Fluoroquinolones upregulate insulin-like growth factor-binding protein 3, inhibit cell growth and insulin-like growth factor signaling.

Fluoroquinolones (FQs), commonly known for their antibiotic properties, exhibit additional pharmacological potential with anti-proliferative effects on various malignant cell types and immunomodulatory responses. Despite these observed effects, the precise mechanisms of action remain elusive. This study elucidates the biological impact of FQs on insulin-like growth factor-binding protein 3 (IGFBP-3) productions in a p53-dependent manner. Cultured cells and mouse models treated with FQs demonstrated increased IGFBP-3 mRNA expression and protein secretion. The FQ-induced IGFBP-3 was identified to impede cell growth by inhibiting IGF-I signaling and exerting effects through an IGF-independent pathway. Notably, FQ-mediated suppression of cell proliferation was reversed in p53-null and p53 knockdown cells, suggesting the pivotal role of p53 in FQ-induced IGFBP-3 production and IGFBP-3-mediated growth inhibition. Additionally, ciprofloxacin, a clinically used FQ, exhibited the induction of tumor cell apoptosis and attenuation of tumor growth in a syngeneic mouse hepatocellular carcinoma (HCC) model. These findings unveil a novel mechanism through which FQs act as anti-proliferative agents, prompting further exploration of their potential utility or derivative compounds in cancer treatment and prevention.

Prodigiosin Inhibits Transforming Growth Factor ß Signaling by Interfering Receptor Recycling and Subcellular Translocation in Epithelial Cells.

Prodigiosin (PG) is a naturally occurring polypyrrole red pigment produced by numerous microorganisms including some Serratia and Streptomyces strains. PG has exhibited promising anticancer activity; however, the molecular mechanisms of action of PG on malignant cells remain ambiguous. Transforming growth factor-ß (TGF-ß) is a multifunctional cytokine that governs a wide array of cellular processes in development and tissue homeostasis. Malfunctions of TGF-ß signaling are associated with numerous human cancers. Emerging evidence underscores the significance of internalized TGF-ß receptors and their intracellular trafficking in initiating signaling cascades. In this study, we identified PG as a potent inhibitor of the TGF-ß pathway. PG blocked TGF-ß signaling by targeting multiple sites of this pathway, including facilitating the sequestering of TGF-ß receptors in the cytoplasm by impeding the recycling of type II TGF-ß receptors to the cell surface. Additionally, PG prompts a reduction in the abundance of receptors on the cell surface through the disruption of the receptor glycosylation. In human Caucasian lung carcinoma cells and human hepatocellular cancer cell line cells, nanomolar concentrations of PG substantially diminish TGF-ß-triggered phosphorylation of Smad2 protein. This attenuation is further reflected in the suppression of downstream target gene expression, including those encoding fibronectin, plasminogen activator inhibitor-1, and N-cadherin. SIGNIFICANCE STATEMENT: Prodigiosin (PG) emerges from this study as a potent TGF-ß pathway inhibitor, disrupting receptor trafficking and glycosylation and reducing TGF-ß signaling and downstream gene expression. These findings not only shed light on PG's potential therapeutic role but also present a captivating avenue towards future anti-TGF-ß strategies.

Suppression of TGFß-Induced Interleukin-6 Secretion by Sinulariolide from Soft Corals through Attenuation of the p38-NF-kB Pathway in Carcinoma Cells.

Sinulariolide (SC-1) is a natural product extracted from the cultured-type soft coral Sinularia flexibilis and possesses anti-inflammation, anti-proliferative, and anti-migratory in several types of cancer cells. However, the molecular pathway behind its effects on inflammation remains poorly understood. Since inflammatory cytokines such as TGFß, TNFα, IL-1, IL-6, and IL-8 activate transcription factors such as Smads, NF-κB, STAT3, Snail, Twist, and Zeb that drive the epithelial-to-mesenchymal transition (EMT), in this study, we focus on the investigation in effects of SC-1 on TGFß-induced interleukin-6 (IL-6) releases in an in vitro cell culture model. We showed that both intracellular IL-6 expression and secretion were stimulated by TGFß and associated with strong upregulation of IL-6 mRNA and increased transcription in A549 cells. SC-1 blocked TGFß-induced secretion of IL-6 while showing no effect on the induction of fibronectin and plasminogen activator inhibitor-1 genes, indicating that SC-1 interferes with only a subset of TGFß activities. In addition, SC-1 inhibits TGFß-induced IL-6 by suppressing p38 MAPK signaling and subsequently inhibits NF-κB and its nuclear translocation without affecting the canonical Smad pathway and receptor turnover. Overall, these data suggest that p38 may involve in the inhibition of SC-1 in IL-6 release, thus illustrating an inhibitory effect for SC-1 in the suppression of inflammation, EMT phenotype, and tumorigenesis.

Fluoroquinolones Suppress TGF-ß and PMA-Induced MMP-9 Production in Cancer Cells: Implications in Repurposing Quinolone Antibiotics for Cancer Treatment.

