Clinical significance of loss of Fhl1 expression in human gastric cancer

Honeycomb-Shaped Supermacroporous Adsorbent Integrating Size-Exclusion and Selective Chemisorption Enables High-Efficiency Extraction and Analysis of Exosomes from Plasma

As cell secretions, exosomes play an important role in disease diagnosis, but the extraction of high-purity exosomes from body fluids faces great challenges. To address this issue, this work creates an excellently selective adsorbent by modifying the zwitterionic polymer carrying choline phosphate on the surface of honeycomb-shaped supermacroporous silica, which integrates chemisorption and size-exclusion principles. The results indicate that the supermacropore with a thin pore wall allows exosomes to enter and thereby be adsorbed by the polymer via specific multivalent interaction and, meanwhile, excludes large cell debris and microvesicles. Moreover, the amphiphilic polymer can inhibit the adsorption of coexisting proteins. Taking advantage of these properties, the adsorbent can extract higher purity exosomes in a simpler way over "gold standard" ultracentrifugation and normal adsorbents. Furthermore, the in situ lysis of adsorbed exosomes simplifies the subsequent analysis and enhances the sensitivity. Consequently, 422 proteins are identified in the exosomes extracted from healthy human plasma, which is higher than that obtained by ultracentrifugation. For plasma from colorectal cancer patients, 62 upregulated and 165 downregulated proteins are identified and can be used as potential biomarkers. In conclusion, the adsorbent can serve as a platform for the high-efficiency extraction of exosomes in clinical diagnostic research.

FHL1 as a prognostic biomarker and therapeutic target in acute promyelocytic leukaemia

Acute myeloid leukemia (AML) has a poor prognosis and high heterogeneity. Most cases of leukemias are caused by environmental factors interacting with the cell's genetic material, but treatment is still dominated by cell cycle drugs. Therefore, there is an urgent need to find reliable biomarkers. Based on the Gene Expression Omnibus database, Kaplan-Meier survival analysis and univariate Cox regression analysis were used to select the genes that had the most significant influence on the prognosis of patients with AML. Quantitative real-time PCR and Western blot were used to assess the effects of small interfering RNA transfection and lentiviral interference on the gene's knockout and overexpression, respectively. These method were also used to confirm the expression levels of the FHL1 gene in the HL60 cell line compared to neutrophils.. Cell Counting Kit-8 and flow cytometry were used to detect the effect of high or low expression of FHL1 on cell viability and apoptosis under the influence of cytarabine and daunorubicin. FHL1 was found to be the most prognostic independent biomarker by GSE12417 screening and GSE37642 validation. FHL1 is highly expressed in AML, and knockdown of FHL1 can increase the sensitivity of AML cells to cytarabine and daunorubicin. FHL1 may play a role as a potential molecular marker and therapeutic target for predicting poor prognosis of AML and for direct treatment (chemotherapy).

Role of four and a half LIM domain protein 1 in tumors (Review)

As a cytoskeletal protein, the four and a half LIM domain protein 1 (FHL1) is widely expressed in various cells, particularly skeletal and cardiac muscle cells. FHL1 is involved in the development of the skeletal muscle and myocardium, regulations of gene transcription and thyroid function, and other physiological processes. Its expression is closely related to numerous diseases, such as skeletal muscle disease and viral infections. With the advances in research, the role of FHL1 in the development of tumors is also being revealed. The mechanism of FHL1 in the regulation of tumor growth is complex and is becoming a research focus. It is also expected to become a potential target for tumor therapy. Therefore, the present article reviewed the progress in research on the role of FHL1 in cancer.

Four and a half LIM domains protein 1 can be as a double-edged sword in cancer progression

Four and a half LIM domains protein 1 (FHL1), as the name suggests, contains four and a half LIM domains capable of interacting with various molecules, including structural proteins, kinases, and transcriptional machinery. FHL1 contains a zinc-finger domain and performs diverse roles in regulation of gene transcription, cytoarchitecture, cell proliferation, and signal transduction. Several studies have validated the importance of FHL1 in muscle development, myopathy, and cardiovascular diseases. Mutations in the FHL1 gene are associated with various myopathies. Recently, FHL1 was identified as a major host factor for chikungunya virus (CHIKV) infection in both humans and mice. Based on more recent findings over the last decade, FHL1 is proposed to play a dual role in cancer progression. On the one hand, FHL1 expression is suppressed in several cancer types, which correlates with increased metastatic disease and decreased survival. Moreover, FHL1 is reported to inhibit tumor cell growth and migration by associating with diverse signals, such as TGF-β and ER, and therefore considered a tumor suppressor. On the other hand, FHL1 can function as an oncogenic protein that promotes tumor progression upon phosphorylation, reflecting complex roles in cancer. This review primarily focuses on the dual role and underlying mechanisms of action of FHL1 in human cancer progression and its clinical relevance.

