Fat4 suppression induces Yap translocation accounting for the promoted proliferation and migration of gastric cancer cells

Recurrent somatic mutations of FAT family cadherins induce an aggressive phenotype and poor prognosis in anaplastic large cell lymphoma

BACKGROUND

Anaplastic Large Cell Lymphoma (ALCL) is a rare and aggressive T-cell lymphoma, classified into ALK-positive and ALK-negative subtypes, based on the presence of chromosomal translocations involving the ALK gene. The current standard of treatment for ALCL is polychemotherapy, with a high overall survival rate. However, a subset of patients does not respond to or develops resistance to these therapies, posing a serious challenge for clinicians. Recent targeted treatments such as ALK kinase inhibitors and anti-CD30 antibody-drug conjugates have shown promise but, for a fraction of patients, the prognosis is still unsatisfactory.

METHODS

We investigated the genetic landscape of ALK + ALCL by whole-exome sequencing; recurring mutations were characterized in vitro and in vivo using transduced ALCL cellular models.

RESULTS

Recurrent mutations in FAT family genes and the transcription factor RUNX1T1 were found. These mutations induced changes in ALCL cells morphology, growth, and migration, shedding light on potential factors contributing to treatment resistance. In particular, FAT4 silencing in ALCL cells activated the β-catenin and YAP1 pathways, which play crucial roles in tumor growth, and conferred resistance to chemotherapy. Furthermore, STAT1 and STAT3 were hyper-activated in these cells. Gene expression profiling showed global changes in pathways related to cell adhesion, cytoskeletal organization, and oncogenic signaling. Notably, FAT mutations associated with poor outcome in patients.

CONCLUSIONS

These findings provide novel insights into the molecular portrait of ALCL, that could help improve treatment strategies and the prognosis for ALCL patients.

Genetic landscape and prognosis of conjunctival melanoma in Chinese patients

AIMS

Conjunctival melanoma (CoM) is a rare but highly lethal ocular melanoma and there is limited understanding of its genetic background. To update the genetic landscape of CoM, whole-exome sequencing (WES) and targeted next-generation sequencing (NGS) were performed.

METHODS

Among 30 patients who were diagnosed and treated at Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, from January 2018 to January 2023, WES was performed on 16 patients, while targeted NGS was conducted on 14 patients. Samples were analysed to identify the mutated genes, and the potential predictive factors for progression-free survival were evaluated. Furthermore, the expression of the mutated gene was detected and validated in a 30-patient cohort by immunofluorescence.

RESULTS

Mutations were verified in classic genes, such as BRAF (n=9), NRAS (n=5) and NF1 (n=6). Mutated FAT4 and BRAF were associated with an increased risk for the progression of CoM. Moreover, decreased expression of FAT4 was detected in CoM patients with a worse prognosis.

CONCLUSIONS

The molecular landscape of CoM in Chinese patients was updated with new findings. A relatively high frequency of mutated FAT4 was determined in Chinese CoM patients, and decreased expression of FAT4 was found in patients with worse prognoses. In addition, both BRAF mutations and FAT4 mutations could serve as predictive factors for CoM patients.

Somatic mutations that affect early genetic progression and immune microenvironment in gastric carcinoma

Gastric carcinoma (GC) is a high heterogeneity and malignant tumor with a poor prognosis. The current implementation of immunotherapy in GC is limited due to the insufficient exploration of immune-related mutations and speculated early mutation events. Therefore, we performed whole-exome sequencing on 40 patients with GC to explore their genetic characteristics, shedding light on the order of genetic events, somatic mutations impacting the immune microenvironment, and potential biomarkers for immunotherapy. Regarding genetic events, TP53 disruptions were identified as frequent and early events in GC progression, often occurring alongside other gene mutations. The mutations occurring in GANS, SMAD4, and POLE were early independent events. Patients harboring CSMD3, FAT4, FLG, KMT2C, LRP1B, MUC5B, MUC16, PLEC, RNF43, SYNE1, TP53, TTN, XIRP2, and ZFHX4 mutations tended to have decreased B cells, T cells, macrophage, neutrophil, and dendritic cells infiltration, except for the ARID1A gene mutations. We also found patients with microsatellite instability-high tumors had higher homologous recombination deficiency (HRD) scores. HRD showed a positive correlation with tumor mutational burden, which might serve as indirect evidence supporting the potential of HRD as a biomarker for GC. These findings highlighted GC's high heterogeneity and complexity and provided valuable insights into the somatic mutations that affect early genetic progression and immune microenvironment.

