Inhibition of angiogenesis and invasion by 3,3'-diindolylmethane is mediated by the nuclear factor-kappaB downstream target genes MMP-9 and uPA that regulated bioavailability of vascular endothelial growth factor in prostate cancer

Notch-1 induces epithelial-mesenchymal transition consistent with cancer stem cell phenotype in pancreatic cancer cells

Activation of Notch-1 is known to be associated with the development and progression of human malignancies including pancreatic cancer. Emerging evidence suggest that the acquisition of epithelial-mesenchymal transition (EMT) phenotype and induction of cancer stem cell (CSC) or cancer stem-like cell phenotype are interrelated and contributes to tumor recurrence and drug resistance. The molecular mechanism(s) by which Notch-1 contributes to the acquisition of EMT phenotype and CSC self-renewal capacity has not been fully elucidated. Here we show that forced over-expression of Notch-1 leads to increased cell growth, clonogenicity, migration and invasion of AsPC-1 cells. Moreover, over-expression of Notch-1 led to the induction of EMT phenotype by activation of mesenchymal cell markers such as ZEB1, CD44, EpCAM, and Hes-1. Here we also report, for the first time, that over-expression of Notch-1 leads to increased expression of miR-21, and decreased expression of miR-200b, miR-200c, let-7a, let-7b, and let-7c. Re-expression of miR-200b led to decreased expression of ZEB1, and vimentin, and increased expression of E-cadherin. Over-expression of Notch-1 also increased the formation of pancreatospheres consistent with expression of CSC surface markers CD44 and EpCAM. Finally, we found that genistein, a known natural anti-tumor agent inhibited cell growth, clonogenicity, migration, invasion, EMT phenotype, formation of pancreatospheres and expression of CD44 and EpCAM. These results suggest that the activation of Notch-1 signaling contributes to the acquisition of EMT phenotype, which is in part mediated through the regulation of miR-200b and CSC self-renewal capacity, and these processes could be attenuated by genistein treatment.

Mechanisms and therapeutic implications of cell death induction by indole compounds

Indole compounds, obtained from cruciferous vegetables, are well-known for their anti-cancer properties. In particular, indole-3-carbinol (I3C) and its dimeric product, 3,3′-diindolylmethane (DIM), have been widely investigated for their effectiveness against a number of human cancers in vitro as well as in vivo. These compounds are effective inducers of apoptosis and the accumulating evidence documenting their ability to modulate multiple cellular signaling pathways is a testimony to their pleiotropic behavior. Here we attempt to update current understanding on the various mechanisms that are responsible for the apoptosis-inducing effects by these compounds. The significance of apoptosis-induction as a desirable attribute of anti-cancer agents such as indole compounds cannot be overstated. However, an equally intriguing property of these compounds is their ability to sensitize cancer cells to standard chemotherapeutic agents. Such chemosensitizing effects of indole compounds can potentially have major clinical implications because these non-toxic compounds can reduce the toxicity and drug-resistance associated with available chemotherapies. Combinational therapy is increasingly being realized to be better than single agent therapy and, through this review article, we aim to provide a rationale behind combination of natural compounds such as indoles with conventional therapeutics.

Attenuation of multi-targeted proliferation-linked signaling by 3,3'-diindolylmethane (DIM): from bench to clinic

Emerging evidence provide credible support in favor of the potential role of bioactive products derived from ingesting cruciferous vegetables such as broccoli, brussel sprouts, cauliflower and cabbage. Among many compounds, 3,3'-diindolylmethane (DIM) is generated in the acidic environment of the stomach following dimerization of indole-3-carbinol (I3C) monomers present in these classes of vegetables. Both I3C and DIM have been investigated for their use in preventing, inhibiting, and reversing the progression of cancer - as a chemopreventive agent. In this review, we summarize an updated, wide-ranging pleiotropic anti-tumor and biological effects elicited by DIM against tumor cells. It is unfeasible to point one single target as basis of cellular target of action of DIM. We emphasize key cellular and molecular events that are effectively modulated in the direction of inducing apoptosis and suppressing cell proliferation. Collectively, DIM orchestrates signaling through Ah receptor, NF-κB/Wnt/Akt/mTOR pathways impinging on cell cycle arrest, modulation of key cytochrome P450 enzymes, altering angiogenesis, invasion, metastasis and epigenetic behavior of cancer cells. The ability of DIM to selectively induce tumor cells to undergo apoptosis has been observed in preclinical models, and thus it has been speculated in improving the therapeutic efficacy of other anticancer agents that have diverse molecular targets. Consequently, DIM has moved through preclinical development into Phase I clinical trials, thereby suggesting that DIM could be a promising and novel agent either alone or as an adjunct to conventional therapeutics such as chemo-radio and targeted therapies. An important development has been the availability of DIM formulation with superior bioavailability for humans. Therefore, DIM appears to be a promising chemopreventive agent or chemo-radio-sensitizer for the prevention of tumor recurrence and/or for the treatment of human malignancies.

In vitro anti-angiogenic properties of LGD1069, a selective retinoid X-receptor agonist through down-regulating Runx2 expression on Human endothelial cells

Background

LGD1069 (Targretin^®) is a selective retinoid X receptor (RXR) ligand, which is used in patients for cutaneous T-cell lymphoma. Our published study reported that LGD1069 inhibited tumor-induced angiogenesis in non-small cell lung cancer. In present study, we found that LGD1069 suppressed the proliferation, adhesion, invasion and migration of endothelial cells directly, and affected the expression of vegf and some matrix genes.

Methods

Human umbilical vein endothelial cells (HUVECs) were used for in vitro study. MTT assay and Sulforhodamine B assay were used for cell viability assay; the tube formation assay was used to investigate the effect of LGD1069 on angiogenesis in vitro. In vitro adhesion, migration and invasion of HUVEC cells were analyzed by Matrigel adhesion, migration and invasion assay. Gene expressions were measured by RT-PCR and Western blot analysis.

Results

Our data showed here that LGD1069 inhibited the activation of TGF-β/Smad pathway significantly. Furthermore, it was demonstrated that expression of Runx2 was suppressed pronouncedly during incubation with LGD1069. Runx2 is a DNA-binding transcription factor which plays a master role in tumor-induced angiogenesis and cancer cells metastasis by interaction with the TGF-β/Smad pathway of transcriptional modulators.

Conclusions

Our results suggested that LGD1069 may impair angiogenic and metastatic potential induced by tumor cells through suppressing expression of Runx2 directly on human endothelial cells, which may point out new pathway through which LGD1069 display anti-angiogenic properties, and provide new molecular evidence to support LGD1069 as a potent anti-metastatic agent in cancer therapy.

Diosgenin, a steroidal saponin, inhibits migration and invasion of human prostate cancer PC-3 cells by reducing matrix metalloproteinases expression

Background

Diosgenin, a steroidal saponin obtained from fenugreek (Trigonella foenum graecum), was found to exert anti-carcinogenic properties, such as inhibiting proliferation and inducing apoptosis in a variety of tumor cells. However, the effect of diosgenin on cancer metastasis remains unclear. The aim of the study is to examine the effect of diosgenin on migration and invasion in human prostate cancer PC-3 cells.

Methods and Principal Findings

Diosgenin inhibited proliferation of PC-3 cells in a dose-dependent manner. When treated with non-toxic doses of diosgenin, cell migration and invasion were markedly suppressed by in vitro wound healing assay and Boyden chamber invasion assay, respectively. Furthermore, diosgenin reduced the activities of matrix metalloproteinase-2 (MMP-2) and MMP-9 by gelatin zymography assay. The mRNA level of MMP-2, -9, -7 and extracellular inducer of matrix metalloproteinase (EMMPRIN) were also suppressed while tissue inhibitor of metalloproteinase-2 (TIMP-2) was increased by diosgenin. In addition, diosgenin abolished the expression of vascular endothelial growth factor (VEGF) in PC-3 cells and tube formation of endothelial cells. Our immunoblotting assays indicated that diosgenin potently suppressed the phosphorylation of phosphatidylinositide-3 kinase (PI3K), Akt, extracellular signal regulating kinase (ERK) and c-Jun N-terminal kinase (JNK). In addition, diosgenin significantly decreased the nuclear level of nuclear factor kappa B (NF-κB), suggesting that diosgenin inhibited NF-κB activity.

Conclusion/Significance

The results suggested that diosgenin inhibited migration and invasion of PC-3 cells by reducing MMPs expression. It also inhibited ERK, JNK and PI3K/Akt signaling pathways as well as NF-κB activity. These findings reveal new therapeutic potential for diosgenin in anti-metastatic therapy.