Downregulation of FHL1 protein in glioma inhibits tumor growth through PI3K/AKT signaling

Human four-and-a-half LIM domains protein 1 (FHL1) is a member of the FHL protein family, which serves an important role in multiple cellular events by interacting with transcription factors using its cysteine-rich zinc finger motifs. A previous study indicated that FHL1 was downregulated in several types of human cancer and served a role as a tumor suppressive gene. The overexpression of FHL1 inhibited tumor cell proliferation. However, to the best of our knowledge, there is no evidence to confirm whether FHL1 affected glioma growth, and the molecular mechanisms through which FHL1 represses tumor development remain unclear. In the present study, the expression level of FHL1 was determined using immunohistochemical staining in 114 tumor specimens from patients with glioma. The results indicated that FHL1 expression was negatively associated with the pathological grade of gliomas. Furthermore, Kaplan-Meier survival curves demonstrated that the patients with an increased FHL1 expression exhibited a significantly longer survival time, suggesting that FHL1 may be a prognostic marker for glioma. The protein level of FHL1 was relatively increased in the U251 glioma cell line compared with that in the U87 cell line. Therefore, FHL1 was knocked down in U251 by siRNA and overexpressed in U87, and it was identified that FHL1 significantly decreased the activation of PI3K/AKT signaling by interacting with AKT. Further experiments verified that FHL1 inhibited the growth of gliomas in vivo by modulating PI3K/AKT signaling. In conclusion, the results of the present study demonstrated that FHL1 suppressed glioma development through PI3K/AKT signaling.

Long Intergenic Noncoding RNA 00261 Acts as a Tumor Suppressor in Non-Small Cell Lung Cancer via Regulating miR-105/FHL1 Axis

Purpose: Long noncoding RNAs (lncRNAs) have recently received more attention for their roles in tumor progression. LINC00261 was studied in this research to identify how it affects the progression of non-small cell lung cancer (NSCLC).

Methods: Firstly, the expression of LINC00261 in NSCLC cells and paired samples of NSCLC tissue was detected by RT-qPCR. Then, the associations between LINC00261 expression level and clinicopathological characteristics were evaluated. Furthermore, functional assays of cell proliferation, colony formation and transwell, as well as western blot assay, luciferase assay and RNA immunoprecipitation (RIP) assay were conducted. Afterwards, the effects of LINC00261 expression on NSCLC formation and growing were confirmed by in vivo models.

Results: As results, expression of LINC00261 was significantly down-regulated in tumor samples than that in normal samples, which was correlated with the lymphatic metastasis, tumor size, tumor stage as well as patient survival time. Knockdown of LINC00261 inhibited tumor growth and invasion ability in vitro. In addition, miR-105 was identified as a direct target of LINC00261 via mechanism experiments and its expression in tumor tissues negatively correlated to LINC00261 expression. Further experiments found that Four and expression of Half LIM domains 1 (FHL1) was negatively correlated with miR-105 but positively with LINC00261. Moreover, in vivo assays verified the overexpression of LINC00261 could suppress formation of NSCLC and regulate the expression of miR-105/FHL1 axis.

Conclusions: These results indicate that LINC00261 could suppress metastasis and proliferation of NSCLC via suppressing miR-105/FHL1 axis, which may offer a new vision for interpreting the mechanism of NSCLC development.

Overexpression Of hsa-miR-664a-3p Is Associated With Cigarette Smoke-Induced Chronic Obstructive Pulmonary Disease Via Targeting FHL1

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is recognized as a chronic lung disease with incomplete reversible airflow limitation, but its pathophysiology was still not clear. This study aimed at investigating regulatory roles of special miRNA-mRNA axis in COPD development.

METHODS

Differentially expressed miRNAs and downstream mRNAs were screened from the Gene Expression Omnibus (GEO) dataset by using the LIMMA package in R software. Weighted Gene Co-expression Network Analysis (WGCNA) was used to construct a co-expression network for COPD. The correlation of dysregulated miRNA(s) and COPD was analyzed, and miRNAs with significant differences were validated in peripheral blood mononuclear cells (PBMCs) from COPD patients by real-time PCR. Regulatory roles of candidate miRNAs and targeted mRNAs were investigated in vitro study.

RESULTS

Thirteen modules of co-expressed miRNAs and mRNAs were constructed from a selected cohort with WGCNA. Turquoise module with 12 differentially expressed miRNAs and 120 mRNAs was significantly correlated with COPD. The expression of hsa-miR-664a-3p, an upregulated miRNA in the module, was increased both in lung tissue and PBMCs from COPD patients, whereas that targeted four and a half LIM domains 1 (FHL1) gene was decreased and positively correlated with forced expiratory volume in 1 sec (FEV1)/forced vital capacity (FVC%) (r = 0.59, p < 0.01). In vitro, luciferase activity assay revealed FHL1 as a target of hsa-miR-664a-3p and it could be directly downregulated by overexpression of hsa-miR-664a-3p. Furthermore, cigarette smoke extract could increase hsa-miR-664a-3p level and decrease FHL1 level in Beas-2B cells.

CONCLUSION

The present study validated significant upregulation of hsa-miR-664a-3p in COPD patients, and its target gene FHL1 was downregulated and positively correlated with FEV1/FVC%; both hsa-miR-664a-3p and FHL1 could be regulated by cigarette smoke extract. Results of bioinformatic analyses and expanded validation suggest that the axis from hsa-miR-664a-3p to FHL1 might play a key role in cigarette smoke-induced COPD, and the exact mechanism should be confirmed in further studies.

