies.

Modelling the Tumor Microenvironment: Recapitulating Nano- and Micro-Scale Properties that Regulate Tumor Progression

Breast cancer remains a significant burden with 1 in 8 women affected and metastasis posing a significant challenge for patient survival. Disease progression involves remodeling of the extracellular matrix (ECM). In breast cancer, tissue stiffness increases owing to an increase in collagen production by recruited cancer-associated fibroblasts (CAFs). These stromal modifications are notable during primary tumor growth and have a dualistic action by creating a hard capsule to prevent penetration of anti-cancer therapies and forming a favorable environment for tumor progression. Remodeling of the tumor microenvironment immediately presented to cells can include changes in protein composition, concentration and structural arrangement and provides the first mechanical stimuli in the metastatic cascade. Not surprisingly, metastatic cancer cells possess the ability to mechanically adapt, and their adaptability ensures not only survival but successful invasion within altered environments. In the past decade, the importance of the microenvironment and its regulatory role in diseases have gained traction and this is evident in the shift from plastic culture to the development of novel biomaterials that mimic in vivo tissue. With these advances, elucidations can be made into how ECM remodeling and more specifically, altered cell-ECM adhesions, regulate tumor growth and cancer cell plasticity. Such enabling tools in mechanobiology will identify fundamental mechanisms in cancer progression that eventually help develop preventative and therapeutic treatment from a clinical perspective. This review will focus on current platforms engineered to mimic the micro and nano-properties of the tumor microenvironment and subsequent understanding of mechanically regulated pathways in cancer.

Translating Molecules into Imaging—The Development of New PET Tracers for Patients with Melanoma

Melanoma is a deadly disease that often exhibits relentless progression and can have both early and late metastases. Recent advances in immunotherapy and targeted therapy have dramatically increased patient survival for patients with melanoma. Similar advances in molecular targeted PET imaging can identify molecular pathways that promote disease progression and therefore offer physiological information. Thus, they can be used to assess prognosis, tumor heterogeneity, and identify instances of treatment failure. Numerous agents tested preclinically and clinically demonstrate promising results with high tumor-to-background ratios in both primary and metastatic melanoma tumors. Here, we detail the development and testing of multiple molecular targeted PET-imaging agents, including agents for general oncological imaging and those specifically for PET imaging of melanoma. Of the numerous radiopharmaceuticals evaluated for this purpose, several have made it to clinical trials and showed promising results. Ultimately, these agents may become the standard of care for melanoma imaging if they are able to demonstrate micrometastatic disease and thus provide more accurate information for staging. Furthermore, these agents provide a more accurate way to monitor response to therapy. Patients will be able to receive treatment based on tumor uptake characteristics and may be able to be treated earlier for lesions that with traditional imaging would be subclinical, overall leading to improved outcomes for patients.

Anandamide-Modulated Changes in Metabolism, Glycosylation Profile and Migration of Metastatic Melanoma Cells

Simple Summary

Anandamide (AEA) belongs to the group of endocannabinoids and possesses various regulatory properties in physiological as well as pathological processes occurring in the organism. In this research some basic biological tests were applied to investigate AEA-induced changes in cell metabolism and motility, as well as advanced biophysical methods for the determination of the differences in the cell glycosylation profile on a highly dangerous model of melanoma skin cancer, for which an effective therapy is not yet available. Our research suggests that anandamide treatment of metastatic melanoma cells increases the cell metabolism which leads to the reduction in the metastatic potential of cells in terms of the cell glycosylation profile and cell migration. In the view of our research, it can be presumed that anandamide usage in the combined therapy of advanced melanoma would be an advantage for the patient.

Abstract

An effective therapy for advanced melanoma, a skin cancer with the highest mortality, has not yet been developed. The endocannabinoid system is considered to be an attractive target for cancer treatment. The use of endocannabinoids, such as anandamide (AEA), is considered to be much greater than as a palliative agent. Thus, we checked its influence on various signaling pathways in melanoma cells. Our investigation was performed on four commercial cell lines derived from different progression stages (radial WM35 and vertical WM115 growth phases, lymph node WM266-4 metastasis, solid tumor A375-P metastasis). Cell viability, glucose uptake, quantification of reactive oxygen species production, expression of selected genes encoding glycosyltransferases, quantification of glycoproteins production and changes in the glycosylation profile and migration, as well as in cell elastic properties were analyzed. The cell glycosylation profile was investigated using the biophysical profiling method—the quartz crystal microbalance with dissipation monitoring (QCM-D). Anandamide treatment of only metastatic cells resulted in: an increase in the cell metabolism, a decrease in GFAT-1 and DPM1 expression, followed by a decrease in L1-CAM glycoprotein production, which further influenced the reduction in the cell glycosylation profile and migration. Considering our results, AEA usage is highly recommended in the combined therapy of advanced melanoma.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

RGD engineered dendrimer nanotherapeutic as an emerging targeted approach in cancer therapy

A bird's eye view is now demanded in the area of cancer research to suppress the suffering of cancer patient and mediate the lack of treatment related to chemotherapy. Chemotherapy is always preferred over surgery or radiation therapy, but they never met the patient's demand of safe medication. Targeted therapy has now been in research that could hinder the unnecessary effect of drug on normal cells but could affect the tumor cells in much efficient manner. Angiogenesis is process involved in development of new blood vessel that nourishes tumor growth. Integrin receptors are over expressed on cancer cells that play vital role in angiogenesis for growth and metastasis of tumor cell. A delivery of RGD based peptide to integrin targeted site could help in its successful binding and liberation of drug in tumor vasculature. Dendrimers, in addition to its excellent pharmacokinetic properties also helps to carry targeting ligand to site of tumor by successfully conjugating with them. The aim of this review is to bring light upon the role of integrin in cancer progression, interaction of RGD to integrin receptor and more importantly the RGD-dendrimer based targeted therapy for the treatment of various cancers.

Homo and heterobimetallic palladium and platinum complexes bearing μ-diphosphane bridges involved in biological studies

Given the increasing reports of well-defined bimetallic molecular complexes as potential anticancer agents in the last decades, along with the prevalence of platinum in anticancer therapy, we report here a detailed survey of bimetallic platinum and palladium complexes investigated as potential anticancer agents. Specifically, we will concentrate on the synthesis, characterisation and biological (anticancer) studies of a sub-class of these agents, namely homo and heterobimetallic complexes bearing a bridging phosphane ligand of the type: [L_nM₁(μ-R₂P(CH₂)_nPR₂)M₂L_m] (where M₁ is platinum or palladium, M₂ is any other transition metal, R = alkyl or aryl substituents, L_n or L_m are co-ligands, n = 1-6). We will review the in vitro and in vivo activities and any mechanistic anticancer studies of these complexes with a view of trying to delineate patterns in biological activity and structure-activity relationships (SAR). We do not include the review of bimetallic complexes in this class that have not undergone any anticancer testing, nor those that have been involved in other biological investigations unrelated to cancer studies.

