FAT1 Upregulates in Oral Squamous Cell Carcinoma and Promotes Cell Proliferation via Cell Cycle and DNA Repair

Recent advances in the role of atypical cadherin FAT1 in tumorigenesis (Review)

The FAT atypical cadherin 1 (FAT1) gene is the ortholog of the Drosophila fat gene and encodes the protocadherin FAT1. FAT1 belongs to the cadherin superfamily, a group of full-length membrane proteins that contain cadherin-like repeats. In various types of human cancer, FAT1 is one of the most commonly mutated genes, and is considered to be an emerging cancer biomarker and a potential target for novel therapies. However, the biological functions of FAT1 and the precise downstream signaling pathways that it mediates have remained to be fully elucidated. The present review discussed the current literature on FAT1, focusing on FAT1 mutations and expression levels, and their impact on signaling pathways and mechanisms in various types of cancer, including both solid tumors and hematological malignancies, such as esophageal squamous cell carcinoma, head and neck squamous cell carcinoma, lung squamous cell carcinoma, hepatocellular carcinoma, glioma, breast cancer, acute lymphoblastic leukemia, acute myeloid leukemia, lymphoma and myeloma. The present review aimed to provide further insights and research directions for future studies on FAT1 as an oncogenic factor or tumor suppressor.

Reference gene evaluation for normalization of gene expression studies with lymph tissue and node‑derived stromal cells of patients with oral squamous cell carcinoma

Profiling studies using reverse transcription quantitative PCR (RT-qPCR) require reliable normalization to reference genes to accurately interpret the results. A stable reference gene panel was established to profile metastatic and non-metastatic lymph nodes in patients with oral squamous cell carcinoma. The stability of 18S ribosomal RNA (18SrRNA), ribosomal Protein Lateral Stalk Subunit P0 (RPLP0), ribosomal Protein L27 (RPL27), TATA-box binding protein (TBP), hypoxanthine phosphoribosyl-transferase 1 (HPRT1), beta-actin (ACTB), glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) and vimentin (VIM) was evaluated, as reference genes for profiling patient-derived lymph node stromal cells (LNSCs; N=8; N0:6, N+:2) and lymph node tissues (Patients:14, Nodes=20; N0:7; N+:13). The genes were initially assessed based on their expression levels, specificity, and stability rankings to identify the best combination of reference genes. VIM was excluded from the final analysis because of its low expression (high quantification cycle >32) and multiple peaks in the melting curve. The stability analysis was performed using Reffinder, which utilizes four tools; geNorm, NormFinder, BestKeeper and Comparative ∆Ct methods, thereby enabling the computing of a comprehensive ranking. Evaluation of the gene profiles indicated that while RPLP0 and 18SrRNA were stable in both lymph node tissues and LNSCs, HPRT1, RPL27 were uniquely stable in these tissues whereas ACTB and TBP were most stable in LNSCs. The present study identified the most stable reference gene panel for the RT-qPCR profiling of lymph node tissues and patient-derived LNSCs. The observation that the gene panel differed between the two model systems further emphasized the need to evaluate the reference gene subset based on the disease and cellular context.

Identification of key genes and pathways involved in T-DM1-resistance in OE-19 esophageal cancer cells through bioinformatics analysis

Introduction

Esophageal Cancer (EC) ranks among the most common malignancies worldwide. Most EC patients acquire drug resistance to chemotherapy either intrinsically or acquired after T-DM1 treatment, which shows that increasing or decreasing the expression of particular genes might influence chemotherapeutic sensitivity or resistance. Therefore, gaining a deeper understanding of the altered expression of genes involved in EC drug resistance and developing new therapeutic methods are essential targets for continued advancement in EC therapy.

Methods

The present study aimed to find critical regulatory genes/pathways in the progression of T-DM1 resistance in OE-19 EC cells. Expression datasets were extracted from GEO omnibus. Gene interactions were analyzed, and the protein-protein interaction network was drawn. Then, enrichment analysis of the hub genes and network cluster analysis of the hub genes was performed. Finally, the genes were screened in the DrugBank database as therapeutic targets and molecular docking analysis was done on the selected targets.

