Semaphorin-3F suppresses the stemness of colorectal cancer cells by inactivating Rac1

Reverse effect of Semaphorin-3F on rituximab resistance in diffuse large B-cell lymphoma via the Hippo pathway

BACKGROUND

Exploring the underlying mechanism of rituximab resistance is critical to improve the outcomes of patients with diffuse large B-cell lymphoma (DLBCL). Here, we tried to identify the effects of the axon guidance factor semaphorin-3F (SEMA3F) on rituximab resistance as well as its therapeutic value in DLBCL.

METHODS

The effects of SEMA3F on the treatment response to rituximab were investigated by gain- or loss-of-function experiments. The role of the Hippo pathway in SEMA3F-mediated activity was explored. A xenograft mouse model generated by SEMA3F knockdown in cells was used to evaluate rituximab sensitivity and combined therapeutic effects. The prognostic value of SEMA3F and TAZ (WW domain-containing transcription regulator protein 1) was examined in the Gene Expression Omnibus (GEO) database and human DLBCL specimens.

RESULTS

We found that loss of SEMA3F was related to a poor prognosis in patients who received rituximab-based immunochemotherapy instead of chemotherapy regimen. Knockdown of SEMA3F significantly repressed the expression of CD20 and reduced the proapoptotic activity and complement-dependent cytotoxicity (CDC) activity induced by rituximab. We further demonstrated that the Hippo pathway was involved in the SEMA3F-mediated regulation of CD20. Knockdown of SEMA3F expression induced the nuclear accumulation of TAZ and inhibited CD20 transcriptional levels via direct binding of the transcription factor TEAD2 and the CD20 promoter. Moreover, in patients with DLBCL, SEMA3F expression was negatively correlated with TAZ, and patients with SEMA3F low TAZ high had a limited benefit from a rituximab-based strategy. Specifically, treatment of DLBCL cells with rituximab and a YAP/TAZ inhibitor showed promising therapeutic effects in vitro and in vivo .

CONCLUSION

Our study thus defined a previously unknown mechanism of SEMA3F-mediated rituximab resistance through TAZ activation in DLBCL and identified potential therapeutic targets in patients.

Emerging roles and mechanisms of semaphorins activity in cancer

Semaphorins are regulatory molecules that are linked to the modulation of several cancer processes, such as angiogenesis, cancer cell invasiveness and metastasis, tumor growth, as well as cancer cell survival. Semaphorin (SEMA) activity depends on the cancer histotypes and their particularities. In broad terms, the effects of SEMAs result from their interaction with specific receptors/co-receptors - Plexins, Neuropilins and Integrins - and the subsequent effects upon the downstream effectors (e.g. PI3K/AKT, MAPK/ERK). The present article serves as an integrative review work, discussing the broad implications of semaphorins in cancer, focusing on cell proliferation/survival, angiogenesis, invasion, metastasis, stemness, and chemo-resistance/response whilst highlighting their heterogeneity as a family. Herein, we emphasized that semaphorins are largely implicated in cancer progression, interacting with the tumor microenvironment components. Whilst some SEMAs (e.g. SEMA3A, SEMA3B) function widely as tumor suppressors, others (e.g. SEMA3C) act as pro-tumor semaphorins. The differences observed in terms of the biological structure of SEMAs and the particularities of each cancer histotypes require that each semaphorin be viewed as a unique entity, and its roles must be researched accordingly. A more in-depth and comprehensive view of the molecular mechanisms that promote and sustain the malignant behavior of cancer cells is of utmost importance.

The versatile roles of testrapanins in cancer from intracellular signaling to cell-cell communication: cell membrane proteins without ligands

The tetraspanins (TSPANs) are a family of four-transmembrane proteins with 33 members in mammals. They are variably expressed on the cell surface, various intracellular organelles and vesicles in nearly all cell types. Different from the majority of cell membrane proteins, TSPANs do not have natural ligands. TSPANs typically organize laterally with other membrane proteins to form tetraspanin-enriched microdomains (TEMs) to influence cell adhesion, migration, invasion, survival and induce downstream signaling. Emerging evidence shows that TSPANs can regulate not only cancer cell growth, metastasis, stemness, drug resistance, but also biogenesis of extracellular vesicles (exosomes and migrasomes), and immunomicroenvironment. This review summarizes recent studies that have shown the versatile function of TSPANs in cancer development and progression, or the molecular mechanism of TSPANs. These findings support the potential of TSPANs as novel therapeutic targets against cancer.

Vagus innervation in the gastrointestinal tumor: Current understanding and challenges

The vagus nerve (VN) is the main parasympathetic nerve of the autonomic nervous system. It is widely distributed in the gastrointestinal tract and maintains gastrointestinal homeostasis with the sympathetic nerve under physiological conditions. The VN communicates with various components of the tumor microenvironment to positively and dynamically affect the progression of gastrointestinal tumors (GITs). The intervention in vagus innervation delays GIT progression. Developments in adeno-associated virus vectors, nanotechnology, and in vivo neurobiological techniques have enabled the creation of precisely regulated "tumor neurotherapies". Furthermore, the combination of neurobiological techniques and single cell sequencing may reveal more insights into VN and GIT. The present review aimed to summarize the mechanisms of communication between the VN and the gastrointestinal TME and to explore the potential and challenges of VN-based tumor neurotherapy in GITs.

Advances in SEMA3F regulation of clinically high-incidence cancers

Cancer has become a leading cause of morbidity and mortality in recent years. Its high prevalence has had a severe impact on society. Researchers have achieved fruitful results in the causative factors, pathogenesis, treatment strategies, and cancer prevention. Semaphorin 3F (SEMA3F), a member of the signaling family, was initially reported in the literature to inhibit the growth, invasion, and metastasis of cancer cells in lung cancer. Later studies showed it has cancer-inhibiting effects in malignant tumors such as breast, colorectal, ovarian, oral squamous cell carcinoma, melanoma, and head and neck squamous carcinoma. In contrast, recent studies have reported that SEMA3F is expressed more in hepatocellular carcinoma than in normal tissue and promotes metastasis of hepatocellular carcinoma. We chose lung, breast, colorectal, and hepatocellular carcinomas with high clinical prevalence to review the roles and molecular mechanisms of SEMA3F in these four carcinomas. We concluded with an outlook on clinical interventions for patients targeting SEMA3F.

