Filamin Research Articles

Therapeutic potential of targeting the FLNA-regulated Wee1 kinase in adrenocortical carcinomas.

Filamin A (FLNA) is poorly expressed in adrenocortical carcinomas (ACC) compared to adenomas (ACA). Its presence is associated to a less aggressive tumour behaviour, potentially due to its role in negatively regulating IGF1R signalling. Upregulation of G2/M Wee1 kinase was shown in FLNA-deficient mouse neural progenitor cells, and it has been reported in several tumours. This study explored Wee1 expression in ACC and its regulation by FLNA, the effects of Wee1 inhibitor AZD1775, and the impact of FLNA on its efficacy in ACC cell lines and primary cells. Analysis of FLNA and Wee1 proteins revealed elevated Wee1 and reduced FLNA in ACC compared to normal adrenal gland. FLNA knockdown increased Wee1 protein in NCI-H295R, MUC-1, and in primary ACC cells. Higher p-CDK1 and cyclin B1 were shown in FLNA-silenced MUC-1, while decreased Wee1, p-CDK1 and cyclin B1 resulted after FLNA overexpression. Wee1 reduction was reverted by lactacystin treatment and FLNA transfection increased p-Wee1 (Ser123), suggesting FLNA's role in targeting Wee1 for degradation. AZD1775 dose-dependently reduced proliferation and viability in ACC cell lines and primary cultures, and it triggered MUC-1 cell death. Similar effects were induced by Wee1 silencing. FLNA depletion augmented AZD1775's efficacy in reducing proliferation and potentiating apoptosis in MUC-1 and primary cells. In conclusion, we demonstrated that FLNA regulates Wee1 expression by promoting its degradation, suggesting that low FLNA typical of ACC leads to increased Wee1 with consequent cancer cells growth. It proposes Wee1 inhibition as a new potential therapeutic approach for ACC, particularly for those lacking FLNA.

Pulmonary hypertension in patients carrying FLNA loss-of-function variants.

Pulmonary hypertension (PH) is an unusual complication of X-linked disease caused by loss-of-function (LOF) variants in the filamin A (FLNA) gene. Patients with FLNA LOF may also present dysmorphic facial features, aortic dilation, thrombopenia, and periventricular nodular heterotopia (PVNH). We reported clinical, functional, radiologic, and hemodynamic characteristics of patients with FLNA LOF variants and PH from the French PH Network. Nine patients were identified with a female to male ratio of 8:1. PH was diagnosed at a median age of 36 [0-69] years. Associated conditions included epilepsy (n=5), PVNH (n=7), valvular heart disease (n=8), congenital heart diseases (n=4), thrombocytopenia (n=4), and hyperlaxity (n=4). Right heart catheterisation confirmed moderate-to-severe precapillary PH with a median mPAP of 33 [22-49] mmHg and PVR of 4.7 [2.4-8.0] WU. The DLCO was markedly decreased (48 [22-64] %pred) and five patients had obstructive ventilatory disorder. High-resolution CT showed heterogeneous parenchyma (n=8), emphysema (n=3), presence of a peripheral hyperclear band (n=3) and aortic ectasia (n=4). Pathologic assessment available in one patient revealed significant remodelling of small pulmonary arteries, interstitial edema, and irregular alveoli shapes. During follow-up, three patients died, including two from right heart failure. No patient died from aortic rupture. Precapillary PH, likely due to multiple mechanisms, may complicate the course of patients with LOF FLNA variants and may be the presenting symptom leading to diagnosis. The combination of PH with parenchymal involvement and extrapulmonary symptoms (epilepsy, congenital heart diseases, valvular and aortic involvement, thrombocytopenia) should prompt genetic screening for FLNA.