Results

In the current study, nine hub genes were identified in TDM-1-resistant EC cells (CTGF, CDH17, THBS1, CXCL8, NRP1, ITGB5, EDN1, FAT1, and PTGS2). The KEGG analysis highlighted the IL-17 signaling pathway and ECM-receptor interaction pathway as the most critical pathways; cluster analysis also showed the significance of these pathways. Therefore, the genes involved in these two pathways, including CXCL8, FSCN1, PTGS2, SERPINE2, LEF1, THBS1, CCN2, TAGLN, CDH11, and ITGA6, were searched in DrugBank as therapeutic targets. The DrugBank analysis suggests a potential role for Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) in reducing T-DM1 drug resistance in EC. The docking results revealed that NSAIDs, including Diclofenac, Mefenamic acid, Celecoxib, Naproxen, and Etoricoxib, significantly suppress resistant cancer cells.

Conclusion

This comprehensive bioinformatics analysis deeply explains the molecular mechanisms governing TDM-1 resistance in EC. The identified hub genes and their associated pathways offer potential targets for therapeutic interventions. Moreover, the possible role of NSAIDs in mitigating T-DM1 resistance presents an intriguing avenue for further investigation. This research contributes significantly to the field and establishes a basis for further research to enhance treatment efficacy for EC patients.

Evolutionary dependency of cancer mutations in gene pairs inferred by nonsynonymous-synonymous mutation ratios

BACKGROUND

Determining the impact of somatic mutations requires understanding the functional relationship of genes acquiring mutations; however, it is largely unknown how mutations in functionally related genes influence each other.

METHODS

We employed non-synonymous-to-synonymous or dNdS ratios to evaluate the evolutionary dependency (ED) of gene pairs, assuming a mutation in one gene of a gene pair can affect the evolutionary fitness of mutations in its partner genes as mutation context. We employed PanCancer- and tumor type-specific mutational profiles to infer the ED of gene pairs and evaluated their biological relevance with respect to gene dependency and drug sensitivity.

RESULTS

We propose that dNdS ratios of gene pairs and their derived cdNS (context-dependent dNdS) scores as measure of ED distinguishing gene pairs either as synergistic (SYN) or antagonistic (ANT). Mutation contexts can induce substantial changes in the evolutionary fitness of mutations in the paired genes, e.g., IDH1 and IDH2 mutation contexts lead to substantial increase and decrease of dNdS ratios of ATRX indels and IDH1 missense mutations corresponding to SYN and ANT relationship with positive and negative cdNS scores, respectively. The impact of gene silencing or knock-outs on cell viability (genetic dependencies) often depends on ED, suggesting that ED can guide the selection of candidates for synthetic lethality such as TCF7L2-KRAS mutations. Using cell line-based drug sensitivity data, the effects of targeted agents on cell lines are often associated with mutations of genes exhibiting ED with the target genes, informing drug sensitizing or resistant mutations for targeted inhibitors, e.g., PRSS1 and CTCF mutations as resistant mutations to EGFR and BRAF inhibitors for lung adenocarcinomas and melanomas, respectively.

CONCLUSIONS

We propose that the ED of gene pairs evaluated by dNdS ratios can advance our understanding of the functional relationship of genes with potential biological and clinical implications.

The Predictive Value of BUB1 in the Prognosis of Oral Squamous Cell Carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the most common type of malignant tumour in the oral cavity, and it is known for its poor prognosis. Budding uninhibited by benzimidazoles 1 (BUB1) may be related to cancer prognosis; however, the specific relationship between BUB1 and OSCC prognosis remains largely unexplored.

METHODS

The mRNA levels of BUB1 were analysed using data from the TCGA_OSCC and GSE23558 cohorts. OSCC samples from the TCGA_OSCC dataset were divided into low- and high-BUB1 expression groups based on the median BUB1 level. Furthermore, results of survival analysis, tumour mutation burden (TMB), gene set enrichment analysis (GSEA) pathways, and drug-sensitivity analysis were compared between the 2 groups.