Proteomic analysis of human prostate cancer PC-3M-1E8 cells and PC-3M-2B4 cells of same origin but with different metastatic potential

Prostate cancer (PCa) is the second most frequently diagnosed cancer and the fifth leading cause of death from cancer in men worldwide. Increased understanding of the prostate cancer metastasis mechanisms will help identify more efficient intervention strategies to prevent or treat this deadly disease in the future. To identify the candidate proteins that contribute to metastasis of PCa, isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic analysis was performed to explore differentially expressed proteins between two homologous human prostate cancer cell lines including highly-metastatic PC-3M-1E8 cell line and poorly-metastatic PC-3M-2B4 cell line. Here, a total of 58 proteins were identified to be significantly differentially expressed between PC-3M-1E8 and PC-3M-2B4 cells, which were further verified using real-time quantitative PCR and western blot analysis. The bioinformatic analysis suggested that the differentially expressed proteins, like MMP1 and FHL1, may contribute to the higher metastatic ability of PC-3M-1E8 cells than PC-3M-2B4 cells. In addition, functional analyses proved MMP1’s positive effect on the higher metastatic ability of PC-3M-1E8 cells than PC-3M-2B4 cells. These findings provided a unique resource to specifically reveal the complex molecular regulatory mechanisms underlying the progression of prostate cancer from poorly-metastatic to highly-metastatic stage.

IGF2-derived miR-483-3p associated with Hirschsprung's disease by targeting FHL1

HSCR (Hirschsprung's disease) is a serious congenital defect, and the aetiology of it remains unclear. Many studies have highlighted the significant roles of intronic miRNAs and their host genes in various disease, few was mentioned in HSCR although. In this study, miR-483-3p along with its host gene IGF2 (Insulin-like growth factor 2) was found down-regulated in 60 HSCR aganglionic colon tissues compared with 60 normal controls. FHL1 (Four and a half LIM domains 1) was determined as a target gene of miR-483-3p via dual-luciferase reporter assay, and its expression was at a higher level in HSCR tissues. Here, we study cell migration and proliferation in human 293T and SH-SY5Y cell lines by performing Transwell and CCK8 assays. In conclusion, the knockdown of miR-483-3p and IGF2 both suppressed cell migration and proliferation, while the loss of FHL1 leads to opposite outcome. Furthermore, miR-483-3p mimics could rescue the negative effects on cell proliferation and migration caused by silencing IGF2, while the FHL1 siRNA may inverse the function of miR-483-3p inhibitor. This study revealed that miR-483-3p derived from IGF2 was associated with Hirschsprung's disease by targeting FHL1 and may provide a new pathway to understand the aetiology of HSCR.

Characterization of long non-coding RNAs and MEF2C-AS1 identified as a novel biomarker in diffuse gastric cancer

Previous studies proved that long noncoding RNAs (lncRNAs) play important role in human cancer. However, the knowledge of genome scale expression of lncRNAs and their potential biological function in gastric cancer is still lacking. Next generation RNA sequencing (RNA-seq) was performed on tumor tissues and matched adjacent normal tissues of six diffuse gastric cancer (DGC) patients. Then we performed a comprehensive analysis on lncRNAs and mRNA. Fifty-eight lncRNAs were upregulated and 54 lncRNAs were downregulated in diffuse gastric cancer tissue compared with adjacent tissue. The numbers of up- and downregulated mRNAs were 306 and 161, respectively. In addition, we inferred the function of lncRNAs by construction of a co-expression network for deregulated mRNAs and lncRNAs. Co-expressed genes of MEF2C-AS1 and FENDRR were enriched to RAS and TGF-beta signaling pathway. MEF2C-AS1 and FENDRR expression were re-evaluated by Real-time Quantitative PCR in 42 DGC patients' tumor and normal tissues, and other 46 DGC patents' and 21 healthy controls' plasma. Validation data showed MEF2C-AS1 and FENDRR were significantly downregulated in tumor tissues compared with normal tissues. And decreased FENDRR are associated with aggressive tumor characteristics including more advanced stage (P = .030), poor differentiation (P = .043) and lymphatic metastasis (P = .001). The expression level MEF2C-AS1 was significantly lower in DGC patients' plasma than that in healthy controls' plasma. In gastric cancer cell lines, knock-down of MEF2C-AS1 or FENDRR reduced the protein levels of FAT3, NTN1 and LYVE1 (the co-expressed genes), which were related with gastric cancer cell proliferation and invasion by previous studies. In addition, knock-down of MEF2C-AS1 or FENDRR promoted aggressive tumor behaviors in in-vitro assays. In this study, we provide a valuable resource of lncRNAs which might play important roles in the function of oncogenes or tumor suppressors affecting the development and progression of diffuse gastric cancer.

Genome-wide Analyses on Single Disease Samples for Potential Biomarkers and Biological Features of Molecular Subtypes: A Case Study in Gastric Cancer

Purpose: Based on the previous 3 well-defined subtypes of gastric adenocarcinoma (invasive, proliferative and metabolic), we aimed to find potential biomarkers and biological features of each subtype.

Methods: The genome-wide co-expression network of each subtype of gastric cancer was firstly constructed. Then, the functional modules in each genome-wide co-expression network were divided. Next, the key genes were screened from each functional module. Finally, the enrichment analysis was performed on the key genes to mine the biological features of each subtype. Comparative analysis between each pair of subtypes was performed to find the common and unique features among different subtypes.

Results: A total of 207 key genes were identified in invasive, 215 key genes in proliferative, and 204 key genes in metabolic subtypes. Most key genes in each subtype were unique and new findings compared with that of the existing related researches. The GO and KEGG enrichment analyses for the key genes of each subtype revealed important biological features of each subtype.

