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The RNA helicase DDX21 is vital for ribosome biogenesis and is upregulated in CRC, but the mechanism by which DDX21 is dysregulated and by which DDX21 promotes tumorigenesis in CRC remains poorly understood. Here, we showed that DDX21 is a direct transcriptional target gene of β-catenin and mediates the protumorigenic function of β-catenin in CRC. DDX21 expression is correlated with the expression and activity of β-catenin, and high DDX21 expression is associated with a poor prognosis in CRC patients. Loss of DDX21 leads to cytoplasmic translocation and decreased transcriptional activity of YAP and suppresses the proliferation and migration of CRC cells, which can be partially rescued by YAP reactivation. Importantly, by using translation elongation inhibitors and DNA intercalators, we showed that ribosomal stress upregulates DDX21 expression and induces the downregulation of LATS and the activation of YAP, probably through the ZAKα-MKK4/7-JNK axis. Overall, our study revealed the transcriptional activation mechanism of DDX21 in CRC and the activation of YAP in the ribosomal stress response, indicating the potential of combination therapy involving the induction of ribosomal stress and YAP inhibition., (© 2024. The Author(s).)

Hepatocellular carcinoma (HCC) stands as one of the most aggressively advancing and lethal malignancies. Sorafenib is presently endorsed as a primary therapy for advanced liver cancer, but its resistance presents a formidable challenge. Previous studies have implicated a connection between post-sorafenib discontinuation rebound and the development of drug resistance, yet the underlying mechanism remains elusive. In this study, we discerned that Sorafenib induced a senescent phenotype in HCC cells and caused a cleavage of ubiquitin-binding protein p62. Mechanistic studies establish that truncated p62 drives cellular senescence by promoting proteasome-dependent degradation of 4EBP1. Furthermore, truncated p62 induced specific ubiquitination of 4EBP1. Crucially, virtual drug screening uncovered that dacinostat inhibited cellular senescence by blocking sorafenib-induced p62 cleavage. In summary, our findings imply that truncated p62 from sorafenib cleavage promotes senescence via 4EBP1 degradation. The prevention of p62 cleavage could emerge as a crucial strategy for impeding the sorafenib-induced cellular senescence., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Gastric cancer is one of the most lethal human malignancies in the world. Although great efforts are put in developing novel therapeutic targets, the effective targeting drugs are still limited. Recent studies reveal the abnormality of Hippo/YAP axis play critical role in the oncogenic process of gastric cancer. It is of great importance to demonstrate the regulation of Hippo signaling activity and YAP protein turnover in gastric cancer. Besides, the phosphorylation cascade on YAP function, which has been thoroughly investigated, the ubiquitination of YAP is also important in Hippo signaling status. Here, We utilized the DUB (Deubiquitinase) siRNA library to identify critical DUB for Hippo signaling. We discovered OTUB1 as a critical factor to facilitate gastric cancer cell stemness and progression, which deubiquitinated and stabilized YAP protein. The clinical data analysis implicated OTUB1 was higher expressed in gastric cancer, which correlated with YAP activity and poor survival. OUTB1 interacted with YAP protein via its OTU domain (Ovarian tumor domain) and deubiquitinated YAP at several lysine sites (K90, K280, K343, K494 and K497), which subsequently inhibited YAP degradation. Our study revealed a novel deubiquitinase of Hippo/YAP axis and one possible therapeutic target for YAP-driven gastric cancer., (© 2022. The Author(s).)

Inflammatory bowel diseases, like ulcerative colitis and Crohn's disease are frequently accompanied by colorectal cancers. However, the mechanisms underlying colitis-associated cancers are not fully understood. Src Kinase Associated Phosphoprotein 2 (SKAP2), a substrate of Src family kinases, is highly expressed in macrophages. Here, we examined the effects of SKAP2 on inflammatory responses in a mouse model of tumorigenesis with colitis induced by azoxymethane/dextran sulfate sodium. SKAP2 knockout increased the severity of colitis and tumorigenesis, as well as lipopolysaccharide (LPS) induced acute inflammation. SKAP2 attenuated inflammatory signaling in macrophages induced by uptake of cancer cell-derived exosomes. SKAP2 -/- mice were characterized by the activation of NF-κB signaling and the upregulation and release of cytokines including TNFα, IL-1β, IL-6, CXCL-9/-10/-13, and sICAM1; SKAP2 overexpression attenuated NF-κB activation. Mechanistically, SKAP2 formed a complex with the SHP-1 tyrosine phosphatase via association with the Sirpα transmembrane receptor. SKAP2 also physically associated with the TIR domain of MyD88, TIRAP, and TRAM, adaptors of toll-like receptor 4 (TLR4). SKAP2-mediated recruitment of the Sirpα/SHP-1 complex to TLR4 attenuated inflammatory responses, whereas direct interaction of SKAP2 with SHP-2 decreased SHP-2 activation. SHP-2 is required for efficient NF-κB activation and suppresses the TRAM/TRIF-INFβ pathway; therefore, SKAP2-mediated SHP-2 inhibition affected two signaling axes from TLR4. The present findings indicate that SKAP2 prevents excess inflammation by inhibiting the TLR4-NF-κB pathway, and it activates the TLR4-IFNβ pathway through SHP-1 and SHP-2, thereby suppressing inflammation-mediated tumorigenesis., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Colorectal cancer (CRC) is among the top five most common malignant tumors worldwide and has a high mortality rate. Identification of the mechanism of CRC and potential therapeutic targets is critical for improving survival. In the present study, we observed high expression of RAN binding protein 1 (RANBP1) in CRC tissues. Upregulated RANBP1 expression was strongly associated with TNM stages and was an independent risk factor for poor prognosis. In vitro and in vivo functional experiments demonstrated that RANBP1 promoted the proliferation and invasion of CRC cells and inhibited the apoptosis of CRC cells. Low RANBP1 expression reduced the expression levels of hsa-miR-18a, hsa-miR-183, and hsa-miR-106 microRNAs (miRNAs) by inhibiting the nucleoplasmic transport of precursor miRNAs (pre-miRNAs), thereby promoting the accumulation of the latter in the nucleus and reducing the expression of mature miRNAs. Further experiments and bioinformatic analyses demonstrated that RANBP1 promoted the expression of YAP by regulating miRNAs and the Hippo pathway. We also found that YAP acted as a transcriptional cofactor to activate RANBP1 transcription in combination with TEAD4 transcription factor. Thus, RANBP1 further promoted the progression of CRC by forming a positive feedback loop with YAP. Our results revealed the biological role and mechanism of RANBP1 in CRC for the first time, suggesting that RANBP1 can be used as a diagnostic molecule and a potential therapeutic target in CRC., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Metastasis of bladder cancer is a complex process and has been associated with poor clinical outcomes. However, the mechanisms of bladder cancer metastasis remain largely unknown. The present study found that the long noncoding RNA lnc00892 was significantly downregulated in bladder cancer tissues, with low lnc00892 expression associated with poor prognosis of bladder cancer patients. Lnc00892 significantly inhibited the migration, invasion, and metastasis of bladder cancer cells in vitro and in vivo. In-depth analysis showed that RhoA/C acted downstream of lnc00892 to inhibit bladder cancer metastasis. Mechanistically, lnc00892 reduces nucleolin gene transcription by competitively binding the promoter of nucleolin with c-Jun, thereby inhibiting nucleolin-mediated stabilization of RhoA/RhoC mRNA. Taken together, these findings provide novel insights into understanding the mechanisms of bladder cancer metastasis and suggest that lnc00892 can serve as a potential therapeutic target in patients with invasive bladder cancer., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Expression of β-crystallin B2 (CRYβB2) is elevated in African American (AA) breast tumors. The underlying mechanisms of CRYβB2-induced malignancy and the association of CRYβB2 protein expression with survival have not yet been described. Here, we report that the expression of CRYβB2 in breast cancer cells increases stemness, growth, and metastasis. Transcriptomics data revealed that CRYβB2 upregulates genes that are functionally associated with unfolded protein response, oxidative phosphorylation, and DNA repair, while down-regulating genes related to apoptosis. CRYβB2 in tumors promotes de-differentiation, an increase in mesenchymal markers and cancer-associated fibroblasts, and enlargement of nucleoli. Proteome microarrays identified a direct interaction between CRYβB2 and the nucleolar protein, nucleolin. CRYβB2 induces nucleolin, leading to the activation of AKT and EGFR signaling. CRISPR studies revealed a dependency on nucleolin for the pro-tumorigenic effects of CRYβB2. Triple-negative breast cancer (TNBC) xenografts with upregulated CRYβB2 are distinctively sensitive to the nucleolin aptamer, AS-1411. Lastly, in AA patients, higher levels of nucleolar CRYβB2 in primary TNBC correlates with decreased survival. In summary, CRYβB2 is upregulated in breast tumors of AA patients and induces oncogenic alterations consistent with an aggressive cancer phenotype. CRYβB2 increases sensitivity to nucleolin inhibitors and may promote breast cancer disparity., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