RESULTS

Based on the data from the TCGA_OSCC and GSE23558 cohorts, BUB1 mRNA levels were significantly upregulated in OSCC tissues compared to healthy controls. Moreover, high expression of BUB1 may serve as an independent indicator of poor prognosis in OSCC. Additionally, patients with high BUB1 expression also exhibited increased levels of immune checkpoints and TMB, suggesting that patients with high BUB1 expression may benefit from immunotherapy. Mechanistically, transcription factors ZFP64, TCF3, and ZNF281 were found to potentially bind to the promoter region of BUB1, thereby regulating its gene expression. Furthermore, GSEA results showed that BUB1 expression was closely related to cell cycle and tumour-related pathways in OSCC. Drug-sensitivity analysis showed that patients with high BUB1 expression may be more sensitive to gemcitabine, paclitaxel, or imatinib.

CONCLUSIONS

Collectively, results demonstrated that high BUB1 levels may be related to a poor prognosis of OSCC, highlighting its potential as a novel prognostic biomarker for OSCC.

FAT1 inhibits the proliferation of DLBCL cells via increasing the m6A modification of YAP1 mRNA

Emerging evidence shows that FAT atypical cadherin 1 (FAT1) mutations occur in lymphoma and are associated with poorer overall survival. Considering that diffuse large B cell lymphoma (DLBCL) is the category of lymphoma with the highest incidence rate, this study aims to explore the role of FAT1 in DLBCL. The findings demonstrate that FAT1 inhibits the proliferation of DLBCL cell lines by downregulating the expression of YAP1 rather than by altering its cellular localization. Mechanistic analysis via meRIP-qPCR/luciferase reporter assays showed that FAT1 increases the m6A modification of YAP1 mRNA 3'UTR and the subsequent binding of heterogeneous nuclear ribonucleoprotein D (HNRNPD) to the m6A modified YAP1 mRNA, thus decreasing the stability of YAP1 mRNA. Furthermore, FAT1 increases YAP1 mRNA 3'UTR m6A modification by decreasing the activity of the TGFβ-Smad2/3 pathway and the subsequent expression of ALKBH5, which is regulated at the transcriptional level by Smad2/3. Collectively, these results reveal that FAT1 inhibits the proliferation of DLBCL cells by increasing the m6A modification of the YAP1 mRNA 3'UTR via the TGFβ-Smad2/3-ALKBH5 pathway. The findings of this study therefore indicate that FAT1 exerts anti-tumor effects in DLBCL and may represent a novel target in the treatment of this form of lymphoma.

FAT1 inhibits AML autophagy and proliferation via downregulating ATG4B expression

BACKGROUND

Emerging studies have shown that FAT atypical cadherin 1 (FAT1) and autophagy separately inhibits and promotes acute myeloid leukemia (AML) proliferation. However, it is unknown whether FAT1 were associated with autophagy in regulating AML proliferation.

METHODS

AML cell lines, 6-week-old male nude mice and AML patient samples were used in this study. qPCR/Western blot and cell viability/3H-TdR incorporation assays were separately used to detect mRNA/protein levels and cell activity/proliferation. Luciferase reporter assay was used to examine gene promoter activity. Co-IP analysis was used to detect the binding of proteins.

RESULTS

In this study, we for the first time demonstrated that FAT1 inhibited AML proliferation by decreasing AML autophagy level. Moreover, FAT1 weakened AML autophagy level via decreasing autophagy related 4B (ATG4B) expression. Mechanistically, we found that FAT1 reduced the phosphorylated and intranuclear SMAD family member 2/3 (smad2/3) protein levels, thus decreasing the activity of ATG4B gene promoter. Furthermore, we found that FAT1 competitively bound to TGF-βR II which decreased the binding of TGF-βR II to TGF-βR I and the subsequent phosphorylation of TGF-βR I, thus reducing the phosphorylation and intranuclear smad2/3. The experiments in nude mice showed that knockdown of FAT1 promoted AML autophagy and proliferation in vivo.