Potential Cross Talk between Autism Risk Genes and Neurovascular Molecules: A Pilot Study on Impact of Blood Brain Barrier Integrity

Autism Spectrum Disorder (ASD) is a common pediatric neurobiological disorder with up to 80% of genetic etiologies. Systems biology approaches may make it possible to test novel therapeutic strategies targeting molecular pathways to alleviate ASD symptoms. A clinical database of autism subjects was queried for individuals with a copy number variation (CNV) on microarray, Vineland, and Parent Concern Questionnaire scores. Pathway analyses of genes from pathogenic CNVs yielded 659 genes whose protein-protein interactions and mRNA expression mapped 121 genes with maximal antenatal expression in 12 brain regions. A Research Domain Criteria (RDoC)-derived neural circuits map revealed significant differences in anxiety, motor, and activities of daily living skills scores between altered CNV genes and normal microarrays subjects, involving Positive Valence (reward), Cognition (IQ), and Social Processes. Vascular signaling was identified as a biological process that may influence these neural circuits. Neuroinflammation, microglial activation, iNOS and 3-nitrotyrosine increase in the brain of Semaphorin 3F- Neuropilin 2 (Sema 3F-NRP2) KO, an ASD mouse model, agree with previous reports in the brain of ASD individuals. Signs of platelet deposition, activation, release of serotonin, and albumin leakage in ASD-relevant brain regions suggest possible blood brain barrier (BBB) deficits. Disruption of neurovascular signaling and BBB with neuroinflammation may mediate causative pathophysiology in some ASD subgroups. Although preliminary, these data demonstrate the potential for developing novel therapeutic strategies based on clinically derived data, genomics, cognitive neuroscience, and basic neuroscience methods.

Molecular targets and therapeutics in chemoresistance of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a specific subtype of breast cancer (BC), which shows immunohistochemically negative expression of hormone receptor i.e., Estrogen receptor and Progesterone receptor along with the absence of Human Epidermal Growth Factor Receptor-2 (HER2/neu). In Indian scenario the prevalence of BC is 26.3%, whereas, in West Bengal the cases are of 18.4%. But the rate of TNBC has increased up to 31% and shows 27% of total BC. Conventional chemotherapy is effective only in the initial stages but with progression of the disease the effectivity gets reduced and shown almost no effect in later or advanced stages of TNBC. Thus, TNBC patients frequently develop resistance and metastasis, due to its peculiar triple-negative nature most of the hormonal therapies also fails. Development of chemoresistance may involve various factors, such as, TNBC heterogeneity, cancer stem cells (CSCs), signaling pathway deregulation, DNA repair mechanism, hypoxia, and other molecular factors. To overcome the challenges to treat TNBC various targets and molecules have been exploited including CSCs modulator, drug efflux transporters, hypoxic factors, apoptotic proteins, and regulatory signaling pathways. Moreover, to improve the targets and efficacy of treatments researchers are emphasizing on targeted therapy for TNBC. In this review, an effort has been made to focus on phenotypic and molecular variations in TNBC along with the role of conventional as well as newly identified pathways and strategies to overcome challenge of chemoresistance.

Potential crosstalk between sonic hedgehog-WNT signaling and neurovascular molecules: Implications for blood-brain barrier integrity in autism spectrum disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disease originating from combined genetic and environmental factors. Post-mortem human studies and some animal ASD models have shown brain neuroinflammation, oxidative stress, and changes in blood-brain barrier (BBB) integrity. However, the signaling pathways leading to these inflammatory findings and vascular alterations are currently unclear. The BBB plays a critical role in controlling brain homeostasis and immune response. Its dysfunction can result from developmental genetic abnormalities or neuroinflammatory processes. In this review, we explore the role of the Sonic Hedgehog/Wingless-related integration site (Shh/Wnt) pathways in neurodevelopment, neuroinflammation, and BBB development. The balance between Wnt-β-catenin and Shh pathways controls angiogenesis, barriergenesis, neurodevelopment, central nervous system (CNS) morphogenesis, and neuronal guidance. These interactions are critical to maintain BBB function in the mature CNS to prevent the influx of pathogens and inflammatory cells. Genetic mutations of key components of these pathways have been identified in ASD patients and animal models, which correlate with the severity of ASD symptoms. Disruption of the Shh/Wnt crosstalk may therefore compromise BBB development and function. In turn, impaired Shh signaling and glial activation may cause neuroinflammation that could disrupt the BBB. Elucidating how ASD-related mutations of Shh/Wnt signaling could cause BBB leaks and neuroinflammation will contribute to our understanding of the role of their interactions in ASD pathophysiology. These observations may provide novel targeted therapeutic strategies to prevent or alleviate ASD symptoms while preserving normal developmental processes. Cover Image for this issue: https://doi.org/10.1111/jnc.15081.

Potential crosstalk between sonic hedgehog-WNT signaling and neurovascular molecules: Implications for blood-brain barrier integrity in autism spectrum disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disease originating from combined genetic and environmental factors. Post-mortem human studies and some animal ASD models have shown brain neuroinflammation, oxidative stress, and changes in blood-brain barrier (BBB) integrity. However, the signaling pathways leading to these inflammatory findings and vascular alterations are currently unclear. The BBB plays a critical role in controlling brain homeostasis and immune response. Its dysfunction can result from developmental genetic abnormalities or neuroinflammatory processes. In this review, we explore the role of the Sonic Hedgehog/Wingless-related integration site (Shh/Wnt) pathways in neurodevelopment, neuroinflammation, and BBB development. The balance between Wnt-β-catenin and Shh pathways controls angiogenesis, barriergenesis, neurodevelopment, central nervous system (CNS) morphogenesis, and neuronal guidance. These interactions are critical to maintain BBB function in the mature CNS to prevent the influx of pathogens and inflammatory cells. Genetic mutations of key components of these pathways have been identified in ASD patients and animal models, which correlate with the severity of ASD symptoms. Disruption of the Shh/Wnt crosstalk may therefore compromise BBB development and function. In turn, impaired Shh signaling and glial activation may cause neuroinflammation that could disrupt the BBB. Elucidating how ASD-related mutations of Shh/Wnt signaling could cause BBB leaks and neuroinflammation will contribute to our understanding of the role of their interactions in ASD pathophysiology. These observations may provide novel targeted therapeutic strategies to prevent or alleviate ASD symptoms while preserving normal developmental processes.