Conclusions: For a subtype, most identified key genes and important biological features were unique, which means that the key genes can be used as the potential biomarker of a subtype, and each subtype of gastric cancer might have different occurrence and development mechanisms. Thus, different diagnosis and therapy methods should be applied to the invasive, proliferative and metabolic subtypes of gastric cancer.

Epigenetic analysis of FHL1 tumor suppressor gene in human liver cancer

Liver cancer is one of the most common types of cancer among human malignancies. Four and a half LIM domains 1 (FHL1), as a tumor suppressor gene, is frequently downregulated in multiple types of human cancer. However, the role and specific mechanisms of FHL1 as a tumor suppressor in liver cancer are poorly understood. The present study aimed to investigate the role and associated mechanisms of FHL1 in human liver cancer. The level of FHL1 mRNA in hepatocellular carcinoma (HCC) tissue specimens and cell lines derived from the human liver was determined using reverse transcription polymerase chain reaction and western blot analysis. The association between FHL1 expression and clinicopathological characteristics of patients with liver cancer was analyzed. Western blotting, small interfering RNA (siRNA) and chromatin immunoprecipitation were used to study the expression association of FHL1 and enhancer of zeste homolog 2 (EZH2) in human liver cancer and to explore the regulatory mechanism of FHL1 downregulation. Colony formation and migration assays were performed while FHL1 was overexpressed in Hep3B cells. The results showed that the expression of FHL1 mRNA in tumor tissue decreased, exhibiting a significant difference compared with the adjacent non-cancerous tissue (P<0.05). However, the downregulation of FHL1 was not significantly associated with the sex, age, hepatitis B virus infection status, tumor size, distant metastasis status or level of tumor differentiation of the patients. FHL1 was synergistically silenced by DNA methylation and histone modification, and 3-deanzaneplanocin A (DZNep), an inhibitor of EZH2, which is a histone methyltransferase of the polycomb repressive complex 2, which catalyzes histone H3 lysine 27 tri-methylation (H3K27me3). A significant association between FHL1 and EZH2 expression was identified in the female hepatocellular carcinoma (HCC) samples, but was not in the male HCC samples. FHL1 overexpression and DZNep treatment significantly suppressed the growth and migration of Hep3B cells by restoring FHL1 expression. H3K27me3 was significantly enriched at the FHL1 promoter region, as indicated by a chromatin immunoprecipitation assay, and associated with the epigenetic repression of the FHL1 tumor suppressor gene in HCC cell lines. In conclusion, the present study provides an insight into DNA methylation and EZH2-H3K27me3 epigenetic repression of FHL1 in human liver cancer.

A signature motif in LIM proteins mediates binding to checkpoint proteins and increases tumour radiosensitivity

Tumour radiotherapy resistance involves the cell cycle pathway. CDC25 phosphatases are key cell cycle regulators. However, how CDC25 activity is precisely controlled remains largely unknown. Here, we show that LIM domain-containing proteins, such as FHL1, increase inhibitory CDC25 phosphorylation by forming a complex with CHK2 and CDC25, and sequester CDC25 in the cytoplasm by forming another complex with 14-3-3 and CDC25, resulting in increased radioresistance in cancer cells. FHL1 expression, induced by ionizing irradiation in a SP1- and MLL1-dependent manner, positively correlates with radioresistance in cancer patients. We identify a cell-penetrating 11 amino-acid motif within LIM domains (eLIM) that is sufficient for binding CHK2 and CDC25, reducing the CHK2–CDC25 and CDC25–14-3-3 interaction and enhancing CDC25 activity and cancer radiosensitivity accompanied by mitotic catastrophe and apoptosis. Our results provide novel insight into molecular mechanisms underlying CDC25 activity regulation. LIM protein inhibition or use of eLIM may be new strategies for improving tumour radiosensitivity.

CDC25 phosphatases are important cell cycle regulators. Here, the authors show that the LIM domain-containing proteins (for example, FHL1) induce inhibitory CDC25 phosphorylation resulting in radioresistance and that a specific peptide can increase tumour radiosensitivity by increasing CDC25 activity.

X-linked FHL1 as a novel therapeutic target for head and neck squamous cell carcinoma

To identify X-linked novel tumor suppressors could provide novel insights to improve prognostic prediction and therapeutic strategy for some cancers. Using bioinformatics and Venn analysis of gene transcriptional profiling, we identified downregulation of X-linked four-and-a-half LIM domains protein 1 (FHL1) gene in head and neck squamous cell carcinoma (HNSCC). FHL1 functions were investigated and confirmed in vitro and in vivo. FHL1 downregulated mechanisms were analyzed in HNSCCs by using methylation specific PCR, bisulfate-based sequencing, 5-Aza-dC treatment and chromatin immunoprecipitation assays. Two independent HNSCC cohorts (the training cohort n = 105 and the validation cohort n = 101) were enrolled to evaluate clinical implications of FHL1 expression by using real-time PCR or immunohistochemistry. FHL1 mRNA and protein expressions were frequently decreased in HNSCCs. FHL1 overexpression or depletion gave rise to suppress or promote cell growth through Cyclin D1, Cyclin E and p27 dysregulations. Abundant occupy of EZH2 or H3K27Me3 was observed in FHL1 promoter except for DNA hypermethylation. Reduced FHL1 mRNA expression was notably associated with poor differentiation (p = 0.020). Multivariate analysis demonstrated FHL1 mRNA expression was identified as independent prognostic predictors of overall survival (OS) (p = 0.036; HR 0.520; Cl, 0.283-0.958) and disease-free survival (DFS) (p = 0.041; HR 0.527; Cl, 0.284-0.975), which was validated by another independent cohort (p = 0.021; HR 0.404; Cl, 0.187-0.871 for OS; p = 0.011; HR 0.407; Cl, 0.203-0.815 for DFS). These results suggest epigenetic silencing of X-linked FHL1 may have an important role in adjuvant therapeutic intervention of HNSCCs and is an independent prognostic factor in patients with HNSCCs.