The role of integrins in melanoma: a review

Integrins are the major family of cell adhesion receptors in humans and essential for a wide range of normal physiology, including formation and maintenance of tissue structure integrity, cell migration, proliferation, and differentiation. Integrins also play a prominent role in tumor growth and metastasis. Translational research has tried to define the contribution of integrins to the phenotypic aggressiveness of melanoma because such knowledge is clinically useful. For example, differential expression of integrins in primary cutaneous melanoma can be used to distinguish indolent from aggressive, prometastatic melanoma. Recent studies have shown that gene expression-based testing of patient-derived melanoma tissue is feasible, and molecular tests may fully replace interventional surgical methods such as sentinel lymph node biopsies in the future. Because of their central role in mediating invasion and metastasis, integrins are likely to be useful biomarkers. Integrins are also attractive candidate targets for interventional therapy. This article focuses on the role of integrins in melanoma and highlights recent advances in the field of translational research.

Mass Spectrometry-Based Proteomic Characterization of Cutaneous Melanoma Ectosomes Reveals the Presence of Cancer-Related Molecules

Cutaneous melanoma (CM) is an aggressive type of skin cancer for which effective biomarkers are still needed. Recently, the protein content of extracellular vesicles (ectosomes and exosomes) became increasingly investigated in terms of its functional role in CM and as a source of novel biomarkers; however, the data concerning the proteome of CM-derived ectosomes is very limited. We used the shotgun nanoLC-MS/MS approach to the profile protein content of ectosomes from primary (WM115, WM793) and metastatic (WM266-4, WM1205Lu) CM cell lines. Additionally, the effect exerted by CM ectosomes on recipient cells was assessed in terms of cell proliferation (Alamar Blue assay) and migratory properties (wound healing assay). All cell lines secreted heterogeneous populations of ectosomes enriched in the common set of proteins. A total of 1507 unique proteins were identified, with many of them involved in cancer cell proliferation, migration, escape from apoptosis, epithelial-mesenchymal transition and angiogenesis. Isolated ectosomes increased proliferation and motility of recipient cells, likely due to the ectosomal transfer of different cancer-promoting molecules. Taken together, these results confirm the significant role of ectosomes in several biological processes leading to CM development and progression, and might be used as a starting point for further studies exploring their diagnostic and prognostic potential.

A Penicillin Derivative Exerts an Anti-Metastatic Activity in Melanoma Cells Through the Downregulation of Integrin αvβ3 and Wnt/β-Catenin Pathway

The synthetic triazolylpeptidyl penicillin derivative, named TAP7f, has been previously characterized as an effective antitumor agent in vitro and in vivo against B16-F0 melanoma cells. In this study, we investigated the anti-metastatic potential of this compound on highly metastatic murine B16-F10 and human A375 melanoma cells. We found that TAP7f inhibited cell adhesion, migration and invasion in a dose-dependent manner. Additionally, we demonstrated that TAP7f downregulated integrin αvβ3 expression and Wnt/β-catenin pathway, a signaling cascade commonly related to tumor invasion and metastasis. Thus, TAP7f reduced both the enzymatic activity and the expression levels of matrix-metalloproteinases-2 and -9 in a time dependent manner. Moreover, TAP7f inhibited the expression of the transcription factor Snail and the mesenchymal markers vimentin, and N-cadherin, and up-regulated the expression of the epithelial marker E-cadherin, suggesting that the penicillin derivative affects epithelial-mesenchymal transition. Results obtained in vitro were supported by those obtained in a B16-F10-bearing mice metastatic model, that showed a significant TAP7f inhibition of lung metastasis. These findings suggest the potential of TAP7f as a chemotherapeutic agent for the treatment of metastatic melanoma.

Characterization of glycolysis-related gene expression in malignant melanoma

Malignant melanoma exhibits a distinct metabolic phenotype with high glycolytic activity. Previously, we have shown that glucose transporter isoform 1 (GLUT1) favors growth and metastasis of malignant melanoma. In this study, we investigated the expression of GLUT1 and the further glycolysis-related genes hexokinase 1 and 2 (HK1, HK2), lactate dehydrogenase A (LDH-A) and monocarboxylate transporters 1 and 4 (MCT1, MCT4) in eleven human melanoma cell lines under normoxic and hypoxic conditions. Furthermore, a set of 25 human malignant melanoma tissue samples was analyzed. Under hypoxic conditions, we could observe a significant upregulation of hypoxia-inducible factor 1 alpha (HIF-1a) target genes GLUT1, HK2 and LDH-A, but not MCT4. While under normoxic conditions the expression of glycolysis-related genes showed no correlation with origin or BRAF mutation status, GLUT1 expression was significantly elevated in metastatic and BRAF-V600E mutated melanoma cell lines under hypoxic conditions. Furthermore, GLUT1 expression in human melanoma tissue samples correlated significantly with HK1, LDH-A and MCT1 expression, confirming a glycolytic phenotype. Notably, Cyclin D1 expression, which is used as a prognostic marker for the outcome of melanoma patients, as it is associated with proliferation and invasiveness of melanoma, significantly correlated with GLUT1, HK1, LDH-A and MCT1 expression. In summary, our findings provide further evidence that enhanced glycolytic activity in melanoma favors disease progression and is an attractive therapeutic target for this highly aggressive tumor.

Leucurogin and melanoma therapy

Leucurogin is an ECD disintegrin-like protein, cloned from Bothrops leucurus venom gland. This new protein, encompassing the disintegrin region of a PIII metalloproteinase, is produced by recombinant technology and its biological and functional activity was partially characterized in this study. Biological activity was characterized in vitro using human fibroblasts. Functional activity of leucurogin was analysed in vitro and in vivo with murine B16F10 Nex-2 and human melanoma BLM cells. The results show that leucurogin inhibits cellular processes dependent on collagen type I. In a competition assay with collagen, leucurogin inhibits, in a dose-dependent manner, the adhesion of fibroblast to collagen. At 10 μM leucurogin reduces adhesion (40%) and migration (70%) of hFb and inhibits migration (32%) and proliferation (65%) of BLM cells. At 2.5 μM leucurogin inhibits 80% cell proliferation of B16F10 Nex-2 melanoma cells. At 4.8 μM leucurogin inhibits, in vitro, the vascular structures formation by endothelial cells by 66%. Leucurogin, injected intraperitoneally, i.p. (5 μg/animal, two-month old C57/Bl6 male mice) on alternate days for 15 days, inhibits lung metastasis of B16F10 Nex-2 cells by 70-75%. In the treatment of human melanoma, grafted intradermally in the nude mice flank, leucurogin (7.5 μg/kg in alternate days during 17 days) inhibits tumor growth by more than 40%. Leucurogin can be considered a promising agent for melanoma treatment.

