Genomic and phenotypic analysis reveals a key role for CCN1 (CYR61) in BAG3-modulated adhesion and invasion

Corelating the molecular structure of BAG3 to its oncogenic role

BAG3 is a multifaceted protein characterised by having WW domain, PXXP motif and BAG domain. This protein gets upregulated during malignant transformation of cells and has been associated with poorer survival of patients. Procancerous activity of BAG domain of BAG3 is well documented. BAG domain interacts with ATPase domain of Hsp-70 preventing protein delivery to proteasome. This impediment results in enhanced cell survival, proliferation, resistance to apoptosis and chemoresistance. Besides BAG domain other two domains/motifs of BAG3 are under research vigilance to explore its further oncogenic role. This review summarises the role of different structural determinants of BAG3 in elevating oncogenesis. Based on the already existing findings, more interacting partners of BAG3 are anticipated. The anticipated partners of BAG3 can shed a wealth of information into the mechanistic insights of its proproliferative role. Proper insights into the mechanistic details adopted by BAG3 to curtail/elaborate activity of anticipated interacting partners can serve as a potent target for development of therapeutic interventions.

CYR61 promotes colorectal carcinoma progression via activating epithelial-mesenchymal transition

Colorectal carcinoma is the third most common type of cancer. Although the role of matricellular proteins and their association with tumor progression is well documented, limited data are available concerning their involvement in colorectal cancer. The current study investigated the expression pattern of matricellular proteins SPARC and CYR61 with epithelial-mesenchymal transition proteins in human CRC tissues and unleashed their association with colorectal cancer progression. The expression of these proteins was associated with advancement in tumor staging, nodal metastasis, and vascular invasion. Elevated CYR61 protein levels were also consistent with higher mesenchymal markers ZEB1 and Vimentin in collected biopsies and CRC cells. Moreover, expression of CYR61 promoted CRC cell migration, invasion, proliferation, and apoptosis. Our findings conclusively revealed the significant involvement of CYR61 in CRC progression through activating epithelial-mesenchymal transition. This discovery holds great promise for advancing therapeutic approaches in the treatment of CRC.

Shear loaded osteocyte-like-cells affect epithelial and mesenchymal gene expression in DU145 prostate cancer cells, while decreasing their invasion in vitro

Once prostate cancer (PC) metastasizes towards bone the 5-year survival rates drop with 70%, but it is largely unknown why. Bone is continuously mechanically loaded, which likely modulates the paracrine signaling from osteocytes towards PC cells to affect tumor behavior. We hypothesize that shear loaded osteocytes affect PC cell proliferation, invasion and epithelial and mesenchymal-related gene and protein expression. We cultured human DU145 cells, a commonly used cell line for prostate cancer metastases, in the conditioned medium (CM) from shear loaded or unloaded human osteocyte-like-cells (OCYLCs) for 1 and 3 days and assessed their number by staining nuclei with DAPI, their invasion by performing an invasion assay, and epithelial-to-mesenchymal (EMT)-related gene and protein expression by qPCR and immunocytochemistry. CM of shear loaded OCYLCs did not affect DU145 cell number compared to CM of static cultured OCYLCs, but decreased their invasion 1.34-fold. CM of shear loaded OCYLCs enhanced expression of epithelial genes: SYND1 and CDH1 after day 1, while it also enhanced CDH1 after day 3. CM of shear loaded osteocytes enhanced mesenchymal genes: VMN, Snail and MIP2 after day 1, while it decreased expression of mesenchymal CYR61 after day 3. We conclude that CM of shear loaded OCYLCs does not affect DU145 cell proliferation, but decreases their invasion, and differentially affects their EMT-related gene expression. Identifying paracrine signals from shear loaded osteocytes that decrease PC cell invasion may provide novel leads in developing treatments for bone metastases from PC.

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.

