The role of alpha(v)beta(3) in prostate cancer progression

Advancing Cancer Theranostics Through Integrin αVβ3-Targeted Peptidomimetic IAC: From Bench to Bedside

Introduction: The expression of alpha-five beta-three (αVβ3) integrins is upregulated in various malignancies undergoing angiogenesis. The development of integrin antagonists as diagnostic probes makes the αVβ3 integrin a suitable candidate for targeting tumor angiogenesis. The goal of this study was to optimize the radiolabeling and evaluate the potential of conjugated integrin antagonist carbamate (IAC), a peptidomimetic, as a theranostic radiopharmaceutical for targeting tumor angiogenesis. Methodology: Radiolabeling of DOTAGA [2,2',2" -{10-(2,6-dioxotetrahydro-2H-pyran-3-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl} triacetic-acid]-IAC with [68Ga]Ga, [177Lu]Lu, and [225Ac]Ac was optimized. The binding affinity (Kd) of DOTAGA-IAC for the αVβ3 receptor and cancer cell lines was quantified. The biodistribution studies were conducted in healthy Wistar rats. Dosimetry analysis was performed on [177Lu]Lu-DOTAGA-IAC distribution data. A pilot study of [68Ga]Ga-DOTAGA-IAC and [18F]FDG Positron Emission Tomography (PET/CT) imaging was performed in five patients with histopathologically confirmed breast cancer. PET/CT findings were compared between [68Ga]Ga-DOTAGA-IAC and [18F]FDG in these patients. Results: Radiopharmaceuticals were prepared with high radiochemical purity (>99.9%). Kd and Bmax measurements were 15.02 nM and 417 fmol for αVβ3 receptor protein: 115.7 nM and 295.3 fmol for C6 glioma cells. Biodistribution studies in rats suggested the excretion via kidneys and partially through the hepatobiliary route. The effective dose of [177Lu]Lu-DOTAGA-IAC was found to be 0.17 mSv/MBq. The dynamic study in patients revealed the optimal imaging time to be 30-35 mins postadministration. Out of the cohort, [68Ga]Ga-DOTAGA-IAC detected the primary lesions in all five patients with a mean standard uptake value (SUVmax) of 3.94 ± 0.58 compared with [18F]FDG (SUVmax 13.8 ± 6.53). Conclusion: The study demonstrates that DOTAGA-IAC exhibits strong binding to αVβ3 integrin, positioning it as a promising PET agent for assessing primary and metastatic cancers. The outcomes from the pilot study suggest the potential of [68Ga]Ga-DOTAGA-IAC PET/CT in breast carcinoma diagnosis. While recognizing the theranostic potential of DOTAGA-IAC for αVβ3 integrin-expressing tumors, further clinical investigations are warranted to comprehensively assess therapeutic efficacy.

Osteoarthritis as a Systemic Disease Promoted Prostate Cancer In Vivo and In Vitro

Osteoarthritis (OA) is increasing worldwide, and previous work found that OA increases systemic cartilage oligomeric matrix protein (COMP), which has also been implicated in prostate cancer (PCa). As such, we sought to investigate whether OA augments PCa progression. Cellular proliferation and migration of RM1 murine PCa cells treated with interleukin (IL)-1α, COMP, IL-1α + COMP, or conditioned media from cartilage explants treated with IL-1α (representing OA media) and with inhibitors of COMP were assessed. A validated murine model was used for tumor growth and marker expression analysis. Both proliferation and migration were greater in PCa cells treated with OA media compared to controls (p < 0.001), which was not seen with direct application of the stimulants. Migration and proliferation were not negatively affected when OA media was mixed with downstream and COMP inhibitors compared to controls (p > 0.05 for all). Mice with OA developed tumors 100% of the time, whereas mice without OA only 83.4% (p = 0.478). Tumor weight correlated with OA severity (Pearson correlation = 0.813, p = 0.002). Moreover, tumors from mice with OA demonstrated increased Ki-67 expression compared to controls (mean 24.56% vs. 6.91%, p = 0.004) but no difference in CD31, PSMA, or COMP expression (p > 0.05). OA appears to promote prostate cancer in vitro and in vivo.

Interleukin-30 subverts prostate cancer-endothelium crosstalk by fostering angiogenesis and activating immunoregulatory and oncogenic signaling pathways

BACKGROUND

Cancer-endothelial interplay is crucial for tumor behavior, yet the molecular mechanisms involved are largely unknown. Interleukin(IL)-30, which is expressed as a membrane-anchored cytokine by human prostate cancer (PC) cells, promotes PC vascularization and progression, but the underlying mechanisms have yet to be fully explored.

METHODS

PC-endothelial cell (EC) interactions were investigated, after coculture, by flow cytometry, transcriptional profiling, western blot, and ELISA assays. Proteome profiler phospho-kinase array unveiled the molecular pathways involved. The role of tumor-derived IL30 on the endothelium's capacity to generate autocrine circuits and vascular budding was determined following IL30 overexpression, by gene transfection, or its deletion by CRISPR/Cas9 genome editing. Clinical value of the experimental findings was determined through immunopathological study of experimental and patient-derived PC samples, and bioinformatics of gene expression profiles from PC patients.

RESULTS

Contact with PC cells favors EC proliferation and production of angiogenic and angiocrine factors, which are boosted by PC expression of IL30, that feeds autocrine loops, mediated by IGF1, EDN1, ANG and CXCL10, and promotes vascular budding and inflammation, via phosphorylation of multiple signaling proteins, such as Src, Yes, STAT3, STAT6, RSK1/2, c-Jun, AKT and, primarily CREB, GSK-3α/β, HSP60 and p53. Deletion of the IL30 gene in PC cells inhibits endothelial expression of IGF1, EDN1, ANG and CXCL10 and substantially impairs tumor angiogenesis. In its interaction with IL30-overexpressing PC cells the endothelium boosts their expression of a wide range of immunity regulatory genes, including CCL28, CCL4, CCL5, CCR2, CCR7, CXCR4, IL10, IL13, IL17A, FASLG, IDO1, KITLG, TNFA, TNFSF10 and PDCD1, and cancer driver genes, including BCL2, CCND2, EGR3, IL6, VEGFA, KLK3, PTGS1, LGALS4, GNRH1 and SHBG. Immunopathological analyses of PC xenografts and in silico investigation of 1116 PC cases, from the Prostate Cancer Transcriptome Atlas, confirmed the correlation between the expression of IL30 and that of both pro-inflammatory genes, NOS2, TNFA, CXCR5 and IL12B, and cancer driver genes, LGALS4, GNRH1 and SHBG, which was validated in a cohort of 80 PC patients.

CONCLUSIONS

IL30 regulates the crosstalk between PC and EC and reshapes their transcriptional profiles, triggering angiogenic, immunoregulatory and oncogenic gene expression programs. These findings highlight the angiostatic and oncostatic efficacy of targeting IL30 to fight PC.