CONCLUSIONS

Collectively, these results revealed that FAT1 downregulates ATG4B expression via inhibiting TGFβ-smad2/3 signaling activity, thus decreasing the autophagy level and proliferation activity of AML cells.

GENERAL SIGNIFICANCE

Our study suggested that the "FAT1-TGFβ-smad2/3-ATG4B-autophagy" pathway may be a novel target for developing new targeted drugs to AML treatment.

Predictive capacity of FAT1 transcriptional expression in patients with head and neck squamous cell carcinomas treated with radiotherapy

OBJECTIVE

To analyze the predictive capacity at the primary location of the tumor of the FAT1 transcriptional expression in patients with head and neck squamous cell carcinoma treated with radiotherapy.

MATERIAL AND METHODS

We conducted a retrospective study from biopsies of the primary location of the tumor in 82 patients with head and neck squamous cell carcinoma treated with radiotherapy. The transcriptional expression of FAT1 was determined by RT-PCR. The level of FAT1 transcriptional expression was categorized according to the local control after radiotherapy using a recursive partitioning analysis.

RESULTS

Elevated FAT1 transcriptional expression was associated with an increased risk of local recurrence after radiotherapy. Patients with a high expression level of FAT1 (n=18; 22.0%) had a 5-year local recurrence-free survival of 42.1% (95% CI: 18.6%-65.6%), whereas for patients with a low expression (n=64; 78.0%) it was 72.4% (95% CI: 61.5%-83.3%) (p=0.002). According to the result of a multivariate analysis, patients with a high FAT1 expression category had a 2.3-fold increased risk of local recurrence (95% CI: 1.0-5.2; p=0.043).

CONCLUSIONS

Elevated FAT1 transcriptional expression was associated with a significantly increased risk of local recurrence in patients with head and neck squamous cell carcinoma treated with radiotherapy.

Genetic characteristics of advanced oral tongue squamous cell carcinoma in young patients

OBJECTIVES

We aimed to investigate genetic alterations in oral tongue squamous cell carcinoma (OTSCC) based on age and the clinical significance of these alterations in young OTSCC patients.

MATERIALS AND METHODS

We detected genetic alterations in 44 cases of advanced OTSCC through next-generation sequencing and analyzed and compared patients either younger or older than 45 years. Further analysis was conducted on a validation group of 96 OTSCC patients aged ≤ 45 years to examine the clinical and prognostic associations of TERT promoter (TERTp) mutations.

RESULTS

TP53 mutation was the most common genetic alteration in advanced OTSCC (88.6%), followed by TERTp mutation (59.1%), CDKN2A mutation (31.8%), FAT1 mutation (9.1%), NOTCH1 mutation (9.1%), EGFR amplification (18.2%), and CDKN2A homozygous deletion (4.5%). TERTp mutation was the only genetic alteration significantly enriched in young patients (81.3% in young versus 46.4% in older; P < 0.024). Within the validation group of young patients, TERTp mutation was identified in 30 cases (30/96, 31.3%) and tended to be related to both smoking and alcohol consumption (P = 0.072), higher stage (P = 0.002), more frequent perineural invasion (P = 0.094), and worse overall survival (P = 0.012) than wild type.

CONCLUSION

Our findings suggest that TERTp mutation is more frequent in young patients with advanced OTSCC and is associated with worse clinical outcomes. Therefore, TERTp mutation may serve as a prognostic biomarker for OTSCC in young patients. The findings of this study may help in developing personalized treatment strategies for OTSCC based on age and genetic alterations.

