YC-1 [3-(5'-Hydroxymethyl-2'-furyl)-1-benzyl Indazole] exhibits a novel antiproliferative effect and arrests the cell cycle in G0-G1 in human hepatocellular carcinoma cells

Advances in antitumor research of HIF-1α inhibitor YC-1 and its derivatives

Generally, hypoxia-inducible factor-1α (HIF-1α) is highly expressed in solid tumors, it plays a key role in the occurrence and development of tumors, hindering cancer treatment in various ways. The antitumor activity and pharmacological mechanism of YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1‑benzyl indazole], an HIF-1α inhibitor, and the design and synthesis of its derivatives have attracted tremendous attention in the field of antitumor research. YC-1 is a potential drug candidate and a lead compound for tumor therapy. Hence, the multifaceted mechanism of action of YC-1 and the structure activity relationship (SAR) of its derivatives are important factors to be considered for the development of HIF-1α inhibitors. Therefore, this review aimed to provide a comprehensive overview of the various antitumor mechanisms of YC-1 in antitumor research and an in-depth summary of the SAR for the development of its derivatives. A full understanding and discussion of these aspects are expected to provide potential ideas for developing novel HIF-1α inhibitors and antitumor drugs belonging to the YC-1 class. The review also highlighted the application prospects of the YC-1 class of potential antitumor candidates, and provided some unique insights about these antitumor agents.

Effect of phenylurea hydroxamic acids on histone deacetylase and VEGFR-2

A series of phenylurea hydroxamic acids incorporating pharmacophores of inhibitors of HDAC inhibitors and VEGFR-2 has been designed. Most of the compounds show antiproliferative activity comparable to that of Vorinostat and Sorafenib, and better EPC inhibitory activity. Enzymatic assays and Western blotting results indicated that compound 14 not only inhibits HDAC but also has slight VEGFR-2 inhibitory activity. A docking study revealed that the polar hydroxamic acid retains the interaction with HDAC through a zinc ion and also interacts with some residues of the active site of VEGFR-2. Despite 14 displaying a weaker VEGFR-2 activity, a possible route to develop potent HDAC/VEGFR-2 inhibitors is suggested.

Post-translational modifications of EZH2 in cancer

Enhancer of zeste homolog 2 (EZH2), as a main component of Polycomb Repressive Complex 2, catalyzes histone H3K27me3 to silence its target gene expression. EZH2 upregulation results in cancer development and poor prognosis of cancer patients. Post-translational modifications (PTMs) are important biological events in cancer progression. PTMs regulate protein conformation and diversity functions. Recently, mounting studies have demonstrated that EZH2 stability, histone methyltransferase activity, localization, and binding partners can be regulated by PTMs, including phosphorylation, O-GlcNAcylation, acetylation, methylation and ubiquitination. However, the detailed molecular mechanisms of the EZH2-PTMs and whether other types of PTMs occur in EZH2 remain largely unclear. This review presents an overview of different roles of EZH2 modification and EZH2-PTMs crosstalk during tumorigenesis and cancer metastasis. We also discussed the therapeutic potential of targeting EZH2 modifications for cancer therapy.

Squalene deters drivers of RCC disease progression beyond VHL status

Identifying drug candidates to target cellular events/signaling that evades von Hippel-Lindau tumor suppressor (VHL) gene interaction is critical for the cure of renal cell carcinoma (RCC). Recently, we characterized a triterpene-squalene derived from marine brown alga. Herein, we investigated the potential of squalene in targeting HIF-signaling and other drivers of RCC progression. Squalene inhibited cell proliferation, induced cell dealth and reverted the cells' metastatic state (migration, clonal expansion) independent of their VHL status. Near-identical inhibition of HIF-1α and HIF-2α and the regulation of downstream targets in VHL wild type and mutant cell lines demonstrated squalene efficacy beyond VHL-HIF interaction. In a rat model of chemically induced RCC, squalene displayed chemopreventive capabilities by substantial reversal of lipid peroxidation, mitochondrial redox regulation, maintaining ∆ψ_m, inflammation [Akt, nuclear factor κB (NF-κB)], angiogenesis (VEGFα), metastasis [matrix metalloproteinase 2 (MMP-2)], and survival (Bax/Bcl2, cytochrome-c, Casp3). Squalene restored glutathione, glutathione reductase, glutathione-s-transferase, catalase, and superoxide dismutase and stabilized alkaline phosphatase, alkaline transaminase, and aspartate transaminase. The correlation of thiobarbituric acid reactive substance with VEGF/NF-κB and negative association of GSH with Casp3 show that squalene employs reduction in ROS regulation. Cytokinesis-block micronuclei (CBMN) assay in VHL^wt/mut cells revealed both direct and bystander effects of squalene with increased micronucleus (MN) frequency. Clastogenicity analysis of rat bone marrow cells demonstrated an anti-clastogenic effect of squalene, with increased polychromatic erythrocytes (PCEs), decreased MNPCE,s and MN normochromatic erythrocytes. Squalene could effectively target HIF signaling that orchestrate RCC evolution. The efficacy of squalene is similar in VHL^wt and VHL^mut RCC cells, and hence, squalene could serve as a promising drug candidate for an RCC cure beyond VHL status and VHL-HIF interaction dependency. Summary: Squalene derived from marine brown algae displays strong anti-cancer (RCC) activity, functionally targeting HIF-signaling pathway, and affects various cellular process. The significance of squalene effect for RCC is highlighted by its efficiency beyond VHL status, designating itself a promising drug candidate. Graphical abstract.

YC-1 Antagonizes Wnt/β-Catenin Signaling Through the EBP1 p42 Isoform in Hepatocellular Carcinoma

Novel drugs targeting Wnt signaling are gradually being developed for hepatocellular carcinoma (HCC) treatment. In this study, we used a Wnt-responsive Super-TOPflash (STF) luciferase reporter assay to screen a new compound targeting Wnt signaling. 3-(5'-Hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) was identified as a small molecule inhibitor of the Wnt/β-catenin pathway. Our coimmunoprecipitation (co-IP) data showed that YC-1 did not affect the β-catenin/TCF interaction. Then, by mass spectrometry, we identified the ErbB3 receptor-binding protein 1 (EBP1) interaction with the β-catenin/TCF complex upon YC-1 treatment. EBP1 encodes two splice isoforms, p42 and p48. We further demonstrated that YC-1 enhances p42 isoform binding to the β-catenin/TCF complex and reduces the transcriptional activity of the complex. The suppression of colony formation by YC-1 was significantly reversed after knockdown of both isoforms (p48 and p42); however, the inhibition of colony formation was maintained when only EBP1 p48 was silenced. Taken together, these results suggest that YC-1 treatment results in a reduction in Wnt-regulated transcription through EBP1 p42 and leads to the inhibition of tumor cell proliferation. These data imply that YC-1 is a drug that antagonizes Wnt/β-catenin signaling in HCC.

