CYR61 and alphaVbeta5 integrin cooperate to promote invasion and metastasis of tumors growing in preirradiated stroma

Metformin shows anti-neoplastic properties by inhibition of oxidative phosphorylation and glycolysis in epidermolysis bullosa-associated aggressive cutaneous squamous cell carcinoma

BACKGROUND

While most cutaneous squamous cell carcinomas (cSCCs) are treatable, certain high-risk cSCCs, such as those in recessive dystrophic epidermolysis bullosa (RDEB) patients, are particularly aggressive. Owing to repeated wounding, inflammation and unproductive healing, RDEB patients have a 68% cumulative risk of developing life-threatening cSCCs by the age of 35, and a 70% risk of death by the age of 45. Despite aggressive treatment, cSCC represents the leading cause of premature mortality in these patients, highlighting an unmet clinical need. Increasing evidence points to a role of altered metabolism in the initiation and maintenance of cSCC, making metabolism a potential therapeutic target.

OBJECTIVES

We sought to determine the feasibility of targeting tumour cell energetics as a strategy to selectively hinder the growth advantage of aggressive cSCC.

METHODS

We evaluated the cell energetics profiles of RDEB-SCC cells by analysing available gene expression data against multiple gene signatures and single-gene targets linked to metabolic reprogramming. Additionally, we employed real-time metabolic profiling to measure glycolysis and respiration in these cells. Furthermore, we investigated the anti-neoplastic properties of the metformin against human and murine high-risk cSCCs in vitro and in vivo.

RESULTS

Gene expression analyses highlighted a divergence in cell energetics profiles between RDEB-SCC and non-malignant RDEB keratinocytes, with tumour cells demonstrating enhanced respiration and glycolysis scores. Real-time metabolic profiling supported these data and additionally highlighted a metabolic plasticity of RDEB-SCC cells. Against this background, metformin exerted an anti-neoplastic potential by hampering both respiration and glycolysis, and by inhibiting proliferation in vitro. Metformin treatment in an analogous model of fast-growing murine cSCC resulted in delayed tumour onset and slower tumour growth, translating to a 29% increase in median overall survival.

CONCLUSIONS

Our data indicate that metformin exerts anti-neoplastic properties in aggressive cSCCs that exhibit high-risk features by interfering with respiration and glycolytic processes.

CD248 promotes migration and metastasis of osteosarcoma through ITGB1-mediated FAK-paxillin pathway activation

BACKGROUND

Osteosarcoma (OS) is the most common malignant bone tumor with a high incidence in children and adolescents. Frequent tumor metastasis and high postoperative recurrence are the most common challenges in OS. However, detailed mechanism is largely unknown.

METHODS

We examined the expression of CD248 in OS tissue microarrays by immunohistochemistry (IHC) staining. We studied the biological function of CD248 in cell proliferation, invasion and migration of OS cells by CCK8 assay, transwell and wound healing assay. We also studied its function in the metastasis of OS in vivo. At last, we explored the potential mechanism how CD248 promotes OS metastasis by using RNA-seq, western blot, immunofluorescence staining and co-immunoprecipitation using CD248 knockdown OS cells.

RESULTS

CD248 was highly expressed in OS tissues and its high expression was correlated with pulmonary metastasis of OS. Knockdown of CD248 in OS cells significantly inhibited cell migration, invasion and metastasis, while had no obvious effect on cell proliferation. Lung metastasis in nude mice was significantly inhibited when CD248 was knocked down. Mechanistically, we found that CD248 could promote the interaction between ITGB1 and extracellular matrix (ECM) proteins like CYR61 and FN, which activated the FAK-paxillin pathway to promote the formation of focal adhesion and metastasis of OS.

CONCLUSION

Our data showed that high CD248 expression is correlated with the metastatic potential of OS. CD248 may promote migration and metastasis through enhancing the interaction between ITGB1 and certain ECM proteins. Therefore, CD248 is a potential marker for diagnosis and effective target for the treatment of metastatic OS.

Implications of hydrogen sulfide in colorectal cancer: Mechanistic insights and diagnostic and therapeutic strategies

Hydrogen sulfide (H₂S) is an important signaling molecule in colorectal cancer (CRC). It is produced in the colon by the catalytic synthesis of the colonocytes' enzymatic systems and the release of intestinal microbes, and is oxidatively metabolized in the colonocytes' mitochondria. Both endogenous H₂S in colonic epithelial cells and exogenous H₂S in intestinal lumen contribute to the onset and progression of CRC. The up-regulation of endogenous synthetases is thought to be the cause of the elevated H₂S levels in CRC cells. Different diagnostic probes and combination therapies, as well as tumor treatment approaches through H₂S modulation, have been developed in recent years and have become active area of investigation for the diagnosis and treatment of CRC. In this review, we focus on the specific mechanisms of H₂S production and oxidative metabolism as well as the function of H₂S in the occurrence, progression, diagnosis, and treatment of CRC. We also discuss the present challenges and provide insights into the future research of this burgeoning field.

Regulation of CyR61 expression and release by 3-mercaptopyruvate sulfurtransferase in colon cancer cells

Cysteine-rich angiogenic inducer 61 (CYR61, also termed CCN family member 1 or CCN1), is a matricellular protein encoded by the CYR61 gene. This protein has been implicated in the regulation of various cancer-associated processes including tumor growth, angiogenesis, tumor cell adhesion, migration, and invasion as well as the regulation of anticancer drug resistance. Hydrogen sulfide (H₂S) is a gaseous endogenous biological mediator, involved in the regulation of cellular bioenergetics, angiogenesis, invasion, and chemotherapeutic resistance in several types of cancer. H₂S is produced by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current studies were set up to investigate if CBS or 3-MST regulates CyR61 in colon cancer cells in the context of the regulation of proliferation, migration, and survival. The study mainly utilized HCT116 cells, in which two of the principal H₂S-producing enzymes, CBS and 3-MST, are highly expressed. The H₂S donor GYY4137 and the polysulfide donor Na₂S₃ activated the CyR61 promoter in a concentration-dependent fashion. Aminooxyacetic acid (AOAA), a pharmacological inhibitor of CBS as well as HMPSNE: 2-[(4-hydroxy-6- methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one, a pharmacological inhibitor of 3-MST inhibited CyR61 mRNA expression. This effect was more pronounced in response to HMPSNE than to AOAA and occurred through the modulation of S1PR via ATF1 and CREB. CyR61 was found to play an active, but relatively minor role in maintaining colon cell proliferation. HMPSNE markedly suppressed the secretion/release of CyR61 from the colon cancer cells. Moreover, HMPSNE promoted colon cancer cell apoptosis; endogenously produced CyR61 was found to counteract this effect, at least in part via RhoA activation. Taken together, we conclude that the upregulation of 3-MST in cancer cells exerts cytoprotective effects and confers the cancer cells a more aggressive phenotype - at least in part via the modulation of CyR61 expression and release.

Connexins orchestrate progression of breast cancer metastasis to the brain by promoting FAK activation

Brain metastasis is a complication of increasing incidence in patients with breast cancer at advanced disease stage. It is a severe condition characterized by a rapid decline in quality of life and poor prognosis. There is a critical clinical need to develop effective therapies to prevent and treat brain metastases. Here, we describe a unique and robust spontaneous preclinical model of breast cancer metastasis to the brain (4T1-BM₂) in mice that has been instrumental in uncovering molecular mechanisms guiding metastatic dissemination and colonization of the brain. Key experimental findings were validated in the additional murine D2A1-BM₂ model and in human MDA231-BrM₂ model. Gene expression analyses and functional studies, coupled with clinical transcriptomic and histopathological investigations, identified connexins (Cxs) and focal adhesion kinase (FAK) as master molecules orchestrating breast cancer colonization of the brain. Cx31 promoted homotypic tumor cell adhesion, heterotypic tumor-astrocyte interaction, and FAK phosphorylation. FAK signaling prompted NF-κB activation inducing Lamc2 expression and laminin 332 (laminin 5) deposition, α6 integrin-mediated adhesion, and sustained survival and growth within brain parenchyma. In the MDA231-BrM₂ model, the human homologous molecules CX43, LAMA4, and α3 integrin were involved. Systemic treatment with FAK inhibitors reduced brain metastasis progression. In conclusion, we report a spontaneous model of breast cancer metastasis to the brain and identified Cx-mediated FAK-NF-κB signaling as a mechanism promoting cell-autonomous and microenvironmentally controlled cell survival for brain colonization. Considering the limited therapeutic options for brain metastatic disease in cancer patients, we propose FAK as a therapeutic candidate to further pursue in the clinic.