MFG-E8 Regulates Vascular Smooth Muscle Cell Migration Through Dose-Dependent Mediation of Actin Polymerization

Background Migration of vascular smooth muscle cells (VSMCs) is the main contributor to neointimal formation. The Arp2/3 (actin-related proteins 2 and 3) complex activates actin polymerization and is involved in lamellipodia formation during VSMC migration. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a glycoprotein expressed in VSMCs. We hypothesized that MFG-E8 regulates VSMC migration through modulation of Arp2/3-mediated actin polymerization. Methods and Results To determine whether MFG-E8 is essential for VSMC migration, a model of neointimal hyperplasia was induced in the common carotid artery of wild-type and MFG-E8 knockout mice, and the extent of neointimal formation was evaluated. Genetic deletion of MFG-E8 in mice attenuated injury-induced neointimal hyperplasia. Cultured VSMCs deficient in MFG-E8 exhibited decreased cell migration. Immunofluorescence and immunoblotting revealed decreased Arp2 but not Arp3 expression in the common carotid arteries and VSMCs deficient in MFG-E8. Exogenous administration of recombinant MFG-E8 biphasically and dose-dependently regulated the cultured VSMCs. At a low concentration, MFG-E8 upregulated Arp2 expression. By contrast, MFG-E8 at a high concentration reduced the Arp2 level and significantly attenuated actin assembly. Arp2 upregulation mediated by low-dose MFG-E8 was abolished by treating cultured VSMCs with β1 integrin function-blocking antibody and Rac1 inhibitors. Moreover, treatment of the artery with a high dose of recombinant MFG-E8 diminished injury-induced neointimal hyperplasia and reduced VSMC migration. Conclusions MFG-E8 plays a critical role in VSMC migration through dose-dependent regulation of Arp2-mediated actin polymerization. These findings suggest that high doses of MFG-E8 may have therapeutic potential for treating vascular occlusive diseases.

Rac1, A Potential Target for Tumor Therapy

RAS-related C3 botulinum toxin substrate 1 (Rac.1) is one of the important members of Rho GTPases. It is well known that Rac1 is a cytoskeleton regulation protein that regulates cell adhesion, morphology, and movement. Rac1 is highly expressed in different types of tumors, which is related to poor prognosis. Studies have shown that Rac1 not only participates in the tumor cell cycle, apoptosis, proliferation, invasion, migration and angiogenesis, but also participates in the regulation of tumor stem cell, thus promoting the occurrence of tumors. Rac1 also plays a key role in anti-tumor therapy and participates in immune escape mediated by the tumor microenvironment. In addition, the good prospects of Rac1 inhibitors in cancer prevention and treatment are exciting. Therefore, Rac1 is considered as a potential target for the prevention and treatment of cancer. The necessity and importance of Rac1 are obvious, but it still needs further study.

Knockdown of Parkinson's disease-related gene ATP13A2 reduces tumorigenesis via blocking autophagic flux in colon cancer

Background

Accumulating evidence shows that Parkinson’s disease is negatively associated with colon cancer risk, indicating that Parkinson’s disease family proteins may be involved in the initiation of colon cancer. Here, we aimed to identify a Parkinson’s disease-related gene involved in colon cancer, elucidate the underlying mechanisms, and test whether it can be used as a target for cancer therapy.

Methods

We first screened colon cancer and normal tissues for differential expression of Parkinson’s disease-associated genes and identified ATP13A2, which encodes cation-transporting ATPase 13A2, as a putative marker for colon cancer. We next correlated ATP13A2 expression with colon cancer prognosis. We performed a series of ATP13A2 knockdown and overexpression studies in vitro to identify the contribution of ATP13A2 in the stemness and invasive capacity of colon cancer cells. Additionally, autophagy flux assay were determined to explore the mechanism of ATP13A2 induced stemness. Finally, we knocked down ATP13A2 in mice using siRNA to determine whether it can be used as target for colon cancer treatment.

Results

Colon cancer patients with high ATP13A2 expression exhibit shorter overall survival than those with low ATP13A2. Functionally, ATP13A2 acts as a novel stimulator of stem-like traits. Furthermore, knockdown of ATP13A2 in HCT116 resulted in decreased levels of cellular autophagy. Additionally, bafilomycin A1, an autophagy inhibitor, reversed the ATP13A2-induced stemness of colon cancer cells. Lastly treatment with ATP13A2 siRNA reduced the volume of colon cancer xenografts in mice.

Conclusions

The PD-associated gene ATP13A2 is involved in colon cancer stemness through regulation of autophagy. Furthermore, ATP13A2 is a novel prognostic biomarker for colon cancer and is a potential target for colon cancer therapy.

