Nucleolar follistatin promotes cancer cell survival under glucose-deprived conditions through inhibiting cellular rRNA synthesis

The Reign of Follistatin in Tumors and Their Microenvironment: Implications for Drug Resistance

Follistatin (FST) is a potent neutralizer of the transforming growth factor-β superfamily and is associated with normal cellular programs and various hallmarks of cancer, such as proliferation, migration, angiogenesis, and immune evasion. The aberrant expression of FST by solid tumors is a well-documented observation, yet how FST influences tumor progression and therapy response remains unclear. The recent surge in omics data has revealed new insights into the molecular foundation underpinning tumor heterogeneity and its microenvironment, offering novel precision medicine-based opportunities to combat cancer. In this review, we discuss these recent FST-centric studies, thereby offering an updated perspective on the protean role of FST isoforms in shaping the complex cellular ecosystem of tumors and in mediating drug resistance.

An integrated genomic approach identifies follistatin as a target of the p63-epidermal growth factor receptor oncogenic network in head and neck squamous cell carcinoma

Although numerous putative oncogenes have been associated with the etiology of head and neck squamous cell carcinoma (HNSCC), the mechanisms by which these oncogenes and their downstream targets mediate tumor progression have not been fully elucidated. We performed an integrative analysis to identify a crucial set of targets of the oncogenic transcription factor p63 that are common across multiple transcriptomic datasets obtained from HNSCC patients, and representative cell line models. Notably, our analysis revealed FST which encodes follistatin, a secreted glycoprotein that inhibits the transforming growth factor TGFβ/activin signaling pathways, to be a direct transcriptional target of p63. In addition, we found that FST expression is also driven by epidermal growth factor receptor EGFR signaling, thus mediating a functional link between the TGF-β and EGFR pathways. We show through loss- and gain-of-function studies that FST predominantly imparts a tumor-growth and migratory phenotype in HNSCC cells. Furthermore, analysis of single-cell RNA sequencing data from HNSCC patients unveiled cancer cells as the dominant source of FST within the tumor microenvironment and exposed a correlation between the expression of FST and its regulators with immune infiltrates. We propose FST as a prognostic biomarker for patient survival and a compelling candidate mediating the broad effects of p63 on the tumor and its associated microenvironment.

Quiescent Ovarian Cancer Cells Secrete Follistatin to Induce Chemotherapy Resistance in Surrounding Cells in Response to Chemotherapy

PURPOSE

We recently reported that the transcription factor NFATC4, in response to chemotherapy, drives cellular quiescence to increase ovarian cancer chemoresistance. The goal of this work was to better understand the mechanisms of NFATC4-driven ovarian cancer chemoresistance.

EXPERIMENTAL DESIGN

We used RNA sequencing to identify NFATC4-mediated differential gene expression. CRISPR-Cas9 and FST (follistatin)-neutralizing antibodies were used to assess impact of loss of FST function on cell proliferation and chemoresistance. ELISA was used to quantify FST induction in patient samples and in vitro in response to chemotherapy.

RESULTS

We found that NFATC4 upregulates FST mRNA and protein expression predominantly in quiescent cells and FST is further upregulated following chemotherapy treatment. FST acts in at least a paracrine manner to induce a p-ATF2-dependent quiescent phenotype and chemoresistance in non-quiescent cells. Consistent with this, CRISPR knockout (KO) of FST in ovarian cancer cells or antibody-mediated neutralization of FST sensitizes ovarian cancer cells to chemotherapy treatment. Similarly, CRISPR KO of FST in tumors increased chemotherapy-mediated tumor eradication in an otherwise chemotherapy-resistant tumor model. Suggesting a role for FST in chemoresistance in patients, FST protein in the abdominal fluid of patients with ovarian cancer significantly increases within 24 hours of chemotherapy exposure. FST levels decline to baseline levels in patients no longer receiving chemotherapy with no evidence of disease. Furthermore, elevated FST expression in patient tumors is correlated with poor progression-free, post-progression-free, and overall survival.

CONCLUSIONS

FST is a novel therapeutic target to improve ovarian cancer response to chemotherapy and potentially reduce recurrence rates.

