Circular RNAs (circRNAs) and eukaryotic translation initiation factor 4A3 (EIF4A3) have been reported to participate in the pathogenesis of nasopharyngeal carcinoma (NPC), but their mechanism has not been fully understood. This research aimed to confirm the role and regulatory mechanism of hsa_circ_0049396 interacting with EIF4A3 in NPC tumorigenesis. Quantitative real time polymerase chain reaction (qRT-PCR) was executed to detect the levels of hsa_circ_0049396 and EIF4A3. Cell function experiments and nude mice xenograft assay were used to confirm the role of hsa_circ_0049396 in NPC. The regulatory effect of EIA4A3 on hsa_circ_0049396 was determined by circInteractome prediction, RNA binding protein immunoprecipitation (RIP) assay, and qRT-PCR. In addition, the Hippo-YAP pathway-related proteins and EIF4A3 protein were detected by western blotting. hsa_circ_0049396 was proved to be downregulated in NPC samples, and its low expression indicated the poor prognosis of NPC. After upregulating hsa_circ_0049396 in NPC cells, the proliferation, migration, invasion, and tumor growth in vivo were suppressed by inhibiting the Hippo-YAP pathway. Moreover, EIF4A3 bound to the flanking regions of the hsa_circ_0049396 to enhance hsa_circ_0049396 expression in NPC cells. hsa_circ_0049396 mediated by EIF4A3 in NPC can attenuate NPC tumorigenesis by inhibiting the Hippo-YAP pathway. This finding may provide a potential early diagnostic biomarker or drug target to improve the precision medicine approaches of NPC.

The type I phosphatidylinositol 4-phosphate 5-kinase (PIP5K) family produces the critical lipid regulator phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) in the plasma membrane (PM). Here, we investigated the potential role of PIP5Kγ, a PIP5K isoform, in the Hippo pathway. The ectopic expression of PIP5Kγ87 or PIP5Kγ90, two major PIP5Kγ splice variants, activated large tumor suppressor kinase 1 (LATS1) and inhibited Yes-associated protein (YAP), whereas PIP5Kγ knockdown yielded opposite effects. The regulatory effects of PIP5Kγ were dependent on its catalytic activity and the presence of Merlin and LATS1. PIP5Kγ knockdown weakened the restoration of YAP phosphorylation upon stimulation with epidermal growth factor or lysophosphatidic acid. We further found that PIP5Kγ90 bound to the Merlin\'s band 4.1/ezrin/radixin/moesin (FERM) domain, forming a complex with PI(4,5)P2 and LATS1 at the PM. Notably, PIP5Kγ90, but not its kinase-deficient mutant, potentiated Merlin-LATS1 interaction and recruited LATS1 to the PM. Consistently, PIP5Kγ knockdown or inhibitor (UNC3230) enhanced colony formation in carcinoma cell lines YAP-dependently. In addition, PIP5Kγ90 interacted with heat shock cognate 71-kDa protein (Hsc70), which also contributed to Hippo pathway activation. Collectively, our results suggest that PIP5Kγ regulates the Hippo-YAP pathway by forming a functional complex with Merlin and LATS1 at the PI(4,5)P2-rich PM and via interplay with Hsc70.

Transcription factor SNAI2 plays key roles during development and has also been known to promote metastasis by inducing invasive phenotype and tumor-initiating activity of cancer cells. However, the post-translational regulation of SNAI2 is less well studied. We performed a dual-luciferase-based, genome-wide E3 ligase siRNA library screen and identified ASB13 as an E3 ubiquitin ligase that targets SNAI2 for ubiquitination and degradation. ASB13 knockout in breast cancer cells promoted cell migration and decreased F-actin polymerization, while overexpression of ASB13 suppressed lung metastasis. Furthermore, ASB13 knockout decreased YAP expression, and such regulation is dependent on an increased protein level of SNAI2, which in turn represses YAP transcription. YAP suppresses tumor progression in breast cancer, as YAP knockout increases tumorsphere formation, anchorage-independent colony formation, cell migration in vitro, and lung metastasis in vivo. Clinical data analysis reveals that ASB13 expression is positively correlated with improved overall survival in breast cancer patients. These findings establish ASB13 as a suppressor of breast cancer metastasis by promoting degradation of SNAI2 and relieving its transcriptional repression of YAP.