p53 is one of the most important tumor suppressor genes, and the exploration of p53-target genes is important for elucidation of its functional mechanisms. In this study, we identified Armadillo Repeat gene deleted in Velo-Cardio-Facial syndrome (ARVCF) as a direct target of p53 through ChIP-sequencing analysis. Activated p53 protein was found to bind to two distinct sites in the ARVCF gene, resulting in induction of ARVCF expression at both the mRNA and protein levels. We revealed that the knockdown of ARVCF inhibited p53-induced apoptosis. Interestingly, ARVCF interacted with hnRNPH2, which is involved in pre-mRNA splicing, and ARVCF knockdown induced dynamic changes in alternative splicing patterns. These results suggest that p53-induced ARVCF indirectly, but not directly, regulates p53 target selectivity through splicing alterations of specific genes. Thus, we demonstrated that the induction of ARVCF expression contributed to the tumor suppressive function of p53. Recently, it has been reported that many tumors have thousands of alternative splicing events that are not detectable in normal samples. ARVCF may play a role in alternative splicing events in cancer and may provide clues to explore novel approaches for cancer diagnosis and therapy.

Previous studies have shown that the main function of VASP is to regulate the cytoskeleton and play an important role in promoting tumor cell metastasis. In this study, we first reveal that VASP is located in the nucleus of breast cancer cells and elucidate a Wnt/β-catenin/VASP positive feedback loop. We identify that VASP is a target gene of Wnt/β-catenin signaling pathway, and activation of Wnt/β-catenin signaling pathway can significantly upregulate VASP protein expression, while upregulated VASP protein can in turn promote translocation of β-catenin and DVL3 proteins into the nucleus. In the nucleus, VASP, DVL3, β-catenin, and TCF4 can form VASP/DVL3/β-catenin/TCF4 protein complex, activating Wnt/β-catenin signaling pathway, and promoting the expression of target genes VASP, c-myc, and cyclin D1. Thus, our study reveals that there is a Wnt/β-catenin/VASP malignant positive feedback loop in breast cancer, which promotes the proliferation and migration of breast cancer cells, and breaking this positive feedback loop may provide new strategy for breast cancer treatment.

The melanocytic lineage, which is prominently exposed to ultraviolet radiation (UVR) and radiation-independent oxidative damage, requires specific DNA-damage response mechanisms to maintain genomic and transcriptional homeostasis. The coordinate lineage-specific regulation of intricately intertwined DNA repair and transcription is incompletely understood. Here we demonstrate that the Microphthalmia-associated transcription factor (MITF) directly controls general transcription and UVR-induced nucleotide excision repair by transactivation of GTF2H1 as a core element of TFIIH. Thus, MITF ensures the rapid resumption of transcription after completion of strand repair and maintains transcriptional output, which is indispensable for survival of the melanocytic lineage including melanoma in vitro and in vivo. Moreover, MITF controls c-MYC implicated in general transcription by transactivation of far upstream binding protein 2 (FUBP2/KSHRP), which induces c-MYC pulse regulation through TFIIH, and experimental depletion of MITF results in consecutive loss of CDK7 in the TFIIH-CAK subcomplex. Targeted for proteasomal degradation, CDK7 is dependent on transactivation by MITF or c-MYC to maintain a steady state. The dependence of TFIIH-CAK on sequence-specific MITF and c-MYC constitutes a previously unrecognized mechanism feeding into super-enhancer-driven or other oncogenic transcriptional circuitries, which supports the concept of a transcription-directed therapeutic intervention in melanoma.

Although cell polarity plays an important role in epithelial tumorigenesis, the consequence of polarity protein loss in prostatic tumorigenesis and the underlying mechanisms remain unclear. Using conditional knockout mouse models, we found in the current study that loss of polarity protein Par3 increases prostatic epithelial cell growth, elevates symmetrical cell divisions in basal cells, and randomizes spindle orientation in luminal cells, causing the development of high-grade prostatic intraepithelial neoplasia (PIN). Mechanistically, loss of Par3 dissociates the Par3/merlin/Lats1 complex, consequently inhibiting phosphorylation of Lats1 to attenuate the Hippo pathway. Furthermore, attenuated Hippo pathway enhances nuclear translocation of Yes-associated protein (YAP), which promotes cell proliferation and symmetrical cell divisions through transcriptional activation of Ki-67 and Sox2. In addition, Lats1 dephosphorylation impairs its interaction with G protein signaling modulator 2 (GPSM2, which is also known as LGN) that causes randomization of spindle orientation in luminal cells. Interestingly, co-deletion of Par3 and Lats1 for complete blockade of the Hippo pathway in mice results in prostate tumor initiation, whereas co-deletion of Par3 and YAP for disrupting YAP nuclear translocation reverses the phenotypes to a relatively normal state. Therefore, our findings highlight combination of Par3 loss and blockade of the Hippo pathway as a novel mechanism for prostatic tumorigenesis.

Yes-associated protein (YAP) has been identified as a key regulator of tissue homeostasis. However, the precise role and regulatory mechanism of YAP in esophageal squamous cell carcinoma (ESCC) remains unclear. Here we report that the genetic or pharmacological inhibition of YAP repressed cancer stem cell (CSC)-like properties, including tumorsphere-forming potential, cell motility, and chemoresistance in vitro, and was sufficient to attenuate tumor growth and CSC marker expression in ESCC xenografts. Mechanistically, YAP transcriptionally activated its downstream target SOX9 via TEAD1-mediated binding. We also observed a positive correlation between YAP signaling and SOX9 expression in two independent clinical cohorts. Intriguingly, YAP-targeting microRNAs, including miR-506-3p, which were induced by SOX9, post-transcriptionally repressed YAP expression, contributing to a negative feedback mechanism. Dual inhibition of YAP and SOX9 robustly suppressed malignant phenotypes. Notably, ESCC samples from The Cancer Genome Atlas (TCGA) dataset had frequent (44%) instances of YAP gene amplification and genetic inactivation of Hippo pathway regulators. Nuclear YAP expression was elevated in 197 ESCC tissues from a Chinese cohort. Together, our findings provide evidence that genetic hyperactivation of YAP unbalances the YAP-SOX9 feedback loop and confers CSC-like features in ESCC, suggesting that this YAP-SOX9 circuit represents a potential therapeutic target.

Over the past decades, the Hippo has been established as a crucial pathway involved in organ size control and cancer suppression. Dysregulation of Hippo signaling and hyperactivation of its downstream effector YAP are frequently associated with various human cancers. However, the underlying significance of such YAP activation in cancer development and therapy has not been fully characterized. In this study, we reported that the Hippo signaling deficiency can lead to a YAP-dependent oncogene addiction for cancer cells. Through a clinical compound library screen, we identified histone deacetylase (HDAC) inhibitors as putative inhibitors to suppress YAP expression. Importantly, HDAC inhibitors specifically targeted the viability and xenograft tumor growth for the cancer cells in which YAP is constitutively active. Taken together, our results not only establish an active YAP-induced oncogene addiction in cancer cells, but also lay the foundation to develop targeted therapies for the cancers with Hippo dysfunction and YAP activation.