Drug Resistance in Glioma Cells Induced by a Mesenchymal-Amoeboid Migratory Switch

Cancer cell invasion is a precondition for tumour metastasis and represents one of the most devastating characteristics of cancer. The development of drugs targeting cell migration, known as migrastatics, may improve the treatment of highly invasive tumours such as glioblastoma (GBM). In this study, investigations into the role of the cell adhesion protein Cellular communication network factor 1 (CCN1, also known as CYR61) in GBM cell migration uncovered a drug resistance mechanism adopted by cells when treated with the small molecule inhibitor CCG-1423. This inhibitor binds to importin α/β inhibiting the nuclear translocation of the transcriptional co-activator MKL1, thus preventing downstream effects including migration. Despite this reported role as an inhibitor of cell migration, we found that CCG-1423 treatment did not inhibit GBM cell migration. However, we could observe cells now migrating by mesenchymal-amoeboid transition (MAT). Furthermore, we present evidence that CCN1 plays a critical role in the progression of GBM with increased expression in higher-grade tumours and matched blood samples. These findings support a potential role for CCN1 as a biomarker for the monitoring and potentially early prediction of GBM recurrence, therefore as such could help to improve treatment of and increase survival rates of this devastating disease.

Cyr61 promotes Schwann cell proliferation and migration via αvβ3 integrin

BACKGROUND

Schwann cells (SCs) play a crucial role in the repair of peripheral nerves. This is due to their ability to proliferate, migrate, and provide trophic support to axon regrowth. During peripheral nerve injury, SCs de-differentiate and reprogram to gain the ability to repair nerves. Cysteine-rich 61 (Cyr61/CCN1) is a member of the CCN family of matrix cell proteins and have been reported to be abundant in the secretome of repair mediating SCs. In this study we investigate the function of Cyr61 in SCs.

RESULTS

We observed Cyr61 was expressed both in vivo and in vitro. The promoting effect of Cyr61 on SC proliferation and migration was through autocrine and paracrine mechanisms. SCs expressed αvβ3 integrin and the effect of Cyr61 on SC proliferation and migration could be blocked via αvβ3 integrin. Cyr61 could influence c-Jun protein expression in cultured SCs.

CONCLUSIONS

In this study, we found that Cyr61 promotes SC proliferation and migration via αvβ3 integrin and regulates c-Jun expression. Our study contributes to the understanding of cellular and molecular mechanisms underlying SC's function during nerve injury, and thus, may facilitate the regeneration of peripheral nerves after injury.

BAG3 Proteomic Signature under Proteostasis Stress

The multifunctional HSP70 co-chaperone BAG3 (BCL-2-associated athanogene 3) represents a key player in the quality control of the cellular proteostasis network. In response to stress, BAG3 specifically targets aggregation-prone proteins to the perinuclear aggresome and promotes their degradation via BAG3-mediated selective macroautophagy. To adapt cellular homeostasis to stress, BAG3 modulates and functions in various cellular processes and signaling pathways. Noteworthy, dysfunction and deregulation of BAG3 and its pathway are pathophysiologically linked to myopathies, cancer, and neurodegenerative disorders. Here, we report a BAG3 proteomic signature under proteostasis stress. To elucidate the dynamic and multifunctional action of BAG3 in response to stress, we established BAG3 interactomes under basal and proteostasis stress conditions by employing affinity purification combined with quantitative mass spectrometry. In addition to the identification of novel potential BAG3 interactors, we defined proteins whose interaction with BAG3 was altered upon stress. By functional annotation and protein-protein interaction enrichment analysis of the identified potential BAG3 interactors, we confirmed the multifunctionality of BAG3 and highlighted its crucial role in diverse cellular signaling pathways and processes, ensuring cellular proteostasis and cell viability. These include protein folding and degradation, gene expression, cytoskeleton dynamics (including cell cycle and transport), as well as granulostasis, in particular.

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.

Ras-ERK1/2 signaling contributes to the development of colorectal cancer via regulating H3K9ac

BACKGROUNDS/AIMS

Ras is a control switch of ERK1/2 pathway, and hyperactivation of Ras-ERK1/2 signaling appears frequently in human cancers. However, the molecular regulation following by Ras-ERK1/2 activation is still unclear. This work aimed to reveal whether Ras-ERK1/2 promoted the development of colorectal cancer via regulating H3K9ac.

