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

Revisiting prostate cancer metabolism: From metabolites to disease and therapy

Prostate cancer (PCa), one of the most commonly diagnosed cancers worldwide, still presents important unmet clinical needs concerning treatment. In the last years, the metabolic reprogramming and the specificities of tumor cells emerged as an exciting field for cancer therapy. The unique features of PCa cells metabolism, and the activation of specific metabolic pathways, propelled the use of metabolic inhibitors for treatment. The present work revises the knowledge of PCa metabolism and the metabolic alterations that underlie the development and progression of the disease. A focus is given to the role of bioenergetic sources, namely, glucose, lipids, and glutamine sustaining PCa cell survival and growth. Moreover, it is described as the action of oncogenes/tumor suppressors and sex steroid hormones in the metabolic reprogramming of PCa. Finally, the status of PCa treatment based on the inhibition of metabolic pathways is presented. Globally, this review updates the landscape of PCa metabolism, highlighting the critical metabolic alterations that could have a clinical and therapeutic interest.

Tumor Hypoxia As an Enhancer of Inflammation-Mediated Metastasis: Emerging Therapeutic Strategies

Metastasis is the leading cause of cancer-related deaths. Recent research has implicated tumor inflammation as a promoter of metastasis. Myeloid, lymphoid, and mesenchymal cells in the tumor microenvironment promote inflammatory signaling amongst each other and together with cancer cells to modulate sustained inflammation, which may enhance cancer invasiveness. Tumor hypoxia, a state of reduced available oxygen present in the majority of solid tumors, acts as a prognostic factor for a worse outcome and is known to have a role in tumor inflammation through the regulation of inflammatory mediator signals in both cancer and neighboring cells in the microenvironment. Multiple methods to target tumor hypoxia have been developed and tested in clinical trials, and still more are emerging as the impacts of hypoxia become better understood. These strategies include mechanistic inhibition of the hypoxia inducible factor signaling pathway and hypoxia activated pro-drugs, leading to both anti-tumor and anti-inflammatory effects. This prompts a need for further research on the prevention of hypoxia-mediated inflammation in cancer. Hypoxia-targeting strategies seem to have the most potential for therapeutic benefit when combined with traditional chemotherapy agents. This paper will serve to summarize the role of the inflammatory response in metastasis, to discuss how hypoxia can enable or enhance inflammatory signaling, and to review established and emerging strategies to target the hypoxia-inflammation-metastasis axis.

YC‑1 reduces inflammatory responses by inhibiting nuclear factor‑κB translocation in mice subjected to transient focal cerebral ischemia

3‑(5‑hydroxymethyl‑2‑furyl)‑1‑benzyl‑indazole (YC‑1) is understood to protect against ischemic stroke, but the molecular basis for its neuroprotection remains to be fully characterized. The present study investigated the influence of YC‑1 on inflammatory responses following experimental stroke. Previous studies indicated that nuclear factor (NF)‑κB‑driven signals serve a pivotal role in mediating inflammatory responses following stroke. Ischemic stroke results in activation of NF‑κB to induce gene expression of factors including inducible nitric oxide synthase, interleukin (IL)‑1β, IL‑6 and matrix metalloproteinases (MMPs). The results of the present study demonstrated that YC‑1 effectively reduced brain infarction and brain edema, and improved blood‑brain barrier leakage. Additionally, animals treated with YC‑1 exhibited significant reductions in neutrophil and macrophage infiltration into the ischemic brain. Furthermore, YC‑1 effectively inhibited NF‑κB translocation and binding activity, and the activity and expression of MMP‑9 following ischemic stroke. In conclusion, YC‑1 may effectively attenuate NF‑κB‑induced inflammatory damage following cerebral ischemia‑reperfusion.