Rationally Designed 3D Hydrogels Model Invasive Lung Diseases Enabling High-Content Drug Screening

Cell behavior is highly dependent upon microenvironment. Thus, to identify drugs targeting metastatic cancer, screens need to be performed in tissue mimetic substrates that allow cell invasion and matrix remodeling. A novel biomimetic 3D hydrogel platform that enables quantitative analysis of cell invasion and viability at the individual cell level is developed using automated data acquisition methods with an invasive lung disease (lymphangioleiomyomatosis, LAM) characterized by hyperactive mammalian target of rapamycin complex 1 (mTORC1) signaling as a model. To test the lung-mimetic hydrogel platform, a kinase inhibitor screen is performed using tuberous sclerosis complex 2 (TSC2) hypomorphic cells, identifying Cdk2 inhibition as a putative LAM therapeutic. The 3D hydrogels mimic the native niche, enable multiple modes of invasion, and delineate phenotypic differences between healthy and diseased cells, all of which are critical to effective drug screens of highly invasive diseases including lung cancer.

The functional role of integrins during intra- and extravasation within the metastatic cascade

Formation of distant metastases is by far the most common cause of cancer-related deaths. The process of metastasis formation is complex, and within this complex process the formation of migratory cells, the so called epithelial mesenchymal transition (EMT), which enables cancer cells to break loose from the primary tumor mass and to enter the bloodstream, is of particular importance. To break loose from the primary cancer, cancer cells have to down-regulate the cell-to-cell adhesion molecuIes (CAMs) which keep them attached to neighboring cancer cells. In contrast to this downregulation of CAMS in the primary tumor, cancer cells up-regulate other types of CAMs, that enable them to attach to the endothelium in the organ of the future metastasis. During EMT, the expression of cell-to-cell and cell-to-matrix adhesion molecules and their down- and upregulation is therefore critical for metastasis formation. Tumor cells mimic leukocytes to enable transmigration of the endothelial barrier at the metastatic site. The attachment of leukocytes/cancer cells to the endothelium are mediated by several CAMs different from those at the site of the primary tumor. These CAMs and their ligands are organized in a sequential row, the leukocyte adhesion cascade. In this adhesion process, integrins and their ligands are centrally involved in the molecular interactions governing the transmigration. This review discusses the integrin expression patterns found on primary tumor cells and studies whether their expression correlates with tumor progression, metastatic capacity and prognosis. Simultaneously, further possible, but so far unclearly characterized, alternative adhesion molecules and/or ligands, will be considered and emerging therapeutic possibilities reviewed.

Integrin-targeted quantitative optoacoustic imaging with MRI correlation for monitoring a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma

PURPOSE

To investigate αvβ3-integrin-targeted optoacoustic imaging and MRI for monitoring a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma.

MATERIALS AND METHODS

Human BRAF V600E-positive melanoma xenograft (A375)-bearing Balb/c nude mice (n = 10) were imaged before (day 0) and after (day 7) a BRAF/MEK inhibitor combination therapy (encorafenib, 1.3 mg/kg/d; binimetinib, 0.6 mg/kg/d, n = 5) or placebo (n = 5), respectively. Optoacoustic imaging was performed on a preclinical system unenhanced and 5 h after i. v. injection of an αvβ3-integrin-targeted fluorescent probe. The αvβ3-integrin-specific tumor signal was derived by spectral unmixing. For morphology-based tumor response assessments, T2w MRI data sets were acquired on a clinical 3 Tesla scanner. The imaging results were validated by multiparametric immunohistochemistry (ß3 -integrin expression, CD31 -microvascular density, Ki-67 -proliferation).

RESULTS

The αvβ3-integrin-specific tumor signal was significantly reduced under therapy, showing a unidirectional decline in all animals (from 7.98±2.22 to 1.67±1.30; p = 0.043). No significant signal change was observed in the control group (from 6.60±6.51 to 3.67±1.93; p = 0.500). Immunohistochemistry revealed a significantly lower integrin expression (ß3: 0.20±0.02 vs. 0.39±0.05; p = 0.008) and microvascular density (CD31: 119±15 vs. 292±49; p = 0.008) in the therapy group. Tumor volumes increased with no significant intergroup difference (therapy: +107±42 mm3; control +112±44mm3, p = 0.841). In vivo blocking studies with αvβ3-integrin antagonist cilengitide confirmed the target specificity of the fluorescent probe.

CONCLUSIONS

αvβ3-integrin-targeted optoacoustic imaging allowed for the early non-invasive monitoring of a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma, adding molecular information on tumor receptor status to morphology-based tumor response criteria.

CAR T cells targeting αvβ3 integrin are effective against advanced cancer in preclinical models

Objective

Integrins are heterodimeric receptors that convey cell-to-cell and cell-to-matrix interactions. Integrin α_vβ₃ is expressed in several tumour entities including melanoma, glioblastoma, breast, pancreatic and prostate cancer, where it promotes tumour cell survival and metastasis. Here, we generated α_vβ₃-specific chimeric antigen receptor (CAR) T-cells and analysed their antitumour function in pre-clinical models in vitro and in vivo.

Methods

α_vβ₃-CARs comprising a super-humanised hLM609 targeting domain with either high or low affinity (hLM609v7, K _d = 3 nM vs. hLM609v11, K _d = 160 nM) and equipped with either a long or a short IgG4-Fc extracellular spacer (229 vs. 12 amino acids) were expressed in CD8⁺ and CD4⁺ T-cells through lentiviral transduction.