METHODS

A vector for expression of K-Ras mutated at G12 V and T35S was transfected into SW48 cells, and the acetylation of H3K9 was measured by Western blot analysis. MTT assay, colony formation assay, transwell assay, chromatin immunoprecipitation and RT-qPCR were performed to detect whether H3K9ac was contributed to K-Ras-mediated cell growth and migration. Furthermore, whether HDAC2 and PCAF involved in modification of H3K9ac following Ras-ERK1/2 activation were studied.

RESULTS

K-Ras mutated at G12 V and T35S induced a significant activation of ERK1/2 signaling and a significant down-regulation of H3K9ac. Recovering H3K9 acetylation by using a mimicked H3K9ac expression vector attenuated the promoting effects of Ras-ERK1/2 on tumor cells growth and migration. Besides, H3K9ac can be deacetylated by HDAC2 and MDM2-depedent degradation of PCAF.

CONCLUSION

H3K9ac was a specific target for Ras-ERK1/2 signaling pathway. H3K9 acetylation can be modulated by HDAC2 and MDM2-depedent degradation of PCAF. The revealed regulation provides a better understanding of Ras-ERK1/2 signaling in tumorigenesis.

BAG3 contributes to HGF-mediated cell proliferation, migration, and invasion via the Egr1 pathway in gastric cancer

INTRODUCTION:

Bcl2-associated athanogene 3 (BAG3) is elevated in several types of cancers. However, the role of BAG3 in progression of gastric cancer is unknown. Therefore, the present study aims to find out the role of BAG3 in hepatocyte growth factor (HGF)-mediated tumor progression and the molecular mechanisms by which HGF regulates BAG3 expression.

METHODS:

BAG3 mRNA and protein were measured using reverse transcription polymerase chain reaction and Western blot in the 2 human gastric cancer cell lines, NUGC3 and MKN28, treated with or without HGF. The effects of BAG3 knockdown on cell proliferation, cell invasion, and apoptosis were analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the in vitro 2-chamber invasion assay, and flow cytometry in BAG3 short hairpin RNA (shRNA)-transfected cells and control cells. The signaling pathways involved in BAG3 that are regulated by HGF were analyzed. The chromatin immunoprecipitation assay was used to determine binding of Egr1 to the BAG3 promoter.

RESULTS:

BAG3 mRNA and protein levels were increased following treatment with HGF. HGF-mediated BAG3 upregulation increased cell proliferation and cell invasion; however, it decreased apoptosis. HGF-mediated BAG3 upregulation is regulated by an ERK and Egr1-dependent pathway. BAG3 may have an important role in HGF-mediated cell proliferation and metastasis in gastric cancer through an ERK and Egr1-dependent pathway.

CONCLUSION:

This pathway may provide novel therapeutic targets and provide information for further identification of other targets of therapeutic significance in gastric cancer.

BAG3 regulates stability of IL-8 mRNA via interplay between HuR and miR-4312 in PDACs

Bcl-2 associated athanogene 3 (BAG3) is highly expressed in pancreatic ductal adenocarcinoma (PDAC), and its high expression appears to be a poor prognostic factor for patients with PDAC. In this study, we show that BAG3 knockdown significantly decreases migration and invasion of PDACs via reduction of interleukine-8 (IL-8) production. BAG3 knockdown regulates IL-8 expression at the posttranscriptional levels via interplay between recruitment of RNA-binding protein HuR and miR-4312. HuR binds to the cis-elements located in the 3'-untranslational region (UTR) of the IL-8 transcript to stabilize it, whereas miR-4312-containing miRNA-induced silencing complex (miRISC) is recruited to the adjacent seed element to destabilize it. The binding of HuR prevents the recruitment of Argonaute (Ago2), overriding miR-4312-mediated translation inhibition of IL-8. BAG3 knockdown decreases cytoplasmic distribution of HuR via increasing its phosphorylation at Ser202, therefore compromising its recruitment while promoting recruitment of miR-4312 containing miRISC to IL-8 transcript. Furthermore, our data indicate that only phosphorylated Ago2 at Ser387 interacts with IL-8 transcript. BAG3 knockdown increases phosphorylation of Ago2 at Ser387, thereby further promoting loading of miR-4312 containing miRISC to IL-8 transcript. Taken together, we propose that BAG3 promotes invasion by stabilizing IL-8 transcript via HuR recruitment, and subsequently suppressing the loading of miR-4312 containing miRISC in PDACs. Our results reveal a novel pathway linking BAG3 expression to enhanced PDAC metastasis, thus making BAG3 a potential target for intervention in pancreatic cancer.