Broccoli-derived phytochemicals indole-3-carbinol and 3,3'-diindolylmethane exerts concentration-dependent pleiotropic effects on prostate cancer cells: comparison with other cancer preventive phytochemicals

In the present studies, we utilized prostate cancer cell culture models to elucidate the mechanisms of action of broccoli-derived phytochemicals 3,3'-diindolylmethane (DIM) and indole-3-carbinol (I3C). We found DIM and I3C at 1-5 µM inhibited androgen and estrogen-mediated pathways and induced xenobiotic metabolism pathway. By contrast, DIM and I3C induced cyclin inhibitors, indicators of stress/DNA damage, only at ≥25 µM. We also demonstrated that an inhibitory effect of DIM and I3C on cell growth involves inhibition of insulin-like growth factor-1 receptor expression. More importantly, we showed that differences in efficacies and mechanisms existed between DIM and I3C. These included differences in effective concentrations, a differential effect on androgen receptor binding, and a differential effect on xenobiotic metabolic pathway through aryl hydrocarbon receptor-dependent and -independent mechanism. Furthermore we determined that several other diet-derived cancer protective compounds, similar to DIM and I3C, exhibited pleiotrophic effects on signaling pathways that included proliferation, cell cycle, and nuclear receptors-mediated pathways. However, the efficacies and mechanisms of these compounds vary. We also showed that some cellular pathways are not likely to be affected by DIM or I3C when circulating concentration of orally ingested DIM or I3C is considered. Based on our results, a model for cancer protective effects of DIM and I3C was proposed.

Catalytic activity of Matrix metalloproteinase-19 is essential for tumor suppressor and anti-angiogenic activities in nasopharyngeal carcinoma

The association of Matrix metalloproteinase-19 (MMP19) in the development of nasopharyngeal carcinoma (NPC) was identified from differential gene profiling, which showed MMP19 was one of the candidate genes down-regulated in the NPC cell lines. In this study, quantitative RT-PCR and Western blot analysis showed MMP19 was down-regulated in all seven NPC cell lines. By tissue microarray immunohistochemical staining, MMP19 appears down-regulated in 69.7% of primary NPC specimens. Allelic deletion and promoter hypermethylation contribute to MMP19 down-regulation. We also clearly demonstrate that the catalytic activity of MMP19 plays an important role in antitumor and antiangiogenesis activities in comparative studies of the wild-type and the catalytically inactive mutant MMP19. In the in vivo tumorigenicity assay, only the wild-type (WT), but not mutant, MMP19 transfectants suppress tumor formation in nude mice. In the in vitro colony formation assay, WT MMP19 dramatically reduces colony-forming ability of NPC cell lines, when compared to the inactive mutant. In the tube formation assay of human umbilical vein endothelial cells and human microvascular endothelial cells (HMEC-1), secreted WT MMP19, but not mutant MMP19, induces reduction of tube-forming ability in endothelial cells with decreased vascular endothelial growth factor (VEGF) in conditioned media detected by enzyme-linked immunosorbent assay (ELISA). The anti-angiogenic activity of WT MMP19 is correlated with suppression of tumor formation. These results now clearly show that catalytic activity of MMP19 is essential for its tumor suppressive and anti-angiogenic functions in NPC.

Estrogen induced metastatic modulators MMP-2 and MMP-9 are targets of 3,3'-diindolylmethane in thyroid cancer

BACKGROUND

Thyroid cancer is the most common endocrine related cancer with increasing incidences during the past five years. Current treatments for thyroid cancer, such as surgery or radioactive iodine therapy, often require patients to be on lifelong thyroid hormone replacement therapy and given the significant recurrence rates of thyroid cancer, new preventive modalities are needed. The present study investigates the property of a natural dietary compound found in cruciferous vegetables, 3,3'-diindolylmethane (DIM), to target the metastatic phenotype of thyroid cancer cells through a functional estrogen receptor.

METHODOLOGY/PRINCIPAL FINDINGS

Thyroid cancer cell lines were treated with estrogen and/or DIM and subjected to in vitro adhesion, migration and invasion assays to investigate the anti-metastatic and anti-estrogenic effects of DIM. We observed that DIM inhibits estrogen mediated increase in thyroid cell migration, adhesion and invasion, which is also supported by ER-α downregulation (siRNA) studies. Western blot and zymography analyses provided direct evidence for this DIM mediated inhibition of E(2) enhanced metastasis associated events by virtue of targeting essential proteolytic enzymes, namely MMP-2 and MMP-9.

CONCLUSION/SIGNIFICANCE

Our data reports for the first time that DIM displays anti-estrogenic like activity by inhibiting estradiol enhanced thyroid cancer cell proliferation and in vitro metastasis associated events, namely adhesion, migration and invasion. Most significantly, MMP-2 and MMP-9, which are known to promote and enhance metastasis, were determined to be targets of DIM. This anti-estrogen like property of DIM may lead to the development of a novel preventive and/or therapeutic dietary supplement for thyroid cancer patients by targeting progression of the disease.

GMI, a Ganoderma immunomodulatory protein, down-regulates tumor necrosis factor α-induced expression of matrix metalloproteinase 9 via NF-κB pathway in human alveolar epithelial A549 cells

Matrix metalloproteinase 9 (MMP-9) has been implicated in airway injury in chronic obstructive pulmonary disease (COPD), lung inflammation, and lung cancer and plays a major role in tumor necrosis factor-α (TNF-α)-stimulated tumor invasion and lung inflammation. MMP-9 activity is promoted by the pro-inflammatory cytokine TNF-α. GMI, cloned from Ganoderma microsporum and purified, is one of the recombinant fungal immunomodulatory proteins. To understand the molecular mechanisms involved in the suppression of TNF-α-mediated tumor invasion and inflammation, GMI modulation of this pathway was investigated in human alveolar epithelial A549 cells in this study. GMI exhibited an inhibitory effect on TNF-α-induced invasion, with GMI treatment and TNF-α exposure presenting the most anti-invasive properties on Boyden chamber assay. GMI reduced TNF-α-induced MMP-9 activities on gelatin zymography assay through inhibition of MMP-9 transcriptional activity. RT-PCR and MMP-9 promoter luciferase analysis revealed that GMI inhibits the transcription of MMP-9 mRNA. Moreover, in vitro and in vivo binding experiments, an electrophoretic mobility shift assay (EMSA), and chromatin immunoprecipitation assay (ChIP) demonstrated that GMI suppresses DNA binding of nuclear factor (NF)-κB transcription factors to MMP-9 promoter. Western blot analysis indicated that GMI blocks the phosphorylation and degradation of IκBα, which in turn leads to suppression of the phosphorylation and nuclear translocation of p65. Thus, overall, our results indicated that GMI mediates antitumor invasion and anti-inflammatory effects through modulation of NF-κB/MMP-9 pathways.

Novel targets for prostate cancer chemoprevention

Among many endocrine-related cancers, prostate cancer (PCa) is the most frequent male malignancy, and it is the second most common cause of cancer-related death in men in the United States. Therefore, this review focuses on summarizing the knowledge of molecular signaling pathways in PCa because, in order to better design new preventive strategies for the fight against PCa, documentation of the knowledge on the pathogenesis of PCa at the molecular level is very important. Cancer cells are known to have alterations in multiple cellular signaling pathways; indeed, the development and the progression of PCa are known to be caused by the deregulation of several selective signaling pathways such as the androgen receptor, Akt, nuclear factor-kappaB, Wnt, Hedgehog, and Notch. Therefore, strategies targeting these important pathways and their upstream and downstream signaling could be promising for the prevention of PCa progression. In this review, we summarize the current knowledge regarding the alterations in cell signaling pathways during the development and progression of PCa, and document compelling evidence showing that these are the targets of several natural agents against PCa progression and its metastases.

Epithelial to mesenchymal transition is mechanistically linked with stem cell signatures in prostate cancer cells

BACKGROUND

Current management of patients diagnosed with prostate cancer (PCa) is very effective; however, tumor recurrence with Castrate Resistant Prostate Cancer (CRPC) and subsequent metastasis lead to poor survival outcome, suggesting that there is a dire need for novel mechanistic understanding of tumor recurrence, which would be critical for designing novel therapies. The recurrence and the metastasis of PCa are tightly linked with the biology of prostate cancer stem cells or cancer-initiating cells that is reminiscent of the acquisition of Epithelial to Mesenchymal Transition (EMT) phenotype. Increasing evidence suggests that EMT-type cells share many biological characteristics with cancer stem-like cells.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we found that PCa cells with EMT phenotype displayed stem-like cell features characterized by increased expression of Sox2, Nanog, Oct4, Lin28B and/or Notch1, consistent with enhanced clonogenic and sphere (prostasphere)-forming ability and tumorigenecity in mice, which was associated with decreased expression of miR-200 and/or let-7 family. Reversal of EMT by re-expression of miR-200 inhibited prostasphere-forming ability of EMT-type cells and reduced the expression of Notch1 and Lin28B. Down-regulation of Lin28B increased let-7 expression, which was consistent with repressed self-renewal capability.