Circulating Tumor Cells Adhesion: Application in Biosensors

The early and non-invasive diagnosis of tumor diseases has been widely investigated by the scientific community focusing on the development of sensors/biomarkers that act as a way of recognizing the adhesion of circulating tumor cells (CTCs). As a challenge in this area, strategies for CTCs capture and enrichment currently require improvements in the sensors/biomarker's selectivity. This can be achieved by understanding the biological recognition factors for different cancer cell lines and also by understanding the interaction between surface parameters and the affinity between macromolecules and the cell surface. To overcome some of these concerns, electrochemical sensors have been used as precise, fast-response, and low-cost transduction platforms for application in cytosensors. Additionally, distinct materials, geometries, and technologies have been investigated to improve the sensitivity and specificity properties of the support electrode that will transform biochemical events into electrical signals. This review identifies novel approaches regarding the application of different specific biomarkers (CD44, Integrins, and EpCAm) for capturing CTCs. These biomarkers can be applied in electrochemical biosensors as a cytodetection strategy for diagnosis of cancerous diseases.

Oxidative stress induced by Pollonein-LAAO, a new L-amino acid oxidase from Bothrops moojeni venom, prompts prostate tumor spheroid cell death and impairs the cellular invasion process in vitro

Cancer cells produce abnormal levels of reactive oxygen species (ROS) that contribute to promote their malignant phenotype. In this framework, we hypothesized that the change in ROS concentration above threshold could impair key events of prostate cancer cells (PC-3) progression. Our results demonstrated that Pollonein-LAAO, a new L-amino acid oxidase obtained from Bothrops moojeni venom, was cytotoxic to PC-3 cells in two-dimensional and in tumor spheroid assays. Pollonein-LAAO was able to increase the intracellular ROS generation that culminates in cell death from apoptosis by both intrinsic and extrinsic pathways due to the up-regulation of TP53, BAX, BAD, TNFRSF10B and CASP8. Additionally, Pollonein-LAAO reduced mitochondrial membrane potential and caused G0/G1 phase to delay, due to the up-regulation of CDKN1A and the down-regulation of the expression of CDK2 and E2F. Interestingly, Pollonein-LAAO inhibited critical steps of the cellular invasion process (migration, invasion and adhesion), due to the down-regulation of SNAI1, VIM, MMP2, ITGA2, ITGAV and ITGB3. Furthermore, the Pollonein-LAAO effects were associated with the intracellular ROS production, since the presence of catalase restored the invasiveness of PC-3 cells. In this sense, this study contributes to the potential use of Pollonein-LAAO as ROS-based agent to enhance the current understanding of cancer treatment strategies.

Cyclic Peptides for the Treatment of Cancers: A Review

Cyclic peptides have been widely reported to have therapeutic abilities in the treatment of cancer. This has been proven through in vitro and in vivo studies against breast, lung, liver, colon, and prostate cancers, among others. The multitude of data available in the literature supports the potential of cyclic peptides as anticancer agents. This review summarizes the findings from previously reported studies and discusses the different cyclic peptide compounds, the sources, and their modes of action as anticancer agents. The prospects and future of cyclic peptides will also be described to give an overview on the direction of cyclic peptide development for clinical applications.

Cu2+-Chelating Mesoporous Silica Nanoparticles for Synergistic Chemotherapy/Chemodynamic Therapy

In this study, a pH-responsive controlled-release mesoporous silica nanoparticle (MSN) formulation was developed. The MSNs were functionalized with a histidine (His)-tagged targeting peptide (B3int) through an amide bond, and loaded with an anticancer drug (cisplatin (CP)) and a lysosomal destabilization mediator (chloroquine (CQ)). Cu²⁺ was then used to seal the pores of the MSNs via chelation with the His-tag. The resultant nanoparticles showed pH-responsive drug release, and could effectively target tumor cells via the targeting effect of B3int. The presence of CP and Cu²⁺ permits reactive oxygen species to be generated inside cells; thus, the chemotherapeutic effect of CP is augmented by chemodynamic therapy. In vitro and in vivo experiments showed that the nanoparticles are able to effectively kill tumor cells. An in vivo cancer model revealed that the nanoparticles increase apoptosis in tumor cells, and thereby diminish the tumor volume. No off-target toxicity was noted. It thus appears that the functionalized MSNs developed in this work have great potential for targeted, synergistic anticancer therapies.

SPARC Induces E-Cadherin Repression and Enhances Cell Migration through Integrin αvβ3 and the Transcription Factor ZEB1 in Prostate Cancer Cells

Secreted protein acidic and rich in cysteine (SPARC), or osteonectin, is a matricellular protein that modulates interactions between cells and their microenvironment. SPARC is expressed during extracellular matrix remodeling and is abundant in bone marrow and high-grade prostate cancer (PCa). In PCa, SPARC induces changes associated with epithelial–mesenchymal transition (EMT), enhancing migration and invasion and increasing the expression of EMT transcriptional factor Zinc finger E-box-binding homeobox 1 (ZEB1), but not Zinc finger protein SNAI1 (Snail) or Zinc finger protein SNAI2 (Slug). It is unknown whether the SPARC-induced downregulation of E-cadherin in PCa cells depends on ZEB1. Several integrins are mediators of SPARC effects in cancer cells. Because integrin signaling can induce EMT programs, we hypothesize that SPARC induces E-cadherin repression through the activation of integrins and ZEB1. Through stable knockdown and the overexpression of SPARC in PCa cells, we demonstrate that SPARC downregulates E-cadherin and increases vimentin, ZEB1, and integrin β3 expression. Knocking down SPARC in PCa cells decreases the tyrosine-925 phosphorylation of FAK and impairs focal adhesion formation. Blocking integrin αvβ3 and silencing ZEB1 revert both the SPARC-induced downregulation of E-cadherin and cell migration enhancement. We conclude that SPARC induces E-cadherin repression and enhances PCa cell migration through the integrin αvβ3/ZEB1 signaling pathway.

Non-Cationic RGD-Containing Protein Nanocarrier for Tumor-Targeted siRNA Delivery

Despite the recent successes in siRNA therapeutics, targeted delivery beyond the liver remains the major hurdle for the widespread application of siRNA in vivo. Current cationic liposome or polymer-based delivery agents are restricted to the liver and suffer from off-target effects, poor clearance, low serum stability, and high toxicity. In this study, we genetically engineered a non-cationic non-viral tumor-targeted universal siRNA nanocarrier (MW 26 KDa). This protein nanocarrier consists of three function domains: a dsRNA binding domain (dsRBD) (from human protein kinase R) for any siRNA binding, 18-histidine for endosome escape, and two RGD peptides at the N- and C-termini for targeting tumor and tumor neovasculature. We showed that cloned dual-RGD-dsRBD-18his (dual-RGD) protein protects siRNA against RNases, induces effective siRNA endosomal escape, specifically targets integrin α_vβ₃ expressing cells in vitro, and homes siRNA to tumors in vivo. The delivered siRNA leads to target gene knockdown in the cell lines and tumor xenografts with low toxicity. This multifunctional and biomimetic siRNA carrier is biodegradable, has low toxicity, is suitable for mass production by fermentation, and is serum stable, holding great potential to provide a widely applicable siRNA carrier for tumor-targeted siRNA delivery.

Cancer induced bone pain: current management and future perspectives

Recent improvements in the therapeutic armamentarium of oncology by the addition of targeted and immunotherapeutic agents have led to an increase in the life expectancy of advanced-stage cancer patients. This has led to an increased number of patients presenting with bone metastasis and experiencing episodes of cancer-induced bone pain (CIBP). CIBP is a crippling, chronic, morbid state interfering significantly with the functional capacity and the quality of life (QoL). CIBP is characterized by a complex multifactorial pathophysiological mechanism involving tumor cells, bone cells, inflammatory microenvironment, and the neuronal tissue. It may not be possible to mitigate pain completely; therefore, the aim should be to reach the lowest possible level of pain that allows for an acceptable QoL to the patient. Multimodality approach of surgical, radiation, medical and behavioral techniques is thus recommended to manage CIBP. This review discusses the pathogenesis and pathophysiological mechanism accompanying bone metastasis and CIBP, currently approved therapies for the management of CIBP, and the future perspective.