Updates on the hepatocyte growth factor/c-Met axis in hepatocellular carcinoma and its therapeutic implications

Hepatocellular carcinoma (HCC) is the fifth most common cancer and is the second leading cause of cancer death. Since the diagnosis of HCC is difficult, in many cases patients with HCC are diagnosed advanced stage of development. Hepatocyte growth factor (HGF)/c-mesenchymal-epithelial transition receptor (c-Met) axis is a key signaling pathway in HCC, either via canonical or non-canonical pathways. Available treatments against HCC based upon HGF/c-Met inhibition can increase patient lifespan, but do not reach the expected therapeutic benefits. In HCC, c-Met monomers can bind other receptor monomers, activating several noncanonical signaling pathways, leading to increased cell proliferation, invasion, motility, and drug resistance. All of these processes are enhanced by the tumor microenvironment, with stromal cells contributing to boost tumor progression through oxidative stress, angiogenesis, lymphangiogenesis, inflammation, and fibrosis. Novel treatments against HCC are being explored to modulate other targets such as microRNAs, methyltransferases, and acetyltransferases, which are all involved in the regulation of gene expression in cancer. This review compiles basic knowledge regarding signaling pathways in HCC, and compounds already used or showing potential to be used in clinical trials.

ATPase inhibitory factor 1 inhibition improves the antitumor of YC-1 against hepatocellular carcinoma

YC-1 is a synthetic compound, which serves as a hypoxia-inducible factor 1-α inhibitor or sensitizer to enhance the effect of chemotherapy. Previous studies have revealed the anti-cancer effects of YC-1 in various types of cancer, including hepatocellular carcinoma (HCC). ATPase inhibitory factor 1 (IF1) is upregulated in a number of human carcinomas and regulates mitochondrial bioenergetics and structure. However, whether IF1 is involved in the antitumor effects of YC-1 against HCC remains unclear. The present study examined the function of IF1 in HCC and its potential role in YC-1 effects within HCC cells. MTT, colony formation and Transwell assays revealed that IF1 overexpression promoted proliferation, colony formation and invasion of HCC cells, while IF1 downregulation had the opposite effects. Overexpression of IF1 reversed the inhibitory effects of YC-1 on Huh7 cell growth and invasion activities, while downregulation of IF1 increased the sensitivity of HCCLM3 cells to YC-1. YC-1 treatment of HCCLM3 and Huh7 cells reduced the levels of phosphorylated (p-) signal transducer and activator of transcription 3 (STAT3) and IF1, and increased the expression of E-cadherin. IF1 knockdown resulted in decreased p-STAT3 levels and increased E-cadherin expression, while IF1 overexpression increased p-STAT3 levels and reduced the expression of E-cadherin. The present study demonstrated that the inhibition of IF1 improves the antitumor effects of YC-1 in HCC cells. These findings support the clinical strategy of combining YC-1 and an IF1 inhibitor for the treatment of HCC.

YC-1 induces G0/G1 phase arrest and mitochondria-dependent apoptosis in cisplatin-resistant human oral cancer CAR cells

Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G₀/G₁ phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G₀/G₁ phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

A 4-Phenoxyphenol Derivative Exerts Inhibitory Effects on Human Hepatocellular Carcinoma Cells through Regulating Autophagy and Apoptosis Accompanied by Downregulating α-Tubulin Expression

Hepatocellular carcinoma (HCC) is a leading cancer worldwide. Advanced HCCs are usually resistant to anticancer drugs, causing unsatisfactory chemotherapy outcomes. In this study, we showed that a 4-phenoxyphenol derivative, 4-[4-(4-hydroxyphenoxy)phenoxy]phenol (4-HPPP), exerts an inhibitory activity against two HCC cell lines, Huh7 and Ha22T. We further investigated the anti-HCC activities of 4-HPPP, including anti-proliferation and induction of apoptosis. Our results showed that higher dosage of 4-HPPP downregulates the expression of α-tubulin and causes nuclear enlargement in both the Huh-7 and Ha22T cell lines. Interestingly, the colony formation results showed a discrepancy in the inhibitory effect of 4-HPPP on HCC and rat liver epithelial Clone 9 cells, suggesting the selective cytotoxicity of 4-HPPP toward HCC cells. Furthermore, the cell proliferation and apoptosis assay results illustrated the differences between the two HCC cell lines. The results of cellular proliferation assays, including trypan blue exclusion and colony formation, revealed that 4-HPPP inhibits the growth of Huh7 cells, but exerts less cytotoxicity in Ha22T cells. Furthermore, the annexin V assay performed for detecting the apoptosis showed similar results. Western blotting results showed 4-HPPP caused the increase of pro-apoptotic factors including cleaved caspase-3, Bid and Bax in HCC cells, especially in Huh-7. Furthermore, an increase of autophagy-associated protein microtubule-associated protein-1 light chain-3B (LC3B)-II and the decrease of Beclin-1 and p62/SQSTM1 were observed following 4-HPPP treatment. Additionally, the level of γH2A histone family, member X (γH₂AX), an endogenous DNA damage biomarker, was dramatically increased in Huh7 cells after 4-HPPP treatment, suggesting the involvement of DNA damage pathway in 4-HPPP-induced apoptosis. On the contrary, the western blotting results showed that treatment up-regulates pro-survival proteins, including the phosphorylation of protein kinase B (Akt) and the level of survivin on Ha22T cells, which may confer a resistance toward 4-HPPP. Notably, the blockade of extracellular signal-regulated kinases (ERK), but not Akt, enhanced the cytotoxicity of 4-HPPP against Ha22T cells, indicating the pro-survival role of ERK in 4-HPPP-induced anti-HCC effect. Our present work suggests that selective anti-HCC activity of 4-HPPP acts through induction of DNA damage. Accordingly, the combination of ERK inhibitor may significantly enhance the anti-cancer effect of 4-HPPP for those HCC cells which overexpress ERK in the future.

Synthesis and biological evaluation of novel 3,9-substituted β-carboline derivatives as anticancer agents

In our previous studies on 1-benzyl-3-(5-hydroxymethyl-2-furyl)indazole (YC-1) analogs, we synthesised numerous substituted carbazole and α-carboline derivatives, which exhibited anticancer activity. In this study, we designed and synthesised a series of 3,9-substituted β-carbolines, by replacing the tricyclic rings of carbazole and α-carboline derivatives with isosteric β-carboline, and evaluated anticancer activity. We observed that 9-(2-methoxybenzyl)-β-carboline-3-carboxylic acid (11a) inhibited the growth of HL-60 cells by inducing apoptosis, with a half maximal inhibitory concentration of 4.0 μM. Our findings indicate that β-carboline derivatives can be used as lead compounds for developing novel antitumor agents.

YC-1 enhances the anti-tumor activity of sorafenib through inhibition of signal transducer and activator of transcription 3 (STAT3) in hepatocellular carcinoma

Background

Traditional systemic chemotherapy does not provide survival benefits in patients with hepatocellular carcinoma (HCC). Molecular targeted therapy shows promise for HCC treatment, however, the duration of effectiveness for targeted therapies is finite and combination therapies offer the potential for improved effectiveness.

Methods

Sorafenib, a multikinase inhibitor, and YC-1, a soluble guanylyl cyclase (sGC) activator, were tested in HCC by proliferation assay, cell cycle analysis and western blot in vitro and orthotopic and ectopic HCC models in vivo.