The oncogenic role of LncRNA FAM83C-AS1 in colorectal cancer development by epigenetically inhibits SEMA3F via stabilizing EZH2

Inactivation of Semaphorin 3F (SEMA3F) is involved in colorectal cancer development. However, the mechanism by which SEMA3F is regulated remains elusive. Deregulation of lncRNAs have been implicated in multiple human malignancies, including colorectal cancer (CRC). To date, it is still unclear whether and how lncRNA regulates SEMA3F expression and mediates CRC progression. Here we identify the oncogenic role of lncRNA FAM83C antisense RNA 1 (FAM83C-AS1) in CRC. FAM83C-AS1 is upregulated in tumor tissues and cells of CRC, which is negatively correlated with SEMA3F expression. Reciprocally, knockdown of FAM83C-AS1 exhibits inhibitory effects on the malignant transformation of CRC. Moreover, our data uncover that FAM83C-AS1 enhances methylation of SEMA3F promoter H3K27me3 via upregulating methyltransferase enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2). Specifically, FAM83C-AS1 stabilizes EZH2 protein through recruiting the zinc finger RANBP2-type containing 1 (ZRANB1). Both in vitro and in vivo rescue assays exhibit that SEMA3F is dispensable for the tumor-promoting effects of FAM83C-AS1 on CRC progression. Our data thus demonstrate that the epigenetic role of FAM83C-AS1 in suppression of SEMA3F expression through stabilization of EZH2 to drive CRC progression, which may be conducive to discovering novel therapeutic targets for the treatment of CRC.

Evaluation of active Rac1 levels in cancer cells: A case of misleading conclusions from immunofluorescence analysis

A large number of aggressive cancer cell lines display elevated levels of activated Rac1, a small GTPase widely implicated in cytoskeleton reorganization, cell motility, and metastatic dissemination. A commonly accepted methodological approach for detecting Rac1 activation in cancer cells involves the use of a conformation-sensitive antibody that detects the active (GTP-bound) Rac1 without interacting with the GDP-bound inactive form. This antibody has been extensively used in fixed cell immunofluorescence and immunohistochemistry. Taking advantage of prostate and pancreatic cancer cell models known to have high basal Rac1-GTP levels, here we have established that this antibody does not recognize Rac1 but rather detects the intermediate filament protein vimentin. Indeed, Rac1-null PC3 prostate cancer cells or cancer models with low levels of Rac1 activation still show a high signal with the anti-Rac1-GTP antibody, which is lost upon silencing of vimentin expression. Moreover, this antibody was unable to detect activated Rac1 in membrane ruffles induced by epidermal growth factor stimulation. These results have profound implications for the study of this key GTPase in cancer, particularly because a large number of cancer cell lines with characteristic mesenchymal features show simultaneous up-regulation of vimentin and high basal Rac1-GTP levels when measured biochemically. This misleading correlation can lead to assumptions about the validity of this antibody and inaccurate conclusions that may affect the development of appropriate therapeutic approaches for targeting the Rac1 pathway.

Active RAC1 Promotes Tumorigenic Phenotypes and Therapy Resistance in Solid Tumors

Acting as molecular switches, all three members of the Guanosine triphosphate (GTP)-ase-family, Ras-related C3 botulinum toxin substrate (RAC), Rho, and Cdc42 contribute to various processes of oncogenic transformations in several solid tumors. We have reviewed the distribution of patterns regarding the frequency of Ras-related C3 botulinum toxin substrate 1 (RAC1)-alteration(s) and their modes of actions in various cancers. The RAC1 hyperactivation/copy-number gain is one of the frequently observed features in various solid tumors. We argued that RAC1 plays a critical role in the progression of tumors and the development of resistance to various therapeutic modalities applied in the clinic. With this perspective, here we interrogated multiple functions of RAC1 in solid tumors pertaining to the progression of tumors and the development of resistance with a special emphasis on different tumor cell phenotypes, including the inhibition of apoptosis and increase in the proliferation, epithelial-to-mesenchymal transition (EMT), stemness, pro-angiogenic, and metastatic phenotypes. Our review focuses on the role of RAC1 in adult solid-tumors and summarizes the contextual mechanisms of RAC1 involvement in the development of resistance to cancer therapies.

Semaphorin-4C is upregulated in epithelial ovarian cancer

The present retrospective study aimed to investigate the expression of semaphorin-4C (Sema4C) in epithelial ovarian cancer (EOC), and to determine the association between Sema4C expression and patient clinicopathological characteristics. Sema4C mRNA expression was detected by reverse transcription-quantitative polymerase chain reaction in the tissues of 74 cases of EOC, 20 cases of ovarian epithelial benign tumor, 20 cases of ovarian borderline epithelial tumor and 15 cases of normal ovarian tissue. Immunohistochemistry was used to detect the expression and localization of Sema4C. The association between Sema4C expression level and patients clinicopathological characteristics was determined by χ² test. The results demonstrated that Sema4C expression level in ovarian epithelial carcinoma tissues was significantly higher compared with that in benign tumors, borderline epithelial tumors and normal ovarian tissues (P<0.05). In addition, Sema4C expression in ovarian cancer tissues was significantly associated with the clinical and pathological stages of tumors (P<0.05). In conclusion, the present study demonstrated that Sema4C expression was upregulated in EOC.

Changes in Expression Pattern of SEMA3F Depending on Endometrial Cancer Grade - Pilot Study

Background:

In the course of neoplastic diseases, a reduction in SEMA3F expression is observed, which translates into an increase in the proliferative and proangiogenic potential of cells forming the tumor and the surrounding microenvironment.

Objective:

The aim of this study was to determine the changes in SEMA3F level in endometrial cancer depending on its grade.

Methods:

The study material consisted of tissue samples: 15 without neoplastic changes (control group) and 45 with endometrial cancer (G1, 17; G2, 15; G3, 13; study group). SEMA3F expression was assessed using the immune-histochemical method.

Results:

The expression of SEMA3F was observed in the control group (Me = 159.38) and in the study group (G1, Me = 121.32; G2, Me = 0; G3, Me = 130.37). Differences between each grade and control and between individual grades were statistically significant. There were no significant correlations between SEMA3F expression and weight and Body Mass Index (BMI). The reduced SEMA3F expression in tumor tissue compared to healthy tissue indicates that this protein plays key roles in proliferation and angiogenesis.

Conclusion:

We found that depending on the severity of the disease, cancer adopts different survival strategies, where SEMA3F plays an important role. As a molecular marker, SEMA3F is not sensitive to weight and BMI.