Anti-Cancer Effects of Cyclic Peptide ALOS4 in a Human Melanoma Mouse Model

We examined the effects of ALOS4, a cyclic peptide discovered previously by phage library selection against integrin α_vβ₃, on a human melanoma (A375) xenograft model to determine its abilities as a potential anti-cancer agent. We found that ALOS4 promoted healthy weight gain in A375-engrafted nude mice and reduced melanoma tumor mass and volume. Despite these positive changes, examination of the tumor tissue did not indicate any significant effects on proliferation, mitotic index, tissue vascularization, or reduction of αSMA or Ki-67 tumor markers. Modulation in overall expression of critical downstream α_vβ₃ integrin factors, such as FAK and Src, as well as reductions in gene expression of c-Fos and c-Jun transcription factors, indirectly confirmed our suspicions that ALOS4 is likely acting through an integrin-mediated pathway. Further, we found no overt formulation issues with ALOS4 regarding interaction with standard inert laboratory materials (polypropylene, borosilicate glass) or with pH and temperature stability under prolonged storage. Collectively, ALOS4 appears to be safe, chemically stable, and produces anti-cancer effects in a human xenograft model of melanoma. We believe these results suggest a role for ALOS4 in an integrin-mediated pathway in exerting its anti-cancer effects possibly through immune response modulation.

Integrins as attractive targets for cancer therapeutics

Integrins are transmembrane receptors that have been implicated in the biology of various human physiological and pathological processes. These molecules facilitate cell–extracellular matrix and cell–cell interactions, and they have been implicated in fibrosis, inflammation, thrombosis, and tumor metastasis. The role of integrins in tumor progression makes them promising targets for cancer treatment, and certain integrin antagonists, such as antibodies and synthetic peptides, have been effectively utilized in the clinic for cancer therapy. Here, we discuss the evidence and knowledge on the contribution of integrins to cancer biology. Furthermore, we summarize the clinical attempts targeting this family in anti-cancer therapy development.

AKT in Bone Metastasis of Solid Tumors: A Comprehensive Review

Simple Summary

Bone metastasis is a frequent complication of solid tumors and leads to a reduced overall survival. Although much progress has been made in the field of tumor therapy in the last years, bone metastasis depicts a stage of the disease with a lack of appropriate therapeutical options. Hence, this review aims to present the role of AKT in bone metastasis of solid tumors to place the spotlight on AKT as a possible therapeutical approach for patients with bone metastases. Furthermore, we intended to discuss postulated underlying molecular mechanisms of the bone metastasis-promoting effect of AKT, especially in highly bone-metastatic breast, prostate, and lung cancer. To conclude, this review identified the AKT kinase as a potential therapeutical target in bone metastasis and revealed remaining questions, which need to be addressed in further research projects.

Abstract

Solid tumors, such as breast cancer and prostate cancer, often form bone metastases in the course of the disease. Patients with bone metastases frequently develop complications, such as pathological fractures or hypercalcemia and exhibit a reduced life expectancy. Thus, it is of vital importance to improve the treatment of bone metastases. A possible approach is to target signaling pathways, such as the PI3K/AKT pathway, which is frequently dysregulated in solid tumors. Therefore, we sought to review the role of the serine/threonine kinase AKT in bone metastasis. In general, activation of AKT signaling was shown to be associated with the formation of bone metastases from solid tumors. More precisely, AKT gets activated in tumor cells by a plethora of bone-derived growth factors and cytokines. Subsequently, AKT promotes the bone-metastatic capacities of tumor cells through distinct signaling pathways and secretion of bone cell-stimulating factors. Within the crosstalk between tumor and bone cells, also known as the vicious cycle, the stimulation of osteoblasts and osteoclasts also causes activation of AKT in these cells. As a consequence, bone metastasis is reduced after experimental inhibition of AKT. In summary, AKT signaling could be a promising therapeutical approach for patients with bone metastases of solid tumors.

RGD-Binding Integrins Revisited: How Recently Discovered Functions and Novel Synthetic Ligands (Re-)Shape an Ever-Evolving Field

Simple Summary

Integrins, a superfamily of cell adhesion receptors, were extensively investigated as therapeutic targets over the last decades, motivated by their multiple functions, e.g., in cancer (progression, metastasis, angiogenesis), sepsis, fibrosis, and viral infections. Although integrin-targeting clinical trials, especially in cancer, did not meet the high expectations yet, integrins remain highly interesting therapeutic targets. In this article, we analyze the state-of-the-art knowledge on the roles of a subfamily of integrins, which require binding of the tripeptide motif Arg-Gly-Asp (RGD) for cell adhesion and signal transduction, in cancer, in tumor-associated exosomes, in fibrosis and SARS-CoV-2 infection. Furthermore, we outline the latest achievements in the design and development of synthetic ligands, which are highly selective and affine to single integrin subtypes, i.e., αvβ3, αvβ5, α5β1, αvβ6, αvβ8, and αvβ1. Lastly, we present the substantial progress in the field of nuclear and optical molecular imaging of integrins, including first-in-human and clinical studies.

Abstract

Integrins have been extensively investigated as therapeutic targets over the last decades, which has been inspired by their multiple functions in cancer progression, metastasis, and angiogenesis as well as a continuously expanding number of other diseases, e.g., sepsis, fibrosis, and viral infections, possibly also Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). Although integrin-targeted (cancer) therapy trials did not meet the high expectations yet, integrins are still valid and promising targets due to their elevated expression and surface accessibility on diseased cells. Thus, for the future successful clinical translation of integrin-targeted compounds, revisited and innovative treatment strategies have to be explored based on accumulated knowledge of integrin biology. For this, refined approaches are demanded aiming at alternative and improved preclinical models, optimized selectivity and pharmacological properties of integrin ligands, as well as more sophisticated treatment protocols considering dose fine-tuning of compounds. Moreover, integrin ligands exert high accuracy in disease monitoring as diagnostic molecular imaging tools, enabling patient selection for individualized integrin-targeted therapy. The present review comprehensively analyzes the state-of-the-art knowledge on the roles of RGD-binding integrin subtypes in cancer and non-cancerous diseases and outlines the latest achievements in the design and development of synthetic ligands and their application in biomedical, translational, and molecular imaging approaches. Indeed, substantial progress has already been made, including advanced ligand designs, numerous elaborated pre-clinical and first-in-human studies, while the discovery of novel applications for integrin ligands remains to be explored.

Differential expression of αVβ3 and αVβ6 integrins in prostate cancer progression

Neuroendocrine prostate cancer (NEPrCa) arises de novo or after accumulation of genomic alterations in pre-existing adenocarcinoma tumors in response to androgen deprivation therapies. We have provided evidence that small extracellular vesicles released by PrCa cells and containing the αVβ3 integrin promote neuroendocrine differentiation of PrCa in vivo and in vitro. Here, we examined αVβ3 integrin expression in three murine models carrying a deletion of PTEN (SKO), PTEN and RB1 (DKO), or PTEN, RB1 and TRP53 (TKO) genes in the prostatic epithelium; of these three models, the DKO and TKO tumors develop NEPrCa with a gene signature comparable to those of human NEPrCa. Immunostaining analysis of SKO, DKO and TKO tumors shows that αVβ3 integrin expression is increased in DKO and TKO primary tumors and metastatic lesions, but absent in SKO primary tumors. On the other hand, SKO tumors show higher levels of a different αV integrin, αVβ6, as compared to DKO and TKO tumors. These results are confirmed by RNA-sequencing analysis. Moreover, TRAMP mice, which carry NEPrCa and adenocarcinoma of the prostate, also have increased levels of αVβ3 in their NEPrCa primary tumors. In contrast, the αVβ6 integrin is only detectable in the adenocarcinoma areas. Finally, analysis of 42 LuCaP patient-derived xenografts and primary adenocarcinoma samples shows a positive correlation between αVβ3, but not αVβ6, and the neuronal marker synaptophysin; it also demonstrates that αVβ3 is absent in prostatic adenocarcinomas. In summary, we demonstrate that αVβ3 integrin is upregulated in NEPrCa primary and metastatic lesions; in contrast, the αVβ6 integrin is confined to adenocarcinoma of the prostate. Our findings suggest that the αVβ3 integrin, but not αVβ6, may promote a shift in lineage plasticity towards a NE phenotype and might serve as an informative biomarker for the early detection of NE differentiation in prostate cancer.

Small extracellular vesicles modulated by αVβ3 integrin induce neuroendocrine differentiation in recipient cancer cells

The ability of small extracellular vesicles (sEVs) to reprogram cancer cells is well established. However, the specific sEV components able to mediate aberrant effects in cancer cells have not been characterized. Integrins are major players in mediating sEV functions. We have previously reported that the αVβ3 integrin is detected in sEVs of prostate cancer (PrCa) cells and transferred into recipient cells. Here, we investigate whether sEVs from αVβ3-expressing cells affect tumour growth differently than sEVs from control cells that do not express αVβ3. We compared the ability of sEVs to stimulate tumour growth, using sEVs isolated from PrCa C4-2B cells by iodixanol density gradient and characterized with immunoblotting, nanoparticle tracking analysis, immunocapturing and single vesicle analysis. We incubated PrCa cells with sEVs and injected them subcutaneously into nude mice to measure in vivo tumour growth or analysed in vitro their anchorage-independent growth. Our results demonstrate that a single treatment with sEVs shed from C4-2B cells that express αVβ3, but not from control cells, stimulates tumour growth and induces differentiation of PrCa cells towards a neuroendocrine phenotype, as quantified by increased levels of neuroendocrine markers. In conclusion, the expression of αVβ3 integrin generates sEVs capable of reprogramming cells towards an aggressive phenotype.

Unlocking Golgi: Why Does Morphology Matter?

The mammalian Golgi apparatus is a highly dynamic organelle, which is normally localized in the juxtanuclear space and plays an essential role in the regulation of cellular homeostasis. While posttranslational modification of cargo is mediated by the resident enzymes (glycosyltransferases, glycosidases, and kinases), the ribbon structure of Golgi and its cisternal stacking mostly rely on the cooperation of coiled-coil matrix golgins. Among them, giantin, GM130, and GRASPs are unique, because they form a tripartite complex and serve as Golgi docking sites for cargo delivered from the endoplasmic reticulum (ER). Golgi undergoes significant disorganization in many pathologies associated with a block of the ER-to-Golgi or intra-Golgi transport, including cancer, different neurological diseases, alcoholic liver damage, ischemic stress, viral infections, etc. In addition, Golgi fragments during apoptosis and mitosis. Here, we summarize and analyze clinically relevant observations indicating that Golgi fragmentation is associated with the selective loss of Golgi residency for some enzymes and, conversely, with the relocation of some cytoplasmic proteins to the Golgi. The central concept is that ER and Golgi stresses impair giantin docking site but have no impact on the GM130-GRASP65 complex, thus inducing mislocalization of giantin-sensitive enzymes only. This cardinally changes the processing of proteins by eliminating the pathways controlled by the missing enzymes and by activating the processes now driven by the GM130-GRASP65-dependent proteins. This type of Golgi disorganization is different from the one induced by the cytoskeleton alteration, which despite Golgi de-centralization, neither impairs function of golgins nor alters trafficking.

Methods for Evaluation of a Snake Venom-Derived Disintegrin in Animal Models of Human Cancer

Integrin targeting has been shown to be an effective approach for anticancer therapy. We engineered a recombinant disintegrin, vicrostatin (VCN), that binds with high affinity and specificity to the Arg-Gly-Asp (RGD) class of integrins, including αvβ3, αvβ5, and α5β1, involved in tumor invasion and metastasis. We used three different delivery modalities to examine anticancer activity of VCN in mouse models of human ovarian cancer, glioma, and prostate cancer. A female mouse model was used to examine the treatment of established ovarian cancer (OC) using VCN delivered intraperitoneally (IP) weekly either in saline or impregnated in a viscoelastic gel. SKOV3^luc cells (a human OC cell line) were directly injected IP into immunodeficient mice. We also examined the antitumor activity of radioiodinated VCN delivered intravenously in a human glioma model in nude mice. We evaluated the effectiveness of ¹³¹I-VCN in combination with the DNA alkylating agent temozolomide in limiting glioma growth. Finally, treatment of a bone metastatic model of human prostate cancer (PC) in immunodeficient mice was examined using a liposomal formulation of VCN (LVCN) delivered intravenously. Human PC cells were suspended in a solution of Matrigel and injected into the left tibia of immunodeficient mice. Diameters of both the left and right (control) tibias were measured by caliper repeatedly after VCN treatment was initiated.

Targeting the TMPRSS2/ERG fusion mRNA using liposomal nanovectors enhances docetaxel treatment in prostate cancer

BACKGROUND

The TMPRSS2/ERG (TE) fusion gene is present in half of the prostate cancers (PCas). The TMPRSS2 and ERG junction of the fusion messenger RNA (mRNA) constitutes a cancer-specific target. Although docetaxel-based chemotherapy is the second line of therapy following development resistance to androgen ablation therapies, it is not curative. Therefore, the development of nontoxic novel monotherapies for targeting TE mRNA in PCa patients and for increasing the clinical efficacy of docetaxel treatment are needed.

METHODS

We evaluated multiple approaches to enhance the delivery of TE small interfering RNA (siRNA) containing liposomes including PEGylation, topical treatment with nitroglycerin (NG) to increase permeability and retention, and three different PEG modifications: folate, RGD cyclic peptide, and a bFGF fibroblast growth factor receptor-targeting peptide. The efficacy of the optimized TE siRNA liposome in combination with docetaxel was then evaluated in vivo with or without topical NG in vivo using a VCaP xenograft model. TE fusion protein knockdown in residual tumors was assessed using Western blotting and immunohistochemistry.

RESULTS

In vivo therapeutic targeting of TE fusion gene by systemic delivery of RGD-peptide-coated liposomal siRNA nanovectors led to sustained target silencing, suppressed tumor growth in xenograft models and enhanced the efficacy of docetaxel chemotherapy. Simultaneous application of the vasodilator NG to the skin further increased tissue the delivery of siRNA and enhanced target knockdown.

CONCLUSION

TE-targeted gene silencing therapy using liposomal nanovectors is a potential therapeutic strategy as a monotherapy and to enhance the efficacy of chemotherapy in patients with advanced PCa.

Post-ER Stress Biogenesis of Golgi Is Governed by Giantin

BACKGROUND

The Golgi apparatus undergoes disorganization in response to stress, but it is able to restore compact and perinuclear structure under recovery. This self-organization mechanism is significant for cellular homeostasis, but remains mostly elusive, as does the role of giantin, the largest Golgi matrix dimeric protein.

METHODS

In HeLa and different prostate cancer cells, we used the model of cellular stress induced by Brefeldin A (BFA). The conformational structure of giantin was assessed by proximity ligation assay and atomic force microscopy. The post-BFA distribution of Golgi resident enzymes was examined by 3D SIM high-resolution microscopy.

RESULTS

We detected that giantin is rather flexible than an extended coiled-coil dimer and BFA-induced Golgi disassembly was associated with giantin monomerization. A fusion of the nascent Golgi membranes after BFA washout is forced by giantin re-dimerization via disulfide bond in its luminal domain and assisted by Rab6a GTPase. GM130-GRASP65-dependent enzymes are able to reach the nascent Golgi membranes, while giantin-sensitive enzymes appeared at the Golgi after its complete recovery via direct interaction of their cytoplasmic tail with N-terminus of giantin.

CONCLUSION

Post-stress recovery of Golgi is conducted by giantin dimer and Golgi proteins refill membranes according to their docking affiliation rather than their intra-Golgi location.

Targeting Integrins in Cancer Nanomedicine: Applications in Cancer Diagnosis and Therapy

Due to advancements in nanotechnology, the application of nanosized materials (nanomaterials) in cancer diagnostics and therapeutics has become a leading area in cancer research. The decoration of nanomaterial surfaces with biological ligands is a major strategy for directing the actions of nanomaterials specifically to cancer cells. These ligands can bind to specific receptors on the cell surface and enable nanomaterials to actively target cancer cells. Integrins are one of the cell surface receptors that regulate the communication between cells and their microenvironment. Several integrins are overexpressed in many types of cancer cells and the tumor microvasculature and function in the mediation of various cellular events. Therefore, the surface modification of nanomaterials with integrin-specific ligands not only increases their binding affinity to cancer cells but also enhances the cellular uptake of nanomaterials through the intracellular trafficking of integrins. Moreover, the integrin-specific ligands themselves interfere with cancer migration and invasion by interacting with integrins, and this finding provides a novel direction for new treatment approaches in cancer nanomedicine. This article reviews the integrin-specific ligands that have been used in cancer nanomedicine and provides an overview of the recent progress in cancer diagnostics and therapeutic strategies involving the use of integrin-targeted nanomaterials.

Altered Cell Adhesion and Glycosylation Promote Cancer Immune Suppression and Metastasis

Cell-cell interactions and cell adhesion are key mediators of cancer progression and facilitate hallmarks of cancer including immune evasion and metastatic dissemination. Many cell adhesion molecules within the tumor microenvironment are changed and significant alterations of glycosylation are observed. These changes in cell adhesion molecules alter the ability of tumor cells to interact with other cells and extracellular matrix proteins. Three families of cell-cell interaction molecules selectins, Siglecs, and integrins have been associated with cancer progression in many pre-clinical studies, yet inhibition of cell adhesion as a therapeutic target is just beginning to be explored. We review how cell-cell interactions mediated by integrins and the glycan-binding receptors selectins and Siglec receptors support cancer progression. The discussion focuses on mechanisms during immune evasion and metastasis that can be therapeutically targeted by blocking these cell-cell interactions.

H19-Dependent Transcriptional Regulation of β3 and β4 Integrins Upon Estrogen and Hypoxia Favors Metastatic Potential in Prostate Cancer

Estrogen and hypoxia promote an aggressive phenotype in prostate cancer (PCa), driving transcription of progression-associated genes. Here, we molecularly dissect the contribution of long non-coding RNA H19 to PCa metastatic potential under combined stimuli, a topic largely uncovered. The effects of estrogen and hypoxia on H19 and cell adhesion molecules’ expression were investigated in PCa cells and PCa-derived organotypic slice cultures (OSCs) by qPCR and Western blot. The molecular mechanism was addressed by chromatin immunoprecipitations, overexpression, and silencing assays. PCa cells’ metastatic potential was analyzed by in vitro cell-cell adhesion, motility test, and trans-well invasion assay. We found that combined treatment caused a significant H19 down-regulation as compared with hypoxia. In turn, H19 acts as a transcriptional repressor of cell adhesion molecules, as revealed by up-regulation of both β3 and β4 integrins and E-cadherin upon H19 silencing or combined treatment. Importantly, H19 down-regulation and β integrins induction were also observed in treated OSCs. Combined treatment increased both cell motility and invasion of PCa cells. Lastly, reduction of β integrins and invasion was achieved through epigenetic modulation of H19-dependent transcription. Our study revealed that estrogen and hypoxia transcriptionally regulate, via H19, cell adhesion molecules redirecting metastatic dissemination from EMT to a β integrin-mediated invasion.

Characterization of CD44 intracellular domain interaction with RUNX2 in PC3 human prostate cancer cells

BACKGROUND

Expression of CD44 receptor is associated with the onset of several tumors. The intracellular domain of CD44 (CD44-ICD) has been implicated as a co-transcription factor for RUNX2 in the regulation of expression of MMP-9 in breast carcinoma cells. Previous studies from our laboratory demonstrated the role of CD44 in migration and invasion of PC3 prostate cells through activation of MMP-9. CD44 signaling regulates the phosphorylation and hence the localization of RUNX2 in the nucleus. The role of CD44-ICD has not been studied in prostate cancer cells. This study aimed to explore the role of CD44-ICD and RUNX2 in the regulation of expression of metastasis-related genes.

METHODS

PC3 and PC3 cells overexpressing RUNX2 protein were analyzed for RUNX2/CD44-ICD interaction by immunoprecipitation, immunoblotting, and Immunofluorescence analyses. Wound healing and tumorsphere formation analyses were also done in these cells. The real-time PCR analysis was used to detect the expression levels of different genes.

RESULTS

Expression of CD44 and RUNX2 was observed only in PC3 cells (androgen receptor positive) and not in LNCaP or PCa2b cells (androgen receptor negative). Therefore, CD44-ICD fragment (~ 15-16 kDa) was observed in PC3 cells. Moreover, localization of CD44-ICD was more in the nucleus than in the cytoplasm of PC3 cells. Inhibition of cleavage of CD44 with a γ-secretase inhibitor, DAPT reduced the formation of CD44-ICD; however, accumulation of CD44-external truncation fragments (~ 20 and ~ 25 kDa) was detected. RUNX2 and CD44-ICD interact in the nucleus of PC3 cells, and this interaction was more in PC3 cells transfected with RUNX2 cDNA. Overexpression of RUNX2 augments the expression of metastasis-related genes (e.g., MMP-9 and osteopontin) which resulted in increased migration and tumorsphere formation.

CONCLUSIONS

We have shown here a strong functional relationship between CD44-ICD and RUNX2 in PC3 cells. RUNX2 forms a complex with CD44-ICD as a co-transcriptional factor, and this complex formation not only activates the expression of metastasis-related genes but also contributes to migration and tumorsphere formation. Therefore, RUNX2 and CD44-ICD are potential targets for anti-cancer therapy, and attenuation of their interaction may validate the regulatory effects of these proteins on cancer migration and progression.