Pharmacological HIF-inhibition attenuates postoperative adhesion formation

Peritoneal adhesions represent a common complication of abdominal surgery, and tissue hypoxia is a main determinant in adhesion formation. Reliable therapeutic options to reduce peritoneal adhesions are scarce. We investigated whether the formation of postsurgical adhesions can be affected by pharmacological interference with hypoxia-inducible factors (HIFs). Mice were treated with a small molecule HIF-inhibitor, YC-1 (3-[5′-Hydroxymethyl-2′-furyl]-1-benzyl-indazole), or vehicle three days before and seven days after induction of peritoneal adhesions or, alternatively, once during induction of peritoneal adhesions. Pretreatment or single intraperitoneal lavage with YC-1 significantly reduced postoperative adhesion formation without prompting systemic adverse effects. Expression analyses of cytokines in peritoneal tissue and fluid and in vitro assays applying macrophages and peritoneal fibroblasts indicated that this effect was cooperatively mediated by various putatively HIF-1α-dependent mechanisms, comprising attenuated pro-inflammatory activation of macrophages, impaired recruitment and activation of peritoneal fibroblasts, mitigated epithelial-mesenchymal-transition (EMT), as well as enhanced fibrinolysis and impaired angiogenesis. Thus, this study identifies prevention of postsurgical peritoneal adhesions as a novel and promising field for the application of HIF inhibitors in clinical practice.

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.

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.

Nuclear factor kappa-B signaling is integral to ocular neovascularization in ischemia-independent microenvironment

Retinal ischemia promotes the upregulation of VEGF expression and accounts for most pathological features of retinal neovascularization (NV). Paradoxically, VEGF remains the pivotal stimulator of ocular NV, despite the absence of ischemia. Therefore, the central question arises as to how the various molecular mechanisms interplay in ischemia-independent NV. It's been suggested that NFκB plays a crucial role in the pathogenesis of diabetic vasculopathies. Here, we dissected the molecular mechanism of ocular NV in the rho/VEGF transgenic mouse model, which develops subretinal NV in ischemia-independent microenvironment. Furthermore, we examined whether intravitreal administration of YC-1, a HIF-1 inhibitor, can modulate the activation of NFκB and its downstream angiogenic signaling in the mouse retina. We demonstrated that YC-1 inhibited retinal NFκB/p65 DNA binding activity and downregulated NFκB/p65, FAK, α5β1, EPO, ET-1, and MMP-9 expression at the message and the protein levels. In addition, YC-1 significantly inhibited subretinal NV by reducing the number of neovascular lesions, the area of each lesion and the total area of NV per retina. We further investigated the influence of VEGF signaling pathway on HIF-1α transcriptional activity to substantiate that this mouse model develops subretinal NV in an ischemia-independent microenvironment. Our data demonstrated that VEGF overexpression didn't have any impact on HIF-1α transcriptional activity, whereas treatment with YC-1 significantly inhibited endogenous HIF-1 activity. Our study suggests that retinal NFκB transcriptional activity is pivotal to ischemia-independent mechanisms, which lead to the local activation of angiogenic cascades. Our data also indicate that the nexus between VEGF and NFκB is implicated in triggering the angiogenic cascade that promotes retinal NV. Hence, targeting the VEGF/NFκB axis may act in a negative feedback loop to suppress ocular NV. This study suggests that inhibition of NFκB activation may be a means of turning off a “master switch” responsible for initiating and perpetuating these ocular pathologies.

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.

Inhibition of NF-κB by opioids in T cells

Opioids potently inhibit a number of physiological and pathophysiological effects such as pain and inflammation in the brain and the periphery. One of the targets of opioids mediating such effects is the proinflammatory transcription factor NF-κB. In neuronal cells, opioids inhibit this factor by inducing I-κB independently on calcium, involving the opioid-mediated activation of the transcription factor AP-1. However, when and how precisely NF-κB is modulated by opioids in T cells are unknown. By using the TNF-triggered, NF-κB-mediated induction of IL-8 mRNA in primary human T cells and Jurkat T cells, in this study we show that opioids inhibit NF-κB in T cells as well, but that the underlying mechanisms are different from those observed in neuronal cells. We found that stimulation of the T cells with opioids resulted in a significant inhibition of the TNF-triggered ubiquitination and degradation of I-κB. Additionally, an opioid-mediated induction of the deubiquitinating enzyme ubiquitin-specific protease 15 was observed, which is known to inhibit the NF-κB pathway by stabilizing I-κB. The induction of ubiquitin-specific protease 15 was dependent on calcium and the transcription factor NFAT. Activation of AP-1 and induction of I-κB in response to the opioids were not observed in the T cells. These results indicate that μ opioid receptors, which mediate the effects in both cell types, might be coupled to different effector cascades in the different cell types, which may then result in cell type-specific effects of the drugs.

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.

