Fibulin-3 Research Articles

GSK3 inhibition reduces ECM production and prevents age-related macular degeneration-like pathology.

Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD) is an age-related macular degeneration-like (AMD-like) retinal dystrophy caused by an autosomal dominant R345W mutation in the secreted glycoprotein, fibulin-3 (F3). To identify new small molecules that reduce F3 production in retinal pigmented epithelium (RPE) cells, we knocked-in a luminescent peptide tag (HiBiT) into the endogenous F3 locus that enabled simple, sensitive, and high-throughput detection of the protein. The GSK3 inhibitor, CHIR99021 (CHIR), significantly reduced F3 burden (expression, secretion, and intracellular levels) in immortalized RPE and non-RPE cells. Low-level, long-term CHIR treatment promoted remodeling of the RPE extracellular matrix, reducing sub-RPE deposit-associated proteins (e.g., amelotin, complement component 3, collagen IV, and fibronectin), while increasing RPE differentiation factors (e.g., tyrosinase, and pigment epithelium-derived factor). In vivo, treatment of 8-month-old R345W+/+ knockin mice with CHIR (25 mg/kg i.p., 1 mo) was well tolerated and significantly reduced R345W F3-associated AMD-like basal laminar deposit number and size, thereby preventing the main pathological feature in these mice. This is an important demonstration of small molecule-based prevention of AMD-like pathology in ML/DHRD mice and may herald a rejuvenation of interest in GSK3 inhibition for the treatment of retinal degenerative diseases, including potentially AMD itself.

A spectrum of clinically-identified cysteine mutations in fibulin-3 (EFEMP1) highlight its disulfide bonding complexity and potential to induce stress response activation.

Fibulin-3 (FBLN3), also known as EFEMP1, is a secreted extracellular matrix (ECM) glycoprotein that contains forty cysteine residues. These cysteines, which are distributed across one atypical and five canonical calcium-binding epidermal growth factor (EGF) domains, are important for regulating FBLN3 structure, secretion, and presumably function. As evidence of this importance, a rare homozygous p.C55R mutation in FBLN3 negates its function, alters disulfide bonding, and causes marfanoid syndrome. Additional studies suggest that heterozygous premature stop codon mutations in FBLN3 may also cause similar, albeit less severe, connective tissue disorders. Interestingly, a series of twenty-four cysteine mutations in FBLN3 have been identified in the human population and published in the Clinical Variation (ClinVar) and gnomAD databases. We tested how seven of these cysteine mutants (five loss-of-cysteine variants: C42Y, C190R, C218R, C252F, and C365S, two gain-of-cysteine variants: R358C, Y369C) and two newly developed mutations (G57C and Y397C) altered FBLN3 secretion, disulfide bonding, MMP2 zymography, and stress response activation Surprisingly, we found a wide variety of biochemical behaviors: i) loss-of-cysteine variants correlated with an increased likelihood of disulfide dimer formation, ii) N-terminal mutations were less likely to disrupt secretion, and were less prone to aggregation, iii) in contrast to wild-type FBLN3, multiple, but not all variants failed to induce MMP2 levels in cell culture, and iv) C-terminal mutations (either loss or gain of cysteines) were more prone to significant secretion defects, intracellular accumulation/misfolding, and stress response activation. These results provide molecular and biochemical insight into FBLN3 folding, secretion, and function for many cysteine mutations found in the human population, some of which may increase the likelihood of subclinical connective tissue or other FBLN3-associated haploinsufficiency diseases.