Effect of genetic variants in cell adhesion pathways on the biochemical recurrence in prostate cancer patients with radical prostatectomy

The aberrant expression of cell adhesion molecules is a hallmark of epithelial‐to‐mesenchymal transition, resulting in the transformation of cancer cells to a more aggressive phenotype. This study investigated the association between genetic variants in cell adhesion pathways and the prognosis of patients with prostate cancer following radical prostatectomy (RP). A total of 18 haplotype‐tagging single‐nucleotide polymorphisms (SNPs) in eight cancer‐related adhesion molecules were genotyped in 458 prostate cancer patients, followed by the replication of the top SNPs in an additional set of 185 patients. Log‐rank test and multivariate Cox regression analysis adjusted for covariates were used to evaluate associations with the risk of biochemical recurrence (BCR) after RP. In the discovery set, four SNPs in CDH2 were marginally associated with BCR. Among these, CDH2 rs643555C > T was found to be associated with BCR in the replication set. Patients with rs643555TT genotype had a significantly shorter BCR‐free survival compared with those with CC/CT genotypes in the combined analysis (adjusted hazard ratio 1.78, 95% confidence interval 1.19‐2.67, P = 0.005). Additional analyses revealed that rs643555T was associated with higher expression of CDH2, and upregulated CDH2 was correlated with tumor aggressiveness and shortened BCR‐free survival. In conclusion, rs643555C > T affects CDH2 expression, and thus influences BCR in localized prostate cancer patients treated with RP. CDH2 rs643555 may be a promising biomarker to identify patients at high risk of poor prostate cancer prognosis.

Ligustrazine recovers thiram-induced tibial dyschondroplasia in chickens: Involvement of new molecules modulating integrin beta 3

Tetramethyl thiuram disulfide (thiram) is a dithiocarbamate, which is extensively used in agriculture as pesticide and fungicide for treating grains intended for seed purposes and also for storing food grains. One of the most evident and detrimental effect produced by thiram is tibial dyschondroplasia (TD) in many avian species, by feeding diets containing thiram, a growth plate cartilage disease. TD is characterized by the lack of blood vessels and impaired vascular invasion of the hypertrophic chondrocyte resulting in the massive cell death. This study investigated the effects of ligustrazine on the treatment and control of thiram induced-TD. A total of 210 chicks were divided into three equal groups (n = 70): control group (received standard diet), TD group (feed on thiram containing diet from day 3-7), and ligustrazine group (feed on thiram containing diet from day 3-7 and after that ligustrazine @ 30 mg/kg from day 8 to day 18). During the experiment, the lameness, production parameters, tibia bone indicators, pathological index changes and integrin beta 3 (ITGB3) expressions were examined. The results reveal that ligustrazine plays an important role in improving angiogenesis and decreasing chondrocytes damage in TD chicks via a new molecule modulating ITGB3. So, the administration of ligustrazine can be an important way to cope with the losses and costs associated with TD in commercial poultry farming and animal welfare issue due to environmental contamination of thiram.

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.

Regulatory signaling network in the tumor microenvironment of prostate cancer bone and visceral organ metastases and the development of novel therapeutics

This article describes cell signaling network of metastatic prostate cancer (PCa) to bone and visceral organs in the context of tumor microenvironment and for the development of novel therapeutics. The article focuses on our recent progress in the understanding of: 1) The plasticity and dynamics of tumor–stroma interaction; 2) The significance of epigenetic reprogramming in conferring cancer growth, invasion and metastasis; 3) New insights on altered junctional communication affecting PCa bone and brain metastases; 4) Novel strategies to overcome therapeutic resistance to hormonal antagonists and chemotherapy; 5) Genetic-based therapy to co-target tumor and bone stroma; 6) PCa-bone-immune cell interaction and TBX2-WNTprotein signaling in bone metastasis; 7) The roles of monoamine oxidase and reactive oxygen species in PCa growth and bone metastasis; and 8) Characterization of imprinting cluster of microRNA, in tumor–stroma interaction. This article provides new approaches and insights of PCa metastases with emphasis on basic science and potential for clinical translation. This article referenced the details of the various approaches and discoveries described herein in peer-reviewed publications. We dedicate this article in our fond memory of Dr. Donald S. Coffey who taught us the spirit of sharing and the importance of focusing basic science discoveries toward translational medicine.

Osteopontin Plasma Level Does Not Detect Prostate Cancer in Patients Referred for Diagnostic Prostate Biopsy

Background

Prostate cancer is the second most frequent cause of tumor-related deaths in men in Western countries. The selection and evaluation of new markers might help to overcome the limits of the most widely used diagnostic tool, the prostate-specific antigen (PSA) test, often combined with digital rectal examination (DRE). Osteopontin (OPN) is an integrin-binding glycoprotein that has recently been shown to be related to tumor development, progression and metastasis in both experimental and clinical studies. The present study compares plasma OPN levels and tumor presence and grade in a group of PSA/DRE-positive patients referred for diagnostic prostate biopsy.

Methods

Plasma OPN levels were measured by enzyme-linked immunosorbent assay in blood samples of 194 PSA/DRE-positive patients referred for diagnostic prostate biopsy. OPN measurements were compared with PSA levels and tumor presence and grade as established by needle biopsy.

Results

Plasma OPN levels were not increased in patients with prostate cancer, and in patients with high-grade prostate cancer the plasma OPN levels were not different from those in patients with low-grade or no prostate cancer.

Conclusions

In PSA/DRE-positive patients referred for diagnostic prostate biopsy, OPN does not appear to be a plasma marker able to detect prostate cancer or high-grade prostate cancer.

Bone Marrow Microenvironment as a Regulator and Therapeutic Target for Prostate Cancer Bone Metastasis

Bone is the most common site of prostate cancer metastasis. Once prostate cancer cells metastasize to bone, the mortality rate of prostate cancer patients increases significantly. Furthermore, bone metastases produce multiple skeletal complications, including bone pain that impairs the patients' quality of life. Effective therapies for bone metastatic disease are underdeveloped with most current therapies being primarily palliative with modest survival benefit. Although the exact mechanisms through which prostate cancer metastasizes to bone are unclear, growing evidence suggests that the bone marrow microenvironment, particularly its hematopoietic activity, is a significant mediator of prostate cancer bone tropism. Moreover, the bone microenvironment may regulate metastatic prostate cancer cells between dormant and proliferative states. In this review, we discuss (1) how prostate cancer cells interact with the bone microenvironment to establish bone metastases and (2) current and future potential treatments for prostate cancer patients with bone metastases.

BKCa promotes growth and metastasis of prostate cancer through facilitating the coupling between αvβ3 integrin and FAK

BKCa is a large conductance calcium activated potassium channel promoting prostate cancer cell proliferation, although the mechanism is not fully elucidated. In addition, whether BKCa is involved in metastasis of prostate cancer remains to be explored. Here, we report that BKCa is overexpressed in prostate cancer. BKCa expression positively correlates with Ki67 index and gleason score of prostate cancer. Upregulation of BKCa promoted proliferation, migration and invasion of prostate cancer cells. On the contrary, downregulation of BKCa inhibited growth and metastasis of prostate cancer cells both in vitro and in vivo. Moreover, the ion-conducting function of BKCa contributed moderately to prostate cancer proliferation and migration, although, this was not the primary mechanism. BKCa action was mainly mediated through forming a functional complex with αvβ3 integrin. The BKCa/αvβ3 integrin complex promoted FAK phosphorylation independent of the channel activity. Overexpression of BKCa enhanced its association with αvβ3 integrin and FAK which increased FAK phosphorylation. Conversely, disrupting the complex by downregulation of BKCa reduced FAK phosphorylation. Finally, blocking of αvβ3 integrin or p-FAK activity using LM609 or Y15 markedly abrogated BKCa-enhanced cell proliferation and migration. Taken together, these results suggest that targeting BKCa/αvβ3/FAK may inaugurate innovative approaches to inhibit prostate cancer growth and metastasis.