Impact of Different [Tc(N)PNP]-Scaffolds on the Biological Properties of the Small cRGDfK Peptide: Synthesis, In Vitro and In Vivo Evaluations

Background: The [^99mTc][Tc(N)(PNP)] system, where PNP is a bisphosphinoamine, is an interesting platform for the development of tumor ‘receptor-specific’ agents. Here, we compared the reactivity and impact of three [Tc(N)(PNP)] frameworks on the stability, receptor targeting properties, biodistribution, and metabolism of the corresponding [^99mTc][Tc(N)(PNP)]-tagged cRGDfK peptide to determine the best performing agent and to select the framework useful for the preparation of [^99mTc][Tc(N)(PNP)]-housing molecular targeting agents. Methods: cRGDfK pentapeptide was conjugated to Cys and labeled with each [Tc(N)(PNP)] framework. Radioconjugates were assessed for their lipophilicity, stability, in vitro and in vivo targeting properties, and performance. Results: All compounds were equally synthetically accessible and easy to purify (RCY ≥ 95%). The main influences of the synthon on the targeting peptide were observed in in vitro cell binding and in vivo. Conclusions: The variation in the substituents on the phosphorus atoms of the PNP enables a fine tuning of the biological features of the radioconjugates. ws[^99mTc][Tc(N)(PNP3OH)]– and [^99mTc][Tc(N)(PNP3)]– are better performing synthons in terms of labeling efficiency and in vivo performance than the [^99mTc][Tc(N)(PNP43)] framework and are therefore more suitable for further radiopharmaceutical purposes. Furthermore, the good labeling properties of the ws[^99mTc][Tc(N)(PNP3OH)]– framework can be exploited to extend this technology to the labeling of temperature-sensitive biomolecules suitable for SPECT imaging.

Cyclic RGD-Decorated Liposomal Gossypol AT-101 Targeting for Enhanced Antitumor Effect

Introduction

(-)-Gossypol (AT-101), the (-)-enantiomer of the natural compound gossypol, has shown significant inhibitory effects on various types of cancers such as osteosarcoma, myeloma, glioma, lung cancer, and prostate cancer. However, the clinical application of (-)-gossypol was often hindered by its evident side effects and the low bioavailability via oral administration, which necessitated the development of suitable (-)-gossypol preparations to settle the problems. In this study, injectable cyclic RGD (cRGD)-decorated liposome (cRGD-LP) was prepared for tumor-targeted delivery of (-)-gossypol.

Methods

The cRGD-LP was prepared based on cRGD-modified lipids. For comparison, a non-cRGD-containing liposome (LP) with a similar chemical composition to cRGD-LP was specially designed. The physicochemical properties of (-)-gossypol-loaded cRGD-LP (Gos/cRGD-LP) were investigated in terms of the drug loading efficiency, particle size, morphology, drug release, and so on. The inhibitory effect of Gos/cRGD-LP on the proliferation of tumor cells in vitro was evaluated using different cell lines. The biodistribution of cRGD-LP in vivo was investigated via the near-infrared (NIR) fluorescence imaging technique. The antitumor effect of Gos/cRGD-LP in vivo was evaluated in PC-3 tumor-bearing nude mice.

Results

Gos/cRGD-LP had an average particle size of about 62 nm with a narrow size distribution, drug loading efficiency of over 90%, and sustained drug release for over 96 h. The results of NIR fluorescence imaging demonstrated the enhanced tumor targeting of cRGD-LP in vivo. Moreover, Gos/cRGD-LP showed a significantly enhanced inhibitory effect on PC-3 tumors in mice, with a tumor inhibition rate of over 74% and good biocompatibility.

Conclusion

The incorporation of cRGD could significantly enhance the tumor-targeting effect of the liposomes and improve the antitumor effect of the liposomal (-)-gossypol in vivo, which indicated the potential of Gos/cRGD-LP that warrants further investigation for clinical applications of this single-isomer drug.

Roles of Integrins in Gastrointestinal Cancer Metastasis

Integrins are a large family of heterodimeric transmembrane receptors which mediate cell adhesion and transmit signals to the cell interior. The mechanistic roles of integrins have long been an enigma in cancer, given its complexity in regulating different cellular behaviors. Recently, however, increasing research is providing new insights into its function and the underlying mechanisms, which collectively include the influences of altered integrin expression on the aberrant signaling pathways and cancer progression. Many studies have also demonstrated the potentiality of integrins as therapeutic targets in cancer treatment. In this review, we have summarized these recent reports and put a particular emphasis on the dysregulated expression of integrins and how they regulate related signaling pathways to facilitate the metastatic progression of gastrointestinal cancer, including gastric cancer (GC) and colorectal cancer (CRC), which will address the crucial roles of integrins in gastrointestinal cancer.

Plasminogen Regulates Fracture Repair by Promoting the Functions of Periosteal Mesenchymal Progenitors

Defective or insufficient bone repair and regeneration are common in patients as a result of major trauma or severe disease. Cell therapy with periosteal mesenchymal progenitors, which can be limited in severe injury, serves as a promising approach; however, its efficacy is limited due to a repair-hostile ischemic tissue microenvironment after traumatic fracture. Here we report that plasminogen (Plg), a factor that is upregulated in these environments, is critical for fracture healing. Plg knockout mice had impaired trabecular and cortical bone structure and exhibited delayed and incomplete fracture healing. Interestingly, Plg deficiency greatly reduced the thickness of expanded periosteum, suggesting a role of Plg in periosteal mesenchymal progenitor-mediated bone repair. In culture, Plg increased cell proliferation and migration in periosteal mesenchymal progenitors and inhibited cell death under ischemic conditions. Mechanistically, we revealed that Plg cleaved and activated Cyr61 to regulate periosteal progenitor function. Thus, our study uncovers a cellular mechanism underlying fracture healing, by which Plg activates Cyr61 to promote periosteal progenitor proliferation, survival, and migration and improves bone repair after fracture. Targeting Plg may offer a rational and effective therapeutic opportunity for improving fracture healing. © 2021 American Society for Bone and Mineral Research (ASBMR).

Integrins regulate stemness in solid tumor: an emerging therapeutic target

Integrins are the adhesion molecules and transmembrane receptors that consist of α and β subunits. After binding to extracellular matrix components, integrins trigger intracellular signaling and regulate a wide spectrum of cellular functions, including cell survival, proliferation, differentiation and migration. Since the pattern of integrins expression is a key determinant of cell behavior in response to microenvironmental cues, deregulation of integrins caused by various mechanisms has been causally linked to cancer development and progression in several solid tumor types. In this review, we discuss the integrin signalosome with a highlight of a few key pro-oncogenic pathways elicited by integrins, and uncover the mutational and transcriptomic landscape of integrin-encoding genes across human cancers. In addition, we focus on the integrin-mediated control of cancer stem cell and tumor stemness in general, such as tumor initiation, epithelial plasticity, organotropic metastasis and drug resistance. With insights into how integrins contribute to the stem-like functions, we now gain better understanding of the integrin signalosome, which will greatly assist novel therapeutic development and more precise clinical decisions.

