Inhibitory Effects of STAT3 Transcription Factor by Synthetic Decoy ODNs on Autophagy in Renal Fibrosis

Autophagy in the proximal tubules may promote fibrosis by activating tubular cell death, interstitial inflammation, and the production of pro-fibrotic factors. The signal transducer and activator of transcription 3 (STAT3) is activated as a potential transcription factor, which mediates the stimulation of renal fibrosis. We investigated the role of the STAT3 in autophagy and its effect on the prevention of interstitial renal fibrosis. In this study, we use synthesized STAT3 decoy oligonucleotides (ODN), which were injected into the tail veins of unilateral ureteral obstruction (UUO) mice, to explore the regulation of autophagy in UUO-induced renal fibrosis. The expression of interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and collagen were decreased by STAT3 decoy ODN. The autophagy markers microtubule-associated protein light chain 3 (LC3) and fibronectin, were identified through immunofluorescent staining, indicating that they were reduced in the group injected with ODN. The expressions of LC3, Beclin1, p62, and autophagy-related 5–12 (Atg5–12) and hypoxia inducible factor-1α (HIF-1α) were inhibited in the ODN injection group. We determined the inhibitory effect of autophagy in chronic kidney disease and confirmed that STAT3 decoy ODN effectively inhibited autophagy by inhibiting the expression of STAT3 transcription factors in the UUO group.

STAT3 decoy oligonucleotide-carrying microbubbles with pulsed ultrasound for enhanced therapeutic effect in head and neck tumors

Signal transducer and activator of transcription-3 (STAT3) is an oncogenic transcription factor implicated in carcinogenesis, tumor progression, and drug resistance in head and neck squamous cell carcinoma (HNSCC). A decoy oligonucleotide targeting STAT3 offers a promising anti-tumor strategy, but achieving targeted tumor delivery of the decoy with systemic administration poses a significant challenge. We previously showed the potential for STAT3 decoy-loaded microbubbles, in conjunction with ultrasound targeted microbubble cavitation (UTMC), to decrease tumor growth in murine squamous cell carcinoma. As a next step towards clinical translation, we sought to determine the anti-tumor efficacy of our STAT3 decoy delivery platform against human HNSCC and the effect of higher STAT3 decoy microbubble loading on tumor cell inhibition. STAT3 decoy was loaded on cationic lipid microbubbles (STAT3-MB) or loaded on liposome-conjugated lipid microbubbles to form STAT3-loaded liposome-microbubble complexes (STAT3-LPX). UTMC treatment efficacy with these two formulations was evaluated in vitro using viability and apoptosis assays in CAL33 (human HNSCC) cells. Anti-cancer efficacy in vivo was performed in a CAL33 tumor murine xenograft model. UTMC with STAT3-MB caused significantly lower CAL33 cell viability compared to UTMC with STAT3-LPX (56.8±8.4% vs 84.5±8.8%, respectively, p<0.05). In vivo, UTMC with STAT3-MB had strong anti-tumor effects, with significantly less tumor burden and greater survival compared to that of UTMC with microbubbles loaded with a mutant control decoy and untreated control groups (p<0.05). UTMC with STAT3 decoy-loaded microbubbles significantly decreases human HNSSC tumor progression. These data set the stage for clinical translation of our microbubble platform as an imaged-guided, targeted delivery strategy for STAT3 decoy, or other nucleotide-based therapeutics, in human cancer treatment.