Dysfunctional atrial fibroblast processing of filamin A in atrial fibrillation

Abstract Background/Introduction Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, is associated with atrial structural remodelling, hallmarked by fibrosis. Atrial fibrosis is instigated by atrial fibroblasts (AFBs). It was previously uncovered the hormone calcitonin (CT) is produced in the heart and, via binding to the CT-receptors (CTR), inhibits atrial fibrogenesis and fibroblast profibrotic activity. [1] In AF, abnormally increased CTR internalisation causes loss of physiological surface CTR and prevents fibroblast activation by CT. The molecular mechanisms of this phenomenon in ACFs are unknown. Aim To explore the role of filamin A (FLNa), an actin cross-linking protein that was previously shown to interact with CTR, [2] in the regulation of CTR trafficking. Methods AFBs were enzymatically isolated from left atrial appendage biopsies collected from 30 patients in persistent AF or normal sinus rhythm (SR, controls) undergoing elective heart surgery. Immunostaining assessed the localisation of CTR and its overlap with the nucleus (stained with DAPI) and FLNa in AFBs. Co-localisation was quantified by the JACoP BIOP plugin for ImageJ. Target mRNA expression was assessed by RT-qPCR and protein levels by immunoblot. Immunoprecipitation (IP) then immunoblot (IB) validated protein-protein interactions. Calpain activity was assessed with a fluorescence-based assay. The effects of calpains on FLNa proteolytic processing was examined with calpain inhibitor calpeptin (10nM–100nM vs DMSO loading control). Results Immunostaining revealed aberrant, intracellular localisation of CTR in AF-AFBs (A) with increased nuclear localisation (p=0.03) and reduced co-localisation with FLNa (p=0.03). FLNa gene expression showed a trend towards reduction in AF (by 36%, p=0.06; B). Meanwhile, although full-length FLNa protein was unaltered in AF, there was a striking 67% reduction (p=0.02) in the expression of FLNa’s c-terminal fragment (FLNaCT), which contains the CTR binding domain (C). Co-immunoprecipitation confirmed a physical interaction between CTR and FLNaCT (D) in both SR and AF AFBs. FLNaCT is typically generated when FLNa is cleaved by the protease calpain 1, whose protein (F) but not mRNA (E), was significantly downregulated (71%, p<0.001) in AF. Puzzlingly, a ~70% loss of calpain 1 protein was associated with unchanged calpain activity (G) and FLNaCT levels in AFBs treated with calpain inhibitor calpeptin (H). Conclusions Persistent AF is associated with an aberrant CTR localisation and FLNa proteolytic processing, not attributable to altered calpain activity. Further characterisation of the molecular determinants of the altered CTR localisation may uncover novel and potentially druggable facets of structural remodelling in AF.

Splicing dysregulation in glioblastoma alters the function of cell migration-related genes.

Glioblastoma (GBM) has a poor prognosis with a high recurrence and low survival rate. Previous RNA-seq analyses have revealed that alternative splicing (AS) plays a role in GBM progression. Here, we present a novel AS analysis method (Semi-Q) and describe its use to identify GBM-specific AS events. We analyzed RNA-seq data from normal brain (NB), normal human astrocytes (NHAs) and GBM samples, and found that comparison between NHA and GBM was especially informative. Importantly, this analysis revealed that genes encoding cell migration-related proteins, including filamins (FLNs) and actinins (ACTNs), were among those most affected by differential AS. Functional assays revealed that dysregulated AS of FLNA, B and C transcripts produced protein isoforms that not only altered transcription of cell proliferation-related genes but also led to enhanced cell migration, resistance to cell death and/or mitochondrial respiratory function, while a dysregulated AS isoform of ACTN4 enhanced cell migration. Together, our results indicate that cell migration and actin cytoskeleton-related genes are differentially regulated by AS in GBM, supporting a role for AS in facilitating tumor growth and invasiveness.

Significance of Fibrillin-1, Filamin A, MMP2 and SOX9 in Mitral Valve Pathology.

Genetic factors play a significant role in the pathogenesis of mitral valve diseases, including mitral valve prolapse (MVP) and mitral valve regurgitation. Genes like Fibrillin-1 (FBN1), Filamin A (FLNA), matrix metalloproteinase 2 (MMP2), and SRY-box transcription factor 9 (SOX9) are known to influence mitral valve pathology but knowledge of the exact mechanism is far from clear. Data regarding serum parameters, transesophageal echocardiography, and genetic and histopathologic parameters were investigated in 54 patients who underwent cardiovascular surgery for mitral valve regurgitation. The possible association between Fibrillin-1, Filamin A, MMP2, and SOX9 gene expressions was checked in relationship with the parameters of systemic inflammatory response. The mRNA expression levels (RQ-relative quantification) were categorized into three distinct groups: low (RQ < 1), medium/normal (RQ = 1-2), and high (RQ > 2). Severe fibrosis of the mitral valve was reflected by high expression of FBN1 and low expression of MMP2 (p < 0.05). The myxoid degeneration level was associated with the mRNA expression level for FBN1 and a low lymphocyte-monocyte ratio was associated with an increased mRNA expression of FBN1 (p < 0.05). A high number of monocytes was associated with high values of FBN1 whereas the increase in the number of lymphocytes was associated with high levels of MMP2. In addition, we observed that the risk of severe hyalinization was enhanced by a low mRNA expression of FLNA and/or SOX9. In conclusion, a lower FLNA mRNA expression can reflect the aging process that is highlighted in mitral valve pathology as a higher risk for hyalinization, especially in males, that might be prevented by upregulation of the SOX9 gene. FBN1 and MMP2 influence the inflammation-related fibrotic degeneration of the mitral valve. Understanding the genetic base of mitral valve pathology can provide insights into disease mechanisms, risk stratification, and potential therapeutic targets.