CONCLUSIONS/SIGNIFICANCE

These results suggest that miR-200 played a pivotal role in linking the characteristics of cancer stem-like cells with EMT-like cell signatures in PCa. Selective elimination of cancer stem-like cells by reversing the EMT phenotype to Mesenchymal-Epithelial Transition (MET) phenotype using novel agents would be useful for the prevention of tumor recurrence especially by eliminating those cells that are the "Root Cause" of tumor development and recurrence.

Activation of checkpoint kinase 2 by 3,3'-diindolylmethane is required for causing G2/M cell cycle arrest in human ovarian cancer cells

We evaluated the effect of 3,3'-diindolylmethane (DIM) in ovarian cancer cells. DIM treatment inhibited the growth of SKOV-3, TOV-21G, and OVCAR-3 ovarian cancer cells in both a dose- and time-dependent manner with effective concentrations ranging from 40 to 100 muM. Growth-inhibitory effects of DIM were mediated by cell cycle arrest in G(2)/M phase in all the three cell lines. G(2)/M arrest was associated with DNA damage as indicated by phosphorylation of H(2)A.X at Ser139 and activation of checkpoint kinase 2 (Chk2) in all the three cell lines. Other G(2)/M regulatory molecules such as Cdc25C, Cdk1, cyclin B1 were down-regulated by DIM. Cycloheximide or Chk2 inhibitor pretreatment abrogated not only activation of Chk2 but also G(2)/M arrest and apoptosis mediated by DIM. To further establish the involvement of Chk2 in DIM-mediated G(2)/M arrest, cells were transfected with dominant-negative Chk2 (DN-Chk2). Blocking Chk2 activation by DN-Chk2 completely protected cells from DIM-mediated G(2)/M arrest. These results were further confirmed in Chk2 knockout DT40 lymphoma cells, in which DIM failed to cause cell cycle arrest. These results clearly indicate the requirement of Chk2 activation to cause G(2)/M arrest by DIM in ovarian cancer cells. Moreover, blocking Chk2 activation also abrogates the apoptosis-inducing effects of DIM. Furthermore, our results show that DIM treatment cause ROS generation. Blocking ROS generation by N-acetyl cysteine protects the cells from DIM-mediated G(2)/M arrest and apoptosis. Our results establish Chk2 as a potent molecular target of DIM in ovarian cancer cells and provide the rationale for further clinical investigation of DIM.

Extracellular protease ADAMTS9 suppresses esophageal and nasopharyngeal carcinoma tumor formation by inhibiting angiogenesis

ADAMTS metalloprotease family member ADAMTS9 maps to 3p14.2 and shows significant associations with the aerodigestive tract cancers esophageal squamous cell carcinoma (ESCC) and nasopharyngeal carcinoma (NPC). However, the functional impact of ADAMTS9 on cancer development has not been explored. In this study, we evaluated the hypothesized antiangiogenic and tumor-suppressive functions of ADAMTS9 in ESCC and NPC, in stringent tumorigenicity and Matrigel plug angiogenesis assays. ADAMTS9 activation suppressed tumor formation in nude mice. Conversely, knockdown of ADAMTS9 resulted in clones reverting to the tumorigenic phenotype of parental cells. In vivo angiogenesis assays revealed a reduction in microvessel numbers in gel plugs injected with tumor-suppressive cell transfectants. Similarly, conditioned medium from cell transfectants dramatically reduced the tube-forming capacity of human umbilical vein endothelial cells. These activities were associated with a reduction in expression levels of the proangiogenic factors MMP9 and VEGFA, which were consistently reduced in ADAMTS9 transfectants derived from both cancers. Taken together, our results indicate that ADAMTS9 contributes an important function in the tumor microenvironment that acts to inhibit angiogenesis and tumor growth in both ESCC and NPC.

Intraocular matrix metalloproteinase 2 and 9 in patients with diabetes mellitus with and without diabetic retinopathy

INTRODUCTION

We aimed to investigate activities of metalloproteinases 2 (MMP-2) and MMP-9 in aqueous humour of patients with diabetes mellitus with various stages of diabetic retinopathy.

MATERIAL AND METHODS

We included 36 samples of aqueous humour of patients suffering from diabetes mellitus, undergoing routine cataract surgery. Seven of them suffered from proliferative diabetic retinopathy (PDR), 3 had diabetic maculopathy and the remaining 26 had background or minimal background retinopathy only. Metalloproteinases 2 and MMP-9 activities in aqueous humour were measured by gelatin zymography combined with the densitometric imaging system. Total protein content in aqueous humour samples was also assessed.

RESULTS

Metalloproteinases 2 activities were present in almost all samples of aqueous humour (32 of 36) and were 2.6-fold higher in patients who suffered from diabetic ocular complications (p < 0.0001). Activities of MMP-2 correlated well with the duration of the disease (correlation = 0.37, p = 0.03) and tended to correlate with total protein levels in aqueous humour (correlation = 0.43, p = 0.06). Metalloproteinases 9 activities were observed only in 2 of 7 patients with proliferative diabetic disease and the enzyme was absent from aqueous humour samples of patients without proliferative retinopathy.

CONCLUSIONS

Increased activities of MMP-2 in aqueous humour of patients with PDR may be related to the disease process and support the hypothesis that MMP-2 may be of particular importance in diabetic retinal neovascularization. MMP-9 may be activated at a certain disease stage only.

ProstaCaid Induces G2/M Cell Cycle Arrest and Apoptosis in Human and Mouse Androgen-Dependent and-Independent Prostate Cancer Cells

The anticancer effects of ProstaCaid, a novel integrative blend of vitamins, minerals, multiherb extracts, and derivatives, were tested in human and mouse androgen—dependent (AD) and —independent (AI) prostate cancer cell lines. ProstaCaid shows growth inhibitory effects on both human and mouse AD prostate cancer cells (LNCaP and CASP 2.1) and AI prostate cancer cells (PC3 and CASP 1.1) in a dose-/time-dependent manner. Consistently, long-term treatment with ProstaCaid also reduced colony formation capacities of prostate cancer cells. Flow cytometry assays revealed that ProstaCaid induces G2/M arrest and apoptosis in LNCaP and PC3 cells after 72 hours of treatment. Immunoblotting assay demonstrated that 25 µg/mL of ProstaCaid treatment resulted in (1) the reduction of cyclin D1, cyclin B1, and Cdc2 expression in a time-dependent way; (2) increase in p21WAF1/Cip1 as early as 12 hours after the treatments in PC3 cells and reduction to base line at the 72-hour time point; and (3) repression of Bcl-2, BclxL, and induction of Bim as well as the cleavages of caspase-3 and poly(ADP-ribose) polymerase (PARP) at 72 hours of treatment, suggesting caspase-3-dependent apoptosis. Moreover, ProstaCaid suppressed activation of AKT and MAPK signaling pathways in PC3 and LNCaP cells by reducing phosphorylation levels of AKT, its downstream target S6 ribosomal protein and GSK3β, and ERK1/2, respectively. In summary, these findings strongly suggest that ProstaCaid may be a potential chemopreventive and therapeutic agent for both AD and, more importantly, AI prostate cancer.

PAR-4 as a possible new target for pancreatic cancer therapy

IMPORTANCE OF THE FIELD

Pancreatic cancer (PC) is a deadly disease that is intractable to currently available treatment regimens. Although well described in different tumors types, the importance of apoptosis inducer prostate apoptosis response-4 (Par-4) in PC has not been appreciated. PC is an oncogenic kras driven disease, which is known to downregulate Par-4. Therefore, this review highlights its significance and builds a strong case supporting the role of Par-4 as a possible therapeutic target in PC.

AREAS COVERED IN THIS REVIEW

Literature-based evidence spanning the last 15 years on Par-4 and its significance in PC.

WHAT THE READER WILL GAIN

This review provides comprehensive knowledge of the significance of Par-4 and its association with kras status in PC, along with the crosstalk with crucial resistance and survival molecules NF-kappaB and Bcl-2 that ultimately are responsible for the overall poor outcome of different therapeutic approaches in this disease.

