CRIPTO overexpression promotes mesenchymal differentiation in prostate carcinoma cells through parallel regulation of AKT and FGFR activities

A novel intronic circular RNA circFGFR1int2 up-regulates FGFR1 by recruiting transcriptional activators P65/FUS and suppressing miR-4687-5p to promote prostate cancer progression

Fibroblast growth factor receptor 1 (FGFR1) is a core component of the FGFs/FGFR pathway that activates multiple signalling pathways, including ERK1/2, PI3K/AKT, PLCγ, and NF-κB. Aberrant expression of FGFR1 due to gene amplification, chromosome rearrangement, point mutation, and epigenetic deregulations, have been reported in various cancers. FGFR1 overexpression has also been reported in prostate cancer (PCa), but the underlining mechanisms are not clear. Here we report a novel circular RNA, circFGFR1int2, derived from intron 2 of FGFR1 gene, which is overexpressed in PCa and associated with tumor progression. Importantly, we show that circFGFR1int2 facilitates FGFR1 transcription by recruiting transcription activators P65/FUS and by interacting with FGFR1 promoter. Moreover, we show that circFGFR1int2 suppresses post-transcriptional inhibitory effects of miR-4687-5p on FGFR1 mRNA. These mechanisms synergistically promote PCa cell growth, migration, and invasion. Overexpression of circFGFR1int2 is significantly correlated with higher tumor grade, Gleason score, and PSA level, and is a significant unfavorable prognosticator for CRPC-free survival (CFS) (RR = 3.277, 95% confidence interval: 1.192-9.009; P = 0.021). These findings unravelled novel mechanisms controlling FGFR1 gene expression by intronic circRNA and its potential clinicopathological utility as a diagnostic or therapeutic target.

Oncofetal Protein CRIPTO Is Involved in Wound Healing and Fibrogenesis in the Regenerating Liver and Is Associated with the Initial Stages of Cardiac Fibrosis

Oncofetal protein, CRIPTO, is silenced during homeostatic postnatal life and often re-expressed in different neoplastic processes, such as hepatocellular carcinoma. Given the reactivation of CRIPTO in pathological conditions reported in various adult tissues, the aim of this study was to explore whether CRIPTO is expressed during liver fibrogenesis and whether this is related to the disease severity and pathogenesis of fibrogenesis. Furthermore, we aimed to identify the impact of CRIPTO expression on fibrogenesis in organs with high versus low regenerative capacity, represented by murine liver fibrogenesis and adult murine heart fibrogenesis. Circulating CRIPTO levels were measured in plasma samples of patients with cirrhosis registered at the waitlist for liver transplantation (LT) and 1 year after LT. The expression of CRIPTO and fibrotic markers (αSMA, collagen type I) was determined in human liver tissues of patients with cirrhosis (on a basis of viral hepatitis or alcoholic disease), in cardiac tissue samples of patients with end-stage heart failure, and in mice with experimental liver and heart fibrosis using immuno-histochemical stainings and qPCR. Mouse models with experimental chronic liver fibrosis, induced with multiple shots of carbon tetrachloride (CCl4) and acute liver fibrosis (one shot of CCl4), were evaluated for CRIPTO expression and fibrotic markers. CRIPTO was overexpressed in vivo (Adenoviral delivery) or functionally sequestered by ALK4Fc ligand trap in the acute liver fibrosis mouse model. Murine heart tissues were evaluated for CRIPTO and fibrotic markers in three models of heart injury following myocardial infarction, pressure overload, and ex vivo induced fibrosis. Patients with end-stage liver cirrhosis showed elevated CRIPTO levels in plasma, which decreased 1 year after LT. Cripto expression was observed in fibrotic tissues of patients with end-stage liver cirrhosis and in patients with heart failure. The expression of CRIPTO in the liver was found specifically in the hepatocytes and was positively correlated with the Model for End-stage Liver Disease (MELD) score for end-stage liver disease. CRIPTO expression in the samples of cardiac fibrosis was limited and mostly observed in the interstitial cells. In the chronic and acute mouse models of liver fibrosis, CRIPTO-positive cells were observed in damaged liver areas around the central vein, which preceded the expression of αSMA-positive stellate cells, i.e., mediators of fibrosis. In the chronic mouse models, the fibrosis and CRIPTO expression were still present after 11 weeks, whereas in the acute model the liver regenerated and the fibrosis and CRIPTO expression resolved. In vivo overexpression of CRIPTO in this model led to an increase in fibrotic markers, while blockage of CRIPTO secreted function inhibited the extent of fibrotic areas and marker expression (αSMA, Collagen type I and III) and induced higher proliferation of residual healthy hepatocytes. CRIPTO expression was also upregulated in several mouse models of cardiac fibrosis. During myocardial infarction CRIPTO is upregulated initially in cardiac interstitial cells, followed by expression in αSMA-positive myofibroblasts throughout the infarct area. After the scar formation, CRIPTO expression decreased concomitantly with the αSMA expression. Temporal expression of CRIPTO in αSMA-positive myofibroblasts was also observed surrounding the coronary arteries in the pressure overload model of cardiac fibrosis. Furthermore, CRIPTO expression was upregulated in interstitial myofibroblasts in hearts cultured in an ex vivo model for cardiac fibrosis. Our results are indicative for a functional role of CRIPTO in the induction of fibrogenesis as well as a potential target in the antifibrotic treatments and stimulation of tissue regeneration.