Tumor metastasis is the most common cause of cancer death. Elucidation of the mechanism of tumor metastasis is therefore important in the development of novel, effective anti-cancer therapies to reduce cancer mortality. Interaction between cancer cells and surrounding stromal cells in the tumor microenvironment is a key factor in tumor metastasis. Using a co-culture assay system with human prostate cancer LNCaP cells and primary human prostate stromal cells, we identified epithelial membrane protein 1 (EMP1) as a gene with elevated expression in the cancer cells. The orthotopic injection of LNCaP cells overexpressing EMP1 (EMP1-LNCaP cells) into the prostate of nude mice induced lymph node and lung metastases, while that of control LNCaP cells did not. EMP1-LNCaP cells had higher cell motility and Rac1 activity than control LNCaP cells. These results were also observed in other lines of cancer cells. We newly identified copine-III as an intracellular binding partner of EMP1. Knockdown of copine-III attenuated the increased cell motility and Rac1 activity in EMP1-LNCaP cells. Reduced cell motility and Rac1 activity following knockdown of copine-III in EMP1-LNCaP cells were recovered by re-expression of wild-type copine-III, but not of a copine-III mutant incapable of interacting with EMP1, suggesting the importance of the EMP1-copine-III interaction. Phosphorylated and activated Src and a Rac guanine nucleotide exchange factor Vav2 were found to be involved in the EMP1-induced enhancement of cell motility and Rac1 activation. Moreover, EMP1 was highly expressed in prostate cancer samples obtained from patients with higher Gleason score. These results demonstrate that upregulation of EMP1 significantly increases cancer cell migration that leads to tumor metastasis, suggesting that EMP1 may play an essential role as a positive regulator of tumor metastasis.

Mutations in the isocitrate dehydrogenase 1 (IDH1) gene have been identified in a number of cancer types, including brain cancer. The Cancer Genome Atlas project has revealed that IDH1 mutations occur in 70-80% of grade II and grade III gliomas. Until recently, most of the functional studies of IDH1 mutations in cellular models have been conducted in overexpression systems with the IDH1 wild type background. In this study, we employed a modified CRISPR/Cas9 genome editing technique called "single base editing", and efficiently introduced heterozygous IDH1 R132H mutation (IDH1 R132H/WT ) in human astroglial cells. Global DNA methylation profiling revealed hypermethylation as well as hypomethylation induced by IDH1 R132H/WT . Global gene expression analysis identified molecular targets and pathways altered by IDH1 R132H/WT , including cell proliferation, extracellular matrix (ECM), and cell migration. Our phenotype analysis indicated that compared with IDH1 wild type cells, IDH1 R132H/WT promoted cell migration by upregulating integrin β4 (ITGB4); and significantly inhibited cell proliferation. Using our mutated IDH1 models generated by "single base editing", we identified novel molecular targets of IDH1 R132H/WT , namely Yes-associated protein (YAP) and its downstream signaling pathway Notch, to mediate the cell growth-inhibiting effect of IDH1 R132H/WT . In summary, the "single base editing" strategy has successfully created heterozygous IDH1 R132H mutation that recapitulates the naturally occurring IDH1 mutation. Our isogenic cellular systems that differ in a single nucleotide in one allele of the IDH1 gene provide a valuable model for novel discoveries of IDH1 R132H/WT -driven biological events.

We have identified an epidermal cancer stem (ECS) cell population that drives formation of rapidly growing and highly invasive and vascularized tumors. VEGF-A and neuropilin-1 (NRP-1) are highly expressed in ECS cell tumors and VEGF-A/NRP-1 interaction is required for ECS cell survival and tumor vascularization. We now identify a novel signaling cascade that is triggered by VEGF-A/NRP-1. We show that NRP-1 forms a complex with GIPC1 and α6/β4-integrin to activate FAK/Src signaling, which leads to stabilization of a YAP1/∆Np63α to enhance ECS cell survival, invasion, and angiogenesis. Loss of NRP-1, GIPC1, α6/β4-integrins, YAP1, or ∆Np63α reduces these responses. Moreover, restoration of constituently active YAP1 or ∆Np63α in NRP-1 null cells restores the ECS cell phenotype. Tumor xenograft experiments show that NRP-1 knockout ECS cells form small tumors characterized by reduced vascularization as compared to wild-type cells. The NRP-1 knockout tumors display signaling changes consistent with a role for the proposed signaling cascade. These studies suggest that VEGF-A interacts with NRP-1 and GIPC1 to regulate α6/β4-integrin, FAK, Src, PI3K/PDK1, LATS1 signaling to increase YAP1/∆Np63α accumulation to drive ECS cell survival, angiogenesis, and tumor formation.

Nuclear activated β-catenin plays a causative role in colorectal cancers (CRC) but remains an elusive therapeutic target. Using human CRC cells harboring different Wnt/β-catenin pathway mutations in APC/KRAS or β-catenin/KRAS genes, and both genetic and pharmacological knockdown approaches, we show that oncogenic β-catenin signaling negatively regulates the expression of NHERF1 (Na + /H + exchanger 3 regulating factor 1), a PDZ-adaptor protein that is usually lost or downregulated in early dysplastic adenomas to exacerbate nuclear β-catenin activity. Chromatin immunoprecipitation (ChIP) assays demonstrated that β-catenin represses NHERF1 via TCF4 directly, while the association between TCF1 and the Nherf1 promoter increased upon β-catenin knockdown. To note, the occurrence of a cytostatic survival response in settings of single β-catenin-depleted CRC cells was abrogated by combining NHERF1 inhibition via small hairpin RNA (shRNA) or RS5517, a novel PDZ1-domain ligand of NHERF1 that prevented its ectopic nuclear entry. Mechanistically, dual NHERF1/β-catenin targeting promoted an autophagy-to-apoptosis switch consistent with the activation of Caspase-3, the cleavage of PARP and reduced levels of phospho-ERK1/2, Beclin-1, and Rab7 autophagic proteins compared with β-catenin knockdown alone. Collectively, our data unveil novel β-catenin/TCF-dependent mechanisms of CRC carcinogenesis, also offering preclinical proof of concept for combining β-catenin and NHERF1 pharmacological inhibitors as a mechanism-based strategy to augment apoptotic death of CRC cells refractory to current Wnt/β-catenin-targeted therapeutics.

Liver cancer comprises a group of malignant tumors, among which hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) are the most common. ICC is especially pernicious and associated with poor clinical outcome. Studies have shown that a subset of human ICCs may originate from mature hepatocytes. However, the mechanisms driving the trans-differentiation of hepatocytes into malignant cholangiocytes remain poorly defined. We adopted lineage tracing techniques and an established murine hepatocyte-derived ICC model by hydrodynamic injection of activated forms of AKT (myr-AKT) and Yap (YapS127A) proto-oncogenes. Wild-type, Notch1 flox/flox , and Notch2 flox/flox mice were used to investigate the role of canonical Notch signaling and Notch receptors in AKT/Yap-driven ICC formation. Human ICC and HCC cell lines were transfected with siRNA against Notch2 to determine whether Notch2 regulates biliary marker expression in liver tumor cells. We found that AKT/Yap-induced ICC formation is hepatocyte derived and this process is strictly dependent on the canonical Notch signaling pathway in vivo. Deletion of Notch2 in AKT/Yap-induced tumors switched the phenotype from ICC to hepatocellular adenoma-like lesions, while inactivation of Notch1 in hepatocytes did not result in significant histomorphological changes. Finally, in vitro studies revealed that Notch2 silencing in ICC and HCC cell lines down-regulates the expression of Sox9 and EpCAM biliary markers. Notch2 is the major determinant of hepatocyte-derived ICC formation in mice.

Despite the general focus on an invasive and de-differentiated phenotype as main driver of cancer metastasis, in melanoma patients many metastatic lesions display a high degree of pigmentation, indicative for a differentiated phenotype. Indeed, studies in mice and fish show that melanoma cells switch to a differentiated phenotype at secondary sites, possibly because in melanoma differentiation is closely linked to proliferation through the lineage-specific transcriptional master regulator MITF. Importantly, while a lot of effort has gone into identifying factors that induce the de-differentiated/invasive phenotype, it is not well understood how the switch to the differentiated/proliferative phenotype is controlled. We identify collagen as a contributor to this switch. We demonstrate that collagen stiffness induces melanoma differentiation through a YAP/PAX3/MITF axis and show that in melanoma patients increased collagen abundance correlates with nuclear YAP localization. However, the interrogation of large patient datasets revealed that in the context of the tumour microenvironment, YAP function is more complex. In the absence of fibroblasts, YAP/PAX3-mediated transcription prevails, but in the presence of fibroblasts tumour growth factor-β suppresses YAP/PAX3-mediated MITF expression and induces YAP/TEAD/SMAD-driven transcription and a de-differentiated phenotype. Intriguingly, while high collagen expression is correlated with poorer patient survival, the worst prognosis is seen in patients with high collagen expression, who also express MITF target genes such as the differentiation markers TRPM1, TYR and TYRP1, as well as CDK4. In summary, we reveal a distinct lineage-specific route of YAP signalling that contributes to the regulation of melanoma pigmentation and uncovers a set of potential biomarkers predictive for poor survival.