Diabetic cardiomyopathy (DCM) is a major diabetes-related microvascular disease. LncRNA MALAT1 is widely expressed in cardiomyocytes responding to hypoxia and high levels of glucose (high glucose). In this study, cardiac fibroblasts (CFs) were transfected with si-MALAT1 and exposed to high glucose. CFs in the high glucose groups were treated with 30 mmol/L glucose, and the control CFs were treated with 5.5 mmol/L glucose. The expression of MALAT1 in the nucleus and cytoplasm of CFs was detected. The biological behavior of CFs, as well as collagen production, activity of the Hippo-YAP pathway, and nuclear localization of YAP were measured. Mouse models of DCM were established to observe the pathological changes to myocardium and determine the levels of collagen I, Bax, and Bcl-2. The interaction between MALAT1 and YAP was analyzed, and CREB expression in the high-glucose treated CFs was detected. MALAT1 was upregulated in high-glucose CFs and located in the nucleus. High-glucose increased collagen production, inflammation, cell proliferation, cell invasiveness, and phosphorylation of MST1 and LATS1, and also promoted nuclear translocation of YAP. These trends in high-glucose treated CFs and the DCM mice were reversed by transfection with si-MALAT1. MALAT1 positively regulated the nuclear translocation of YAP by binding to CREB. CREB levels were increased in the high-glucose CFs, but decreased after silencing MALAT1. These results indicate that si-MALAT1 reduces inflammation and collagen accumulation in high-glucose CFs and DCM mice via the Hippo-YAP pathway and CREB.

UNASSIGNED: Gastric carcinoma is the second most frequently diagnosed cancer and leading cause of cancer death in China. As a new generation of cancer therapeutic drug, CL-6, a curcumin derivative, shows better bioavailability than curcumin, which has shown anticancer effects in gastric cancer (GC). However, whether CL-6 shows similar activities in GC has not been examined.
UNASSIGNED: Cell proliferation assay, colony-forming assay, flow cytometric analysis, wound healing assay, and Transwell invasion assay were performed to examine the effects of CL-6 on proliferation, apoptosis, migration, and invasion on human AGS and MGC-803 cell lines. Western blot was used to evaluate protein levels of Bax, Bcl-2, YAP, p-YAP, and Lats, and gene expression was measured by real-time quantitative PCR (RT-qPCR).
UNASSIGNED: CL-6 dose dependently reduced proliferation, increased apoptosis, and inhibited the migration and invasion abilities of AGS and MGC-803 cells. CL-6 also increased levels of pro-apoptotic protein Bax, decreased levels of antiapoptotic protein Bcl-2, and increased the Bax/Bcl-2 ratio. CL-6 treatment also inhibited YAP and YAP protein and mRNA expression, while it induced the expression of Lats and p-YAP (Ser127).
UNASSIGNED: CL-6 induces apoptosis of GC cells by activating the Hippo-YAP signaling pathway. These results indicate the therapeutic potential of the novel curcumin derivative CL-6 in GC.

Zyxin is a member of the focal adhesion complex and plays a critical role in actin filament polymerization and cell motility. Several recent studies showed that Zyxin is a positive regulator of Yki/YAP (Yes-associated protein) signaling. However, little is known about the mechanisms by which Zyxin itself is regulated and how Zyxin affects Hippo-YAP activity. We first showed that Zyxin is phosphorylated by CDK1 during mitosis. Depletion of Zyxin resulted in significantly impaired colon cancer cell proliferation, migration, anchorage-independent growth, and tumor formation in xenograft animal models. Mitotic phosphorylation is required for Zyxin activity in promoting growth. Zyxin regulates YAP activity through the colon cancer oncogene CDK8. CDK8 knockout phenocopied Zyxin knockdown in colon cancer cells, while ectopic expression of CDK8 substantially restored the tumorigenic defects of Zyxin-depletion cells. Mechanistically, we showed that CDK8 directly phosphorylated YAP and promoted its activation. Fully activated YAP is required to support the growth in CDK8-knockout colon cancer cells in vitro and in vivo. Together, these observations suggest that Zyxin promotes colon cancer tumorigenesis in a mitotic-phosphorylation-dependent manner and through CDK8-mediated YAP activation.