BAG3 promotes the phenotypic transformation of primary rat vascular smooth muscle cells via TRAIL

Under normal physiological condition, the mature vascular smooth muscle cells (VSMCs) show differentiated phenotype. In response to various environmental stimuluses, VSMCs convert from the differentiated phenotype to dedifferentiated phenotype characterized by the increased ability of proliferation/migration and the reduction of contractile ability. The phenotypic transformation of VSMCs played an important role in atherosclerosis. Both Bcl-2-associated athanogene 3 (BAG3) and tumor necrosis factor-related apopt-osis inducing ligand (TRAIL) involved in apoptosis. The relationship between BAG3 and TRAIL and their effects the proliferation and migration in VSMCs are rarely reported. This study investigated the effects of BAG3 on the phenotypic modulation and the potential underlying mechanisms in primary rat VSMCs. Primary rat VSMCs were extracted and cultured in vitro. Cell proliferation was detected by cell counting, real-time cell analyzer (RTCA) and EdU incorporation. Cell migration was detected by wound healing, Transwell and RTCA. BAG3 and TRAIL were detected using real-time PCR and western blotting and the secreted proteins in the cultured media by dot blot. The expression of BAG3 increased with continued passages in cultured primary VSMCs. BAG3 promoted the proliferation and migration of primary rat VSMC in a time-dependent manner. BAG3 significantly increased the expression of TRAIL while had no effects on its receptors. TRAIL knockdown or blocking by neutralizing antibody inhibited the proliferation of VSMCs induced by BAG3. TRAIL knockdown exerted no obvious influence on the migration of VSMCs. Based on this study, we report for the first time that BAG3 was expressed in cultured primary rat VSMCs and the expression of BAG3 increased with continued passages. Furthermore, BAG3 promoted the proliferation of VSMCs via increasing the expression of TRAIL. In addition, we also demonstrated that BAG3 promoted the migration of VSMCs independent of TRAIL upregulation.

Overexpression of the anti-apoptotic protein BAG3 in human choroidal melanoma: A case report

Bcl-2-associated athanogene 3 (BAG3), a co-chaperone of heat shock protein 70 (HSP70), exerts anti-apoptotic effects in various malignant tumors. However, relationships between choroidal melanoma and BAG3 are poorly studied. This study investigated the expression of BAG3 in a case of human choroidal melanoma. Funduscopy, computed tomography, and single-photon emission computed tomography with the intravenous injection of N-isopropyl-p-[¹²³I] iodoamphetamine strongly indicated choroidal melanoma in a 68-year-old woman. Accordingly, we carried out an enucleation and pathological diagnosis. Proteins and total RNA were extracted from normal retinochoroidal and tumor tissues. Proteins were also extracted from ocular nevus tissues of other patients. We examined the expression of BAG3 protein and mRNA using Western blotting and the real-time quantitative polymerase chain reaction, respectively. Immunohistochemical stains were positive for melan-A, HMB-45, and S-100. Histopathology confirmed a choroidal melanoma. The expression of BAG3 protein and mRNA in the choroidal melanoma tissue was upregulated with respect to both normal retinochoroidal tissue and ocular nevus tissues from other patients. Because BAG3 may inhibit apoptosis of choroidal melanoma and facilitate its survival, overexpression of this gene product may be a prognostic marker and therapeutic target.