PRR11 Is a Prognostic Marker and Potential Oncogene in Patients with Gastric Cancer

PRR11 is a potential candidate oncogene that has been implicated in the pathogenesis of lung cancer, however the role of PRR11 in gastric cancer is currently unclear. In the present study, we investigated the role of PRR11 in gastric cancer by evaluating its expression status in samples from a cohort of 216 patients with gastric cancer. PRR11 was found to be overexpressed in 107 (49.5%) patients by immunohistochemistry of tissue microarrays generated using the patient samples. Furthermore, PRR11 overexpression was found to correlate significantly with clinicopathologic features such as tumor invasion, tumor differentiation, and disease stage. Survival analysis of the cohort revealed that PRR11 is an independent prognostic factor for gastric cancer patients. PRR11 was stably silenced in a gastric carcinoma cell line using an shRNA-based approach, and treated cells showed decreased cellular proliferation and colony formation in vitro and cell growth in vivo, companied by decreased expression of CTHRC1 and increased expression of LXN, proteins involved in tumor progression. Evaluation of human gastric cancer samples demonstrated that PRR11 expression was also associated with increased CTHRC1 and decreased LXN expression. These data indicate that PRR11 may be widely activated in human gastric cancer and are consistent with the hypothesis that PRR11 functions as an oncogene in the development and progression of gastric cancer.

FHL1 inhibits the growth of tongue squamous cell carcinoma cells via G1/S cell cycle arrest

Four and a half LIM protein 1 (FHL1) has been characterized as a tumor suppressor in various types of tumor. However, the biological function and underlying mechanism of FHL1 in tongue squamous cell carcinoma (TSCC) remain to be elucidated. The present study demonstrated that FHL1 inhibits anchorage‑dependent and ‑independent growth of TSCC cells in vitro and tumor growth in nude mice, as determined by cell proliferation and soft agar assays. Knockdown of FHL1 with FHL1 small interfering RNA (siRNA) promoted tumor growth in nude mice. Mechanistically, flow cytometric analysis showed that knockdown of FHL1 promoted G1/S cell cycle progression. Furthermore, expression of cell cycle‑associated regulators, cyclin D and cyclin E, were detected by western blotting and reverse transcription‑quantitative polymerase chain reaction. Cyclin D and cyclin E were markedly elevated at both the protein and mRNA level in the FHL1 siRNA‑transfected cells. These results suggested that FHL1 has a tumor suppressive role in TSCC and that FHL1 may be a useful target for TSCC gene therapy.

MiR-410 is overexpressed in liver and colorectal tumors and enhances tumor cell growth by silencing FHL1 via a direct/indirect mechanism

FHL1 is an important tumor-suppressor that is downregulated in multiple tumors by unknown mechanisms. We demonstrated that miR-410 specifically targets the 3′UTR of FHL1. Furthermore, using DNA bisulfite modification and sequencing experiments, we demonstrated that the FHL1 promoter is hypermethylated in cancer cells. FHL1 methylation is increased upon miR-410 expression, suggesting that the regulation of FHL1 by miR-410 occurs by a dual mechanism. Using chromatin immunoprecipitation assays, we observed that miR-410 overexpression results in the increased binding of DNMT3A at the FHL1 promoter, which could explain how miR-410 regulates FHL1 methylation. Importantly, in vitro and in vivo results suggest that miR-410 may have oncogenic properties. Furthermore, both miR-410 and DNMT3A are upregulated in clinical human liver and colorectal tumors cancers. Our results suggest that miR-410 may function as an oncomiR and are consistent with its key function in regulating FHL1 in certain digestive system cancers.

The four and a half LIM family members are novel interactants of the human T-cell leukemia virus type 1 Tax oncoprotein

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia (ATL). The viral regulatory protein Tax1 plays a pivotal role in T-cell transformation and ATL development. Previous studies in our laboratory, using the yeast 2-hybrid approach to screen a T-cell library for Tax1-interacting partners, identified the cellular Four and a Half Lim domain protein 3 (FHL3) as a possible Tax1-interacting candidate. FHL3 is a member of the FHL family of proteins, which function as transcriptional coactivators and cytoskeleton regulators and have a role in cancer progression and development. The aim of this study was to investigate the physical and functional interaction between Tax1 and members of the FHL family of proteins. We show that Tax1 and FHL3 interact both in vitro and in vivo. Furthermore, both FHL1 and -2 also interact with Tax1. We have demonstrated that FHL3 enhances Tax1-mediated activation of the viral long terminal repeat (LTR) without affecting basal activity and that FHL1 to -3 regulate NF-κB activation by Tax1 in a cell-specific manner. In addition, we have found that the interaction between Tax1 and FHL1 to -3 affects the localization of these proteins, leading to their redistribution in cells. Tax1 also affected FHL3 cytoskeleton function by increasing FHL3-mediated cell spreading. Overall, our results suggest that the interaction between Tax1 and the FHL family alters both the transactivating activity and the subcellular localization of Tax1 and provide new insights into molecular mechanisms that underlie the oncogenic nature of this HTLV-1 protein.