Cyr61 from adipose-derived stem cells promotes colorectal cancer metastasis and vasculogenic mimicry formation via integrin αV β5

Adipose‐derived stem cells (ADSCs) play a vital role in colorectal cancer (CRC) progression, but the mechanism remains largely unknown. Herein, we found that ADSCs isolated from CRC patients produced more cysteine‐rich 61 (Cyr61) than those from healthy donors, and the elevated serum Cyr61 levels were associated with advanced TNM stages. Moreover, serum Cyr61 displayed a better diagnostic value for CRC compared to carcinoembryonic antigen (CEA) and carbohydrate antigen (CA19‐9). Mechanistically, integrin α_Vβ₅ was identified as the functional receptor by which Cyr61 promotes CRC cell metastasis in vitro and in vivo by activating the α_Vβ₅/FAK/NF‐κB signaling pathway. In addition, Cyr61 promotes vasculogenic mimicry (VM) formation, thereby promoting tumor growth and metastasis through a α_Vβ₅/FAK/HIF‐1α/STAT3/MMP2 signaling cascade. Histologically, xenografts and clinical samples of CRC both exhibited VM, which was correlated with HIF‐1α and MMP2 activation. Notably, we demonstrated the synergistic effect of combined anti‐VM therapy (integrin α_Vβ₅ inhibitor) and anti‐VEGF therapy (bevacizumab) in patient‐derived xenograft models. Further investigation showed that CRC cell‐derived exosomal STAT3 promoted Cyr61 transcription in ADSCs. These findings indicate that Cyr61 derived from ADSCs plays a critical role in promoting CRC progression via integrin α_Vβ₅ and provides a novel antitumor strategy by targeting Cyr61/α_Vβ₅.

Primary tumor and metastasis-sectioning the different steps of the metastatic cascade

Patients with lung cancer in the majority die of metastases. Treatment options include surgery, chemo- and radiotherapy, targeted therapy by tyrosine kinase inhibitors (TKIs), and immuno-oncologic treatment. Despite the success with these treatment options, cure of lung cancer is achieved in only a very small proportion of patients. In most patients’ recurrence and metastasis will occur, and finally kill the patient. Metastasis is a multistep procedure. It requires a change in adhesion of tumor cells for detachment from their neighboring cells. The next step is migration either as single cells [epithelial-mesenchymal transition (EMT)], or as cell clusters (hybrid-EMT or bulk migration). A combination of genetic changes is required to facilitate migration. Then tumor cells have to orient themselves along matrix proteins, detect oxygen concentrations, prevent attacks by immune cells, and induce a tumor-friendly switch of stroma cells (macrophages, myofibroblasts, etc.). Having entered the blood stream tumor cells need to adapt to shear stress, avoid being trapped by coagulation, but also use coagulation in small veins for adherence to endothelia, and express homing molecules for extravasation. Within a metastatic site, tumor cells need a well-prepared niche to establish a metastatic focus. Tumor cells again have to establish a vascular net for maintaining nutrition and oxygen supply, communicate with stroma cells, grow out and set further metastases. In this review the different steps will be discussed with a focus on pulmonary carcinomas. The vast amount of research manuscripts published so far are not easy to analyze: in most reports’ single steps of the metastatic cascade are interpreted as evidence for the whole process; for example, migration is interpreted as evidence for metastasis. In lung cancer most often latency periods are shorter, in between 1–5 years. In other cases, despite widespread migration occurs, tumor cells die within the circulation and do not reach a metastatic site. Therefore, migration is a requisite, but does not necessarily predict metastasis. The intention of this review is to point to these different aspects and hopefully provoke research directed into a more functional analysis of the metastatic process.

Plasminogen regulates mesenchymal stem cell-mediated tissue repair after ischemia through Cyr61 activation

Stem cell transplantation has emerged as a promising strategy in regenerative medicine. However, the poor survival and persistence of the transplanted cells, including mesenchymal stem cells (MSCs), in the hostile ischemic microenvironments represents a major therapeutic barrier. Here we report that plasminogen (Plg) stimulated MSC functions and promoted MSC survival during tissue repair after ischemia. Genetic Plg ablation abolished MSC survival, migration, and proliferation in mouse ischemic limbs, and abrogated MSC-mediated blood reperfusion, neovascularization, and tissue repair after ischemia, suggesting a critical role for Plg in MSC-mediated tissue repair. Furthermore, multiplex cytokine array analysis identified that Plg cleaved and activated cysteine-rich protein 61 (Cyr61), an ECM-associated growth factor, to stimulate MSC survival and migration. Overexpression with truncated Cyr61 in MSCs rescued blood reperfusion after hind limb ischemia in Plg-deficient mice. Finally, Plg-mediated Cyr61 cleavage promoted endothelial cell migration and neovascularization in vitro and in vivo. Our study reveals that Plg promotes MSC survival, persistence, and paracrine effects and improves postischemic neovascularization and tissue repair through Cyr61 cleavage and activation. Thus, targeting Plg/Cyr61 may offer exciting therapeutic opportunities for strengthening MSC therapy in ischemic diseases.

Plasminogen promotes mesenchymal stem cell function and improves post-ischemic neovascularization and tissue repair through cysteine-rich protein 61 activation.

Irradiation Induces Epithelial Cell Unjamming

The healthy and mature epithelial layer is ordinarily quiescent, non-migratory, solid-like, and jammed. However, in a variety of circumstances the layer transitions to a phase that is dynamic, migratory, fluid-like and unjammed. This has been demonstrated in the developing embryo, the developing avian airway, the epithelial layer reconstituted in vitro from asthmatic donors, wounding, and exposure to mechanical stress. Here we examine the extent to which ionizing radiation might similarly provoke epithelial layer unjamming. We exposed primary human bronchial epithelial (HBE) cells maintained in air-liquid interface (ALI) to sub-therapeutic doses (1 Gy) of ionizing radiation (IR). We first assessed: (1) DNA damage by measuring p-H2AX, (2) the integrity of the epithelial layer by measuring transepithelial electrical resistance (TEER), and (3) the extent of epithelial cell differentiation by detecting markers of differentiated airway epithelial cells. As expected, IR exposure induced DNA damage but, surprisingly, disrupted neither normal differentiation nor the integrity of the epithelial cell layer. We then measured cell shape and cellular migration to determine the extent of the unjamming transition (UJT). IR caused cell shape elongation and increased cellular motility, both of which are hallmarks of the UJT as previously confirmed. To understand the mechanism of IR-induced UJT, we inhibited TGF-β receptor activity, and found that migratory responses were attenuated. Together, these observations show that IR can provoke epithelial layer unjamming in a TGF-β receptor-dependent manner.

Inhibition of CYR61-S100A4 Axis Limits Breast Cancer Invasion

Background and Objective: Matricellular proteins modulate the micro environment of tumors and are recognized to contribute to tumor cell invasion and dissemination. The cysteine-rich angiogenic inducer 61 (CYR61) is upregulated in mesenchymal transformed and invasive breast cancer cells. CYR61 correlates with poor prognosis of breast cancer patients. The signaling mechanism that causes invasive properties of cancer cells regarding to epithelial-mesenchymal transition (EMT) needs further research. In this study, we investigated the signaling mechanism, which is responsible for reduced cell invasion after suppression of CYR61 in mesenchymal transformed breast cancer cells and in triple negative breast cancer cells. Methods: We addressed this issue by generating a mesenchymal transformed breast cancer cell line using prolonged mammosphere cultivation. Western blotting and quantitative PCR were used to analyze gene expression alterations. Transient gene silencing was conducted using RNA interference. Proliferation was assessed using AlamarBlue assay. Invasiveness was analyzed using 2D and 3D invasion assays. Immune-histochemical analysis of patient tissue samples was performed to examine the prognostic value of CYR61 expression. Results: In this study, we investigated whether CYR61 could be used as therapeutic target and prognostic marker for invasive breast cancer. We discovered an interaction of CYR61 with metastasis-associated protein S100A4. Suppression of CYR61 by RNA interference reduced the expression of S100A4 dependent on ERK1/2 activity regulation. Non-invasive breast cancer cells became invasive due to extracellular CYR61 supplement. Immune-histochemical analysis of 239 patient tissue samples revealed a correlation of higher CYR61 and S100A4 expression with invasive breast cancer and metastasis. Conclusion: Our data suggest that suppression of CYR61 impedes the formation of an invasive cancer cell phenotype by reducing ERK1/2 phosphorylation thereby suppressing S100A4. These findings identify mechanisms by which CYR61 suppresses cell invasion and suggest it to be a potential therapeutic target and prognostic marker for invasive breast cancer and metastasis.