TAKE HOME MESSAGE

Par-4 holds promise as a potential therapeutic target that can be induced by chemopreventive agents and small-molecule inhibitors either alone or in combination with standard chemotherapeutics leading to selective apoptosis in PC cells. It also acts as a chemosensitizer and therefore warrants further clinical investigations in this disease.

The in vitro and in vivo anti-metastatic efficacy of oxythiamine and the possible mechanisms of action

This study examined the anti-metastatic effects of oxythiamine (OT) both in cell culture and in vivo. Cell culture results revealed that OT (0-20 microM) significantly inhibited the invasion and migration (IC(50) = 8.75 microM) of Lewis lung carcinoma (LLC) cells. These effects of OT were accompanied by the inhibition of metalloproteinases-2 and -9 (MMP-2, MMP-9), urokinase-type plasminogen activator (uPA) activities and by the increases in protein expression of tissue inhibitors of metalloproteinases-1 and -2 (TIMP-1, TIMP-2). We then implanted (s.c.) C57BL/6 mice with LLC cells and supplemented the mice with a low- or a high-dose of OT (250 or 500 mg/kg BW) daily for 5 wk. During the 5-wk period, OT supplementation decreased plasma MMP-2 activity in a dose-dependent manner, and this effect was significant after 4 wk of tumor cell implantation. Tumor metastasis was found to confine to the lungs of mice injected with the tumor cells. High-OT supplementation strongly lowered the number and area of tumors and inhibited protein expression of MMP-2 and MMP-9 in the lungs. In addition, high-OT supplementation markedly decreased the extent of proliferating cell nuclear antigen (PCNA) staining in the lungs. By contrast, OT supplementation increased TIMP-1 and -2 protein expression in the lungs. These results demonstrate that OT supplementation attenuates tumor cell metastasis, possibly via inhibition of protein expression of MMPs, extent of PCNA staining and via increase of proteins expression of TIMPs.

Blueberry phytochemicals inhibit growth and metastatic potential of MDA-MB-231 breast cancer cells through modulation of the phosphatidylinositol 3-kinase pathway

Dietary phytochemicals are known to exhibit a variety of anticarcinogenic properties. This study investigated the chemopreventive activity of blueberry extract in triple-negative breast cancer cell lines in vitro and in vivo. Blueberry decreased cell proliferation in HCC38, HCC1937, and MDA-MB-231 cells with no effect on the nontumorigenic MCF-10A cell line. Decreased metastatic potential of MDA-MB-231 cells by blueberry was shown through inhibition of cell motility using wound-healing assays and migration through a polyethylene terephthalate membrane. Blueberry treatment decreased the activity of matrix metalloproteinase-9 and the secretion of urokinase-type plasminogen activator while increasing tissue inhibitor of metalloproteinase-1 and plasminogen activator inhibitor-1 secretion in MDA-MB-231 conditioned medium as shown by Western blotting. Cell signaling pathways that control the expression/activation of these processes were investigated via Western blotting and reporter gene assay. Treatment with blueberry decreased phosphatidylinositol 3-kinase (PI3K)/AKT and NFkappaB activation in MDA-MB-231 cells, where protein kinase C and extracellular signal-regulated kinase (ERK) were not affected. In vivo, the efficacy of blueberry to inhibit triple-negative breast tumor growth was evaluated using the MDA-MB-231 xenograft model. Tumor weight and proliferation (Ki-67 expression) were decreased in blueberry-treated mice, where apoptosis (caspase-3 expression) was increased compared with controls. Immunohistochemical analysis of tumors from blueberry-fed mice showed decreased activation of AKT and p65 NFkappaB signaling proteins with no effect on the phosphorylation of ERK. These data illustrate the inhibitory effect of blueberry phytochemicals on the growth and metastatic potential of MDA-MB-231 cells through modulation of the PI3K/AKT/NFkappaB pathway.

Down-regulation of uPA and uPAR by 3,3'-diindolylmethane contributes to the inhibition of cell growth and migration of breast cancer cells

3,3'-Diindolylmethane (DIM) is a known anti-tumor agent against breast and other cancers; however, its exact mechanism of action remains unclear. The urokinase plasminogen activator (uPA) and its receptor (uPAR) system are involved in the degradation of basement membrane and extracellular matrix, leading to tumor cell invasion and metastasis. Since uPA-uPAR system is highly activated in aggressive breast cancer, we hypothesized that the biological activity of B-DIM could be mediated via inactivation of uPA-uPAR system. We found that B-DIM treatment as well as silencing of uPA-uPAR led to the inhibition of cell growth and motility of MDA-MB-231 cells, which was in part due to inhibition of VEGF and MMP-9. Moreover, silencing of uPA-uPAR led to decreased sensitivity of these cells to B-DIM indicating an important role of uPA-uPAR in B-DIM-mediated inhibition of cell growth and migration. We also found similar effects of B-DIM on MCF-7, cells expressing low levels of uPA-uPAR, which was due to direct down-regulation of MMP-9 and VEGF, independent of uPA-uPAR system. Interestingly, over-expression of uPA-uPAR in MCF-7 cells attenuated the inhibitory effects of B-DIM. Our results, therefore, suggest that B-DIM down-regulates uPA-uPAR in aggressive breast cancers but in the absence of uPA-uPAR, B-DIM can directly inhibit VEGF and MMP-9 leading to the inhibition of cell growth and migration of breast cancer cells.

miR-146a suppresses invasion of pancreatic cancer cells

The aggressive course of pancreatic cancer is believed to reflect its unusually invasive and metastatic nature, which is associated with epidermal growth factor receptor (EGFR) overexpression and NF-kappaB activation. MicroRNAs (miRNA) have been implicated in the regulation of various pathobiological processes in cancer, including metastasis in pancreatic cancer and in other human malignancies. In this study, we report lower expression of miR-146a in pancreatic cancer cells compared with normal human pancreatic duct epithelial cells. Reexpression of miR-146a inhibited the invasive capacity of pancreatic cancer cells with concomitant downregulation of EGFR and the NF-kappaB regulatory kinase interleukin 1 receptor-associated kinase 1 (IRAK-1). Cellular mechanism studies revealed crosstalk between EGFR, IRAK-1, IkappaBalpha, NF-kappaB, and MTA-2, a transcription factor that regulates metastasis. Treatment of pancreatic cancer cells with the natural products 3,3'-diinodolylmethane (DIM) or isoflavone, which increased miR-146a expression, caused a downregulation of EGFR, MTA-2, IRAK-1, and NF-kappaB, resulting in an inhibition of pancreatic cancer cell invasion. Our findings reveal DIM and isoflavone as nontoxic activators of a miRNA that can block pancreatic cancer cell invasion and metastasis, offering starting points to design novel anticancer agents.

miR-200 regulates PDGF-D-mediated epithelial-mesenchymal transition, adhesion, and invasion of prostate cancer cells

MicroRNAs have been implicated in tumor progression. Recent studies have shown that the miR-200 family regulates epithelial-mesenchymal transition (EMT) by targeting zinc-finger E-box binding homeobox 1 (ZEB1) and ZEB2. Emerging evidence from our laboratory and others suggests that the processes of EMT can be triggered by various growth factors, such as transforming growth factor beta and platelet-derived growth factor-D (PDGF-D). Moreover, we recently reported that overexpression of PDGF-D in prostate cancer cells (PC3 PDGF-D cells) leads to the acquisition of the EMT phenotype, and this model offers an opportunity for investigating the molecular interplay between PDGF-D signaling and EMT. Here, we report, for the first time, significant downregulation of the miR-200 family in PC3 PDGF-D cells as well as in PC3 cells exposed to purified active PDGF-D protein, resulting in the upregulation of ZEB1, ZEB2, and Snail2 expression. Interestingly, re-expression of miR-200b in PC3 PDGF-D cells led to reversal of the EMT phenotype, which was associated with the downregulation of ZEB1, ZEB2, and Snail2 expression, and these results were consistent with greater expression levels of epithelial markers. Moreover, transfection of PC3 PDGF-D cells with miR-200b inhibited cell migration and invasion, with concomitant repression of cell adhesion to the culture surface and cell detachment. From these results, we conclude that PDGF-D-induced acquisition of the EMT phenotype in PC3 cells is, in part, a result of repression of miR-200 and that any novel strategy by which miR-200 could be upregulated would become a promising approach for the treatment of invasive prostate cancer.