Filamin A regulates platelet shape change and contractile force generation via phosphorylation of the myosin light chain.

Platelets are critical mediators of hemostasis and thrombosis. Platelets circulate as discs in their resting form but change shape rapidly upon activation by vascular damage and/or soluble agonists such as thrombin. Platelet shape change is driven by a dynamic remodeling of the actin cytoskeleton. Actin filaments interact with the protein myosin, which is phosphorylated on the myosin light chain (MLC) upon platelet activation. Actin-myosin interactions trigger contraction of the actin cytoskeleton, which drives platelet spreading and contractile force generation. Filamin A (FLNA) is an actin cross-linking protein that stabilizes the attachment between subcortical actin filaments and the cell membrane. In addition, FLNA binds multiple proteins and serves as a critical intracellular signaling scaffold. Here, we used platelets from mice with a megakaryocyte/platelet-specific deletion of FLNA to investigate the role of FLNA in regulating platelet shape change. Relative to controls, FLNA-null platelets exhibited defects in stress fiber formation, contractile force generation, and MLC phosphorylation in response to thrombin stimulation. Blockade of Rho kinase (ROCK) and protein kinase C (PKC) with the inhibitors Y27632 and bisindolylmaleimide (BIM), respectively, also attenuated MLC phosphorylation; our data further indicate that ROCK and PKC promote MLC phosphorylation through independent pathways. Notably, the activity of both ROCK and PKC was diminished in the FLNA-deficient platelets. We conclude that FLNA regulates thrombin-induced MLC phosphorylation and platelet contraction, in a ROCK- and PKC-dependent manner.

Targeting Cleavage of C-Terminal Fragment of Cytoskeletal Filamin A in Cancers.

Human cancers express altered levels of actin-binding cytoskeletal filamin A (FLNA) protein. FLNA in mammals consists of an actin-binding domain at its N-terminus that is followed by 24 immunoglobulin-like repeat modules interrupted by two hinge regions between repeats 15-16 and 23-24. Cleavage of these hinge regions produces a naturally occurring C-terminal 90 kDa fragment of FLNA (FLNACT) that physically interacts with multiple proteins with diverse functions. This cleavage leads to actin cytoskeleton remodeling, which in turn contributes to cellular signaling, nucleocytoplasmic shuttling of transcriptional factors and nuclear receptors, and regulation of their transcriptional activities that are important for initiation and progression of cancers. Therefore, recent studies have proposed blocking FLNA cleavage as a means of cancer therapy. Here, we update how FLNA cleavage has been targeted by different approaches and their potential implications for future treatment of human cancers.

Reducing Filamin A Restores Cortical Synaptic Connectivity and Early Social Communication Following Cellular Mosaicism in Autism Spectrum Disorder Pathways.

Communication in the form of nonverbal, social vocalization, or crying is evolutionary conserved in mammals and is impaired early in human infants that are later diagnosed with autism spectrum disorder (ASD). Defects in infant vocalization have been proposed as an early sign of ASD that may exacerbate ASD development. However, the neural mechanisms associated with early communicative deficits in ASD are not known. Here, we expressed a constitutively active mutant of Rheb (RhebS16H), which is known to upregulate two ASD core pathways, mTOR complex 1 (mTORC1) and ERK1/2, in Layer (L) 2/3 pyramidal neurons of the neocortex of mice of either sex. We found that cellular mosaic expression of RhebS16H in L2/3 pyramidal neurons altered the production of isolation calls from neonatal mice. This was accompanied by an expected misplacement of neurons and dendrite overgrowth, along with an unexpected increase in spine density and length, which was associated with increased excitatory synaptic activity. This contrasted with the known decrease in spine density in RhebS16H neurons of 1-month-old mice. Reducing the levels of the actin cross-linking and adaptor protein filamin A (FLNA), known to be increased downstream of ERK1/2, attenuated dendrite overgrowth and fully restored spine properties, synaptic connectivity, and the production of pup isolation calls. These findings suggest that upper-layer cortical pyramidal neurons contribute to communicative deficits in a condition known to affect two core ASD pathways and that these mechanisms are regulated by FLNA.