Are Integrins Still Practicable Targets for Anti-Cancer Therapy?

Correlative clinical evidence and experimental observations indicate that integrin adhesion receptors, in particular those of the αV family, are relevant to cancer cell features, including proliferation, survival, migration, invasion, and metastasis. In addition, integrins promote events in the tumor microenvironment that are critical for tumor progression and metastasis, including tumor angiogenesis, matrix remodeling, and the recruitment of immune and inflammatory cells. In spite of compelling preclinical results demonstrating that the inhibition of integrin αVβ3/αVβ5 and α5β1 has therapeutic potential, clinical trials with integrin inhibitors targeting those integrins have repeatedly failed to demonstrate therapeutic benefits in cancer patients. Here, we review emerging integrin functions and their proposed contribution to tumor progression, discuss preclinical evidence of therapeutic significance, revisit clinical trial results, and consider alternative approaches for their therapeutic targeting in oncology, including targeting integrins in the other cells of the tumor microenvironment, e.g., cancer-associated fibroblasts and immune/inflammatory cells. We conclude that integrins remain a valid target for cancer therapy; however, agents with better pharmacological properties, alternative models for their preclinical evaluation, and innovative combination strategies for clinical testing (e.g., together with immuno-oncology agents) are needed.

Downregulation of miR-142-5p promotes tumor metastasis through directly regulating CYR61 expression in gastric cancer

BACKGROUND

Recurrence is a primary cause of gastric cancer (GC)-related deaths. We reported previously that low expression of miR-142-5p could predict recurrence in GC. The present study aimed to investigate the function and mechanism of miR-142-5p in metastasis of GC.

METHODS

MiR-142-5p expression was detected in 101 GC samples by qRT-PCR. Its clinical significance was statistically analyzed. The roles of miR-142-5p and its candidate target gene CYR61 in metastasis were determined both in vivo and in vitro.

RESULTS

MiR-142-5p downregulation was significantly associated with the recurrence (P = 0.031) and poor prognosis of GC (P = 0.043). MiR-142-5p inhibited cancer cell migration and invasion both in vitro and in vivo. CYR61 was identified as a novel direct target of miR-142-5p by bioinformatics analysis of target prediction and luciferase reporter assay. The re-expression and knockdown of CYR61 could, respectively, rescue the effects induced by miR-142-5p overexpression and knockdown. MiR-142-5p attenuated GC cell migration and invasion, at least partially, by inactivation of the canonical Wnt/β-catenin signaling pathway through CYR61.

CONCLUSIONS

The newly identified miR-142-5p-CYR61-Wnt/β-catenin axis partially illustrates the molecular mechanism of GC recurrence and represents a novel prognosis biomarker for GC.

Type I interferon/IRF7 axis instigates chemotherapy-induced immunological dormancy in breast cancer

Neoadjuvant and adjuvant chemotherapies provide survival benefits to breast cancer patients, in particular in estrogen receptor negative (ER^-) cancers, by reducing rates of recurrences. It is assumed that the benefits of (neo)adjuvant chemotherapy are due to the killing of disseminated, residual cancer cells, however, there is no formal evidence for it. Here, we provide experimental evidence that ER^- breast cancer cells that survived high-dose Doxorubicin and Methotrexate based chemotherapies elicit a state of immunological dormancy. Hallmark of this dormant phenotype is the sustained activation of the IRF7/IFN-β/IFNAR axis subsisting beyond chemotherapy treatment. Upregulation of IRF7 in treated cancer cells promoted resistance to chemotherapy, reduced cell growth and induced switching of the response from a myeloid derived suppressor cell-dominated immune response to a CD4⁺/CD8⁺ T cell-dependent anti-tumor response. IRF7 silencing in tumor cells or systemic blocking of IFNAR reversed the state of dormancy, while spontaneous escape from dormancy was associated with loss of IFN-β production. Presence of IFN-β in the circulation of ER^- breast cancer patients treated with neoadjuvant Epirubicin chemotherapy correlated with a significantly longer distant metastasis-free survival. These findings establish chemotherapy-induced immunological dormancy in ER^- breast cancer as a novel concept for (neo)adjuvant chemotherapy activity, and implicate sustained activation of the IRF7/IFN-β/IFNAR pathway in this effect. Further, IFN-β emerges as a potential predictive biomarker and therapeutic molecule to improve outcome of ER^- breast cancer patients treated with (neo)adjuvant chemotherapy.

[99mTc][Tc(N)PNP43]-Labeled RGD Peptides As New Probes for a Selective Detection of αvβ3 Integrin: Synthesis, Structure-Activity and Pharmacokinetic Studies

New integrin-selective molecules suitable for therapeutic or imaging purposes are currently of interest in development of effective personalized medical platforms. RGDechi is a bifunctional peptide selective for integrin α_vβ₃. Herein, RGDechi and three truncated derivatives functionalized with a cysteine (1-4) were synthesized and labeled with the [^99mTc][Tc(N)PNP43]-synthon ([PNP43 = (CH₃)₂P(CH₂)₂N(C₂H₄OCH₃)(CH₂)₂P(CH₃)₂]) (^99mTc1-4) as a basis for selective integrin recognition. The pharmacological parameters of all radiolabeled peptides were assessed along with the pharmacokinetic profiles of the most promising ^99mTc1 and ^99mTc2 compounds both on healthy and melanoma-bearing mice. Their metabolism and metabolite identification are also reported. ^99mTc1-2 are able to discriminate between endogenously expressed integrins α_vβ₃ and α_vβ₅ and possess favorable pharmacokinetics characterized by low liver uptake and rapid elimination from nontarget tissues resulting in positive target-to-nontarget ratios. Results are encouraging; the presented construct can be considered the starting point for the development of agents for the selective detection of α_vβ₃ expression by SPECT.

Effects of radiation on the metastatic process

Radiotherapy remains one of the corner stones in the treatment of various malignancies and often leads to an improvement in overall survival. Nonetheless, pre-clinical evidence indicates that radiation can entail pro-metastatic effects via multiple pathways. Via direct actions on cancer cells and indirect actions on the tumor microenvironment, radiation has the potential to enhance epithelial-to-mesenchymal transition, invasion, migration, angiogenesis and metastasis. However, the data remains ambiguous and clinical observations that unequivocally prove these findings are lacking. In this review we discuss the pre-clinical and clinical data on the local and systemic effect of irradiation on the metastatic process with an emphasis on the molecular pathways involved.

The matricellular protein CYR61 promotes breast cancer lung metastasis by facilitating tumor cell extravasation and suppressing anoikis

Matricellular proteins play multiple roles in primary tumor growth, local invasion and tumor angiogenesis. However, their contribution to metastasis and the putative mechanisms involved are less well characterized. In ER-negative human breast cancer, elevated expression levels of the matricellular protein Cysteine-rich angiogenic inducer 61 (CYR61) are associated with more aggressive progression. Here, we investigated the role of CYR61 in breast cancer lung metastasis using the triple negative human breast cancer cell lines MDA-MB-231 and SUM159. Silencing of CYR61 significantly decreased lung metastasis from tumors orthotopically implanted in pre-irradiated or naive mammary tissue and upon tail vein injection. Constitutive CYR61 silencing impaired cancer cell extravasation to the lung during the first 24 hours after tail vein injection. In contrast, CYR61 inducible silencing starting 24 hours after cancer cell injection had no impact on lung metastasis formation. In vitro experiments revealed that CYR61 silencing decreased cancer cell transendothelial migration and motility, reduced CYR61 levels present at the cell surface and sensitized cancer cells to anoikis. Furthermore, we demonstrate that CYR61-dependent cell survival under non-adhesive conditions relied, at least partially, on β1 integrin ligation and AMPKα signaling while it was independent of AKT, FAK and ERK1/2 activation. Our data provide the first evidence that CYR61 promotes breast cancer lung metastasis by facilitating tumor cell extravasation and protecting from anoikis during initial seeding to the lung. The uncovered CYR61-β1 integrin-AMPKα axis may serve as a potential therapeutic target to prevent breast cancer metastasis to the lung.