BACKGROUND: Fluoroquinolones (FQs) are potent antimicrobials with multiple effects on host cells and tissues. Although FQs can attenuate cancer invasion and metastasis, the underlying molecular mechanisms remain unclear. Matrix metalloproteinase-9 (MMP-9) has functional roles in tumor angiogenesis, invasion, and metastasis, and is associated with cancer progression and poor prognosis, suggesting that inhibitors of MMP-9 activity and transcription are prime candidates for cancer therapy. Despite numerous preclinical data supporting the use of MMP-9 inhibitors as anticancer drugs, the few available examples are not therapeutically useful due to low specificity and off-target effects. We examined the effects of FQs on MMP-9 production in cancer cells following transforming growth factor beta (TGF-ß) and phorbol 12-myristate 13-acetate (PMA) stimulation. EXPERIMENTAL APPROACHES: Using confluent cultures of HepG2 and A549 cells, the effects of FQs (ciprofloxacin, levofloxacin, clinafloxacin, gatifloxacin, and enrofloxacin) on TGF-ß and PMA-induced MMP-9 mRNA expression and production were studied in RNA extracts and culture supernatants, respectively. FQs specifically abrogated TGF-ß and PMA-induced MMP-9 levels and activity in a concentration and time-dependent manner, without affecting other MMPs or proteins involved in epithelial-mesenchymal transition. Additionally, FQs inhibited TGF-ß and PMA-induced cell migration via p38 and cyclic AMP signaling pathways. CONCLUSIONS AND IMPLICATIONS: Overall, we demonstrated that FQs inhibit cancer cell migration and invasion by downregulating MMP-9 expression and revealed the cellular mechanisms underlying their potential value in cancer treatment.

Garcimultiflorone K from Garcinia multiflora attenuates hepatocellular carcinoma metastasis by suppressing transforming growth factor-ß signaling.

BACKGROUND: Transforming growth factor­ß (TGF-ß) signaling is a crucial inducer of tissue fibrosis and extracellular matrix accumulation and a vital suppressor of epithelial cell proliferation and cancer metastasis. The nature of this multifunctional cytokine has prompted the development of TGF-ß signaling inhibitors as therapeutic agents. Our research group has recently isolated the polyprenylated polycyclic acylphloroglucinol garcimultiflorone K (GMK) from the stems of Garcinia multiflora; GMK exhibits antiangiogenic activity in endothelial cells. PURPOSE: In the current study, we aimed to explore the antitumor effect and detailed mechanisms of Garcimultiflorone K in hepatocellular carcinoma cells. METHODS: Cell proliferation and viability were evaluated using the MTT assay. The migratory ability of HepG2 cells was measured using wound healing assays. The inhibitory effect of GMK against the nuclear translocation of Smad by TGF-ß was assessed through immunofluorescence staining and Western blotting. To investigate TGF-ß-dependent gene expression profiles upon GMK stimulation, RNA transcript levels were determined using reverse transcription polymerase chain reaction. The effects of GMK in Smad2-driven transcriptomic activities were studied using a reporter gene assay. Protein levels were detected using Western blotting. RESULTS: Our data revealed that GMK inhibited TGF-ß-induced cellular responses, including Smad protein phosphorylation, cell migration, and extracellular matrix production, during epithelial-mesenchymal transition (EMT). Mechanistic studies further demonstrated that GMK suppressed TGF-ß signaling by downregulating TGF-ß receptor II (TßRII). CONCLUSION: These findings elucidate that TßRII expression in hepatic cells can be specifically suppressed by GMK to attenuate metastasis and the disease-promoting effects of EMT, representing a therapeutic approach.

Recent progress in TGF-ß inhibitors for cancer therapy.

Transforming growth factor-ß (TGF-ß) is a multifunctional cytokine that is involved in proliferation, metastasis, and many other important processes in malignancy. Inhibitors targeting TGF-ß have been considered by pharmaceutical companies for cancer therapy, and some of them are in clinical trial now. Unfortunately, several of these programs have recently been relinquished, and most companies that remain in the contest are progressing slowly and cautiously. This review summarizes the TGF-ß signal transduction pathway, its roles in oncogenesis and fibrotic diseases, and advancements in antibodies and small-molecule inhibitors of TGF-ß.

Roles of Myosin-Mediated Membrane Trafficking in TGF-ß Signaling.

Recent findings have revealed the role of membrane traffic in the signaling of transforming growth factor-ß (TGF-ß). These findings originate from the pivotal function of TGF-ß in development, cell proliferation, tumor metastasis, and many other processes essential in malignancy. Actin and unconventional myosin have crucial roles in subcellular trafficking of receptors; research has also revealed a growing number of unconventional myosins that have crucial roles in TGF-ß signaling. Unconventional myosins modulate the spatial organization of endocytic trafficking and tether membranes or transport them along the actin cytoskeletons. Current models do not fully explain how membrane traffic forms a bridge between TGF-ß and the downstream effectors that produce its functional responsiveness, such as cell migration. In this review, we present a brief overview of the current knowledge of the TGF-ß signaling pathway and the molecular components that comprise the core pathway as follows: ligands, receptors, and Smad mediators. Second, we highlight key role(s) of myosin motor-mediated protein trafficking and membrane domain segregation in the modulation of the TGF-ß signaling pathway. Finally, we review future challenges and provide future prospects in this field.