Abstract 3937: Investigating the role of fibulin 3 in pancreatic tumorigenesis

Abstract Pancreatic ductal adenocarcinoma (PDA) is a highly lethal malignancy with a five-year survival rate of less than 11%, making it one of the deadliest cancers. Notably, 95% of PDA cases exhibit KRAS mutations, contributing to highly dysregulated cell signaling networks. Despite extensive research into the interplay of various oncogenic pathways in pancreatic tumorigenesis, targeted therapies against these signaling networks have displayed modest efficacy, with most patients rapidly developing therapeutic resistance. Recent studies highlight the significance of the carbohydrate antigen 19-9 (CA19-9) as a functional biomarker linked to disease progression and resistance. However, understanding the detailed functions of CA19-9-modified proteins in PDA has been limited due to the lack of adequate models for synthesizing CA19-9. To address this challenge, we have developed unique mouse and 3D organoid culture models capable of producing CA19-9. CA19-9 elevation in mice with KRAS-mutations results in an aggressive PDA phenotype through increased tumor proliferation and microenvironment (TME) remodeling. Furthermore, our research has identified Fibulin 3 (FBLN3), an extracellular matrix glycoprotein, as a secreted, CA19-9-modified protein that stimulates tumorigenesis. In this study, we found that FBLN3 not only facilitates tumor proliferation but also drives epithelial-mesenchymal transition (EMT) and promotes STAT3 pathways activation in the CA19-9pos, KRAS-mutant PDA organoids. Additionally, in both CA19-9pos, KRAS-mutant PDA mouse models and human PDA, FBLN3 is expressed by cancer-associated fibroblasts (CAFs), suggesting its role in TME remodeling. These findings have significant implications for providing novel insights into PDA biology and paracrine signaling mechanisms, identifying FBLN3 as a potential therapeutic target for the improved treatment of this devastating disease. Citation Format: Hyemin Song, Jasper Hsu, Xiaoxue Lin, Satoshi Ogawa, Vasiliki Pantazopoulou, Kristina Peck, Chelsea Bottomley, Shira Okhovat, McKenna Stamp, Kassidy Curtis, Jeffrey D. Esko, Dannielle D. Engle. Investigating the role of fibulin 3 in pancreatic tumorigenesis [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 3937.

Prognostic value of midkine, syndecan-1, hyaluronan synthase-2, sestrin-1, laminin subunit alpha-4 and fibulin-3 for malignant pleural mesothelioma.

The prognosis of malignant pleural mesothelioma (MPM) is poor, with a limited survival time. In this study, we aimed to examine expression levels of genes selected from relevant literature and to utilize in silico methods to determine genes whose expression could reflect the prognosis of patients with MPM by ex-vivo validation experiments. The study group consisted of 54 MPM patients treated with chemotherapy. Expression of 6 genes - midkine (MDK), syndecan-1 (SDC1), hyaluronan synthase-2 (HAS2), sestrin-1 (SESN1), laminin subunit alpha-4 (LAMA4), and fibulin-3 (FBLN3) - was examined by qPCR in tumor tissues. Sestrin-1 and LAMA4 were identified using an in house R-based script: Unsupervised Survival Analysis Tool. Midkine, SDC1, HAS2, and FBLN3 were selected from current literature. We used two housekeeping genes, i.e. glucose-6-phosphate dehydrogenase and TATA-box binding protein, as controls. Of the patients, 43 (79.6%) had epithelioid mesothelioma. The median survival for all patients was 10 (±1.2 SE) months (95% CI: 7.7-12.3). In multivariate analyses, MDK (p = 0.007), HAS2 (p = 0.008) and SESN1 (p = 0.014) expression levels were related to survival time in the whole group. In epithelioid type MPM patients, MDK (p = 0.014), FBLN3 (p = 0.029), HAS2 (p = 0.014) and SESN1 (p = 0.045) expression was related to survival time in multivariate analyses. High HAS2 and SESN1 expressions and low MDK are potential biomarkers of good prognosis in MPM. High HAS2 and SESN1 expression and low MDK and FBLN3 can also be utilized as biomarkers of good prognosis for epithelioid MPM. Those results should be further investigated in sera, plasma, and pleural effusions.