The FAT1 Cadherin Drives Vascular Smooth Muscle Cell Migration

Vascular smooth muscle cells (VSMCs) are normally quiescent and non-migratory, regulating the contraction and relaxation of blood vessels to control the vascular tone. In response to arterial injury, these cells become active; they proliferate, secrete matrix proteins, and migrate, and thereby contribute importantly to the progression of several cardiovascular diseases. VSMC migration specifically supports atherosclerosis, restenosis after catheter-based intervention, transplant vasculopathy, and vascular remodeling during the formation of aneurysms. The atypical cadherin FAT1 is expressed robustly in activated VSMCs and promotes their migration. A positive role of FAT1 in the migration of other cell types, including neurons, fibroblasts, podocytes, and astrocyte progenitors, has also been described. In cancer biology, however, the effect of FAT1 on migration depends on the cancer type or context, as FAT1 either suppresses or enhances cancer cell migration and invasion. With this review, we describe what is known about FAT1's effects on cell migration as well as the factors that influence FAT1-dependent migration. In VSMCs, these factors include angiotensin II, which activates FAT1 expression and cell migration, and proteins of the Atrophin family: Atrophin-1 and the short isoform of Atrophin-2, which promote VSMC migration, and the long isoform of Atrophin-2, which exerts negative effects on FAT1-dependent VSMC migration.

Genome-wide DNA methylation profiling of HPV-negative leukoplakia and gingivobuccal complex cancers

BACKGROUND

Gingivobuccal complex oral squamous cell carcinoma (GBC-OSCC) is an aggressive malignancy with high mortality often preceded by premalignant lesions, including leukoplakia. Previous studies have reported genomic drivers in OSCC, but much remains to be elucidated about DNA methylation patterns across different stages of oral carcinogenesis.

RESULTS

There is a serious lack of biomarkers and clinical application of biomarkers for early detection and prognosis of gingivobuccal complex cancers. Hence, in search of novel biomarkers, we measured genome-wide DNA methylation in 22 normal oral tissues, 22 leukoplakia, and 74 GBC-OSCC tissue samples. Both leukoplakia and GBC-OSCC had distinct methylation profiles as compared to normal oral tissue samples. Aberrant DNA methylation increases during the different stages of oral carcinogenesis, from premalignant lesions to carcinoma. We identified 846 and 5111 differentially methylated promoters in leukoplakia and GBC-OSCC, respectively, with a sizable fraction shared between the two sets. Further, we identified potential biomarkers from integrative analysis in gingivobuccal complex cancers and validated them in an independent cohort. Integration of genome, epigenome, and transcriptome data revealed candidate genes with gene expression synergistically regulated by copy number and DNA methylation changes. Regularised Cox regression identified 32 genes associated with patient survival. In an independent set of samples, we validated eight genes (FAT1, GLDC, HOXB13, CST7, CYB5A, MLLT11, GHR, LY75) from the integrative analysis and 30 genes from previously published reports. Bisulfite pyrosequencing validated GLDC (P = 0.036), HOXB13 (P < 0.0001) promoter hypermethylation, and FAT1 (P < 0.0001) hypomethylation in GBC-OSCC compared to normal controls.

CONCLUSIONS

Our findings identified methylation signatures associated with leukoplakia and gingivobuccal complex cancers. The integrative analysis in GBC-OSCC identified putative biomarkers that enhance existing knowledge of oral carcinogenesis and may potentially help in risk stratification and prognosis of GBC-OSCC.

The diverse functions of FAT1 in cancer progression: good, bad, or ugly?

FAT atypical cadherin 1 (FAT1) is among the most frequently mutated genes in many types of cancer. Its highest mutation rate is found in head and neck squamous cell carcinoma (HNSCC), in which FAT1 is the second most frequently mutated gene. Thus, FAT1 has great potential to serve as a target or prognostic biomarker in cancer treatment. FAT1 encodes a member of the cadherin-like protein family. Under normal physiological conditions, FAT1 serves as a molecular "brake" on mitochondrial respiration and acts as a receptor for a signaling pathway regulating cell-cell contact interaction and planar cell polarity. In many cancers, loss of FAT1 function promotes epithelial-mesenchymal transition (EMT) and the formation of cancer initiation/stem-like cells. However, in some types of cancer, overexpression of FAT1 leads to EMT. The roles of FAT1 in cancer progression, which seems to be cancer-type specific, have not been clarified. To further study the function of FAT1 in cancers, this review summarizes recent relevant literature regarding this protein. In addition to phenotypic alterations due to FAT1 mutations, several signaling pathways and tumor immune systems known or proposed to be regulated by this protein are presented. The potential impact of detecting or targeting FAT1 mutations on cancer treatment is also prospectively discussed.