The nexus between VEGF and NFκB orchestrates a hypoxia-independent neovasculogenesis

Nuclear Factor-Kappa B [NFκB] activation triggers the elevation of various pro-angiogenic factors that contribute to the development and progression of diabetic vasculopathies. It has been demonstrated that vascular endothelial growth factor [VEGF] activates NFκB signaling pathway. Under the ischemic microenvironments, hypoxia-inducible factor-1 [HIF-1] upregulates the expression of several proangiogenic mediators, which play crucial roles in ocular pathologies. Whereas YC-1, a soluble guanylyl cyclase [sGC] agonist, inhibits HIF-1 and NFκB signaling pathways in various cell and animal models. Throughout this investigation, we examined the molecular link between VEGF and NFκB under a hypoxia-independent microenvironment in human retinal microvascular endothelial cells [hRMVECs]. Our data indicate that VEGF promoted retinal neovasculogenesis via NFκB activation, enhancement of its DNA-binding activity, and upregulating NFκB/p65, SDF-1, CXCR4, FAK, αVβ3, α5β1, EPO, ET-1, and MMP-9 expression. Conversely, YC-1 impaired the activation of NFκB and its downstream signaling pathways, via attenuating IκB kinase phosphorylation, degradation and activation, and thus suppressing p65 phosphorylation, nuclear translocation, and inhibiting NFκB-DNA binding activity. We report for the first time that the nexus between VEGF and NFκB is implicated in coordinating a scheme that upregulates several pro-angiogenic molecules, which promotes retinal neovasculogenesis. Our data may suggest the potential use of YC-1 to attenuate the deleterious effects that are associated with hypoxia/ischemia-independent retinal vasculopathies.

The anticancer agent YC-1 suppresses progestin-stimulated VEGF in breast cancer cells and arrests breast tumor development

Recent epidemiological studies show that postmenopausal women taking estrogen-progestin hormone replacement therapy (HRT) have a higher risk of breast cancer than women on an HRT regimen lacking progestins. This may be related to the observation that progestin-treated breast cancer cells express and secrete high levels of vascular endothelial growth factor (VEGF), a potent angiogenic factor that promotes breast tumor growth. Anti-progestins such as RU-486 block this effect, indicating that progesterone receptors (PR) are involved in promoting VEGF induction; however antiprogestins cross-react with other steroid receptors which limits their clinical use. Alternative strategies are, therefore, needed to arrest the growth of progestin-dependent tumors. 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole (YC-1), a novel anticancer drug initially developed as an inhibitor of HIF-1α, is currently undergoing preclinical trials against various forms of cancer. Since HIF-1α has recently been implicated in PR-mediated VEGF synthesis, we undertook studies to determine whether YC-1 inhibits progestin-dependent VEGF induction and tumor progression. Surprisingly, we found that YC-1 downregulated PR in human breast cancer cells, both in vivo and in vitro, thereby blocking progestin-dependent induction of VEGF and tumor growth. YC-1 also inhibited progestin-accelerated DMBA-induced mammary tumors in rats, properties which would likely render it effective against progestin-dependent tumors which frequently develop in post-menopausal women. We, therefore, propose that based on our observations, YC-1 warrants further investigation as a novel agent which could prove extremely useful as an anti-angiogenic chemotherapeutic drug.

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.

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.

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.

YC-1 rescues cancer cachexia by affecting lipolysis and adipogenesis

Loss of adipose tissue, primarily due to increased lipolysis but also to an impairment of adipogenesis, is a key feature of weight loss in cancer cachexia. Because of the myriad pathogenic signaling pathways essential for atrophy of adipose tissue, effective therapeutic agents for cachectic adipose loss are lacking and urgently needed. The authors evaluated the effects of YC-1 on adipogenesis of 3T3-L1 preadipocytes, TNF-α- and tumor-cell-induced lipolysis in 3T3-L1 adipocytes, and cachectic weight loss in colon-26 adenocarcinoma-bearing mice because YC-1 has been shown to possess versatile pharmacological actions, including anticancer activity. It was found that YC-1 promotes the differentiation of 3T3-L1 preadipocytes into adipocytes through activation of Akt and extracellular signal-regulated kinase (ERK) signaling pathways as well as activation of several adipogenic mediators, such as peroxisome proliferator-activated receptor γ (PPARγ), insulin receptor α (IRα), insulin receptor substrate-3 (IRS-3) and glucose transporter-4 (GLUT-4). In the in vitro lipolysis models, YC-1 attenuates TNF-α-induced lipolysis of adipocytes by antagonizing TNF-α-mediated activation of ERK and downregulation of perilipin (PLIN). It was also found that YC-1 inhibits colon-26 adenocarcinoma cell-induced lipolysis of 3T3-L1 adipocytes. Moreover, YC-1 effectively rescues cachectic weight loss in colon-26 adenocarcinoma-bearing mice by blocking lipolysis, involving insulin. Taken together the results show that YC-1 with its anticancer and anticachexia talents is highly worth developing as a novel agent for cancer therapy.