Clinically-identified C-terminal mutations in fibulin-3 are prone to misfolding and destabilization

Distinct mutations in the secreted extracellular matrix protein, fibulin-3 (F3), have been associated with a number of ocular diseases ranging from primary open angle glaucoma to cuticular age-related macular degeneration to a rare macular dystrophy, Malattia Leventinese (ML). The R345W F3 mutation that causes ML leads to F3 misfolding, inefficient secretion and accumulation at higher intracellular steady state levels in cultured cells. Herein, we determined whether fifteen other clinically-identified F3 mutations also led to similar levels of misfolding and secretion defects, which might provide insight into their potential pathogenicity. Surprisingly, we found that only a single F3 variant, L451F, presented with a significant secretion defect (69.5 ± 2.4% of wild-type (WT) F3 levels) and a corresponding increase in intracellular levels (226.8 ± 25.4% of WT F3 levels). Upon follow-up studies, when this conserved residue (L451) was mutated to a charged (Asp or Arg) or bulky (Pro, Trp, Tyr) residue, F3 secretion was also compromised, indicating the importance of small side chains (Leu, Ala, or Gly) at this residue. To uncover potential inherent F3 instability not easily observed under typical culture conditions, we genetically eliminated the sole stabilizing N-linked glycosylation site (N249) from select clinically-identified F3 mutants. This removal exacerbated R345W and L451F secretion defects (19.8 ± 3.0% and 12.4 ± 1.2% of WT F3 levels, respectively), but also revealed a previously undiscovered secretion defect in another C-terminal variant, Y397H (42.0 ± 10.1% of WT F3 levels). Yet, glycan removal did not change the relative secretion of the N-terminal mutants tested (D49A, R140W, I220F). These results highlight the uniqueness and molecular similarities between the R345W and L451F variants and also suggest that previously identified disease-associated mutations (e.g., R140W) are indistinguishable from WT with respect to secretion, hinting that they may lead to disease by an alternative mechanism.

Fibulin-3 knockout mice demonstrate corneal dysfunction but maintain normal retinal integrity.

Fibulin-3 (F3) is an extracellular matrix glycoprotein found in basement membranes across the body. An autosomal dominant R345W mutation in F3 causes a macular dystrophy resembling dry age-related macular degeneration (AMD), whereas genetic removal of wild-type (WT) F3 protects mice from sub-retinal pigment epithelium (RPE) deposit formation. These observations suggest that F3 is a protein which can regulate pathogenic sub-RPE deposit formation in the eye. Yet the precise role of WT F3 within the eye is still largely unknown. We found that F3 is expressed throughout the mouse eye (cornea, trabecular meshwork (TM) ring, neural retina, RPE/choroid, and optic nerve). We next performed a thorough structural and functional characterization of each of these tissues in WT and homozygous (F3-/-) knockout mice. The corneal stroma in F3-/- mice progressively thins beginning at 2 months, and the development of corneal opacity and vascularization starts at 9 months, which worsens with age. However, in all other tissues (TM, neuralretina, RPE, and optic nerve), gross structural anatomy and functionality were similar across WT and F3-/- mice when evaluated using SD-OCT, histological analyses, electron microscopy, scotopic electroretinogram, optokinetic response, and axonal anterograde transport. The lack of noticeable retinal abnormalities in F3-/- mice was confirmed in a human patient with biallelic loss-of-function mutations in F3. These data suggest that (i) F3 is important for maintaining the structural integrity of the cornea, (ii) absence of F3 does not affect the structure or function of any other ocular tissue in which it is expressed, and (iii) targeted silencing of F3 in the retinaand/or RPE will likely be well-tolerated, serving as asafe therapeutic strategy for reducing sub-RPE deposit formation in disease. KEY MESSAGES: • Fibulins are expressed throughout the body at varying levels. • Fibulin-3 has a tissue-specific pattern of expression within the eye. • Lack of fibulin-3 leads to structural deformities in the cornea. • The retina and RPE remain structurally and functionally healthy in the absence of fibulin-3 in both mice and humans.

FBLN3 inhibited the invasion and metastasis of colorectal cancer through the AKT/mTOR pathway.