SRC points the way to biomarkers and chemotherapeutic targets

The role of Src in tumorigenesis has been extensively studied since the work of Peyton Rous over a hundred years ago. Src is a non-receptor tyrosine kinase that plays key roles in signaling pathways controlling tumor cell growth and migration. Src regulates the activities of numerous molecules to induce cell transformation. However, transformed cells do not always migrate and realize their tumorigenic potential. They can be normalized by surrounding nontransformed cells by a process called contact normalization. Tumor cells need to override contact normalization to become malignant or metastatic. In this review, we discuss the role of Src in cell migration and contact normalization, with emphasis on Cas and Abl pathways. This paradigm illuminates several chemotherapeutic targets and may lead to the identification of new biomarkers and the development of effective anticancer treatments.

FHL family members suppress vascular endothelial growth factor expression through blockade of dimerization of HIF1α and HIF1β

Four and a half LIM domain (FHL) proteins belong to a family of LIM-only proteins that have been implicated in the development and progression of various types of cancers. However, the role of FHL proteins in tumor angiogenesis remains to be elucidated. Herein, we demonstrate that FHL1-3 decrease the promoter activity and expression of vascular endothelial growth factor (VEGF), the key regulator of angiogenesis in cancer growth and progression as well as an important target gene of the transcription factor hypoxia-inducible factor 1 (HIF1α/HIF1β). FHL1-3 interacted with HIF1α both in vitro and in vivo. A single LIM domain of FHL1 was sufficient for its interaction with HIF1α. FHL1 interacted with the HIF1α region containing basic helix-loop-helix (bHLH) motif and PER-ARNT-SIM domain, both of which aid in dimerization with HIF1β and DNA binding. FHL1-3 inhibited HIF1 transcriptional activity and HIF1-mediated VEGF expression in a hypoxia-independent manner. Moreover, FHL1 blocked HIF1α-HIF1β heterodimerization and HIF1α recruitment to the VEGF promoter. These data suggest that FHL proteins are involved in negative regulation of VEGF possibly by interfering with the dimerization and DNA binding of HIF1 subunits and may play an important role in tumor angiogenesis.

High prevalence of epigenetic inactivation of the human four and a half LIM domains 1 gene in human oral cancer

The four and a half LIM domains 1 (FHL1) gene has been related to carcinogenesis. However, the expression status of FHL1 in human oral squamous cell carcinoma (OSCC) remains unclear and the detailed mechanism of gene silencing is poorly understood. The aim of this study was to examine the FHL1 expression level and its regulatory mechanism in OSCCs. Quantitative reverse-transcriptase-polymerase chain reaction (PCR) and western blotting showed significant downregulation of FHL1 in all OSCC-derived cell lines (Sa3, HSC-2, HSC-3, HSC-4, HO-1-u-1, HO-1-N-1, KON and Ca9-22) compared to human normal oral keratinocytes. We also found that FHL1 mRNA expression was frequently downregulated (P<0.01) in 51 (86.4%) of 59 primary OSCCs compared with the corresponding normal oral tissues, while there was no significant difference between the status of the FHL1 protein expression in OSCCs and the clinicopathological features. Using methylation-specific PCR, we detected methylated FHL1 in all cell lines and treatment with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine restored the FHL1 expression. However, no significant restoration of FHL1 expression was observed using sodium butyrate, an inhibitor of histone deacetylase and chromatin immunoprecipitation showed that histone H3 lysine 9 in the FHL1 promoter region was significantly acetylated. In addition, no mutation in the entire coding region of the FHL1 gene was found. Therefore, our data suggested that inactivation of the FHL1 gene is a frequent event during oral carcinogenesis and that the mechanism of FHL1 downregulation in OSCCs is through DNA methylation of the promoter region rather than histone deacetylation or mutation.

Downregulation and antiproliferative role of FHL3 in breast cancer

Four and a half LIM domain (FHL) protein 3 is a member of the FHL protein family that plays roles in the regulation of signal transduction, cell adhesion, survival, and mobility. FHL3 has been implicated in the development and progression of liver cancer. However, the biological function of FHL3 in other cancers remains unclear. Here, we show that FHL3 is downregulated in breast cancer patients. Using small interfering RNA (siRNA) knockdown and/or overexpression experiments, we demonstrated that FHL3 suppressed anchorage-dependent and -independent growth of human breast cancer cells. The antiproliferative effects of FHL3 on breast cancer cell growth were associated with both the G1 and the G2/M cell cycle arrest, which was accompanied by a marked inhibition of the G1-phase marker cyclin D1 and the G2/M-phase marker cyclin B1 as well as the induction of the cyclin dependent kinase inhibitor p21 (WAF1/CIP1), a negative regulator of cell cycle progression at G1 and G2. These results suggest that FHL3 may play a role in the development and progression of breast cancer, and thereby may be a potential target for human breast cancer gene therapy.