Genome-wide identification and spatiotemporal expression analysis of cadherin superfamily members in echinoderms

BACKGROUND

Cadherins are calcium-dependent transmembrane cell-cell adhesion proteins that are essential for metazoan development. They consist of three subfamilies: classical cadherins, which bind catenin, protocadherins, which contain 6-7 calcium-binding repeat domains, and atypical cadherins. Their functions include forming adherens junctions, establishing planar cell polarity (PCP), and regulating cell shape, proliferation, and migration. Because they are basal deuterostomes, echinoderms provide important insights into bilaterian evolution, but their only well-characterized cadherin is G-cadherin, a classical cadherin that is expressed by many embryonic epithelia. We aimed to better characterize echinoderm cadherins by conducting phylogenetic analyses and examining the spatiotemporal expression patterns of cadherin-encoding genes during Strongylocentrotus purpuratus development.

RESULTS

Our phylogenetic analyses conducted on two echinoid, three asteroid, and one crinoid species identified ten echinoderm cadherins, including one deuterostome-specific ortholog, cadherin-23, and an echinoderm-specific atypical cadherin that possibly arose in an echinoid-asteroid ancestor. Catenin-binding domains in dachsous-2 orthologs were found to be a deuterostome-specific innovation that was selectively lost in mouse, while those in Fat4 orthologs appeared to be Ambulacraria-specific and were selectively lost in non-crinoid echinoderms. The identified suite of echinoderm cadherins lacks vertebrate-specific innovations but contains two proteins that are present in protostomes and absent from mouse. The spatiotemporal expression patterns of four embryonically expressed cadherins (fat atypical cadherins 1 and 4, dachsous-2, and protocadherin-9) were dynamic and mirrored the expression pattern of Frizzled 5/8, a non-canonical Wnt PCP pathway receptor protein essential for archenteron morphogenesis.

CONCLUSIONS

The echinoderm cadherin toolkit is more similar to that of an ancient bilaterian predating protostomes and deuterostomes than it is to the suite of cadherins found in extant vertebrates. However, it also appears that deuterostomes underwent several cadherin-related innovations. Based on their similar spatiotemporal expression patterns and orthologous relationships to PCP-related and tumor-suppressing proteins, we hypothesize that sea urchin cadherins may play a role in regulating the shape and growth of embryonic epithelia and organs. Future experiments will examine cadherin expression in non-echinoid echinoderms and explore the functions of cadherins during echinoderm development.

Prognostic Impact of FSTL3, ADAM12, and FAT4 in Patients of Colon Cancer: Clinicopathologic Study

There is a cellular crosstalk between Wnt/β-catenin and Hippo/Yes-related protein 1 signaling paths in colon cancer (CC) which promotes EMT processes that mediate the metastatic progression of CC. We aimed to evaluate follistatin-like 3 (FSTL3), ADAM12, and FAT4 expressions in CC. A statistical analysis was done to establish how disease-free survival, overall survival (OS), and relapse all performed a prognostic role. High FSTL3 was detected in 68% of CC and significantly related to left-sided tumors ( P = 0.002) and the advanced tumor features, such as metastasis ( P = 0.010), pT ( P = 0.006), high grade ( P = 0.005), lymph node contribution ( P = 0.013), and advanced stage ( P = 0.003). Positive ADAM12 expression was observed in 60% and significantly related to left-sided tumors ( P = 0.001) and significantly common in high grade ( P = 0.028), lymph node involvement ( P < 0.001), and advanced stage ( P = 0.004). Low FAT4 expression was recognized in 76% and linked with the right-sided tumors ( P = 0.036). FAT4 expression was contrariwise linked with CC grade ( P < 0.001). Furthermore, FAT4 expression was inversely correlated with lymph node involvement ( P = 0.002), metastasis ( P = 0.046), and advanced stage ( P = 0.002). During the follow-up, 14 cases were relapsed and positively associated with high FSTL3 expression ( P = 0.001) and ADAM12 expression ( P < 0.001), but negatively linked with FAT4 expression ( P = 0.003). Shorter disease-free survival was substantially correlated with positive ADAM12, extreme FSTL3, and low FAT4 expression ( P < 0.001, P = 0.002, P = 0.003, consecutively). Moreover, Kaplan-Meier curves demonstrated a significant correlation between shorter OS with extreme FSTL3, positive ADAM12, and low FAT4 ( P = 0.004, <0.001, 0.019, consecutively). High FSTL3, positive ADAM12, and low FAT4 expression are unfavorable prognostic influences in CC that may be accountable for relapse and therapeutic resistance in CC.

Fat and Dachsous cadherins in mammalian development

Cell growth and patterning are critical for tissue development. Here we discuss the evolutionarily conserved cadherins, Fat and Dachsous, and the roles they play during mammalian tissue development and disease. In Drosophila, Fat and Dachsous regulate tissue growth via the Hippo pathway and planar cell polarity (PCP). The Drosophila wing has been an ideal tissue to observe how mutations in these cadherins affect tissue development. In mammals, there are multiple Fat and Dachsous cadherins, which are expressed in many tissues, but mutations in these cadherins that affect growth and tissue organization are context dependent. Here we examine how mutations in the Fat and Dachsous mammalian genes affect development in mammals and contribute to human disease.