Whence CRIPTO: The Reemergence of an Oncofetal Factor in 'Wounds' That Fail to Heal

There exists a set of factors termed oncofetal proteins that play key roles in ontogeny before they decline or disappear as the organism's tissues achieve homeostasis, only to then re-emerge in cancer. Although the unique therapeutic potential presented by such factors has been recognized for more than a century, their clinical utility has yet to be fully realized1. This review highlights the small signaling protein CRIPTO encoded by the tumor derived growth factor 1 (TDGF1/Tdgf1) gene, an oft cited oncofetal protein whose presence in the cancer literature as a tumor promoter, diagnostic marker and viable therapeutic target continues to grow. We touch lightly on features well established and well-reviewed since its discovery more than 30 years ago, including CRIPTO's early developmental roles and modulation of SMAD2/3 activation by a selected set of transforming growth factor β (TGF-β) family ligands. We predominantly focus instead on more recent and less well understood additions to the CRIPTO signaling repertoire, on its potential upstream regulators and on new conceptual ground for understanding its mode of action in the multicellular and often stressful contexts of neoplastic transformation and progression. We ask whence it re-emerges in cancer and where it 'hides' between the time of its fetal activity and its oncogenic reemergence. In this regard, we examine CRIPTO's restriction to rare cells in the adult, its potential for paracrine crosstalk, and its emerging role in inflammation and tissue regeneration-roles it may reprise in tumorigenesis, acting on subsets of tumor cells to foster cancer initiation and progression. We also consider critical gaps in knowledge and resources that stand between the recent, exciting momentum in the CRIPTO field and highly actionable CRIPTO manipulation for cancer therapy and beyond.

Extracellular Vesicles in Advanced Prostate Cancer: Tools to Predict and Thwart Therapeutic Resistance

Prostate cancer (PCa) is the second most frequent cancer and the fifth leading cause of cancer death among men worldwide. At first, advanced PCa is treated by androgen deprivation therapy with a good initial response. Nevertheless, recurrences occur, leading to Castrate-Resistance Prostate Cancer (CRPC). During the last decade, new therapies based on inhibition of the androgen receptor pathway or taxane chemotherapies have been used to treat CRPC patients leading to an increase in overall survival, but the occurrence of resistances limits their benefits. Numerous studies have demonstrated the implication of extracellular vesicles (EVs) in different cancer cellular mechanisms. Thus, the possibility to isolate and explore EVs produced by tumor cells in plasma/sera represents an important opportunity for the deciphering of those mechanisms and the discovery of biomarkers. Herein, we summarized the role of EVs in therapeutic resistance of advanced prostate cancer and their use to find biomarkers able to predict these resistances.

Targeting Nodal and Cripto-1: Perspectives Inside Dual Potential Theranostic Cancer Biomarkers

BACKGROUND

Elucidating the mechanisms of recurrence of embryonic signaling pathways in tumorigenesis has led to the discovery of onco-fetal players which have physiological roles during normal development but result aberrantly re-activated in tumors. In this context, Nodal and Cripto-1 are recognized as onco-developmental factors, which are absent in normal tissues but are overexpressed in several solid tumors where they can serve as theranostic agents.