YC-1, a novel potential anticancer agent, inhibit multidrug-resistant protein via cGMP-dependent pathway

The aim of the present study was to evaluate the effect of 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) on multidrug resistance. Expression of human P-glycoprotein was assessed by realtime quantitative RT-PCR and western blot. The efflux function of P-glycoprotein was evaluated by rhodamine 123 accumulation and calcein-AM uptake models. The mechanisms of action of YC-1 on different signaling pathways were studied using series of antagonists and the kinetics was also assessed. Cytotoxicity was evaluated by MTT assay. The results demonstrated that increased intracellular accumulation of rhodamine 123 and increased fluorescence of calcein were observed after YC-1 treatment. Furthermore, increased YC-1 concentration resulted in significant decrease in Vmax while K(M) remained unchanged suggested that YC-1 acted as a noncompetitive inhibitor of P-glycoprotein. Moreover, the inhibition of Pgp efflux function by YC-1 was significantly reversed by NO synthase inhibitor, (L)-NAME, the sGC inhibitor, ODQ, the PKG inhibitor, Rp-8-Br-PET-cGMPS, and the PKG inhibitor KT5823. In addition, ERK kinase inhibitor PD98059 also significantly restored YC-1 inhibited Pgp efflux function. These results indicated that YC-1 inhibited Pgp efflux via the NO-cGMP-PKG-ERK signaling pathway through noncompetitive inhibition. The present study revealed that YC-1 could be a good candidate for development as a MDR modulator.

The ubiquitin-proteasome system in prostate cancer and its transition to castration resistance

Prostate cancer is the most common carcinoma in the male population. In its initial stage, the disease is androgen-dependent and responds therapeutically to androgen deprivation treatment but it usually progresses after a few years to an androgen-independent phase that is refractory to hormonal manipulations. The proteasome is a multi-unit protease system that regulates the abundance and function of a significant number of cell proteins, and its inhibition results in cancer cell growth inhibition and apoptosis and is already exploited in the clinic with the use of proteasome inhibitor bortezomib in multiple myeloma. In order to be recognized by the proteasome, a target protein needs to be linked to a chain of the small protein ubiquitin. In this paper, we review the role of ubiquitin-proteasome system (UPS) in androgen receptor-dependent transcription as well as in the castration resistant stage of the disease, and we discuss therapeutic opportunities that UPS inhibition offers in prostate cancer.

Effects of TLR agonists on the hypoxia-regulated transcription factor HIF-1alpha and dendritic cell maturation under normoxic conditions

Dendritic cells (DC) are professional antigen presenting cells that represent an important link between innate and adaptive immunity. Danger signals such as toll-like receptor (TLR) agonists induce maturation of DC leading to a T-cell mediated adaptive immune response. In this study, we show that exogenous as well as endogenous inflammatory stimuli for TLR4 and TLR2 induce the expression of HIF-1alpha in human monocyte-derived DC under normoxic conditions. On the functional level, inhibition of HIF-1alpha using chetomin (CTM), YC-1 and digoxin lead to no consistent effect on MoDC maturation, or cytokine secretion despite having the common effect of blocking HIF-1alpha stabilization or activity through different mechanisms. Stabilization of HIF-1alpha protein by hypoxia or CoCl(2) did not result in maturation of human DC. In addition, we could show that TLR stimulation resulted in an increase of HIF-1alpha controlled VEGF secretion. These results show that stimulation of human MoDC with exogenous as well as endogenous TLR agonists induces the expression of HIF-1alpha in a time-dependent manner. Hypoxia alone does not induce maturation of DC, but is able to augment maturation after TLR ligation. Current evidence suggests that different target genes may be affected by HIF-1alpha under normoxic conditions with physiological roles that differ from those induced by hypoxia.