Genetic Alterations and Deregulation of Hippo Pathway as a Pathogenetic Mechanism in Bone and Soft Tissue Sarcoma

The Hippo pathway is an evolutionarily conserved modulator of developmental biology with a key role in tissue and organ size regulation under homeostatic conditions. Like other signaling pathways with a significant role in embryonic development, the deregulation of Hippo signaling contributes to oncogenesis. Central to the Hippo pathway is a conserved cascade of adaptor proteins and inhibitory kinases that converge and regulate the activity of the oncoproteins YAP and TAZ, the final transducers of the pathway. Elevated levels and aberrant activation of YAP and TAZ have been described in many cancers. Though most of the studies describe their pervasive activation in epithelial neoplasms, there is increasing evidence pointing out its relevance in mesenchymal malignancies as well. Interestingly, somatic or germline mutations in genes of the Hippo pathway are scarce compared to other signaling pathways that are frequently disrupted in cancer. However, in the case of sarcomas, several examples of genetic alteration of Hippo members, including gene fusions, have been described during the last few years. Here, we review the current knowledge of Hippo pathway implication in sarcoma, describing mechanistic hints recently reported in specific histological entities and how these alterations represent an opportunity for targeted therapy in this heterogeneous group of neoplasm.

Meta-transcriptomic comparison of two sponge holobionts feeding on coral- and macroalgal-dissolved organic matter

Background

Sponge holobionts (i.e., the host and its associated microbiota) play a key role in the cycling of dissolved organic matter (DOM) in marine ecosystems. On coral reefs, an ecological shift from coral-dominated to algal-dominated ecosystems is currently occurring. Given that benthic corals and macroalgae release different types of DOM, in different abundances and with different bioavailability to sponge holobionts, it is important to understand how the metabolic activity of the host and associated microbiota change in response to the exposure to both DOM sources. Here, we look at the differential gene expression of two sponge holobionts 6 hours after feeding on naturally sourced coral- and macroalgal-DOM using RNA sequencing and meta-transcriptomic analysis.

Results

We found a slight, but significant differential gene expression in the comparison between the coral- and macroalgal-DOM treatments in both the high microbial abundance sponge Plakortis angulospiculatus and the low microbial abundance sponge Haliclona vansoesti. In the hosts, processes that regulate immune response, signal transduction, and metabolic pathways related to cell proliferation were elicited. In the associated microbiota carbohydrate metabolism was upregulated in both treatments, but coral-DOM induced further lipid and amino acids biosynthesis, while macroalgal-DOM caused a stress response. These differences could be driven by the presence of distinct organic macronutrients in the two DOM sources and of small pathogens or bacterial virulence factors in the macroalgal-DOM.

Conclusions

This work provides two new sponge meta-transcriptomes and a database of putative genes and genetic pathways that are involved in the differential processing of coral- versus macroalgal-DOM as food source to sponges with high and low abundances of associated microbes. These pathways include carbohydrate metabolism, signaling pathways, and immune responses. However, the differences in the meta-transcriptomic responses of the sponge holobionts after 6 hours of feeding on the two DOM sources were small. Longer-term responses to both DOM sources should be assessed to evaluate how the metabolism and the ecological function of sponges will be affected when reefs shift from coral towards algal dominance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08893-y.

Whole genome sequencing and inheritance-based variant filtering as a tool for unraveling missing heritability in pediatric cancer

Survival rates for pediatric cancer have significantly increased the past decades, now exceeding 70-80% for most cancer types. The cause of cancer in children and adolescents remains largely unknown and a genetic susceptibility is considered in up to 10% of the cases, but most likely this is an underestimation. Families with multiple pediatric cancer patients are rare and strongly suggestive for an underlying predisposition to cancer. The absence of identifiable mutations in known cancer predisposing genes in such families could indicate undiscovered heritability. To discover candidate susceptibility variants, whole genome sequencing was performed on germline DNA of a family with two children affected by Burkitt lymphoma. Using an inheritance-based filtering approach, 18 correctly segregating coding variants were prioritized without a biased focus on specific genes or variants. Two variants in FAT4 and DCHS2 were highlighted, both involved in the Hippo signaling pathway, which controls tissue growth and stem cell activity. Similarly, a set of nine non-coding variants was prioritized, which might contribute, in differing degrees, to the increased cancer risk within this family. In conclusion, inheritance-based whole genome sequencing in selected families or cases is a valuable approach to prioritize variants and, thus, to further unravel genetic predisposition in childhood cancer.