OBJECTIVE

To collect, review and discuss the most relevant papers related to the involvement of Nodal and Cripto-1 in the development, progression, recurrence and metastasis of several tumors where they are over-expressed, with a particular attention to their occurrence on the surface of the corresponding sub-populations of cancer stem cells (CSC).

RESULTS

We have gathered, rationalized and discussed the most interesting findings extracted from some 370 papers related to the involvement of Cripto-1 and Nodal in all tumor types where they have been detected. Data demonstrate the clear connection between Nodal and Cripto-1 presence and their multiple oncogenic activities across different tumors. We have also reviewed and highlighted the potential of targeting Nodal, Cripto-1 and the complexes that they form on the surface of tumor cells, especially of CSC, as an innovative approach to detect and suppress tumors with molecules that block one or more mechanisms that they regulate.

CONCLUSION

Overall, Nodal and Cripto-1 represent two innovative and effective biomarkers for developing potential theranostic anti-tumor agents that target normal as well as CSC subpopulations and overcome both pharmacological resistance and tumor relapse.

Therapeutic Targeting of CD146/MCAM Reduces Bone Metastasis in Prostate Cancer

Prostate Cancer is the most common cancer and the second leading cause of cancer-related death in males. When prostate cancer acquires castration resistance, incurable metastases, primarily in the bone, occur. The aim of this study is to test the applicability of targeting melanoma cell adhesion molecule (MCAM; CD146) with a mAb for the treatment of lytic prostate cancer bone metastasis. We evaluated the effect of targeting MCAM using in vivo preclinical bone metastasis models and an in vitro bone niche coculture system. We utilized FACS, cell proliferation assays, and gene expression profiling to study the phenotype and function of MCAM knockdown in vitro and in vivo. To demonstrate the impact of MCAM targeting and therapeutic applicability, we employed an anti-MCAM mAb in vivo. MCAM is elevated in prostate cancer metastases resistant to androgen ablation. Treatment with DHT showed MCAM upregulation upon castration. We investigated the function of MCAM in a direct coculture model of human prostate cancer cells with human osteoblasts and found that there is a reduced influence of human osteoblasts on human prostate cancer cells in which MCAM has been knocked down. Furthermore, we observed a strongly reduced formation of osteolytic lesions upon bone inoculation of MCAM-depleted human prostate cancer cells in animal model of prostate cancer bone metastasis. This phenotype is supported by RNA sequencing (RNA-seq) analysis. Importantly, in vivo administration of an anti-MCAM human mAb reduced the tumor growth and lytic lesions. These results highlight the functional role for MCAM in the development of lytic bone metastasis and suggest that MCAM is a potential therapeutic target in prostate cancer bone metastasis. IMPLICATIONS: This study highlights the functional application of an anti-MCAM mAb to target prostate cancer bone metastasis.

Development of conformational antibodies targeting Cripto-1 with neutralizing effects in vitro

Human Cripto-1 (Cripto-1), the founding member of the EGF-CFC superfamily, is a key regulator of many processes during embryonic development and oncogenesis. Cripto-1 is barely present or even absent in normal adult tissues while it is aberrantly re-expressed in various tumors. Blockade of the CFC domain-mediated Cripto-1 functions is acknowledged as a promising therapeutic intervention point to inhibit the tumorigenic activity of the protein. In this work, we report the generation and characterization of murine monoclonal antibodies raised against the synthetic folded CFC [112-150] domain of the human protein. Through subtractive ELISA assays clones were screened for the ability to specifically recognize "hot spot" residues on the CFC domain, which are crucial for the interaction with Activin Type I receptor (ALK4) and GRP78. On selected antibodies, SPR and epitope mapping studies have confirmed their specificity and have revealed that recognition occurs only on a conformational epitope. Furthermore, FACS analyses have confirmed the ability of 1B4 antibody to recognize the membrane-anchored and soluble native Cripto-1 protein in a panel of human cancer cells. Finally, we have evaluated its functional effects through in vitro cellular signaling assays and cell cycle analysis. These findings suggest that the selected anti-CFC mAbs have the potential to neutralize the protein oncogenic activity and may be used as theranostic molecules suitable as tumor homing agents for Cripto-1-overexpressing cancer cells and tissues and to overcome drug-resistance in routine cancer therapies.