Chemopreventive agent 3,3'-diindolylmethane selectively induces proteasomal degradation of class I histone deacetylases

3,3'-Diindolylmethane (DIM) is an anticancer agent that induces cell cycle arrest and apoptosis through unknown mechanisms. Here, we report that DIM can selectively induce proteasome-mediated degradation of class I histone deacetylases (HDAC1, HDAC2, HDAC3, and HDAC8) without affecting the class II HDAC proteins. DIM induced downregulation of class I HDACs in human colon cancer cells in vitro and in vivo in tumor xenografts. HDAC depletion relieved HDAC-mediated transcriptional inhibition of the cyclin-dependent kinase inhibitors p21WAF1 and p27KIP2, significantly increasing their expression and triggering cell cycle arrest in the G(2) phase of the cell cycle. Additionally, HDAC depletion was associated with an induction of DNA damage that triggered apoptosis. Our findings indicate that DIM acts to selectively target the degradation of class I HDACs.

Antiangiogenic effects of indole-3-carbinol and 3,3'-diindolylmethane are associated with their differential regulation of ERK1/2 and Akt in tube-forming HUVEC

We previously reported that indole-3-carbinol (I3C), found in cruciferous vegetables, suppresses angiogenesis in vivo and in vitro. However, the underlying molecular mechanisms still remain unclear. Antiangiogenic effects of its major metabolite, 3,3'-diindolylmethane (DIM), also have not been fully elucidated. In this study, we investigated the effects of these indoles on angiogenesis and tested a hypothesis that I3C and DIM inhibit angiogenesis and induce apoptosis by affecting angiogenic signal transduction in human umbilical vein endothelial cells (HUVEC). We found that I3C and DIM at 25 micromol/L significantly inhibited tube formation and only DIM induced a significant increase in apoptosis in tube-forming HUVEC. DIM showed a stronger antiangiogenic activity than I3C. At the molecular level, I3C and DIM markedly inactivated extracellular signal-regulated kinase 1/2 (ERK1/2) and the inhibitory effect of DIM was significantly greater than that of I3C. DIM treatment also resulted in activation of the caspase pathway and inactivation of Akt, whereas I3C did not affect them. These results indicate that I3C and DIM had a differential potential in the regulation of the 2 principal survival signals, ERK1/2 and Akt, in endothelial cells. We also demonstrated that pharmacological inhibition of ERK1/2 and/or Akt was enough to inhibit tube formation and induce caspase-dependent apoptosis in tube-forming HUVEC. We conclude that both I3C and DIM inhibit angiogenesis at least in part via inactivation of ERK1/2 and that inactivation of Akt by DIM is responsible for its stronger antiangiogenic effects than those of I3C.

Oral administration of 3,3'-diindolylmethane inhibits lung metastasis of 4T1 murine mammary carcinoma cells in BALB/c mice

3,3'-diindolylmethane (DIM) is the major in vivo product of the acid-catalyzed oligomerization of indole-3-carbinol present in cruciferous vegetables, and it has been shown to exhibit anticancer properties. In this study, we assessed the effects of DIM on the metastasis of 4T1 mouse mammary carcinoma cells. In vitro culture studies showed that DIM dose-dependently inhibited the migration, invasion, and adhesion of 4T1 cells at concentrations of 0-10 micromol/L without attendant changes in cell viability. In an in vivo lung metastasis model, 4T1 cells (2 x 10(5) cells/mouse) were injected into the tail veins of syngeneic female BALB/c mice. Beginning on the second day, the mice were subjected to gavage with 0-10 mg DIM/(kg body weight x d) for 13 d. Oral DIM administration resulted in a marked reduction in the number of pulmonary tumor nodules. DIM treatment significantly reduced the levels of matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1, and vascular cell adhesion molecule (VCAM)-1 and increased TIMP-2 levels in the sera and lungs of mice injected with 4T1 cells. Additionally, DIM treatment reduced the serum concentrations of interleukin (IL)-1beta, IL-6 and tumor necrosis factor (TNF)alpha. We have demonstrated that DIM profoundly inhibits the lung metastasis of 4T1 cells, which was accompanied by reduced levels of MMP, adhesion molecules, and proinflammatory cytokines. These results indicate that DIM has potential as an antimetastatic agent for the treatment of breast cancer.

Harnessing the fruits of nature for the development of multi-targeted cancer therapeutics

Cancer cells exhibit deregulation in multiple cellular signaling pathways. Therefore, treatments using specific agents that target only one pathway usually fail in cancer therapy. The combination treatments using chemotherapeutic agents with distinct molecular mechanisms are considered more promising for higher efficacy; however, using multiple agents contributes to added toxicity. Emerging evidence has shown that some "natural products" such as isoflavones, indole-3-carbinol (I3C) and its in vivo dimeric product 3,3'-diindolylmethane (DIM), and curcumin among many others, have growth inhibitory and apoptosis inducing effects on human and animal cancer cells mediated by targeting multiple cellular signaling pathways in vitro without causing unwanted toxicity in normal cells. Therefore, these non-toxic "natural products" from natural resources could be useful in combination with conventional chemotherapeutic agents for the treatment of human malignancies with lower toxicity and higher efficacy. In fact, recently increasing evidence from pre-clinical in vivo studies and clinical trials have shown some success in support of the use of rational design of multi-targeted therapies for the treatment of cancers using conventional chemotherapeutic agents in combination with "natural products". These studies have provided promising results and further opened-up newer avenues for cancer therapy. In this review article, we have succinctly summarized the known effects of "natural products" especially by focusing on isoflavones, indole-3-carbinol (I3C) and its in vivo dimeric product 3,3'-diindolylmethane (DIM), and curcumin, and provided a comprehensive view on the molecular mechanisms underlying the principle of cancer therapy using combination of "natural products" with conventional therapeutics.

Anti-angiogenic activity of triptolide in anaplastic thyroid carcinoma is mediated by targeting vascular endothelial and tumor cells

Triptolide is confirmed to suppress angiogenesis of anaplastic thyroid carcinoma. Here we further expound the precise mechanism involved in this activity. Triptolide downregulated nuclear factor kappa B (NF-kappaB) pathway and its targeting genes associated with endothelial cell mobilization in human umbilical vein endothelial cells (HUVECs) and impaired VEGF expression in thyroid carcinoma TA-K cells. Furthermore, both triptolide and the conditioned medium from triptolide-treated TA-K cells (CMT) significantly attenuated proliferation, migration and tube formation of HUVECs. In vivo, triptolide inhibited TA-K cell-induced tumor growth, vascular formation and VEGF expression. Our data establish that triptolide inhibits tumor angiogenesis by the dual action on vascular endothelial cells and tumor cells, thus providing a novel and overall explanation for the anti-angiogenesis action of triptolide. The multicellular targets emphasize triptolide as a high-performance and potential angiogenesis inhibitor.

FoxM1 down-regulation leads to inhibition of proliferation, migration and invasion of breast cancer cells through the modulation of extra-cellular matrix degrading factors

Forkhead box M1 (FoxM1) transcription factor is known to play important role in human cancers which, in part, is mediated by its ability to modulate cell cycle regulatory proteins as well as genes involved in cell proliferation and differentiation. In breast cancer, FoxM1 down-regulation is increasingly being recognized as an important mechanism for the targeted activity of anti-cancer agents. However, the mechanistic insight in support of the role of FoxM1 in aggressive breast cancer is poorly understood. We have tested the biological consequence of FoxM1 down-regulation and up-regulation in breast cancer cell lines and found that the down-regulation of FoxM1 in MDA-MB-231 and SUM149 cells by siRNA approach inhibited cell growth, clonogenicity, migration, and invasion. We also found decreased expression of CDK2 and E2F1 with concomitant increase in p21 and p27 proteins, suggesting an important role of FoxM1 in cell cycle progression. In contrast, over-expression of FoxM1 by cDNA transfection, in breast cancer cells (SUM102 and SKBR3) expressing low levels of FoxM1, resulted in increased cell proliferation, migration, and invasion. Moreover, down-regulation of FoxM1 inhibited the expression of many factors that are involved in the degradation of extra cellular matrix and angiogenesis such as uPA, uPAR, MMP-2, MMP-9, and vascular endothelial growth factor (VEGF) as well as inhibited the activity of MMP-9 and VEGF. Interestingly, over-expression of uPA by cDNA transfection abrogated the cellular effects that were observed by the down-regulation of FoxM1. Taken together, these results suggest the potential application of FoxM1 down-regulation as a novel approach for the treatment of aggressive breast cancer.