Increased expression of FAT4 suppress metastasis of lung adenocarcinoma through regulating MAPK pathway and associated with immune cells infiltration

FAT4 is an extremely large atypical cadherin with crucial roles in the control of planar cell polarity (PCP) and regulation of the Hippo signaling pathway. Our study aims to clarify the FAT4 expression patterns, as well as the significance of FAT4 in predicting the prognosis and cancer immunity to non-small cell lung cancer (NSCLC). FAT4 mRNA and protein expressions were both underregulated in NSCLC and associated with poor prognosis in both lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). In addition, overexpress FAT4 with jujuboside A (JUA) or knockdown FAT4 with siRNA regulated the metastasis of LUAD through MAPK pathways. Moreover, the FAT4 expression included multiple immunological components to promote an immunosuppressive tumor microenvironment (TME). Furthermore, a study of the TCGA-LUAD cohort's DNA methylation results showed that most FAT4 DNA CpG sites were typically hypermethylated in NSCLC relative to the normal lung tissue. The DNA CpG sites cg25879360 and cg26389756 of FAT4 were found to be strongly associated with FAT4 expression in LUAD through the correlation study. In conclusion, this is the first to report the potential function of FAT4 in NSCLC. Hence, FAT4 could be used as a promising prognostic and immunological biomarker for NSCLC.

Emerging Mechanisms of Growth and Patterning Regulation by Dachsous and Fat Protocadherins

Dachsous (Ds) and Fat are evolutionarily conserved cell adhesion molecules that play a critical role in development of multiple organ systems, where they coordinate tissue growth and morphogenesis. Much of our understanding of Ds-Fat signaling pathway comes from studies in Drosophila, where they initiate a signaling pathway that regulate growth by influencing Hippo signaling and morphogenesis by regulating Planar Cell Polarity (PCP). In this review, we discuss recent advances in our understanding of the mechanisms by which Ds-Fat signaling pathway regulates these critical developmental processes. Further, we discuss the progress in our understanding about how they function in mammals.

Diffuse gastric cancer: Emerging mechanisms of tumor initiation and progression

Gastric cancer is globally the fourth leading cause of cancer-related deaths. Patients with diffuse-type gastric cancer (DGC) particularly have a poor prognosis that only marginally improved over the last decades, as conventional chemotherapies are frequently ineffective and specific therapies are unavailable. Early-stage DGC is characterized by intramucosal lesions of discohesive cells, which can be present for many years before the emergence of advanced DGC consisting of highly proliferative and invasive cells. The mechanisms underlying the key steps of DGC development and transition to aggressive tumors are starting to emerge. Novel mouse- and organoid models for DGC, together with multi-omic analyses of DGC tumors, revealed contributions of both tumor cell-intrinsic alterations and gradual changes in the tumor microenvironment to DGC progression. In this review, we will discuss how these recent findings are leading towards an understanding of the cellular and molecular mechanisms responsible for DGC initiation and malignancy, which may provide opportunities for targeted therapies.

The novel FAT4 activator jujuboside A suppresses NSCLC tumorigenesis by activating HIPPO signaling and inhibiting YAP nuclear translocation

FAT atypical cadherin 4 (FAT4) has been identified as a tumor suppressor in lung cancers. However, no agent for lung cancer treatment targeting FAT4 has been used in the clinic. Jujuboside A (JUA) is a major active compound in Semen Ziziphi Spinosae. Semen Ziziphi Spinosae is a traditional Chinese herbal medicine used clinically for tumor treatment to improve patients' quality of life. However, the anti-lung cancer activity and the underlying mechanisms of JUA are not yet fully understood. Here, we demonstrated the anti-lung cancer activity of JUA in two lung cancer mice models and three non-small cell lung cancer (NSCLC) cell lines, and further illustrated its underlying mechanisms. JUA suppressed the occurrence and development of lung cancer and extended mice survival in vivo, and suppressed NSCLC cell activities through cell cycle arrest, proliferation suppression, stemness inhibition and senescence promotion. Moreover, JUA directly bound with and activated FAT4, subsequently activating FAT4-HIPPO signaling and inhibiting YAP nuclear translocation. Knockdown of FAT4 diminished JUA's effects on HIPPO signaling, YAP nuclear translocation, cell proliferation and cellular senescence. In conclusion, JUA significantly suppressed NSCLC tumorigenesis by regulating FAT4-HIPPO-YAP signaling. Our findings suggest that JUA is a novel FAT4 activator that can be developed as a promising NSCLC therapeutic agent targeting the FAT4-HIPPO-YAP pathway.