A Role for the Chaperone Complex BAG3-HSPB8 in Actin Dynamics, Spindle Orientation and Proper Chromosome Segregation during Mitosis

The co-chaperone BAG3, in complex with the heat shock protein HSPB8, plays a role in protein quality control during mechanical strain. It is part of a multichaperone complex that senses damaged cytoskeletal proteins and orchestrates their seclusion and/or degradation by selective autophagy. Here we describe a novel role for the BAG3-HSPB8 complex in mitosis, a process involving profound changes in cell tension homeostasis. BAG3 is hyperphosphorylated at mitotic entry and localizes to centrosomal regions. BAG3 regulates, in an HSPB8-dependent manner, the timely congression of chromosomes to the metaphase plate by influencing the three-dimensional positioning of the mitotic spindle. Depletion of BAG3 caused defects in cell rounding at metaphase and dramatic blebbing of the cortex associated with abnormal spindle rotations. Similar defects were observed upon silencing of the autophagic receptor p62/SQSTM1 that contributes to BAG3-mediated selective autophagy pathway. Mitotic cells depleted of BAG3, HSPB8 or p62/SQSTM1 exhibited disorganized actin-rich retraction fibres, which are proposed to guide spindle orientation. Proper spindle positioning was rescued in BAG3-depleted cells upon addition of the lectin concanavalin A, which restores cortex rigidity. Together, our findings suggest the existence of a so-far unrecognized quality control mechanism involving BAG3, HSPB8 and p62/SQSTM1 for accurate remodelling of actin-based mitotic structures that guide spindle orientation.

Small heat shock proteins (sHSP/HSPB) form a diverse family of ATP-independent chaperones. Some of them protect the proteome against aggregation during stress and others regulate normal biological processes through ill-defined mechanisms. Interactions between HSPB proteins and elements of the cytoskeleton are increasingly linked to their implication in human degenerative diseases and cancer. For instance, a multichaperone complex containing HSPB8 and its co-chaperone BAG3 would maintain muscle cell integrity by promoting the autophagic clearance of damaged components within F-actin structures. Selective autophagy is a targeted protein degradation mechanism for elimination of damaged organelles and proteins. It may also regulate removal of signaling proteins from their functionally relevant sites during intense remodeling of the cytoskeleton, as it occurs during mitosis. Here, we report a novel role for HSPB8 and BAG3 during mitosis in mammalian cells that involves the autophagic receptor p62/SQSTM1. We show that a reduction of any protein within the HSPB8-BAG3-p62/SQSTM signaling axis similarly impairs mitotic progression and chromosome segregation by affecting orientation of the mitotic spindle and assembly of mitotic-specific actin structures. Our findings establish a unique role for HSPB8 in a novel function of BAG3 in mitotic cell division and genome stability, through effect on remodeling of the actin cytoskeleton.

BAG3 regulates formation of the SNARE complex and insulin secretion

Insulin release in response to glucose stimulation requires exocytosis of insulin-containing granules. Glucose stimulation of beta cells leads to focal adhesion kinase (FAK) phosphorylation, which acts on the Rho family proteins (Rho, Rac and Cdc42) that direct F-actin remodeling. This process requires docking and fusion of secretory vesicles to the release sites at the plasma membrane and is a complex mechanism that is mediated by SNAREs. This transiently disrupts the F-actin barrier and allows the redistribution of the insulin-containing granules to more peripheral regions of the β cell, hence facilitating insulin secretion. In this manuscript, we show for the first time that BAG3 plays an important role in this process. We show that BAG3 downregulation results in increased insulin secretion in response to glucose stimulation and in disruption of the F-actin network. Moreover, we show that BAG3 binds to SNAP-25 and syntaxin-1, two components of the t-SNARE complex preventing the interaction between SNAP-25 and syntaxin-1. Upon glucose stimulation BAG3 is phosphorylated by FAK and dissociates from SNAP-25 allowing the formation of the SNARE complex, destabilization of the F-actin network and insulin release.