Pleiotropic roles of matrix metalloproteinases in tumor angiogenesis: contrasting, overlapping and compensatory functions

A number of extensive reviews are available discussing the roles of MMPs in various aspects of cancer progression from benign tumor formation to overt cancer present with deadly metastases. This review will focus specifically on the evidence functionally linking the MMPs and tumor-induced angiogenesis in various in vivo models. Emphasis has been placed on the cellular origin of the MMPs in tumor tissue, the requirement of proMMP activation and the resulting proteolytic activity for the induction and progression of tumor angiogenesis, and the pleiotropic roles for some of the MMPs. The functional mechanisms of the angiogenic MMPs are discussed as well as their catalytic detection in complex biological systems. In addition, the contribution of active MMPs to metastatic spread and establishment of secondary metastasis will be discussed in view of the findings indicating that MMPs are involved in the preparation of pre-metastatic niches. Finally, the most recent evidence, indicating the pro-metastatic consequences of anti-angiogenic therapies employing MMP inhibitors will be presented as examples highlighting possible outcomes of interfering with the pleiotropic nature of the MMP functionality.

Up-regulation of miR-200 and let-7 by natural agents leads to the reversal of epithelial-to-mesenchymal transition in gemcitabine-resistant pancreatic cancer cells

Pancreatic cancer is the fourth most common cause of cancer death in the United States, and the aggressiveness of pancreatic cancer is in part due to its intrinsic and extrinsic drug resistance characteristics, which are also associated with the acquisition of epithelial-to-mesenchymal transition (EMT). Emerging evidence also suggests that the processes of EMT are regulated by the expression status of many microRNAs (miRNA), which are believed to function as key regulators of various biological and pathologic processes during tumor development and progression. In the present study, we compared the expression of miRNAs between gemcitabine-sensitive and gemcitabine-resistant pancreatic cancer cells and investigated whether the treatment of cells with "natural agents" [3,3'-diindolylmethane (DIM) or isoflavone] could affect the expression of miRNAs. We found that the expression of miR-200b, miR-200c, let-7b, let-7c, let-7d, and let-7e was significantly down-regulated in gemcitabine-resistant cells, which showed EMT characteristics such as elongated fibroblastoid morphology, lower expression of epithelial marker E-cadherin, and higher expression of mesenchymal markers such as vimentin and ZEB1. Moreover, we found that reexpression of miR-200 by transfection studies or treatment of gemcitabine-resistant cells with either DIM or isoflavone resulted in the down-regulation of ZEB1, slug, and vimentin, which was consistent with morphologic reversal of EMT phenotype leading to epithelial morphology. These results provide experimental evidence, for the first time, that DIM and isoflavone could function as miRNA regulators leading to the reversal of EMT phenotype, which is likely to be important for designing novel therapies for pancreatic cancer.

Loss of inhibitor of growth (ING-4) is implicated in the pathogenesis and progression of human astrocytomas

Inhibitor of growth 4 (ING-4) is a tumor suppressor gene that interacts with nuclear factor-kappaB (NF-kappaB) and represses its transcriptional activity. Several lines of evidence suggest that the tumor suppressor gene ING-4, the transcription factor NF-kappaB and its target genes matrix metalloproteases MMP-2, MMP-9 and urokinase plasminogen activator (u-PA) are critically involved in tumor invasion. The aim of the present study was to investigate immunohistochemically the expression pattern of ING-4, NF-kappaB and the NF-kappaB downstream targets MMP-2, MMP-9 and u-PA in human astrocytomas from 101 patients. We found that ING-4 expression was significantly decreased in astrocytomas, and ING-4 loss was associated with tumor grade progression. Expression of p65, a NF-kappaB subunit, was significantly higher in grade IV than in grade III and grade I/II tumors, and a statistical significant negative correlation between expression of ING-4 and expression of nuclear p65 was noticed. MMP-9, MMP-2 and u-PA were overexpressed in human astrocytomas. Of note, astrocytomas of advanced histologic grades (grade III, IV) displayed significantly higher expression levels of these proteins compared to tumors of lower grades (grade I, II). Collectively, our data suggest an essential role for ING-4 in human astrocytoma development and progression possibly through regulation of the NF-kappaB-dependent expression of genes involved in tumor invasion.

3,3'-diindolylmethane attenuates colonic inflammation and tumorigenesis in mice

BACKGROUND

3,3-Diindolylmethane (DIM) is a major in vivo product of acid-catalyzed oligomerization of indole-3-carbinol (I3C) derived from Brassica food plants. Although DIM is known as a chemopreventive and chemotherapeutic phytochemical, the effects of DIM on inflammation in vivo are still unknown. In the present study we investigated the antiinflammatory effects of DIM on experimental colitis and colitis-associated colorectal carcinogenesis.

METHODS

To determine if DIM has an antiinflammatory effect in vivo, we examined the therapeutic effects of DIM in dextran sodium sulfate (DSS)-induced experimental colitis and colitis-associated colon carcinogenesis induced by azoxymethane (AOM)/DSS in BALB/c mice.

RESULTS

Treatment with DIM significantly attenuated loss of body weight, shortening of the colon, and severe clinical signs in a colitis model. This was associated with a remarkable amelioration of the disruption of the colonic architecture and a significant reduction in colonic myeloperoxidase activity and production of prostaglandin E(2), nitric oxide, and proinflammatory cytokines. Further, DIM administration dramatically decreased the number of colon tumors in AOM/DSS mice.

CONCLUSIONS

These results suggest that DIM-mediated antiinflammatory action at colorectal sites may be therapeutic in the setting of inflammatory bowel disease and colitis-associated colon cancer.

Inhibition of vinyl carbamate-induced pulmonary adenocarcinoma by indole-3-carbinol and myo-inositol in A/J mice

In previous studies, we reported that indole-3-carbinol (I3C) and myo-inositol (MI) inhibit lung adenoma induced by tobacco smoke carcinogens in A/J mice. In this paper, we extended our work and examined the effects of I3C (70 or 30 micromol/g diet) and MI (56 micromol/g diet) against vinyl carbamate (VC)-induced lung adenocarcinoma by administering the agents from 1 week after the second of two injections of VC until termination of the study at week 18. The higher dose of I3C decreased multiplicities of tumors on the surface of the lung (26%, P = 0.0005), carcinoma incidence (38%), multiplicity (67%, P < 0.0001) and size (complete abolition of carcinoma with an area of >1.0 cm(2)) as well as adenoma with cellular pleomorphism (46%, P < 0.0001). The lower dose of I3C was less effective. MI decreased multiplicities of pulmonary surface tumors (20%, P = 0.0005), adenoma with cellular pleomorphism (40%, P < 0.0001) and lung adenoma (52%, P < 0.0001) and the proportion of the biggest carcinoma (carcinoma with an area of >1.0 cm(2), P < 0.05). Immunoblot analyses of lung tissues for potential target identification showed that I3C (70 micromol/g diet) inhibits IkappaBalpha degradation, nuclear factor-kappaB activation, expression of cyclooxygenase-2, phospho-Akt and fatty acid synthase (FAS) and activates caspase-3 and poly ADP ribose polymerase cleavage. The effect of MI was limited to inhibition of phospho-Akt and FAS expression. Our data show that I3C and MI inhibit lung carcinoma and provide a basis for future evaluation of these compounds in clinical trials as chemopreventive agents for current and former smokers.

Neutrophil MMP-9 proenzyme, unencumbered by TIMP-1, undergoes efficient activation in vivo and catalytically induces angiogenesis via a basic fibroblast growth factor (FGF-2)/FGFR-2 pathway

The structural and catalytic requirements for neutrophil MMP-9 proenzyme (proMMP-9) to induce angiogenesis were investigated using a quantitative angiogenesis model based on grafting of collagen onplants onto the chorioallantoic membrane of chick embryos. Both physiological activation of neutrophil proMMP-9 and proteolytic activity of the generated MMP-9 enzyme were critically dependent on the tissue inhibitor of metalloproteinase (TIMP)-free status of the zymogen. The presence of an intact active site and hemopexin domain were required for full angiogenesis-inducing activity of the MMP-9 enzyme. Timed additions of TIMP-1 to the onplants containing TIMP-free neutrophil proMMP-9 indicated that in vivo activation of the zymogen occurred during the first 24 h after grafting. Within the onplant tissue, MMP-9 activation was accompanied by proteolytic modifications of fibrillar collagen and an influx of host proteins, the rate of which depended on the TIMP-free status of the zymogen. By quantifying the levels of host angiogenic factors, we demonstrated that basic fibroblast growth factor (FGF-2) was a major cytokine becoming bioavailable in the onplant tissue undergoing a neutrophil proMMP-9-mediated angiogenic switch. Inhibition of angiogenesis with specific function-blocking antibodies further indicated an involvement of a FGF-2/FGFR-2 pathway in neutrophil proMMP-9-induced angiogenesis. The enhanced angiogenesis catalyzed by neutrophil MMP-9 appears to evoke also a localized, low threshold level vascular endothelial growth factor (VEGF)/VEGFR-2 pathway, likely functioning in the formation and/or stabilization of blood vessels. That neutrophil proMMP-9, unencumbered by TIMP-1, directly mediates FGF-2-dependent angiogenesis was also demonstrated in our quantitative mouse angiogenesis model employing subcutaneous collagen implants, thus implicating the novel TIMP-free MMP-9/FGF-2/FGFR-2 pathway in proMMP-9-induced angiogenesis in a mammalian setting.