Trastuzumab is the only target to be approved as the first-line treatment of HER2 positive metastatic gastric cancer, but ubiquitous resistance decreases its therapeutic benefit. In this study, we found HER4, phosphorylation HER4 (p-HER4) and the mesenchymal marker Vimentin increased in trastuzumab-resistant cells (MKN45TR and NCI-N87TR), while epithelial markers expressions in trastuzumab-resistant cell lines and animal models decreased. Additionally, silencing HER4 prevented the epithelial-mesenchymal transition and led to decreased proliferation and migration in vitro and in vivo. The expression of YAP1, a vital downstream interacted target of HER4, decreased when HER4 was knocked down. Interestingly, stimulation of NRG1 could compromise the inhibitory impact and rescue cell survival; whereas, transfection of siYAP1 sensitized trastuzumab-treated cells. Expression analysis of the proteins in patient-derived xenograft model (PDX) mice showed that HER4, p-HER4, YAP1, and Vimentin were clearly upregulated in the trastuzumab-resistant mice compared to mice without trastuzumab resistance. However, HER2 and E-cadherin were downregulated in response to continuous treatment with trastuzumab. These findings elucidated that the central role of the HER4-YAP1 axis in trastuzumab resistance of HER2-positive gastric cancer cells through induction of EMT. Hence, regulating the HER4-YAP1 axis might be a promising strategy for clinical interventions in patients with HER2-positive gastric cancer.

The Yes-associated protein 1 (YAP1), a major downstream effector of the Hippo pathway, functions as a transcriptional regulator and has an important role in cellular control of organ size and tumor growth. Elevated oncogenic activity of YAP1 has been clarified in different types of human cancers, which contributes to cancer cell survival and chemoresistance. However, the molecular mechanism of YAP1 overexpression in cancer is still not clear. Here we demonstrate that the deubiquitination enzyme USP9X deubiquitinates and stabilizes YAP1, thereby promoting cancer cell survival. Increased USP9X expression correlates with increased YAP1 protein in human breast cancer cell lines and patient samples. Moreover, depletion of USP9X increases YAP1 polyubiquitination, which in turn elevates YAP1 turnover and cell sensitivity to chemotherapy. Overall, our study establishes the USP9X-YAP1 axis as an important regulatory mechanism of breast cancer and provides a rationale for potential therapeutic interventions in the treatment of breast cancer.

Tissue inhibitor of metalloproteinase-1 (TIMP-1), a member of the TIMP family (TIMP-1 to 4), is highly expressed in various types of cancer and forms a complex with its receptor CD63 and Integrin β1. However, the precise oncogenic mechanism of TIMP-1 remains unclear. Yes-associated protein (YAP) and transcriptional co-activator with PDZ binding motif (TAZ) are transcription co-activators enhancing the transcription of specific genes related to cell proliferation. But the mechanism of aberrant YAP/TAZ activation in cancer is not fully understood. Here, we showed that TIMP-1 activates YAP/TAZ as novel downstream targets to promote cell proliferation. The TIMP-1-CD63-Integrin β1 axis activates Src and promotes RhoA-mediated F-actin assembly, leading to LATS1/2 inactivation. This results in under-phosphorylation, protein stabilization and nuclear translocation of YAP/TAZ (YAP/TAZ activation); CTGF production; and cell proliferation. Furthermore, the TIMP-1-YAP/TAZ axis is aberrantly activated in various types of cancer cells or tissues. TIMP-1 knockdown inhibits cell proliferation through YAP/TAZ inactivation in cancer cells. This study found that TIMP-1 accelerates cell proliferation through YAP/TAZ activation in cancer, and suggests the TIMP-1-YAP/TAZ axis may be a novel potential drug target for cancer patients.

Clinical intervention for patients with advanced prostate cancer (PCa) remains challenging due to the inevitable recurrence of castration-resistant prostate cancer (CRPC) after androgen deprivation therapy (ADT). Cancer stem cells (CSCs) with serial tumor-propagating capacity are considered to be the driving force for PCa progression and recurrence. In this study, we report that the miR-302/367 cluster, a previously identified potent pluripotency regulator, is upregulated in prostate tumors. Specifically, the forced expression of the miR-302/367 cluster accelerates the in vitro and in vivo growth of PCa cells and their resistance to androgen ablation, whereas the knockdown of the miR-302/367 cluster using anti-sense RNA suppresses the incidence of formation, growth rate and endpoint weight of PCa cell tumors. Mechanistically, we find that LATS2, a key component of the tumor-suppressive Hippo signaling pathway, acts as a direct target of the miR-302/367 cluster in PCa cells. The downregulation of LATS2 by the miR-302/367 cluster reduces the phosphorylation and enhances the nuclear translocation of the YAP oncoprotein. Conversely, the restoration of LATS2 expression abrogates the tumor-promoting effects of forced miR-302/367 cluster expression. Collectively, the potent pluripotency regulator-triggered miR-302/367/LATS2/YAP pathway is essential for prostate tumor-propagating cells and promotes castration resistance. Thus, targeting this signaling axis may represent a promising therapeutic strategy for CRPC.

Overexpression of the transcriptional coregulators C-terminal binding proteins 1 and 2 (CtBP1 and 2) occurs in many human solid tumors and is associated with poor prognosis. CtBP modulates oncogenic gene expression programs and is an emerging drug target, but its oncogenic role is unclear. Consistent with this oncogenic potential, exogenous CtBP2 transformed primary mouse and human cells to anchorage independence similarly to mutant H-Ras. To investigate CtBP's contribution to in vivo tumorigenesis, Apc min/+ mice, which succumb to massive intestinal polyposis, were bred to Ctbp2 +/- mice. CtBP interacts with adenomatous polyposis coli (APC) protein, and is stabilized in both APC-mutated human colon cancers and Apc min/+ intestinal polyps. Ctbp2 heterozygosity increased the median survival of Apc min/+ mice from 21 to 48 weeks, and reduced polyp formation by 90%, with Ctbp2 +/- polyps exhibiting reduced levels of β-catenin and its oncogenic transcriptional target, cyclin D1. CtBP's potential as a therapeutic target was studied by treating Apc min/+ mice with the CtBP small-molecule inhibitors 4-methylthio-2-oxobutyric acid and 2-hydroxy-imino phenylpyruvic acid, both of which reduced polyposis by more than half compared with vehicle treatment. Phenocopying Ctbp2 deletion, both Ctbp inhibitors caused substantial decreases in the protein level of Ctbp2, as well its oncogenic partner β-catenin, and the effects of the inhibitors on CtBP and β-catenin levels could be modeled in an APC-mutated human colon cancer cell line. CtBP2 is thus a druggable transforming oncoprotein critical for the evolution of neoplasia driven by Apc mutation.

Recent evidences suggest that stearoyl-CoA-desaturase 1 (SCD1), the enzyme involved in monounsaturated fatty acids synthesis, has a role in several cancers. We previously demonstrated that SCD1 is important in lung cancer stem cells survival and propagation. In this article, we first show, using primary cell cultures from human lung adenocarcinoma, that the effectors of the Hippo pathway, Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), are required for the generation of lung cancer three-dimensional cultures and that SCD1 knock down and pharmacological inhibition both decrease expression, nuclear localization and transcriptional activity of YAP and TAZ. Regulation of YAP/TAZ by SCD1 is at least in part dependent upon β-catenin pathway activity, as YAP/TAZ downregulation induced by SCD1 blockade can be rescued by the addition of exogenous wnt3a ligand. In addition, SCD1 activation of nuclear YAP/TAZ requires inactivation of the β-catenin destruction complex. In line with the in vitro findings, immunohistochemistry analysis of lung adenocarcinoma samples showed that expression levels of SCD1 co-vary with those of β-catenin and YAP/TAZ. Mining available gene expression data sets allowed to observe that high co-expression levels of SCD1, β-catenin, YAP/TAZ and downstream targets have a strong negative prognostic value in lung adenocarcinoma. Finally, bioinformatics analyses directed to identify which gene combinations had synergistic effects on clinical outcome in lung cancer showed that poor survival is associated with high co-expression of SCD1, β-catenin and the YAP/TAZ downstream target birc5. In summary, our data demonstrate for the first time the involvement of SCD1 in the regulation of the Hippo pathway in lung cancer, and point to fatty acids metabolism as a key regulator of lung cancer stem cells.