Fibulin-3(FBLN3) levels are different in different types of cancers. We found that fibulin-3 was downregulated in colorectal (CRC) cells, particularly in the SW480 cell line. By comparison, transfecting SW480 cells with a lentivirus overexpressing fibulin-3 RNA could inhibit proliferation, induce G1/S arrest, and promote cell apoptosis. Fibulin-3 overexpression further suppressed the invasion and metastasis of CRC. These effects were regulated through the AKT/mTOR signaling pathway.

Abstract 4657: LOX and ZFPM2 as novel diagnostic biomarkers for malignant pleural mesothelioma

Abstract Malignant pleural mesothelioma (MPM) is a rare, aggressive cancer being developed on outlayer of lung tissues and caused by mostly occupational exposure to asbestos. Poor prognosis needs to develop therapeutic drug as well as early diagnostic biomarker. Currently, mesothelin (MSLN), osteopontin (OPN), and fibulin 3 (FBLN3) have been reported as potential diagnostic biomarkers for MPM. In this study, we first performed bioinformatics analysis for public database to find diagnostic biomarkers for MPM. From the analysis using Cancer Cell Line Encyclopedia (CCLE) and Gene Expression Omnibus (GEO) databases, included were 7 genes involving LOX, LOXL1, LOXL2, ZFPM2, THBS2, SULF1, CDH11 identified as potential diagnostic biomarkers. These genes showed a similar diagnostic ability to FBLN3 or MSLN as MPM biomarker candidates. Further molecular approach using quantitative real-time polymerase chain reaction (QPCR) confirmed the higher mRNA expression of these candidates in MPM cell lines and patient samples. Moreover, two particular genes, LOX and ZFPM, showed MPM specific patterns of mRNA expression that were further confirmed in protein level by western blot assay. Together with biological approach, biostatistical analysis of receiver operating characteristic (ROC) analysis using the GEO database revealed significantly higher diagnostic potential of LOX and ZFPM2 genes compared to the FBLN3, one of the best diagnostic biomarkers currently reported. From this study, we believe these genes together with FBLN3 and MSLN would become novel potential biomarker candidates for MPM diagnosis. Citation Format: Minkyu Kim, Hyun-Won Kim, Soon-Hee Jung, Sung Soo Oh, Yangsik Jeong, Jong-Whan Choi. LOX and ZFPM2 as novel diagnostic biomarkers for malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4657. doi:10.1158/1538-7445.AM2017-4657

Mapping wild-type and R345W fibulin-3 intracellular interactomes

Fibulin-3 (F3) is an important, disulfide-rich, extracellular matrix glycoprotein that has been associated with a number of diseases ranging from cancer to retinal degeneration. An Arg345Trp (R345W) mutation in F3 causes the rare, autosomal dominant macular dystrophy, Malattia Leventinese. The purpose of this study was to identify and validate novel intracellular interacting partners of wild-type (WT) and R345W F3 in retinal pigment epithelium cells. We used stable isotope labeling by amino acids in cell culture (SILAC) to generate ‘heavy’ and ‘light’ isotopically labeled ARPE-19 cell populations which were subsequently infected with adenovirus encoding for FLAG-tagged WT or R345W F3. After immunoprecipitation, interacting proteins were identified by multidimensional protein identification technology (MudPIT). We identified sixteen new intracellular F3 interacting partners, the vast majority of which are involved in protein folding and/or degradation in the endoplasmic reticulum (ER). Eight of these interactions (ANXA5, ERdj5, PDIA4, P4HB, PDIA6, RCN1, SDF2L1, and TXNDC5) were verified at the western blotting level. These F3 interactome results can serve as the basis for pursuing targeted genetic or pharmacologic approaches in an effort to alter the fate of either WT or mutant F3.