3,3'-Diindolylmethane enhances chemosensitivity of multiple chemotherapeutic agents in pancreatic cancer

Clinical management of pancreatic cancer is a major problem, which is in part due to both de novo and acquired resistance to conventional therapeutics. Here, we present in vitro and in vivo preclinical evidence in support of chemosensitization of pancreatic cancer cells by 3,3-diindolylmethane (DIM), a natural compound that can be easily obtained by consuming cruciferous vegetables. DIM pretreatment of pancreatic cancer cells led to a significantly increased apoptosis (P < 0.01) with suboptimal concentrations of chemotherapeutic agents (cisplatin, gemcitabine, and oxaliplatin) compared with monotherapy. It is known that resistance to chemotherapy in pancreatic cancer is associated with constitutively activated nuclear factor-kappaB (NF-kappaB), which becomes further activated by chemotherapeutic drugs. Our data provide mechanistic evidence for the first time showing that DIM potentiates the killing of pancreatic cancer cells by down-regulation of constitutive as well as drug-induced activation of NF-kappaB and its downstream genes (Bcl-xL, XIAP, cIAP, and survivin). Most importantly, using an orthotopic animal model, we found reduction in tumor size (P < 0.001) when DIM was given in combination with oxaliplatin compared with monotherapy. This was accompanied by loss of phospho-p65 and down-regulation of NF-kappaB activity and its downstream genes (Bcl-xL, survivin, and XIAP), which correlated with reduced cell proliferation (as assessed by Ki-67 immunostaining of tumor specimens) and evidence of apoptosis [as assessed by poly(ADP-ribose) polymerase cleavage and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining]. These results provide strong in vivo evidence in support of our hypothesis that DIM could abrogate chemotherapeutic drug (cisplatin, gemcitabine, and/or oxaliplatin)-induced activation of NF-kappaB, resulting in the chemosensitization of pancreatic tumors to conventional therapeutics.

Inactivation of uPA and its receptor uPAR by 3,3'-diindolylmethane (DIM) leads to the inhibition of prostate cancer cell growth and migration

3,3'-Diindolylmethane (DIM) has been studied for its putative anti-cancer properties, especially against prostate cancer; however, its exact mechanism of action remains unclear. We recently provided preliminary data suggesting down-regulation of uPA during B-DIM (a clinically active DIM)-induced inhibition of invasion and angiogenesis in prostate cancer cells. Since the expression and activation of uPA plays important role in tumorigenicity, and high endogenous levels of uPA and uPAR are found in advanced metastatic cancers, we investigated their role in B-DIM-mediated inhibition of prostate cancer cell growth and motility. Using PC3 cells, we found that B-DIM treatment as well as the silencing of uPA and uPAR by siRNAs led to the inhibition of cell growth and motility. Conversely, over-expression of uPA/uPAR in LNCaP and C4-2B cells resulted in increased cell growth and motility, which was effectively inhibited by B-DIM. Moreover, we found that uPA as well as uPAR induced the production of VEGF and MMP-9, and that the down-regulation of uPA/uPAR by siRNAs or B-DIM treatment resulted in the inhibition of VEGF and MMP-9 secretion which could be responsible for the observed inhibition of cell migration. Interestingly, silencing of uPA/uPAR led to decreased sensitivity to B-DIM indicating important role of uPA/uPAR in B-DIM-mediated regulation of prostate cancer cell growth and migration. Our data suggest that chemopreventive and/or therapeutic activity of B-DIM is in part due to down-regulation of uPA-uPAR leading to reduced production of VEGF/MMP-9 which ultimately leads to the inhibition of cell growth and migration of aggressive prostate cancer cells.

3,3'-diindolylmethane enhances the efficacy of butyrate in colon cancer prevention through down-regulation of survivin

Butyrate is an inhibitor of histone deacetylase (HDAC) and has been extensively evaluated as a chemoprevention agent for colon cancer. We recently showed that mutations in the adenomatous polyposis coli (APC) gene confer resistance to HDAC inhibitor-induced apoptosis in colon cancers. Here, we show that APC mutation rendered colon cancer cells resistant to butyrate-induced apoptosis due to the failure of butyrate to down-regulate survivin in these cells. Another cancer-preventive agent, 3,3'-diindolylmethane (DIM), was identified to be able to down-regulate survivin in colon cancers expressing mutant APC. DIM inhibited survivin mRNA expression and promoted survivin protein degradation through inhibition of p34(cdc2)-cyclin B1-mediated survivin Thr(34) phosphorylation. Pretreatment with DIM enhanced butyrate-induced apoptosis in colon cancer cells expressing mutant APC. DIM/butyrate combination treatment induced the expression of proapoptotic Bax and Bak proteins, triggered Bax dimerization/activation, and caused release of cytochrome c and Smac proteins from mitochondria. Whereas overexpression of survivin blocked DIM/butyrate-induced apoptosis, knocking down of survivin by small interfering RNA increased butyrate-induced apoptosis in colon cancer cells. We further showed that DIM was able to down-regulate survivin and enhance the effects of butyrate in apoptosis induction and prevention of familial adenomatous polyposis in APC(min/+) mice. Thus, the combination of DIM and butyrate is potentially an effective strategy for the prevention of colon cancer.

Penta-O-galloyl-beta-D-glucose suppresses prostate cancer bone metastasis by transcriptionally repressing EGF-induced MMP-9 expression

Prostate carcinoma is the most frequently diagnosed malignancy and the second leading cause of cancer-related death of men in the United States. Epidermal growth factor (EGF) generated from bone tissue contributes to prostate cancer metastasis through stimulating matrix metalloproteinase (MMP) secretions from prostate cancer cells. In this study, in vitro invasion assay was performed by incubating penta-O-galloyl-beta-D-glucose (5GG) at various concentrations with 2 x 10(4) PC-3 cells for 48 h. The anti-invasive and cytotoxic effects of 5GG were found and evaluated on the human androgen-independent prostate cancer PC-3 cell line by MTT assays and Western blot analyses. 5GG inhibited the EGF-induced cell invasiveness and MMP-9 expression in a dose- and time-dependent manner by reducing the MMP-9 transcriptional activity. To explore the mechanisms for the 5GG-mediated regulation of MMP-9, we further examined the effects of 5GG on transcription factors, including NF-kappaB, AP-1, and mitogen-activated protein kinase (MAPK) activities. The results showed that 5GG suppressed the EGF-induced NF-kappaB nuclear translocation and also abrogated the EGF-induced activation of c-jun N-terminal kinase (JNK), an upstream modulator of NF-kappaB. Moreover, we showed that 5GG reduced EGFR expression through the proteasome pathway. These results suggest that 5GG may exert at least part of its anti-invasive effect in androgen-independent prostate cancer by controlling MMP-9 expression through the suppression of the EGFR/JNK pathway. Finally, 5GG suppresses invasion and tumorigenesis in nude mice treatment with intratibia injection of PC-3 cells. These in vitro and in vivo results suggest that 5GG may be a therapeutic candidate for the treatment of advanced prostate cancer.