Targeting αvβ3 and αvβ5 integrins inhibits pulmonary metastasis in an intratibial xenograft osteosarcoma mouse model

Osteosarcoma is an aggressive bone cancer that has a high propensity for metastasis to the lungs. Patients with metastatic disease face a very poor prognosis. Therefore, novel therapeutics, efficiently suppressing the metastatic process, are urgently needed. Integrins play a pivotal role in tumor cell adhesion, motility and metastasis. Here, we evaluated αvβ3 and αvβ5 integrin inhibition with cilengitide as a novel metastasis-suppressive therapeutic approach in osteosarcoma. Immunohistochemical analysis of αvβ3 and αvβ5 integrins expression in a tissue microarray of tumor specimens collected from osteosarcoma patients revealed that αvβ5 integrin is mainly found on tumor cells, whereas αvβ3 is predominantly expressed by stromal cells. In vitro functional assays demonstrated that cilengitide dose-dependently inhibited de novo adhesion, provoked detachment and inhibited migration of osteosarcoma cell lines. Cilengitide induced a decline in cell viability, blocked the cell cycle in the G1 phase and caused anoikis by activation of the Hippo pathway. In a xenograft orthotopic mouse model cilengitide minimally affected intratibial primary tumor growth but, importantly, suppressed pulmonary metastasis. The data demonstrate that targeting αvβ3 and αvβ5 integrins in osteosarcoma should be considered as a novel therapeutic option for patients with metastatic disease.

cRGD peptide installation on cisplatin-loaded nanomedicines enhances efficacy against locally advanced head and neck squamous cell carcinoma bearing cancer stem-like cells

Recalcitrant head and neck squamous cell carcinoma (HNSCC) usually relapses after therapy due to the enrichment of drug resistant cancer stem-like cells (CSCs). Nanomedicines have shown potential for eradicating both cancer cells and CSCs by effective intratumoral navigation for reaching particular cell populations and controlling drug delivery. The installation of ligands on nanomedicines is an attractive approach for improving the delivery to CSCs within tumors, though the development of CSC-selective ligand-receptor systems has been challenging. Herein, we found that the CSC subpopulation in HNSCC cells overexpresses α_vβ₅ integrins, which is preferentially expressed in tumor neovasculature and cancer cells, and can be effectively targeted by using cyclic Arg-Gly-Asp (cRGD) peptide. Thus, in this study, we propose installing cRGD peptide on micellar nanomedicines incorporating cisplatin for improving their activity against CSCs and enhancing survival. Both cisplatin-loaded micelles (CDDP/m) and cRGD-installed CDDP/m (cRGD-CDDP/m) were effective against HNSCC SAS-L1-Luc cells in vitro, though cRGD-installed CDDP/m was more potent than CDDP/m against the CSC fraction. In vivo, the cRGD-CDDP/m also showed significant antitumor activity against HNSCC orthotopic tumors, i.e. SAS-L1 and HSC-2. Moreover, cRGD-CDDP/m rapidly accumulated into the lymph node metastasis of SAS-L1 tumors, effectively inhibiting their growth, and prolonging mice survival. These findings indicate cRGD-installed nanomedicines as an advantageous strategy for targeting CSCs in HNSCC, and particularly, cRGD-CDDP/m as a significant therapeutic strategy against regionally advanced HNSCC.

A phase I study of cilengitide and paclitaxel in patients with advanced solid tumors

PURPOSE

Cilengitide is a potent and selective inhibitor of the integrins αvβ3 and αvβ5. The primary objective of this phase I clinical trial was to establish the maximum tolerated dose and determine safety/tolerability of cilengitide in combination with paclitaxel in patients with advanced solid tumors. Secondary objectives included the evaluation of the preliminary clinical outcomes.

PATIENTS AND METHODS

Patients with advanced solid tumors experiencing disease progression on standard treatment were assigned to two different dose levels of cilengitide (2000 mg intravenously once or twice weekly) in combination with fixed-dose, weekly paclitaxel (90 mg/m² intravenously).

RESULTS

Twelve evaluable patients were treated per protocol. A single dose limiting toxicity (DLT) of grade 4 neutropenia was observed at the starting dose level of once weekly cilengitide. There were no grade ≥3 adverse events that occurred with >10% frequency. One patient achieved a partial response to therapy. Five patients experienced stable disease as best response, 3 of which discontinued study participation due to progressive, peripheral neuropathy.

CONCLUSIONS

Cilengitide in combination with paclitaxel was well tolerated. Antitumor activity was observed. The recommended phase II dose is twice weekly cilengitide (2000 mg) with weekly paclitaxel (90 mg/m²). Further studies evaluating drugs that target this pathway are warranted.

Progression and metastasis of lung cancer

Metastasis in lung cancer is a multifaceted process. In this review, we will dissect the process in several isolated steps such as angiogenesis, hypoxia, circulation, and establishment of a metastatic focus. In reality, several of these processes overlap and occur even simultaneously, but such a presentation would be unreadable. Metastasis requires cell migration toward higher oxygen tension, which is based on changing the structure of the cell (epithelial-mesenchymal transition), orientation within the stroma and stroma interaction, and communication with the immune system to avoid attack. Once in the blood stream, cells have to survive trapping by the coagulation system, to survive shear stress in small blood vessels, and to find the right location for extravasation. Once outside in the metastatic locus, tumor cells have to learn the communication with the “foreign” stroma cells to establish vascular supply and again express molecules, which induce immune tolerance.

Differential expression of CCN family members CYR611, CTGF and NOV in gastric cancer and their association with disease progression

CCN is an acronym for cysteine-rich protein 61 (CYR61), connective tissue growth factor (CTGF) and nephroblastoma overexpressed (NOV). Aberrations of certain CCN members including CYR61, CTGF, Wnt1-inducible signalling pathway protein (WISP)-1 and -3 have been reported in gastric cancer. The present study aimed to examine the clinical relevance of NOV along with CYR61 and CTGF in gastric cancer by analysing their transcript levels. CYR61, CTGF and NOV transcript expression in 324 gastric cancer samples with paired adjacent normal gastric tissues were determined using real-time quantitative PCR and the results were statistically analysed against patient clinicopathological data using SPSS software. NOV mRNA levels in gastric cancer tissues were significantly elevated when compared with levels in their paired adjacent non-cancerous tissues. Local advanced tumours with invasive expansion (T3 and T4) expressed higher levels of NOV (p=0.013) compared with the less invasive tumours (T1 and T2). CYR61 transcript levels were also significantly increased in gastric cancers compared with levels in the adjacent non-cancerous tissues. Kaplan-Meier survival curves revealed that patients with CYR61-low transcript levels had longer overall survival (OS) (p=0.018) and disease-free survival (DFS) (p=0.015). NOV overexpression promoted the in vitro proliferation of AGS cells while the knockdown resulted in a reduced proliferation of HGC27 cells. A similar effect was observed for the invasion of these two gastric cancer cell lines. NOV expression was increased in gastric cancer which was associated with local invasion and distant metastases. Taken together, the expression of NOV and CYR61 was increased in gastric cancer. The elevated expression of CYR61 was associated with poorer survival. NOV promoted proliferation and invasion of gastric cancer cells. Further investigations may highlight their predictive and therapeutic potential in gastric cancer.