Results

In vitro, combination of sorafenib and YC-1 synergistically inhibited proliferation and colony formation of HepG2, BEL-7402 and HCCLM3 cells. The combination also induced S cell cycle arrest and apoptosis, as observed by activated PARP and caspase 8. Sorafenib and YC-1 respectively suppressed the expression of phosphorylated STAT3 (p-STAT3) (Y705) in a dose- and time-dependent manner. Combination of sorafenib and YC-1 significantly inhibited the expression of p-STAT3 (Y705) (S727), p-ERK1/2, cyclin D1 and survivin and SHP-1 activity compared with sorafenib or YC-1 used alone in all tested HCC cell lines. In vivo, sorafenib-YC-1 combination significantly suppressed the growth of HepG2 tumor xenografts with decreased cell proliferation and increased apoptosis observed by PCNA and PARP. Similar results were also confirmed in a HCCLM3 orthotopic model. There was a reduction in CD31-positive blood vessels and reduced VEGF expression, which suggested a combinational effect of sorafenib and YC-1 on angiogenesis. The reduced expression of p-STAT3, cyclin D1 and survivin was also observed with the combination of sorafenib and YC-1.

Conclusions

Our data show that sorafenib-YC-1 combination is a novel potent therapeutic agent that can target the STAT3 signaling pathway to inhibit HCC tumor growth.

CLC604 preferentially inhibits the growth of HER2-overexpressing cancer cells and sensitizes these cells to the inhibitory effect of Taxol in vitro and in vivo

HER2 has become a solicitous therapeutic target in metastatic and clinical drug-resistant cancer. Here, we evaluated whether or not 1-benzyl-3-(5-hydroxymethyl-2-furyl)indazole (YC-1) and its furopyrazole and thienopyrazole analogues repress the expression of the HER2 protein. Among the test compounds, (1-benzyl-3-(p-hydroxymethylphenyl)-5-methylfuro[3,2-c]pyrazol) (CLC604), an isosteric analogue of YC-1, significantly suppressed the expression of HER2, and preferentially inhibited cell proliferation and induced apoptosis in HER2-overexpressing cancer cells. Our results revealed that CLC604 reduced HER2 expression through a post-transcriptional mechanism and involvement of proteasomal activity. CLC604 disrupted the association of 90-kDa heat shock protein (Hsp90) with HER2 resulting from the inhibition of Hsp90 ATPase activity. Moreover, we found that CLC604 significantly enhanced the antitumor efficacy of clinical drugs against HER2-overexpressing tumors and efficiently reduced HER2-induced drug resistance in vitro and in vivo. These findings suggest that CLC604 should be developed further as a novel antitumor drug candidate for the treatment of drug-resistant cancer.

YC-1 exerts inhibitory effects on MDA-MB-468 breast cancer cells by targeting EGFR in vitro and in vivo under normoxic condition

3-(5′-hydroxymethyl-2′-furyl)-1-benzyl indazole (YC-1), the hypoxia-inducible factor-1 alpha (HIF-1α) inhibitor, suppresses tumor proliferation and metastasis by down-regulating HIF-1α expression under hypoxic conditions. Our previous studies demonstrated that YC-1 inhibited breast cancer cell proliferation under normoxic conditions. In the current study, we investigated the targets of YC-1 and mechanism of its action in MDA-MB-468 breast cancer cells. In the in vitro experiments, we found that YC-1 significantly inhibited MDA-MB-468 cell proliferation in normoxia and hypoxia. Under normoxic conditions, YC-1 induced apoptosis of MDA-MB-468 cells and blocked cell cycle in the G₁ phase, and these effects were possibly related to caspase 8, p21, and p27 expression. RT-PCR and Western blotting results showed that YC-1 primarily inhibited HIF-1α at the mRNA and protein levels under hypoxic conditions, but suppressed the expression of epidermal growth factor receptor (EGFR) at the mRNA and protein levels under normoxic conditions. In vivo, YC-1 prolonged survival, increased survival rate, decreased tumor size and metastasis rate, and inhibited tissue EGFR and HIF-1α expression. However, YC-1 exerted no obvious effect on body weight. These results indicate that YC-1 inhibits the proliferation of MDA-MB-468 cells by acting on multiple targets with minimal side effects. Thus, YC-1 is a promising target drug for breast cancer.

Guanylate cyclase activator YC-1 potentiates apoptotic effect of licochalcone A on human epithelial ovarian carcinoma cells via activation of death receptor and mitochondrial pathways

Natural phenol licorice compounds have been shown to induce apoptosis in cancer cells. 3-(5'-Hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) may enhance the sensitivity of cancer cells to anticancer drugs. However, the combined effect of licochalcone A and YC-1 on cell death in ovarian cancer cells has not been studied. We assessed the combined effect of licochalcone A and YC-1 on apoptosis in human epithelial ovarian carcinoma cell lines in relation to the cell death process. In the OVCAR-3 and SK-OV-3 cell lines, licochalocone A induced a decrease in Bid, Bcl-2, Bcl-xL and survivin protein levels; an increase in Bax levels; loss of the mitochondrial transmembrane potential; cytochrome c release; activation of caspases (-8, -9 and -3); cleavage of PARP-1; and an increase in the tumor suppressor p53 levels. YC-1 enhanced licochalcone A-induced apoptosis-related protein activation, nuclear damage and cell death. These results suggest that YC-1 may potentiate the apoptotic effect of licochalcone A on ovarian carcinoma cell lines by increasing the activation of the caspase-8- and Bid-dependent pathway and the mitochondria-mediated apoptotic pathway, leading to caspase activation. The combination of licochalcone A and YC-1 may confer a benefit in the treatment of human epithelial ovarian adenocarcinoma.

KMUP-1 inhibits H441 lung epithelial cell growth, migration and proinflammation via increased NO/CGMP and inhibited RHO kinase/VEGF signaling pathways

This study investigates whether KMUP-1 protects soluble guanylate cyclase (sGC) and inhibits vascular endothelial growth factor (VEGF) expression in lung epithelial cells in hypoxia, therapeutically targeting epithelial proinflammation. H441 cells were used as a representative epithelial cell line to examine the role of sGC and VEGF in hypoxia and the anti-proinflammatory activity of KMUP-1 in normoxia. Human H441 cells were grown in hypoxia for 24-72 h. KMUP-1 (1, 10, 100 microM) arrested cells at the G0/G1 phase of the cell cycle, reduced cell survival and migration, increased p21/p27, restored eNOS, increased soluble guanylate cyclase (sGC) and PKG and inhibited Rho kinase II (ROCK-II). KMUP-1 (0.001-0.1 microM) concentration dependently increased eNOS in normoxia and did not inhibit phosphodiesterase-5A (PDE-5A) in hypoxic cells. Hypoxia-induced factor-1alpha (HIF-1alpha) and VEGF were suppressed by KMUP-1 but not by L-NAME (100 microM). The PKG inhibitor Rp-8-CPT-cGMPS (10 microM) blunted the inhibition of ROCK-II by KMUP-1. KMUP-1 inhibited thromboxane A2-mimetic agonist U46619-induced PDE-5A, TNF-alpha (100 ng/ml)-induced iNOS, and ROCK-II and associated phospho-p38 MAPK, suggesting multiple anti-proinflammatory activities. In addition, increased p21/p27 by KMUP-1 at higher concentrations might contribute to an increased Bax/Bcl-2 and active caspase-3/procaspase-3 ratio, concomitantly causing apoptosis. KMUP-1 inhibited ROCK-II/VEGF in hypoxia, indicating its anti-neoplastic and anti-inflammatory properties. KMUP-1 inhibited TNF-alpha-induced iNOS and U46619-induced PDE-5A and phospho-p38 MAPK in normoxia, confirming its anti-proinflammatory action. KMUP-1 could be used as an anti-proinflammatory to reduce epithelial inflammation.