Exploring the immune landscape of disulfidptosis in ulcerative colitis and the role of modified gegen qinlian decoction in mediating disulfidptosis to alleviate colitis in mice

Ethnopharmacological relevanceUlcerative colitis (UC), a recurrent inflammatory bowel disease, continues to challenge effective pharmacologic management. Disulfidptosis, a recently identified form of cell death, appears implicated in the progression of various diseases. Scientific studies have demonstrated that Modified Gegen Qinlian decoction (MGQD) alleviates UC symptoms. However, the underlying mechanisms remain inadequately elucidated. Aim of the studyThis study investigated the role of disulfidptosis in UC and explored the potential of MGQD to ameliorate UC by mediating disulfidptosis. MethodsMicroarray data were utilized to identify disulfidptosis-related genes stably expressed in UC, and integrated genomic analyses were conducted to elucidate the landscape of disulfidptosis in UC. Subsequently, C57BL/6J mice were administered 3% dextran sodium sulfate (DSS) to induce experimental colitis and treated with MGQD. Quantitative real-time polymerase chain reaction and immunohistochemical analysis of colonic tissues from colitis mice were performed to validate the microarray data findings. Finally, molecular docking was employed to explore the binding interactions between MGQD components and disulfidptosis biomarkers. ResultsMyosin heavy chain 10 (MYH10) and filamin A (FLNA) were identified as stably expressed in UC, demonstrating high diagnostic value for the disease. Correlation analysis indicated that disulfidptosis-related genes are associated with elevated levels of immune cells in UC. Single gene set enrichment analysis further clarified that these genes might be involved in the pathological processes of UC via immune-related pathways. Subsequent animal experiments revealed that MYH10 and FLNA were significantly upregulated in mice with colitis, a condition reversed by MGQD treatment. Molecular docking results showed that MYH10 and FLNA serve as stable binding targets for the primary components of MGQD. ConclusionsThe study identified a connection between the disulfidptosis-related landscape and immune infiltration in UC, suggesting that MGQD may modulate disulfidptosis by inhibiting MYH10 and FLNA, thereby alleviating UC.

Contributions of Germline and Somatic Mosaic Genetics to Thoracic Aortic Aneurysms in Nonsyndromic Individuals.

Thoracic aortic aneurysm (TAA) is associated with significant morbidity and mortality. Although individuals with family histories of TAA often undergo clinical molecular genetic testing, adults with nonsyndromic TAA are not typically evaluated for genetic causes. We sought to understand the genetic contribution of both germline and somatic mosaic variants in a cohort of adult individuals with nonsyndromic TAA at a single center. One hundred eighty-one consecutive patients <60 years who presented with nonsyndromic TAA at the Massachusetts General Hospital underwent deep (>500×) targeted sequencing across 114 candidate genes associated with TAA and its related functional pathways. Samples from 354 age- and sex-matched individuals without TAA were also sequenced, with a 2:1 matching. We found significant enrichments for germline (odds ratio [OR], 2.44, P=4.6×10-6 [95% CI, 1.67-3.58]) and also somatic mosaic variants (OR, 4.71, P=0.026 [95% CI, 1.20-18.43]) between individuals with and without TAA. Likely genetic causes were present in 24% with nonsyndromic TAA, of which 21% arose from germline variants and 3% from somatic mosaic alleles. The 3 most frequently mutated genes in our cohort were FLNA (encoding Filamin A), NOTCH3 (encoding Notch receptor 3), and FBN1 (encoding Fibrillin-1). There was increased frequency of both missense and loss of function variants in TAA individuals. Likely contributory dominant acting genetic variants were found in almost one quarter of nonsyndromic adults with TAA. Our findings suggest a more extensive genetic architecture to TAA than expected and that genetic testing may improve the care and clinical management of adults with nonsyndromic TAA.

CircRNA ATF6 suppresses bladder cancer cell proliferation and migration via miR-146a-5p/FLNA axis

BackgroundBladder cancer (BCa) is the most common malignancy with increasing morbidity and mortality. Circular RNA (circRNA) ATF6 level was downregulated in BCa after GSE92675 CircRNA microarray dataset was analyzed using GEO2R. However, its function and mechanism in BCa remain largely unknown. MethodsGEO2R and reverse transcription quantitative polymerase chain reaction (RT-qPCR) were used to measure levels of circRNA ATF6, microRNA-146a-5p (miR-146a-5p), and filamin A (FLNA). CircRNA ATF6 stability was assessed by actinomycin D and RNase R assays, while circRNA ATF6 cellular localization was examined by FISH experiments in T24 cells. Cell counting kit-8 (CCK-8), colony formation, wound-healing, and transwell assays were used to study circRNA ATF6’s function in growth, motility, and invasion. By examining luciferase, starBase, RNA pull-down, and RNA immunoprecipitation (RIP) experiments, we anticipated and confirmed miR-146a-5p interactions with circRNA ATF6, as well as miR-146a-5p interactions with FLNA. On tumor-bearing mice, in vivo experiments were conducted. ResultsMiR-146a-5p expression in Bca was elevated, while circRNA ATF6 and FLNA were downregulated. CircRNA ATF6 showed better stability in BCa cells, with its expression primarily in the cytoplasm. Upregulating circRNA ATF6 lowered BCa cell viability, colony numbers, and invasion numbers, but broadened their migratory pattern. MiR-146a-5p was directly sponged up by circRNA ATF6, which also detrimentally affected miR-146a-5p levels in BCa. MiR-146a-5p reduced BCa FLNA expression by targeting FLNA. FLNA silencing abolished circRNA ATF6’s mitigating function in BCa cell proliferation, motility, and invasion. In vivo, overexpression of circRNA ATF6 significantly reduced tumor volume and weight. ConclusionCircRNA ATF6 suppresses BCa cell growth, migration and invasion through the miR-146a-5p/FLNA axis.