Cyr61 promotes CD204 expression and the migration of macrophages via MEK/ERK pathway in esophageal squamous cell carcinoma

Tumor-associated macrophages (TAMs) are known to be involved in the progression of various human malignancies. We previously demonstrated that CD204 was a useful marker for TAMs contributing to the angiogenesis, progression, and prognosis of human esophageal squamous cell carcinoma (ESCC). We also showed that conditioned media of ESCC cell lines induced CD204 expression in THP-1 human monocytic leukemia cells. Here, we performed a cDNA microarray analysis between THP-1 cells stimulated with TPA (macrophage [MΦ]-like THP-1 cells) treated with and without conditioned medium of ESCC cell line to clarify the molecular characteristics of TAMs in ESCC. From the microarray data, we discovered that Cyr61 was induced in CD204-positive-differentiated THP-1 cells (TAM-like THP-1 cells). In the ESCC microenvironment, not only cancer cells but also TAMs expressed Cyr61. Interestingly, the expression levels of Cyr61 showed a significant positive correlation with the number of CD204-positive macrophages in ESCCs by immunohistochemistry. Recombinant human Cyr61 (rhCyr61) promoted cell migration and induced the expression of CD204 along with the activation of the MEK/ERK pathway in MΦ-like THP-1 cells. Pretreatment with a MEK1/2 inhibitor significantly inhibited not only the Cyr61-mediated migration but also the CD204 expression in the MΦ-like THP-1 cells. These results suggest that Cyr61 may contribute to the expression of CD204 and the promotion of cell migration via the MEK/ERK pathway in TAMs in the ESCC microenvironment.

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.

BAG3-dependent noncanonical autophagy induced by proteasome inhibition in HepG2 cells

Emerging lines of evidence have shown that blockade of ubiquitin-proteasome system (UPS) activates autophagy. The molecular players that regulate the relationship between them remain to be elucidated. Bcl-2 associated athanogene 3 (BAG3) is a member of the BAG co-chaperone family that regulates the ATPase activity of heat shock protein 70 (HSP70) chaperone family. Studies on BAG3 have demonstrated that it plays multiple roles in physiological and pathological processes, including antiapoptotic activity, signal transduction, regulatory role in virus infection, cell adhesion and migration. Recent studies have attracted much attention on its role in initiation of autophagy. The current study, for the first time, demonstrates that proteasome inhibitors elicit noncanonical autophagy, which was not suppressed by inhibitors of class III phosphatidylinositol 3-kinase (PtdIns3K) or shRNA against Beclin 1 (BECN1). In addition, we demonstrate that BAG3 is ascribed to activation of autophagy elicited by proteasome inhibitors and MAPK8/9/10 (also known as JNK1/2/3 respectively) activation is also implicated via upregulation of BAG3. Moreover, we found that noncanonical autophagy mediated by BAG3 suppresses responsiveness of HepG2 cells to proteasome inhibitors.

Role of BAG3 protein in leukemia cell survival and response to therapy

The ability of BAG3, a member of the BAG family of heat shock protein (Hsp) 70 - cochaperones, to sustain the survival of human primary B-CLL and ALL cells was recognized about nine years ago. Since then, the anti-apoptotic activity of BAG3 has been confirmed in other tumor types, where it has been shown to regulate the intracellular concentration and localization of apoptosis-regulating factors, including NF-κB-activating (IKKγ) and Bcl2-family (Bax) proteins. Furthermore, growing evidences support its role in lymphoid and myeloid leukemia response to therapy. Moreover in the last years, the contribution of BAG3 to autophagy, a process known to be involved in the pathogenesis and response to therapy of leukemia cells, has been disclosed, opening a new avenue for the interpretation of the role of this protein in leukemias' biology.

Involvement of JNK and NF-κB pathways in lipopolysaccharide (LPS)-induced BAG3 expression in human monocytic cells

Lipopolysaccharide (LPS) is an outer-membrane glycolipid component of Gram-negative bacteria known for its fervent ability to activate monocytic cells and for its potent proinflammatory capabilities. Bcl-2-associated athanogene 3 (BAG3) is a survival protein that has been shown to be stimulated during cell response to stressful conditions, such as exposure to high temperature, heavy metals, proteasome inhibition, and human immunodeficiency virus 1 (HIV-1) infection. In addition, BAG3 regulates replication of Varicella-Zoster Virus (VZV) and Herpes Simplex Virus (HSV) replication, suggesting that BAG3 could participate in the host response to infection. In the current study, we found that LPS increased the expression of BAG3 in a dose- and time-dependent manner. Actinomycin D completely blocked the LPS-induced BAG3 accumulation, as well as LPS activated the proximal promoter of BAG3 gene, supported that the induction by LPS occurred at the level of gene transcription. LPS-induced BAG3 expression was blocked by JNK or NF-κB inhibition, suggesting that JNK and NF-κB pathways participated in BAG3 induction by LPS. In addition, we also found that induction of BAG3 was implicated in monocytic cell adhesion to extracellular matrix induced by LPS. Overall, the data support that BAG3 is induced by LPS via JNK and NF-κB-dependent signals, and involved in monocytic cell-extracellular matrix interaction, suggesting that BAG3 may have a role in the host response to LPS stimulation.