MiR-106b-5p regulates the migration and invasion of colorectal cancer cells by targeting FAT4

MicroRNA-106b-5p (miR-106b-5p) is involved in the development of many cancers including colorectal cancer (CRC), and FAT4 is correlated with regulation of growth and apoptosis of cancer cells. The present study aimed to investigate the relation between FAT4 and miR-106b-5p and the underlying mechanism of the two on the development of CRC. Quantitative real-time PCR (qRT-PCR) assay and Western blot (WB) analysis were performed to detect the expressions of messenger RNAs (mRNAs), microRNAs (miRNAs) and proteins. The viability of CRC cells was detected by cell counting kit-8 (CCK-8). Scratch test and transwell assay were performed to measure the migration and invasion of CRC cell. Tumor angiogenesis was simulated by in vitro angiogenesis experiment. Dual-luciferase reporter assay was performed to verify the targeting relation between miR-106b-5p and FAT4. The study found that the expression of FAT4 was down-regulated and that of miR-106b-5p was up-regulated in CRC tissues. Overexpression of FAT4 resulted in decreased proliferation, migration, invasion and angiogenesis of CRC cells, whereas silencing of FAT4 led to the opposite results. In rescue experiment, miR-106b-5p partially reversed the function of FAT4 in CRC cells, thus playing a carcinogenic role by targeting FAT4 in the CRC cells.

Leukemia inhibitory factor promotes gastric cancer cell proliferation, migration, and invasion via the LIFR-Hippo-YAP pathway

The long-term outcome of gastric cancer (GC) patients remains unsatisfactory despite some recent improvements. Leukemia inhibitory factor (LIF) is a prognostic biomarker for some solid tumors, however its role in GC remains unknown. In this study, we demonstrated that LIF and LIF receptor (LIFR) are overexpressed in GC tissues and established that a correlation exists between them. LIF and LIFR expression are associated with tumor differentiation, lymphovascular invasion, tumor stage, lymph node metastasis, and pTNM stage, indicating that they may be useful prognostic factors. LIF promoted GC cell proliferation, colony formation, invasion, migration, and tumor growth; it also promoted cell cycle progression and inhibited apoptosis; and knocking out the LIFR gene reversed the effects of LIF. LIF inhibited the activity of the Hippo pathway, resulting in reduced phosphorylation of YAP, increased YAP nuclear translocation, and increased cell proliferation. Finally, silencing YAP mRNA expression suppressed cell proliferation. Overall, the results demonstrate that LIF promotes the malignant biological behavior of GC cells through LIFR-Hippo-YAP signaling. LIF may therefore be a useful biomarker for GC.

Cisplatin promotes the expression level of PD-L1 in the microenvironment of hepatocellular carcinoma through YAP1

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies worldwide. However, the immune tolerance limits the effect of chemotherapeutic drugs. Therefore, the mechanism of cisplatin in promoting PD-L1 expression by YAP1 was investigated in the present study, and we found that cisplatin increased the expression level of YAP1 in the mouse liver with H22 cells. Meanwhile, cisplatin improved the expression level of PD-L1, IL-1β and CCL2 in the tumor microenvironment. Further, cisplatin also enhanced the expression level of YAP1 in shYAP1 HepG2215 cells. The expression of PD-L1 was decreased by Verteporfin, YAP1 inhibitor, during the treatment of DEN/TCPOBOP-induced liver cancer in C57BL/6 mice. These results suggested that cisplatin could deteriorate the immunosuppressive microenvironment through increasing PD-L1, CCL2, IL-1β by upregulated YAP1 expression. Therefore, the study suggested that YAP1 blockade destroyed the immunosuppressive microenvironment of cancer to improve the effect of chemotherapy in HCC.

New insights into the core Hippo signaling and biological macromolecules interactions in the biology of solid tumors

As an evolutionarily conserved pathway, Hippo signaling pathway impacts different pathology and physiology processes such as wound healing, tissue repair/size and regeneration. When some components of Hippo signaling dysregulated, it affects cancer cells proliferation. Moreover, the relation Hippo pathway with other signaling including Wnt, TGFβ, Notch, and EGFR signaling leaves effect on the proliferation of cancer cells. Utilizing a number of therapeutic approaches, such as siRNAs and long noncoding RNA (lncRNA) to prevent cancer cells through the targeting of Hippo pathways, can provide new insights into cancer target therapy. The purpose of present review, first of all, is to demonstrate the importance of Hippo signaling and its relation with other signaling pathways in cancer. It also tries to demonstrate targeting Hippo signaling progress in cancer therapy.