Restoring soluble guanylyl cyclase expression and function blocks the aggressive course of glioma

The NO and cGMP signaling pathways are of broad physiological and pathological significance. We compared the NO/soluble guanylyl cyclase (sGC)/cGMP pathway in human glioma tissues and cell lines with that of healthy control samples and demonstrated that sGC expression is significantly lower in glioma preparations. Our analysis of GEO databases (National Cancer Institute) further revealed a statistically significant reduction of sGC transcript levels in human glioma specimens. On the other hand, the expression levels of particulate (membrane) guanylyl cyclases (pGC) and cGMP-specific phosphodiesterase (PDE) were intact in the glioma cells that we have tested. Pharmacologically manipulating endogenous cGMP generation in glioma cells through either stimulating pGC by ANP/BNP, or blocking PDE by 3-isobutyl-1-methylxanthine/zaprinast caused significant inhibition of proliferation and colony formation of glioma cells. Genetically restoring sGC expression also correlated inversely with glioma cells growth. Orthotopic implantation of glioma cells transfected with an active mutant form of sGC (sGCα1β1(Cys105)) in athymic mice increased the survival time by 4-fold over the control. Histological analysis of xenografts overexpressing α1β1(Cys105) sGC revealed changes in cellular architecture that resemble the morphology of normal cells. In addition, a decrease in angiogenesis contributed to glioma inhibition by sGC/cGMP therapy. Our study proposes the new concept that suppressed expression of sGC, a key enzyme in the NO/cGMP pathway, may be associated with an aggressive course of glioma. The sGC/cGMP signaling-targeted therapy may be a favorable alternative to chemotherapy and radiotherapy for glioma and perhaps other tumors.

Cyclic GMP induced apoptosis via protein kinase G in oestrogen receptor-positive and -negative breast cancer cell lines

The activation of protein kinase G (PKG) by cyclic guanosine 3,5-monophosphate (cGMP) has become of considerable interest as a novel molecular approach for the induction of apoptosis in cancer cells. The present study was designed to examine the effects of cGMP and PKG on cell growth and apoptosis in the human breast cancer cell lines, MCF-7 and MDA-MB-468. To achieve this, 1-benzyl-3-(5P-hydroxymethyl-2P-furyl) indazole (YC-1), a soluble guanylyl cyclase activator, and 8-bromo-cGMP (8-br-cGMP), a membrane-permeant and phosphodiesterase-resistant analogue of cGMP, were employed in MCF-7 and MDA-MB-468 cells. Then, the role of PKG in the induction of apoptosis was evaluated using KT5823 and Rp-8-pCPT-cGMP as specific inhibitors of PKG. The expression of PKG isoforms in these cell lines was also investigated. KT5823 and Rp-8-pCPT-cGMP significantly attenuated the loss of cell viability caused by YC-1 and 8-br-cGMP in these cells. This study provides direct evidence that the activation of PKG by cGMP induces growth inhibition and apoptosis in MCF-7 and MDA-MB-468 breast cancer cell lines.

Essential roles of the nitric oxide (no)/cGMP/protein kinase G type-Iα (PKG-Iα) signaling pathway and the atrial natriuretic peptide (ANP)/cGMP/PKG-Iα autocrine loop in promoting proliferation and cell survival of OP9 bone marrow stromal cells

Inappropriate signaling conditions within bone marrow stromal cells (BMSCs) can lead to loss of BMSC survival, contributing to the loss of a proper micro-environmental niche for hematopoietic stem cells (HSCs), ultimately causing bone marrow failure. In the present study, we investigated the novel role of endogenous atrial natriuretic peptide (ANP) and the nitric oxide (NO)/cGMP/protein kinase G type-Iα (PKG-Iα) signaling pathway in regulating BMSC survival and proliferation, using the OP9 BMSC cell line commonly used for facilitating the differentiation of HSCs. Using an ANP-receptor blocker, endogenously produced ANP was found to promote cell proliferation and prevent apoptosis. NO donor SNAP (S-nitroso-N-acetylpenicillamine) at low concentrations (10 and 50 µM), which would moderately stimulate PKG activity, protected these BMSCs against spontaneous apoptosis. YC-1, a soluble guanylyl cyclase (sGC) activator, decreased the levels of apoptosis, similar to the cytoprotective effects of low-level NO. ODQ (1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one), which blocks endogenous NO-induced activation of sGC and thus lowers endogenous cGMP/PKG activity, significantly elevated apoptotic levels by 2.5- and three-fold. Pre-incubation with 8-Bromo-cGMP or ANP, which bypass the ODQ block, almost completely prevented the ODQ-induced apoptosis. A highly-specific PKG inhibitor, DT-3, at 20, and 30 µM, caused 1.5- and two-fold increases in apoptosis, respectively. ODQ and DT-3 also decreased BMSCs proliferation and colony formation. Small Interfering RNA gene knockdown of PKG-Iα increased apoptosis and decreased proliferation in BMSCs. The data suggest that basal NO/cGMP/PKG-Iα activity and autocrine ANP/cGMP/PKG-Iα are necessary for preserving OP9 cell survival and promoting cell proliferation and migration.

Guanylate cyclase activator YC-1 enhances TRAIL-induced apoptosis in human epithelial ovarian carcinoma cells via activation of apoptosis-related proteins

To assess the ability of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) to promote apoptosis, we investigated the effect of YC-1 on tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in the human epithelial ovarian carcinoma cell lines. In OVCAR-3 and SK-OV-3 cell lines, we examined the stimulatory effect of YC-1 on TRAIL-induced apoptosis by monitoring cell death, nuclear damage, changes in apoptosis-related protein levels, activation of caspases and changes in the mitochondrial transmembrane potential. TRAIL induced a decrease in Bid, Bcl-2 and Bcl-xL protein levels, increase in cleaved Bid and Bax levels, loss of the mitochondrial transmembrane potential, cytochrome c release, activation of caspases (-8, -9 and -3) and an increase in the tumour suppressor p53 levels. YC-1 enhanced TRAIL-induced apoptosis-related protein activation, nuclear damage and cell death. Results from this study suggest that YC-1 may enhance the apoptotic effect of TRAIL on ovarian carcinoma cell lines by increasing the activation of the caspase-8- and Bid-dependent pathways and the mitochondria-mediated apoptotic pathway, leading to caspase activation. YC-1 may confer a benefit in TRAIL treatment of epithelial ovarian adenocarcinoma.