Reverse phase protein array identifies novel anti-invasion mechanisms of YC-1

YC-1 has recently been demonstrated to have potent anti-invasion and anti-metastatic activity in several cancer models, in addition to its anti-proliferation activity. However, the mechanism underlying its anti-invasion/anti-metastatic activity is largely unknown. Nasopharyngeal carcinoma (NPC) is a highly metastatic head and neck cancer in Southeast Asia. Here, we demonstrated that YC-1 inhibited invasiveness and proliferation of NPC cells, with the latter being accompanied by PARP cleavage, S-phase arrest and activation of Chk1/Chk2. We aimed at identifying novel anti-invasion mechanisms of YC-1 in NPC by a functional proteomic platform, the reverse phase protein array (RPPA). Our study revealed for the first time that multiple invasion-related signaling proteins (beta-catenin, caveolin, Src and EGFR), as well as several growth-related proteins (AMPKalpha, phospho-acetyl-CoA carboxylase (p-ACC), HER-2 and mTOR), which were previously un-described signaling proteins altered by YC-1, were found to be down-modulated by YC-1 in NPC cells. We hypothesized that YC-1-mediated downregulation of these invasion proteins contributed to its anti-invasion activity in NPC cells. Overexpression of EGFR, activated Src or caveolin, but not beta-catenin reversed the inhibitory effects of YC-1 on NPC cell invasion, with EGFR and activated Src having additional effects on rescuing NPC cells from YC-1-mediated growth inhibition. In summary, we have identified several novel anti-invasion mechanisms of YC-1 that could impact NPC, and possibly other cancers as well.

YC-1 enhances natural killer cell differentiation from hematopoietic stem cells

NK cells play crucial roles in innate immunity and adaptive immunity. The detailed mechanisms, however, governing NK cell development remains unclear. In this study, we report that YC-1 significantly enhances NK cell populations differentiated from human umbilical cord blood hematopoietic stem cells (HSCs). NK cells increased by YC-1 display both phenotypic and functional features of fully mature NK (mNK) cells, but YC-1 does not affect the activation of mNK cells. YC-1 did not affect cGMP production and phosphorylation of STAT-5 which is essential for IL-15R signaling. On the other hand, YC-1 increased p38 MAPK phosphorylation during NK cell differentiation. Furthermore, p38 inhibitor SB203580 inhibited the differentiation of NK cells enhanced by YC-1. Taken together, these data suggest that YC-1 enhances NK cell differentiation through the activation of p38 MAPK which is involved in NK cell differentiation.

Regulation of HIV-1 transcription in cells of the monocyte-macrophage lineage

Human immunodeficiency virus type 1 (HIV-1) has been shown to replicate productively in cells of the monocyte-macrophage lineage, although replication occurs to a lesser extent than in infected T cells. As cells of the monocyte-macrophage lineage become differentiated and activated and subsequently travel to a variety of end organs, they become a source of infectious virus and secreted viral proteins and cellular products that likely initiate pathological consequences in a number of organ systems. During this process, alterations in a number of signaling pathways, including the level and functional properties of many cellular transcription factors, alter the course of HIV-1 long terminal repeat (LTR)-directed gene expression. This process ultimately results in events that contribute to the pathogenesis of HIV-1 infection. First, increased transcription leads to the upregulation of infectious virus production, and the increased production of viral proteins (gp120, Tat, Nef, and Vpr), which have additional activities as extracellular proteins. Increased viral production and the presence of toxic proteins lead to enhanced deregulation of cellular functions increasing the production of toxic cellular proteins and metabolites and the resulting organ-specific pathologic consequences such as neuroAIDS. This article reviews the structural and functional features of the cis-acting elements upstream and downstream of the transcriptional start site in the retroviral LTR. It also includes a discussion of the regulation of the retroviral LTR in the monocyte-macrophage lineage during virus infection of the bone marrow, the peripheral blood, the lymphoid tissues, and end organs such as the brain. The impact of genetic variation on LTR-directed transcription during the course of retrovirus disease is also reviewed.

Inhibition of constitutive and cxc-chemokine-induced NF-kappaB activity potentiates ansamycin-based HSP90-inhibitor cytotoxicity in castrate-resistant prostate cancer cells

Background:

We determined how CXC-chemokine signalling and necrosis factor-κB (NF-κB) activity affected heat-shock protein 90 (Hsp90) inhibitor (geldanamycin (GA) and 17-allylamino-demethoxygeldanamycin (17-AAG)) cytotoxicity in castrate-resistant prostate cancer (CRPC).