TUFT1 Promotes Triple Negative Breast Cancer Metastasis, Stemness, and Chemoresistance by Up-Regulating the Rac1/β-Catenin Pathway

Objectives: Triple negative breast cancer (TNBC) is a subtype of breast cancer with stronger invasion and metastasis, but its specific mechanism of action is still unclear. Tuft1 plays an important regulatory role in the survival of breast cancer cells; however, its role in regulating TNBC metastatic potential has not been well-characterized. Our aim was therefore to systematically study the mechanism of TUFT1 in the metastasis, stemness, and chemoresistance of TNBC and provide new predictors and targets for BC treatment.

Methods: We used western blotting and IHC to measure TUFT1and Rac1-GTP expression levels in both human BC samples and cell lines. A combination of shRNA, migration/invasion assays, sphere formation assay, apoptosis assays, nude mouse xenograft tumor model, and GTP activity assays was used for further mechanistic studies.

Results: We demonstrated that silencing TUFT1 in TNBC cells significantly inhibited cell metastasis and stemness in vitro. A nude mouse xenograft tumor model revealed that TUFT1 knockdown greatly decreased spontaneous lung metastasis of TNBC tumors. Mechanism studies showed that TUFT1 promoted tumor cell metastasis and stemness by up-regulating the Rac1/β-catenin pathway. Moreover, mechanistic studies indicated that the lack of TUFT1 expression in TNBC cells conferred more sensitive to chemotherapy and increased cell apoptosis via down-regulating the Rac1/β-catenin signaling pathway. Further, TUFT1 expression positively correlated with Rac1-GTP in TNBC samples, and co-expression of TUFT1 and Rac1-GTP predicted poor prognosis in TNBC patients who treated with chemotherapy.

Conclusion: Our findings suggest that TUFT1/Rac1/β-catenin pathway may provide a potential target for more effective treatment of TNBC.

TIAM1 promotes chemoresistance and tumor invasiveness in colorectal cancer

Accumulating evidence suggests that cancer cells with stem cell-like features have higher resistance to chemotherapeutic agents. Herein, we identified T-lymphoma invasion and metastasis-inducing protein-1 (TIAM1) as one of the Wnt-signaling associated genes which drives self-renewal and its expression is upregulated by cancer associated fibroblasts (CAFs). TIAM1 expression was assessed in resected colorectal cancer (CRC) tissues from 300 patients who did or did not respond to chemotherapy. siRNA and CRISPR/Cas9 was used to examine whether the inhibition of TIAM1 affects chemosensitivity of CRC. We demonstrate that stemness through Wnt signaling regulates chemosensitivity and this phenomenon occurs exclusively in cancer stem cells. Subsequently, we established patient-derived CAFs and tested whether the drug sensitivity of CRC cell lines is altered with CAF-derived conditioned medium. High-TIAM1 expression correlated significantly with poor prognosis of CRC patients, and was overexpressed in patients who did not respond to chemotherapy. We demonstrated that the inhibition of TIAM1 enhanced sensitivity to chemotherapeutic drugs and reduced tumor invasiveness in a series of experiments in vitro. Moreover, CAF-derived conditioned media increased stemness and chemoresistance in CRC cell lines through TIAM1 overexpression. In addition, we validated TIAM1 associated drug sensitivity using a xenograft model. We have demonstrated that TIAM1 is overexpressed in CRC tumors from patients who did not respond to chemotherapeutic drugs and levels of TIAM1 expression served as an independent prognostic factor. Mechanistically, CAFs enhanced CRC chemoresistance through TIAM1 overexpression. Collectively, these results suggest that TIAM1 regulates chemosensitivity in tumors and stroma and thus may be an attractive therapeutic target.

Semaphorins as Regulators of Phenotypic Plasticity and Functional Reprogramming of Cancer Cells

Semaphorins, initially found as neuronal guidance cues in embryo development, are now appreciated as major regulators of tissue morphogenesis and homeostasis, as well as of cancer progression. In fact, semaphorin signals have a profound impact on cell morphology, which has been commonly associated with the ability to regulate monomeric GTPases, cell-substrate adhesion, and cytoskeletal dynamics. Recently, however, several reports have indicated a novel and additional function of diverse semaphorins in the regulation of gene expression and cell phenotype plasticity. In this review article, we discuss these novel findings, focusing on the role of semaphorin signals in the regulation of bi-directional epithelial-mesenchymal transitions, stem cell properties, and drug resistance, which greatly contribute to the pathogenesis of cancer.

Class-3 Semaphorins and Their Receptors: Potent Multifunctional Modulators of Tumor Progression

Semaphorins are the products of a large gene family containing 28 genes of which 21 are found in vertebrates. Class-3 semaphorins constitute a subfamily of seven vertebrate semaphorins which differ from the other vertebrate semaphorins in that they are the only secreted semaphorins and are distinguished from other semaphorins by the presence of a basic domain at their C termini. Class-3 semaphorins were initially characterized as axon guidance factors, but have subsequently been found to regulate immune responses, angiogenesis, lymphangiogenesis, and a variety of additional physiological and developmental functions. Most class-3 semaphorins transduce their signals by binding to receptors belonging to the neuropilin family which subsequently associate with receptors of the plexin family to form functional class-3 semaphorin receptors. Recent evidence suggests that class-3 semaphorins also fulfill important regulatory roles in multiple forms of cancer. Several class-3 semaphorins function as endogenous inhibitors of tumor angiogenesis. Others were found to inhibit tumor metastasis by inhibition of tumor lymphangiogenesis, by direct effects on the behavior of tumor cells, or by modulation of immune responses. Notably, some semaphorins such as sema3C and sema3E have also been found to potentiate tumor progression using various mechanisms. This review focuses on the roles of the different class-3 semaphorins in tumor progression.

[ARTICLE WITHDRAWN] Long Noncoding RNA TUNAR Represses Growth, Migration, and Invasion of Human Glioma Cells Through Regulating miR-200a and Rac1

THIS ARTICLE WAS WITHDRAWN BY THE PUBLISHERS IN NOVEMBER 2020.