Sorafenib suppresses TGF-ß responses by inducing caveolae/lipid raft-mediated internalization/degradation of cell-surface type II TGF-ß receptors: Implications in development of effective adjunctive therapy for hepatocellular carcinoma.

Sorafenib is the only FDA approved drug for the treatment of advanced hepatocellular carcinoma (HCC) and other malignancies. Studies indicate that TGF-ß signalling is associated with tumour progression in HCC. Autocrine and paracrine TGF-ß promotes tumour growth and malignancy by inducing epithelial-mesenchymal transition (EMT). Sorafenib is believed to antagonize tumour progression by inhibiting TGF-ß-induced EMT. It improves survival of patients but HCC later develops resistance and relapses. The underlying mechanism of resistance is unknown. Understanding of the molecular mechanism of sorafenib inhibition of TGF-ß-induced signalling or responses in HCC may lead to development of adjunctive effective therapy for HCC. In this study, we demonstrate that sorafenib suppresses TGF-ß responsiveness in hepatoma cells, hepatocytes, and animal liver, mainly by downregulating cell-surface type II TGF-ß receptors (TßRII) localized in caveolae/lipid rafts and non-lipid raft microdomains via caveolae/lipid rafts-mediated internalization and degradation. Furthermore, sorafenib-induced downregulation and degradation of cell-surface TßRII is prevented by simultaneous treatment with a caveolae disruptor or lysosomal inhibitors. On the other hand, sorafenib only downregulates cell-surface TßRII localized in caveolae/lipid rafts but not localized in non-lipid raft microdomains in hepatic stellate cells. These results suggest that sorafenib inhibits TGF-ß signalling mainly by inducing caveolae/lipid raft-mediated internalization and degradation of cell-surface TßR-II in target cells. They may also imply that treatment with agents which promote formation of caveolae/lipid rafts, TGF-ß receptor kinase inhibitors (e.g., LY2157299) or TGF-ß peptide antagonists (by liver-targeting delivery) may be considered as effective adjunct therapy with sorafenib for HCC.

Pentachloropseudilin Inhibits Transforming Growth Factor-ß (TGF-ß) Activity by Accelerating Cell-Surface Type†II TGF-ß Receptor Turnover in Target Cells.

Pentachloropseudilin (PClP) is a chlorinated phenylpyrrole compound that was first isolated from Actinoplanes (ATCC33002), and its structure has been confirmed by chemical synthesis. PClP shows broad antimicrobial activity against Gram-negative and Gram-positive bacteria, protozoa, fungi, and yeast. In mammalian cells, PClP is known to act as a reversible and allosteric inhibitor of myosin 1c (Myo1c). Herein, we report that PCIP is a potent inhibitor of transforming growth factor-ß (TGF-ß)-stimulated signaling. PCIP inhibits TGF-ß-stimulated Smad2/3 phosphorylation and plasminogen activator inhibitor-1 (PAI-1) promoter activation with an IC50 of 0.1 µm in target cells (A549, HepG2, and Mv1Lu cells). In addition, PCIP attenuates TGF-ß-stimulated expression of vimentin, N-cadherin, and fibronectin and, thus, blocks TGF-ß-induced epithelial to mesenchymal transition (EMT) in these cells. Furthermore, cell-surface labeling and immunoblot analysis indicates that PCIP suppresses TGF-ß-stimulated cellular responses by attenuating cell-surface expression of the type II TGF-ß receptor through accelerating caveolae-mediated internalization followed by primarily lysosome-dependent degradation of the receptor, as demonstrated by sucrose density gradient analysis and immune fluorescence staining.

Pentabromophenol suppresses TGF-ß signaling by accelerating degradation of type II TGF-ß receptors via caveolae-mediated endocytosis.

Pentabromophenol (PBP), a brominated flame retardant (BFR), is widely used in various consumer products. BFRs exert adverse health effects such as neurotoxic and endocrine-disrupting effects. In this study, we found that PBP suppressed TGF-ß response by accelerating the turnover rate of TGF-ß receptors. PBP suppressed TGF-ß-mediated cell migration, PAI-1 promoter-driven reporter gene activation, and Smad2/3 phosphorylation in various cell types. Furthermore, PBP abolished TGF-ß-mediated repression of E-cadherin expression, in addition to the induction of vimentin expression and N-cadherin and fibronectin upregulation, thus blocking TGF-ß-induced epithelial-mesenchymal transition in A549 and NMuMG cells. However, this inhibition was not observed with other congeners such as tribromophenol and triiodophenol. TGF-ß superfamily members play key roles in regulating various biological processes including cell proliferation and migration as well as cancer development and progression. The results of this in vitro study provide a basis for studies on the detailed relationship between PBP and modulation of TGF-ß signalling. Because PBP is similar to other BFRs such as polybrominated diphenyl ethers (PBDEs), additional laboratory and mechanistic studies should be performed to examine BFRs as potential risk factors for tumorigenesis and other TGF-ß-related diseases.