Methods:

Geldanamycin and 17-AAG toxicity, together with the CXCR2 antagonist AZ10397767 or NF-κB inhibitor BAY11-7082, was assessed by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay in two CRPC lines, DU145 and PC3. Flow cytometry quantified apoptotic or necrosis profiles. Necrosis factor-κB activity was determined by luciferase readouts or indirectly by quantitative PCR and ELISA-based determination of CXCL8 expression.

Results:

Geldanamycin and 17-AAG reduced PC3 and DU145 cell viability, although PC3 cells were less sensitive. Addition of AZ10397767 increased GA (e.g., PC3 IC₂₀: from 1.67±0.4 to 0.18±0.2 nM) and 17-AAG (PC3 IC₂₀: 43.7±7.8 to 0.64±1.8 nM) potency in PC3 but not DU145 cells. Similarly, BAY11-7082 increased the potency of 17-AAG in PC3 but not in DU145 cells, correlating with the elevated constitutive NF-κB activity in PC3 cells. AZ10397767 increased 17-AAG-induced apoptosis and necrosis and decreased NF-κB activity/CXCL8 expression in 17-AAG-treated PC3 cells.

Conclusion:

Ansamycin cytotoxicity is enhanced by inhibiting NF-κB activity and/or CXC-chemokine signalling in CRPC cells. Detecting and/or inhibiting NF-κB activity may aid the selection and treatment response of CRPC patients to Hsp90 inhibitors.

A mass spectrometric investigation of the ability of metal complexes to modulate transcription factor activity

ESI mass spectrometry was used to assess the ability of metal complexes to inhibit binding of a transcription factor to a DNA molecule containing its recognition sequence.

Decrease in RelA phosphorylation by inhibiting protein kinase A induces cell death in NF-kappaB-expressing and drug-resistant tumor cells

The RelA (p65) is a subunit of nuclear transcription factor kappa B (NF-kappaB) and actively participates in expression of NF-kappaB-dependent genes involved in inflammation and tumorigenesis. Hence, the regulation of p65 is an important strategy to regulate those responses. In this study, we provide data that the dichlorophenyl derivative of 1,2,4-thiadiazolidine (known as P(3)-25) induced cell death in NF-kappaB-expressing and doxorubicin-resistant cells. P(3)-25 inhibited NF-kappaB DNA binding activity partially, but inhibited NF-kappaB-dependent genes expression completely. It inhibited phosphorylation of Rel A (p65) by inhibiting activity of protein kinase A (PKA). The PKA inhibition was independent of adenylate cyclase activity or cAMP level. The PKA activity decreased due to inhibition of catalytic subunit of PKA. P(3)-25 inhibited almost 80% PKA activity at 100 nM concentration, having an IC(50) at 10.5 nM. P(3)-25 potentiated different chemotherapeutic agents-mediated cell death. Our results suggest that P(3)-25 inhibits PKA activity followed by decreased phosphorylation of p65 and transcriptional activity of NF-kappaB thereby decreasing antiapoptotic proteins resulting in induction of apoptosis in NF-kappaB-expressing and doxorubicin-resistant cells. The study might help to understand the mechanism of P(3)-25-mediated apoptosis and to design it as new chemotherapeutic drug for tumor therapy.

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.

Chemotherapy-induced CXC-chemokine/CXC-chemokine receptor signaling in metastatic prostate cancer cells confers resistance to oxaliplatin through potentiation of nuclear factor-kappaB transcription and evasion of apoptosis