Semaphorin 3F and Netrin-1: The Novel Function as a Regulator of Tumor Microenvironment

Axon guidance molecules play an important role in regulating proper neuronal networking during neuronal development. They also have non-neuronal properties, which include angiogenesis, inflammation, and tumor development. Semaphorin 3F (SEMA3F), a member of the class 3 semaphorins, was initially identified as an axon guidance factor, that repels axons and collapses growth cones. However, SEMA3F has similar effects on endothelial cells (ECs) and tumor cells. In this review, we discuss the novel molecular mechanisms underlying SEMA3F activity in vascular and tumor biology. Recent evidence suggests that SEMA3F functions as a PI3K-Akt-mTOR inhibitor in mammalian cells, including T cells, ECs, and tumor cells. Therefore, SEMA3F may have broad therapeutic implications. We also discuss the key role of axon guidance molecules as regulators of the tumor microenvironment. Netrin-1, a chemoattractant factor in the neuronal system, promotes tumor progression by enhancing angiogenesis and metastasis. Moreover, our recent studies demonstrate that netrin-1/neogenin interactions augment CD4+ T cell chemokinesis and elicit pro-inflammatory responses, suggesting that netrin-1 plays a key role in modulating the function of a tumor and its surrounding cells in the tumor microenvironment. Overall, this review focuses on SEMA3F and netrin-1 signaling mechanisms to understand the diverse biological functions of axon guidance molecules.

RAC1-GTP promotes epithelial-mesenchymal transition and invasion of colorectal cancer by activation of STAT3

Epithelial-mesenchymal transition (EMT) plays a critical role in initiating tumor invasion and metastasis of colorectal cancer (CRC), although the underlying mechanisms remain to be clarified. Herein, we demonstrate that the active form of Rac family small GTPase 1 (RAC1-GTP) is overexpressed in CRCs and promotes the EMT-mediated invasion of CRC cells through activation of the signal transducers and activators of transcription 3 (STAT3) pathway. Increased expression of RAC1-GTP in CRC tissues was positively correlated with the TNM stages of CRCs and indicated poor prognosis of CRC patients. Targeting RAC1-GTP activity by its specific inhibitor NSC23766 markedly suppressed the migration and invasion of CRC cells. Mechanistically, RAC1-GTP directly interacted with STAT3 to promote STAT3 phosphorylation, thus promoted EMT of CRC cells. Enforced expression of constitutively activated STAT3 (STAT3-C) abrogated the suppressive effect of RAC1-GTP disruption on the migration and invasion of CRC cells. Importantly, NSC23766 disrupted EMT in CRC cells and significantly diminished growth of CRC xenografts. Taken together, our data indicate that RAC1-GTP is an important player in EMT-mediated tumor invasion and a potential therapeutic target for CRCs.

RHO GTPases in cancer: known facts, open questions, and therapeutic challenges

RHO GTPases have been traditionally associated with protumorigenic functions. While this paradigm is still valid in many cases, recent data have unexpectedly revealed that RHO proteins can also play tumor suppressor roles. RHO signaling elements can also promote both pro- and antitumorigenic effects using GTPase-independent mechanisms, thus giving an extra layer of complexity to the role of these proteins in cancer. Consistent with these variegated roles, both gain- and loss-of-function mutations in RHO pathway genes have been found in cancer patients. Collectively, these observations challenge long-held functional archetypes for RHO proteins in both normal and cancer cells. In this review, I will summarize these data and discuss new questions arising from them such as the functional and clinical relevance of the mutations found in patients, the mechanistic orchestration of those antagonistic functions in tumors, and the pros and cons that these results represent for the development of RHO-based anticancer drugs.

Class 3 semaphorins modulate the invasive capacity of rheumatoid arthritis fibroblast-like synoviocytes

Objective

Class 3 semaphorins regulate diverse cellular processes relevant to the pathology of RA, including immune modulation, angiogenesis, apoptosis and invasive cell migration. Therefore, we analysed the potential role of class 3 semaphorins in the pathology of RA.

Methods

Protein and mRNA expression in RA synovial tissue, SF and fibroblast-like synoviocytes (FLS) were determined by immunoblotting and quantitative PCR (qPCR). RA FLS migration and invasion were determined using wound closure and transwell invasion assays, respectively. PlexinA1, neuropilin-1 and neuropilin-2 expression was knocked down using small interfering RNA (siRNA). Activation of FLS intracellular signalling pathways was assessed by immunoblotting.

Results

mRNA expression of semaphorins (Sema)3B, Sema3C, Sema3F and Sema3G was significantly lower in the synovial tissue of early arthritis patients at baseline who developed persistent disease compared with patients with self-limiting disease after 2 years follow-up. Sema3B and Sema3F expression was significantly lower in arthritis patients fulfilling classification criteria for RA compared with those who did not. FLS expression of Sema3A was induced after stimulation with TNF, IL-1β or lipopolysaccharides (LPS), while Sema3B and Sema3F expression was downregulated. Exogenously applied Sema3A induced the migration and invasive capacity of FLS, while stimulation with Sema3B or Sema3F reduced spontaneous FLS migration, and platelet-derived growth factor induced cell invasion, effects associated with differential regulation of MMP expression and mediated by the PlexinA1 and neuropilin-1 and -2 receptors.

Conclusion

Our data suggest that modulation of class 3 semaphorin signaling could be a novel therapeutic strategy for modulating the invasive behaviour of FLS in RA.