FHL1 on chromosome X is a single-hit gastrointestinal tumor-suppressor gene and contributes to the formation of an epigenetic field defect

Tumor-suppressor genes on chromosome X can be inactivated by a single hit, any of the point mutations, chromosomal loss and aberrant DNA methylation. As aberrant DNA methylation can be induced frequently, we here aimed to identify a tumor-suppressor gene on chromosome X inactivated by promoter DNA methylation. Of 69 genes on chromosome X upregulated by treatment of a gastric cancer cell line with a DNA-demethylating agent, 5-aza-2'-deoxycytidine, 11 genes had low or no expression in the cell line and abundant expression in normal gastric mucosae. Among them, FHL1 was frequently methylation-silenced in gastric and colon cancer cell lines, and methylated in primary gastric (21/80) and colon (5/50) cancers. Knockdown of the endogenous FHL1 in two cell lines by two kinds of shRNAs significantly increased cell growth in vitro and sizes of xenografts in nude mice. Expression of exogenous FHL1 in a non-expressing cell line significantly reduced its migration, invasion and growth. Notably, a somatic mutation (G642T; Lys214Asn) was identified in one of 144 colon cancer specimens, and the mutant FHL1 was shown to lack its inhibitory effects on migration, invasion and growth. FHL1 methylation was associated with Helicobacter pylori infection and accumulated in normal-appearing gastric mucosae of gastric cancer patients. These data showed that FHL1 is a methylation-silenced tumor-suppressor gene on chromosome X in gastrointestinal cancers, and that its silencing contributes to the formation of an epigenetic field for cancerization.

Fhl1 as a downstream target of Wnt signaling to promote myogenesis of C2C12 cells

Previous studies have shown that Wnt signaling is involved in postnatal mammalian myogenesis; however, the downstream mechanism of Wnt signaling is not fully understood. This study reports that the murine four-and-a-half LIM domain 1 (Fhl1) could be stimulated by β-catenin or LiCl treatment to induce myogenesis. In contrast, knockdown of the Fhl1 gene expression in C2C12 cells led to reduced myotube formation. We also adopted reporter assays to demonstrate that either β-catenin or LiCl significantly activated the Fhl1 promoter, which contains four putative consensus TCF/LEF binding sites. Mutations of two of these sites caused a significant decrease in promoter activity by luciferase reporter assay. Thus, we suggest that Wnt signaling induces muscle cell differentiation, at least partly, through Fhl1 activation.

Down-regulated SPARCL1 is associated with clinical significance in human gastric cancer

BACKGROUND

SPARC-like protein 1 (SPARCL1), a member of extracelluar matrix glycoprotein, is involved in many physiological functions.

METHODS

Tissue microarray (TMA) blocks were constructed based on 1,072 Chinese patients, containing both gastric cancer (GC) tissues and adjacent normal mucosa tissues. We analyzed the expression of SPARCL1 from both mRNA and protein level, using Real-time quantitative polymerase chain reaction (qRT-PCR), semi-quantitative PCR, immunohistochemistry (IHC), and Western blotting. Loss of heterozygosity analysis at the SPARCL1 gene locus was carried out using ten paired tumor and matched normal tissues.

RESULTS

SPARCL1 mRNA was significantly reduced in tumor specimens compared with normal tissues. Down-regulation of SPARCL1 protein was detected in 413 cases (38.7%) of 1,072 primary gastric tumor tissues. Kaplan-Meier survival curves demonstrated that SPARCL1-positive patients had better median survival time than SPARCL1-negative patients (59 months vs. 28 months, P = 0.001). Multivariate survival analysis revealed that SPARCL1 was an independent prognostic factor in gastric adenocarcinoma patients with no metastasis and well/moderately differentiated. The incidence of LOH for each individual marker was 12.5% (1/8) for D4S2462, 20% (2/10) for D4S2929, and 33.3% (3/9) for SPARCL1.

CONCLUSIONS

Our study revealed the clinical significance of SPARCL1 expression, providing a basis that the loss of SPARCL1 is a negative event in GC progression and prognosis. Furthermore, SPARCL1 protein might be considered to be a potential differentiation marker.

Downregulation and growth inhibitory role of FHL1 in lung cancer

Four and a half Lin-11, Isl-1, Mac-3 (LIM) protein 1 (FHL1) has been linked to carcinogenesis. However, the role of FHL1 in lung cancer remains unclear and the detailed mechanism underlying its tumor suppressive role is poorly understood. The purpose of this study was to examine FHL1 expression in lung cancer patients and to investigate how it was associated with lung cancer cell growth. Immunoblotting and immunohistochemistry showed that FHL1 protein was downregulated in over 90% of 80 lung cancer patients. FHL1 expression was strongly correlated with tumor histological types (p < 10(-4) ) and the differentiation of the tumor (p = 0.002). FHL1 inhibited anchorage-dependent and -independent growth of human lung cancer cell lines. The inhibitory effects of FHL1 on lung cancer cell growth were associated with both the G1 and the G2/M cell cycle arrest concomitant with a marked inhibition of cyclin A, cyclin B1 and cyclin D as well as the induction of the cyclin dependent kinase inhibitors p21 (WAF1/CIP1) and p27 (Kip1). Direct intratumoral injection of an adenovirus expressing FHL1 dramatically suppressed the growth of A549 lung cancer cells in nude mice. Our data suggest that reduced expression of FHL1 may play an important role in the development and progression of lung cancer and that FHL1 may be a useful target for lung cancer gene therapy.