Abstract 692: Identifying genes that regulate bladder cancer progression and invasion

Abstract Transitional cell carcinoma (TCC) is the most common type of bladder cancer and can be categorized as either non-muscle invasive (Ta-T1) or muscle invasive (≥T2). Approximately 50% of bladder cancers are T1 at initial diagnosis; however, the recurrence rate for these tumors is high and they may progress into T2. In this study, we aimed to determine if there are specific gene expression differences between T1 vs. T2 bladder cancer that can help identify key regulators in bladder cancer progression and invasion. T1 and T2 bladder cancer tissues were subjected to RNA-Seq to evaluate for differences among these stages. Additionally, the Oncomine database was examined to further narrow down potential candidates that differentiate T1 from T2. These efforts led to the identification of an extracellular matrix glycoprotein, fibulin-3 (FBLN3), as being highly expressed in T2 compared to T1 tissues. To validate these findings, FBLN3 expression was measured using qRT-PCR from formalin fixed and paraffin embedded tissues from patient bladder samples ranging from stages Ta-T4. These studies confirmed that FBLN3 expression was elevated in muscle-invasive compared to non-muscle invasive bladder cancer. Consistent with these findings, FBLN3 expression level correlated with the invasive ability of several bladder cancer cell lines. Specifically, FBLN3 expression was determined using both qRT-PCR and western blotting amongst the T24, UMUC-13, UMUC-3, RT4, and 5637 bladder cancer cell lines. The most invasive cell lines, T24 and UMUC-13, demonstrated the highest FBLN3 expression. In contrast, the least invasive cells, RT4 and 5637, demonstrated the least FBLN3 expression. To determine a functional role for FBLN3 in bladder cancer invasion, we knocked down or increased FBLN3 expression in bladder cancer cell lines using lentiviral transduction. Knockdown of FBLN3 expression in the T24 and UMUC-13 cells inhibited the invasion and migration of these bladder cancer cells; whereas, FBLN3 overexpression in the 5637 cells promoted the invasiveness of the bladder cancer cells. Furthermore, cell viability and growth rates were not affected by manipulation of FBLN3 expression. Our results indicate that FBLN3 serves as a pro-invasive factor in bladder cancer. These findings suggest that FBLN3 could serve as (1) a biomarker to differentiate T1 from T2 bladder cancers and (2) a promising therapeutic target. Citation Format: Amy L. Han, Brendan Veeneman, Scott A. Tomlins, Evan T. Keller. Identifying genes that regulate bladder cancer progression and invasion. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 692.

Malattia Leventinese/Doyne Honeycomb Retinal Dystrophy: Similarities to Age-Related Macular Degeneration and Potential Therapies.

Fibulin-3 (F3) is a secreted, disulfide-rich glycoprotein which is expressed in a variety of tissues within the body, including the retina. An Arg345Trp (R345W) mutation in F3 was identified as the cause of a rare retinal dystrophy, Malattia Leventinese/Doyne Honeycomb Retinal Dystrophy (ML/DHRD). ML/DHRD shares many phenotypic similarities with age-related macular degeneration (AMD). The most prominent feature of ML/DHRD is the development of radial or honeycomb patterns of drusen which can develop as early as adolescence. Two independent mouse models of ML/DHRD show evidence of complement activation as well as retinal pigment epithelium (RPE) atrophy, strengthening the phenotypic connection with AMD. Because of its similarities with AMD, ML/DHRD is receiving increasing interest as a potential surrogate disease to study the underpinnings of AMD. This mini-review summarizes the current knowledge of F3 and points toward potential therapeutic strategies which directly or indirectly target cellular dysfunction associated with R345W F3.

Elastogenesis-related gene polymorphisms and the risk of pelvic organ prolapse development

Pelvic organ prolapse (POP) represents a urologic and gynecological disease, the development of which is governed both by environmental and genetic factors. We describe the results of our association study of polymorphic variants of genes involved in the assembly of elastic fibrils, namely, the lysyl oxidase protein 1 (LOXL1) and fibulin-3 (FBLN3) genes. We revealed an association of the rs2304719-T allele and rs2165241 (C)-rs2304719(T)-rs893821(T) haplotype of the LOXL1 gene with an increased risk of POP development, as well as a weak association with the disease of the rs3791660-C allele and the rs3791679(T)- rs1367228(A)-rs3791660(C)-rs2033316(A) haplotype of the FBLN3 gene.