[Emerging roles of Hippo signaling pathway in gastrointestinal cancers and its molecular mechanisms]

Hippo signaling pathway is highly conservative in evolution. MST1/2, LATS1/2, and the effector protein YAP/TAZ are the core members of this signaling pathway in mammalian cells. There have been many studies on YAP/TAZ and its downstream, however, the upstream regulatory factors of the Hippo signaling pathway remain unclear, and become one of the hot research directions of this pathway at present. In addition, Hippo signaling pathway can cross-talk with other signaling pathways such as Wnt and Notch signaling pathways, and plays an important role in controlling organ size, maintaining tissue homeostasis, and promoting tissue repair and regeneration. Abnormal Hippo signaling pathway may lead to the occurrence of a variety of tumors, especially gastrointestinal cancers such as liver cancer, colorectal cancer and gastric cancer. The abnormal expression of its members in gastrointestinal cancers is related to cancer cell proliferation, apoptosis, invasion and migration. Hippo signaling pathway is vital for liver repair and regeneration. Its inactivation will lead to the occurrence of primary liver cancer. The mechanism of YAP in liver cancer mainly depends on TEAD-mediated gene transcription. Hippo signaling pathway is also important for maintaining intestinal homeostasis, and its imbalance can lead to the occurrence and recurrence of colorectal cancer. In primary and metastatic gastric cancer, the expression of YAP/TAZ is significantly up-regulated, but the specific molecular mechanism is unclear. This article summarizes the recent progress on Hippo signaling pathway and its upstream regulatory factors, its roles in the development of gastrointestinal cancers and related molecular mechanisms; and also discusses the future research directions of Hippo signaling pathway.

FAT4 silencing promotes epithelial-to-mesenchymal transition and invasion via regulation of YAP and β-catenin activity in ovarian cancer

Background

The adhesion molecule, FAT4, has a tumor suppressor function with a critical role in the epithelial-to-mesenchymal-transition (EMT) and anti-malignant growth in several cancers. No study has investigated yet its role in epithelial ovarian cancer (EOC) progression. In the present study, we examined the role of FAT4 in proliferation and metastasis, and its mechanisms of interaction in these processes.

Methods

We have performed cell viability, colony formation, and invasion assays in ovarian cancer cells treated with siRNA to knockdown FAT4 gene expression. The regulatory effects of FAT4 on proteins involved in apoptotic, Wnt, Hippo, and retinoblastoma signaling pathways were evaluated by Western blotting following FAT4 repression. Also, 426 ovarian tumor samples and 88 non-tumor samples from the Gene Expression Profiling Interactive Analysis (GEPIA) database were analyzed for the expression of FAT4. Pearson’s correlation was performed to determine the correlation between FAT4 and the E2F5, cyclin D1, cdk4, and caspase 9 expressions.

Results

Lower expression of FAT4 was observed in ovarian cancer cell lines and human samples as compared to non-malignant tissues. This down-regulation seems to enhance cell viability, invasion, and colony formation. Silencing FAT4 resulted in the upregulation of E2F5, vimentin, YAP, β-catenin, cyclin D1, cdk4, and Bcl2, and in the downregulation of GSK-3-β, and caspase 9 when compared to control. Furthermore, regulatory effects of FAT4 on the EMT and aggressive phenotype seem to occur through Hippo, Wnt, and cell cycle pathways.

Conclusion

FAT4 downregulation promotes increased growth and invasion through the activation of Hippo and Wnt-β-catenin pathways.

Hippo-Yap/Taz signaling: Complex network interactions and impact in epithelial cell behavior

The Hippo pathway has emerged as a crucial integrator of signals in biological events from development to adulthood and in diseases. Although extensively studied in Drosophila and in cell cultures, major gaps of knowledge still remain on how this pathway functions in mammalian systems. The pathway consists of a growing number of components, including core kinases and adaptor proteins, which control the subcellular localization of the transcriptional co-activators Yap and Taz through phosphorylation of serines at key sites. When localized to the nucleus, Yap/Taz interact with TEAD transcription factors to induce transcriptional programs of proliferation, stemness, and growth. In the cytoplasm, Yap/Taz interact with multiple pathways to regulate a variety of cellular functions or are targeted for degradation. The Hippo pathway receives cues from diverse intracellular and extracellular inputs, including growth factor and integrin signaling, polarity complexes, and cell-cell junctions. This review highlights the mechanisms of regulation of Yap/Taz nucleocytoplasmic shuttling and their implications for epithelial cell behavior using the lung as an intriguing example of this paradigm. This article is categorized under: Gene Expression and Transcriptional Hierarchies > Regulatory Mechanisms Signaling Pathways > Cell Fate Signaling Establishment of Spatial and Temporal Patterns > Cytoplasmic Localization.