Capillary morphogenesis gene 2 maintains gastric cancer stem-like cell phenotype by activating a Wnt/β-catenin pathway

A growing body of evidence shows that the development and progression of gastric cancer (GC) is mainly associated to the presence of gastric cancer stem-like cells (GCSLCs). However, it is unclear how GCSLC population is maintained. This study aimed to explore the role of capillary morphogenesis gene 2 (CMG2) in GCSLC maintenance and the relevance to GC progression. We found that CMG2 was highly expressed in GC tissues and the expression levels were associated with the invasion depth and lymph node metastasis of GC, and inversely correlated with the survival of GC patients. Sorted CMG2^High GC cells preferentially clustered in CD44^High stem-like cell population, which expressed high levels of stemness-related genes with increased capabilities of self-renewal and tumorigenicity. Depletion of CMG2 gene resulted in reduction of GCSLC population with attenuated stemness and decrease of invasive and metastatic capabilities with subdued epithelial–mesenchymal transition phenotype in GC cells. Mechanistically, CMG2 interacted with LRP6 in GCSLCs to activate a Wnt/β-catenin pathway. Thus, our results demonstrate that CMG2 promotes GC progression by maintaining GCSLCs and can serve as a new prognostic indicator and a target for human GC therapy.

The crucial role of SEMA3F in suppressing the progression of oral squamous cell carcinoma

Background

Oral squamous cell carcinoma (OSCC) is one of the most common types of malignancy. Semaphorin 3F (SEMA3F) is highly conserved but present at a lower level in various cancers than in healthy tissues. While it has been reported that SEMA3F is involved in cancer cell proliferation, migration and invasion, its function in OSCC remains unknown.

Methods

The expression of SEMA3F in OSCC tissues and OSCC-derived cells was analyzed using qRT-PCR and western blotting. Using SAS and HSC2 cells, we also monitored the effect of SEMA3F on OSCC cell proliferation, migration and invasion using MTT, colony formation and transwell assays. The function of SEMA3F in OSCC tumor formation was also assessed in vivo.

Results

SEMA3F was significantly downregulated in OSCC tissues and OSCC-derived cells. SEMA3F shows growth inhibitory activity in SAS and HSC2 cells and may act as a tumor suppressor. It can inhibit the migration and invasion potential of OSCC cells. Our results also demonstrate that SEMA3F can suppress the growth of OSCC cells in vivo.

Conclusions

This study revealed that SEMA3F plays a role as a tumor suppressor in OSCC cell proliferation, migration and invasion. Our finding provides new insight into the progression of OSCC. Therapeutically, SEMA3F has some potential as a target for OSCC treatment, given sufficient future research.

Phosphorylated mTOR and YAP serve as prognostic markers and therapeutic targets in gliomas

Glioma is the most prevalent type of tumor in the brain and is comprised of grades I-IV, according to the WHO classification system. Grade IV glioma is also known as glioblastoma multiforme (GBM), the most malignant type of glioma. Glioma is characterized by a complex molecular background, and gene profiling studies have disclosed critical genetic events in human gliomas, which make targeted therapies the most promising therapeutic strategy. However, crosstalk between the targeted signaling pathways may hinder the efficacy of targeted therapies in gliomas. Therefore, it is necessary to identify effective markers to stratify patients for specific therapeutic procedures. Although several mechanisms have been proposed based on the crosstalk between PI3K/AKT/mTORC1 and Hippo/YAP pathways, the clinical significance of the two pathways has not yet been assessed in a combinatorial manner. In this study, we evaluated the two pathways in human glioma specimens and observed the positive correlation between protein levels of p-mTORS2448 and YAP in gliomas. The findings indicated that high expression of p-mTORS2448 and YAP correlated with poor overall survival of glioma patients. As p-mTORS2448 is a specific marker of mTORC1 activation, our results reveal a potential interaction between mTORC1 and YAP, which might functionally participate in the development and progression of gliomas. In support of this hypothesis, a combination of inhibitors targeting mTORC1 and YAP showed a better inhibitory effect on growth of glioma cell lines. Altogether, our work, for the first time, reveals that p-mTORS2448 and YAP can be used as markers of PI3K/AKT/mTORC1 and Hippo/YAP pathway activity to predict prognosis and are target candidates for personalized medicine.

Immunohistochemical evalulation of activated Ras and Rac1 as potential downstream effectors of aquaporin-5 in breast cancer in vivo

Aberrant levels of aquaporin-5 (AQP5) expression have been observed in several types of cancer, including breast cancer, where AQP5 overexpression is associated with metastasis and poor prognosis. In cultured cancer cells, AQP5 facilitates cell migration and activates Ras signaling. Both increased cell migration and Ras activation are associated with cancer metastasis, but so far it is unknown if AQP5 also affects these processes in vivo. Therefore, we investigated if high AQP5 expression in breast cancer tissue correlated with increased activation of Ras and of Rac1, which is a GTPase also involved in cell migration. This was accomplished by immunohistochemical analysis of invasive ductal carcinoma of breast tissue sections from human patients, followed by qualitative and quantitative correlation analysis between AQP5 and activated Ras and Rac1. Immunohistochemistry revealed that activation of Ras and Rac1 was positively correlated. There was, however, no correlation between high AQP5 expression and activation of Ras, whereas a nonsignificant, but positive, tendency between the levels of AQP5 and activated Rac1 levels was observed. In summary, this is the first report that correlates AQP5 expression levels to downstream signaling partners in breast cancer tissue sections. The results suggest Rac1 as a potential downstream signaling partner of AQP5 in vivo.

Role of Rac1 Pathway in Epithelial-to-Mesenchymal Transition and Cancer Stem-like Cell Phenotypes in Gastric Adenocarcinoma