Results

α_vβ₃-CAR T-cells eliminated α_vβ₃-positive tumour cells rapidly and specifically, produced IFN-γ and IL-2 (CD4⁺ > CD8⁺) and exhibited productive proliferation. In vitro, we observed the strongest reactivity with the higher-affinity hLM609v7 α_vβ₃-CAR in the short spacer configuration, consistent with the tumour membrane-distal localization of the hLM609 epitope. In a murine xenograft model of metastatic A-375 melanoma, the strongest antitumour effect was mediated by the lower-affinity hLM609v11 α_vβ₃-CAR. Notably, a single administration of hLM609v11 α_vβ₃-CAR T-cells was able to induce complete elimination of melanoma lesions, leading to long-term tumour-free survival.

Conclusions

These data establish α_vβ₃ integrin as a novel target for CAR T-cell immunotherapy, and affirm our previous notion that binding domain affinity and spacer length can be calibrated to augment CAR reactivity.

Clinical implications

α_vβ₃-CAR T-cells have therapeutic potential in several prevalent solid tumours, including melanoma and triple-negative breast cancer.

Integrins as therapeutic targets in the organ-specific metastasis of human malignant melanoma

Integrins are a large family of adhesion molecules that mediate cell-cell and cell-extracellular matrix interactions. Among the 24 integrin isoforms, many have been found to be associated with tumor angiogenesis, tumor cell migration and proliferation, and metastasis. Integrins, especially αvβ3, αvβ5 and α5β1, participate in mediating tumor angiogenesis by interacting with the vascular endothelial growth factor and angiopoietin-Tie signaling pathways. Melanoma patients have a poor prognosis when the primary tumor has generated distant metastases, and the melanoma metastatic site is an independent predictor of the survival of these patients. Different integrins on the melanoma cell surface preferentially direct circulating melanoma cells to different organs and promote the development of metastases at specific organ sites. For instance, melanoma cells expressing integrin β3 tend to metastasize to the lungs, whereas those expressing integrin β1 preferentially generate lymph node metastases. Moreover, tumor cell-derived exosomes which contain different integrins may prepare a pre-metastatic niche in specific organs and promote organ-specific metastases. Because of the important role that integrins play in tumor angiogenesis and metastasis, they have become promising targets for the treatment of advanced cancer. In this paper, we review the integrin isoforms responsible for angiogenesis and organ-specific metastasis in malignant melanoma and the inhibitors that have been considered for the future treatment of metastatic disease.

Precise integrin-targeting near-infrared imaging-guided surgical method increases surgical qualification of peritoneal carcinomatosis from gastric cancer in mice

Peritoneal carcinomatosis from gastric cancer represents a common recurrent gastric cancer that seriously affects the survival, prognosis, and quality of life of patients at its advanced stage. In recent years, complete cytoreduction surgery in combination with hyperthermic intraperitoneal chemotherapy has been demonstrated to improve the survival and prognosis of patients with malignant tumors including peritoneal carcinomatosis from gastric cancer. Establishing viable methods of accurately assessing the tumor burden in patients with peritoneal carcinoma and correctly selecting suitable patients in order to improve cytoreduction surgical outcomes and reduce the risk of postoperative complications has become a challenge in the field of peritoneal carcinoma research. Here, we investigated peritoneal carcinomatosis from gastric cancer in a mouse model by using our self-developed surgical navigation system that combines optical molecular imaging with an integrin-targeting Arg-Gly-Asp-indocyanine green (RGD-ICG) molecular probe. The results showed that our diagnostic method could achieve a sensitivity and specificity of up to 93.93% and 100%, respectively, with a diagnostic index (DI) of 193.93% and diagnostic accuracy rate of 93.93%.Furthermore, the minimum tumor diameter measured during the surgery was 1.8 mm and the operative time was shortened by 3.26-fold when compared with the conventionally-treated control group. Therefore, our surgical navigation system that combines optical molecular imaging with an RGD-ICG molecular probe, could improve the diagnostic accuracy rate for peritoneal carcinomatosis from gastric cancer, shorten the operative time, and improve the quality of the cytoreduction surgery for peritoneal carcinomatosis from gastric cancer, thus providing a solid foundation for its future clinical development and application.

PIM kinases as therapeutic targets against advanced melanoma

Therapeutic strategies for the treatment of metastatic melanoma show encouraging results in the clinic; however, not all patients respond equally and tumor resistance still poses a challenge. To identify novel therapeutic targets for melanoma, we screened a panel of structurally diverse organometallic inhibitors against human-derived normal and melanoma cells. We observed that a compound that targets PIM kinases (a family of Ser/Thr kinases) preferentially inhibited melanoma cell proliferation, invasion, and viability in adherent and three-dimensional (3D) melanoma models. Assessment of tumor tissue from melanoma patients showed that PIM kinases are expressed in pre- and post-treatment tumors, suggesting PIM kinases as promising targets in the clinic. Using knockdown studies, we showed that PIM1 contributes to melanoma cell proliferation and tumor growth in vivo; however, the presence of PIM2 and PIM3 could also influence the outcome. The inhibition of all PIM isoforms using SGI-1776 (a clinically-available PIM inhibitor) reduced melanoma proliferation and survival in preclinical models of melanoma. This was potentiated in the presence of the BRAF inhibitor PLX4720 and in the presence of PI3K inhibitors. Our findings suggest that PIM inhibitors provide promising additions to the targeted therapies available to melanoma patients.

Quantitative comparison of the spreading and invasion of radial growth phase and metastatic melanoma cells in a three-dimensional human skin equivalent model

BACKGROUND

Standard two-dimensional (2D) cell migration assays do not provide information about vertical invasion processes, which are critical for melanoma progression. We provide information about three-dimensional (3D) melanoma cell migration, proliferation and invasion in a 3D melanoma skin equivalent (MSE) model. In particular, we pay careful attention to compare the structure of the tissues in the MSE with similarly-prepared 3D human skin equivalent (HSE) models. The HSE model is identically prepared to the MSE model except that melanoma cells are omitted. Using the MSE model, we examine melanoma migration, proliferation and invasion from two different human melanoma cell lines. One cell line, WM35, is associated with the early phase of the disease where spreading is thought to be confined to the epidermis. The other cell line, SK-MEL-28, is associated with the later phase of the disease where spreading into the dermis is expected.

METHODS

3D MSE and HSE models are constructed using human de-epidermised dermis (DED) prepared from skin tissue. Primary fibroblasts and primary keratinocytes are used in the MSE and HSE models to ensure the formation of a stratified epidermis, with a well-defined basement membrane. Radial spreading of cells across the surface of the HSE and MSE models is observed. Vertical invasion of melanoma cells downward through the skin is observed and measured using immunohistochemistry. All measurements of invasion are made at day 0, 9, 15 and 20, providing detailed time course data.