Role of Hypoxic Stress in Regulating Tumor Immunogenicity, Resistance and Plasticity

Hypoxia, or gradients of hypoxia, occurs in most growing solid tumors and may result in pleotropic effects contributing significantly to tumor aggressiveness and therapy resistance. Indeed, the generated hypoxic stress has a strong impact on tumor cell biology. For example, it may contribute to increasing tumor heterogeneity, help cells gain new functional properties and/or select certain cell subpopulations, facilitating the emergence of therapeutic resistant cancer clones, including cancer stem cells coincident with tumor relapse and progression. It controls tumor immunogenicity, immune plasticity, and promotes the differentiation and expansion of immune-suppressive stromal cells. In this context, manipulation of the hypoxic microenvironment may be considered for preventing or reverting the malignant transformation. Here, we review the current knowledge on how hypoxic stress in tumor microenvironments impacts on tumor heterogeneity, plasticity and resistance, with a special interest in the impact on immune resistance and tumor immunogenicity.

Knockdown of Cripto-1 inhibits the proliferation, migration, invasion, and angiogenesis in prostate carcinoma cells

Cripto-1 (CR-1) is a member of the epidermal growth factor-Cripto-1/FRL1/Cryptic gene family that plays a key role in the various malignant cancers. However, the role of CR-1 in prostate carcinoma (PCa) remains limited. The expression of CR-1 was down-regulated by small interfering RNA (siRNA). Western blot measured the expression levels of CR-1 and some related proteins. We performed Cell Counting Kit-8, 5-ethynyl-2-deoxyuridine (EdU) incorporation assay and flow cytometry to detect the cellular proliferation and cycle. The transwell assay was used to observe cellular migration and invasion. The ability of angiogenesis was evaluated by tube formation assay. Our results showed that CR-1 knockdown markedly inhibited cell proliferation and induced cycle arrest in G1 phase, as p21 and p27 were up-regulated, whereas cyclin D1 and cyclin E1 were diminished. Moreover, silencing of CR-1 dramatically inhibited cell migration and invasion, repressed matrix metalloproteinases, and disturbed epithelial-mesenchymal transition. CR-1 siRNA suppressed the secreted level of vascular endothelial growth factor, and reduced protein level of Vascular endothelial growth factor receptor 2. We further found that decreased CR-1 expression inhibited FAK/Src/PI3K and Wnt/b-catenin signalling in PCa cells. These results suggested CR-1 might be served as an effective therapeutic target in PCa.

CRIPTO promotes an aggressive tumour phenotype and resistance to treatment in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Despite increasing treatment options for this disease, prognosis remains poor. CRIPTO (TDGF1) protein is expressed at high levels in several human tumours and promotes oncogenic phenotype. Its expression has been correlated to poor prognosis in HCC. In this study, we aimed to elucidate the basis for the effects of CRIPTO in HCC. We investigated CRIPTO expression levels in three cohorts of clinical cirrhotic and HCC specimens. We addressed the role of CRIPTO in hepatic tumourigenesis using Cre-loxP-controlled lentiviral vectors expressing CRIPTO in cell line-derived xenografts. Responses to standard treatments (sorafenib, doxorubicin) were assessed directly on xenograft-derived ex vivo tumour slices. CRIPTO-overexpressing patient-derived xenografts were established and used for ex vivo drug response assays. The effects of sorafenib and doxorubicin treatment in combination with a CRIPTO pathway inhibitor were tested in ex vivo cultures of xenograft models and 3D cultures. CRIPTO protein was found highly expressed in human cirrhosis and hepatocellular carcinoma specimens but not in those of healthy participants. Stable overexpression of CRIPTO in human HepG2 cells caused epithelial-to-mesenchymal transition, increased expression of cancer stem cell markers, and enhanced cell proliferation and migration. HepG2-CRIPTO cells formed tumours when injected into immune-compromised mice, whereas HepG2 cells lacking stable CRIPTO overexpression did not. High-level CRIPTO expression in xenograft models was associated with resistance to sorafenib, which could be modulated using a CRIPTO pathway inhibitor in ex vivo tumour slices. Our data suggest that a subgroup of CRIPTO-expressing HCC patients may benefit from a combinatorial treatment scheme and that sorafenib resistance may be circumvented by inhibition of the CRIPTO pathway. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

JARID2 promotes invasion and metastasis of hepatocellular carcinoma by facilitating epithelial-mesenchymal transition through PTEN/AKT signaling

JARID2 is crucial for maintenance of pluripotency and differentiation of embryonic stem cells. However, little is known about the role of JARID2 in metastasis of hepatocellular carcinoma (HCC). This study found that JARID2 expression was significantly higher in HCC tissues than that in adjacent non-tumor liver tissues (ANLTs), and its expression level correlated with HCC metastasis. High JARID2 expression was significantly correlated with multiple tumor nodules, high Edmondson-Steiner grade, microvascular invasion, advanced TNM stage and advanced BCLC stage (all P < 0.05) and indicated poor prognosis of HCC in training and validation cohorts (all P < 0.05) totaling 182 patients. High JARID2 expression was an independent and significant risk factor for disease-free survival (DFS; P = 0.017) and overall survival (OS; P = 0.041) after curative liver resection in training cohort, and also validated as an independent and significant risk factor for DFS (P = 0.033) and OS (P = 0.031) in validation cohort. Moreover, down-regulation of JARID2 dramatically inhibited HCC cell migration, invasion, proliferation in vitro and metastasis in vivo, whereas overexpression of JARID2 significantly increased migration, invasion, proliferation in vitro and metastasis in vivo. Mechanistically, the data showed that JARID2 exerted its function by repressing PTEN expression through increasing H3K27 trimethylation (H3K27me3) at PTEN promoter region, which subsequently resulted in activation of protein kinase B (AKT) and enhanced epithelial-mesenchymal transition (EMT). In conclusion, this study revealed that JARID2 promotes invasion and metastasis of HCC by facilitating EMT through PTEN/AKT signaling.

Extracellular vesicles released by mesenchymal-like prostate carcinoma cells modulate EMT state of recipient epithelial-like carcinoma cells through regulation of AR signaling

Extracellular vesicles released from cancer cells may play an important role in cancer progression by shuttling oncogenic information into recipient cells. However, our knowledge is still fragmentary and there remain numerous questions regarding the mechanisms at play and the functional consequences of these interactions. We have recently established a mesenchymal-like prostate cancer cell line (22Rv1/CR-1; Mes-PCa). In this study, we assessed the effects of the extracellular vesicles released by these cells on recipient androgen-dependent epithelial VCaP prostate cancer cells. Mes-PCa derived vesicles were found to promote mesenchymal features in the recipient epithelial-like prostate cancer cells. This transformation was accompanied by a modulation of androgen receptor signaling and activation of TGFβ signaling pathway. Moreover, recipient cells acquiring mesenchymal traits displayed enhanced migratory and invasive features as well as increased resistance to the androgen receptor antagonist, enzalutamide. Our results suggest a previously unappreciated role for Mes-PCa secreted vesicles in cancer promotion by transferring cell-mediated signals and promoting phenotypic changes in recipient prostate cancer cells.

CRIPTO and its signaling partner GRP78 drive the metastatic phenotype in human osteotropic prostate cancer

CRIPTO (CR-1, TDGF1) is a cell surface/secreted oncoprotein actively involved in development and cancer. Here, we report that high expression of CRIPTO correlates with poor survival in stratified risk groups of prostate cancer (PCa) patients. CRIPTO and its signaling partner glucose-regulated protein 78 (GRP78) are highly expressed in PCa metastases and display higher levels in the metastatic ALDH^high sub-population of PC-3M-Pro4Luc2 PCa cells compared with non-metastatic ALDH^low. Coculture of the osteotropic PC-3M-Pro4Luc2 PCa cells with differentiated primary human osteoblasts induced CRIPTO and GRP78 expression in cancer cells and increases the size of the ALDH^high sub-population. Additionally, CRIPTO or GRP78 knockdown decreases proliferation, migration, clonogenicity and the size of the metastasis-initiating ALDH^high sub-population. CRIPTO knockdown reduces the invasion of PC-3M-Pro4Luc2 cells in zebrafish and inhibits bone metastasis in a preclinical mouse model. These results highlight a functional role for CRIPTO and GRP78 in PCa metastasis and suggest that targeting CRIPTO/GRP78 signaling may have significant therapeutic potential.