Rare-Earth-Doped Nanoparticles for Short-Wave Infrared Fluorescence Bioimaging and Molecular Targeting of αVβ3-Expressing Tumors

The use of short-wave infrared (SWIR) light for fluorescence bioimaging offers the advantage of reduced photon scattering and improved tissue penetration compared to traditional shorter wavelength imaging approaches. While several nanomaterials have been shown capable of generating SWIR emissions, rare-earth-doped nanoparticles (REs) have emerged as an exceptionally bright and biocompatible class of SWIR emitters. Here, we demonstrate SWIR imaging of REs for several applications, including lymphatic mapping, real-time monitoring of probe biodistribution, and molecular targeting of the αvβ3 integrin in a tumor model. We further quantified the resolution and depth penetration limits of SWIR light emitted by REs in a customized imaging unit engineered for SWIR imaging of live small animals. Our results indicate that SWIR light has broad utility for preclinical biomedical imaging and demonstrates the potential for molecular imaging using targeted REs.

Decreased Expression of miR-548c-3p in Osteosarcoma Contributes to Cell Proliferation Via Targeting ITGAV

The members of the integrin αv (ITGAV) family are widely expressed on many types of tumors and have been reported to be involved into angiogenesis, tumor metastases, and multicellular radioresistance. Osteosarcoma (OS) is the most common primary malignant bone tumor and the role of ITGAV in OS needs to be further elucidated. MicroRNAs are aberrantly expressed in a variety of cancers. Thus, the authors collected OS tissues (n = 15) and corresponding paracancerous tissues (n = 15) and found that the expression of miR-548c-3p was significantly downregulated in OS tissues and cell lines 143B, SaoS2, and HOS when compared to the corresponding paracancerous tissues and human osteoblast cell line hFOB (OB3), respectively. In addition, the authors identified that miR-548c-3p could directly target the 3'-untranslated region of ITGAV, and miR-548c-3p overexpression inhibits the mRNA and protein levels of ITGAV, which were confirmed by the luciferase reporter assays. Interestingly, they also uncovered that miR-548c-3p overexpression or knockdown of ITGAV remarkably suppressed cell vitality and promoted apoptosis and G2/M cell cycle arrest, leading to abrogating the ability of colony formation. The results indicated that the miR-548c-3p, similar to the target agents against integrin αv in clinical trials, could negatively regulate the ITGAV and be a promising tumor therapeutic target.

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.

Proteolytic fragments of fibronectin function as matrikines driving the chemotactic affinity of prostate cancer cells to human bone marrow mesenchymal stromal cells via the α5β1 integrin

The haematopoietic niche is contributed to by bone marrow-resident mesenchymal stromal cells (BM-MSCs) and subverted by prostate cancer cells. To study mechanisms by which BM-MSCs and prostate cancer cells may interact, we assessed the migration, invasion, adhesion and proliferation of bone-derived prostate cancer cells (PC-3) in co-culture with pluripotent human BM-MSCs. We observed a strong adhesive, migratory and invasive phenotype of PC-3 cells with BM- MSC-co-culture and set out to isolate and characterize the bioactive principle. Initial studies indicated that chemotaxis was secondary to a protein residing in the >100kDa fraction. Size-exclusion chromatography (SEC) recovered peak activity in a high-molecular weight fraction containing thrombospondin-1 (TSP1). While TSP1 immunodepletion decreased activity, put-back with purified TSP1 did not reproduce bioactivity. Further purification of the TSP1-containing high-molecular weight fraction of the BM-MSC secretome with heparin-affinity chromatography recovered bioactivity with highly restricted bands on polyacrylamide gel electrophoresis, determined by mass spectroscopy to be proteolytic fragments of fibronectin (FN). Put-back experiments with full-length FN permitted adhesion but failed to induce migration. Monospecific antibodies to FN blocked adhesion. Proteolytic cleavage of FN generated FN fragments which now induced migration. Neutralizing monoclonal antibodies to FN receptors α5 and β1 integrins, and α5 knockdown specifically blocked migration and adhesion.

CONCLUSION

Fibronectin fragments (FNFr) function as matrikines driving the chemotactic affinity of prostate cancer cells via the α5β1 integrin. Taken together with the high-frequency of α5β1 expression in disseminated prostate cancer cells in bone marrow aspirates from patients, the FNFr/FN-α5β1 interaction warrants further study as a therapeutic target.

Radiolabeled cyclic RGD peptides as radiotracers for tumor imaging

The integrin family comprises 24 transmembrane receptors, each a heterodimeric combination of one of 18α and one of 8β subunits. Their main function is to integrate the cell adhesion and interaction with the extracellular microenvironment with the intracellular signaling and cytoskeletal rearrangement through transmitting signals across the cell membrane upon ligand binding. Integrin α_vβ₃ is a receptor for the extracellular matrix proteins containing arginine–glycine–aspartic (RGD) tripeptide sequence. The α_vβ₃ is generally expressed in low levels on the epithelial cells and mature endothelial cells, but it is highly expressed in many solid tumors. The α_vβ₃ levels correlate well with the potential for tumor metastasis and aggressiveness, which make it an important biological target for development of antiangiogenic drugs, and molecular imaging probes for early tumor diagnosis. Over the last decade, many radiolabeled cyclic RGD peptides have been evaluated as radiotracers for imaging tumors by SPECT or PET. Even though they are called “α_vβ₃-targeted” radiotracers, the radiolabeled cyclic RGD peptides are also able to bind α_vβ₅, α₅β₁, α₆β₄, α₄β₁, and α_vβ₆ integrins, which may help enhance their tumor uptake due to the “increased receptor population.” This article will use the multimeric cyclic RGD peptides as examples to illustrate basic principles for development of integrin-targeted radiotracers and focus on different approaches to maximize their tumor uptake and T/B ratios. It will also discuss important assays for pre-clinical evaluations of the integrin-targeted radiotracers, and their potential applications as molecular imaging tools for noninvasive monitoring of tumor metastasis and early detection of the tumor response to antiangiogenic therapy.

A prodrug-doped cellular Trojan Horse for the potential treatment of prostate cancer

Despite considerable advances in prostate cancer research, there is a major need for a systemic delivery platform that efficiently targets anti-cancer drugs to sites of disseminated prostate cancer while minimizing host toxicity. In this proof-of-principle study, human mesenchymal stem cells (MSCs) were loaded with poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) that encapsulate the macromolecule G114, a thapsigargin-based prostate specific antigen (PSA)-activated prodrug. G114-particles (∼950 nm in size) were internalized by MSCs, followed by the release of G114 as an intact prodrug from loaded cells. Moreover, G114 released from G114 MP-loaded MSCs selectively induced death of the PSA-secreting PCa cell line, LNCaP. Finally, G114 MP-loaded MSCs inhibited tumor growth when used in proof-of-concept co-inoculation studies with CWR22 PCa xenografts, suggesting that cell-based delivery of G114 did not compromise the potency of this pro-drug in-vitro or in-vivo. This study demonstrates a potentially promising approach to assemble a cell-based drug delivery platform, which inhibits cancer growth in-vivo without the need of genetic engineering. We envision that upon achieving efficient homing of systemically infused MSCs to cancer sites, this MSC-based platform may be developed into an effective, systemic 'Trojan Horse' therapy for targeted delivery of therapeutic agents to sites of metastatic PCa.

