Complementation of non-tumorigenicity of HPV18-positive cervical carcinoma cells involves differential mRNA expression of cellular genes including potential tumor suppressor genes on chromosome 11q13

Fra-1 Inhibits Cell Growth and the Warburg Effect in Cervical Cancer Cells via STAT1 Regulation of the p53 Signaling Pathway

The oncogenesis of cervical cancer is a multi-factor and multi-step process, and major risk factors include oncogene activation with tumor suppressor gene inactivation, viral factors, and immune factors. For example, the human papillomavirus (HPV) has been linked to the occurrence of cervical cancer. At present, the pathogenesis of cervical cancer remains unclear. Fra-1 (Fos-related antigen 1, also known as FOSL1) is a member of the Fos family and an important nuclear transcription factor that regulates normal cell growth, differentiation, and apoptosis. In the present study, we found that Fra-1 inhibited the proliferation of cervical cancer cells while also promoting apoptosis and affecting cell cycle distribution. Moreover, Fra-1 up-regulated STAT1 expression and modulated p53 signal pathway activity in cervical cancer cells. Overexpression of Fra-1 inhibited cell senescence by altering sirtuin 1 (SIRT1) expression in HeLa cells, and Fra-1 overexpression restored mitochondrial disorder and suppressed metabolic reprogramming in HeLa cells. Silencing of STAT1 impaired the inhibitory effect of Fra-1 on cervical cancer cell growth, while knock-down of STAT1 reversed the effect on cell senescence and mitochondrial dysfunction caused by Fra-1 in HeLa cells. Silencing of STAT1 also recovered metabolic reprogramming in cervical cancer cells. In summary, our results show that Fra-1 inhibited cervical cancer cell growth and the Warburg effect via STAT1-mediated regulation of the p53 signaling pathway.

Role of GARP in the activation of latent TGF-β1

TGF-β1, 2 and 3 cytokines are involved in many cellular processes including cell proliferation, differentiation, migration and survival. Whereas TGF-β2 and 3 play important roles in embryonic development, TGF-β1 is mostly implicated in controlling immune responses after birth. The production of TGF-β1 is a tightly regulated process, occurring mostly at a post-translational level. Virtually all cells produce the latent, inactive form of TGF-β1. In latent TGF-β1, the mature TGF-β1 dimer is non-covalently associated to the Latency Associated Peptide, or LAP, which prevents binding to the TGF-β1 receptor. Activation of the cytokine implies release of mature TGF-β1 from LAP. Only a few cell types activate latent TGF-β1, via mechanisms that are cell type specific. Proteins such as integrins, proteases and thrombospondin-1 activate TGF-β1 in epithelial cells, fibroblasts and dendritic cells. More recently, the protein GARP was shown to be involved in TGF-β1 activation by regulatory T cells (Treg), a subset of CD4⁺ T lymphocytes specialized in suppression of immune responses. GARP is a transmembrane protein that binds latent-TGF-β1 and tethers it on the Treg surface. The role of GARP was studied mostly in Tregs, and this was recently reviewed in L. Sun, H. Jin and H. Li, Oncotarget, 2016, 7, 42826-42836. However, GARP is also expressed in non-immune cells. This review focuses on the roles of GARP in latent TGF-β1 activation by immune and non-immune cells.

The role of platelet and endothelial GARP in thrombosis and hemostasis

BACKGROUND

Glycoprotein-A Repetitions Predominant protein (GARP or LRRC32) is present on among others human platelets and endothelial cells. Evidence for its involvement in thrombus formation was suggested by full knockout of GARP in zebrafish.

OBJECTIVES

To evaluate the role of GARP in platelet physiology and in thrombus formation using platelet and endothelial conditional GARP knock out mice.

METHODS

Platelet and endothelial specific GARP knockout mice were generated using the Cre-loxP recombination system. The function of platelets without GARP was measured by flow cytometry, spreading analysis and aggregometry using PAR4-activating peptide and collagen related peptide. Additionally, clot retraction and collagen-induced platelet adhesion and aggregation under flow were analyzed. Finally, in vivo tail bleeding time, occlusion time of the mesenteric and carotid artery after FeCl3-induced thrombosis were determined in platelet and endothelial specific GARP knock out mice.

RESULTS

Platelet specific GARP knockout mice had normal surface GPIb, GPVI and integrin αIIb glycoprotein expression. Although GARP expression was increased upon platelet activation, platelets without GARP displayed normal agonist induced activation, spreading on fibrinogen and aggregation responses. Furthermore, absence of GARP on platelets did not influence clot retraction and had no impact on thrombus formation on collagen-coated surfaces under flow. In line with this, neither the tail bleeding time nor the occlusion time in the carotid- and mesenteric artery after FeCl3-induced thrombus formation in platelet or endothelial specific GARP knock out mice were affected.

CONCLUSIONS

Evidence is provided that platelet and endothelial GARP are not important in hemostasis and thrombosis in mice.

FBLN4 as candidate gene associated with long-term and short-term survival with primary glioblastoma

Background

Glioblastoma multiforme (GBM) is the most common malignant and lethal type of primary central nervous system tumor in humans. In spite of its high lethality, a small percentage of patients have a relatively good prognosis, with median survival times of 36 months or longer. The identification of clinical subsets of GBM associated with distinct molecular genetic profiles has made it possible to design therapies tailored to treat individual patients.

Methods

We compared microarray data sets from long-term survivors (LTSs) and short-term survivors (STSs) to screen for prognostic biomarkers in GBM patients using the WebArrayDB platform. We focused on FBLN4, IGFBP-2, and CHI3L1, all members of a group of 10 of the most promising, differentially regulated gene candidates. Using formalin-fixed paraffin-embedded GBM samples, we corroborated the relationship between these genes and patient outcomes using methylation-specific polymerase chain reaction (PCR) for MGMT methylation status and quantitative reverse transcription PCR for expression of these genes.

Results

Expression levels of the mRNAs of these 3 genes were higher in the GBM samples than in normal brain samples and these 3 genes were significantly upregulated in STSs compared to the levels in LTS samples (P<0.01). Furthermore, Kaplan–Meier analysis showed that the expression patterns of FBLN4 and IGFBP-2 serve as independent prognostic indicators for overall survival (P<0.01 and P<0.05, respectively).

Conclusion

To our knowledge, this is the first report describing FBLN4 as a prognostic factor for GBM patient survival, demonstrating that increased GBM survival time correlates with decreased FBLN4 expression. Understanding FBLN4 expression patterns could aid in the creation of powerful tools to predict clinical prognoses of GBM patients.

Monoclonal antibodies against GARP/TGF-β1 complexes inhibit the immunosuppressive activity of human regulatory T cells in vivo

Regulatory T cells (Tregs) are essential to prevent autoimmunity, but excessive Treg function contributes to cancer progression by inhibiting antitumor immune responses. Tregs exert contact-dependent inhibition of immune cells through the production of active transforming growth factor-β1 (TGF-β1). On the Treg cell surface, TGF-β1 is in an inactive form bound to membrane protein GARP and then activated by an unknown mechanism. We demonstrate that GARP is involved in this activation mechanism. Two anti-GARP monoclonal antibodies were generated that block the production of active TGF-β1 by human Tregs. These antibodies recognize a conformational epitope that requires amino acids GARP137-139 within GARP/TGF-β1 complexes. A variety of antibodies recognizing other GARP epitopes did not block active TGF-β1 production by Tregs. In a model of xenogeneic graft-versus-host disease in NSG mice, the blocking antibodies inhibited the immunosuppressive activity of human Tregs. These antibodies may serve as therapeutic tools to boost immune responses to infection or cancer via a mechanism of action distinct from that of currently available immunomodulatory antibodies. Used alone or in combination with tumor vaccines or antibodies targeting the CTLA4 or PD1/PD-L1 pathways, blocking anti-GARP antibodies may improve the efficiency of cancer immunotherapy.

An Optimization-Driven Analysis Pipeline to Uncover Biomarkers and Signaling Paths: Cervix Cancer

Establishing how a series of potentially important genes might relate to each other is relevant to understand the origin and evolution of illnesses, such as cancer. High-throughput biological experiments have played a critical role in providing information in this regard. A special challenge, however, is that of trying to conciliate information from separate microarray experiments to build a potential genetic signaling path. This work proposes a two-step analysis pipeline, based on optimization, to approach meta-analysis aiming to build a proxy for a genetic signaling path.

Fra-1 is downregulated in cervical cancer tissues and promotes cervical cancer cell apoptosis by p53 signaling pathway in vitro

Cervical cancer is a potentially preventable disease; however, it is the third most commonly diagnosed cancer and the fourth leading cause of cancer deaths in women worldwide. Cervical cancer is thought to develop through a multistep process involving virus, tumor suppressor genes, proto-oncogenes and immunological factors. It is known that human papillomavirus (HPV) infection is necessary but insufficient to cause malignancy. At present, the etiology of cervical carcinoma remains poorly understood. In this study, we found that the expression of FOS-like antigen-1 (Fra-1) gene was downregulated in cervical cancer compared with the adjacent non-cancerous tissues by RT-qPCR, immunohistochemistry (IHC) and western blotting techniques. To uncover the effect of Fra-1 on cervical cancer, we tested and confirmed that Fra-1 significantly inhibited the proliferation of HeLa cells by MMT assays in vitro. At the same time, overexpression of Fra-1 promoted apoptosis of HeLa cells. To explore the possible mechanism of Fra-1 in cervical cancer, we tested the expression levels of key molecules in p53 signaling pathway by western blotting technology. The results showed that p53 was downregulated in cervical cancer compared with the adjacent non-cancerous tissues, but MDM2 proto-oncogene, E3 ubiquitin protein ligase (MDM2) was upregulated in cervical cancer. In vitro, the p53 was upregulated and MDM2 was downregulated in HeLa cells with Fra-1 overexpression. In summary, our results suggested that Fra-1 expression is low in cervical cancer tissues and promotes apoptosis of cervical cancer cells by p53 signaling pathway.

Nuclear matrix protein SMAR1 represses c-Fos-mediated HPV18 E6 transcription through alteration of chromatin histone deacetylation

Matrix attachment region (MAR)-binding proteins have been implicated in the transcriptional regulation of host as well as viral genes, but their precise role in HPV-infected cervical cancer remains unclear. Here we show that HPV18 promoter contains consensus MAR element in the LCR and E6 sequences where SMAR1 binds and reinforces HPV18 E6 transcriptional silencing. In fact, curcumin-induced up-regulation of SMAR1 ensures recruitment of SMAR1-HDAC1 repressor complex at the LCR and E6 MAR sequences, thereby decreasing histone acetylation at H3K9 and H3K18, leading to reorientation of the chromatin. As a consequence, c-Fos binding at the putative AP-1 sites on E6 promoter is inhibited. E6 depletion interrupts degradation of E6-mediated p53 and lysine acetyl transferase, Tip60. Tip60, in turn, acetylates p53, thereby restoring p53-mediated transactivation of proapoptotic genes to ensure apoptosis. This hitherto unexplained function of SMAR1 signifies the potential of this unique scaffold matrix-associated region-binding protein as a critical regulator of E6-mediated anti-apoptotic network in HPV18-infected cervical adenocarcinoma. These results also justify the candidature of curcumin for the treatment of HPV18-infected cervical carcinoma.