Mps One Binder Kinase Activator (MOB)1A/1B are core components of the Hippo pathway. These proteins, which coactivate LArge Tumour Suppressor homologue kinases, are also tumour suppressors. To investigate MOB1A/B's roles in normal physiology and lung cancer, we generated doxycycline (Dox)-inducible, bronchioalveolar epithelium-specific, null mutations of MOB1A/B in mice (SPC-rtTA/(tetO) 7 -Cre/Mob1a flox/flox /Mob1b -/- ; termed luMob1DKO mice). Most mutants (70%) receiving Dox in utero (luMob1DKO (E6.5-18.5) mice) died of hypoxia within 1 h post-birth. Their alveolar epithelial cells showed increased proliferation, impaired YAP1/TAZ-dependent differentiation and decreased surfactant protein production, all features characteristic of human respiratory distress syndrome. Intriguingly, mutant mice that received Dox postnatally (luMob1DKO (P21-41) mice) did not develop spontaneous lung adenocarcinomas, and urethane treatment-induced lung tumour formation was decreased (rather than increased). Lungs of luMob1DKO (P21-41) mice exhibited increased detachment of bronchiolar epithelial cells and decreased numbers of the bronchioalveolar stem cells thought to initiate lung adenocarcinomas. YAP1/TAZ-NKX2.1-dependent expression of collagen XVII, a key hemidesmosome component, was also reduced. Thus, a MOB1-YAP1/TAZ-NKX2.1 axis is essential for normal lung homeostasis and expression of the collagen XVII protein necessary for alveolar stem cell maintenance in the lung niche.

Wild-type p53 (wtp53) is described as a tumour suppressor gene; mutations in this gene occur in many human cancers and promote oncogenic capacity. Here, we establish that the oncogenic activity of mutant p53 (mtp53) is driven by the WASP-interacting protein (WIP). WIP knockdown from mtp53-expressing glioblastoma and breast cancer cells (BCC) greatly reduced proliferation and growth capacity of cancer stem cell (CSC)-like cells and decreased CSC-like markers (CD133, CD44 or YAP/TAZ). mtp53 overexpression in human astrocytes enhanced their proliferative capacity in suspension culture and increased expression of CSC markers and WIP. WIP knockdown compromised tumour glioblastoma and BCC growth capacity in vivo. We show that WIP is phosphorylated by AKT2 and is regulated by mtp53/p63 through enhancement of PI3K/AKT2-mediated integrin/receptor recycling pathways. WIP regulates this oncogenic pathway by controlling YAP/TAZ stability. We thus establish a new CSC signalling pathway downstream of mtp53 in which AKT2 regulates WIP and controls YAP/TAZ stability.

The loss of E-cadherin causes dysfunction of the cell-cell junction machinery, which is an initial step in epithelial-to-mesenchymal transition (EMT), facilitating cancer cell invasion and the formation of metastases. A set of transcriptional repressors of E-cadherin (CDH1) gene expression, including Snail1, Snail2 and Zeb2 mediate E-cadherin downregulation in breast cancer. However, the molecular mechanisms underlying the control of E-cadherin expression in breast cancer progression remain largely unknown. Here, by using global gene expression approaches, we uncover a novel function for Cdc42 GTPase-activating protein (CdGAP) in the regulation of expression of genes involved in EMT. We found that CdGAP used its proline-rich domain to form a functional complex with Zeb2 to mediate the repression of E-cadherin expression in ErbB2-transformed breast cancer cells. Conversely, knockdown of CdGAP expression led to a decrease of the transcriptional repressors Snail1 and Zeb2, and this correlated with an increase in E-cadherin levels, restoration of cell-cell junctions, and epithelial-like morphological changes. In vivo, loss of CdGAP in ErbB2-transformed breast cancer cells impaired tumor growth and suppressed metastasis to lungs. Finally, CdGAP was highly expressed in basal-type breast cancer cells, and its strong expression correlated with poor prognosis in breast cancer patients. Together, these data support a previously unknown nuclear function for CdGAP where it cooperates in a GAP-independent manner with transcriptional repressors to function as a critical modulator of breast cancer through repression of E-cadherin transcription. Targeting Zeb2-CdGAP interactions may represent novel therapeutic opportunities for breast cancer treatment.

The transmission of cellular information requires fine and subtle regulation of proteins that need to interact in a coordinated and specific way to form efficient signaling networks. The spatial and temporal coordination relies on scaffold proteins. Thanks to protein interaction domains such as PDZ domains, scaffold proteins organize multiprotein complexes enabling the proper transmission of cellular information through intracellular networks. NHERF1/EBP50 is a PDZ-scaffold protein that was initially identified as an organizer and regulator of transporters and channels at the apical side of epithelia through actin-binding ezrin-moesin-radixin proteins. Since, NHERF1/EBP50 has emerged as a major regulator of cancer signaling network by assembling cancer-related proteins. The PDZ-scaffold EBP50 carries either anti-tumor or pro-tumor functions, two antinomic functions dictated by EBP50 expression or subcellular localization. The dual function of NHERF1/EBP50 encompasses the regulation of several major signaling pathways engaged in cancer, including the receptor tyrosine kinases PDGFR and EGFR, PI3K/PTEN/AKT and Wnt-β-catenin pathways.

Mechanisms regulating the transition of mammary epithelial cells (MECs) to mammary stem cells (MaSCs) and to tumor-initiating cells (TICs) have not been entirely elucidated. The p53 family member, p63, is critical for mammary gland development and contains transactivation domain isoforms, which have tumor-suppressive activities, and the ΔN isoforms, which act as oncogenes. In the clinic, p63 is often used as a diagnostic marker, and further analysis of the function of TAp63 in the mammary gland is critical for improved diagnosis and patient care. Loss of TAp63 in mice leads to the formation of aggressive metastatic mammary adenocarcinoma at 9-16 months of age. Here we show that TAp63 is crucial for the transition of mammary cancer cells to TICs. When TAp63 is lost, MECs express embryonic and MaSC signatures and activate the Hippo pathway. These data indicate a crucial role for TAp63 in mammary TICs and provide a mechanism for its role as a tumor- and metastasis-suppressor in breast cancer.

The Yes-associated protein (YAP) is an effector that transduces the output of the Hippo pathway to transcriptional modulation. Considering the role of YAP in cancers, this protein has emerged as a key node in malignancy development. In this study, we determined that Aurora A kinase acts as a positive regulator for YAP-mediated transcriptional machinery. Specifically, YAP associates with Aurora A predominantly in the nucleus. Activation of Aurora A can impinge on YAP activity through direct phosphorylation. Moreover, aberrant expression of YAP and Aurora A signaling is highly correlated with triple-negative breast cancer (TNBC). We herein provide evidence to establish the functional relevance of this newly discovered regulatory axis in TNBC.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a high degree of inflammation and profound immune suppression. Here we identify Yes-associated protein (Yap) as a critical regulator of the immunosuppressive microenvironment in both mouse and human PDAC. Within Kras:p53 mutant pancreatic ductal cells, Yap drives the expression and secretion of multiple cytokines/chemokines, which in turn promote the differentiation and accumulation of myeloid-derived suppressor cells (MDSCs) both in vitro and in vivo. Pancreas-specific knockout of Yap or antibody-mediated depletion of MDSCs promoted macrophage reprogramming, reactivation of T cells, apoptosis of Kras mutant neoplastic ductal cells and pancreatic regeneration after acute pancreatitis. In primary human PDAC, YAP expression levels strongly correlate with an MDSC gene signature, and high expression of YAP or MDSC-related genes predicts decreased survival in PDAC patients. These results reveal multifaceted roles of YAP in PDAC pathogenesis and underscore its promise as a therapeutic target for this deadly disease.

The tumor-suppressor RUNX3 has a critical role in a lineage determination, cell cycle arrest and apoptosis. Lozenge (Lz), a Drosophila homolog of mammalian RUNX family members, has integral roles in these processes and specifically in eye cell fate determination. To elucidate the genetic modifiers of Lz/RUNX3, we performed a large-scale functional screen in a fly mutant library. The screen revealed genetic interactions between the Lz, Rac and Hippo pathways. Analysis of interactions among these genes revealed that the defective phenotype resulting from activation of Yki, an end point effector of the Hippo pathway, was suppressed by Lz and enhanced by Rac-Trio. Molecular biological analysis using mammalian homologs reveled that LATS1/2-mediated YAP phosphorylation-facilitated dissociation of the YAP-TEAD4 complex and association of the YAP-RUNX3 complex. When cells were stimulated to proliferate, activated RAC-TRIO signaling inhibited LATS1/2-mediated YAP phosphorylation; consequently, YAP dissociated from RUNX3 and associated with TEAD, thereby replacing the YAP-RUNX3 complex with YAP-TEAD. RUNX3 contributed to both association and dissociation of YAP-TEAD complex, most likely through the formation of the YAP-TEAD-RUNX3 ternary complex. Ectopic expression of RUNX3 in MKN28 gastric cancer cells reduced tumorigenicity, and the tumor-suppressive activity of RUNX3 was associated with its ability to interact with YAP. These results identify a novel regulatory mechanism, mediated by the Hippo and RAC-TRIO pathways, that changes the binding partner of YAP.