Acquisition of tumor cell phenotypic diversity along the EMT spectrum under hypoxic pressure: Consequences on susceptibility to cell-mediated cytotoxicity

Tumor escape to immunosurveillance and resistance to immune attacks present a major hurdle in cancer therapy, especially in the current era of new cancer immunotherapies. We report here that hypoxia, a hallmark of most solid tumors, orchestrates carcinoma cell heterogeneity through the induction of phenotypic diversity and the acquisition of distinct epithelial-mesenchymal transition (EMT) states. Using lung adenocarcinoma cells derived from a non-metastatic patient, we demonstrated that hypoxic stress induced phenotypic diversity along the EMT spectrum, with induction of EMT transcription factors (EMT-TFs) SNAI1, SNAI2, TWIST1, and ZEB2 in a hypoxia-inducible factor-1α (HIF1A)-dependent or -independent manner. Analysis of hypoxia-exposed tumor subclones, with pronounced epithelial or mesenchymal phenotypes, revealed that mesenchymal subclones exhibited an increased propensity to resist cytotoxic T lymphocytes (CTL), and natural killer (NK) cell-mediated lysis by a mechanism involving defective immune synapse signaling. Additionally, targeting EMT-TFs, or inhibition of TGF-β signaling, attenuated mesenchymal subclone susceptibility to immune attack. Together, these findings uncover hypoxia-induced EMT and heterogeneity as a novel driving escape mechanism to lymphocyte-mediated cytotoxicity, with the potential to provide new therapeutic opportunities for cancer patients.

A zebrafish xenograft model for studying human cancer stem cells in distant metastasis and therapy response

Lethal and incurable bone metastasis is one of the main causes of death in multiple types of cancer. A small subpopulation of cancer stem/progenitor-like cells (CSCs), also known as tumor-initiating cells from heterogenetic cancer is considered to mediate bone metastasis. Although over the past decades numerous studies have been performed in different types of cancer, it is still difficult to track small numbers of CSCs during the onset of metastasis. With use of noninvasive high-resolution imaging, transparent zebrafish embryos can be employed to dynamically visualize cancer progression and reciprocal interaction with stroma in a living organism. Recently we established a zebrafish CSC-xenograft model to visually and functionally analyze the role of CSCs and their interactions with the microenvironment at the onset of metastasis. Given the highly conserved human and zebrafish genome, transplanted human cancer cells are able to respond to zebrafish cytokines, modulate the zebrafish microenvironment, and take advantage of the zebrafish stroma during cancer progression. This chapter delineates the zebrafish CSC-xenograft model as a useful tool for both CSC biological study and anticancer drug screening.

EGFR-Based Immunoisolation as a Recovery Target for Low-EpCAM CTC Subpopulation

Circulating tumour cells (CTCs) play a key role in the metastasis process, as they are responsible for micrometastasis and are a valuable tool for monitoring patients in real-time. Moreover, efforts to develop new strategies for CTCs isolation and characterisation, and the translation of CTCs into clinical practice needs to overcome the limitation associated with the sole use of Epithelial Cell Adhesion Molecule (EpCAM) expression to purify this tumour cell subpopulation. CTCs are rare events in the blood of patients and are believed to represent the epithelial population from a primary tumour of epithelial origin, thus EpCAM immunoisolation is considered an appropriate strategy. The controversy stems from the impact that the more aggressive mesenchymal tumour phenotypes might have on the whole CTC population. In this work, we first characterised a panel of cell lines representative of tumour heterogeneity, confirming the existence of tumour cell subpopulations with restricted epithelial features and supporting the limitations of EpCAM-based technologies. We next developed customised polystyrene magnetic beads coated with antibodies to efficiently isolate the phenotypically different subpopulations of CTCs from the peripheral blood mononuclear cells (PBMCs) of patients with metastatic cancer. Besides EpCAM, we propose Epidermal Growth Factor Receptor (EGFR) as an additional isolation marker for efficient CTCs detection.