RESULTS

Both HSE and MSE models are similar to native skin in vivo, with a well-defined stratification of the epidermis that is separated from the dermis by a basement membrane. In the HSE and MSE we find fibroblast cells confined to the dermis, and differentiated keratinocytes in the epidermis. In the MSE, melanoma cells form colonies in the epidermis during the early part of the experiment. In the later stage of the experiment, the melanoma cells in the MSE invade deeper into the tissues. Interestingly, both the WM35 and SK-MEL-28 melanoma cells lead to a breakdown of the basement membrane and eventually enter the dermis. However, these two cell lines invade at different rates, with the SK-MEL-28 melanoma cells invading faster than the WM35 cells.

DISCUSSION

The MSE and HSE models are a reliable platform for studying melanoma invasion in a 3D tissue that is similar to native human skin. Interestingly, we find that the WM35 cell line, that is thought to be associated with radial spreading only, is able to invade into the dermis. The vertical invasion of melanoma cells into the dermal region appears to be associated with a localised disruption of the basement membrane. Presenting our results in terms of time course data, along with images and quantitative measurements of the depth of invasion extends previous 3D work that has often been reported without these details.

Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model

Melanoma is a highly metastatic and deadly form of cancer. Invasive melanoma cells overexpress integrin α_vβ₃, which is a well-known target for Arg-Gly-Asp-based (RGD) peptides. We developed a sophisticated method to synthetize milligram amounts of a targeted vector that allows the RGD-mediated targeting, internalization, and release of a mitochondria-disruptive peptide derived from the pro-apoptotic Bax protein. We found that 2.5 μM Bax[109-127] was sufficient to destabilize the mitochondria in ten different tumor cell lines, even in the presence of the anti-apoptotic Bcl2 protein, which is often involved in tumor resistance. This pore-forming peptide displayed antitumor activity when it was covalently linked by a disulfide bridge to the tetrameric RAFT-c[RGD]₄-platform and after intravenous injection in a human melanoma tumor model established in humanized immuno-competent mice. In addition to its direct toxic effect, treatment with this combination induced the release of the immuno-stimulating factor monocyte chimoattractant protein 1 (MCP1) in the blood and a decrease in the level of the pro-angiogenic factor FGF2. Our novel multifunctional, apoptosis-inducing agent could be further customized and assayed for potential use in tumor-targeted therapy.

Tension in Cancer

Integrins represent a large family of cell receptors that mediate adhesion to the extracellular matrix (ECM), thereby modulating a variety of cellular functions that are required for proliferation, migration, malignant conversion and invasiveness. During tumorigenesis the conversion of a tumor cell from sessile, stationary phenotype to an invasive phenotype requires the ability of tumor cells to interact with their environment in order to transduce signals from the ECM into the cells. Hence, there is increasing evidence that changes in the composition, topography and tension of tumor matrix can be sensed by integrin receptors, leading to the regulation of intracellular signalling events which subsequently help to fuel cancer progression. The fact that intracellular signals perceived from integrin ligand binding impact on almost all steps of tumor progression, including tumor cell proliferation, survival, metastatic dissemination and colonization of a metastatic niche, renders integrins as ideal candidates for the development of therapeutic agents. In this review we summarize the role of integrins in cancer with the special focus on cancer therapies and the recent progress that has been made in the understanding of “integrin-induced tension in cancer”. Finally, we conclude with clinical evidence for the role of integrin-mediated mechanotransduction in the development of therapy-resistant tumors.

Thrombospondin-1 and Cutaneous Melanoma

Background:

Thrombospondins (TSPs) are recognized as important glycoproteins that regulate a wide variety of cell functions and interactions. TSPs in malignant tumors can both enhance and inhibit tumor progression, invasion, and metastasis, depending on cell type, stromal interactions, and microenvironment. These proteins are potential targets for anticancer therapy.

Objective:

The aim of our article is to review the role of thrombospondin-1 (TSP1) in cutaneous melanoma.

Conclusions:

TSP1 expression is variable in melanoma cell lines and tumors. Similar to findings in other human cancers, expression of TSP1 by melanoma cells usually inhibits tumor progression via the antiangiogenic effect of TSP1. Conversely, stromal TSP1 overexpression in melanoma is a poor prognostic factor associated with decreased survival. Understanding the interactions of TSP1 with other melanoma- and matrix-associated proteins should provide new prognostic indices and possible therapeutic targets for melanoma treatment.

On the trail of the glycan codes stored in cancer-related cell adhesion proteins

Changes in the profile of protein glycosylation are a hallmark of ongoing neoplastic transformation. A unique set of tumor-associated carbohydrate antigens expressed on the surface of malignant cells may serve as powerful diagnostic and therapeutic targets. Cell-surface proteins with altered glycosylation affect the growth, proliferation and survival of those cells, and contribute to their acquisition of the ability to migrate and invade. They may also facilitate tumor-induced immunosuppression and the formation of distant metastases. Deciphering the information encoded in these particular glycan portions of glycoconjugates may shed light on the mechanisms of cancer progression and metastasis. A majority of the related review papers have focused on overall changes in the patterns of cell-surface glycans in various cancers, without pinpointing the molecular carriers of these glycan structures. The present review highlights the ways in which particular tumor-associated glycan(s) coupled with a given membrane-bound protein influence neoplastic cell behavior during the development and progression of cancer. We focus on altered glycosylated cell-adhesion molecules belonging to the cadherin, integrin and immunoglobulin-like superfamilies, examined in the context of molecular interactions.

Gene expression analyses of primary melanomas reveal CTHRC1 as an important player in melanoma progression

Melanoma is notorious for its high tendency to metastasize and its refractoriness to conventional treatments after metastasis, and the responses to most targeted therapies are short-lived. A better understanding of the molecular mechanisms behind melanoma development and progression is needed to develop more effective therapies and to identify new markers to predict disease behavior. Here, we compared the gene expression profiles of benign nevi, and non-metastatic and metastatic primary melanomas to identify any common changes in disease progression. We identified several genes associated with inflammation, angiogenesis, and extracellular matrix modification to be upregulated in metastatic melanomas. We selected one of these genes, collagen triple helix repeat containing 1 (CTHRC1), for detailed analysis, and found that CTHRC1 was expressed in both melanoma cells and the associated fibroblasts, as well as in the endothelium of tumor blood vessels. Knockdown of CTHRC1 expression by shRNAs in melanoma cells inhibited their migration in Transwell assays and their invasion in three-dimensional collagen and Matrigel matrices. We also elucidated the possible down-stream effectors of CTHRC1 by gene expression profiling of the CTHRC1-knockdown cells. Our analyses showed that CTHRC1 is regulated coordinately with fibronectin and integrin β3 by the pro-invasive and -angiogenic transcription factor NFATC2. We also found CTHRC1 to be a target of TFGβ and BRAF. These data highlight the importance of tumor stroma in melanoma progression. Furthermore, CTHRC1 was recognized as an important mediator of melanoma cell migration and invasion, providing together with its regulators-NFATC2, TGFβ, and BRAF-attractive therapeutic targets against metastatic melanomas.