Fibulin-3 levels in malignant pleural mesothelioma are associated with prognosis but not diagnosis.

Background:Fibulin-3 (FBLN3) was recently presented as a promising novel biomarker for malignant pleural mesothelioma (MPM), warranting independent validation studies.Methods:ELISA was used to measure cellular and secreted FBLN3 in cell lines, in plasma of xenograft tumour-bearing mice, in plasma from two independent series of MPM and non-MPM patients and in pleural fluid from a third series. Diagnostic and prognostic potential of FBLN3 was assessed by receiver operating characteristics curve analysis and Kaplan–Meier method, respectively.Results:FBLN3 was expressed in all MPM and benign mesothelial cell lines tested, and a correlation was observed between cellular protein expression and secreted levels. Human FBLN3 was detectable in plasma of tumour-bearing mice, suggesting that MPM cells contribute to levels of circulating FBLN3. Plasma FBLN3 was significantly elevated in MPM patients from the Sydney cohort, but not the Vienna cohort, but the diagnostic accuracy was low (63%, (95% CI: 50.1–76.4) and 56% (95% CI: 41.5–71.0), respectively). Although FBLN3 levels in pleural effusions were not significantly different between cases and controls, FBLN3 levels in pleural effusion fluid were found to be independently associated with prognosis (hazard ratio of 9.92 (95% CI: 2.14–45.93)).Conclusions:These data confirm the potential prognostic value of pleural effusion FBLN3, but question the diagnostic value of this protein in MPM patients.

Differential tolerance of ‘pseudo-pathogenic’ tryptophan residues in calcium-binding EGF domains of short fibulin proteins

An Arg345Trp (R345W) mutation in the last canonical calcium-binding epidermal growth factor (cbEGF) domain of fibulin-3 (F3) causes the rare macular dystrophy, Malattia Leventinese (ML). In cell culture studies, this mutation leads to inefficient F3 secretion and higher intracellular steady state levels, likely due to F3 disulfide bonding and/or protein folding problems. However, how the R345W mutation actually causes ML is still largely unknown. Herein we tested whether the introduction of analogous, ‘pseudo-pathogenic’ tryptophan mutations immediately after the bn cysteine (bn+1) in other cbEGF domains also caused protein folding/secretion challenges. We found that introduction of tryptophan mutations into each of the four other F3 canonical cbEGF domains caused a significant reduction in protein secretion ranging from 2.7 to 56% of wild-type (WT) F3 levels. Surprisingly, an R185W mutation in the first canonical cbEGF domain of F3 yielded the highest amount of secretion among the F3 tryptophan mutants, and its secretion defect could be rescued to near WT levels (95%) after growth temperature reduction. Interestingly, when similarly positioned tryptophan mutations were introduced into any of the canonical cbEGF domains of the highly homologous protein, fibulin-5 (F5), there was no effect on secretion. In an attempt to make F3 tolerant of tryptophan residues (like F5), we genetically engineered F3 to have a higher sequence homology with F5 by deleting three insert regions present in F3, but not F5. However, deletion of one or more of these regions did not have a beneficial effect on R345W F3 secretion. Overall, these results demonstrate that the introduction of tryptophan residues at the bn+1 position does not universally disrupt cbEGF domain folding and secretion, but that their effect is context dependent, and in this case, uniquely disrupt the folding of canonical cbEGF domains of F3, but not F5.

Genetic ablation of N-linked glycosylation reveals two key folding pathways for R345W fibulin-3, a secreted protein associated with retinal degeneration.