Ewing sarcoma is characterized by chromosomal translocations fusing the EWS gene with various members of the ETS family of transcription factors, most commonly FLI1. EWS-FLI1 is an aberrant transcription factor driving Ewing sarcoma tumorigenesis by either transcriptionally inducing or repressing specific target genes. Herein, we showed that Sprouty 1 (SPRY1), which is a physiological negative feedback inhibitor downstream of fibroblast growth factor (FGF) receptors (FGFRs) and other RAS-activating receptors, is an EWS-FLI1 repressed gene. EWS-FLI1 knockdown specifically increased the expression of SPRY1, while other Sprouty family members remained unaffected. Analysis of SPRY1 expression in a panel of Ewing sarcoma cells showed that SPRY1 was not expressed in Ewing sarcoma cell lines, suggesting that it could act as a tumor suppressor gene in these cells. In agreement, induction of SPRY1 in three different Ewing sarcoma cell lines functionally impaired proliferation, clonogenic growth and migration. In addition, SPRY1 expression inhibited extracellular signal-related kinase/mitogen-activated protein kinase (MAPK) signaling induced by serum and basic FGF (bFGF). Moreover, treatment of Ewing sarcoma cells with the potent FGFR inhibitor PD-173074 reduced bFGF-induced proliferation, colony formation and in vivo tumor growth in a dose-dependent manner, thus mimicking SPRY1 activity in Ewing sarcoma cells. Although the expression of SPRY1 was low when compared with other tumors, SPRY1 was variably expressed in primary Ewing sarcoma tumors and higher expression levels were significantly associated with improved outcome in a large patient cohort. Taken together, our data indicate that EWS-FLI1-mediated repression of SPRY1 leads to unrestrained bFGF-induced cell proliferation, suggesting that targeting the FGFR/MAPK pathway can constitute a promising therapeutic approach for this devastating disease.

Atypical protein kinase Cι (PKCι) is an oncogene in lung and ovarian cancer. The PKCι gene PRKCI is targeted for frequent tumor-specific copy number gain (CNG) in both lung squamous cell carcinoma (LSCC) and ovarian serous carcinoma (OSC). We recently demonstrated that in LSCC cells PRKCI CNG functions to drive transformed growth and tumorigenicity by activating PKCι-dependent cell autonomous Hedgehog (Hh) signaling. Here, we assessed whether OSC cells harboring PRKCI CNG exhibit similar PKCι-dependent Hh signaling. Surprisingly, we find that whereas PKCι is required for the transformed growth of OSC cells harboring PRKCI CNG, these cells do not exhibit PKCι-dependent Hh signaling or Hh-dependent proliferation. Rather, transformed growth of OSC cells is regulated by PKCι-dependent nuclear localization of the oncogenic transcription factor, YAP1. Lentiviral shRNA-mediated knockdown (KD) of PKCι leads to decreased nuclear YAP1 and increased YAP1 binding to angiomotin (AMOT), which sequesters YAP1 in the cytoplasm. Biochemical analysis reveals that PKCι directly phosphorylates AMOT at a unique site, Thr750, whose phosphorylation inhibits YAP1 binding. Pharmacologic inhibition of PKCι decreases YAP1 nuclear localization and blocks OSC tumor growth in vitro and in vivo. Immunohistochemical analysis reveals a strong positive correlation between tumor PKCι expression and nuclear YAP1 in primary OSC tumor samples, indicating the clinical relevance of PKCι-YAP1 signaling. Our results uncover a novel PKCι-AMOT-YAP1 signaling axis that promotes OSC tumor growth, and provide a rationale for therapeutic targeting of this pathway for treatment of OSC., Competing Interests: The authors declare that they have no conflicts of interest to disclose.

MicroRNA-375 (miR-375) is frequently elevated in prostate tumors and cell-free fractions of patient blood, but its role in genesis and progression of prostate cancer is poorly understood. In this study, we demonstrated that miR-375 is inversely correlated with epithelial-mesenchymal transition signatures (EMT) in clinical samples and can drive mesenchymal-epithelial transition (MET) in model systems. Indeed, miR-375 potently inhibited invasion and migration of multiple prostate cancer lines. The transcription factor YAP1 was found to be a direct target of miR-375 in prostate cancer. Knockdown of YAP1 phenocopied miR-375 overexpression, and overexpression of YAP1 rescued anti-invasive effects mediated by miR-375. Furthermore, transcription of the miR-375 gene was shown to be directly repressed by the EMT transcription factor, ZEB1. Analysis of multiple patient cohorts provided evidence for this ZEB1-miR-375-YAP1 regulatory circuit in clinical samples. Despite its anti-invasive and anti-EMT capacities, plasma miR-375 was found to be correlated with circulating tumor cells in men with metastatic disease. Collectively, this study provides new insight into the function of miR-375 in prostate cancer, and more broadly identifies a novel pathway controlling epithelial plasticity and tumor cell invasion in this disease.

Id1 is a helix-loop-helix transcriptional modulator that increases the aggressiveness of malignant glial neoplasms. Since most glioblastomas (GBMs) show increased phosphatidylinositol-3 kinase (PI-3K) signaling, we sought to determine whether this pathway regulates Id1 expression. Higher basal Id1 expression correlates with dysregulated PI-3K signaling in multiple established GBM cell lines. Further characterization of PI-3K-dependent Id1 regulation reveals that chemical or genetic inhibition of PI-3K signaling reduces Id1 protein but not mRNA expression. Overall, PI-3K signaling appears to enhance Id1 translation with no significant effect on its stability. PI-3K signaling is known to regulate protein translation through mTORC1-dependent phosphorylation of 4E-BP1, which reduces its association with and inhibition of the translation initiation factor eIF4E. Interestingly, while inhibition of PI-3K and AKT lowers 4E-BP1 phosphorylation and expression of Id1 in all cases, inhibition of TORC1 with rapamycin does not consistently have a similar effect, suggesting an alternative mechanism for PI-3K-dependent regulation of Id1 translation. We now identify a potential role for the serine-threonine phosphatase PPM1G in translational regulation of Id1 protein expression. PPM1G knockdown by siRNA increase both 4E-BP1 phosphorylation and Id1 expression and PPM1G and 4E-BP1 co-associates in GBM cells. Furthermore, PPM1G is a phosphoprotein and this phosphorylation appears to be regulated by PI-3K activity. Finally, PI-3K inhibition increases PPM1G activity when assessed by an in vitro phosphatase assay. Our findings provide the first evidence that the PI-3K/AKT signaling pathway modulates PPM1G activity resulting in a shift in the balance between hyper- and hypo-phosphorylated 4E-BP1 and translational regulation of Id1 expression., Competing Interests: None

Pancreatic cancer is one of the most lethal malignancies, with virtually all patients eventually succumbing to their disease. Mutations in p53 have been documented in >50% of pancreatic cancers. Owing to the high incidence of p53 mutations in PanIN 3 lesions and pancreatic tumors, we interrogated the comparative ability of adult pancreatic acinar and ductal cells to respond to oncogenic Kras and mutant Tp53(R172H) using Hnf1b:CreER(T2) and Mist1:CreER(T2) mice. These studies involved co-activation of a membrane-tethered GFP lineage label, allowing for direct visualization and isolation of cells undergoing Kras and mutant p53 activation. Kras activation in Mist1(+) adult acinar cells resulted in brisk PanIN formation, whereas no evidence of pancreatic neoplasia was observed for up to 6 months following Kras activation in Hnf1beta(+) adult ductal cells. In contrast to the lack of response to oncogenic Kras alone, simultaneous activation of Kras and mutant p53 in adult ductal epithelium generated invasive PDAC in 75% of mice as early as 2.5 months after tamoxifen administration. These data demonstrate that pancreatic ductal cells, whereas exhibiting relative resistance to oncogenic Kras alone, can serve as an effective cell of origin for pancreatic ductal adenocarcinoma in the setting of gain-of-function mutations in p53.