Dequalinium blocks macrophage-induced metastasis following local radiation

A major therapeutic obstacle in clinical oncology is intrinsic or acquired resistance to therapy, leading to subsequent relapse. We have previously shown that systemic administration of different cytotoxic drugs can induce a host response that contributes to tumor angiogenesis, regrowth and metastasis. Here we characterize the host response to a single dose of local radiation, and its contribution to tumor progression and metastasis. We show that plasma from locally irradiated mice increases the migratory and invasive properties of colon carcinoma cells. Furthermore, locally irradiated mice intravenously injected with CT26 colon carcinoma cells succumb to pulmonary metastasis earlier than their respective controls. Consequently, orthotopically implanted SW480 human colon carcinoma cells in mice that underwent radiation, exhibited increased metastasis to the lungs and liver compared to their control tumors. The irradiated tumors exhibited an increase in the colonization of macrophages compared to their respective controls; and macrophage depletion in irradiated tumor-bearing mice reduces the number of metastatic lesions. Finally, the anti-tumor agent, dequalinium-14, in addition to its anti-tumor effect, reduces macrophage motility, inhibits macrophage infiltration of irradiated tumors and reduces the extent of metastasis in locally irradiated mice. Overall, this study demonstrates the adverse effects of local radiation on the host that result in macrophage-induced metastasis.

Radiation-induced lung damage promotes breast cancer lung-metastasis through CXCR4 signaling

Radiotherapy is a mainstay in the postoperative treatment of breast cancer as it reduces the risks of local recurrence and mortality after both conservative surgery and mastectomy. Despite recent efforts to decrease irradiation volumes through accelerated partial irradiation techniques, late cardiac and pulmonary toxicity still occurs after breast irradiation. The importance of this pulmonary injury towards lung metastasis is unclear. Preirradiation of lung epithelial cells induces DNA damage, p53 activation and a secretome enriched in the chemokines SDF-1/CXCL12 and MIF. Irradiated lung epithelial cells stimulate adhesion, spreading, growth, and (transendothelial) migration of human MDA-MB-231 and murine 4T1 breast cancer cells. These metastasis-associated cellular activities were largely mimicked by recombinant CXCL12 and MIF. Moreover, an allosteric inhibitor of the CXCR4 receptor prevented the metastasis-associated cellular activities stimulated by the secretome of irradiated lung epithelial cells. Furthermore, partial (10%) irradiation of the right lung significantly stimulated breast cancer lung-specific metastasis in the syngeneic, orthotopic 4T1 breast cancer model.

Our results warrant further investigation of the potential pro-metastatic effects of radiation and indicate the need to develop efficient drugs that will be successful in combination with radiotherapy to prevent therapy-induced spread of cancer cells.

The matricellular protein CCN1 enhances TGF-β1/SMAD3-dependent profibrotic signaling in fibroblasts and contributes to fibrogenic responses to lung injury

Matricellular proteins mediate pleiotropic effects during tissue injury and repair. CCN1 is a matricellular protein that has been implicated in angiogenesis, inflammation, and wound repair. In this study, we identified CCN1 as a gene that is differentially up-regulated in alveolar mesenchymal cells of human subjects with rapidly progressive idiopathic pulmonary fibrosis (IPF). Elevated levels of CCN1 mRNA were confirmed in lung tissues of IPF subjects undergoing lung transplantation, and CCN1 protein was predominantly localized to fibroblastic foci. CCN1 expression in ex vivo IPF lung fibroblasts correlated with gene expression of the extracellular matrix proteins, collagen (Col)1a1, Col1a2, and fibronectin as well as the myofibroblast marker, α-smooth muscle actin. RNA interference (RNAi)-mediated knockdown of CCN1 down-regulated the constitutive expression of these profibrotic genes in IPF fibroblasts. TGF-β1, a known mediator of tissue fibrogenesis, induces gene and protein expression of CCN1 via a mothers against decapentaplegic homolog 3 (SMAD3)-dependent mechanism. Importantly, endogenous CCN1 potentiates TGF-β1-induced SMAD3 activation and induction of profibrotic genes, supporting a positive feedback loop leading to myofibroblast activation. In vivo RNAi-mediated silencing of CCN1 attenuates fibrogenic responses to bleomycin-induced lung injury. These studies support previously unrecognized, cooperative interaction between the CCN1 matricellular protein and canonical TGF-β1/SMAD3 signaling that promotes lung fibrosis.-Kurundkar, A. R., Kurundkar, D., Rangarajan, S., Locy, M. L., Zhou, Y., Liu, R.-M., Zmijewski, J., Thannickal, V. J. The matricellular protein CCN1 enhances TGF-β1/SMAD3-dependent profibrotic signaling in fibroblasts and contributes to fibrogenic responses to lung injury.

Cyr61/CCN1 overexpression induces epithelial-mesenchymal transition leading to laryngeal tumor invasion and metastasis and poor prognosis

BACKGROUND

To examine the expression of cysteine-rich 61 (Cyr61/CCN1) protein in laryngeal squamous- cell carcinoma (LSCC) tissues, and its relationship with the tumor epithelial-mesenchymal transition (EMT), invasion, metastasis, and prognosis.

MATERIALS AND METHODS

Immunohistochemistry was used to detect the expressions of Cyr61, Vimentin (Vim), and E-cadherin (E-cad) in 88 cases of LSCC tissues and 30 cases of tumor-adjacent normal tissues. Vim and E-cad were used as mesenchymal and epithelial markers, respectively, to determine the relationship between Cyr61 expression and the EMT of LSCC cells. In addition, clinical and histopathological data were combined to analyze the relationship between the positive-expression rates of Cyr61, Vim and E-cad and LSCC invasion, metastasis and prognosis.

RESULTS

In LSCC tissues, Vim expression rate was significantly higher than that of the tumor-adjacent tissues, whereas E-cad expression rate was significantly lower than that of the tumor-adjacent tissues. The Vim expression rate was significantly higher in stages T3 and T4 than in stages T1 and T2 LSCC tissues, whereas E-cad expression rate was significantly lower in stages T3 and T4 than in stages T1 and T2 LSCC tissues. Compared to the group without lymph node metastasis, the Vim expression rate was significantly higher and the E-cad expression rate was significantly lower in the group with lymph node metastasis. The expression rate of Cyr61 was significantly higher in LSCC tissues than in the tumor-adjacent normal tissues. In addition, the Cyr61 expression rate was higher in stages T3 and T4 than in stages T1 and T2 LSCC, and higher in the group with lymph node metastasis than in the group without lymph node metastasis. The Vim expression rate was significantly higher in the Cyr61 positive group than in the Cyr61 negative group, whereas the E-cad expression rate was significantly higher in the Cyr61 negative group than in the Cyr61 positive group. Survival analysis indicated that survival rates of Cyr61 positive, Vim positive and E-cad negative groups were significantly lower than that of Cyr61 negative, Vim negative and E-cad positive groups, respectively.

CONCLUSIONS

Cyr61 expression is closely associated with LSCC invasion and lymph node metastasis. Overexpression of Cyr61 may induce EMT and therefore leads to LSCC invasion and metastasis and poor prognosis. Cyr61 may become a new maker for clinical prediction of LSCC invasion and metastasis and a new target for LSCC treatment.

Tenascin-C: Exploitation and collateral damage in cancer management

Despite an increasing knowledge about the causes of cancer, this disease is difficult to cure and still causes far too high a death rate. Based on advances in our understanding of disease pathogenesis, novel treatment concepts, including targeting the tumor microenvironment, have been developed and are being combined with established treatment regimens such as surgical removal and radiotherapy. Yet it is obvious that we need additional strategies to prevent tumor relapse and metastasis. Given its exceptional high expression in most cancers with low abundance in normal tissues, tenascin-C appears an ideal candidate for tumor treatment. Here, we will summarize the current applications of targeting tenascin-C as a treatment for different tumors, and highlight the potential of this therapeutic approach.

Emerging role of CCN family proteins in tumorigenesis and cancer metastasis (Review)

The CCN family of proteins comprises the members CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6. They share four evolutionarily conserved functional domains, and usually interact with various cytokines to elicit different biological functions including cell proliferation, adhesion, invasion, migration, embryonic development, angiogenesis, wound healing, fibrosis and inflammation through a variety of signalling pathways. In the past two decades, emerging functions for the CCN proteins (CCNs) have been identified in various types of cancer. Perturbed expression of CCNs has been observed in a variety of malignancies. The aberrant expression of certain CCNs is associated with disease progression and poor prognosis. Insight into the detailed mechanisms involved in CCN-mediated regulation may be useful in understanding their roles and functions in tumorigenesis and cancer metastasis. In this review, we briefly introduced the functions of CCNs, especially in cancer.