Radiation-induced HIF-1alpha cell survival pathway is inhibited by soy isoflavones in prostate cancer cells

We previously showed that treatment of prostate cancer cells with soy isoflavones and radiation resulted in greater cell killing in vitro, and caused downregulation of NF-kappaB and APE1/Ref-1. APE1/Ref-1 functions as a redox activator of transcription factors, including NF-kappaB and HIF-1alpha. These molecules are upregulated by radiation and implicated in radioresistance of cancer cells. We extended our studies to investigate the role of HIF-1alpha survival pathway and its upstream Src and STAT3 molecules in isoflavones and radiation interaction. Radiation induced phosphorylation of Src and STAT3 leading to induction of HIF-1alpha. Genistein, daidzein or a mixture of soy isoflavones did not activate this pathway. These data were observed both in PC-3 (AR-) and C4-2B (AR+) androgen-independent cell lines. Pretreatment with isoflavones inhibited Src/STAT3/HIF-1alpha activation by radiation and nuclear translocation of HIF-1alpha. These findings correlated with decreased expression of APE1/Ref-1 and DNA binding activity of HIF-1alpha and NF-kappaB. In APE1/Ref-1 cDNA transfected cells, radiation caused a greater increase in HIF-1alpha and NF-kappaB activities but this effect was inhibited by pretreatment with soy prior to radiation. Transfection experiments indicate that APE1/Ref-1 inhibition by isoflavones impairs the radiation-induced transcription activity of NF-kappaB and HIF-1alpha. This mechanism could result in the inhibition of genes essential for tumor growth and angiogenesis, as demonstrated by inhibition of VEGF production and HUVECs tube formation. Our novel findings suggest that the increased responsiveness to radiation mediated by soy isoflavones could be due to pleiotropic effects of isoflavones blocking cell survival pathways induced by radiation including Src/STAT3/HIF-1alpha, APE1/Ref-1 and NF-kappaB.

Cell cycle-dependent effects of 3,3'-diindolylmethane on proliferation and apoptosis of prostate cancer cells

Epidemiological studies have shown that a diet rich in fruits and cruciferous vegetables is associated with a lower risk of prostate cancer. Indole-3-carbinol (I3C) and its dimeric product 3,3'-diindolylmethane (DIM) have been shown to exhibit anti-tumor activity both in vitro and in vivo. Recently, we have reported that a formulated DIM (B-DIM) induced apoptosis and inhibited growth, angiogenesis, and invasion of prostate cancer cells by regulating Akt, NF-kappaB, VEGF and the androgen receptor (AR) signaling pathway. However, the precise molecular mechanism(s) by which B-DIM inhibits prostate cancer cell growth and induces apoptosis have not been fully elucidated. Most importantly, it is not known how B-DIM affects cell cycle regulators and proteasome activity, which are critically involved in cell growth and apoptosis. In this study, we investigated the effects of B-DIM on proteasome activity and AR transactivation with respect to B-DIM-mediated cell cycle regulation and induction of apoptosis in both androgen-sensitive LNCaP and androgen-insensitive C4-2B prostate cancer cells. We believe that our results show for the first time the cell cycle-dependent effects of B-DIM on proliferation and apoptosis of synchronized prostate cancer cells progressing from G(1) to S phase. B-DIM inhibited this progression by induction of p27(Kip1) and down-regulation of AR. We also show for the first time that B-DIM inhibits proteasome activity in S phase, leading to the inactivation of NF-kappaB signaling and induction of apoptosis in LNCaP and C4-2B cells. These results suggest that B-DIM could be a potent agent for the prevention and/or treatment of both hormone sensitive as well as hormone-refractory prostate cancer.

A small-molecule triptolide suppresses angiogenesis and invasion of human anaplastic thyroid carcinoma cells via down-regulation of the nuclear factor-kappa B pathway

Anaplastic thyroid carcinoma (ATC) is among the most aggressive malignancies known and is characterized with rapid growth, early invasion, and complete refractoriness to current therapies. Here we report that triptolide, a small molecule from a Chinese herb, could potently inhibit proliferation in vitro, angiogenesis in vivo, and invasion in a Matrigel model in human ATC cell line TA-K cells at nanomolar concentrations. We further elucidate that triptolide inhibits the nuclear factor-kappaB (NF-kappaB) transcriptional activity via blocking the association of p65 subunit with CREB-binding protein (CBP)/p300 in the early stage and via decreasing the protein level of p65 in the late stage. Expression of the NF-kappaB targeting genes cyclin D1, vascular endothelial growth factor, and urokinase-type plasminogen activator is significantly reduced by triptolide in both TA-K and 8505C human ATC cell lines, which are well known to be critical for proliferation, angiogenesis, and invasion in solid tumors. Our findings suggest that triptolide may function as a small molecule inhibitor of tumor angiogenesis and invasion and may provide novel mechanistic insights into the potential therapy for human ATC.

Acquisition of epithelial-mesenchymal transition phenotype of gemcitabine-resistant pancreatic cancer cells is linked with activation of the notch signaling pathway

Despite rapid advances in many fronts, pancreatic cancer (PC) remains one of the most difficult human malignancies to treat due, in part, to de novo and acquired chemoresistance and radioresistance. Gemcitabine alone or in combination with other conventional therapeutics is the standard of care for the treatment of advanced PC without any significant improvement in the overall survival of patients diagnosed with this deadly disease. Previous studies have shown that PC cells that are gemcitabine-resistant (GR) acquired epithelial-mesenchymal transition (EMT) phenotype, which is reminiscent of "cancer stem-like cells"; however, the molecular mechanism that led to EMT phenotype has not been fully investigated. The present study shows that Notch-2 and its ligand, Jagged-1, are highly up-regulated in GR cells, which is consistent with the role of the Notch signaling pathway in the acquisition of EMT and cancer stem-like cell phenotype. We also found that the down-regulation of Notch signaling was associated with decreased invasive behavior of GR cells. Moreover, down-regulation of Notch signaling by siRNA approach led to partial reversal of the EMT phenotype, resulting in the mesenchymal-epithelial transition, which was associated with decreased expression of vimentin, ZEB1, Slug, Snail, and nuclear factor-kappaB. These results provide molecular evidence showing that the activation of Notch signaling is mechanistically linked with chemoresistance phenotype (EMT phenotype) of PC cells, suggesting that the inactivation of Notch signaling by novel strategies could be a potential targeted therapeutic approach for overcoming chemoresistance toward the prevention of tumor progression and/or treatment of metastatic PC.

SmgGDS is up-regulated in prostate carcinoma and promotes tumour phenotypes in prostate cancer cells

SmgGDS is a guanine nucleotide exchange factor with the unique ability to activate multiple small GTPases, implicating it in cancer development and progression. Here, we investigated the role of SmgGDS in prostate cancer by studying the expression of SmgGDS in benign and malignant prostatic tissues. We also probed SmgGDS function in three prostate carcinoma cell lines using small interfering RNA (siRNA). Immunohistochemical analysis revealed that SmgGDS levels were elevated in prostatic intraepithelial neoplasia (PIN), prostate carcinoma, and metastatic prostate carcinoma. In addition, expression of SmgGDS positively correlated with that of cyclooxygenase-2 (COX-2), a protein believed to promote the development of prostate carcinoma. Reduction of SmgGDS expression in prostate carcinoma cells inhibited proliferation and migration, irrespective of androgen receptor status. These effects were accompanied by a reduction in COX-2 expression and in activity of NF-kappaB, a known regulator of COX-2. Taken together, these findings suggest that SmgGDS promotes the development and progression of prostate cancer, possibly associated with NF-kappaB-dependent up-regulation of COX-2.

Plumbagin, a medicinal plant-derived naphthoquinone, is a novel inhibitor of the growth and invasion of hormone-refractory prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men. Hormone-refractory invasive PCa is the end stage and accounts for the majority of PCa patient deaths. We present here that plumbagin (PL), a quinoid constituent isolated from the root of the medicinal plant Plumbago zeylanica L., may be a potential novel agent in the control of hormone-refractory PCa. Specific observations are the findings that PL inhibited PCa cell invasion and selectively induced apoptosis in PCa cells but not in immortalized nontumorigenic prostate epithelial RWPE-1 cells. In addition, i.p. administration of PL (2 mg/kg body weight), beginning 3 days after ectopic implantation of hormone-refractory DU145 PCa cells, delayed tumor growth by 3 weeks and reduced both tumor weight and volume by 90%. Discontinuation of PL treatment in PL-treated mice for as long as 4 weeks did not result in progression of tumor growth. PL, at concentrations as low as 5 micromol/L, inhibited in both cultured PCa cells and DU145 xenografts (a) the expression of protein kinase Cepsilon (PKCepsilon), phosphatidylinositol 3-kinase, phosphorylated AKT, phosphorylated Janus-activated kinase-2, and phosphorylated signal transducer and activator of transcription 3 (Stat3); (b) the DNA-binding activity of transcription factors activator protein-1, nuclear factor-kappaB, and Stat3; and (c) Bcl-xL, cdc25A, and cyclooxygenase-2 expression. The results indicate for the first time, using both in vitro and in vivo preclinical models, that PL inhibits the growth and invasion of PCa. PL inhibits multiple molecular targets including PKCepsilon, a predictive biomarker of PCa aggressiveness. PL may be a novel agent for therapy of hormone-refractory PCa.