Genes, proteins and complexes: the multifaceted nature of FHL family proteins in diverse tissues

Four and a half LIM domain protein 1 (FHL1) is the founding member of the FHL family of proteins characterized by the presence of four and a half highly conserved LIM domains. The LIM domain is a protein-interaction motif and is involved in linking proteins with both the actin cytoskeleton and transcriptional machinery. To date, more than 25 different protein interactions have been identified for full length FHL1 and its spliced variants, and these interactions can be mapped to a variety of functional classes. Because FHL1 is expressed predominantly in skeletal muscle, all of these proteins interactions translate into a multifunctional and integral role for FHL1 in muscle development, structural maintenance, and signalling. Importantly, 27 FHL1 genetic mutations have been identified that result in at least six different X-linked myopathies, with patients often presenting with cardiovascular disease. FHL1 expression is also significantly up-regulated in a variety of cardiac disorders, even at the earliest stages of disease onset. Alternatively, FHL1 expression is suppressed in a variety of cancers, and ectopic FHL1 expression offers potential for some phenotype rescue. This review focuses on recent studies of FHL1 in muscular dystrophies and cardiovascular disease, and provides a comprehensive review of FHL1s multifunctional roles in skeletal muscle.

Identification of an FHL1 protein complex containing ACTN1, ACTN4, and PDLIM1 using affinity purifications and MS-based protein-protein interaction analysis

INTRODUCTION

Four and a half LIM domains protein 1 (FHL1) is the most widely expressed member of the FHL family of proteins, consisting of four and a half highly conserved LIM domains. A multifunctional and integral role for FHL1 has been implicated in muscle development, structural maintenance, and signaling. To date, 27 FHL1 mutations have been identified that result in at least six different X-linked myopathies, with patients often presenting with cardiovascular complications. Since proteins assemble into dynamic complexes within the cell, FHL1 likely mediates its biological functions in conjunction with other proteins. Delineation of FHL1 interactions could provide insight into its regulatory functions.

METHODS

We performed tandem affinity purification from human embryonic kidney 293 (HEK-293) cells to purify FHL1 and interacting proteins. To identify the potential interactors of FHL1 we performed a total of 9 different purifications from HEK-293 cells which included 3 experimental replicates for each biological condition: FHL1, tag control (DPYSL3), and negative control (empty vector). Purified samples were analyzed by liquid chromatography mass spectrometry (LC-MS). Potential interactors were then verified by immunoprecipitation from mouse heart ventricles and interactions visualized in adult cardiomyocytes using 3D fluorescence microscopy.

RESULTS

We identified a total of 310 different proteins from all 9 purifications and by applying stringent filtering criteria we eliminated all proteins found in any of the controls and only allowed those that were detected in two or more bait purification. We identified 34 high confidence potential binding partners of FHL1. We then showed that FHL1 exists as part of a complex that binds with PDLIM1, GSN and ACTN1.

Development of a novel splice array platform and its application in the identification of alternative splice variants in lung cancer

Background

Microarrays strategies, which allow for the characterization of thousands of alternative splice forms in a single test, can be applied to identify differential alternative splicing events. In this study, a novel splice array approach was developed, including the design of a high-density oligonucleotide array, a labeling procedure, and an algorithm to identify splice events.

Results

The array consisted of exon probes and thermodynamically balanced junction probes. Suboptimal probes were tagged and considered in the final analysis. An unbiased labeling protocol was developed using random primers. The algorithm used to distinguish changes in expression from changes in splicing was calibrated using internal non-spliced control sequences. The performance of this splice array was validated with artificial constructs for CDC6, VEGF, and PCBP4 isoforms. The platform was then applied to the analysis of differential splice forms in lung cancer samples compared to matched normal lung tissue. Overexpression of splice isoforms was identified for genes encoding CEACAM1, FHL-1, MLPH, and SUSD2. None of these splicing isoforms had been previously associated with lung cancer.

Conclusions

This methodology enables the detection of alternative splicing events in complex biological samples, providing a powerful tool to identify novel diagnostic and prognostic biomarkers for cancer and other pathologies.

Four and a half LIM domains 1 (FHL1) and receptor interacting protein of 140kDa (RIP140) interact and cooperate in estrogen signaling

Four and a half LIM domains 1 (FHL1) belongs to a family of LIM-only proteins that regulate gene transcription, cell proliferation, differentiation and apoptosis. However, the biological function of FHL1 remains largely unknown. We used a yeast two-hybrid system and identified receptor interacting protein of 140kDa (RIP140) as a novel FHL1-binding protein. RIP140 interacted with FHL1 both in vitro and in mammalian cells and estrogen enhanced this interaction. All domains of FHL1 are required to interact with RIP140. Overexpression of FHL1 enhanced RIP140 repression of estrogen signaling in breast cancer cells in a reporter assay, whereas reduction of endogenous FHL1 with FHL1 small interfering RNA abolished this effect. Furthermore, overexpression of the FHL1 deletion mutant that lacks the RIP140-binding sites had no effect on RIP140 repression of estrogen signaling. Consistent with the results of the reporter assays, FHL1 and RIP140 synergistically inhibited the transcription of the estrogen-responsive gene pS2. The results presented here suggested the cooperative transcriptional regulation of estrogen signaling by FHL1 and RIP140, and might provide a new regulation mechanism by which estrogen signaling-related diseases such as breast cancer develop.