Prodding the Beast: Assessing the Impact of Treatment-Induced Metastasis

The arsenal of treatments for most cancers fit broadly into the categories of surgery, chemotherapy, radiation, and targeted therapy. All represent proven and successful strategies, yet each can trigger local (tumor) and systemic (host) processes that elicit unwanted, often opposing, influences on cancer growth. Under certain conditions, nearly all cancer treatments can facilitate metastatic spread, often in parallel (and sometimes in clear contrast) with tumor reducing benefits. The paradox of treatment-induced metastasis (TIM) is not new. Supporting preclinical studies span decades, but are often overlooked. With recent evidence of prometastatic effects following treatment with targeted agents blocking the tumor microenvironment, a closer inspection of this literature is warranted. The TIM phenomena may diminish the impact of effective therapies and play a critical role in eventual resistance. Alternatively, it may simply exemplify the gap between animal and human studies, and therefore have little impact for patient disease and treatment. This review will focus on the preclinical model systems used to evaluate TIM and explore the mechanisms that influence overall treatment efficacy. Understanding the role of TIM in established and emerging drug treatment strategies may help provide rationales for future drug combination approaches with antimetastatic agents to improve outcomes and reduce resistance.

GAP-independent functions of DLC1 in metastasis

Metastases are responsible for most cancer-related deaths. One of the hallmarks of metastatic cells is increased motility and migration through extracellular matrixes. These processes rely on specific small GTPases, in particular those of the Rho family. Deleted in liver cancer-1 (DLC1) is a tumor suppressor that bears a RhoGAP activity. This protein is lost in most cancers, allowing malignant cells to proliferate and disseminate in a Rho-dependent manner. However, DLC1 is also a scaffold protein involved in alternative pathways leading to tumor and metastasis suppressor activities. Recently, substantial information has been gathered on these mechanisms and this review is aiming at describing the potential and known alternative GAP-independent mechanisms allowing DLC1 to impair migration, invasion, and metastasis formation.

Mechanism of irradiation-induced mammary cancer metastasis: A role for SAP-dependent Mkl1 signaling

Radiotherapy is a standard treatment after conservative breast cancer surgery. However, cancers relapsing within a previously irradiated area have an increased probability to metastasize. The mechanisms responsible for this aggressiveness remain unclear. Here, we used the clinically relevant 4T1 breast cancer model mimicking aggressive local relapse after radiotherapy to identify differences between tumors grown in untreated versus preirradiated mammary glands. Tumors grown within preirradiated beds were highly enriched in transcripts encoding collagens and other proteins building or modifying the extracellular matrix, such as laminin‐332, tenascins, lysyl oxidases and matrix metalloproteinases. Type I collagen, known to directly contribute to tissue stiffening, and the pro‐metastatic megakaryoblastic leukemia‐1 (Mkl1) target gene tenascin‐C were further investigated. Mammary tissue preirradiation induced Mkl1 nuclear translocation in the tumor cells in vivo, indicating activation of Mkl1 signaling. Transcript profiling of cultured 4T1 cells revealed that the majority of the Mkl1 target genes, including tenascin‐C, required serum response factor (SRF) for their expression. However, application of dynamic strain or matrix stiffness to 4T1 cells converted the predominant SRF/Mkl1 action into SAP domain‐dependent Mkl1 signaling independent of SRF, accompanied by a switch to SAP‐dependent tumor cell migration. 4T1 tumors overexpressing intact Mkl1 became more metastatic within preirradiated beds, while tumors expressing Mkl1 lacking the SAP domain exhibited impaired growth and metastatic spread, and decreased Mkl1 target gene expression. Thus, we identified SAP‐dependent Mkl1 signaling as a previously unrecognized mediator of aggressive progression of mammary tumors locally relapsing after radiotherapy, and provide a novel signaling pathway for therapeutic intervention.

Stroma irradiation results in tumors with increased extracellular matrix deposition.

Irradiation induces Mkl1 nuclear translocation, tumor growth and lung metastases.

Matrix stiffness and cyclic mechanical strain trigger SAP‐dependent Mkl1 signaling.

Strain and irradiation induce SAP‐dependent cell migration and tumor progression.

Radiation‐induced SAP‐dependent Mkl1 action: a new target for breast cancer therapy.

CCN1 induces hepatic ductular reaction through integrin αvβ₅-mediated activation of NF-κB

Liver cholestatic diseases, which stem from diverse etiologies, result in liver toxicity and fibrosis and may progress to cirrhosis and liver failure. We show that CCN1 (also known as CYR61), a matricellular protein that dampens and resolves liver fibrosis, also mediates cholangiocyte proliferation and ductular reaction, which are repair responses to cholestatic injury. In cholangiocytes, CCN1 activated NF-κB through integrin αvβ5/αvβ3, leading to Jag1 expression, JAG1/NOTCH signaling, and cholangiocyte proliferation. CCN1 also induced Jag1 expression in hepatic stellate cells, whereupon they interacted with hepatic progenitor cells to promote their differentiation into cholangiocytes. Administration of CCN1 protein or soluble JAG1 induced cholangiocyte proliferation in mice, which was blocked by inhibitors of NF-κB or NOTCH signaling. Knock-in mice expressing a CCN1 mutant that is unable to bind αvβ5/αvβ3 were impaired in ductular reaction, leading to massive hepatic necrosis and mortality after bile duct ligation (BDL), whereas treatment of these mice with soluble JAG1 rescued ductular reaction and reduced hepatic necrosis and mortality. Blockade of integrin αvβ5/αvβ3, NF-κB, or NOTCH signaling in WT mice also resulted in defective ductular reaction after BDL. These findings demonstrate that CCN1 induces cholangiocyte proliferation and ductular reaction and identify CCN1/αvβ5/NF-κB/JAG1 as a critical axis for biliary injury repair.

MicroRNA-135b regulates ERα, AR and HIF1AN and affects breast and prostate cancer cell growth

MicroRNAs (miRNAs) regulate a wide range of cellular signaling pathways and biological processes in both physiological and pathological states such as cancer. We have previously identified miR-135b as a direct regulator of androgen receptor (AR) protein level in prostate cancer (PCa). We wanted to further explore the relationship of miR-135b to hormonal receptors, particularly estrogen receptor α (ERα). Here we show that miR-135b expression is lower in ERα-positive breast tumors as compared to ERα-negative samples in two independent breast cancer (BCa) patient cohorts (101 and 1302 samples). Additionally, the miR-135b expression is higher in AR-low PCa patient samples (47 samples). We identify ERα as a novel miR-135b target by demonstrating miR-135b binding to the 3'UTR of the ERα and decreased ERα protein and mRNA level upon miR-135b overexpression in BCa cells. MiR-135b reduces proliferation of ERα-positive BCa cells MCF-7 and BT-474 as well as AR-positive PCa cells LNCaP and 22Rv1 when grown in 2D. To identify other genes regulated by miR-135b we performed gene expression studies and found a link to the hypoxia inducible factor 1α (HIF1α) pathway. We show that miR-135b influences the protein level of the inhibitor for hypoxia inducible factor 1α (HIF1AN) and is able to bind to HIF1AN 3'UTR. Our study demonstrates that miR-135b regulates ERα, AR and HIF1AN protein levels through interaction with their 3'UTR regions, and proliferation in ERα-positive BCa and AR-positive PCa cells.