Development of a novel cyclic RGD peptide for multiple targeting approaches of liposomes to tumor region

Liposomes containing cytotoxic agents and targeted with Arg-Gly-Asp based peptides have frequently been used against αvβ3 integrin on tumor neovasculature. However, like many other ligand modified liposomes these preparations suffered from enhanced uptake by the reticulo endothelial system (RES) and off-targeted interaction with integrin receptors vastly expressed in normal organs causing poor biodistribution and toxic effects. Here we mainly focus on development of a RGD-modified liposomal delivery system to enhance both targeting selectivity and tumor uptake. First, sterically stabilized liposomal doxorubicin (SSLD) prepared and decorated with cRGDfK and RGDyC peptides differ in their physical properties. Stability assessments as well as in vitro and in vivo studies revealed that increasing the peptide hydrophobicity promotes the therapeutic efficacy of RGD-SSLD in a C-26 tumor model due to decreased recognition by RES and opsonization and limited off-targeted interactions. Then a novel N-methylated RGD peptide was designed and its capability in targeting integrin presenting cells was comprehensively assessed both in vitro and in vivo. RGDf[N-methyl]C promotes the liposome internalization by HUVEC via integrin mediated endocytosis. Intravital microscopy in window chamber bearing mice illustrated the capability of RGDf[N-methyl]C-liposomes in targeting both tumor vasculature and tumor cells in murine B16F0 and human BLM tumor models. Quantitative biodistribution in mice bearing B16F0 tumor revealed its high affinity to tumor with no considerable affinity to normal organs. Treatment by high dose of RGDf[N-methyl]C-SSLD was found more effective than non-targeted SSLD and no toxic side effect was observed. In conclusion, the RGDf[N-methyl]C-liposome was found promising in targeting tumor vasculature as well as other cells inside the tumor.

Radiolabeled Cyclic RGD Peptide Bioconjugates as Radiotracers Targeting Multiple Integrins

Angiogenesis is a requirement for tumor growth and metastasis. The angiogenic process depends on vascular endothelial cell migration and invasion, and is regulated by various cell adhesion receptors. Integrins are such a family of receptors that facilitate the cellular adhesion to and migration on extracellular matrix proteins in the intercellular spaces and basement membranes. Among 24 members of the integrin family, αvβ3 is studied most extensively for its role in tumor angiogenesis and metastasis. The αvβ3 is expressed at relatively low levels on epithelial cells and mature endothelial cells, but it is highly expressed on the activated endothelial cells of tumor neovasculature and some tumor cells. This restricted expression makes αvβ3 an excellent target to develop antiangiogenic drugs and diagnostic molecular imaging probes. Since αvβ3 is a receptor for extracellular matrix proteins with one or more RGD tripeptide sequence, many radiolabeled cyclic RGD peptides have been evaluated as "αvβ3-targeted" radiotracers for tumor imaging over the past decade. This article will use the dimeric and tetrameric cyclic RGD peptides developed in our laboratories as examples to illustrate basic principles for development of αvβ3-targeted radiotracers. It will focus on different approaches to maximize the radiotracer tumor uptake and tumor/background ratios. This article will also discuss some important assays for preclinical evaluations of integrin-targeted radiotracers. In general, multimerization of cyclic RGD peptides increases their integrin binding affinity and the tumor uptake and retention times of their radiotracers. Regardless of their multiplicity, the capability of cyclic RGD peptides to bind other integrins (namely, αvβ5, α5β1, α6β4, α4β1, and αvβ6) is expected to enhance the radiotracer tumor uptake due to the increased integrin population. The results from preclinical and clinical studies clearly show that radiolabeled cyclic RGD peptides (such as (99m)Tc-3P-RGD2, (18)F-Alfatide-I, and (18)F-Alfatide-II) are useful as the molecular imaging probes for early cancer detection and noninvasive monitoring of the tumor response to antiangiogenic therapy.

Mitotic quiescence, but not unique "stemness," marks the phenotype of bone metastasis-initiating cells in prostate cancer

This study aimed to identify subpopulations of prostate cancer cells that are responsible for the initiation of bone metastases. Using rapidly dividing human prostate cancer cell lines, we identified mitotically quiescent subpopulations (<1%), which we compared with the rapidly dividing populations for patterns of gene expression and for their ability to migrate to the skeletons of athymic mice. The study used 2-photon microscopy to map the presence/distribution of fluorescently labeled, quiescent cells and luciferase expression to determine the presence of growing bone metastases. We showed that the mitotically quiescent cells were very significantly more tumorigenic in forming bone metastases than fast-growing cells (55 vs. 15%) and had a unique gene expression profile. The quiescent cells were not uniquely stem cell like, with no expression of CD133 but had the same level expression of other putative prostate stem cell markers (CD44 and integrins α2/β1), when compared to the rapidly proliferating population. In addition, mitotic quiescence was associated with very high levels of C-X-C chemokine receptor type 4 (CXCR4) production. Inhibition of CXCR4 activity altered the homing of quiescent tumor cells to bone. Our studies suggest that mitotic dormancy is a unique phenotype that facilitates tumor cell colonization of the skeleton in prostate cancer.

Tumour but not stromal expression of β3 integrin is essential, and is required early, for spontaneous dissemination of bone-metastatic breast cancer

Although many preclinical studies have implicated β3 integrin receptors (αvβ3 and αIIbβ3) in cancer progression, β3 inhibitors have shown only modest efficacy in patients with advanced solid tumours. The limited efficacy of β3 inhibitors in patients could arise from our incomplete understanding of the precise function of β3 integrin and, consequently, inappropriate clinical application. Data from animal studies are conflicting and indicate heterogeneity with respect to the relative contributions of β3-expressing tumour and stromal cell populations in different cancers. Here we aimed to clarify the function and relative contributions to metastasis of tumour versus stromal β3 integrin in clinically relevant models of spontaneous breast cancer metastasis, with particular emphasis on bone metastasis. We show that stable down-regulation of tumour β3 integrin dramatically impairs spontaneous (but not experimental) metastasis to bone and lung without affecting primary tumour growth in the mammary gland. Unexpectedly, and in contrast to subcutaneous tumours, orthotopic tumour vascularity, growth and spontaneous metastasis were not altered in mice null for β3 integrin. Tumour β3 integrin promoted migration, protease expression and trans-endothelial migration in vitro and increased vascular dissemination in vivo, but was not necessary for bone colonization in experimental metastasis assays. We conclude that tumour, rather than stromal, β3 expression is essential and is required early for efficient spontaneous breast cancer metastasis to bone and soft tissues. Accordingly, differential gene expression analysis in cohorts of breast cancer patients showed a strong association between high β3 expression, early metastasis and shorter disease-free survival in patients with oestrogen receptor-negative tumours. We propose that β3 inhibitors may be more efficacious if used in a neoadjuvant setting, rather than after metastases are established.

Comparison of BTSE-RGD with DOTA-RGD as a potential imaging agent for tumors

RGD and its analogues are very important compounds and can be used as potential tumor-targeting agents.