Sprouty (SPRY) appears to act as a tumor suppressor in cancer, whereas we demonstrated that SPRY2 functions as a putative oncogene in colorectal cancer (CRC) (Oncogene, 2010, 29: 5241-5253). We investigated the mechanisms by which SPRY regulates epithelial-mesenchymal transition (EMT) in CRC. SPRY1 and SPRY2 mRNA transcripts were significantly upregulated in human CRC. Suppression of SPRY2 repressed AKT2 and EMT-inducing transcription factors and significantly increased E-cadherin expression. Concurrent downregulation of SPRY1 and SPRY2 also increased E-cadherin and suppressed mesenchymal markers in colon cancer cells. An inverse expression pattern between AKT2 and E-cadherin was established in a human CRC tissue microarray. SPRY2 negatively regulated miR-194-5p that interacts with AKT2 3' untranslated region. Mir-194 mimics increased E-cadherin expression and suppressed cancer cell migration and invasion. By confocal microscopy, we demonstrated redistribution of E-cadherin to plasma membrane in colon cancer cells transfected with miR-194. Spry1(-/-) and Spry2(-/-) double mutant mouse embryonic fibroblasts exhibited decreased cell migration while acquiring several epithelial markers. In CRC, SPRY drive EMT and may serve as a biomarker of poor prognosis.

Dysregulation of the Hippo pathway occurs in a variety of cancers and often correlates with a poor prognosis. To further explore the potential role of Hippo pathway dysregulation in tumor development and progression, we investigated its downstream transcription factor TEAD4 in colorectal cancer (CRC). Increased expression and nuclear localization of TEAD4 were found in a significant portion of CRC tissues, in association with metastasis and a poor prognosis. In CRC cells, TEAD4 knockdown induced the mesenchymal-epithelial transition and decreased cell mobility in vitro and metastasis in vivo. Microarray analysis revealed that TEAD4 promoted cell adhesion and upregulated the epithelial-mesenchymal transition-related transcriptome in CRC cells. Vimentin was identified as a new direct target gene mediating TEAD4 function in CRC cells, whereby forced vimentin expression markedly reversed TEAD4-knockdown-induced cell morphological changes and decreased mobility. Interestingly, rescued expression of both WT TEAD4 and a Y429H mutant can reverse the mesenchymal-epithelial transition and increase vimentin expression, cell mobility and metastatic potential in TEAD4-knockdown CRC cells. The discrepant expression of YAP and TEAD4 in CRC tissues, the rescue ability of TEAD4 mutant defect in YAP binding and no effect on vimentin expression by YAP knockdown in CRC cells, all implicated a YAP-independent manner of TEAD4 function in CRC. Furthermore, vimentin positively correlated and CDH1 reversely correlated with the level of TEAD4 in CRC tissues and xenograft tumors. Our results suggest that TEAD4 nuclear expression can serve as a biomarker for CRC progression and poor prognosis. The transcription factor TEAD4 regulates a pro-metastasis transcription program in a YAP-independent manner in CRC, thus providing a novel mechanism of TEAD4 transcriptional regulation and its oncogenic role in CRC, independently of the Hippo pathway.

Current standard of care for muscle-invasive urothelial cell carcinoma (UCC) is surgery along with perioperative platinum-based chemotherapy. UCC is sensitive to cisplatin-based regimens, but acquired resistance eventually occurs, and a subset of tumors is intrinsically resistant. Thus, there is an unmet need for new therapeutic approaches to target chemotherapy-resistant UCC. Yes-associated protein (YAP) is a transcriptional co-activator that has been associated with bladder cancer progression and cisplatin resistance in ovarian cancer. In contrast, YAP has been shown to induce DNA damage associated apoptosis in non-small cell lung carcinoma. However, no data have been reported on the YAP role in UCC chemo-resistance. Thus, we have investigated the potential dichotomous role of YAP in UCC response to chemotherapy utilizing two patient-derived xenograft models recently established. Constitutive expression and activation of YAP inversely correlated with in vitro and in vivo cisplatin sensitivity. YAP overexpression protected while YAP knockdown sensitized UCC cells to chemotherapy and radiation effects via increased accumulation of DNA damage and apoptosis. Furthermore, pharmacological YAP inhibition with verteporfin inhibited tumor cell proliferation and restored sensitivity to cisplatin. In addition, nuclear YAP expression was associated with poor outcome in UCC patients who received perioperative chemotherapy. In conclusion, these results suggest that YAP activation exerts a protective role and represents a pharmacological target to enhance the anti-tumor effects of DNA damaging modalities in the treatment of UCC.

The myc oncogene is overexpressed in almost half of all breast and ovarian cancers, but attempts at therapeutic interventions against myc have proven to be challenging. Myc regulates multiple biological processes, including the cell cycle, and as such is associated with cell proliferation and tumor progression. We identified a protein signature of high myc, low p27 and high phospho-Rb significantly correlated with poor patient survival in breast and ovarian cancers. Screening of a miRNA library by functional proteomics in multiple cell lines and integration of data from patient tumors revealed a panel of five microRNAs (miRNAs) (miR-124, miR-365, miR-34b*, miR-18a and miR-506) as potential tumor suppressors capable of reversing the p27/myc/phospho-Rb protein signature. Mechanistic studies revealed an RNA-activation function of miR-124 resulting in direct induction of p27 protein levels by binding to and inducing transcription on the p27 promoter region leading to a subsequent G1 arrest. Additionally, in vivo studies utilizing a xenograft model demonstrated that nanoparticle-mediated delivery of miR-124 could reduce tumor growth and sensitize cells to etoposide, suggesting a clinical application of miRNAs as therapeutics to target the functional effect of myc on tumor growth.

The mammalian target of rapamycin (mTOR) is commonly activated in colon cancer. mTOR complex 1 (mTORC1) is a major downstream target of the PI3K/ATK pathway and activates protein synthesis by phosphorylating key regulators of messenger RNA translation and ribosome synthesis. Rapamycin analogs Everolimus and Temsirolimus are non-ATP-competitive mTORC1 inhibitors, and suppress proliferation and tumor angiogenesis and invasion. We now show that apoptosis plays a key role in their anti-tumor activities in colon cancer cells and xenografts through the DR5, FADD and caspase-8 axis, and is strongly enhanced by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and 5-fluorouracil. The induction of DR5 by rapalogs is mediated by the ER stress regulator and transcription factor CHOP, but not the tumor suppressor p53, on rapid and sustained inhibition of 4E-BP1 phosphorylation, and attenuated by eIF4E expression. ATP-competitive mTOR/PI3K inhibitors also promote DR5 induction and FADD-dependent apoptosis in colon cancer cells. These results establish activation of ER stress and the death receptor pathway as a novel anticancer mechanism of mTOR inhibitors.

Metastasis of cancer cells involves multiple steps, including their dissociation from the primary tumor and invasion through the endothelial cell barrier to enter the circulation and finding their way to distant organ sites where they extravasate and establish metastatic lesions. Deficient contact inhibition is a hallmark of invasive cancer cells, yet surprisingly the vascular invasiveness of commonly studied cancer cell lines is regulated by the density at which cells are propagated in culture. Cells grown at high density were less effective at invading an endothelial monolayer than cells grown at low density. This phenotypic difference was also observed in a zebrafish model of vascular invasion of cancer cells after injection into the yolk sac and extravasation of cancer cells into tissues from the vasculature. The vascular invasive phenotypes were reversible. A kinome-wide RNA interference screen was used to identify drivers of vascular invasion by panning small hairpin RNA (shRNA) library-transduced noninvasive cancer cell populations on endothelial monolayers. The selection of invasive subpopulations showed enrichment of shRNAs targeting the large tumor suppressor 1 (LATS1) kinase that inhibits the activity of the transcriptional coactivator yes-associated protein (YAP) in the Hippo pathway. Depletion of LATS1 from noninvasive cancer cells restored the invasive phenotype. Complementary to this, inhibition or depletion of YAP inhibited invasion in vitro and in vivo. The vascular invasive phenotype was associated with a YAP-dependent upregulation of the cytokines IL6, IL8 and C-X-C motif ligand 1, 2 and 3. Antibody blockade of cytokine receptors inhibited invasion and confirmed that they are rate-limiting drivers that promote cancer cell vascular invasiveness and could provide therapeutic targets.