Up-regulation of hypoxia-inducible factor-1 alpha by cobalt chloride prevents hearing loss in noise-exposed mice

Since hypoxia-inducible factor-1α (HIF-1α) is the key transcription factor that enables cells to survive in hypoxia, we have investigated whether an upregulation of HIF-1α prevents the noise-induced hearing loss in BALB/c hybrid mice, which were intraperitoneally injected with CoCl(2) (a HIF-1α inducer) and exposed to white band noise with 120 dB peak equivalent sound pressure level for 3h once daily for 3 days. In the CoCl(2) treatment group, HIF-1α was found to be up-regulated in the cochlear tissues and the hearing loss was largely prevented. Histologically, the loss of sensory hair cells was also significantly lower in the CoCl(2) treatment group than the Control group. However, YC-1 (a HIF-1α inhibitor) attenuated the preventive effect of CoCl(2) on the noise-induced hearing loss. These results suggest that HIF-1α plays a crucial role in the prevention against noise trauma in the inner ear.

Combined application of camptothecin and the guanylate cyclase activator YC-1: Impact on cell death and apoptosis-related proteins in ovarian carcinoma cell lines

Camptothecin analogs and guanylate cyclase activator YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole] have been shown to induce apoptosis in cancer cells. However, the combined effect of camptothecin analogs and YC-1 on the viability of epithelial ovarian cancer cells remains uncertain. We assessed the combined effect of YC-1 on the camptothecin toxicity in the human epithelial ovarian carcinoma cell lines OVCAR-3 and SK-OV-3. Camptothecin and YC-1 induced apoptosis in OVCAR-3 and SK-OV-3 cells in a dose- and time-dependent manner. Both compounds induced nuclear damage, decreased Bid and Bcl-2 protein levels, enhanced cytochrome c release, activated caspase-3 and upregulated tumor suppressor p53. Camptothecin decreased Bax protein levels, whereas YC-1 increased Bax levels. YC-1 enhanced the camptothecin-induced changes in the apoptotic protein levels and increased apoptotic effect of camptothecin on ovarian carcinoma cell lines. The results suggested that YC-1 may enhance a camptothecin toxicity against ovarian carcinoma cell lines by increasing activation of the caspase-8 and Bid pathway as well as activation of the mitochondria-mediated apoptotic pathway, leading to cytochrome c release and subsequent caspase-3 activation. Combination of camptothecin analogs and YC-1 may provide a therapeutic benefit against ovarian adenocarcinoma.

NO-independent, haem-dependent soluble guanylate cyclase stimulators

The nitric oxide (NO) signalling pathway is altered in cardiovascular diseases, including systemic and pulmonary hypertension, stroke, and atherosclerosis. The vasodilatory properties of NO have been exploited for over a century in cardiovascular disease, but NO donor drugs and inhaled NO are associated with significant shortcomings, including resistance to NO in some disease states, the development of tolerance during long-term treatment, and non-specific effects such as post-translational modification of proteins. The development of pharmacological agents capable of directly stimulating the NO receptor, soluble guanylate cyclase (sGC), is therefore highly desirable. The benzylindazole compound YC-1 was the first sGC stimulator to be identified; this compound formed a lead structure for the development of optimized sGC stimulators with improved potency and specificity for sGC, including CFM-1571, BAY 41-2272, BAY 41-8543, and BAY 63-2521. In contrast to the NO- and haem-independent sGC activators such as BAY 58-2667, these compounds stimulate sGC activity independent of NO and also act in synergy with NO to produce anti-aggregatory, anti-proliferative, and vasodilatory effects. Recently, aryl-acrylamide compounds were identified independent of YC-1 as sGC stimulators; although structurally dissimilar to YC-1, they have a similar mode of action and promote smooth muscle relaxation. Pharmacological stimulators of sGC may be beneficial in the treatment of a range of diseases, including systemic and pulmonary hypertension, heart failure, atherosclerosis, erectile dysfunction, and renal fibrosis. An sGC stimulator, BAY 63-2521, is currently in clinical development as an oral therapy for patients with pulmonary hypertension. It has demonstrated efficacy in a proof-of-concept study, reducing pulmonary vascular resistance and increasing cardiac output from baseline. A full, phase 2 trial of BAY 63-2521 in pulmonary hypertension is underway.

YC-1 induces heat shock protein 70 expression and prevents oxidized LDL-mediated apoptosis in vascular smooth muscle cells

Heat shock protein 70 (hsp70) functioning as molecular chaperon in physiological conditions is induced under stress environment, which affords a defensive mechanism for cells to escape cellular damage. Hence, it is a critical issue to develop a nontoxic hsp70-inducing compound against cellular death. The present study was conducted to evaluate whether 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl-indazol (YC-1) can effectively induce hsp70 expression and protect vascular smooth muscle cells (VSMCs) against oxidized low-density lipoprotein-induced cytotoxicity. We showed that YC-1 enhanced hsp70 expression in VSMCs through a concentration- and time-dependent manner with maximum expression at 18 and 24 h without involving the cyclic guanosine monophosphate and reactive oxygen species signal in the pathway. Furthermore, we did not observe significant cytotoxicity after YC-1 treatment through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, lactic dehydrogenase, and fluorescence activating cell sorting scan assays. We demonstrated that the nuclear level of heat shock transcription factor 1 increased at 2 h after YC-1 treatment, and hsp70 expression was directed by the up-regulation of hsp70 mRNA, which peaked at 6 h and was followed by a decline. Hence, translocation of heat shock transcription factor 1 and increased level of hsp70 mRNA would account for Hsp70 expression. Finally, we found that YC-1 protects VSMCs from oxidized low-density lipoprotein-inducing apoptosis. According to our observations, YC-1 would be an effectively pharmacological hsp70 inducer that can be used as a cytoprotective agent in vascular diseases.

Molecular composition, activation mechanism of hypoxia-inducible factor-1 and targeted therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumor in the world, with a complex process involving multi-center, multi-cause and multi-genes. Surgical resection is still the main treatment. However, the diagnosis of HCC mostly occurs at middle or advanced stage, and the prognosis is very poor. Therefore, the development of a novel molecular marker for early diagnosis and a new target for gene therapy become hot spots. Hypoxia-inducible factor-1 (HIF-1) takes part in the development, metastasis and recurrence of HCC, and it has potential applications in the early diagnosis and molecular targeted therapy of HCC. We presented a review on molecular composition, activation mechanism of HIF-1, and the targeted therapeutic approaches applied to hepatocellular carcinoma.

YC-1 induces apoptosis of human renal carcinoma A498 cells in vitro and in vivo through activation of the JNK pathway

BACKGROUND AND PURPOSE

The aim of this study was to elucidate the mechanism of YC-1{3-(5'-hydroxy methyl-2'-furyl)-1-benzylindazole}-induced human renal carcinoma cells apoptosis and to evaluate the potency of YC-1 in models of tumour growth in mice.

EXPERIMENTAL APPROACH

YC-1-mediated apoptosis was assessed by analysis of MTT, SRB, DAPI staining and flow cytometry analysis. Knockdown of JNK protein was achieved by transient transfection using siRNA. The mechanisms of action of YC-1 on different signalling pathways involved were studied using western blot. Fas clustering was analysed by confocal microscopy and in vivo efficacy was examined in a A498 xenograft model.