CCN1/CYR61: the very model of a modern matricellular protein

CCN1 (CYR61) is a dynamically expressed, multifunctional matricellular protein that plays essential roles in cardiovascular development during embryogenesis, and regulates inflammation, wound healing and fibrogenesis in the adult. Aberrant CCN1 expression is associated with myriad pathologies, including various cancers and diseases associated with chronic inflammation. CCN1 promotes diverse and sometimes opposing cellular responses, which can be ascribed, as least in part, to disparate activities mediated through its direct binding to distinct integrins in different cell types and contexts. Accordingly, CCN1 promotes cell proliferation, survival and angiogenesis by binding to integrin α(v)β(3), and induces apoptosis and senescence through integrin α(6)β(1) and heparan sulfate proteoglycans. The ability of CCN1 to trigger the accumulation of a robust and sustained level of reactive oxygen species underlies some of its unique activities as a matrix cell-adhesion molecule. Emerging studies suggest that CCN1 might be useful as a biomarker or therapeutic target in certain diseases.

BAG3: a multifaceted protein that regulates major cell pathways

Bcl2-associated athanogene 3 (BAG3) protein is a member of BAG family of co-chaperones that interacts with the ATPase domain of the heat shock protein (Hsp) 70 through BAG domain (110–124 amino acids). BAG3 is the only member of the family to be induced by stressful stimuli, mainly through the activity of heat shock factor 1 on bag3 gene promoter. In addition to the BAG domain, BAG3 contains also a WW domain and a proline-rich (PXXP) repeat, that mediate binding to partners different from Hsp70. These multifaceted interactions underlie BAG3 ability to modulate major biological processes, that is, apoptosis, development, cytoskeleton organization and autophagy, thereby mediating cell adaptive responses to stressful stimuli. In normal cells, BAG3 is constitutively present in a very few cell types, including cardiomyocytes and skeletal muscle cells, in which the protein appears to contribute to cell resistance to mechanical stress. A growing body of evidence indicate that BAG3 is instead expressed in several tumor types. In different tumor contexts, BAG3 protein was reported to sustain cell survival, resistance to therapy, and/or motility and metastatization. In some tumor types, down-modulation of BAG3 levels was shown, as a proof-of-principle, to inhibit neoplastic cell growth in animal models. This review attempts to outline the emerging mechanisms that can underlie some of the biological activities of the protein, focusing on implications in tumor progression.

IKK{gamma} protein is a target of BAG3 regulatory activity in human tumor growth

BAG3, a member of the BAG family of heat shock protein (HSP) 70 cochaperones, is expressed in response to stressful stimuli in a number of normal cell types and constitutively in a variety of tumors, including pancreas carcinomas, lymphocytic and myeloblastic leukemias, and thyroid carcinomas. Down-regulation of BAG3 results in cell death, but the underlying molecular mechanisms are still elusive. Here, we investigated the molecular mechanism of BAG3-dependent survival in human osteosarcoma (SAOS-2) and melanoma (M14) cells. We show that bag3 overexpression in tumors promotes survival through the NF-kappaB pathway. Indeed, we demonstrate that BAG3 alters the interaction between HSP70 and IKKgamma, increasing availability of IKKgamma and protecting it from proteasome-dependent degradation; this, in turn, results in increased NF-kappaB activity and survival. These results identify bag3 as a potential target for anticancer therapies in those tumors in which this gene is constitutively expressed. As a proof of principle, we show that treatment of a mouse xenograft tumor model with bag3siRNA-adenovirus that down-regulates bag3 results in reduced tumor growth and increased animal survival.