FLNA regulates neuronal maturation by modulating RAC1-Cofilin activity in the developing cortex

Periventricular nodular heterotopia (PNH), the most common brain malformation diagnosed in adulthood, is characterized by the presence of neuronal nodules along the ventricular walls. PNH is mainly associated with mutations in the FLNA gene - encoding an actin-binding protein - and patients often develop epilepsy. However, the molecular mechanisms underlying the neuronal failure still remain elusive. It has been hypothesized that dysfunctional cortical circuitry, rather than ectopic neurons, may explain the clinical manifestations. To address this issue, we depleted FLNA from cortical pyramidal neurons of a conditional Flnaflox/flox mice by timed in utero electroporation of Cre recombinase. We found that FLNA regulates dendritogenesis and spinogenesis thus promoting an appropriate excitatory/inhibitory inputs balance. We demonstrated that FLNA modulates RAC1 and cofilin activity through its interaction with the Rho-GTPase Activating Protein 24 (ARHGAP24). Collectively, we disclose an uncharacterized role of FLNA and provide strong support for neural circuit dysfunction being a consequence of FLNA mutations.

Label free quantitative proteomic profiling of serum samples of intellectually disabled young patients revealed dysregulation of complement coagulation and cholesterol cascade systems.

Intellectual disability is a heterogeneous disorder, diagnosed using intelligence quotient (IQ) score criteria. Currently, no specific clinical test is available to diagnose the disease and its subgroups due to inadequate understanding of the pathophysiology. Therefore, current study was designed to explore the molecular mechanisms involved in disease perturbation, and to identify potential biomarkers for disease diagnosis and prognosis. A total of 250 participants were enrolled in this study, including 200 intellectually disabled (ID) subjects from the subgroups (mild, moderate, and severe) with age and gender matched healthy controls (n = 50). Initially, IQ testing score and biochemical profile of each subject was generated, followed by label-free quantitative proteomics of subgroups of IQ and healthy control group through nano-LC/MS- mass spectrometry. A total of 310 proteins were identified, among them198 proteins were common among all groups. Statistical analysis (ANOVA) of the subgroups of ID showed 142 differentially expressed proteins, in comparison to healthy control group. From these, 120 proteins were found to be common among all subgroups. The remaining 22 proteins were categorized as exclusive proteins found only in disease subgroups. Furthermore, the hierarchical cluster analysis (HCL) of common significant proteins was also performed, followed by PANTHER protein classification and GO functional enrichment analysis. Results provides that the datasets of differentially expressed proteins, belong to the categories of immune / defense proteins, transfer carrier proteins, apolipoproteins, complement proteins, protease inhibitors, hemoglobin proteins etc., they are known to involvein immune system, and complement and coagulation pathway cascade and cholesterol metabolism pathway. Exclusively expressed 22 proteins were found to be disease stage specific and strong PPI network specifically those that have significant role in platelets activation and degranulation, such as Filamin A (FLNA). Furthermore, to validate the mass spectrometric findings, four highly significant proteins (APOA4, SAP, FLNA, and SERPING) were quantified by ELISA in all the study subjects. AUROC analysis showed a significant association of APOA4 (0.830), FLNA (0.958), SAP (0.754) and SERPING (0.600) with the disease. Apolipoprotein A4 (APOA4) has a significant role in cholesterol transport, and in modulation of glucose and lipid metabolism in the CNS. Similarly, FLNA has a crucial role in the nervous system, especially in the functioning of synaptic network. Therefore, both APOA4, and FLNA proteins represent good potential for candidate biomarkers for the diagnosis and prognosis of the intellectual disability. Overall, serum proteome of ID patients provides valuable information of proteins/pathways that are altered during ID progression.