Tumor Cell Adhesion As a Risk Factor for Sentinel Lymph Node Metastasis in Primary Cutaneous Melanoma

PURPOSE

Less than 20% of patients with melanoma who undergo sentinel lymph node (SLN) biopsy based on American Society of Clinical Oncology/Society of Surgical Oncology recommendations are SLN positive. We present a multi-institutional study to discover new molecular risk factors associated with SLN positivity in thin and intermediate-thickness melanoma.

PATIENTS AND METHODS

Gene clusters with functional roles in melanoma metastasis were discovered by next-generation sequencing and validated by quantitative polymerase chain reaction using a discovery set of 73 benign nevi, 76 primary cutaneous melanoma, and 11 in-transit melanoma metastases. We then used polymerase chain reaction to quantify gene expression in a model development cohort of 360 consecutive thin and intermediate-thickness melanomas and a validation cohort of 146 melanomas. Outcome of interest was SLN biopsy metastasis within 90 days of melanoma diagnosis. Logic and logistic regression analyses were used to develop a model for the likelihood of SLN metastasis from molecular, clinical, and histologic variables.

RESULTS

ITGB3, LAMB1, PLAT, and TP53 expression were associated with SLN metastasis. The predictive ability of a model that included these molecular variables in combination with clinicopathologic variables (patient age, Breslow depth, and tumor ulceration) was significantly greater than a model that only considered clinicopathologic variables and also performed well in the validation cohort (area under the curve, 0.93; 95% CI, 0.87 to 0.97; false-positive and false-negative rates of 22% and 0%, respectively, using a 10% cutoff for predicted SLN metastasis risk).

CONCLUSION

The addition of cell adhesion-linked gene expression variables to clinicopathologic variables improves the identification of patients with SLN metastases within 90 days of melanoma diagnosis.

Orally active αvβ3 integrin inhibitor MK-0429 reduces melanoma metastasis

Melanoma remains one of the most aggressive types of cancer with a historically low survival rate. The αvβ3 integrin is involved in the progression of malignant melanoma. In the present study, the efficacy of MK-0429, a selective inhibitor of the αvβ3 integrin, was evaluated for its potential in the prevention of melanoma metastasis. Female B6D2F1 mice injected via the tail vein with murine B16F10 melanoma developed lung metastases within ~10 days. In the first experiment, the prevention of lung metastasis was assessed in the model treated with either vehicle, MK-0429 at 100 and 300 mg/kg orally twice daily or cyclophosphamide at 300 mg/kg, i.p. once daily. Study endpoints included determination of the study time period to achieve metastasis in lungs in this model, evaluation of the health effects on the study animals, the total number of lung colonies identified and lung tumor area. Unlike cyclophosphamide, the MK-0429 treatment did not lead to a significant weight reduction in mice. MK-0429 at 100 and 300 mg/kg reduced the number of metastatic tumor colonies by 64 and 57%, respectively, and the high dose also reduced the tumor area by 60% as compared to the vehicle. The second experiment employed B16F10 luciferase-expressing cells to examine the de novo progression of melanoma metastasis over 15 days with bioluminescent imaging of mice treated with MK-0429 at 300 mg/kg as compared to the vehicle. Tumor burden progressively advanced in the lungs of the B16F10-treated animals. However, MK-0429 reduced the progression of ventral and dorsal lung metastases by 22 and 38%, respectively, as compared to the vehicle, by study completion. Quantification of ex vivo tumor burden showed a 30-40% reduction in lung colonies by MK-0429. The two studies collectively demonstrated that MK-0429 was safe and efficacious in significantly decreasing melanoma metastasis in the lungs. The results emphasized the potential of MK-0429 as a novel, therapeutic agent for the prevention of metastatic melanoma.

Cancer stratification by molecular imaging

The lack of specificity of traditional cytotoxic drugs has triggered the development of anticancer agents that selectively address specific molecular targets. An intrinsic property of these specialized drugs is their limited applicability for specific patient subgroups. Consequently, the generation of information about tumor characteristics is the key to exploit the potential of these drugs. Currently, cancer stratification relies on three approaches: Gene expression analysis and cancer proteomics, immunohistochemistry and molecular imaging. In order to enable the precise localization of functionally expressed targets, molecular imaging combines highly selective biomarkers and intense signal sources. Thus, cancer stratification and localization are performed simultaneously. Many cancer types are characterized by altered receptor expression, such as somatostatin receptors, folate receptors or Her2 (human epidermal growth factor receptor 2). Similar correlations are also known for a multitude of transporters, such as glucose transporters, amino acid transporters or hNIS (human sodium iodide symporter), as well as cell specific proteins, such as the prostate specific membrane antigen, integrins, and CD20. This review provides a comprehensive description of the methods, targets and agents used in molecular imaging, to outline their application for cancer stratification. Emphasis is placed on radiotracers which are used to identify altered expression patterns of cancer associated markers.

Disintegrins from snake venoms and their applications in cancer research and therapy

Integrins regulate diverse functions in cancer pathology and in tumor cell development and contribute to important processes such as cell shape, survival, proliferation, transcription, angiogenesis, migration, and invasion. A number of snake venom proteins have the ability to interact with integrins. Among these are the disintegrins, a family of small, non-enzymatic, and cysteine-rich proteins found in the venom of numerous snake families. The venom proteins may have a potential role in terms of novel therapeutic leads for cancer treatment. Disintegrin can target specific integrins and as such it is conceivable that they could interfere in important processes involved in carcinogenesis, tumor growth, invasion and migration. Herein we present a survey of studies involving the use of snake venom disintegrins for cancer detection and treatment. The aim of this review is to highlight the relationship of integrins with cancer and to present examples as to how certain disintegrins can detect and affect biological processes related to cancer. This in turn will illustrate the great potential of these molecules for cancer research. Furthermore, we also outline several new approaches being created to address problems commonly associated with the clinical application of peptide-based drugs such as instability, immunogenicity, and availability.