KEY RESULTS

YC-1 displayed cytotoxicity in renal carcinoma cells at 10(-7)-10(-8) M. Increased condensation of chromatin was observed and an increase in the cell population in subG1 phase. Moreover, YC-1 triggered mitochondria-mediated and caspase-dependent pathways. YC-1 significantly induced Fas ligand expression, but did not modify either the protein levels of death receptors or ligands. In addition, Fas clustering in cells responsive to YC-1 was observed, suggesting involvement of a Fas-mediated pathway. Furthermore, YC-1 markedly induced phosphorylation of JNK and a JNK inhibitor, SP600125, and siRNA JNK1/2 significantly reversed YC-1-induced cytotoxicity and protein expression. We suggest that YC-1 induced JNK phosphorylation, the upregulation of FasL and Fas receptor clustering to promote the activation of caspases 8 and 3, resulting in apoptosis. Finally, we demonstrated the antitumour effect of YC-1 in vivo.

CONCLUSIONS AND IMPLICATIONS

These data suggest that YC-1 is a good candidate for development as an anticancer drug.

CHM-1, a novel synthetic quinolone with potent and selective antimitotic antitumor activity against human hepatocellular carcinoma in vitro and in vivo

Hepatocellular carcinoma is highly chemoresistant to currently available chemotherapeutic agents. In this study, 2'-fluoro-6,7-methylenedioxy-2-phenyl-4-quinolone (CHM-1), a synthetic 6,7-substituted 2-phenyl-4-quinolone, was identified as a potent and selective antitumor agent in human hepatocellular carcinoma. CHM-1 induced growth inhibition of HA22T, Hep3B, and HepG2 cells in a concentration-dependent manner but did not obviously impair the viability of normal cells at the IC(50) for liver cancer cells. CHM-1-induced apoptosis was also characterized by immunofluorescence microscopy. CHM-1 interacted with tubulin at the colchicine-binding site, markedly inhibited tubulin polymerization both in vitro and in vivo, and disrupted microtubule organization. CHM-1 caused cell cycle arrest at G(2)-M phase by activating Cdc2/cyclin B1 complex activity. CHM-1-induced cell death, activation of Cdc2 kinase activity, and elevation of MPM2 phosphoepitopes were profoundly attenuated by roscovitine, a specific cyclin-dependent kinase inhibitor. CHM-1 did not modulate the caspase cascade, and the pan-caspase-inhibitor z-VAD-fmk did not abolish CHM-1-induced cell death. However, CHM-1 induced the translocation of apoptosis-inducing factor (AIF) from mitochondria to the nucleus. Small interfering RNA targeting of AIF substantially attenuated CHM-1-induced AIF translocation. Importantly, CHM-1 inhibited tumor growth and prolonged the lifespan in mice inoculated with HA22T cells. In conclusion, we show that CHM-1 exhibits a novel antimitotic antitumor activity against human hepatocellular carcinoma both in vitro and in vivo via a caspase-independent pathway. CHM-1 is a promising chemotherapeutic agent worthy of further development into a clinical trial candidate for treating cancer, especially hepatocellular carcinoma.

CHM-1 inhibits hepatocyte growth factor-induced invasion of SK-Hep-1 human hepatocellular carcinoma cells by suppressing matrix metalloproteinase-9 expression

Clinical observations suggest that hepatocyte growth factor (HGF) can promote invasion and metastasis in hepatocellular carcinoma. In this study, we found that HGF-stimulated invasion of SK-Hep-1 cells, together with increased expression of matrix metalloproteinase (MMP)-9. CHM-1 was identified from 2-phenyl-4-quinolone derivatives to potently inhibit HGF-induced cell invasion, proteolytic activity, and expression of MMP-9. CHM-1 significantly inhibited tyrosine autophosphorylation of c-Met induced by HGF. CHM-1 also suppressed HGF-induced Akt phosphorylation, and NF-kappaB activation, the downstream regulators of HGF/c-Met signaling, resulting in the inhibition of MMP-9. Thus, we suggest that CHM-1 is a potential therapeutic agent against tumor invasion.

Proteomic approach to studying the cytotoxicity of YC-1 on U937 leukemia cells and antileukemia activity in orthotopic model of leukemia mice

To evaluate the effects of YC-1 on leukemia cell lines, PI incorporation was used to determine cell viability. YC-1 induced a dose- and time-dependent decrease in viability and apoptosis in YC-1-treated U937 cells. YC-1-induced apoptosis is a cyclic guanosine monophosphate (cGMP)-independent pathway. Proteomic analysis showed that the altered proteins include the significant regulation of HSP70, chaperonin, ATP synthase beta chains, and Chain F. Western blotting and immuno-cytochemistry stain showed that YC-1 treatment caused a time-dependent increase in cytosolic Cytochrome c, pro-caspase-9, Apaf-1, and the activation of caspase-9 and -3. Importantly, the in vivo antileukemia effects of YC-1 were evaluated in BALB/c mice inoculated with WEHI-3B orthotopic model. YC-1 enhanced survival rate and prevented the body weight loss in leukemia mice. The enlargement of spleen and lymph nodes were reduced in YC-1 treated than that in leukemia mice. H-E stain of spleen sections revealed that infiltration of immature myeloblastic cells into red pulp was reduced in YC-1-treated group. The apoptotic cells of splenocyte were significantly increased in YC-1 treated than that in leukemia mice by Tdt-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay. Taken together, we conclude that YC-1 acted against U937 cells in vitro via a mitochondrial-dependent apoptosis pathway, and in orthotopic leukemia model, YC-1 administered antileukemia activity.

Anticancer mechanisms of YC-1 in human lung cancer cell line, NCI-H226

As part of a continuing search for potential anticancer drug candidates, 1-benzyl-3-(5-hydroxymethyl-2-furyl)indazole (YC-1) was evaluated in the Japanese Cancer Institute's (JCI) in vitro disease-oriented anticancer screen. The results indicated that YC-1 showed impressive selective toxicity against the NCI-H226 cell line. Therefore, the molecular mechanism by which YC-1 affects NCI-H226 cell growth was studied. YC-1 inhibited NCI-H226 cell growth in a time- and a concentration-dependent manner. YC-1 suppressed the protein levels of cyclin D1, CDK2 and cdc25A, up-regulated p16, p21 and p53, increased the number of NCI-H226 cells in the G0/G1 phase of the cell cycle. Long exposure to YC-1 induced apoptosis by mitochondrial-dependent pathway. In addition, YC-1 inhibited MMP-2 and MMP-9 protein activities to abolish tumor cells metastasis. These findings suggest a mechanism of cytotoxic action of YC-1 and indicate that YC-1 may be a promising chemotherapy agent against lung cancer.

Enhancement of docetaxel efficacy in head and neck cancer treatment by G0 cell stimulation

OBJECTIVES

Docetaxel has recently taken part in new chemotherapy regimens with promising activity especially in the first line therapy (induction chemotherapy) of head and neck cancer (SCCHN). Nevertheless a major problem concerning the response of SCCHN to chemotherapy is the high percentage of resting cells (G0-phase cells) being resistant to chemotherapy. To overcome this phenomenon we have investigated the capacity of several cytokines to switch on cells into division cycle and progress to the chemosensitive phases (S, M-phase).

METHODS

Il-6, Serotonin, G-CSF and EGF were used to stimulate G0-phase squamous cell cancer cells (Detroit 562, A431, UM-SCC 10B) for reentry in the cell cycle to enhance the response to docetaxel. The proportion of G0-phase cells was detected through multicolor FACS analysis and Ki67 staining.

