Hippo Pathway in Cancer: Aberrant Regulation and Therapeutic Opportunities

Increased ACTL6A occupancy within mSWI/SNF chromatin remodelers drives human squamous cell carcinoma

Mammalian SWI/SNF (BAF) chromatin remodelers play dosage-sensitive roles in many human malignancies and neurologic disorders. The gene encoding the BAF subunit actin-like 6a (ACTL6A) is amplified early in the development of many squamous cell carcinomas (SCCs), but its oncogenic role remains unclear. Here we demonstrate that ACTL6A overexpression leads to its stoichiometric assembly into BAF complexes and drives their interaction and engagement with specific regulatory regions in the genome. In normal epithelial cells, ACTL6A was substoichiometric to other BAF subunits. However, increased ACTL6A levels by ectopic expression or in SCC cells led to near saturation of ACTL6A within BAF complexes. Increased ACTL6A occupancy enhanced polycomb opposition genome-wide to activate SCC genes and facilitated the co-dependent loading of BAF and TEAD-YAP complexes on chromatin. Both mechanisms appeared to be critical and function as a molecular AND gate for SCC initiation and maintenance, thereby explaining the specificity of the role of ACTL6A amplification in SCCs.

The Hippo Signaling Pathway in Cancer: A Cell Cycle Perspective

Simple Summary

Cancer is increasingly viewed as a cell cycle disease in that the dysregulation of the cell cycle machinery is a common feature in cancer. The Hippo signaling pathway consists of a core kinase cascade as well as extended regulators, which together control organ size and tissue homeostasis. The aberrant expression of cell cycle regulators and/or Hippo pathway components contributes to cancer development, and for this reason, we specifically focus on delineating the roles of the Hippo pathway in the cell cycle. Improving our understanding of the Hippo pathway from a cell cycle perspective could be used as a powerful weapon in the cancer battlefield.

Abstract

Cell cycle progression is an elaborate process that requires stringent control for normal cellular function. Defects in cell cycle control, however, contribute to genomic instability and have become a characteristic phenomenon in cancers. Over the years, advancement in the understanding of disrupted cell cycle regulation in tumors has led to the development of powerful anti-cancer drugs. Therefore, an in-depth exploration of cell cycle dysregulation in cancers could provide therapeutic avenues for cancer treatment. The Hippo pathway is an evolutionarily conserved regulator network that controls organ size, and its dysregulation is implicated in various types of cancers. Although the role of the Hippo pathway in oncogenesis has been widely investigated, its role in cell cycle regulation has not been comprehensively scrutinized. Here, we specifically focus on delineating the involvement of the Hippo pathway in cell cycle regulation. To that end, we first compare the structural as well as functional conservation of the core Hippo pathway in yeasts, flies, and mammals. Then, we detail the multi-faceted aspects in which the core components of the mammalian Hippo pathway and their regulators affect the cell cycle, particularly with regard to the regulation of E2F activity, the G1 tetraploidy checkpoint, DNA synthesis, DNA damage checkpoint, centrosome dynamics, and mitosis. Finally, we briefly discuss how a collective understanding of cell cycle regulation and the Hippo pathway could be weaponized in combating cancer.

Molecular Mechanisms of Ferroptosis and Its Roles in Hematologic Malignancies

Cell death is essential for the normal metabolism of human organisms. Ferroptosis is a unique regulated cell death (RCD) mode characterized by excess accumulation of iron-dependent lipid peroxide and reactive oxygen species (ROS) compared with other well-known programmed cell death modes. It has been currently recognized that ferroptosis plays a rather important role in the occurrence, development, and treatment of traumatic brain injury, stroke, acute kidney injury, liver damage, ischemia–reperfusion injury, tumor, etc. Of note, ferroptosis may be explained by the expression of various molecules and signaling components, among which iron, lipid, and amino acid metabolism are the key regulatory mechanisms of ferroptosis. Meanwhile, tumor cells of hematological malignancies, such as leukemia, lymphoma, and multiple myeloma (MM), are identified to be sensitive to ferroptosis. Targeting potential regulatory factors in the ferroptosis pathway may promote or inhibit the disease progression of these malignancies. In this review, a systematic summary was conducted on the key molecular mechanisms of ferroptosis and the current potential relationships of ferroptosis with leukemia, lymphoma, and MM. It is expected to provide novel potential therapeutic approaches and targets for hematological malignancies.

NGF Signaling Interacts With the Hippo/YAP Pathway to Regulate Cervical Cancer Progression

Nerve growth factor (NGF) is increasingly implicated in cervical cancer progression, but its mechanism in cervical cancer is unclear. Here, studies demonstrate that NGF inhibits the Hippo signaling pathway and activates Yes-associated protein (YAP) to induce cervical cancer cell proliferation and migration. Our results suggested that stimulation of NGF promoted cell growth and migration and activated YAP in HeLa and C-33A cell lines. The expression of YAP target genes (CTGF and ANKRD1) was upregulated after NGF treatment. The NGF inhibitor Ro 08-2750 and siRNA-mediated NGF receptor gene silencing suppressed HeLa and C-33A cells proliferation and migration, activated large suppressor kinase 1 (LATS1) kinase activity, and suppressed YAP function. In addition, the expression of YAP target genes (CTGF and ANKRD1) was suppressed by Ro 08-2750 treatment in HeLa and C-33A cells. Interestingly, proliferation was significantly higher in NGF-treated cells than in control cells, and this effect was completely reversed by the YAP small molecule inhibitor-verteporfin. Furthermore, the mouse xenograft model shows that NGF regulates YAP oncogenic activity in vivo. Mechanistically, NGF stimulation inactivates LATS1 and activates YAP, and NGF inhibition was found to induce large suppressor kinase 1 (LATS1) phosphorylation. Taken together, these data provide the first direct evidence of crosstalk between the NGF signaling and Hippo cancer pathways, an interaction that affects cervical cancer progression. Our study indicates that combined targeting of the NGF signaling and the Hippo pathway represents a novel therapeutic strategy for treatment of cervical cancer.

SMARCA4 Depletion Induces Cisplatin Resistance by Activating YAP1-Mediated Epithelial-to-Mesenchymal Transition in Triple-Negative Breast Cancer

Simple Summary

SMARCA4 mutations were over-representative in cisplatin resistance and metastatic triple-negative breast cancer (TNBC). Additionally, SMARCA4 inactivation induced the mesenchymal-like subtype TNBC. The epithelial-to-mesenchymal transition and Hippo-YAP/TAZ pathways were activated in SMARCA4 inactivation samples of both SMARCA4 knockout cell lines and TNBC patients. In SMARCA4 knockout cells, the YAP1 inhibitor verteporfin suppressed YAP1 target genes. This study depicts the clinical importance of SMARCA4 depletion in TNBC and suggests YAP/TAZ as a novel target for cisplatin-resistant patients.

Abstract

The role of SMARCA4, an ATPase subunit of the SWI/SNF chromatin remodeling complex, in genomic organization is well studied in various cancer types. However, its oncogenic role and therapeutic implications are relatively unknown in triple-negative breast cancer (TNBC). We investigated the clinical implication and downstream regulation induced by SMARCA4 inactivation using large-scale genome and transcriptome profiles. Additionally, SMARCA4 was knocked out in MDA-MB-468 and MDA-MB-231 using CRISPR/Cas9 to identify gene regulation and a targetable pathway. First, we observed an increase in SMARCA4 mutations in cisplatin resistance and metastasis in TNBC patients. Its inactivation was associated with the mesenchymal-like (MSL) subtype. Gene expression analysis showed that the epithelial-to-mesenchymal transition (EMT) pathway was activated in SMARCA4-deficient patients. Next, the Hippo pathway was activated in the SMARCA4 inactivation group, as evidenced by the higher CTNNB1, TGF-β, and YAP1 oncogene signature scores. In SMARCA4 knockout cells, EMT was upregulated, and the cell line transcriptome changed from the SL to the MSL subtype. SMARCA4 knockout cells showed cisplatin resistance and Hippo-YAP/TAZ target gene activation. The YAP1 inhibitor verteporfin suppressed the expression of YAP1 target genes, and decreased cell viability and invasiveness on SMARCA4 knockout cells. SMARCA4 inactivation in TNBC endowed the resistance to cisplatin via EMT activation. The YAP1 inhibitor could become a novel strategy for patients with SMARCA4-inactivated TNBC.

Evaluation of Diagnostic Potential of Epigenetically Deregulated MiRNAs in Epithelial Ovarian Cancer

Background

Epithelial ovarian cancer (EOC) is one of the most lethal gynecological malignancies among women worldwide. Early diagnosis of EOC could help in ovarian cancer management. MicroRNAs, a class of small non-coding RNA molecules, are known to be involved in post-transcriptional regulation of ~60% of human genes. Aberrantly expressed miRNAs associated with disease progression are confined in lipid or lipoprotein and secreted as extracellular miRNA in body fluid such as plasma, serum, and urine. MiRNAs are stably present in the circulation and recently have gained an importance to serve as a minimally invasive biomarker for early detection of epithelial ovarian cancer.

Methods

Genome-wide methylation pattern of six EOC and two normal ovarian tissue samples revealed differential methylation regions of miRNA gene promoter through MeDIP-NGS sequencing. Based on log2FC and p-value, three hypomethylated miRNAs (miR-205, miR-200c, and miR-141) known to have a potential role in ovarian cancer progression were selected for expression analysis through qRT-PCR. The expression of selected miRNAs was analyzed in 115 tissue (85 EOC, 30 normal) and 65 matched serum (51 EOC and 14 normal) samples.

Results

All three miRNAs (miR-205, miR-200c, and miR-141) showed significantly higher expression in both tissue and serum cohorts when compared with normal controls (p < 0.0001). The receiver operating characteristic curve analysis of miR-205, miR-200c, and miR-141 has area under the curve (AUC) values of 87.6 (p < 0.0001), 78.2 (p < 0.0001), and 86.0 (p < 0.0001), respectively; in advance-stage serum samples, however, ROC has AUC values of 88.1 (p < 0.0001), 78.9 (p < 0.0001), and 86.7 (p < 0.0001), respectively, in early-stage serum samples. The combined diagnostic potential of the three miRNAs in advance-stage serum samples and early-stage serum samples has AUC values of 95.9 (95% CI: 0.925-1.012; sensitivity = 96.6% and specificity = 80.0%) and 98.1 (95% CI: 0.941-1.021; sensitivity = 90.5% and specificity = 100%), respectively.

Conclusion

Our data correlate the epigenetic deregulation of the miRNA genes with their expression. In addition, the miRNA panel (miR-205 + miR-200c + miR-141) has a much higher AUC, sensitivity, and specificity to predict EOC at an early stage in both tissue and serum samples.

Silencing of NACC1 inhibits the proliferation, migration and invasion of nasopharyngeal carcinoma cells via regulating the AKT/mTOR signaling pathway

Nucleus accumbens-associated protein 1 (NACC1) has been reported to serve as an oncogenic role in several types of cancer; however, its role in nasopharyngeal carcinoma (NPC) remains to be determined. The present study aimed to investigate the role of NACC1 in NPC and elucidate the underlying mechanisms. Therefore, NACC1 expression in the normal nasopharyngeal epithelial cell line, NP69, and various NPC cell lines was determined by reverse transcription-quantitative PCR and western blot analyses. NACC1 expression was silenced in the NPC SUNE-1 cell line by transfection with a short hairpin RNA. Cell viability, proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) were then evaluated using MTT, colony formation, wound healing, Transwell and western blot assays, respectively. SC79 was employed to activate AKT expression in NACC1-silenced SUNE-1 cells, and the aforementioned cellular processes were observed. The results revealed that NACC1 expression was upregulated in NPC cell lines. NACC1-knocdown inhibited SUNE-1 cell proliferation, migration, invasion and EMT. Moreover, the levels of phosphorylated AKT and mTOR were decreased upon NACC1 silencing. Mechanistically, the presence of SC79 significantly blocked all the effects of NACC1-knockdown on SUNE-1 cells. The findings of the present study demonstrated that NACC1-knockdown effectively suppressed NPC cell proliferation, migration and invasion by inhibiting the activation of the AKT/mTOR signaling pathway. NACC1 may thus serve as a potential target for the diagnosis and therapy of NPC.

LncRNAs in the Regulation of Genes and Signaling Pathways through miRNA-Mediated and Other Mechanisms in Clear Cell Renal Cell Carcinoma

The fundamental novelty in the pathogenesis of renal cell carcinoma (RCC) was discovered as a result of the recent identification of the role of long non-coding RNAs (lncRNAs). Here, we discuss several mechanisms for the dysregulation of the expression of protein-coding genes initiated by lncRNAs in the most common and aggressive type of kidney cancer-clear cell RCC (ccRCC). A model of competitive endogenous RNA (ceRNA) is considered, in which lncRNA acts on genes through the lncRNA/miRNA/mRNA axis. For the most studied oncogenic lncRNAs, such as HOTAIR, MALAT1, and TUG1, several regulatory axes were identified in ccRCC, demonstrating a number of sites for various miRNAs. Interestingly, the LINC00973/miR-7109/Siglec-15 axis represents a novel agent that can suppress the immune response in patients with ccRCC, serving as a valuable target in addition to the PD1/PD-L1 pathway. Other mechanisms of action of lncRNAs in ccRCC, involving direct binding with proteins, mRNAs, and genes/DNA, are also considered. Our review briefly highlights methods by which various mechanisms of action of lncRNAs were verified. We pay special attention to protein targets and signaling pathways with which lncRNAs are associated in ccRCC. Thus, these new data on the different mechanisms of lncRNA functioning provide a novel basis for understanding the pathogenesis of ccRCC and the identification of new prognostic markers and targets for therapy.

Long noncoding RNAs: fine-tuners hidden in the cancer signaling network

With the development of sequencing technology, a large number of long non-coding RNAs (lncRNAs) have been identified in addition to coding genes. LncRNAs, originally considered as junk RNA, are dysregulated in various types of cancer. Although protein-coding signaling pathways underlie various biological activities, and abnormal signal transduction is a key trigger and indicator for tumorigenesis and cancer progression, lncRNAs are sparking keen interest due to their versatile roles in fine-tuning signaling pathways. We are just beginning to scratch the surface of lncRNAs. Therefore, despite the fact that lncRNAs drive malignant phenotypes from multiple perspectives, in this review, we focus on important signaling pathways modulated by lncRNAs in cancer to demonstrate an up-to-date understanding of this emerging field.

Recent Therapeutic Approaches to Modulate the Hippo Pathway in Oncology and Regenerative Medicine

The Hippo pathway is an evolutionary conserved signaling network that regulates essential processes such as organ size, cell proliferation, migration, stemness and apoptosis. Alterations in this pathway are commonly found in solid tumors and can lead to hyperproliferation, resistance to chemotherapy, compensation for mKRAS and tumor immune evasion. As the terminal effectors of the Hippo pathway, the transcriptional coactivators YAP1/TAZ and the transcription factors TEAD1–4 present exciting opportunities to pharmacologically modulate the Hippo biology in cancer settings, inflammation and regenerative medicine. This review will provide an overview of the progress and current strategies to directly and indirectly target the YAP1/TAZ protein–protein interaction (PPI) with TEAD1–4 across multiple modalities, with focus on recent small molecules able to selectively bind to TEAD, block its autopalmitoylation and inhibit YAP1/TAZ–TEAD-dependent transcription in cancer.

Co-expression of YAP and TAZ associates with chromosomal instability in human cholangiocarcinoma

Background

Activation of the oncogene yes-associated protein (YAP) is frequently detected in intrahepatic cholangiocarcinoma (iCCA); however, the expression pattern and the functional impact of its paralogue WW domain-containing transcription regulator 1 (WWTR1; synonym: TAZ) are not well described in different CCA subtypes.

Methods

Immunohistochemical analysis of YAP and TAZ in iCCA and extrahepatic CCA (eCCA) cohorts was performed. YAP/TAZ shuttling and their functional impact on CCA cell lines were investigated. Target genes expression after combined YAP/TAZ inhibition was analyzed.

Results

Immunohistochemical analysis of iCCA and eCCA revealed YAP or TAZ positivity in up to 49.2%; however, oncogene co-expression was less frequent (up to 23%). In contrast, both proteins were jointly detectable in most CCA cell lines and showed nuclear/cytoplasmic shuttling in a cell density-dependent manner. Next to the pro-proliferative function of YAP/TAZ, both transcriptional co-activators cooperated in the regulation of a gene signature that indicated the presence of chromosomal instability (CIN). A correlation between YAP and the CIN marker phospho-H2A histone family member X (pH2AX) was particularly observed in tissues from iCCA and distal CCA (dCCA). The presence of the CIN genes in about 25% of iCCA was statistically associated with worse prognosis.

Conclusions

YAP and TAZ activation is not uncoupled from cell density in CCA cells and both factors cooperatively contribute to proliferation and expression of CIN-associated genes. The corresponding group of CCA patients is characterized by CIN and may benefit from YAP/TAZ-directed therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08794-5.

Targeting-YAP/TAZ therapies for head and neck cancer, directly or indirectly?

YAP/TAZ are wild over-activated in head and neck squamous cell carcinoma (HNSCC) with high potential as a direct therapy target for HNSCC treatments. However, the efforts on the directly targeting-YAP/TAZ therapies over the past decade, have very limited impacts, mainly caused by: 1. There is still none effective and specific YAP/TAZ inhibitor with clinical potential; 2. YAP/TAZ might not be directly targeted, because of their multiple important biological functions, such as: regulation of cell proliferation and survival, stem cell maintain, regulation of organ development, organ size control, and tissue regeneration. Interestingly, the over-activation of YAP/TAZ in HNSCC mainly be regulated by upstream abnormal molecular or biological events, instead of genes alteration of YAP/TAZ. Therefore, exploring the alternative molecular events regulating YAP/TAZ activation and molecular mechanism in HNSCC might help to uncover novel indirect targets of YAP/TAZ therapies for HNSCC prevention and treatment.

P4HA2-induced prolyl hydroxylation suppresses YAP1-mediated prostate cancer cell migration, invasion, and metastasis

Yes-associated protein 1 (YAP1), a key player in the Hippo pathway, has been shown to play a critical role in tumor progression. However, the role of YAP1 in prostate cancer cell invasion, migration, and metastasis is not well defined. Through functional, transcriptomic, epigenomic, and proteomic analyses, we showed that prolyl hydroxylation of YAP1 plays a critical role in the suppression of cell migration, invasion, and metastasis in prostate cancer. Knockdown (KD) or knockout (KO) of YAP1 led to an increase in cell migration, invasion, and metastasis in prostate cancer cells. Microarray analysis showed that the EMT pathway was activated in Yap1-KD cells. ChIP-seq analysis showed that YAP1 target genes are enriched in pathways regulating cell migration. Mass spectrometry analysis identified P4H prolyl hydroxylase in the YAP1 complex and YAP1 was hydroxylated at multiple proline residues. Proline-to-alanine mutations of YAP1 isoform 3 identified proline 174 as a critical residue, and its hydroxylation suppressed cell migration, invasion, and metastasis. KO of P4ha2 led to an increase in cell migration and invasion, which was reversed upon Yap1 KD. Our study identified a novel regulatory mechanism of YAP1 by which P4HA2-dependent prolyl hydroxylation of YAP1 determines its transcriptional activities and its function in prostate cancer metastasis.

Long non-coding RNA LOC107985656 represses the proliferation of hepatocellular carcinoma cells through activation of the tumor-suppressive Hippo pathway

Long non-coding RNAs (lncRNAs) play important regulatory roles in hepatocellular carcinoma (HCC). However, the function of LOC107985656 in HCC progression remains unclear. The lncRNA, mRNA and miRNA levels in HCC tissues or cells were measured using real-time quantitative polymerase chain reaction (RT-qPCR). The proliferation of cancer cells was evaluated using 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) viability and colony formation assays. Bioinformatics prediction, dual luciferase assay and RNA pull-down assay were performed to analyze the relationships between LOC107985656 and miR-106b-5p, or miR-106b-5p and large tumor suppressor 1 (LATS1). The protein expression levels were detected using Western blot. Results showed that LncRNA LOC107985656 was downregulated in HCC tissues and cells. Upregulation of LOC107985656 inhibited the proliferation of HCC cells, whereas its knockdown promoted this phenomenon. LOC107985656 could activate the tumor-suppressive Hippo pathway by repressing yes association protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) (two homologs of Yki) protein expression in HCC. Further investigation suggested that LOC107985656 regulated the expression of LATS1 by acting as a sponge for absorbing miR-106b-5p in HCC cells. In conclusion, this study unraveled the role of LOC107985656 following a ceRNA (competing endogenous RNAs) mechanism for the miR-106b-5p/LATS1 axis in HCC. The results indicate potential diagnostic and therapeutic applications of LOC107985656 in HCC.

Abbreviations:

HCC: hepatocellular carcinoma; LncRNA: long non-coding RNA; LATS1: large tumor suppressor 1; MTT: 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide; YAP: yes association protein; WWTR1: WW domain-containing transcription regulator protein 1; cDNA: single‐stranded complementary DNA; RT-qPCR: real-time quantitative polymerase chain reaction; Radio-Immunoprecipitation Assay (RIPA); BCA: bicinchoninic acid; ASO: antisense oligonucleotide; MST1/2: Ste20-like kinases 1/2; TEAD: TEA domain transcription factor; ceRNA: competing endogenous RNAs.

The anticarcinogenic and anticancer effects of the dietary flavonoid, morin: Current status, challenges, and future perspectives

Flavonoids constitute one of the most important classes of polyphenols, which have been found to have a wide range of biological activities such as anticancer effects. A large body of evidence demonstrates that morin as a pleiotropic dietary flavonoid possesses potent anticarcinogenic and anticancer activities with minimal toxicity against normal cells. The present review comprehensively elaborates the molecular mechanisms underlying antitumorigenic and anticancer effects of morin. Morin exerts its anticarcinogenic effects through multiple cancer preventive mechanisms, including reduction of oxidative stress, activation of phase II enzymes, induction of apoptosis, attenuation of inflammatory mediators, and downregulation of p-Akt and NF-κB expression. A variety of molecular targets and signaling pathways such as apoptosis, cell cycle, reactive oxygen species (ROS), matrix metalloproteinases (MMPs), epithelial-mesenchymal transition (EMT), and microRNAs (miRNAs) as well as signal transducer and activator of transcription 3 (STAT3), NF-κB, phosphatidylinositol 3-kinase (PI3K)/Akt, mitogen-activated protein kinase (MAPK), and Hippo pathways have been found to be involved in the anticancer effects of morin. In the adjuvant therapy, morin has been shown to have synergistic anticancer effects with several chemotherapeutic drugs. The findings of this review indicate that morin can act as a promising chemopreventive and chemotherapeutic agent.

Systematic identification of novel cancer genes through analysis of deep shRNA perturbation screens

Systematic perturbation screens provide comprehensive resources for the elucidation of cancer driver genes. The perturbation of many genes in relatively few cell lines in such functional screens necessitates the development of specialized computational tools with sufficient statistical power. Here we developed APSiC (Analysis of Perturbation Screens for identifying novel Cancer genes) to identify genetic drivers and effectors in perturbation screens even with few samples. Applying APSiC to the shRNA screen Project DRIVE, APSiC identified well-known and novel putative mutational and amplified cancer genes across all cancer types and in specific cancer types. Additionally, APSiC discovered tumor-promoting and tumor-suppressive effectors, respectively, for individual cancer types, including genes involved in cell cycle control, Wnt/β-catenin and hippo signalling pathways. We functionally demonstrated that LRRC4B, a putative novel tumor-suppressive effector, suppresses proliferation by delaying cell cycle and modulates apoptosis in breast cancer. We demonstrate APSiC is a robust statistical framework for discovery of novel cancer genes through analysis of large-scale perturbation screens. The analysis of DRIVE using APSiC is provided as a web portal and represents a valuable resource for the discovery of novel cancer genes.

Cytoskeleton-associated protein 4 (CKAP4) promotes malignant progression of human gliomas through inhibition of the Hippo signaling pathway

PURPOSE

Gliomas are the most common and aggressive malignant brain tumors and are associated with high mortality and incidence in humans. Despite rigorous multi-modal therapy, including surgery, chemotherapy and radiotherapy, patients with malignant glioma survive an average of 12-15 months following primary diagnosis. Therefore, new molecular biomarkers are urgently needed for diagnosis and targeted therapy. Here, we find that suppression of CKAP4 might inhibit glioma growth through regulation of Hippo signaling.

METHODS

We examined the expression levels of CKAP4 through analysis of RNA sequencing data from GEPIA and CGGA databases. Then, Lentivirus was used to construct stable cell lines with knockout or overexpression of CKAP4. Next, the function of CKAP4 on glioma was investigated in vitro and in an orthotopic brain tumor model in mice. Lastly, luciferase reporter assay, immunofluorescence and immunoblotting were performed to explore the potential mechanism of how CKAP4 affects gliomas.

RESULTS

CKAP4 is highly upregulated in glioma and high CKAP4 expressing tumors were associated with poor patient survival. And CKAP4 promotes malignant progression of gliomas via inhibiting Hippo signaling.

CONCLUSION

CKAP4 has potential as a promising biomarker and can predict the prognosis of patients with gliomas. And targeting CKAP4 expression may be an effective therapeutic strategy for the treatment of human gliomas.

Hypertranscription and replication stress in cancer

Replication stress results from obstacles to replication fork progression, including ongoing transcription, which can cause transcription-replication conflicts. Oncogenic signaling can promote global increases in transcription activity, also termed hypertranscription. Despite the widely accepted importance of oncogene-induced hypertranscription, its study remains neglected compared with other causes of replication stress and genomic instability in cancer. A growing number of recent studies are reporting that oncogenes, such as RAS, and targeted cancer treatments, such as bromodomain and extraterminal motif (BET) bromodomain inhibitors, increase global transcription, leading to R-loop accumulation, transcription-replication conflicts, and the activation of replication stress responses. Here we discuss our mechanistic understanding of hypertranscription-induced replication stress and the resulting cellular responses, in the context of oncogenes and targeted cancer therapies.

Emerging treatment modalities for systemic therapy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has long been a major global clinical problem as one of the most common malignant tumours with a high rate of recurrence and mortality. Although potentially curative therapies are available for the early and intermediate stages, the treatment of patients with advanced HCC remains to be resolved. Fortunately, the past few years have shown the emergence of successful systemic therapies to treat HCC. At the molecular level, HCC is a heterogeneous disease, and current research on the molecular characteristics of HCC has revealed numerous therapeutic targets. Targeted agents based on signalling molecules have been successfully supported in clinical trials, and molecular targeted therapy has already become a milestone for disease management in patients with HCC. Immunotherapy, a viable approach for the treatment of HCC, recognizes the antigens expressed by the tumour and treats the tumour using the immune system of the host, making it both selective and specific. In addition, the pipeline for HCC is evolving towards combination therapies with promising clinical outcomes. More drugs designed to focus on specific pathways and immune checkpoints are being developed in the clinic. It has been demonstrated that some drugs can improve the prognosis of patients with HCC in first- or second-line settings, and these drugs have been approved by the Food and Drug Administration or are nearing approval. This review describes targeting pathways and systemic treatment strategies in HCC and summarizes effective targeted and immune-based drugs for patients with HCC and the problems encountered.

Iminodibenzyl redirected cyclooxygenase-2 catalyzed dihomo-γ-linolenic acid peroxidation pattern in lung cancer

Cyclooxygenase-2 (COX-2) is up-regulated by redox imbalance and is considered a target for cancer therapy. The rationale of the COX-2 inhibitor lies in suppressing COX-2 catalyzed peroxidation of omega-6 polyunsaturated fatty acids (PUFAs), which are essential and pervasive in our daily diet. However, COX-2 inhibitors fail to improve cancer patients' survival and may lead to severe side effects. Here, instead of directly inhibiting COX-2, we utilize a small molecule, iminodibenzyl, which could reprogram the COX-2 catalyzed omega-6 PUFAs peroxidation in lung cancer by inhibiting delta-5-desaturase (D5D) activity. Iminodibenzyl breaks the conversion from dihomo-γ-linolenic acid (DGLA) to arachidonic acid, resulting in the formation of a distinct byproduct, 8-hydroxyoctanoic acid, in lung cancer cells and solid tumors. By utilizing COX-2 overexpression in cancer, the combination of DGLA supplementation and iminodibenzyl suppressed YAP1/TAZ pathway, decreasing the tumor size and lung metastasis in nude mice and C57BL/6 mice. This D5D inhibition-based strategy selectively damaged lung cancer cells with a high COX-2 level, whereas it could avoid harassing normal lung epithelial cells. This finding challenged the COX-2 redox basis in cancer, providing a new direction for developing omega-6 (DGLA)-based diet/regimen in lung cancer therapy.

Modulation of serine/threonine-protein phosphatase 1 (PP1) complexes: A promising approach in cancer treatment

Cancer is the second leading cause of death worldwide. Despite the availability of numerous therapeutic options, tumor heterogeneity and chemoresistance have limited the success of these treatments, and the development of effective anticancer therapies remains a major focus in oncology research. The serine/threonine-protein phosphatase 1 (PP1) and its complexes have been recognized as potential drug targets. Research on the modulation of PP1 complexes is currently at an early stage, but has immense potential. Chemically diverse compounds have been developed to disrupt or stabilize different PP1 complexes in various cancer types, with the objective of inhibiting disease progression. Beneficial results obtained in vitro now require further pre-clinical and clinical validation. In conclusion, the modulation of PP1 complexes seems to be a promising, albeit challenging, therapeutic strategy for cancer.

Emerging Perspectives on Leukemia Inhibitory Factor and its Receptor in Cancer

Tumorigenesis and metastasis have deep connections to inflammation and inflammatory cytokines, but the mechanisms underlying these relationships are poorly understood. Leukemia Inhibitory Factor (LIF) and its receptor (LIFR), part of the interleukin-6 (IL-6) cytokine family, make up one such ill-defined piece of the puzzle connecting inflammation to cancer. Although other members of the IL-6 family have been shown to be involved in the metastasis of multiple types of cancer, the role of LIF and LIFR has been challenging to determine. Described by others in the past as enigmatic and paradoxical, LIF and LIFR are expressed in a diverse array of cells in the body, and the narrative surrounding them in cancer-related processes has been vague, and at times even contradictory. Despite this, recent insights into their functional roles in cancer have highlighted interesting patterns that may allude to a broader understanding of LIF and LIFR within tumor growth and metastasis. This review will discuss in depth the signaling pathways activated by LIF and LIFR specifically in the context of cancer-the purpose being to summarize recent literature concerning the downstream effects of LIF/LIFR signaling in a variety of cancer-related circumstances in an effort to begin teasing out the intricate web of contradictions that have made this pair so challenging to define.

The role of the Hippo pathway in heart disease

Heart disease, including coronary artery disease, myocardial infarction, heart failure, cardiac hypertrophy, and cardiomyopathies, is the leading causes of death worldwide. The Hippo pathway is a central controller for organ size and tissue growth, which plays a pivotal role in determining cardiomyocytes and nonmyocytes proliferation, regeneration, differentiation, and apoptosis. In this review, we summarize the effects of the Hippo pathway on heart disease and propose potential intervention targets. Especially, we discuss the molecular mechanisms of the Hippo pathway involved in maintaining cardiac homeostasis by regulating cardiomyocytes and nonmyocytes function in the heart. Based on this, we conclude that the Hippo pathway is a promising therapeutic target for cardiovascular therapy, which will bring new perspectives for their treatments.

TEAD family transcription factors in development and disease

The balance between stem cell potency and lineage specification entails the integration of both extrinsic and intrinsic cues, which ultimately influence gene expression through the activity of transcription factors. One example of this is provided by the Hippo signalling pathway, which plays a central role in regulating organ size during development. Hippo pathway activity is mediated by the transcriptional co-factors Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), which interact with TEA domain (TEAD) proteins to regulate gene expression. Although the roles of YAP and TAZ have been intensively studied, the roles played by TEAD proteins are less well understood. Recent studies have begun to address this, revealing that TEADs regulate the balance between progenitor self-renewal and differentiation throughout various stages of development. Furthermore, it is becoming apparent that TEAD proteins interact with other co-factors that influence stem cell biology. This Primer provides an overview of the role of TEAD proteins during development, focusing on their role in Hippo signalling as well as within other developmental, homeostatic and disease contexts.

In vivo genome-wide CRISPR screen reveals breast cancer vulnerabilities and synergistic mTOR/Hippo targeted combination therapy

Triple negative breast cancer (TNBC) patients exhibit poor survival outcomes and lack effective targeted therapies. Using unbiased in vivo genome-wide CRISPR screening, we interrogated cancer vulnerabilities in TNBC and identified an interplay between oncogenic and tumor suppressor pathways. This study reveals tumor regulatory functions for essential components of the mTOR and Hippo pathways in TNBC. Using in vitro drug matrix synergy models and in vivo patient-derived xenografts, we further establish the therapeutic relevance of our findings and show that pharmacological inhibition of mTORC1/2 and oncoprotein YAP efficiently reduces tumorigenesis in TNBC. At the molecular level, we find that while verteporfin-induced YAP inhibition leads to apoptosis, torin1-mediated mTORC1/2 inhibition promotes macropinocytosis. Torin1-induced macropinocytosis further facilitates verteporfin uptake, thereby greatly enhancing its pro-apoptotic effects in cancer cells. Overall, our study underscores the power and robustness of in vivo CRISPR genome-wide screens in identifying clinically relevant and innovative therapeutic modalities in cancer.

Triple negative breast cancer (TNBC) lack effective therapies. Here, through an in vivo genome-wide CRISPR screen in TNBCs, the authors identify tumorigenic functions for components of the mTORC1/2 complex and of the YAP/Hippo pathway, and demonstrate that pharmacological inhibition of mTOR and YAP reduces tumour growth in vivo.

The Use of Antihypertensive Drugs as Coadjuvant Therapy in Cancer

Cancer is a complex group of diseases that constitute the second largest cause of mortality worldwide. The development of new drugs for treating this disease is a long and costly process, from the discovery of the molecule through testing in phase III clinical trials, a process during which most candidate molecules fail. The use of drugs currently employed for the management of other diseases (drug repurposing) represents an alternative for developing new medical treatments. Repurposing existing drugs is, in principle, cheaper and faster than developing new drugs. Antihypertensive drugs, primarily belonging to the pharmacological categories of angiotensin-converting enzyme inhibitors, angiotensin II receptors, direct aldosterone antagonists, β-blockers and calcium channel blockers, are commonly prescribed and have well-known safety profiles. Additionally, some of these drugs have exhibited pharmacological properties useful for the treatment of cancer, rendering them candidates for drug repurposing. In this review, we examine the preclinical and clinical evidence for utilizing antihypertensive agents in the treatment of cancer.

Molecular mechanism of cell ferroptosis and research progress in regulation of ferroptosis by noncoding RNAs in tumor cells

Ferroptosis is a newly identified form of nonapoptotic regulated cell death characterized by iron-dependent accumulation of lipid reactive oxygen species. Morphologically and biochemically different from known types of cell death and apoptosis, ferroptosis promotes nervous system diseases, renal failure, ischemia-reperfusion injury, and the treatment of tumors. It could be induced by several mechanisms, including inhibition of glutathione peroxidase 4, lack of cysteine, and peroxidation of polyunsaturated fatty acids, but could be inhibited by iron chelators, lipophilic antioxidants, and some specific inhibitors. Ferroptosis is found to be closely related to the tumorigenesis, invasion, and metastasis of tumors. Noncoding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs), microRNAs, and circular RNAs, do not encode proteins. NcRNAs are found to be capable of regulating the molecular mechanism of ferroptosis in tumor cells post transcription. Ferroptosis provides a new method for cancer treatment. Although several studies have confirmed the important role of ferroptosis in cancer treatment, its specific affecting mechanism is unclear. Here we reviewed the molecular mechanism of ferroptosis in tumor cells and the relationship between ferroptosis and the three important ncRNAs.

Aberrant transcriptional and post-transcriptional regulation of SPAG5, a YAP-TAZ-TEAD downstream effector, fuels breast cancer cell proliferation

Sperm-associated antigen 5 (SPAG5) is an important driver of the cell mitotic spindle required for chromosome segregation and progression into anaphase. SPAG5 has been identified as an important proliferation marker and chemotherapy-sensitivity predictor, especially in estrogen receptor-negative breast cancer subtypes. Here, we report that SPAG5 is a direct target of miR-10b-3p, and its aberrantly high expression associates with poor disease-free survival in two large cohorts of breast cancer patients. SPAG5 depletion strongly impaired cancer cell cycle progression, proliferation, and migration. Interestingly, high expression of SPAG5 pairs with a YAP/TAZ-activated signature in breast cancer patients. Reassuringly, the depletion of YAP, TAZ, and TEAD strongly reduced SPAG5 expression and diminished its oncogenic effects. YAP, TAZ coactivators, and TEAD transcription factors are key components of the Hippo signaling pathway involved in tumor initiation, progression, and metastasis. Furthermore, we report that SPAG5 is a direct transcriptional target of TEAD/YAP/TAZ, and pharmacological targeting of YAP and TAZ severely reduces SPAG5 expression. Collectively, our data uncover an oncogenic feedback loop, comprising miR-10b-3p, SPAG5, and YAP/TAZ/TEAD, which fuels the aberrant proliferation of breast cancer.

New Insights into YES-Associated Protein Signaling Pathways in Hematological Malignancies: Diagnostic and Therapeutic Challenges

Simple Summary

YES-associated protein (YAP) is a co-transcriptional activator that binds to transcriptional factors to increase the rate of transcription of a set of genes, and it can intervene in the onset and progression of different tumors. Most of the data in the literature refer to the effects of the YAP system in solid neoplasms. In this review, we analyze the possibility that YAP can also intervene in hematological neoplasms such as lymphomas, multiple myeloma, and acute and chronic leukemias, modifying the phenomena of cell proliferation and cell death. The possibilities of pharmacological intervention related to the YAP system in an attempt to use its modulation therapeutically are also discussed.

Abstract

The Hippo/YES-associated protein (YAP) signaling pathway is a cell survival and proliferation-control system with its main activity that of regulating cell growth and organ volume. YAP operates as a transcriptional coactivator in regulating the onset, progression, and treatment response in numerous human tumors. Moreover, there is evidence suggesting the involvement of YAP in the control of the hematopoietic system, in physiological conditions rather than in hematological diseases. Nevertheless, several reports have proposed that the effects of YAP in tumor cells are cell-dependent and cell-type-determined, even if YAP usually interrelates with extracellular signaling to stimulate the onset and progression of tumors. In the present review, we report the most recent findings in the literature on the relationship between the YAP system and hematological neoplasms. Moreover, we evaluate the possible therapeutic use of the modulation of the YAP system in the treatment of malignancies. Given the effects of the YAP system in immunosurveillance, tumorigenesis, and chemoresistance, further studies on interactions between the YAP system and hematological malignancies will offer very relevant information for the targeting of these diseases employing YAP modifiers alone or in combination with chemotherapy drugs.

Scanning Protein Surfaces with DNA-Encoded Libraries

Understanding the ligandability of a target protein, defined as the capability of a protein to bind drug-like compounds on any site, can give important stimuli to drug-development projects. For instance, inhibition of protein-protein interactions usually depends on the identification of protein surface binders. DNA-encoded chemical libraries (DELs) allow scanning of protein surfaces with large chemical space. Encoded library selection screens uncovered several protein-protein interaction inhibitors and compounds binding to the surface of G protein-coupled receptors (GPCRs) and kinases. The protein surface-binding chemotypes from DELs are predominantly chemically modified and cyclized peptides, and functional small-molecule peptidomimetics. Peptoid libraries and structural peptidomimetics have been less studied in the DEL field, hinting at hitherto less populated chemical space and suggesting alternative library designs. Roughly a third of bioactive molecules evolved from smaller, target-focused libraries. They showcase the potential of encoded libraries to identify more potent molecules from weak, for example, fragment-like, starting points.

Systemic Therapies for the Management of Non-Clear Cell Renal Cell Carcinoma: What Works, What Doesn't, and What the Future Holds

Non-clear cell renal cell carcinoma (nccRCC) is a broad term that refers to a diverse group of tumors, each with its own distinct biologic and therapeutic profile. The management of nccRCCs is often based on extrapolating data from clinical trials in the more common clear cell renal cell carcinoma, but our emerging prospective and retrospective clinical experience in nccRCC allows us to make more precise recommendations tailored to each histology. The systemic therapy options for metastatic nccRCC include targeted therapies such as tyrosine kinase inhibitors, immune checkpoint inhibitors, and, for specific rare subtypes, cytotoxic chemotherapy. Each nccRCC histology may respond differently to these regimens, which makes accurate pathologic diagnosis imperative. In the present review, we discuss the available clinical and biological data that can help guide systemic therapy recommendations for specific nccRCC subtypes.

MicroRNAs Regulating Hippo-YAP Signaling in Liver Cancer

Liver cancer is one of the most common cancers worldwide, and its prevalence and mortality rate are increasing due to the lack of biomarkers and effective treatments. The Hippo signaling pathway has long been known to control liver size, and genetic depletion of Hippo kinases leads to liver cancer in mice through activation of the downstream effectors yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ). Both YAP and TAZ not only reprogram tumor cells but also alter the tumor microenvironment to exert carcinogenic effects. Therefore, understanding the mechanisms of YAP/TAZ-mediated liver tumorigenesis will help overcome liver cancer. For decades, small noncoding RNAs, microRNAs (miRNAs), have been reported to play critical roles in the pathogenesis of many cancers, including liver cancer. However, the interactions between miRNAs and Hippo-YAP/TAZ signaling in the liver are still largely unknown. Here, we review miRNAs that influence the proliferation, migration and apoptosis of tumor cells by modulating Hippo-YAP/TAZ signaling during hepatic tumorigenesis. Previous findings suggest that these miRNAs are potential biomarkers and therapeutic targets for the diagnosis, prognosis, and treatment of liver cancer.

Epigenetic regulator BMI1 promotes alveolar rhabdomyosarcoma proliferation and constitutes a novel therapeutic target

Rhabdomyosarcoma (RMS) is an aggressive pediatric soft tissue sarcoma. There are two main subtypes of RMS, alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma. ARMS typically encompasses fusion‐positive rhabdomyosarcoma, which expresses either PAX3‐FOXO1 or PAX7‐FOXO1 fusion proteins. There are no targeted therapies for ARMS; however, recent studies have begun to illustrate the cooperation between epigenetic proteins and the PAX3‐FOXO1 fusion, indicating that epigenetic proteins may serve as targets in ARMS. Here, we investigate the contribution of BMI1, given the established role of this epigenetic regulator in sustaining aggression in cancer. We determined that BMI1 is expressed across ARMS tumors, patient‐derived xenografts, and cell lines. We depleted BMI1 using RNAi and inhibitors (PTC‐209 and PTC‐028) and found that this leads to a decrease in cell growth/increase in apoptosis in vitro, and delays tumor growth in vivo. Our data suggest that BMI1 inhibition activates the Hippo pathway via phosphorylation of LATS1/2 and subsequent reduction in YAP levels and YAP/TAZ target genes. These results identify BMI1 as a potential therapeutic vulnerability in ARMS and warrant further investigation of BMI1 in ARMS and other sarcomas.

Perspective of mesenchymal transformation in glioblastoma

Despite aggressive multimodal treatment, glioblastoma (GBM), a grade IV primary brain tumor, still portends a poor prognosis with a median overall survival of 12–16 months. The complexity of GBM treatment mainly lies in the inter- and intra-tumoral heterogeneity, which largely contributes to the treatment-refractory and recurrent nature of GBM. By paving the road towards the development of personalized medicine for GBM patients, the cancer genome atlas classification scheme of GBM into distinct transcriptional subtypes has been considered an invaluable approach to overcoming this heterogeneity. Among the identified transcriptional subtypes, the mesenchymal subtype has been found associated with more aggressive, invasive, angiogenic, hypoxic, necrotic, inflammatory, and multitherapy-resistant features than other transcriptional subtypes. Accordingly, mesenchymal GBM patients were found to exhibit worse prognosis than other subtypes when patients with high transcriptional heterogeneity were excluded. Furthermore, identification of the master mesenchymal regulators and their downstream signaling pathways has not only increased our understanding of the complex regulatory transcriptional networks of mesenchymal GBM, but also has generated a list of potent inhibitors for clinical trials. Importantly, the mesenchymal transition of GBM has been found to be tightly associated with treatment-induced phenotypic changes in recurrence. Together, these findings indicate that elucidating the governing and plastic transcriptomic natures of mesenchymal GBM is critical in order to develop novel and selective therapeutic strategies that can improve both patient care and clinical outcomes. Thus, the focus of our review will be on the recent advances in the understanding of the transcriptome of mesenchymal GBM and discuss microenvironmental, metabolic, and treatment-related factors as critical components through which the mesenchymal signature may be acquired. We also take into consideration the transcriptomic plasticity of GBM to discuss the future perspectives in employing selective therapeutic strategies against mesenchymal GBM.

Comprehensive Molecular Characterization and Response to Therapy in Fumarate Hydratase-Deficient Renal Cell Carcinoma

PURPOSE

Fumarate hydratase-deficient renal cell carcinoma (FH-RCC) is a rare, aggressive form of RCC associated with hereditary leiomyomatosis and RCC syndrome. Evidence for systemic therapy efficacy is lacking.

EXPERIMENTAL DESIGN

We studied clinical and genomic characteristics of FH-RCC, including response [objective response rate (ORR)] to systemic therapies and next-generation sequencing (NGS). Patients with metastatic FH-RCC, defined by presence of pathogenic germline or somatic FH mutation plus IHC evidence of FH loss, were included.

RESULTS

A total of 28 of 32 included patients (median age 46; range, 20-74; M:F, 20:12) underwent germline testing; 23 (82%) harbored a pathogenic FH germline variant. Five (16%) were negative for germline FH mutations; all had biallelic somatic FH loss. Somatic NGS (31/32 patients) revealed co-occurring NF2 mutation most frequently (n = 5). Compared with clear-cell RCC, FH-RCC had a lower mutation count (median 2 vs. 4; P < 0.001) but higher fraction of genome altered (18.7% vs. 10.3%; P = 0.001). A total of 26 patients were evaluable for response to systemic therapy: mTOR/VEGF combination (n = 18, ORR 44%), VEGF monotherapy (n = 15, ORR 20%), checkpoint inhibitor therapy (n = 8, ORR 0%), and mTOR monotherapy (n = 4, ORR 0%). No complete responses were seen. Median overall and progression-free survival were 21.9 months [95% confidence interval (CI): 14.3-33.8] and 8.7 months (95% CI: 4.8-12.3), respectively.

CONCLUSIONS

Although most FH-RCC tumors are due to germline FH alterations, a significant portion result from biallelic somatic FH loss. Both somatic and germline FH-RCC have similar molecular characteristics, with NF2 mutations, low tumor mutational burden, and high fraction of genome altered. Although immunotherapy alone produced no objective responses, combination mTOR/VEGF therapy showed encouraging results.

Pan-cancer investigation reveals mechanistic insights of planar cell polarity gene Fuz in carcinogenesis

The fuzzy planar cell polarity protein (Fuz) is an effector component of the planar cell polarity (PCP) signaling. Together with other core and effector proteins, the PCP pathway controls polarized cell movements. Fuz was also reported as a negative regulator of cell survival. In this study, we performed a pan-cancer survey to demonstrate the role of Fuz in multiple types of cancer. In head-neck squamous cell carcinoma and lung adenocarcinoma tumor samples, a reduction of Fuz transcript expression was detected. This coincides with the poor overall survival probabilities of these patients. We further showed that Fuz promoter hypermethylation contributes to its transcriptional downregulation. Meanwhile, we also identified a relatively higher mutation frequency at the 404th arginine amino acid residue in the coding sequence of Fuz locus, and further demonstrated that mutant Fuz proteins perturb the pro-apoptotic function of Fuz. In summary, our study unveiled an intriguing relationship between Fuz dysregulation and cancer prognosis, and further provides mechanistic insights of Fuz's involvement in carcinogenesis.

Piezo 1 activation facilitates cholangiocarcinoma metastasis via Hippo/YAP signaling axis

Tumor metastasis is one of the major factors for the high mortality in cholangiocarcinoma (CCA), but its underlying mechanisms are not fully understood. Here, we report that Piezo-type mechanosensitive ion channel component 1 (Piezo 1) is detected to be significantly upregulated in CCA tissues, which is linked to a poor prognosis in patients, suggesting that Piezo 1 may act in a pro-metastatic role in CCA development. Piezo 1 is activated through 20% simulated physiological stretch, and deleting Piezo 1 impedes epithelial-to-mesenchymal transition (EMT) of CCA cells, as well as impairing their metastatic capacity in vitro and in vivo. Mechanistically, the activation of Piezo 1 results in large amounts of Yes-associated protein 1 (YAP) translocated into the nucleus from the cytoplasm, and thus the motility of CCA cells is significantly increased. These findings indicate that mechanical stimulation induces Piezo 1 activation, which might be involved in CCA metastasis via the Hippo/YAP signaling axis. Therefore, Piezo 1 and its downstream effectors may be a novel therapeutic target for CCA treatment.

Control of Cell Growth and Proliferation by the Tribbles Pseudokinase: Lessons from Drosophila

Simple Summary

Tribbles pseudokinases represent a sub-branch of the CAMK (Ca²⁺/calmodulin-dependent protein kinase) subfamily and are associated with disease-associated signaling pathways associated with various cancers, including melanoma, lung, liver, and acute leukemia. The ability of this class of molecules to regulate cell proliferation was first recognized in the model organism Drosophila and the fruit fly genetic model and continues to provide insight into the molecular mechanism by which this family of adapter molecules regulates both normal development and disease associated with corruption of their proper regulation and function.

Abstract

The Tribbles (Trib) family of pseudokinase proteins regulate cell growth, proliferation, and differentiation during normal development and in response to environmental stress. Mutations in human Trib isoforms (Trib1, 2, and 3) have been associated with metabolic disease and linked to leukemia and the formation of solid tumors, including melanomas, hepatomas, and lung cancers. Drosophila Tribbles (Trbl) was the first identified member of this sub-family of pseudokinases and shares a conserved structure and similar functions to bind and direct the degradation of key mediators of cell growth and proliferation. Common Trib targets include Akt kinase (also known as protein kinase B), C/EBP (CAAT/enhancer binding protein) transcription factors, and Cdc25 phosphatases, leading to the notion that Trib family members stand athwart multiple pathways modulating their growth-promoting activities. Recent work using the Drosophila model has provided important insights into novel facets of conserved Tribbles functions in stem cell quiescence, tissue regeneration, metabolism connected to insulin signaling, and tumor formation linked to the Hippo signaling pathway. Here we highlight some of these recent studies and discuss their implications for understanding the complex roles Tribs play in cancers and disease pathologies.

Comprehensive Analysis of the Expression of Key Genes Related to Hippo Signaling and Their Prognosis Impact in Ovarian Cancer

The Hippo signaling pathway, one of the most conserved in humans, controlling dimensions of organs and tumor growth, is frequently deregulated in several human malignancies, including ovarian cancer (OC). The alteration of Hippo signaling has been reported to contribute to ovarian carcinogenesis and progression. However, the prognostic roles of individual Hippo genes in OC patients remain elusive. Herein we investigated the expression level and prognostic value of key Hippo genes in OC using online databases, followed by a qRT-PCR validation step in an additional patient cohort. Using the GEPIA database, we observed an increased level for TP53 and reduced expression level for LATS1, LATS2, MST1, TAZ, and TEF in tumor tissue versus normal adjacent tissue. Moreover, LATS1, LATS2, TP53, TAZ, and TEF expression levels have prognostic significance correlated with progression-free survival. The qRT-PCR validation step was conducted in an OC patient cohort comprising 29 tumor tissues and 20 normal adjacent tissues, endorsing the expression level for LATS1, LATS2, and TP53, as well as for two of the miRNAs targeting the TP53 gene, revealing miR-25-3p upregulation and miR-181c-5p downregulation. These results display that there are critical prognostic value dysregulations of the Hippo genes in OC. Our data demonstrate the major role the conserved Hippo pathway presents in tumor control, underlying potential therapeutic strategies and controlling several steps modulated by miRNAs and their target genes that could limit ovarian cancer progression.

MST4 kinase suppresses gastric tumorigenesis by limiting YAP activation via a non-canonical pathway

Hyperactivation of YAP has been commonly associated with tumorigenesis, and emerging evidence hints at multilayered Hippo-independent regulations of YAP. In this study, we identified a new MST4-YAP axis, which acts as a noncanonical Hippo signaling pathway that limits stress-induced YAP activation. MST4 kinase directly phosphorylated YAP at Thr83 to block its binding with importin α, therefore leading to YAP cytoplasmic retention and inactivation. Due to a consequential interplay between MST4-mediated YAP phospho-Thr83 signaling and the classical YAP phospho-Ser127 signaling, the phosphorylation level of YAP at Thr83 was correlated to that at Ser127. Mutation of T83E mimicking MST4-mediated alternative signaling restrained the activity of both wild-type YAP and its S127A mutant mimicking loss of classical Hippo signal. Depletion of MST4 in mice promoted gastric tumorigenesis with diminished Thr83 phosphorylation and hyperactivation of YAP. Moreover, loss of MST4-YAP signaling was associated with poor prognosis of human gastric cancer. Collectively, our study uncovered a noncanonical MST4-YAP signaling axis essential for suppressing gastric tumorigenesis.

TEAD4 as a Prognostic Marker Promotes Cell Migration and Invasion of Urinary Bladder Cancer via EMT

Purpose

As a member of TEA Domain Transcription Factors (TEADs), TEAD4 was found to be upregulated in urinary bladder cancer (UBC). This study focused on investigating the clinical value and potential functions of TEAD4 in UBC.

Materials and Methods

Patients' samples, TCGA-BLCA and multiple GEO datasets were applied to explore the expression pattern of TEAD4 in UBC. Cox regression and Kaplan-Meier survival analyses were carried out to evaluate the prognostic significance of TEAD4 in UBC. Wound healing and transwell assays were performed to explore the biological functions of TEAD4 in UBC cells.

Results

The results of TCGA-BLCA, GEO datasets, Western blotting and immunohistochemistry staining (IHC) indicated that TEAD4 was strikingly elevated in UBC tissues as compared to their normal counterparts, and upregulation of TEAD4 was significantly correlated with clinical stage, pathological grade and poor clinical outcome. Functional studies demonstrated that TEAD4 knockdown suppressed cell migration and invasion by reducing the expression of epithelial-mesenchymal transition (EMT) related markers and transcription regulators.

Conclusion

Our results suggest that TEAD4 may serve as a novel prognostic biomarker and a promising therapeutic target for UBC, and act as a pro-tumorigenic gene to promote cell migration and invasion by inducing EMT.

Role of the HIPPO pathway as potential key player in the cross talk between oncology and cardiology

The HIPPO pathway (HP) is a highly conserved kinase cascade that affects organ size by regulating proliferation, cell survival and differentiation. Discovered in Drosophila melanogaster to early 2000, it immediately opened wide frontiers in the field of research. Over the last years the field of knowledge on HP is quickly expanding and it is thought will offer many answers on complex pathologies. Here, we summarized the results of several studies that have investigated HP signaling both in oncology than in cardiology field, with an overview on future perspectives in cardiology research.

TGFβ promotes YAP-dependent AXL induction in mesenchymal-type lung cancer cells

The acquisition of chemoresistance remains a major cause of cancer mortality due to the limited accessibility of targeted or immune therapies. However, given that severe alterations of molecular features during epithelial-to-mesenchymal transition (EMT) lead to acquired chemoresistance, emerging studies have focused on identifying targetable drivers associated with acquired chemoresistance. Particularly, AXL, a key receptor tyrosine kinase that confers resistance against targets and chemotherapeutics, is highly expressed in mesenchymal cancer cells. However, the underlying mechanism of AXL induction in mesenchymal cancer cells is poorly understood. Our study revealed that the YAP signature, which was highly enriched in mesenchymal-type lung cancer, was closely correlated to AXL expression in 181 lung cancer cell lines. Moreover, using isogenic lung cancer cell pairs, we also found that doxorubicin treatment induced YAP nuclear translocation in mesenchymal-type lung cancer cells to induce AXL expression. Additionally, the concurrent activation of TGFβ signaling coordinated YAP-dependent AXL expression through SMAD4. These data suggest that crosstalk between YAP and the TGFβ/SMAD axis upon treatment with chemotherapeutics might be a promising target to improve chemosensitivity in mesenchymal-type lung cancer.

Hippo pathway effectors YAP and TAZ and their association with skeletal muscle ageing

Skeletal muscle atrophy commonly occurs during ageing, thus pathways that regulate muscle mass may represent a potential therapeutic avenue for interventions. In this review, we explored the Hippo signalling pathway which plays an essential role in human oncogenesis and the pathway's influence on myogenesis and satellite cell functions, on supporting cells such as fibroblasts, and autophagy. YAP/TAZ was found to regulate both myoblast proliferation and differentiation, albeit with unique roles. Additionally, YAP/TAZ has different functions depending on the expressing cell type, making simple inference of their effects difficult. Studies in cancers have shown that the Hippo pathway influenced the autophagy pathway, although with mixed results. Most of the present researches on YAP/TAZ are focused on its oncogenicity and further studies are needed to translate these findings to physiological ageing. Taken together, the modulation of YAP/TAZ or the Hippo pathway in general may offer potential new strategies for the prevention or treatment of ageing.

Targeting YAP-p62 signaling axis suppresses the EGFR-TKI-resistant lung adenocarcinoma

BACKGROUND

Despite the progress of advanced target therapeutic agents and immune checkpoint inhibitors, EGFR-TKI resistance is still one of the biggest obstacles in treating lung cancer. Clinical studies with autophagy inhibitors are actively underway to overcome drug resistance.

METHODS

We used PC9, PC9/GR, and HCC827/GR cell lines to evaluate the activation of autophagy and EGFR-TKI resistance. Chloroquine was applied as an autophagic blocker and verteporfin was utilized as a YAP inhibitor.

RESULTS

In this study, we tried to reveal the effect of autophagy adaptor p62 which is accumulated by autophagy inhibitor in EGFR-TKI-resistant lung adenocarcinoma. We identified that p62 has oncogenic functions that induce cell proliferation and invasion of EGFR-TKI-resistant lung adenocarcinoma. Interestingly, we found for the first time that YAP regulates p62 transcription through ERK, and YAP inhibition can suppress the expression of oncogenic p62. We also confirmed that the expressions of p62 and YAP have a positive correlation in EGFR-mutant lung adenocarcinoma patients. To block cell survival via perturbing YAP-p62 axis, we treated EGFR-TKI-resistant lung cancer cells with YAP inhibitor verteporfin. Remarkably, verteporfin effectively caused the death of EGFR-TKI-resistant lung cancer cells by decreasing the expressions of p62 with oncogenic function, YAP, and its target PD-L1. So, the cumulative effect of oncogenic p62 should be considered when using autophagy inhibitors, especially drugs that act at the last stage of autophagy such as chloroquine and bafilomycin A1.

CONCLUSION

Finally, we suggest that targeting YAP-p62 signaling axis can be useful to suppress the EGFR-TKI-resistant lung cancer. Therefore, drug repurposing of verteporfin for lung cancer treatment may be valuable to consider because it can inhibit critical targets: p62, YAP, and PD-L1 at the same time.

SOX4 maintains the stemness of cancer cells via transcriptionally enhancing HDAC1 revealed by comparative proteomics study

Background

Cancer stem cells (CSCs) are the root of human cancer development and the major cause of treatment failure. Aberrant elevation of SOX4, a member of SOX (SRY-related HMG-box) family transcription factors, has been identified in many types of human cancer and promotes cancer development. However, the role of SOX4 in CSCs, especially at a proteome-wide level, has remained elusive. The aim of this study is to investigate the effect of SOX4 on the stemness of CSCs and reveal the underlying mechanisms by identification of SOX4-induced proteome changes through proteomics study.

Results

Overexpression of SOX4 promotes sphere formation and self-renewal of colorectal cancer cells in vitro and in vivo and elevates the expression levels of CSCs markers. Through iTRAQ-based quantitative proteomics analysis, 215 differentially expressed proteins (128 upregulated, 87 downregulated) in SOX4-overexpressing HCT-116 spheres were identified. The bioinformatic analysis highlighted the importance of HDAC1 as the fundamental roles of its impacted pathways in stem cell maintenance, including Wnt, Notch, cell cycle, and transcriptional misregulation in cancer. The mechanistic study showed that SOX4 directly binds to the promoter of HDAC1, promotes HDAC1 transcription, thereby supporting the stemness of colorectal cancer cells. HDAC1 hallmarks colorectal cancer stem cells and depletion of HDAC1 abolished the stimulatory effect of SOX4. Furthermore, SOX4-HDAC1 axis is conserved in multiple types of cancer.

Conclusions

The results of this study reveal SOX4-induced proteome changes in HCT-116 spheres and demonstrates that transcriptional activation of HDAC1 is the primary mechanism underlying SOX4 maintaining CSCs. This finding suggests that HDAC1 is a potential drug target for eradicating SOX4-driven human CSCs.

ACTN1 supports tumor growth by inhibiting Hippo signaling in hepatocellular carcinoma

Background

Alpha actinins (ACTNs) are major cytoskeletal proteins and exhibit many non-muscle functions. Emerging evidence have uncovered the regulatory role of ACTNs in tumorigenesis, however, the expression pattern, biological functions, and underlying mechanism of ACTN1 in hepatocellular carcinoma (HCC) remain largely unexplored.

Methods

Immunohistochemical analysis of a HCC tissue microarray (n = 157) was performed to determine the expression pattern and prognostic value of ACTN1 in HCC. In vitro loss-of-function study in HCC cells were carried out to investigate ACTN1 knockdown on cell proliferation. In vivo subcutaneous xenograft model and intrahepatic transplantation model were generated to decipher the contribution of ACTN1 in the tumor growth of HCC. Gene set enrichment analysis, quantitative real-time PCR, Co-immunoprecipitation, immunofluorescence and western blotting were performed to identify the underlying molecular mechanism.

Results

It was found that ACTN1 was significantly upregulated in HCC tissues and closely related to llpha-fetoprotein level, tumor thrombus, tumor size, TNM stage and patient prognoses. Knockdown of ACTN1 suppressed in vitro cell proliferation and in vivo tumor growth of HCC cells. Mechanistically, knockdown of ACTN1 increased Hippo signaling pathway activity and decreased Rho GTPases activities. Mechanistically, ACTN1 could competitively interact with MOB1 and decrease the phosphorylation of LATS1 and YAP. The growth-promoting effect induced by ACTN1 was significantly abrogated by pharmacological inhibition of YAP with verteporfin or super-TDU.

Conclusions

ACTN1 is highly expressed in HCC tissues and acts as a tumor promoter by suppressing Hippo signaling via physical interaction with MOB1. ACTN1 may serve as a potential prognostic marker and therapeutic target for HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01821-6.

Transcriptional activators YAP/TAZ and AXL orchestrate dedifferentiation, cell fate, and metastasis in human osteosarcoma

Osteosarcoma (OS) is a molecularly heterogeneous, aggressive, poorly differentiated pediatric bone cancer that frequently spreads to the lung. Relatively little is known about phenotypic and epigenetic changes that promote lung metastases. To identify key drivers of metastasis, we studied human CCH-OS-D OS cells within a previously described rat acellular lung (ACL) model that preserves the native lung architecture, extracellular matrix, and capillary network. This system identified a subset of cells—termed derived circulating tumor cells (dCTCs)—that can migrate, intravasate, and spread within a bioreactor-perfused capillary network. Remarkably, dCTCs highly expressed epithelial-to-mesenchymal transition (EMT)-associated transcription factors (EMT-TFs), such as ZEB1, TWIST, and SOX9, which suggests that they undergo cellular reprogramming toward a less differentiated state by coopting the same epigenetic machinery used by carcinomas. Since YAP/TAZ and AXL tightly regulate the fate and plasticity of normal mesenchymal cells in response to microenvironmental cues, we explored whether these proteins contributed to OS metastatic potential using an isogenic pair of human OS cell lines that differ in AXL expression. We show that AXL inhibition significantly reduced the number of MG63.2 pulmonary metastases in murine models. Collectively, we present a laboratory-based method to detect and characterize a pure population of dCTCs, which provides a unique opportunity to study how OS cell fate and differentiation contributes to metastatic potential. Though the important step of clinical validation remains, our identification of AXL, ZEB1, and TWIST upregulation raises the tantalizing prospect that EMT-TF-directed therapies might expand the arsenal of therapies used to combat advanced-stage OS.

Association of subcellular localization of TEAD transcription factors with outcome and progression in pancreatic ductal adenocarcinoma

BACKGROUND

Transcriptional enhanced associated domain (TEAD) transcription factors are nuclear effectors of several oncogenic signalling pathways including Hippo, WNT, TGF-ß and EGFR pathways that interact with various cancer genes. The subcellular localization of TEAD regulates the functional output of these pathways affecting tumour progression and patient outcome. However, the impact of the TEAD family on pancreatic ductal adenocarcinoma (PDAC) and its clinical progression remain elusive.

METHODS

A cohort of 81 PDAC patients who had undergone surgery was established. Cytoplasmic and nuclear localization of TEAD1, TEAD2, TEAD3 and TEAD4 was evaluated with the immunoreactive score (IRS) by immunohistochemistry (IHC) using paraffin-embedded tissue. Results were correlated with clinicopathological data, disease-free and overall survival.

RESULTS

Nuclear staining of all four TEADs was increased in pancreatic cancer tissue. Patients suffering from metastatic disease at time of surgery showed a strong nuclear staining of TEAD2 and TEAD3 (p < 0.05). Furthermore, a nuclear > cytoplasmic ratio of TEAD2 and TEAD3 was associated with a shorter overall survival and TEAD2 emerged as an independent prognostic factor for disease-free survival.

CONCLUSION

Our study underlines the importance of TEAD transcription factors in PDAC as a nuclear localization was found to be associated with metastatic disease and an unfavourable prognosis after surgical resection.

Narciclasine is a novel YAP inhibitor that disturbs interaction between YAP and TEAD4

Yes-associated protein (YAP) is involved in development, cell growth, cell size, and homeostasis and plays a key role in the progression of various cancers. Among them, constitutive activation of YAP can often be observed in malignant mesothelioma, which arises in the pleura, peritoneum, and pericardium because of inactivation of the Hippo pathway. To date, however, only less-effective treatments such as chemotherapy, radiation therapy, and surgery are available for patients with malignant mesothelioma. In this study, we identified narciclasine as a novel YAP inhibitor that prevents YAP from interacting with TEAD4 because it competes with TEAD4 for binding to YAP. Furthermore, narciclasine could perturb the cell growth and colony formation of malignant mesothelioma NCI-H290 cells in addition to inhibiting their growth in nude mice. Therefore, narciclasine might be a potential seed for a novel antitumor drug against malignant mesothelioma and other cancers in which hyperactivation and/or overexpression of YAP are observed.