Three-dimensional modeling of ovarian cancer

New models for epithelial ovarian cancer initiation and metastasis are required to obtain a mechanistic understanding of the disease and to develop new therapeutics. Modeling ovarian cancer however is challenging as a result of the genetic heterogeneity of the malignancy, the diverse pathology, the limited availability of human tissue for research, the atypical mechanisms of metastasis, and because the origin is unclear. Insights into the origin of high-grade serous ovarian carcinomas and mechanisms of metastasis have resulted in the generation of novel three-dimensional (3D) culture models that better approximate the behavior of the tumor cells in vivo than prior two-dimensional models. The 3D models aim to recapitulate the tumor microenvironment, which has a critical role in the pathogenesis of ovarian cancer. Ultimately, findings using models that accurately reflect human ovarian cancer biology are likely to translate into improved clinical outcomes. In this review we discuss the design of new 3D culture models of ovarian cancer primarily using human cells, key studies in which these models have been applied, current limitations, and future applications.

Critical analysis of 3-D organoid in vitro cell culture models for high-throughput drug candidate toxicity assessments

Drug failure due to toxicity indicators remains among the primary reasons for staggering drug attrition rates during clinical studies and post-marketing surveillance. Broader validation and use of next-generation 3-D improved cell culture models are expected to improve predictive power and effectiveness of drug toxicological predictions. However, after decades of promising research significant gaps remain in our collective ability to extract quality human toxicity information from in vitro data using 3-D cell and tissue models. Issues, challenges and future directions for the field to improve drug assay predictive power and reliability of 3-D models are reviewed.

Osteopontin promotes the invasive growth of melanoma cells by activating integrin αvβ3 and down-regulating tetraspanin CD9

Overexpression of osteopontin (OPN) is strongly associated with the invasiveness/metastasis of many cancers, including melanomas. However, the molecular mechanisms of OPN in these processes remain poorly understood. We found that forced expression of OPN in early vertical-growth-phase melanoma cells dramatically increased their migration/invasion and growth/survival in a three-dimensional collagen I gel. Neutralizing antibodies to OPN, integrin β1, and integrin αvβ3, but not to CD44, negated the effects of OPN. Conversely, knocking down OPN in metastatic melanoma cells abrogated the invasive growth. OPN overexpression activated and OPN knockdown inactivated αvβ3 and αvβ5 integrins, negligibly affecting their expression. We further found OPN expression to inversely correlate with tetraspanin CD9 expression. Early-stage melanoma cells displayed low OPN and high CD9 expression, and conversely, metastatic cells displayed high OPN and low CD9 expression. Overexpression of OPN in vertical-growth-phase melanoma cells induced down-regulation of CD9, and knockdown of OPN in metastatic melanoma cells up-regulated CD9. Reversion of these CD9 changes abolished the effects of OPN. Furthermore, knockdown of CD9 in early-stage melanoma cells stimulated their invasive capacity in three-dimensional collagen. Similarly, microarray analyses of benign nevi and primary melanomas from different stages revealed an inverse correlation between OPN and CD9. These data suggest that OPN promotes melanoma cell invasion by activating integrin αvβ3 and down-regulating CD9, a putative metastasis suppressor.

Integrin Signaling as a Cancer Drug Target

Integrins are transmembrane receptors that mediate cell adhesion to neighboring cells and to the extracellular matrix. Here, the various modes in which integrin-mediated adhesion regulates intracellular signaling pathways impinging on cell survival, proliferation, and differentiation are considered. Subsequently, evidence that integrins also control crucial signaling cascades in cancer cells is discussed. Lastly, the important role of integrin signaling in tumor cells as well as in stromal cells that support cancer growth, metastasis, and therapy resistance indicates that integrin signaling may be an attractive target for (combined) cancer therapy strategies. Current approaches to target integrins in this context are reviewed.

In vitro three-dimensional tumor microenvironment models for anticancer drug discovery

Anticancer drug discovery has long been hampered by the poor predictivity of the preclinical models. There is a growing realization that the tumor microenvironment is a critical determinant of the response of cancer cells to therapeutic agents. The past 5 years have seen a great deal of progress in our understanding of how the three-dimensional microenvironment modulates the signaling behavior of tumor cells. The present review discusses how three-dimensional in vitro cell culture models can benefit cancer drug discovery through an accurate modeling of the tumor microenvironment, leading to more physiologically relevant experimental outcomes.

Development of a novel class of B-Raf(V600E)-selective inhibitors through virtual screening and hierarchical hit optimization

Oncogenic mutations in critical nodes of cellular signaling pathways have been associated with tumorigenesis and progression. The B-Raf protein kinase, a key hub in the canonical MAPK signaling cascade, is mutated in a broad range of human cancers and especially in malignant melanoma. The most prevalent B-Raf(V600E) mutant exhibits elevated kinase activity and results in constitutive activation of the MAPK pathway, thus making it a promising drug target for cancer therapy. Herein, we describe the development of novel B-Raf(V600E) selective inhibitors via multi-step virtual screening and hierarchical hit optimization. Nine hit compounds with low micromolar IC(50) values were identified as B-Raf(V600E) inhibitors through virtual screening. Subsequent scaffold-based analogue searching and medicinal chemistry efforts significantly improved both the inhibitor potency and oncogene selectivity. In particular, compounds 22f and 22q possess nanomolar IC(50) values with selectivity for B-Raf(V600E)in vitro and exclusive cytotoxicity against B-Raf(V600E) harboring cancer cells.

Role of the autotaxin-lysophosphatidate axis in cancer resistance to chemotherapy and radiotherapy

High expression of autotaxin in cancers is often associated with increased tumor progression, angiogenesis and metastasis. This is explained mainly since autotaxin produces the lipid growth factor, lysophosphatidate (LPA), which stimulates cell division, survival and migration. It has recently become evident that these signaling effects of LPA also produce resistance to chemotherapy and radiation-induced cell death. This results especially from the stimulation of LPA(2) receptors, which depletes the cell of Siva-1, a pro-apoptotic signaling protein and stimulates prosurvival kinase pathways through a mechanism mediated via TRIP-6. LPA signaling also increases the formation of sphingosine 1-phosphate, a pro-survival lipid. At the same time, LPA decreases the accumulation of ceramides, which are used in radiation therapy and by many chemotherapeutic agents to stimulate apoptosis. The signaling actions of extracellular LPA are terminated by its dephosphorylation by a family of lipid phosphate phosphatases (LPP) that act as ecto-enzymes. In addition, lipid phosphate phoshatase-1 attenuates signaling downstream of the activation of both LPA receptors and receptor tyrosine kinases. This makes many cancer cells hypersensitive to the action of various growth factors since they often express low LPP1/3 activity. Increasing our understanding of the complicated signaling pathways that are used by LPA to stimulate cell survival should identify new therapeutic targets that can be exploited to increase the efficacy of chemo- and radio-therapy. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.