YAP promotes gastric cancer cell survival and migration/invasion via the ERK/endoplasmic reticulum stress pathway

Yes-associated protein (YAP) has been reported to serve an important role in gastric cancer cell survival and migration. However, the underlying mechanism remains unclear. The aim of present study was to identify the underlying mechanism through which Yap sustains gastric cancer viability and migration. The results of the present study demonstrated that YAP expression was upregulated in gastric cancer MKN-28/74 cells compared with normal gastric GES-1 cells. Functional studies revealed that silencing of YAP inhibited gastric cancer MKN-28/74 cell viability and invasion. Mechanistically, YAP may promote gastric cancer cell survival and migration/invasion by inhibiting the endoplasmic reticulum (ER) stress pathway. In addition, YAP may regulate ER stress by activating the ERK signaling pathway. The results of the present study suggested that YAP may be a tumor promoter in gastric cancer and act through the ERK/ER stress pathway; therefore, YAP may have potential implications for new approaches to gastric cancer therapy.

miR-107 regulates growth and metastasis of gastric cancer cells via activation of the PI3K-AKT signaling pathway by down-regulating FAT4

PURPOSE

To investigate the effect of miR-107 on the growth and metastasis of gastric cancer (GC) and elucidate the probable mechanisms.

METHODS

The expression of miR-107 and FAT4 in GC tissues and cells were detected using qRT-PCR. Bioinformatics and dual luciferase reporter gene assays were used to analyze the relationship between miR-107 and FAT4. miR-NC, miR-107 inhibitor, pcDNA3.1-FAT4 and siRNA-FAT4 were transfected into AGS and MKN-45 GC cell lines, respectively. The proliferation and migration abilities of GC cells after transfection were evaluated using the MTT assay, scratch test and transwell assay. The expression of epithelial-mesenchymal transition (EMT) markers: E-cadherin, N-cadherin, vimentin and related proteins of the PI3K/AKT signaling pathway were determined using western blot. The xenograft tumors of nude mice were observed to assess the tumorigenicity of GC cells in vivo.

RESULTS

MiR-107 was up-regulated, while FAT4 was down-regulated in GC tissues and cells (P < 0.05); FAT4 was targeted and negatively regulated by miR-107. Down-regulating miR-107 or up-regulating FAT4 inhibited the GC cells proliferation, migration, invasion and tumorigenicity, and could also reduce the expression of N-cadherin, vimentin, p-PI3K and p-Akt expression and up-regulate E-cadherin.

CONCLUSIONS

miR-107 promotes growth and metastasis in GC via activation of PI3K-AKT signaling by targeting FAT4, which may be a target for GC treatment.

FAT4-USP51 complex regulates the proliferation and invasion of endometrial cancer via Hippo pathway

Recent studies have identified FAT tumour suppressor homologue 4 (FAT4), an essential component of adherents junctions, involved in several cancers. However, its role in endometrial cancer (EC) remains unclear. In this study, we first analyzed the association between FAT4 expression and tumour stage, tumour type, and patient prognosis in 552 tumour samples and 35 non-tumour samples from The Cancer Genome Atlas (TCGA) database. The association of decreased FAT4 expression with advanced signature (lymph node metastasis, lymphovascular invasion and muscular infiltration) in EC patients was also confirmed by our own dataset. Stable FAT4 Knockdown promoted EC cell lines proliferation and invasion. FAT4 overexpression inhibited the parental cell phenotype. FAT4 silencing resulted in decreased phosphorylation of the LATS1/2 and YAP while increased YAP nuclear translocation which was associated with the promotion of proliferation and invasion. PCR array analysis of the negative control and shFAT4 HEC-1B cell lines revealed that the deubiquitinating enzyme USP51 was a FAT4 interacting target gene. Ablating USP51 by shRNA decreased cellular FAT4 protein level while overexpression of USP51 increased FAT4 protein level. Coimmunoprecipitation confirmed the direct binding of FAT4 and USP51 which was essential for FAT4's function in EC. The growth inhibitory effect of FAT4 was also attenuated by USP51 down-regulation. In conclusion, suppression of FAT4 by inactivation of deubiquitinating enzyme USP51 promoted proliferation and invasion of EC cells via inhibiting Hippo pathway.

Huaier Augmented the Chemotherapeutic Sensitivity of Oxaliplatin via Downregulation of YAP in Hepatocellular Carcinoma

For unresectable Hepatocellular carcinoma (HCC), chemotherapy is still an important treatment strategy. Oxaliplatin (Oxa) is an effective treatment of HCC after sorafenib treatment failure. However, the intrinsic or acquired resistance of Oxa affected the chemotherapeutic sensitivity. By analyzing the data of GEO Database, we found that Oxa aberrantly increased the expression of Cysteine-rich61 (Cyr61) in HCC cell lines. Subsequently, in Bel-7404 and SMMC-7721 cells after treated with Oxa, it was verified that the expression of Cyr61 and Yes-associated protein (YAP) was increased. Moreover, we found that blockade of YAP promoted Oxa-induced cell apoptosis for the first time. Meanwhile, our previous study demonstrated that Huaier (HE) inhibited the expression of YAP. Further study found that combination treatment of Oxa and HE had a significantly synergistic anti-cancer effect and significantly inhibited the expression of YAP and apoptosis related proteins. Taken together, we have observed that overexpression of YAP significantly reduced the chemotherapeutic sensitivity of Oxa in HCC for the first time. Combination treatment of Oxa and HE solved this problem.