Tubule-Derived Follistatin Is Increased in the Urine of Rats with Renal Ischemia and Reflects the Severity of Acute Tubular Damage

Activin A, a member of the TGF-beta superfamily, is a negative regulator of tubular regeneration after renal ischemia. Activin action is controlled by an endogenous antagonist, follistatin. However, the role of follistatin in the kidney is not fully understood. In the present study, we examined the expression and localization of follistatin in normal and ischemic rat kidneys and measured urinary follistatin in rats with renal ischemia to assess whether urinary follistatin could serve as a biomarker for acute kidney injury. Using vascular clamps, renal ischemia was induced for 45 min in 8-week-old male Wistar rats. In normal kidneys, follistatin was localized in distal tubules of the cortex. In contrast, in ischemic kidneys, follistatin was localized in distal tubules of both the cortex and outer medulla. Follistatin mRNA was mainly present in the descending limb of Henle of the outer medulla in normal kidneys but was upregulated in the descending limb of Henle of both the outer and inner medulla after renal ischemia. Urinary follistatin, which was undetectable in normal rats, was significantly increased in ischemic rats and peaked 24 h after reperfusion. There was no correlation between urinary follistatin and serum follistatin. Urinary follistatin levels were increased according to ischemic duration and were significantly correlated with the follistatin-positive area as well as the acute tubular damage area. These results suggest that follistatin normally produced by renal tubules increases and becomes detectable in urine after renal ischemia. Urinary follistatin might be useful to assess the severity of acute tubular damage.

Characterization and Function of the Interaction of Angiogenin With Alpha-Actinin 2

Angiogenin (ANG) is the first human tumor-derived angiogenic protein, which can promote angiogenesis and tumor growth. In a previous study, we identified alpha-actinin 2 (ACTN2), a cytoskeletal protein, as a direct interacting protein with angiogenin. However, the interaction between ANG and ACTN2 was not characterized in detail, which may provide information on the molecular mechanisms of ANG functions. In this study, we mapped the accurate binding domain and sites in ANG and ACTN2, respectively. In ANG, the residues from 83 to 105 are the smallest motif that can bind to ACTN2. We then use site mutation analysis to identify the precise binding sites of ANG in the interaction and found that the 101st residue arginine (R101) represents the critical residue involved in the ANG–ACTN2 interaction. In ACTN2, the residues from 383 to 632, containing two spectrin domains in the middle of the rod structure of ACTN2, play an important role in the interaction. Furthermore, we validated the interaction of ACTN2-383–632 to ANG by glutathione-S-transferase (GST) pull-down assay. In functional analysis, overexpressed ACTN2-383–632 could impair tumor cell motility observably, including cell migration and invasion. Meanwhile, ACTN2-383–632 overexpression inhibited tumor cell proliferation and survival as well. These data suggest that an excess expression of ACTN2 segment ACTN2-383–632 can inhibit tumor cell motility and proliferation by interfering with the interaction between ANG and ACTN2, which provides a potential mechanism of ANG action in tumor growth and metastasis.

Upregulation of follistatin and low apoptotic activity in intraductal oncocytic papillary neoplasm of the pancreatobiliary system

Intraductal oncocytic papillary neoplasm (IOPN) is a rare intraductal tumor of the pancreatobiliary system. Currently, little is known about its distinct characteristics, unlike intraductal papillary mucinous neoplasms (IPMN) and intraductal papillary neoplasms of the bile duct (IPNB). The present study compared 22 IOPNs (18 pancreatic and 4 biliary) with those of 61 IPMNs/8 IPNBs. IOPNs were classified into pure and combined types, depending on the coexistence of IPMN/IPNB. Multiple gene expression analysis (nCounter system) was performed, and hierarchical clustering analysis separated IOPNs(n = 4) and IPMNs(n = 3)/ IPNBs(n = 3), and pathway score analysis supported the result. Volcano plot identified follistatin (FST) as the most upregulated mRNA in IOPN in comparison to the gastric subtype (log2 fold change of 5.34) and the intestinal subtype (that of 5.81) of IPMN/IPNB. The expression of FST in IOPN was also high in quantitative polymerase chain reaction and immunohistochemical analysis. We also found lower apoptotic activity in IOPN, particularly in pure type, compared to high-grade or invasive IPMN/IPNB using immunohistochemistry for cleaved caspase 3. But, combined type IOPN was more similar to IPMN/IPNB than pure IOPN. In conclusion, we proved that IOPN, particularly pure IOPN, is distinct from IPMN/IPNB in FST mRNA overexpression and exhibits lower apoptotic activity.

Human papillomavirus E7 binds Oct4 and regulates its activity in HPV-associated cervical cancers

Octamer binding transcription factor-4 (Oct4), is highly expressed in stem cells and has indispensable roles in pluripotency and cellular reprogramming. In contrast to other factors used for cellular reprogramming, a role for Oct4 outside embryonic stem cells has been elusive and highly controversial. Emerging evidence implicates Oct4 in the carcinogenic process, but the mechanism through which Oct4 may be functioning in cancers is not fully appreciated. Here, we provide evidence that Oct4 is expressed in human cervical cancer and this expression correlates with the presence of the human papillomavirus (HPV) oncogenes E6 and E7. Surprisingly, the viral oncogenes can complement exogenously provided Oct4 in reprogramming assays, providing functional validation for their ability to activate Oct4 transcription in Mouse Embryonic Fibroblasts (MEFs). To interrogate potential roles of Oct4 in cervical cancers we knocked-down Oct4 in HPV(+) (HeLa & CaSki) and HPV(-) (C33A) cervical cancer cell lines and found that Oct4 knockdown attenuated clonogenesis, only in the HPV(+) cells. More unexpectedly, cell proliferation and migration, were differentially affected in HPV(+) and HPV(-) cell lines. We provide evidence that Oct4 interacts with HPV E7 specifically at the CR3 region of the E7 protein and that introduction of the HPV oncogenes in C33A cells and human immortalised keratinocytes generates Oct4-associated transcriptional and phenotypic patterns, which mimic those seen in HPV(+) cells. We propose that a physical interaction of Oct4 with E7 regulates its activity in HPV(+) cervical cancers in a manner not seen in other cancer types.

Follistatin is a novel therapeutic target and biomarker in FLT3/ITD acute myeloid leukemia

Internal tandem duplication of Fms-like tyrosine kinase 3 (FLT3/ITD) occurs in about 30% of acute myeloid leukemia (AML) and is associated with poor response to conventional treatment and adverse outcome. Here, we reported that human FLT3/ITD expression led to axis duplication and dorsalization in about 50% of zebrafish embryos. The morphologic phenotype was accompanied by ectopic expression of a morphogen follistatin (fst) during early embryonic development. Increase in fst expression also occurred in adult FLT3/ITD-transgenic zebrafish, Flt3/ITD knock-in mice, and human FLT3/ITD AML cells. Overexpression of human FST317 and FST344 isoforms enhanced clonogenicity and leukemia engraftment in xenotransplantation model via RET, IL2RA, and CCL5 upregulation. Specific targeting of FST by shRNA, CRISPR/Cas9, or antisense oligo inhibited leukemic growth in vitro and in vivo. Importantly, serum FST positively correlated with leukemia engraftment in FLT3/ITD AML patient-derived xenograft mice and leukemia blast percentage in primary AML patients. In FLT3/ITD AML patients treated with FLT3 inhibitor quizartinib, serum FST levels correlated with clinical response. These observations supported FST as a novel therapeutic target and biomarker in FLT3/ITD AML.

Follistatin impacts Tumor Angiogenesis and Outcome in Thymic Epithelial Tumors

Tumor angiogenesis is a key factor in the progression of thymic epithelial tumors (TETs). Activin A, a member of the TGFβ family, and its antagonist Follistatin are involved in several human malignancies and angiogenesis. We investigated Activin A and Follistatin in serum and tumor tissue of patients with TETs in relation to microvessel density (MVD), WHO histology classification, tumor stage and outcome. Membranous Activin A expression was detected in all tumor tissues of TETs, while Follistatin staining was found in tumor nuclei and cytoplasm. Patients with TETs presented with significantly higher Activin A and Follistatin serum concentrations compared to healthy volunteers, respectively. Follistatin serum concentrations correlated significantly with tumor stage and decreased to physiologic values after complete tumor resection. Follistatin serum concentrations correlated further with MVD and were associated with significantly worse freedom from recurrence (FFR). Low numbers of immature tumor vessels represented even an independent worse prognostic factor for FFR at multivariable analysis. To conclude, the Activin A - Follistatin axis is involved in the pathogenesis of TETs. Further study of Follistatin and Activin A in TETs is warranted as the molecules may serve as targets to inhibit tumor angiogenesis and tumor progression.

Follistatin Protects Against Glomerular Mesangial Cell Apoptosis and Oxidative Stress to Ameliorate Chronic Kidney Disease

Aims: Interventions to inhibit oxidative stress and apoptosis, important pathogenic contributors toward the progression of chronic kidney disease (CKD), are not well established. Here, we investigated the role of a transforming growth factor beta (TGFβ) superfamily neutralizing protein, follistatin (FST), in the regulation of apoptosis and oxidative stress in glomerular mesangial cells (MCs) and in the progression of CKD. Results: The endoplasmic reticulum (ER) stress inducer thapsigargin (Tg), known to cause MC apoptosis, led to a post-translational increase in the expression of FST. Recombinant FST protected, whereas FST downregulation augmented, Tg-induced apoptosis without affecting Ca²⁺ release or ER stress induction. Although activins are the primary ligands neutralized by FST, their inhibition with neutralizing antibodies did not affect Tg-induced apoptosis. Instead, FST protected against Tg-induced apoptosis through neutralization of reactive oxygen species (ROS) independently of its ability to neutralize activins. Importantly, administration of FST to mice with CKD protected against renal cell apoptosis and oxidative stress. This was associated with improved kidney function, reduced albuminuria, and attenuation of fibrosis. Innovation and Conclusion: Independent of its activin neutralizing ability, FST protected against Tg-induced apoptosis through neutralization of ROS and consequent suppression of oxidative stress, seen both in vitro and in vivo. Importantly, FST also ameliorated fibrosis and improved kidney function in CKD. FST is, thus, a novel potential therapeutic agent for delaying the progression of CKD. Antioxid. Redox Signal. 31, 551-571.

Autophagic flux blockage in alveolar epithelial cells is essential in silica nanoparticle-induced pulmonary fibrosis

Silica nanoparticles (SiNPs) have been reported to induce pulmonary fibrosis (PF) with an unknown mechanism. Recently, the activation of autophagy, a lysosome-dependent cell degradation pathway, by SiNPs has been identified in alveolar epithelial cells (AECs). However, the underlying mechanism and the relevance of SiNPs-induced autophagy to the development of PF remain elusive. Here, we report that autophagy dysfunction and subsequent apoptosis in AECs are involved in SiNPs-induced PF. SiNPs engulfed by AECs enhance autophagosome accumulation and apoptosis both in vivo and in vitro. Mechanically, SiNPs block autophagy flux through impairing lysosomal degradation via acidification inhibition. Lysosomal reacidification by cyclic-3',5'-adenosine monophosphate (cAMP) significantly enhances autophagic degradation and attenuate apoptosis. Importantly, enhancement of autophagic degradation by rapamycin protects AECs from apoptosis and attenuates SiNPs-induced PF in the mouse model. Altogether, our data demonstrate a repressive effect of SiNPs on lysosomal acidification, contributing to the decreased autophagic degradation in AECs, thus leading to apoptosis and subsequent PF. These findings may provide an improved understanding of SiNPs-induced PF and molecular targets to antagonize it.

Landscape of long non-coding RNAs in Trichophyton mentagrophytes-induced rabbit dermatophytosis lesional skin and normal skin

Emerging evidences suggest that long non-coding RNAs (lncRNAs) play important role in disease development. However, the role of rabbit lncRNAs in the pathogenesis of dermatophytosis remains elusive. The present study aimed to study and characterize lncRNA transcriptome in 8 T. mentagrophytes-induced female rabbit dermatophytosis lesional (TM) and 4 normal saline-infected (NS) skin biopsies using RNAseq. We identified 5883 lncRNAs in 12 strand-specific RNA-seq libraries and found 64 differentially expressed lncRNAs (q < 0.05) in TM relative to NS. As in other mammalian counterparts, rabbit lncRNAs were distributed in all chromosomes except the Y chromosome and were generally smaller in size and fewer in exon numbers compared to protein coding genes. Next, co-expression analysis revealed that 107 pairs between 32 DE lncRNAs and 96 protein coding genes showed a highly correlated expression (|r| > 0.8). Moreover, miRPara analysis of the lncRNAs revealed 173 lncRNAs with precursor sequences for 9561 probable novel miRNAs. Finally, q-PCR results validated the RNA-seq results with eight randomly selected lncRNAs. To the best of our knowledge, this is the first report on rabbit lncRNAs, and our results highlighted the potential role of lncRNAs in the pathogenesis of dermatophytosis.

The emerging role of follistatin under stresses and its implications in diseases

Follistatin (FST), a single-chain glycosylated protein, is expressed in various tissues. The essential biological function of FST is binding and neutralizing transforming growth factor β (TGF-β) superfamily, including activin, myostatin, and bone morphogenetic protein (BMP). Emerging evidence indicates that FST also serves as a stress responsive protein, which plays a protective role under a variety of stresses. In most cases, FST performs the protective function through its neutralization of TGF-β superfamily. However, under certain circumstances, FST translocates into the nucleus to maintain cellular homeostasis independent of its extracellular antagonism activity. This review provides integrated insight into the most recent advances in understanding the role of FST under various stresses, and the clinical implications corresponding to these findings and discusses the mechanisms to be further studied.

Overexpression of colorectal cancer oncogene CHRDL2 predicts a poor prognosis

Bone morphogenetic proteins (BMPs) both promote and suppress tumorigenesis, and multiple BMP antagonists reportedly contribute to cancer progression. In this study, we demonstrated that the BMP antagonist Chordin-like 2 (CHRDL2) is upregulated in colorectal cancer (CRC) tissues, and that CHRDL2 levels correlate with clinical features of CRC patients, including tumor size, TNM staging, and tumor differentiation. In addition, survival rate and Cox proportional hazards model analyses showed that high CHRDL2 levels correlate with a poor prognosis in CRC. Moreover, CHRDL2 promoted CRC cell proliferation in vitro and in vivo, perhaps through up-regulation of Cyclin D1 and down-regulation of P21. Co-immunoprecipitation assays showed that CHRDL2 bound to BMPs, which inhibited p-Smad1/5, thereby promoting CRC cell proliferation and inhibiting apoptosis. These results suggest CHRDL2 could serve as a biomarker of poor prognosis in CRC, and provide evidence that CHRDL2 acts as an oncogene in human CRC, making it a novel potential therapeutic target.

Systems-level effects of ectopic galectin-7 reconstitution in cervical cancer and its microenvironment

Background

Galectin-7 (Gal-7) is negatively regulated in cervical cancer, and appears to be a link between the apoptotic response triggered by cancer and the anti-tumoral activity of the immune system. Our understanding of how cervical cancer cells and their molecular networks adapt in response to the expression of Gal-7 remains limited.

Methods

Meta-analysis of Gal-7 expression was conducted in three cervical cancer cohort studies and TCGA. In silico prediction and bisulfite sequencing were performed to inquire epigenetic alterations. To study the effect of Gal-7 on cervical cancer, we ectopically re-expressed it in the HeLa and SiHa cervical cancer cell lines, and analyzed their transcriptome and SILAC-based proteome. We also examined the tumor and microenvironment host cell transcriptomes after xenotransplantation into immunocompromised mice. Differences between samples were assessed with the Kruskall-Wallis, Dunn’s Multiple Comparison and T tests. Kaplan–Meier and log-rank tests were used to determine overall survival.

Results

Gal-7 was constantly downregulated in our meta-analysis (p < 0.0001). Tumors with combined high Gal-7 and low galectin-1 expression (p = 0.0001) presented significantly better prognoses (p = 0.005). In silico and bisulfite sequencing assays showed de novo methylation in the Gal-7 promoter and first intron. Cells re-expressing Gal-7 showed a high apoptosis ratio (p < 0.05) and their xenografts displayed strong growth retardation (p < 0.001). Multiple gene modules and transcriptional regulators were modulated in response to Gal-7 reconstitution, both in cervical cancer cells and their microenvironments (FDR < 0.05 %). Most of these genes and modules were associated with tissue morphogenesis, metabolism, transport, chemokine activity, and immune response. These functional modules could exert the same effects in vitro and in vivo, even despite different compositions between HeLa and SiHa samples.

Conclusions

Gal-7 re-expression affects the regulation of molecular networks in cervical cancer that are involved in diverse cancer hallmarks, such as metabolism, growth control, invasion and evasion of apoptosis. The effect of Gal-7 extends to the microenvironment, where networks involved in its configuration and in immune surveillance are particularly affected.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2700-8) contains supplementary material, which is available to authorized users.

Three decades of research on angiogenin: a review and perspective

As a member of the vertebrate-specific secreted ribonucleases, angiogenin (ANG) was first isolated and identified solely by its ability to induce new blood vessel formation, and now, it has been recognized to play important roles in various physiological and pathological processes through regulating cell proliferation, survival, migration, invasion, and/or differentiation. ANG exhibits very weak ribonucleolytic activity that is critical for its biological functions, and exerts its functions through activating different signaling transduction pathways in different target cells. A series of recent studies have indicated that ANG contributes to cellular nucleic acid metabolism. Here, we comprehensively review the results of studies regarding the structure, mechanism, and function of ANG over the past three decades. Moreover, current problems and future research directions of ANG are discussed. The understanding of the function and mechanism of ANG in a wide context will help to better delineate its roles in diseases, especially in cancer and neurodegenerative diseases.

Transcriptional activation of follistatin by Nrf2 protects pulmonary epithelial cells against silica nanoparticle-induced oxidative stress

Silica nanoparticles (SiO2 NPs) cause oxidative stress in respiratory system. Meanwhile, human cells launch adaptive responses to overcome SiO2 NP toxicity. However, besides a few examples, the regulation of SiO2 NP-responsive proteins and their functions in SiO2 NP response remain largely unknown. In this study, we demonstrated that SiO2 NP induced the expression of follistatin (FST), a stress responsive gene, in mouse lung tissue as well as in human lung epithelial cells (A549). The levels of Ac-H3(K9/18) and H3K4me2, two active gene markers, at FST promoter region were significantly increased during SiO2 NP treatment. The induction of FST transcription was mediated by the nuclear factor erythroid 2-related factor 2 (Nrf2), as evidenced by the decreased FST expression in Nrf2-deficient cells and the direct binding of Nrf2 to FST promoter region. Down-regulation of FST promoted SiO2 NP-induced apoptosis both in cultured cells and in mouse lung tissue. Furthermore, knockdown of FST increased while overexpression of FST decreased the expression level of NADPH oxidase 1 (NOX1) and NOX5 as well as the production of cellular reactive oxygen species (ROS). Taken together, these findings demonstrated a protective role of FST in SiO2 NP-induced oxidative stress and shed light on the interaction between SiO2 NPs and biological systems.

Follistatin288 Regulates Germ Cell Cyst Breakdown and Primordial Follicle Assembly in the Mouse Ovary

In mammals, the primordial follicle pool represents the entire reproductive potential of a female. The transforming growth factor-β (TGF-β) family member activin (ACT) contributes to folliculogenesis, although the exact mechanism is not known. The role of FST288, the strongest ACT-neutralizing isoform of follistatin (FST), during cyst breakdown and primordial follicle formation in the fetal mice ovary was assessed using an in vitro culture system. FST was continuously expressed in the oocytes as well as the cuboidal granulosa cells of growing follicles in perinatal mouse ovaries. Treatment with FST288 delayed germ cell nest breakdown, particularly near the periphery of the ovary, and dramatically decreased the percentage of primordial follicles. In addition, there was a dramatic decrease in proliferation of granulosa cells and somatic cell expression of Notch signaling was impaired. In conclusion, FST288 impacts germ cell nest breakdown and primordial follicle assembly by inhibiting somatic cell proliferation.

Physical activity and its mechanistic effects on prostate cancer

Beneficial effects of physical activity have been illustrated in numerous aspects of health. With the increasing incidence of prostate cancer and changes in physical activity of men, understanding the link between the two has important implications for changing this cancer burden. Both positive and negative associations between physical activity and prostate cancer have been previously demonstrated in observational epidemiological studies. Elucidating the biological mechanisms would lead to a better understanding of how physical activity influences the progression of prostate cancer. This review was undertaken to: (1) identify evidence in literature that demonstrates the effects of physical activity on skeletal muscle secretomes, (2) indicate the plausible signaling pathways these proteins might activate, and (3) identify evidence in literature that demonstrates the roles of the signaling pathways in prostate cancer progression and regression. We also discuss proposed biological mechanisms and signaling pathways by which physical activity may prevent the development and progression of prostate cancer. We discuss proteins involved in the normal and aberrant growth and development of the prostate gland that may be affected by physical activity. We further identify future directions for research, including a better understanding of the biological mechanisms, the need to standardize physical activity and identify mechanistic end points of physical activity that can then be correlated with outcomes.

Binding of carbonic anhydrase IX to 45S rDNA genes is prevented by exportin-1 in hypoxic cells

Carbonic anhydrase IX (CA IX) is a surrogate marker of hypoxia, involved in survival and pH regulation in hypoxic cells. We have recently characterized its interactome, describing a set of proteins interacting with CA IX, mainly in hypoxic cells, including several members of the nucleocytoplasmic shuttling apparatuses. Accordingly, we described complex subcellular localization for this enzyme in human cells, as well as the redistribution of a carbonic anhydrase IX pool to nucleoli during hypoxia. Starting from this evidence, we analyzed the possible contribution of carbonic anhydrase IX to transcription of the 45 S rDNA genes, a process occurring in nucleoli. We highlighted the binding of carbonic anhydrase IX to nucleolar chromatin, which is regulated by oxygen levels. In fact, CA IX was found on 45 S rDNA gene promoters in normoxic cells and less represented on these sites, in hypoxic cells and in cells subjected to acetazolamide-induced acidosis. Both conditions were associated with increased representation of carbonic anhydrase IX/exportin-1 complexes in nucleoli. 45 S rRNA transcript levels were accordingly downrepresented. Inhibition of nuclear export by leptomycin B suggests a model in which exportin-1 acts as a decoy, in hypoxic cells, preventing carbonic anhydrase IX association with 45 S rDNA gene promoters.

Follistatin is a novel biomarker for lung adenocarcinoma in humans

Background

Follistatin (FST), a single chain glycoprotein, is originally isolated from follicular fluid of ovary. Previous studies have revealed that serum FST served as a biomarker for pregnancy and ovarian mucinous tumor. However, whether FST can serve as a biomarker for diagnosis in lung adenocarcinoma of humans remains unclear.

Methods and Results

The study population consisted of 80 patients with lung adenocarcinoma, 40 patients with ovarian adenocarcinoma and 80 healthy subjects. Serum FST levels in patients and healthy subjects were measured using ELISA. The results showed that the positive ratio of serum FST levels was 51.3% (41/80), which was comparable to the sensitivity of FST in 40 patients with ovarian adenocarcinoma (60%, 24/40) using the 95th confidence interval for the healthy subject group as the cut-off value. FST expressions in lung adenocarcinoma were examined by immunohistochemical staining, we found that lung adenocarcinoma could produce FST and there was positive correlation between the level of FST expression and the differential degree of lung adenocarcinoma. Furthermore, the results showed that primary cultured lung adenocarcinoma cells could secrete FST, while cells derived from non-tumor lung tissues almost did not produce FST. In addition, the results of CCK8 assay and flow cytometry showed that using anti-FST monoclonal antibody to neutralize endogenous FST significantly augmented activin A-induced lung adenocarcinoma cells apoptosis.

Conclusions

These data indicate that lung adenocarcinoma cells can secret FST into serum, which may be beneficial to the survival of adenocarcinoma cells by neutralizing activin A action. Thus, FST can serve as a promising biomarker for diagnosis of lung adenocarcinoma and a useful biotherapy target for lung adenocarcinoma.

Reduction of AUF1-mediated follistatin mRNA decay during glucose starvation protects cells from apoptosis

Follistatin (FST) performs several vital functions in the cells, including protection from apoptosis during stress. The expression of FST is up-regulated in response to glucose deprivation by an unknown mechanism. We herein showed that the induction of FST by glucose deprivation was due to an increase in the half-life of its mRNA. We further identified an AU-rich element (ARE) in the 3′UTR of FST mRNA that mediated its decay. The expression of FST was elevated after knocking down AUF1 and reduced when AUF1 was further expressed. In vitro binding assays and RNA pull-down assays revealed that AUF1 interacted with FST mRNA directly via its ARE. During glucose deprivation, a majority of AUF1 shuttled from cytoplasm to nucleus, resulting in dissociation of AUF1 from FST mRNA and thus stabilization of FST mRNA. Finally, knockdown of AUF1 decreased whereas overexpression of AUF1 increased glucose deprivation-induced apoptosis. The apoptosis promoting effect of AUF1 was eliminated in FST expressing cells. Collectively, this study provided evidence that AUF1 is a negative regulator of FST expression and participates in the regulation of cell survival under glucose deprivation.

Angiogenin stimulates ribosomal RNA transcription by epigenetic activation of the ribosomal DNA promoter

Angiogenin (ANG) undergoes nuclear translocation and promotes ribosomal RNA (rRNA) transcription thereby enhancing cell growth and proliferation. However, the mode of action of ANG in stimulating rRNA transcription is unclear. Here, we show that ANG enhances the formation of RNA polymerase I (Pol I) pre-initiation complex at the ribosomal DNA (rDNA) promoter. ANG binds at the upstream control element (UCE) of the promoter and enhances promoter occupancy of RNA Pol I as well as the selectivity factor SL1 components TAFI 48 and TAFI 110. We also show that ANG increases the number of actively transcribing rDNA by epigenetic activation through promoter methylation and histone modification. ANG binds to histone H3, inhibits H3K9 methylation, and activates H3K4 methylation as well as H4 acetylation at the rDNA promoter. These data suggest that one of the mechanisms by which ANG stimulates rRNA transcription is through an epigenetic activation of rDNA promoter.

Follistatin as potential therapeutic target in prostate cancer

Follistatin is a single-chain glycosylated protein whose primary function consists in binding and neutralizing some members of the transforming growth factor-β superfamily such as activin and bone morphogenic proteins. Emerging evidence indicates that this molecule may also play a role in the malignant progression of several human tumors including prostate cancer. In particular, recent findings suggest that, in this tumor, follistatin may also contribute to the formation of bone metastasis through multiple mechanisms, some of which are not related to its specific activin or bone morphogenic proteins' inhibitory activity. This review provides insight into the most recent advances in understanding the role of follistatin in the prostate cancer progression and discusses the clinical and therapeutic implications related to these findings.

N-myc downstream-regulated gene 1/Cap43 may function as tumor suppressor in endometrial cancer

PURPOSE

N-myc downstream-regulated gene 1 (NDRG1) reportedly regulates tumor progression in various cancers. Our previous studies showed that NDRG1 was aberrantly overexpressed in human endometrial cancer tissues. The purpose of the present study was to investigate the role of NDRG1 in endometrial carcinogenesis.

METHODS

A short hairpin RNA (shRNA)-mediated gene silencing strategy was employed to stably suppress the expression of NDRG1 in endometrial cancer Ishikawa cells. The influence of NDRG1 silencing on cancer cell biological behaviors was examined through observing in vitro tumor cell proliferation, colony formation, cell migration and invasion. Moreover, the mammalian NDRG1 expression vector pcDNA3.1(+)/NDRG1 was constructed to determine the effects of NDRG1 overexpression on cell proliferation and migration. Additionally, gene expression microarray analysis was conducted to identify NDRG1 downstream target genes after NDRG1 knockdown.

RESULTS

It was demonstrated that NDRG1 knockdown significantly enhanced Ishikawa cell proliferation and dramatically promoted cell migration and invasion. Furthermore, overexpression of NDRG1 in Ishikawa cells greatly inhibited cell proliferation and migration. Through microarray analysis and data mining, a large cohort of NDRG1-repressed target genes were identified. Additionally, through comparing the current microarray results with those obtained previously in studies of cervical and ovarian cancer cells conducted by us, 19 more specific common downstream target genes were identified.

CONCLUSIONS

It was demonstrated that NDRG1 might carry out a tumor suppressor function during endometrial carcinogenesis. The identification of downstream target genes should afford meaningful hints for prospective investigations. The tumor suppressor function of NDRG1 may open a new window for the target therapy of endometrial cancer.

Carbon source metabolism and its regulation in cancer cells

Cancer cell proliferation and progression require sufficient supplies of nutrients including carbon sources, nitrogen sources, and molecular oxygen. Particularly, carbon sources and molecular oxygen are critical for the generation of ATP and building blocks, and for the maintenance of intracellular redox status. However, solid tumors frequently outgrow the blood supply, resulting in nutrient insufficiency. Accordingly, cancer cell metabolism shows aberrant biochemical features that are consequences of oncogenic signaling and adaptation. Those adaptive metabolism features, including the Warburg effect and addiction to glutamine, may form the biochemical basis for resistance to chemotherapy and radiation. A better understanding of the regulatory mechanisms that link the signaling pathways to adaptive metabolic reprogramming may identify novel biomarkers for drug development. In this review, we focus on the regulation of carbon source utilization at a cellular level, emphasizing its relevance to proliferative biosynthesis in cancer cells. We summarize the essential needs of proliferating cells and the metabolic features of glucose, lipids, and glutamine, and we review the roles of transcription regulators (i.e., HIF-1, c-Myc, and p53) and two major oncogenic signaling pathways (i.e., PI3K-Akt and MAPK) in regulating the utilization of carbon sources. Finally, the effects of glucose on cell proliferation and perspective from both biochemical and cellular angles are discussed.

NoD: a Nucleolar localization sequence detector for eukaryotic and viral proteins

Background

Nucleolar localization sequences (NoLSs) are short targeting sequences responsible for the localization of proteins to the nucleolus. Given the large number of proteins experimentally detected in the nucleolus and the central role of this subnuclear compartment in the cell, NoLSs are likely to be important regulatory elements controlling cellular traffic. Although many proteins have been reported to contain NoLSs, the systematic characterization of this group of targeting motifs has only recently been carried out.

Results

Here, we describe NoD, a web server and a command line program that predicts the presence of NoLSs in proteins. Using the web server, users can submit protein sequences through the NoD input form and are provided with a graphical output of the NoLS score as a function of protein position. While the web server is most convenient for making prediction for just a few proteins, the command line version of NoD can return predictions for complete proteomes. NoD is based on our recently described human-trained artificial neural network predictor. Through stringent independent testing of the predictor using available experimentally validated NoLS-containing eukaryotic and viral proteins, the NoD sensitivity and positive predictive value were estimated to be 71% and 79% respectively.

Conclusions

NoD is the first tool to provide predictions of nucleolar localization sequences in diverse eukaryotes and viruses. NoD can be run interactively online at http://www.compbio.dundee.ac.uk/nod or downloaded to use locally.

Follistatin regulates germ cell nest breakdown and primordial follicle formation

Follistatin (FST) is an antagonist of activin and related TGFβ superfamily members that has important reproductive actions as well as critical regulatory functions in other tissues and systems. FST is produced as three protein isoforms that differ in their biochemical properties and in their localization within the body. We created FST288-only mice that only express the short FST288 isoform and previously reported that females are subfertile, but have an excess of primordial follicles on postnatal day (PND) 8.5 that undergo accelerated demise in adults. We have now examined germ cell nest breakdown and primordial follicle formation in the critical PND 0.5-8.5 period to test the hypothesis that the excess primordial follicles derive from increased proliferation and decreased apoptosis during germ cell nest breakdown. Using double immunofluorescence microscopy we found that there is virtually no germ cell proliferation after birth in wild-type or FST288-only females. However, the entire process of germ cell nest breakdown was extended in time (through at least PND 8.5) and apoptosis was significantly reduced in FST288-only females. In addition, FST288-only females are born with more germ cells within the nests. Thus, the excess primordial follicles in FST288-only mice derive from a greater number of germ cells at birth as well as a reduced rate of apoptosis during nest breakdown. These results also demonstrate that FST is critical for normal regulation of germ cell nest breakdown and that loss of the FST303 and/or FST315 isoforms leads to excess primordial follicles with accelerated demise, resulting in premature cessation of ovarian function.