An R345W mutation in the N-glycoprotein, fibulin-3 (F3), results in inefficient F3 folding/secretion and higher intracellular F3 levels. Inheritance of this mutation causes the retinal dystrophy malattia leventinese. N-Linked glycosylation is a common cotranslational protein modification that can regulate protein folding efficiency and energetics. Therefore, we explored how N-glycosylation alters the protein homeostasis or proteostasis of wild-type (WT) and R345W F3 in ARPE-19 cells. Enzymatic and lectin binding assays confirmed that WT and R345W F3 are both primarily N-glycosylated at Asn249. Tunicamycin treatment selectively reduced R345W F3 secretion by 87% (vs. WT F3). Genetic elimination of F3 N-glycosylation (via an N249Q mutation) caused R345W F3 to aggregate intracellularly and adopt an altered secreted conformation. The endoplasmic reticulum (ER) chaperones GRP78 (glucose-regulated protein 78) and GRP94 (glucose-regulated protein 94), and the ER lectins calnexin and calreticulin were identified as F3 binding partners by immunoprecipitation. Significantly more N249Q and N249Q/R345W F3 interacted with GRP94, while substantially less N249Q and N249Q/R345W interacted with the ER lectins than their N-glycosylated counterparts. Inhibition of GRP94 ATPase activity reduced only N249Q/R345W F3 secretion (by 62%), demonstrating this variant's unique reliance on GRP94 for secretion. These observations suggest that R345W F3, but not WT F3, requires N-glycosylation to acquire a stable, native-like structure.

Fibulin-3 negatively regulates ALDH1 via c-MET suppression and increases γ-radiation-induced sensitivity in some pancreatic cancer cell lines

Fibulin-3 (FBLN-3) has been postulated to be either a tumor suppressor or promoter depending on the cell type, and hypermethylation of the FBLN-3 promoter is often associated with human disease, especially cancer. We report that the promoter region of the FBLN-3 was significantly methylated (>95%) in some pancreatic cancer cell lines and thus FBLN-3 was poorly expressed in pancreatic cancer cell lines such as AsPC-1 and MiaPaCa-2. FBLN-3 overexpression significantly down-regulated the cellular level of c-MET and inhibited hepatocyte growth factor-induced c-MET activation, which were closely associated with γ-radiation resistance of cancer cells. Moreover, we also showed that c-MET suppression or inactivation decreased the cellular level of ALDH1 isozymes (ALDH1A1 or ALDH1A3), which serve as cancer stem cell markers, and subsequently induced inhibition of cell growth in pancreatic cancer cells. Therefore, forced overexpression of FBLN-3 sensitized cells to cytotoxic agents such as γ-radiation and strongly inhibited the stemness and epithelial to mesenchymal transition (EMT) property of pancreatic cancer cells. On the other hand, if FBLN3 was suppressed in FBLN-3-expressing BxPC3 cells, the results were opposite. This study provides the first demonstration that the FBLN-3/c-MET/ALDH1 axis in pancreatic cancer cells partially modulates stemness and EMT as well as sensitization of cells to the detrimental effects of γ-radiation.

Differential expression of fibulins in the uterosacral ligaments of women with uterine prolapse

To compare fibulin-3 (FIB-3) and fibulin-5 (FIB-5) expressions in uterosacral ligaments (USL) of women with and without uterine prolapse. USL were sampled in a standardized fashion from women with (n = 8) or without (n = 8) uterine prolapse. Quantitative Real-Time PCR was performed to measure mRNA and immunohistochemistry to assess protein expression. FIB-3 mRNA expression and FIB-3 staining intensity was similar in the USL of women with and without uterine prolapse {[(FIB-3 mean +/- SD mRNA relative units) 0.45 +/- 0.41 vs. 0.46 +/- 0.82, NS] and [Intensity score, median (range), 1(0-1) vs. 1(0-1), NS]}. Both FIB-5 mRNA expression and FIB-5 staining intensity was significantly decreased in USL from women with uterine prolapse compared to women without prolapse {[(FIB-5 mean +/- SD mRNA relative units) 0.07 +/- 0.02 vs. 0.26 +/- 0.20, P = 0.02] and [Intensity score, median (range), 0(0-2) vs. 3(2-3), P = 0.002]}. FIB-5 expression is decreased in USL of women with uterine prolapse.