Constitutive activation of nuclear factor (NF)-kappaB is linked with the intrinsic resistance of androgen-independent prostate cancer (AIPC) to cytotoxic chemotherapy. Interleukin-8 (CXCL8) is a transcriptional target of NF-kappaB whose expression is elevated in AIPC. This study sought to determine the significance of CXCL8 signaling in regulating the response of AIPC cells to oxaliplatin, a drug whose activity is reportedly sensitive to NF-kappaB activity. Administration of oxaliplatin to PC3 and DU145 cells increased NF-kappaB activity, promoting antiapoptotic gene transcription. In addition, oxaliplatin increased the transcription and secretion of CXCL8 and the related CXC-chemokine CXCL1 and increased the transcription and expression of CXC-chemokine receptors, especially CXC-chemokine receptor (CXCR) 2, which transduces the biological effects of CXCL8 and CXCL1. Stimulation of AIPC cells with CXCL8 potentiated NF-kappaB activation in AIPC cells, increasing the transcription and expression of NF-kappaB-regulated antiapoptotic genes of the Bcl-2 and IAP families. Coadministration of a CXCR2-selective antagonist, AZ10397767 (Bioorg Med Chem Lett 18:798-803, 2008), attenuated oxaliplatin-induced NF-kappaB activation, increased oxaliplatin cytotoxicity, and potentiated oxaliplatin-induced apoptosis in AIPC cells. Pharmacological inhibition of NF-kappaBorRNA interference-mediated suppression of Bcl-2 and survivin was also shown to sensitize AIPC cells to oxaliplatin. Our results further support NF-kappaB activity as an important determinant of cancer cell sensitivity to oxaliplatin and identify the induction of autocrine CXCR2 signaling as a novel mode of resistance to this drug.

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.

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.

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.

Mechanisms of antiprostate cancer by gum mastic: NF-kappaB signal as target

AIM

To study the effect of gum mastic, a natural resin, on the proliferation of androgen-independent prostate cancer PC-3 cells, and further investigate the mechanisms involved in this regulatory system, taking nuclear factor kappaB (NF-kappaB) signal as the target.

METHODS

3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and a flow cytometer were used to detect the effect of gum mastic on the proliferation of PC-3 cells. Then, reporter gene assay, RT-PCR, and Western blotting were carried out to study the effects of gum mastic on the NF-kappaB protein level and the NF-kappaB signal pathway. The expression of genes involved in the NF-kappaB signal pathway, including cyclin D1, inhibitors of kappaBs (I kappaB alpha), and phosphorylated Akt (p-AKT), were measured. In addition, transient transfection assays with the 5X NF-kappaB consensus sequence promoter was also used to test the effects of gum mastic.

RESULTS

Gum mastic inhibited PC-3 cell growth and blocked the PC-3 cell cycle in the G1 phase. Gum mastic also suppressed NF-kappaB activity in the PC-3 cells. The expression of cyclin D1, a crucial cell cycle regulator and an NF-kappaB downstream target gene, was reduced as well. Moreover, gum mastic decreased the p-AKT protein level and increased the I kappa B alpha protein level.

CONCLUSION

Gum mastic inhibited the proliferation and blocked the cell cycle progression in PC-3 cells by suppressing NF-kappaB activity and the NF-kappaB signal pathway.

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.

YC-1 inhibits HIF-1 expression in prostate cancer cells: contribution of Akt/NF-kappaB signaling to HIF-1alpha accumulation during hypoxia

Hypoxia-inducible factor 1 (HIF-1), a transcription factor that is critical for tumor adaptation to microenvironmental stimuli, represents an attractive chemotherapeutic target. YC-1 is a novel antitumor agent that inhibits HIF-1 through previously unexplained mechanisms. In the present study, YC-1 was found to prevent HIF-1alpha and HIF-1beta accumulation in response to hypoxia or mitogen treatment in PC-3 prostate cancer cells. Neither HIF-1alpha protein half-life nor mRNA level was affected by YC-1. However, YC-1 was found to suppress the PI3K/Akt/mTOR/4E-BP pathway, which serves to regulate HIF-1alpha expression at the translational step. We demonstrated that YC-1 also inhibited hypoxia-induced activation of nuclear factor (NF)-kappaB, a downstream target of Akt. Two modulators of the Akt/NF-kappaB pathway, caffeic acid phenethyl ester and evodiamine, were observed to decrease HIF-1alpha expression. Additionally, overexpression of NF-kappaB partly reversed the ability of wortmannin to inhibit HIF-1alpha-dependent transcriptional activity, suggesting that NF-kappaB contributes to Akt-mediated HIF-1alpha accumulation during hypoxia. Overall, we identify a potential molecular mechanism whereby YC-1 serves to reduce HIF-1 expression.

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.

Targeting transcription factors in cancer: Challenges and evolving strategies

As investigators uncover the molecular pathways leading to cancer, an abundance of potential molecular targets is accumulating. Among these targets, transcription factors are especially promising. This review discusses the reasons for focusing targeting efforts on transcription factors and highlights some salient examples. The advantages and problems with current methods for targeting are summarized. Finally, we discuss the drug delivery technologies in development that may one day make transcription factor targeting a therapeutic reality.: