Blockage of STAT3 signaling pathway with a decoy oligodeoxynucleotide inhibits growth of human ovarian cancer cells

A Deoxyribonucleic Acid Decoy Trapping DUX4 for the Treatment of Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral dystrophy (FSHD) is characterized by a loss of repressive epigenetic marks leading to the aberrant expression of the DUX4 transcription factor. In muscle, DUX4 acts as a poison protein though the induction of multiple downstream genes. So far, there is no therapeutic solution for FSHD. Because DUX4 is a transcription factor, we developed an original therapeutic approach, based on a DNA decoy trapping the DUX4 protein, preventing its binding to genomic DNA and thereby blocking the aberrant activation of DUX4’s transcriptional network. In vitro, transfection of a DUX4 decoy into FSHD myotubes reduced the expression of the DUX4 network genes. In vivo, both double-stand DNA DUX4 decoys and adeno-associated viruses (AAVs) carrying DUX4 binding sites reduced transcriptional activation of genes downstream of DUX4 in a DUX4-expressing mouse model. Our study demonstrates, both in vitro and in vivo, the feasibility of the decoy strategy and opens new avenues of research.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

Novel Nanocomplexes Targeting STAT3 Demonstrate Promising Anti-Ovarian Cancer Effects in vivo

Background

Cationic solid lipid nanoparticles (SLN) have attracted intensive interest as an effective gene delivery system for its high biocompatibility, stability and low cytotoxicity. In our previous study, we successfully prepared SLN-STAT3 decoy ODN complexes and made a primary study on its antitumor behavior in ovarian cancer cells in vitro. However, there is little information available so far about the effect of SLN-STAT3 decoy ODN complexes on ovarian cancer in vivo, either little information about the pharmacological toxicology in vivo.

Material and Methods

We applied nanotechnology to improve the gene delivery system and synthesize SLN-STAT3 decoy ODN complexes. Xenograft mouse models were established to assess the antitumor effects of SLN-STAT3 decoy ODN on the tumor growth of ovarian cancer in vivo. To analyze the mechanisms of SLN-STAT3 decoy ODN, we investigated apoptosis, autophagy, epithelial–mesenchymal transition (EMT) in tumor tissues of nude mice and investigated the effects and toxicology of SLN-STAT3 decoy ODN complexes on the vital organs of nude mice.

Results

The results showed that SLN-STAT3 decoy ODN complexes markedly inhibited tumor growth in vivo. SLN-STAT3 decoy ODN complexes could induce cell apoptosis through downregulating Bcl-2, survivin and pro caspase 3, but upregulating Bax and cleaved caspase 3. These complexes could also regulate autophagy through upregulating LC3A-II, LC3B-II and beclin-1, but downregulating p-Akt and p-mTOR. Moreover, these complexes could inhibit cancer cell invasion through reversing EMT. Besides, SLN-STAT3 decoy ODN complexes showed no obvious toxicity on vital organs and hematological parameters of nude mice.

Conclusion

The molecular mechanisms that SLN-STAT3 decoy ODN complexes inhibit tumor growth involved activating the apoptotic cascade, regulating autophagy, and reversing EMT program; and these complexes showed no obvious toxicity on nude mice. Our study indicated that the nanocomplexes SLN-STAT3 decoy ODN might be a promising therapeutic approach for ovarian cancer treatment.

Activation of STAT3 and STAT5 Signaling in Epithelial Ovarian Cancer Progression: Mechanism and Therapeutic Opportunity

Epithelial ovarian cancer (EOC) is the most lethal of all gynecologic malignancies. Despite advances in surgical and chemotherapeutic options, most patients with advanced EOC have a relapse within three years of diagnosis. Unfortunately, recurrent disease is generally not curable. Recent advances in maintenance therapy with anti-angiogenic agents or Poly ADP-ribose polymerase (PARP) inhibitors provided a substantial benefit concerning progression-free survival among certain women with advanced EOC. However, effective treatment options remain limited in most recurrent cases. Therefore, validated novel molecular therapeutic targets remain urgently needed in the management of EOC. Signal transducer and activator of transcription-3 (STAT3) and STAT5 are aberrantly activated through tyrosine phosphorylation in a wide variety of cancer types, including EOC. Extrinsic tumor microenvironmental factors in EOC, such as inflammatory cytokines, growth factors, hormones, and oxidative stress, can activate STAT3 and STAT5 through different mechanisms. Persistently activated STAT3 and, to some extent, STAT5 increase EOC tumor cell proliferation, survival, self-renewal, angiogenesis, metastasis, and chemoresistance while suppressing anti-tumor immunity. By doing so, the STAT3 and STAT5 activation in EOC controls properties of both tumor cells and their microenvironment, driving multiple distinct functions during EOC progression. Clinically, increasing evidence indicates that the activation of the STAT3/STAT5 pathway has significant correlation with reduced survival of recurrent EOC, suggesting the importance of STAT3/STAT5 as potential therapeutic targets for cancer therapy. This review summarizes the distinct role of STAT3 and STAT5 activities in the progression of EOC and discusses the emerging therapies specifically targeting STAT3 and STAT5 signaling in this disease setting.

Physapubescin B inhibits tumorgenesis and circumvents taxol resistance of ovarian cancer cells through STAT3 signaling

Ovarian cancer is the most lethal gynaecological malignancy. Recurrence and subsequent resistance to chemotherapy have become major obstacles to treating these diseases. In the present study, we showed that a natural withanolide isolated from the plant Physalis pubescens L. (Solanaceae), Physapubescin B, exhibited potent anti-tumor activity against ovarian cancer cells. Physapubescin B promoted apoptosis, induced cell-cycle arrest and inhibited invasion of ES-2 and A2780 cells. Physapubescin B treatment also resulted in suppression of the transcriptional activity of STAT3, an oncogenic transcription factor activated in many human malignancies including ovarian cancer, through disturbing the dimerization of STAT3, and thereby inhibited the nuclear translocation of Tyr705/Ser727-phosphorylated STAT3. The IL-6-stimulated activation of STAT3 and its downstream genes Cyclin D1, survivin, and Bcl-xL was also repressed by Physapubescin B. Furthermore, Physapubescin B sensitizes A2780 cells to taxol-induced cell growth inhibition in vitro. These findings strongly suggest that Physapubescin B has potential antitumor activity and may circumvent taxol resistance in human ovarian cancer cells through inhibition of aberrant activation of STAT3.

Transcription factor decoy: a pre-transcriptional approach for gene downregulation purpose in cancer

Gene therapy as a therapeutic approach has been the dream for many scientists around the globe. Many strategies have been proposed and applied for this purpose, yet the void for a functional safe method is still apparent. Since most of the diseases are caused by undesirable upregulation (oncogenes) or downregulation (tumor suppressor genes) of genes, major gene therapy's techniques affect gene expression. Most of the methods are used in post-transcriptional level such as RNA inhibitory (RNAi) and splice-switching oligonucleotides (SSOs). RNAi blocks messenger RNA (mRNA) translation by mRNA degradation or interruption between attachments of mRNA with ribosomes' subunits. However, one of the novel methods is the usage of transcription factor targeted decoys. DNA decoys are the new generation of functional gene downregulatory oligonucleotides which compete with specific binding sites of transcription factors. Considering the exponential growth of this technique in both in vitro and in vivo studies, in this paper, we aim to line out the description, design, and application of decoys in research and therapy.

HIF-1α decoy oligodeoxynucleotides inhibit HIF-1α signaling and breast cancer proliferation

Although HIF-1α is considered an attractive target for the development of cancer therapies, like other transcriptional factors, it has been regarded as 'undruggable'. The decoy approach is a new class of antigene strategy that can be used to modulate the function of endogenous transcriptional factors. Here, we designed a decoy oligodeoxynucleotide (ODN) and tested its effect on the function of HIF-1α. We found the HIF-1α decoy ODN could efficiently enter into cells. Furthermore, these decoy ODNs can significantly block the expression of VEGFA, a known targeted gene of HIF-1α suggesting that the HIF-1α decoy ODNs can inhibit the function of HIF-1α. More importantly, the HIF-1α decoy ODN induced apoptosis and cell cycle arrest in MDA-MB-231 breast cancer cells. In summary, HIF-1α decoy ODNs can inhibit the function of HIF-1α and induce cancer cell apoptosis. Therefore, HIF-1α decoy ODNs should be further modified to improve their biological activity in vivo.

Preclinical therapeutic potential of a nitrosylating agent in the treatment of ovarian cancer

This study examines the role of s-nitrosylation in the growth of ovarian cancer using cell culture based and in vivo approaches. Using the nitrosylating agent, S-nitrosoglutathione (GSNO), a physiological nitric oxide molecule, we show that GSNO treatment inhibited proliferation of chemoresponsive and chemoresistant ovarian cancer cell lines (A2780, C200, SKVO3, ID8, OVCAR3, OVCAR4, OVCAR5, OVCAR7, OVCAR8, OVCAR10, PE01 and PE04) in a dose dependent manner. GSNO treatment abrogated growth factor (HB-EGF) induced signal transduction including phosphorylation of Akt, p42/44 and STAT3, which are known to play critical roles in ovarian cancer growth and progression. To examine the therapeutic potential of GSNO in vivo, nude mice bearing intra-peritoneal xenografts of human A2780 ovarian carcinoma cell line (2×10⁶) were orally administered GSNO at the dose of 1 mg/kg body weight. Daily oral administration of GSNO significantly attenuated tumor mass (p<0.001) in the peritoneal cavity compared to vehicle (phosphate buffered saline) treated group at 4 weeks. GSNO also potentiated cisplatin mediated tumor toxicity in an A2780 ovarian carcinoma nude mouse model. GSNO’s nitrosylating ability was reflected in the induced nitrosylation of various known proteins including NFκB p65, Akt and EGFR. As a novel finding, we observed that GSNO also induced nitrosylation with inverse relationship at tyrosine 705 phosphorylation of STAT3, an established player in chemoresistance and cell proliferation in ovarian cancer and in cancer in general. Overall, our study underlines the significance of S-nitrosylation of key cancer promoting proteins in modulating ovarian cancer and proposes the therapeutic potential of nitrosylating agents (like GSNO) for the treatment of ovarian cancer alone or in combination with chemotherapeutic drugs.

Molecular epigenetics in the management of ovarian cancer: are we investigating a rational clinical promise?

Epigenetics is essentially a phenotypical change in gene expression without any alteration of the DNA sequence; the emergence of epigenetics in cancer research and mainstream oncology is fueling new hope. However, it is not yet known whether this knowledge will translate to improved clinical management of ovarian cancer. In this malignancy, women are still undergoing chemotherapy similar to what was approved in 1978, which to this day represents one of the biggest breakthroughs for treating ovarian cancer. Although liquid tumors are benefiting from epigenetically related therapies, solid tumors like ovarian cancer are not (yet?). Herein, we will review the science of molecular epigenetics, especially DNA methylation, histone modifications and microRNA, but also include transcription factors since they, too, are important in ovarian cancer. Pre-clinical and clinical research on the role of epigenetic modifications is also summarized. Unfortunately, ovarian cancer remains an idiopathic disease, for the most part, and there are many areas of patient management, which could benefit from improved technology. This review will also highlight the evidence suggesting that epigenetics may have pre-clinical utility in pharmacology and clinical applications for prognosis and diagnosis. Finally, drugs currently in clinical trials (i.e., histone deacetylase inhibitors) are discussed along with the promise for epigenetics in the exploitation of chemoresistance. Whether epigenetics will ultimately be the answer to better management in ovarian cancer is currently unknown; but we hope so in the future.