Emerging molecular targets in melanoma invasion and metastasis

Metastatic cutaneous melanoma accounts for the majority of skin cancer deaths due to its aggressiveness and high resistance to current therapies. To efficiently metastasize, invasive melanoma cells need to change their cytoskeletal organization and alter contacts with the extracellular matrix and the surrounding stromal cells. Melanoma cells can use different migratory strategies depending on varying environments to exit the primary tumour mass and invade surrounding and later distant tissues. In this review, we have focused on tumour cell plasticity or the interconvertibility that melanoma cells have as one of the factors that contribute to melanoma metastasis. This has been an area of very intense research in the last 5 yr yielding a vast number of findings. We have therefore reviewed all the possible clinical opportunities that this new knowledge offers to both stratify and treat cutaneous malignant melanoma patients.

Occupy tissue: the movement in cancer metastasis

The critical role of migration and invasion in cancer metastasis warrants new therapeutic approaches targeting the machinery regulating cell migration and invasion. While 2-dimensional (2D) models have helped identify a range of adhesion molecules, cytoskeletal components and regulators that are potentially important for cell migration, the use of models that better mimic the 3-dimensional (3D) environment has yielded new insights into the physiology of cell movement. For example, studying cells in 3D models has revealed that invading cancer cells may switch between heterogeneous invasion modes and thus evade pharmacological inhibition of invasion. Here we summarize published data in which the role of cell adhesion molecules in 2D vs. 3D migration have been directly compared and discuss mechanisms that regulate migration speed and persistence in 2D and 3D. Finally we discuss limits of 3D culture models to recapitulate the in vivo situation.

Protein kinase Cα (PKCα) regulates p53 localization and melanoma cell survival downstream of integrin αv in three-dimensional collagen and in vivo

Protein kinase C α (PKCα) is overexpressed in numerous types of cancer. Importantly, PKCα has been linked to metastasis of malignant melanoma in patients. However, it has been unclear how PKCα may be regulated and how it exerts its role in melanoma. Here, we identified a role for PKCα in melanoma cell survival in a three-dimensional collagen model mimicking the in vivo pathophysiology of the dermis. A pathway was identified that involved integrin αv-mediated up-regulation of PKCα and PKCα-dependent regulation of p53 localization, which was connected to melanoma cell survival. Melanoma survival and growth in three-dimensional microenvironments requires the expression of integrin αv, which acts to suppress p53 activity. Interestingly, microarray analysis revealed that PKCα was up-regulated by integrin αv in a three-dimensional microenvironment-dependent manner. Integrin αv was observed to promote a relocalization of endogenous p53 from the nucleus to the cytoplasm upon growth in three-dimensional collagen as well as in vivo, whereas stable knockdown of PKCα inhibited the integrin αv-mediated relocalization of p53. Importantly, knockdown of PKCα also promoted apoptosis in three-dimensional collagen and in vivo, resulting in reduced tumor growth. This indicates that PKCα constitutes a crucial component of the integrin αv-mediated pathway(s) that promote p53 relocalization and melanoma survival.

Inhibition of fibroblast growth by Notch1 signaling is mediated by induction of Wnt11-dependent WISP-1

Fibroblasts are an integral component of stroma and important source of growth factors and extracellular matrix (ECM). They play a prominent role in maintaining tissue homeostasis and in wound healing and tumor growth. Notch signaling regulates biological function in a variety of cells. To elucidate the physiological function of Notch signaling in fibroblasts, we ablated Notch1 in mouse (Notch1^Flox/Flox) embryonic fibroblasts (MEFs). Notch1-deficient (Notch1^−/−) MEFs displayed faster growth and motility rate compared to Notch1^Flox/Flox MEFs. Such phenotypic changes, however, were reversible by reconstitution of Notch1 activation via overexpression of the intracellular domain of Notch1 (NICD1) in Notch1-deficient MEFs. In contrast, constitutive activation of Notch1 signaling by introducing NICD1 into primary human dermal fibroblasts (FF2441), which caused pan-Notch activation, inhibited cell growth and motility, whereas cellular inhibition was relievable when the Notch activation was countered with dominant-negative mutant of Master-mind like 1 (DN-MAML-1). Functionally, “Notch-activated” stromal fibroblasts could inhibit tumor cell growth/invasion. Moreover, Notch activation induced expression of Wnt-induced secreted proteins-1 (WISP-1/CCN4) in FF2441 cells while deletion of Notch1 in MEFs resulted in an opposite effect. Notably, WISP-1 suppressed fibroblast proliferation, and was responsible for mediating Notch1's inhibitory effect since siRNA-mediated blockade of WISP-1 expression could relieve cell growth inhibition. Notch1-induced WISP-1 expression appeared to be Wnt11-dependent, but Wnt1-independent. Blockade of Wnt11 expression resulted in decreased WISP-1 expression and liberated Notch-induced cell growth inhibition. These findings indicated that inhibition of fibroblast proliferation by Notch pathway activation is mediated, at least in part, through regulating Wnt1-independent, but Wnt11-dependent WISP-1 expression.

Identification of a novel family of BRAF(V600E) inhibitors

The BRAF oncoprotein is mutated in about half of malignant melanomas and other cancers, and a kinase activating single valine to glutamate substitution at residue 600 (BRAF(V600E)) accounts for over 90% of BRAF-mediated cancers. Several BRAF(V600E) inhibitors have been developed, although they harbor some liabilities, thus motivating the development of other BRAF(V600E) inhibitor options. We report here the use of an ELISA based high-throughput screen to identify a family of related quinolol/naphthol compounds that preferentially inhibit BRAF(V600E) over BRAF(WT) and other kinases. We also report the X-ray crystal structure of a BRAF/quinolol complex revealing the mode of inhibition, employ structure-based medicinal chemistry efforts to prepare naphthol analogues that inhibit BRAF(V600E) in vitro with IC(50) values in the 80-200 nM range under saturating ATP concentrations, and demonstrate that these compounds inhibit MAPK signaling in melanoma cells. Prospects for improving the potency and selectivity of these inhibitors are discussed.