Phenotypic and genetic analysis of a Chinese pedigree affected with type 1 Otopalatodigital syndrome

To analyze the clinical phenotype and genetic basis of a Chinese pedigree affected with Otopalatodigital syndrome type 1 (OPD1). A pedigree which was evaluated at the Department of Endocrinology, General Hospital of the Central Theater Command on December 3, 2020 was selected as the study subject. Clinical phenotype and genetic features of the proband were analyzed. Whole exome sequencing was employed to screen for genetic variants in the proband, and Sanger sequencing was used to verify the candidate variants in the proband's mother, uncle, maternal aunt, and paternal aunt. Pathogenicity analysis was also conducted for the candidate variants. The proband, a 16-year-old male, had shown distinctive facial features including mildly prominent eyebrows, down-slanting palpebral fissures, hypertelorism, and depressed nasal bridge. Additionally, he had clubbing of bilateral thumbs and big toes, and central type diabetes insipidus. Genetic sequencing revealed that he has harbored a heterozygous c.586C>T (p.R196W) missense variant of the FLNA gene (NM_001110556.2), which was also carried by his mother and uncle. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), this variant was classified as likely pathogenic (PM1+PM2_Supporting+PP2+PP3+PS4 Supporting). The heterozygous c.586C>T (p.R196W) variant of the FLNA gene probably underlay the pathogenesis in this OPD1 family. The central type diabetes insipidus in the proband may represent a newly discovered phenotype of OPD1. Above finding has contributed crucial information for the comprehensive understanding of the clinical manifestations and pathogenic mechanisms of OPD1.

Role of Filamin A in Growth and Migration of Breast Cancer-Review.

Despite ongoing research in the field of breast cancer, the morbidity rates indicate that the disease remains a significant challenge. While patients with primary tumors have relatively high survival rates, these chances significantly decrease once metastasis begins. Thus, exploring alternative approaches, such as targeting proteins overexpressed in malignancies, remains significant. Filamin A (FLNa), an actin-binding protein (ABP), is involved in various cellular processes, including cell migration, adhesion, proliferation, and DNA repair. Overexpression of the protein was confirmed in samples from patients with numerous oncological diseases such as prostate, lung, gastric, colorectal, and pancreatic cancer, as well as breast cancer. Although most researchers concur on its role in promoting breast cancer progression and aggressiveness, discrepancies exist among studies. Moreover, the precise mechanisms through which FLNa affects cell migration, invasion, and even cancer progression remain unclear, highlighting the need for further research. To evaluate FLNa's potential as a therapeutic target, we have summarized its roles in breast cancer.

FLNA overexpression promotes papillary thyroid cancer aggression via the FAK/AKT signaling pathway.

Filamin A (FLNA) is a member of the filamin family and has been found to be critical for the progression of several cancers. However, its biological function in papillary thyroid cancer (PTC) remains largely unexplored. Data from The Cancer Genome Atlas (TCGA) databases were utilized to analyze the FLNA expression level and its influence on the clinical implications of patients with PTC. Gene Expression Omnibus (GEO) and qRT-PCR was used to verify the expression levels of FLNA in PTC. Kaplan-Meier survival analysis was conducted to evaluate the prognostic value of FLNA in PTC. Transwell assays and wound healing were performed to examine the biological function of FLNA knockdown in PTC cells. Gene set enrichment analysis (GSEA) and Western blotting were conducted to investigate the potential mechanisms underlying the role of FLNA in PTC progression. In addition, the relationship between FLNA expression and the tumor immune microenvironment (TME) in PTC was explored. FLNA was significantly upregulated in PTC tissues. High expression levels of FLNA was correlated with advanced TNM stage, T stage, and N stage, as well as poor disease-free interval (DFI) and progression-free interval (PFI) time in PTC patients. Moreover, we found that FLNA knockdown inhibited the migration and invasion of PTC cells. Mechanistically, FLNA knockdown inhibited epithelial-mesenchymal transition (EMT) in PTC and affected the activation of the FAK/AKT signaling pathway. In addition, FLNA expression was associated with TME in PTC. FLNA may be regarded as a new therapeutic target for PTC patients.

Curcumin suppresses the malignant phenotype of laryngeal squamous cell carcinoma through downregulating E2F1 to inhibit FLNA.

Curcumin is a kind of polyphenol substance extracted from the rhizome of Curcuma longa. Because of its good biological activity and pharmacological effects, it has been used in anti-tumor research. The aim of this study was to investigate the anti-cancer mechanism of curcumin on laryngeal squamous cell carcinoma (LSCC). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to check the expression level of transcription factor E2F1 (E2F1) and filamin A (FLNA) mRNA. E2F1 and FLNA protein and proliferation-associated protein were detected through western blot. Cell viability was showed by MTT assay, and flow cytometry was used to exhibit cell cycle distribution and cell apoptosis. Tube formation assay was used to detect the angiogenesis ability of cells. Transwell was used as a method to observe cell migration and invasion. The online website JASPAR predicted the binding site of E2F1 and FLNA promoter, and chromatin immunoprecipitation (ChIP) and dual-luciferase report experiment verified the combination. Curcumin treatment made LSCC cells viability reduce, cell cycle retardant, angiogenesis decrease, metastasis inhibition and apoptosis increase. And curcumin treatment could downregulate the expression of E2F1, and E2F1 overexpression would reverse the influence of curcumin treatment in LSCC cells. Moreover, E2F1 could bind to FLAN promoter and promote FLNA expression. The expression level of FLNA was higher in LSCC tissue and cells compared with normal tissue and cells. E2F1 knockdown inhibited malignant phenotype of LSCC cells, which would be reversed by FLNA addition. In addition, FLNA had high level in LSCC tissue and cells. Curcumin regulated FLNA expression via inhibiting E2F1. Finally, in vivo assay showed that curcumin inhibition restrained LSCC tumor formation. Curcumin downregulated FLNA expression through inhibiting E2F1, thereby suppressing the malignant phenotype and angiogenesis of LSCC cells, which was a new regulatory pathway in LSCC.

Abstract 349: The role of RELTfms and FLNA in human cancer and cellular apoptosis

Abstract Receptor Expressed in Lymphoid Tissues (RELT) is a Tumor Necrosis Factor Receptor family member implicated in several cancers. RELL1 and RELL2 (RELT-Like 1 and 2) are RELT homologs that bind RELT; the three proteins are collectively referred to as RELT family members (RELTfms). We sought to evaluate the role of the OXSR1 kinase and actin-binding protein Filamin A (FLNA) in modulating RELT-induced apoptosis of cancer cells. We also assessed RELTfm expression in human breast and lung cancer biopsies and their ability to sensitize breast cancer cells to chemotherapeutic agents. Methods: Empty vector or expression plasmids for RELTfms were transiently transfected into MDA-MB-231 (231) breast cancer cells with TransfeX reagent. Cell death was assessed by morphology assays and ATP luciferase assays. Apoptosis of 231 cells was assessed by Annexin V/PI staining using Flow cytometry (FC). Immunohistochemistry (IHC) was used to assess RELT expression in human breast and lung cancer biopsies. IHC and western blotting were utilized to determine RELT cellular localization. Results: All three RELLfms were co-immunoprecipitated by a C-terminal fragment of FLNA. RELT overexpression induced death in 231 cells, and this effect was increased with co-transfection of a FLNA S215A mutant, an important phosphorylation site that protects FLNA from cleavage. 231s transfected with RELT and RELL2 demonstrated increased Annexin V/PI signal in comparison to vector control, demonstrating that these RELTfms induce death via an apoptotic pathway. Co-transfection of a mutated plasmid for the OXSR1 kinase did not abrogate RELT-induced apoptosis. A RELT construct with a mutated binding site for the OXSR1 kinase induced apoptosis to a similar extent as wild-type RELT. An increase in doxorubicin-induced apoptosis was observed when 231 cells were transfected with RELL2 versus vector control. IHC results showed increased RELT expression in malignant breast cancer biopsies compared to patient-matched benign tissue. Interestingly, RELT was localized in the nucleus of some malignant lung cancer biopsies, and western blot analysis indicates that RELT translocates to the nucleus and interacts with chromatin in 231 cells. Conclusions: Collectively, these results demonstrate that RELTfms induce apoptosis of breast cancer cells, and potentially increase the sensitivity of breast cancer cells to chemotherapeutic agents. Furthermore, this work enhances our understanding of the interaction between RELT and FLN, a protein that is implicated in many cancers, including breast cancer. Phosphorylation by OXSR1 was previously shown to be required for RELT to activate the p38 pathway, yet the OXSR1 kinase is not required for RELT-induced death. RELT expression is enhanced in breast cancer biopsies, and interestingly, RELT can localize to the nucleus in cancerous cells. Collectively, these findings significantly enhance our understanding of RELTfms and cancer. Citation Format: Emily Chou, Esther Chang, Ihab Abed, Ashley Christensen, Kailey Nguyen, Anusri Yanumula, Yennie Shyu, Alyssa Abram, Jessa Alcaide, Gianne Cusick, Maryann Batiste, Yihui Shi, Eslam Mohammed, John Cusick. The role of RELTfms and FLNA in human cancer and cellular apoptosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 349.

Abstract 3751: Diagnostic assessment of Filamin A (FLNA) as a serum biomarker for identification of benign prostatic hyperplasia vs aggressive prostate cancer in a prospective Mexican cohort

Abstract Prostate cancer (PCa) exhibits a significant health risk to aging men, in which effective diagnosis of high gleason (Gleason &amp;gt;7) cancers is of critical need. Currently, the main screening tool utilized for detection of prostate cancer is prostate specific antigen (PSA), however, PSA exhibits limited utility in men with benign prostatic hyperplasia (BPH) due to inherent elevated PSA as the result of an enlarged prostate, resulting in increasing unnecessary biopsies. In Mexico, there is currently a higher incidence of aggressive PCa due to the risk within the overall population as well as the need for increased screening tools. Since, there is a critical unmet need to evaluate novel PCa diagnostic test that could serve as a reflex test within the screening paradigm, we evaluated the recently developed test, pSTATEdx, which measures the cleaved portion of Filamin A (FLNA) via IP-MRM mass spectrometry in conjunction with the patients age, to determine the overall risk of aggressive prostate cancer. In the current study, we analyzed a prospective cohort from Mexico City and Guadalajara evaluating 34 BPH and 44 PCa in men exhibiting symptoms with PSA levels between 4-10 ng/mL, who were all referred for 12 core prostate biopsies due to suspicion of prostate cancer. Additionally, we assessed 41 non-diseased men as controls who had PSA below 1.5 ng/mL, who were not assessed further. Comparison of non-diseased controls with BPH/PCa men exhibited an AUC of 0.99, PPV 0.96, NPV 0.89, OR 118, and P value 2 e-20, thus demonstrating that pSTATEdx had significant utility in assessing prostate health independent of PSA. In comparison with previously published data, FLNA mean levels were 24 ng/mL in previously published American study cohort and 55 ng/mL in the Mexican BPH/PCa cohort with a P value of &amp;lt;0.001. Assessment of patient populations revealed that there was superior diagnostic performance of FLNA for patients between PSA 4-7, which represents an increased unmet need for biopsy decision support. Analysis of BPH compared to all PCa exhibited a sensitivity of 0.94 and specificity of 0.53, PPV 0.64, NPV of 0.91, and OR of 16.4. Diagnostic analysis of BPH compared to high gleason PCa exhibited a sensitivity of 1, specificity of 0.21, PPV 0.38, NPV of 1, and OR of inf in this pilot study. This assessment revealed promising insight that aggressive PCa was not missed using pSTATEdx. pSTATEdx demonstrated diagnostic utility in prevention of unnecessary biopsies in the Mexican population as a reflex test to those patients with PSA levels between 4-7 as well as demonstrated that aggressive prostate cancers were not missed with the risk score. Additional studies are planned in the future to expand the utility of pSTATEdx in Latin America. Citation Format: Arturo Rodriguez, Arturo Mendoza, Matthew Rosenburg, José de J. Castaneda, Alejandro A. Melgar, Bernardo Ciseros, Adrian G. Gangemi, Nischal M. Chand, Poornima Tekumalla, Greg Miller, Anjan Thakurta, Diego Banuelos, Juan J. Real, Diego A. Joya, Alejandro Romero, Juan D. Farias, Eduardo Cabeza, Hector H. Remess, Julio J. Delgado, Hector M. Sanchez, Ignacio Barragan, Mabel Rodriguez, Barbara Garcia, David A. Sanchez, Juan Izquierdo, Elizabeth M. Lopez, Juan Hanao, Jeronimo G. Frusch, Niven R. Narain, Michael A. Kiebish. Diagnostic assessment of Filamin A (FLNA) as a serum biomarker for identification of benign prostatic hyperplasia vs aggressive prostate cancer in a prospective Mexican cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3751.

The Role of Mechanotransduction in Contact Inhibition of Locomotion and Proliferation.

Contact inhibition (CI) represents a crucial tumor-suppressive mechanism responsible for controlling the unbridled growth of cells, thus preventing the formation of cancerous tissues. CI can be further categorized into two distinct yet interrelated components: CI of locomotion (CIL) and CI of proliferation (CIP). These two components of CI have historically been viewed as separate processes, but emerging research suggests that they may be regulated by both distinct and shared pathways. Specifically, recent studies have indicated that both CIP and CIL utilize mechanotransduction pathways, a process that involves cells sensing and responding to mechanical forces. This review article describes the role of mechanotransduction in CI, shedding light on how mechanical forces regulate CIL and CIP. Emphasis is placed on filamin A (FLNA)-mediated mechanotransduction, elucidating how FLNA senses mechanical forces and translates them into crucial biochemical signals that regulate cell locomotion and proliferation. In addition to FLNA, trans-acting factors (TAFs), which are proteins or regulatory RNAs capable of directly or indirectly binding to specific DNA sequences in distant genes to regulate gene expression, emerge as sensitive players in both the mechanotransduction and signaling pathways of CI. This article presents methods for identifying these TAF proteins and profiling the associated changes in chromatin structure, offering valuable insights into CI and other biological functions mediated by mechanotransduction. Finally, it addresses unanswered research questions in these fields and delineates their possible future directions.