Yes-associated protein (YAP) is overexpressed and has an oncogenic role in hepatocellular carcinoma (HCC). However, whether membrane protein can serve not only as a tumor marker that reflects YAP function but also as a therapeutic target that stimulates tumorigenesis in HCC remains unknown. Here we report that the membrane protein melanoma cell adhesion molecule (MCAM) was under positive regulation by YAP and was highly elevated in HCC cells. Within the MCAM promoter, we found the presence of a cAMP Response Element (CRE; -32 to -25 nt), which is conserved among species and is essential for YAP- and CREB-dependent regulation. Moreover, the interaction between CREB and YAP at the CRE site was dependent on PTPIY-WW domain interactions. However, MCAM expression was low and could not be regulated by YAP in breast and colon cancer cells because of the low levels of the acetyltransferase p300. In HCC cells, high levels of p300 facilitated the binding of YAP to the MCAM promoter, which in turn enhanced histone acetylation and polymerase II recruitment through the dissociation of the deacetylase Sirt1. These results suggest that MCAM is an HCC-specific target of YAP. In clinical serum samples, we found that the serum levels of MCAM were highly elevated in patients with HCC compared with healthy controls and with patients with cirrhosis, hepatitis, colon cancer and breast cancer. MCAM levels were shown to be a slightly better indicator than serum alpha-fetoprotein for predicting HCC. We further demonstrated that MCAM is essential for the survival and transformation of HCC. Mechanistically, MCAM induced translation initiation and the transcriptional activities of c-Jun/c-Fos. In addition, AKT activation had an essential role in the MCAM-promoted binding of eukaryotic initiation factor 4E to c-Jun/c-Fos mRNA. In conclusion, we demonstrated that MCAM may be a potential tumor marker and therapeutic target for the diagnosis and treatment of HCC.

The polyomavirus middle T antigen (PyMT) is an oncogene that activates the non-receptor tyrosine kinase, c-Src, and physically interacts with Taz (WWTR1). Taz is a pro-oncogenic transcription coactivator of the Tead transcription factors. The Hippo tumor suppressor pathway activates the kinase Lats, which phosphorylates Taz, leading to its nuclear exclusion and blunting Tead coactivation. We found that Taz was required for transformation by PyMT, but counter-intuitively, Taz was exclusively cytoplasmic in the presence of PyMT. We demonstrate that in the presence of PyMT, wild-type Taz was phosphorylated by Lats, in a Src-dependent manner. Consistently, a Lats refractory Taz mutant did not undergo cytoplasmic retention by PyMT. We show that Yap, the Taz paralog, and Shp2 phosphatase were nuclear excluded as well. Our findings describe a noncanonical activation of Lats, and an unprecedented Tead-independent role for Taz and Yap in viral-mediated oncogenesis.

Lung cancer is the leading cause of cancer death worldwide, with metastasis underlying majority of related deaths. Angiomotin (AMOT), a scaffold protein, has been shown to interact with oncogenic Yes-associated protein/transcriptional co-activator with a PDZ-binding motif (YAP/TAZ) proteins, suggesting a potential role in tumor progression. However, the functional role of AMOT in lung cancer remains unknown. This study aimed to identify the patho-physiological characteristics of AMOT in lung cancer progression. Results revealed that AMOT expression was significantly decreased in clinical lung cancer specimens. Knockdown of AMOT in a low metastatic CL1-0 lung cancer cell line initiated cancer proliferation, migration, invasion and epithelial-mesenchymal transition. The trigger of cancer progression caused by AMOT loss was transduced by decreased cytoplasmic sequestration and increased nuclear translocation of oncogenic co-activators YAP/TAZ, leading to increased expression of the growth factor, Cyr61. Tumor promotion by AMOT knockdown was reversed when YAP/TAZ or Cyr61 was absent. Further, AMOT knockdown increased the growth and spread of Lewis lung carcinoma in vivo. These findings suggest that AMOT is a crucial suppressor of lung cancer metastasis and highlight its critical role as a tumor suppressor and its potential as a prognostic biomarker and therapeutic target for lung cancer.

NEDD9 is an established marker of invasive and metastatic cancers. NEDD9 downregulation has been shown to dramatically reduce cell invasion and metastasis in multiple tumors. The mechanisms by which NEDD9 regulates invasion are largely unknown. In the current study, we have found that NEDD9 is required for matrix metalloproteinase 14 (MMP14) enzymatic recovery/recycling through the late endosomes to enable disengagement of tissue inhibitor of matrix metalloproteinase 2 (TIMP2) and tumor invasion. Depletion of NEDD9 decreases targeting of the MMP14/TIMP2 complex to late endosomes and increases trafficking of MMP14 from early/sorting endosomes back to the surface in a small GTPase ADP ribosylation factor-6 (Arf6)-dependent manner. NEDD9 directly binds to Arf6-GTPase-activating protein, ARAP3 and Arf6-effector GGA3, thereby facilitating the Arf6 inactivation required for MMP14/TIMP2 targeting to late endosomes. Re-expression of NEDD9 or a decrease in Arf6 activity is sufficient to restore MMP14 activity and the invasive properties of tumor cells. Importantly, NEDD9 inhibition by Vivo-Morpholinos, an antisense therapy, decreases primary tumor growth and metastasis in xenograft models of breast cancer. Collectively, our findings uncover a novel mechanism to control tumor-cell dissemination through NEDD9/Arf6-dependent regulation of MMP14/TIMP2 trafficking, and validate NEDD9 as a clinically relevant therapeutic target to treat metastatic cancer.

Scirrhous gastric cancer is frequently associated with peritoneal dissemination, and the interaction of cancer cells with peritoneal mesothelial cells (PMCs) is crucial for the establishment of the metastasis in the peritoneum. Although cells derived from PMCs are detected within tumors of peritoneal carcinomatosis, how PMCs are incorporated into tumor architecture is not understood. The present study shows that PMCs create the invasion front of peritoneal carcinomatosis, which depends on activation of Tks5 in PMCs. In peritoneal tumor implants, PMCs represent majority of cells located at the invasive edge of the cancer tissue. Exogenously implanted PMCs and host PMCs aggressively invade into abdominal wall upon the peritoneal inoculation of cancer cells, and PMCs locate ahead of cancer cells in the direction of invasion. Tks5, a substrate of Src kinase, is predominantly expressed in the PMCs of cancer tissue, and promotes the invasion of PMCs and cancer cells. Expression and activation of Tks5 was induced in PMCs following their exposure to gastric cancer cells, and increased Tks5 expression was detected in PMCs located at the invasion front. Reduced Tks5 expression in PMCs blocked PMC invasion, which in turn prevents cancer cell invasion both in vitro and in vivo. The peritoneal dissemination of gastric cancer was significantly increased by mixing cancer cells and PMCs, and was suppressed by knockdown of Tks5 in PMCs. These results suggest that cancer-activated PMCs create invasion front by guiding cancer cells. Signaling leading to Tks5 activation in PMCs may be a suitable therapeutic target for prevention of peritoneal carcinomatosis.

The Crk SH2/SH3 adaptor and the Abl nonreceptor tyrosine kinase were first identified as oncoproteins, and both can induce tumorigenesis when overexpressed or mutationally activated. We previously reported the surprising finding that inhibition or knockdown of Abl family kinases enhanced transformation of mouse fibroblasts by CrkI. Abl family inhibitors are currently used or are being tested for treatment of human malignancies, and our finding raised concerns that such inhibitors might actually promote the growth of tumors overexpressing CrkI. Here, we identify the Dok1 adaptor as the key effector for the enhancement of CrkI transformation by Abl inhibition. We show that phosphorylation of tyrosines 295 and 361 of Dok1 by Abl family kinases suppresses CrkI transforming activity, and that upon phosphorylation these tyrosines bind the SH2 domains of the Ras inhibitor p120 RasGAP. Knockdown of RasGAP resulted in a similar enhancement of CrkI transformation, consistent with a critical role for Ras activity. Imaging studies using a FRET sensor of Ras activation revealed alterations in the localization of activated Ras in CrkI-transformed cells. Our results support a model in which Dok1 phosphorylation normally suppresses localized Ras pathway activity in Crk-transformed cells via recruitment and/or activation of RasGAP, and that preventing this negative feedback mechanism by inhibiting Abl family kinases leads to enhanced transformation by Crk.