Identification of genomic aberrations associated with lymph node metastasis in diffuse-type gastric cancer

Diffuse-type gastric cancer (DGC) is a GC subtype with heterogeneous clinical outcomes. Lymph node metastasis of DGC heralds a dismal progression, which hampers the curative treatment of patients. However, the genomic heterogeneity of DGC remains unknown. To identify genomic variations associated with lymph node metastasis in DGC, we performed whole exome sequencing on 23 cases of DGC and paired non-tumor tissues and compared the mutation profiles according to the presence (N3, n = 13) or absence (N0, n = 10) of regional lymph node metastasis. Overall, we identified 185 recurrently mutated genes in DGC, which included a significant novel mutation at CMTM2, as well as previously known mutations at CDH1, RHOA, and TP53. Noticeably, CMTM2 expression could predict the prognostic outcomes of DGC but not intestinal-type GC (IGC), indicating pivotal roles of CMTM2 in DGC progression. In addition, we identified a recurrent loss of heterozygosity (LOH) of DNA copy numbers at the 3p12-pcen locus in DGC. A comparison of N0 and N3 tumors showed that N3 tumors exhibited more frequent DNA copy number aberrations, including copy-neutral LOH and mutations of CpTpT trinucleotides, than N0 tumors (P = 0.2 × 10^-3). In conclusion, DGCs have distinct profiles of somatic mutations and DNA copy numbers according to the status of lymph node metastasis, and this might be helpful in delineating the pathobiology of DGC.

Big roles for Fat cadherins

To create an intricately patterned and reproducibly sized and shaped organ, many cellular processes must be tightly regulated. Cell elongation, migration, metabolism, proliferation rates, cell-cell adhesion, planar polarization and junctional contractions all must be coordinated in time and space. Remarkably, a pair of extremely large cell adhesion molecules called Fat (Ft) and Dachsous (Ds), acting largely as a ligand-receptor system, regulate, and likely coordinate, these many diverse processes. Here we describe recent exciting progress on how the Ds-Ft pathway controls these diverse processes, and highlight a few of the many questions remaining as to how these enormous cell adhesion molecules regulate development.

Low FAT4 expression is associated with a poor prognosis in gastric cancer patients

In this study, we investigated the role of Fat atypical cadherin 4 (FAT4) in gastric cancer (GC) progression. Immunohistochemical analysis showed lower FAT4 expression in tumor tissues from GC patients than in normal gastric epithelium. Lower FAT4 expression was associated with poor prognosis, tumor size and invasion, and lymph node and distant metastases. Multivariate analysis showed that TNM stage, lymph node and distant metastases, Lauren classification, and FAT4 expression were independent prognostic factors in GC. Methylation-specific PCR analysis showed increased FAT4 promoter methylation in GC tumor tissues and cell lines. Higher FAT4 promoter methylation was associated with low FAT4 expression and a poor prognosis. BGC-823 cells showed increased FAT4 expression upon treatment with 5-azacytidine, demethylating agent. FAT4 knockdown in BGC-823 cells led to increased cell proliferation, migration and invasiveness. Moreover, xenografts of BGC-823 cells with FAT4 knockdown showed enhanced tumor growth and metastasis in nude mice. These findings demonstrate that low FAT4 expression is associated with a poor prognosis in GC patients.

Application of unique sequence index (USI) barcode to gene expression profiling in gastric adenocarcinoma

Accurate expression profiling is imperative for understanding the biological roles of mRNAs. Real-time PCR have been at the forefront of biological innovation in detection and monitoring of gene expression, however, fluorophore-labeled oligonucleotides and double-stranded DNA binding dyes, the two most frequently used dyes in RNA detection, are not very cost effective and have poor specificity, respectively. We have developed a cost effective and specific approach for mRNA expression profiling via added unique sequence index (USI) to cDNAs before amplification. USI is a barcode which enable the detection of each target RNA. Using this method, caudal type homeobox 1 (CDX1) and FAT atypical cadherin 4 (FAT4) expressions were investigated in tumoral and non-tumoral tissues of gastric cancer patients and compared with commercial ABI kit. Both methods indicated that FAT4 and CDX1 expression were significantly reduced in gastric cancer tissues compared with adjacent noncancerous tissues. Moreover, we have shown that this assay is highly sensitive, linear and reproducible. USI barcode not only provides a powerful tool for mRNA detection due to its sensitivity, specificity and cost-effectiveness, but also allows comfortable design for real-time qPCR assays within the least time and empowers the analysis of many transcripts of virtually any organism. Furthermore, USI barcode is highly affordable for large numbers of different samples or small sample sizes without microarray and expensive commercial platforms.