Rac1, a Rho GTPase family member, is dysregulated in a variety of tumor types including gastric adenocarcinoma, but little is known about its role in cancer stem-like cells (CSCs). Therefore, Rac1 activity and inhibition were examined in gastric adenocarcinoma cells and mouse xenograft models for epithelial-to-mesenchymal transition (EMT) and CSC phenotypes. Rac1 activity was significantly higher in spheroid-forming or CD44⁺ gastric adenocarcinoma CSCs compared with unselected cells. Rac1 inhibition using Rac1 shRNA or a Rac1 inhibitor (NSC23766) decreased expression of the self-renewal transcription factor, Sox-2, decreased spheroid formation by 78%-81%, and prevented tumor initiation in immunodeficient mice. Gastric adenocarcinoma CSCs had increased expression of the EMT transcription factor Slug, 4.4- to 8.3-fold greater migration, and 4.2- to 12.6-fold greater invasion than unselected cells, and these increases could be blocked completely with Rac1 inhibition. Gastric adenocarcinoma spheroid cells were resistant to 5-fluorouracil and cisplatin chemotherapy, and this chemotherapy resistance could be reversed with Rac1 shRNA or NSC23766. The PI3K/Akt pathway may be upstream of Rac1, and JNK may be downstream of Rac1. In the MKN-45 xenograft model, cisplatin inhibited tumor growth by 50%, Rac1 inhibition by 35%, and the combination by 77%. Higher Rac1 activity, in clinical specimens from gastric adenocarcinoma patients who underwent potentially curative surgery, correlated with significantly worse survival (P = 0.017). In conclusion, Rac1 promotes the EMT program in gastric adenocarcinoma and the acquisition of a CSC state. Rac1 inhibition in gastric adenocarcinoma cells blocks EMT and CSC phenotypes, and thus may prevent metastasis and augment chemotherapy.Implications: In gastric adenocarcinoma, therapeutic targeting of the Rac1 pathway may prevent or reverse EMT and CSC phenotypes that drive tumor progression, metastasis, and chemotherapy resistance. Mol Cancer Res; 15(8); 1106-16. ©2017 AACR.

TTF1-NPs Induce ERS-Mediated Apoptosis and Inhibit Human Hepatoma Cell Growth In Vitro and In Vivo

Previous studies have shown that 5,2',4'-trihydroxy-6,7,5'-trimethoxyflavone (TTF1) is the primary anticancer constituent of the traditional Chinese medicinal plant Sorbaria sorbifolia (SS), which has been applied to treat cancer in China. In this study, we investigated the in vitro and in vivo antitumor effects and biological mechanisms of small-molecule TTF1 nanoparticles (TTF1-NPs). The effects of TTF1-NPs on cell growth and apoptosis were investigated using human hepatoma cells. The molecular changes associated with the effects of TTF1-NPs were analyzed by immunocytochemistry and Western blot analysis. The in vivo effect of TTF1-NPs was investigated using the HepG2 tumor xenograft model. We found that TTF1-NPs exhibited antitumor effects in vitro accompanied by induction of apoptosis in human hepatoma cells. Mechanistically, our data showed that TTF1-NPs induced apoptosis via endoplasmic reticulum stress (ERS) pathway in hepatoma cells. Moreover, inhibition of ERS activation blocked TTF1-NP-induced apoptosis in HepG2 cells. Finally, TTF1-NPs inhibited the growth of HepG2 xenograft tumors. Taken together, our results demonstrated that TTF1-NP-induced apoptosis was mediated at least in part by the ERS pathway and thus inhibited hepatoma tumor growth.

The role of the semaphorins in cancer

The semaphorins were initially characterized as axon guidance factors, but have subsequently been implicated also in the regulation of immune responses, angiogenesis, organ formation, and a variety of additional physiological and developmental functions. The semaphorin family contains more then 20 genes divided into 7 subfamilies, all of which contain the signature sema domain. The semaphorins transduce signals by binding to receptors belonging to the neuropilin or plexin families. Additional receptors which form complexes with these primary semaphorin receptors are also frequently involved in semaphorin signaling. Recent evidence suggests that semaphorins also fulfill important roles in the etiology of multiple forms of cancer. Some semaphorins have been found to function as bona-fide tumor suppressors and to inhibit tumor progression by various mechanisms while other semaphorins function as inducers and promoters of tumor progression.

Distinctive microRNA expression in early stage nasopharyngeal carcinoma patients

The goal of this study was to investigate microRNAs (miRs) expression at different stages of nasopharyngeal carcinoma (NPC). MiR expression profiling at various stages of NPC was performed by miR array and further verified using quantitative real-time RT-PCR. Pathway enrichment analysis was carried out to identify the functional pathways regulated by the miRs. The expression of a selected group of identified miRs was verified in stage I NPC by in situ hybridization (ISH). A total of 449 miRs were identified with significantly different expressions between NPC tissues and normal pharyngeal tissues. Eighty-four miRs were dysregulated only in stage I NPC, among which 45 miRs were up-regulated and the other 39 were down-regulated. Pathway enrichment assay revleaed that three significantly down-regulated and three significantly up-regulated miRs involved in 12 pathways associating with tumour formation and progression. Quantitative RT-PCR confirmed the miR array result. In addition, the low expression levels of hsa-miR-4324, hsa-miR-203a and hsa-miR-199b-5p were further validated in stage I NPC by ISH. This present study identifed the miR signature in stage I NPC, providing the basis for early detection and treatment of NPC.

SEMA3F prevents metastasis of colorectal cancer by PI3K-AKT-dependent down-regulation of the ASCL2-CXCR4 axis

Semaphorin-3F (SEMA3F), an axonal repulsant in nerve development, has been shown to inhibit the progression of human colorectal cancer (CRC); however, the underlying mechanism remains elusive. In this study we found a negative correlation between the levels of SEMA3F and CXCR4 in CRC specimens from 85 patients, confirmed by bioinformatics analysis of gene expression in 229 CRC samples from the Cancer Genome Atlas. SEMA3F(high) /CXCR4(low) patients showed the lowest frequency of lymph node and distant metastasis and the longest survival. Mechanistically, SEMA3F inhibited the invasion and metastasis of CRC cells through PI3K-AKT-dependent down-regulation of the ASCL2-CXCR4 axis. Specifically, ASCL2 enhanced the invasion and metastasis of CRC cells in vitro and expression of ASCL2 correlated with distant metastasis, tumour size and poor overall survival in CRC patients. Treatment of CRC cells with the CXCR4 antagonist AMD3100 attenuated SEMA3F knockdown-induced invasion and metastasis of CRC cells in vitro and in vivo. Our study thus demonstrates that SEMA3F functions as a suppressor of CRC metastasis via down-regulating the ASCL2-CXCR4 axis.