RESULTS

Cell cycle reentering was most effective after combination treatment with Serotonin+EGF. The proportion of G0 phase cells was significantly reduced after stimulation with Serotonin+EGF (p<0.05). Corresponding to cell cycle reentry the cytotoxic effect of docetaxel was significantly (p<0.04) enhanced in the prestimulated cells compared to the control (docetaxel monotreatment).

CONCLUSIONS

Our investigations demonstrate for the first time that sensitizing G0 phase squamous cell carcinoma cells for docetaxel treatment is possible by prestimulation with target cytokines. Considering that up to 95% of tumor cells are in the resting (G0) phase of the cell cycle at the initiation of chemotherapy, prestimulation with EGF and serotonin could contribute to a synchronization of cancer cells. This would clearly enhance the cytotoxic effect.

YC-1 attenuates LPS-induced proinflammatory responses and activation of nuclear factor-kappaB in microglia

BACKGROUND AND PURPOSE

An inflammatory response in the central nervous system mediated by the activation of microglia is a key event in the early stages of the development of neurodegenerative diseases. LPS has been reported to cause marked microglia activation. It is very important to develop drugs that can inhibit microglia activation and neuroinflammation. Here, we investigated the inhibitory effect of YC-1, a known activator of soluble guanylyl cyclase, against LPS-induced inflammatory responses in microglia.

EXPERIMENTAL APPROACH

To understand the inhibitory effects of YC-1 on LPS-induced neuroinflammation, primary cultures of rat microglia and the microglia cell line BV-2 were used. To examine the mechanism of action of YC-1, LPS-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production, iNOS, COX-2 and cytokine expression were analyzed by Griess reaction, ELISA, Western blotting and RT-PCR, respectively. The effect of YC-1 on LPS-induced activation of nuclear factor kappa B (NF-kappaB) was studied by NF-kappaB reporter assay and immunofluorocytochemistry.

KEY RESULTS

YC-1 inhibited LPS-induced production of NO and PGE2 in a concentration-dependent manner. The protein and mRNA expression of iNOS and COX-2 in response to LPS application were also decreased by YC-1. In addition, YC-1 effectively reduced LPS-induced expression of the mRNA for the proinflammatory cytokines, TNF-alpha and IL-1beta. Furthermore, YC-1 inhibited LPS-induced NF-kappaB activation in microglia.

CONCLUSIONS AND IMPLICATIONS

YC-1 was able to inhibit LPS-induced iNOS and COX-2 expression and NF-kappaB activation, indicating that YC-1 may be developed as an anti-inflammatory neuroprotective agent.

2-(3-Fluorophenyl)-6-methoxyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (YJC-1) induces mitotic phase arrest in A549 cells

A 2-phenyl-4-quinolone (2-PQ) derivative, 2-(3-fluorophenyl)-6-methoxyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (YJC-1), was synthesized in our laboratory. In this study, we delineated the growth-inhibitory effect of YJC-1 in human lung carcinoma A549 cells. YJC-1 inhibited cell growth with an IC(50) value of about 4.8 microM via microtubule polymerization, causing growth arrest in the mitotic phase. Immunoblotting analysis revealed a dramatic induction of cyclin-dependent kinase (CDK) inhibitor p21(Cip1/Waf1) and down-regulation of Cdc25C phosphatase to inhibit the protein expression of cyclin B1 and CDK1. We also found that YJC-1 induced a profound time-dependent elevation in p21(Cip1/Waf1) gene expression in comparison with the negative control. In vivo, we also found that YJC-1 significantly suppressed tumor growth in mice inoculated with A549 cells. These findings suggest that YJC-1 can suppress A549 cell growth via mitotic phase arrest.

Synthesis of furopyrazole analogs of 1-benzyl-3-(5-hydroxymethyl-2-furyl)indazole (YC-1) as novel anti-leukemia agents

As part of our continuing search for potential anticancer drug candidates in YC-1 analogs, several 1-benzyl-3-(substituted aryl)-5-methylfuro[3,2-c]pyrazoles were synthesized and evaluated for their cytotoxicity against HL-60 cell line. Among these compounds, 1-benzyl-3-(5-hydroxymethyl-2-furyl)-5-methylfuro[3,2-c]pyrazole (1) showed more potency than YC-1. Through investigation of action mechanism, it was found that compound 1 induced terminal differentiation of HL-60 cells toward granulocyte lineage and promoted HL-60 cell differentiation by regulation of Bcl-2 and c-Myc proteins. Meanwhile, compound 1 also demonstrated apoptosis inducing effect. Such anti-leukemia mechanism of action is apparently different from that of YC-1 which mainly works by inducing apoptosis, but not cell differentiation. Therefore, compound 1 is identified here as a new lead compound of cell differentiating agent and apoptosis inducer for further development of new anti-leukemia agents.

Suppression of hypoxia inducible factor-1alpha (HIF-1alpha) by YC-1 is dependent on murine double minute 2 (Mdm2)

Inhibition of HIF-1alpha activity provides an important strategy for the treatment of cancer. Recently, 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) has been identified as an anti-HIF-1alpha drug in cancer therapy with unclear molecular mechanism. In the present study, we aimed to investigate the effect and mechanism of YC-1 on HIF-1alpha in a hepatocellular carcinoma cell line under hypoxic condition, which was generated by incubating cells with 0.1% O(2). The phenotypic and molecular changes of cells were determined by cell proliferation assay, apoptosis assay, luciferase promoter assay, and Western blot analysis. YC-1 arrested tumor cell growth in a dose-dependent manner, whereas it did not induce cell apoptosis. Hypoxia-induced upregulation of HIF-1alpha was suppressed by YC-1 administration. YC-1 inhibited HIF-1alpha protein synthesis under normoxia and affected protein stability under hypoxia. YC-1 suppressed the expression of total and phosphorylated forms of murine double minute 2 (Mdm2), whereas this inhibitory effect was blocked by overexpression of Mdm2. In conclusion, YC-1 suppressed both protein synthesis and stability of HIF-1alpha in HCC cells, and its inhibitory effects on HIF-1alpha were dependent on Mdm2.

YC-1 Induces S Cell Cycle Arrest and Apoptosis by Activating Checkpoint Kinases

Hypoxia-inducible factor-1alpha (HIF-1alpha) seems central to tumor growth and progression because it up-regulates genes essential for angiogenesis and the hypoxic adaptation of cancer cells, which is why HIF-1alpha inhibition is viewed as a cancer therapy strategy. Paradoxically, HIF-1alpha also leads to cell cycle arrest or the apoptosis of cancer cells. Thus, the possibility cannot be ruled out that HIF-1alpha inhibitors unlock cell cycle arrest under hypoxic conditions and prevent cell death, which would limit the anticancer effect of HIF-1alpha inhibitors. Previously, we reported on the development of YC-1 as an anticancer agent that inhibits HIF-1alpha. In the present study, we evaluated the effects of YC-1 on hypoxia-induced cell cycle arrest and cell death. It was found that YC-1 does not reverse the antiproliferative effect of hypoxia, but rather that it induces S-phase arrest and apoptosis at therapeutic concentrations that inhibit HIF-1alpha and tumor growth; however, YC-1 did not stimulate cyclic guanosine 3',5'-monophosphate production in this concentration range. It was also found that YC-1 activates the checkpoint kinase-mediated intra-S-phase checkpoint, independently of ataxia-telangiectasia mutated kinase or ataxia-telangiectasia mutated and Rad3-related kinase. These results imply that YC-1 does not promote the regrowth of hypoxic tumors because of its cell cycle arrest effect. Furthermore, YC-1 may induce the combined anticancer effects of HIF-1alpha inhibition and cell growth inhibition.