Beneficial effect of STAT3 decoy oligodeoxynucleotide transfection on organ injury and mortality in mice with cecal ligation and puncture-induced sepsis

Sepsis is a major clinical challenge with unacceptably high mortality. The signal transducers and activators of transcription (STAT) family of transcription factors is known to activate critical mediators of cytokine responses, and, among this family, STAT3 is implicated to be a key transcription factor in both immunity and inflammatory pathways. We investigated whether in vivo introduction of synthetic double-stranded STAT3 decoy oligodeoxynucleotides (ODNs) can provide benefits for reducing organ injury and mortality in mice with cecal ligation and puncture (CLP)-induced polymicrobial sepsis. We found that STAT3 was rapidly activated in major end-organ tissues following CLP, which was accompanied by activation of the upstream kinase JAK2. Transfection of STAT3 decoy ODNs downregulated pro-inflammatory cytokine/chemokine overproduction in CLP mice. Moreover, STAT3 decoy ODN transfection significantly reduced the increases in tissue mRNAs and proteins of high mobility group box 1 (HMGB1) and strongly suppressed the excessive elevation in serum HMGB1 levels in CLP mice. Finally, STAT3 decoy ODN administration minimized the development of sepsis-driven major end-organ injury and led to a significant survival advantage in mice after CLP. Our results suggest a critical role of STAT3 in the sepsis pathophysiology and the potential usefulness of STAT3 decoy ODNs for sepsis gene therapy.

4373 Defining the role of non-canonical PIK3CA mutations in head and neck squamous cell carcinoma

OBJECTIVES/GOALS: To characterize the oncogenic potential of HNSCC cell lines harboring 17 non-canonical PIK3CA mutations. METHODS/STUDY POPULATION: Non-canonical PIK3CA mutant constructs generated via site-directed mutagenesis are subcloned into doxycycline-inducible vector pLVX-Puro. Serum-dependent HNSCC cell line (PCI-52-SD1) is then stably transfected with vectors and undergo doxycycline-induction. Cell survival is determined by depriving cells of fetal bovine serum for 72 hours and quantifying remaining cells with 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Cell proliferation and migration is evaluated with colony formation assays and transwell assays respectively. RESULTS/ANTICIPATED RESULTS: To date, the survival behavior of eight non-canonical mutants was assessed. Three mutants – Q75E, V71I, and E970K – exhibited 18.7-26.7% greater survival rate relative to cells transfected with wild-type. Five mutants – R519G, Y606C, W328S, C905S, and M1040I – demonstrated survival rates that differed only by −4.3% to +6.6% relative to wild-type. We hypothesize the three activating mutants that exhibited increased survival will also demonstrate increased cell proliferation and migratory behavior whereas the three neutral mutants will not differ from control. DISCUSSION/SIGNIFICANCE OF IMPACT: Ongoing HNSCC PI3K inhibitor trials could be more effective if all PIK3CA hyperactivation mutations are known. Identifying non-canonical mutation effects could result in greater efficacy if drugs are restricted only to those with activating mutations. CONFLICT OF INTEREST DESCRIPTION: JRG and DEJ are co-inventors of cyclic STAT3 decoy and have financial interests in STAT3 Therapeutics, Inc. STAT3 Therapeutics, Inc. holds an interest in a cyclic STAT3 decoy oligonucleotide. The remaining authors declare no conflicts.

Targeting STAT3 in Cancer with Nucleotide Therapeutics

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in promoting the proliferation and survival of tumor cells. As a ubiquitously-expressed transcription factor, STAT3 has commonly been considered an “undruggable” target for therapy; thus, much research has focused on targeting upstream pathways to reduce the expression or phosphorylation/activation of STAT3 in tumor cells. Recently, however, novel approaches have been developed to directly inhibit STAT3 in human cancers, in the hope of reducing the survival and proliferation of tumor cells. Several of these agents are nucleic acid-based, including the antisense molecule AZD9150, CpG-coupled STAT3 siRNA, G-quartet oligodeoxynucleotides (GQ-ODNs), and STAT3 decoys. While the AZD9150 and CpG-STAT3 siRNA interfere with STAT3 expression, STAT3 decoys and GQ-ODNs target constitutively activated STAT3 and modulate its ability to bind to target genes. Both STAT3 decoy and AZD9150 have advanced to clinical testing in humans. Here we will review the current understanding of the structures, mechanisms, and potential clinical utilities of the nucleic acid-based STAT3 inhibitors.