Synergistic signaling of tumor cell invasiveness by hepatocyte growth factor and hypoxia

Hepatocyte growth factor (HGF) signaling promotes tumor invasiveness in renal cell carcinoma (RCC) and other cancers. In clear cell RCC, VHL loss generates pseudohypoxia that exacerbates HGF-driven invasion through β-catenin deregulation. Hypoxia also enhances HGF-driven invasiveness by papillary RCC cells, but in the absence of VHL, loss signaling integration involves three parallel routes: 1) hypoxia-induced reactive oxygen species production and decreased DUSP2 expression, leading to enhanced mitogen-activated protein kinase (MAPK) cascade activation; 2) reactive oxygen species-induced diacylglycerol production by phospholipase Cγ, leading to protein kinase C activation and increased protein phosphatase- 2A activity, thereby suppressing HGF-induced Akt activation; and 3) a profound shift from HGF-enhanced, proliferation- oriented metabolism to autophagy-dependent invasion and suppression of proliferation. This tripartite signaling integration was not unique to RCC or HGF; in RCC cells, invasive synergy induced by the combination of hypoxia and epidermal growth factor occurred through the same mechanism, and in estrogen receptor-positive breast cancer cells, this mechanism was suppressed in the absence of estrogen. These results define the molecular basis of growth factor and hypoxia invasive synergy in VHL-competent papillary RCC cells, illustrate the plasticity of invasive and proliferative tumor cell states, and provide signaling profiles by which they may be predicted.

CXCR4 as biomarker for radioresistant cancer stem cells

PURPOSE

Radioresistance of cancer cells remains a fundamental barrier for maximum efficient radiotherapy. Tumor heterogeneity and the existence of distinct cell subpopulations exhibiting different genotypes and biological behaviors raise difficulties to eradicate all tumorigenic cells. Recent evidence indicates that a distinct population of tumor cells, called cancer stem cells (CSC), is involved in tumor initiation and recurrence and is a putative cause of tumor radioresistance. There is an urgent need to identify the intrinsic molecular mechanisms regulating the generation and maintenance of resistance to radiotherapy, especially within the CSC subset. The chemokine C-X-C motif receptor 4 (CXCR4) has been found to be a prognostic marker in various types of cancer, being involved in chemotaxis, stemness and drug resistance. The interaction of CXCR4 with its ligand, the chemokine C-X-C motif ligand 12 (CXCL12), plays an important role in modulating the tumor microenvironment, angiogenesis and CSC niche. Moreover, the therapeutic inhibition of the CXCR4/CXCL12 signaling pathway is sensitizing the malignant cells to conventional anti-cancer therapy.

CONTENT

Within this review we are summarizing the role of the CXCR4/CXCL12 axis in the modulation of CSC properties, the regulation of the tumor microenvironment in response to irradiation, therapy resistance and tumor relapse.

CONCLUSION

In light of recent findings, the inhibition of the CXCR4/CXCL12 signaling pathway is a promising therapeutic option to refine radiotherapy.

MiR-194 deregulation contributes to colorectal carcinogenesis via targeting AKT2 pathway

Abstract: Recent studies have increasingly linked microRNAs to colorectal cancer (CRC). MiR-194 has been reported deregulated in different tumor types, whereas the function of miR-194 in CRC largely remains unexplored. Here we investigated the biological effects, mechanisms and clinical significance of miR-194. Functional assay revealed that overexpression of miR-194 inhibited CRC cell viability and invasion in vitro and suppressed CRC xenograft tumor growth in vivo. Conversely, block of miR-194 in APC^Min/+ mice promoted tumor growth. Furthermore, miR-194 reduced the expression of AKT2 both in vitro and in vivo. Clinically, the expression of miR-194 gradually decreased from 20 normal colorectal mucosa (N-N) cases through 40 colorectal adenomas (CRA) cases and then to 40 CRC cases, and was negatively correlated with AKT2 and pAKT2 expression. Furthermore, expression of miR-194 in stool samples was gradually decreased from 20 healthy cases, 20 CRA cases, then to 28 CRC cases. Low expression of miR-194 in CRC tissues was associated with large tumor size (P=0.006), lymph node metastasis (P=0.012) and shorter survival (HR =2.349, 95% CI = 1.242 to 4.442; P=0.009). In conclusion, our data indicated that miR-194 acted as a tumor suppressor in the colorectal carcinogenesis via targeting PDK1/AKT2/XIAP pathway, and could be a significant diagnostic and prognostic biomarker for CRC.

Input of microenvironmental regulation on colorectal cancer: Role of the CCN family

Colorectal cancer (CRC) is a major health problem causing significant morbidity and mortality. Previous results from various studies indicate that CRC tumorigenicity encompasses tumor microenvironment, emphasizing the complex interacting network between cancer cells and nearby host cells, which triggers diverse signaling pathways to promote the growth and spread of cancer cells. The CCN family proteins share a uniform modular structure, mediating a variety of physiological functions, including proliferation, apoptosis, migration, adhesion, differentiation, and survival. Furthermore, CCN proteins are also involved in CRC initiation and development. Many studies have shown that CCN members, such as CCN1, CCN2, CCN3, Wnt-induced secreted protein (WISP)-1, WISP-2, and WISP-3, are dysregulated in CRC, which implies potential diagnostic markers or therapeutic targets clinically. In this review, we summarize the research findings on the role of CCN family proteins in CRC initiation, development, and progression, highlighting their potential for diagnosis, prognosis, and therapeutic application.

Cyr61 expression is associated with prognosis in patients with colorectal cancer

Background

Cysteine-rich 61 (Cyr61), a member of the CCN protein family, possesses diverse functionality in cellular processes such as adhesion, migration, proliferation, and survival. Cyr61 can also function as an oncogene or a tumour suppressor, depending on the origin of the cancer. Only a few studies have reported Cyr61 expression in colorectal cancer. In this study, we assessed the Cyr61 expression in 251 colorectal cancers with clinical follow up.

Methods

We examined Cyr61 expression in 6 colorectal cancer cell lines (HT29, Colo205, Lovo, HCT116, SW480, SW620) and 20 sets of paired normal and colorectal cancer tissues by western blot. To validate the association of Cyr61 expression with clinicopathological parameters, we assessed Cyr61 expression using tissue microarray analysis of primary colorectal cancer by immunohistochemical analysis.

Results

We verified that all of the cancer cell lines expressed Cyr61; 2 cell lines (HT29 and Colo205) demonstrated Cyr61 expression to a slight extent, while 4 cell lines (Lovo, HCT116, SW480, SW620) demonstrated greater Cyr61 expression than HT29 and Colo205 cell lines. Among the 20 cases of paired normal and tumour tissues, greater Cyr61 expression was observed in 16 (80%) tumour tissues than in normal tissues. Furthermore, 157 out of 251 cases (62.5%) of colorectal cancer examined in this study displayed strong Cyr61 expression. Cyr61 expression was found to be associated with pN (p = 0.018). Moreover, Cyr61 expression was associated with statistically significant cancer-specific mortality (p = 0.029). The duration of survival was significantly lesser in patients with Cyr61 high expression than in patients with Cyr61 low expression (p = 0.001). These results suggest that Cyr61 expression plays several important roles in carcinogenesis and may also be a good prognostic marker for colorectal cancer.

Conclusions

Our data confirmed that Cyr61 was expressed in colorectal cancers and the expression was correlated with worse prognosis of colorectal cancers.

Radiotherapy and the tumor microenvironment: mutual influence and clinical implications

Ionizing radiation has been employed in targeted cancer treatments for more than a century because of its cytotoxic effects on cancer cells. However, the responsiveness to radiation and the behavior of tumors in vivo may differ dramatically from observed behaviors of isolated cancer cells in vitro. While not fully understood, these discrepancies are due to a complex constellation of extracellular and intercellular factors that are together termed the tumor microenvironment. Radiation may alter or affect the components of the adjacent tumor microenvironment in significant ways, often with consequences for cancer cells beyond the direct effects of the radiation itself. Moreover, different microenvironmental states, whether induced or at baseline, can modulate or even attenuate the effects of radiation, with consequences for therapeutic efficacy. This chapter describes this bidirectional relationship in detail, exploring the role and clinical implications of the tumor microenvironment with respect to therapeutic irradiation.