Sulindac independently modulates extracellular signal–regulated kinase 1/2 and cyclic GMP–dependent protein kinase signaling pathways

Colorectal cancer is the second leading cause of cancer mortality in the United States. Substantial human and animal data support the ability of nonsteroidal anti-inflammatory drugs to cause regression of existing colon tumors and prevent new tumor formation. The mechanism by which the nonsteroidal anti-inflammatory drug sulindac prevents tumor growth is poorly understood and seems complex as sulindac can modulate several growth-related signaling pathways. Sulindac metabolites simultaneously (a) increase cellular cyclic GMP and subsequently activate cyclic GMP-dependent protein kinase (PKG); (b) activate c-jun NH2-terminal kinase (JNK); (c) inhibit extracellular signal-regulated kinase 1/2 (ERK1/2); and (d) decrease beta-catenin protein expression at times and doses consistent with apoptosis. The purpose of this study was to determine if PKG, ERK1/2, JNK, and beta-catenin are independent targets for sulindac in vitro. Pharmacologic activation of PKG with YC-1 increases JNK phosphorylation and induces apoptosis in colon cancer cells without modulating ERK1/2 phosphorylation or beta-catenin protein expression. Inhibition of ERK1/2 with U0126 induces apoptosis but fails to activate JNK phosphorylation or down-regulate beta-catenin protein expression. Cotreatment with U0126 and YC-1 synergistically increases apoptosis in colorectal cancer cells and recapitulates the effects of sulindac treatment on ERK1/2, JNK, and beta-catenin. These results indicate that sulindac metabolites modulate ERK1/2 and PKG pathways independently in colon cancer cells and suggest that the full apoptotic effect of sulindac is mediated by more than one pathway. Using similar combinatorial approaches in vivo may provide more effective, less toxic chemopreventive and chemotherapeutic strategies. Such therapies could dramatically reduce the incidence and death rate from colorectal cancer.

YC-1 suppresses constitutive nuclear factor-κB activation and induces apoptosis in human prostate cancer cells

Although the indazole compound, YC-1, is reported to exert anticancer activities in several cancer cell types, its target and mechanism of action have not been well explored. The objectives of this study were to ascertain whether YC-1 directly induces apoptosis in prostate cancer cells and to explore the mechanism(s) whereby YC-1 causes cell death. Hormone-refractory metastatic human prostate cancer PC-3 cells were selected for this study. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay indicated that YC-1 suppresses growth of PC-3 cells in a concentration-dependent and time-dependent manner. Apoptosis was determined using 4',6-diamidino-2-phenylindole staining, and cell cycle progression was examined by FACScan flow cytometry. YC-1 treatment showed chromatin condensation and increased the percentage of PC-3 cells in the hypodiploid sub-G0-G1 phase, indicative of apoptosis. Additionally, exposure to YC-1 was found to induce activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase. Translocation and activation of nuclear factor-kappaB (NF-kappaB) were determined by immunofluorescent staining and ELISA, respectively. The results showed that YC-1 abolished constitutive nuclear translocation and activation of NF-kappaB/p65. Furthermore, inhibition of inhibitor of kappaBalpha (IkappaBalpha) phosphorylation and accumulation of IkappaBalpha were observed. The antitumor effects of YC-1 were evaluated by measuring the growth of tumor xenografts in YC-1-treated severe combined immunodeficient mice. The volumes of PC-3 tumors produced in severe combined immunodeficient mice were observed to decline significantly after treatment with YC-1 compared with vehicle controls. We concluded that the antitumor effects of YC-1 in PC-3 cells include the induction of apoptosis and the suppression of NF-kappaB activation. Given these unique actions, further investigations of the effects of YC-1 against hormone-refractory prostate cancer are warranted.

YC-1-inhibited proliferation of rat mesangial cells through suppression of cyclin D1-independent of cGMP pathway and partially reversed by p38 MAPK inhibitor

This study was designed to investigate the effect of 1-benzyl-3-(5'-hydroxymethyl-2'-furyl) indazole (YC-1), a guanylate cyclase activator, upon the proliferation of rat mesangial cells and its underlying mechanism. YC-1 inhibited cell proliferation and DNA synthesis in a dose- and time-dependent manner. Flow cytometry cell-cycle studies revealed that YC-1 prevented the entry of cells from G1 into S phase. The expression of cyclin D1 and the kinase activity of cyclin D1/cyclin-dependent kinase (CDK)4 were lower within YC-1-treated cells, revealed by Western blotting, Northern blotting and kinase assays. YC-1 did not increase the intracellular cGMP concentration in mesangial cells. Inhibitors of soluble guanylate cyclase, protein kinase G, or protein kinase A also did not reverse the inhibitory effect elicited by YC-1, while co-treatment with p38 mitogen-activated protein kinase (MAPK) inhibitor could partially reverse the suppressive effect. YC-1 inhibited proliferation of mesangial cells and induced cell-cycle arrest by the reduction of cyclin D1 synthesis and cyclin D1/CDK4 kinase activity. This effect acts partially through p38 MAPK signal transduction activation and is independent of cGMP-signaling pathways.

YC-1 [3-(5′-Hydroxymethyl-2′-furyl)-1-benzyl Indazole] Inhibits Endothelial Cell Functions Induced by Angiogenic Factors in Vitro and Angiogenesis in Vivo Models

Angiogenesis is a process that involves endothelial cell proliferation, migration, invasion, and tube formation, and inhibition of these processes has implications for angiogenesis-mediated disorders. The purpose of this study was to evaluate the antiangiogenic efficacy of YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole] in well characterized in vitro and in vivo systems. YC-1 inhibited the ability of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in a dose-dependent manner to induce proliferation, migration, and tube formation in human umbilical vascular endothelial cells; these outcomes were evaluated using [3H]thymidine incorporation, transwell chamber, and Matrigel-coated slide assays, respectively. YC-1 inhibited VEGF- and bFGF-induced p42/p44 mitogen-activated protein kinase and Akt phosphorylation as well as protein kinase C alpha translocation using Western blot analysis. The effect of YC-1 on angiogenesis in vivo was evaluated using the mouse Matrigel implant model. YC-1 administered orally in doses of 1 to 100 mg/kg/day inhibited VEGF- and bFGF-induced neovascularization in a dose-dependent manner over 7 days. These results indicate that YC-1 has antiangiogenic activity at very low doses. Moreover, in transplantable murine tumor models, YC-1 administered orally displayed a high degree of antitumor activity (treatment-to-control life span ratio > 175%) without cytotoxicity. YC-1 may be useful for treating angiogenesis-dependent human diseases such as cancer.