HDAC inhibitor SB939 potentiates TRAIL-induced apoptosis in colorectal cancer cells.

Colorectal cancer (CRC) displays noticeable resistance to chemotherapeutic drugs or innovative tumor cell apoptosis-inducing agents such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Thus, sensitizers are needed to enhance the effects of TRAIL-based cancer therapies. Elevated tumor cell death has been reported when various HDAC inhibitors are administered with TRAIL in various human cancers; however, SB939-TRAIL combined treatment has not been reported. In this study, we determined the ability of SB939 and TRAIL, as single agents or in combination, to inhibit the growth and survival of colorectal cancer cells. Our results demonstrated the effects of SB939 and TRAIL on cell viability, apoptosis, and morphological changes in HT-29 cells. SB939 treatment induces hyper-acetylation of histones and death receptors (DR) by activating MAPK proteins in a dose- and time-dependent manner. The ability of SB939 to sensitize HT-29 cells suggests that SB939 can induce essential changes in cell signaling pathways. Thus, the pan-HDAC inhibitor SB939 sensitizes TRAIL-induced apoptosis via up-regulation of DR5, and SB939-TRAIL combined treatment may target the MAPK pathways and serve as an effective therapeutic strategy against CRC.

Lipocalin 2 activates the NLRP3 inflammasome via LPS­induced NF­κB signaling and plays a role as a pro­inflammatory regulator in murine macrophages.

Lipocalin 2 (LCN2) is highly expressed in several infectious and inflammatory disorders. However, the expression level and underlying mechanism of LCN2 in inflammatory bowel disease (IBD) are poorly understood. The current study used murine IBD models and LPS­activated macrophages to elucidate the role of LCN2 in IBD pathogenesis. The levels of LCN2 protein and concentration were confirmed to be much higher in the colons of colitis­induced mice compared with healthy mice using immunohistochemistry, western blotting and ELISA assay. In vitro, the level of LCN2 in RAW264.7 macrophages increased significantly following LPS stimulation and diminished markedly upon using NF­κB­specific inhibitors. Assembly of the NOD­, LRR­, and pyrin domain­containing protein 3 (NLRP3) inflammasome was inhibited when LCN2 expression was knocked down, as evidenced by decreased NLRP3, ASC­1 and caspase­1 activation. Furthermore, secretion and maturation of IL­1ß was attenuated when LCN2 was silenced in LPS­stimulated macrophages. Together, these results suggested that LCN2 directly upregulated the NLRP3 inflammasome complex via NF­κB activation in response to stimulating macrophages with LPS, and that it acted as a pro­inflammatory regulator in macrophage activation modulated by NF­κB activation. Overall, LCN2 may serve as a promising target for the prevention and treatment of IBD.

Lipocalin 2 potentially contributes to tumorigenesis from colitis via IL-6/STAT3/NF-κB signaling pathway.

Lipocalin (LCN) 2 (LCN2), a member of the lipocalin superfamily, plays an important role in oncogenesis and progression in various types of cancer. However, the role of LCN2 in inflammation-associated cancer remains unknown. Here, we explored the functional role and mechanisms of LCN2 in tumorigenesis using murine colitis-associated cancer (CAC) models and human colorectal cancer (CRC) cells. Using murine CAC models, we found that LCN2 was preferentially expressed in colonic tissues from CAC models compared with tissues from normal mice. In vitro results demonstrated that the levels of LCN2 mRNA and protein were markedly up-regulated by interleukin (IL) 6 (IL-6) in human CRC cells. Interestingly, we found LCN2 up-regulation by IL-6 is diminished by nuclear factor-κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3) inhibition using specific inhibitors and small interfering RNA (siRNA). Reporter assay results determined that IL-6 induces LCN2 gene promoter activity under control of NF-κB/STAT3 activation. IL-6-induced LCN2 regulated cell survival and susceptibility of developmental factors to the NF-κB/STAT3 pathway. Taken together, our results highlight the unknown role of LCN2 in CAC progression and suggest that increased LCN2 may serve as an indicator of CRC development in the setting of chronic inflammation.

The HDAC1 Inhibitor CBUD-1001 Enhances TRAIL-induced Apoptosis in Colorectal Cancer Cells.

BACKGROUND/AIM: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potential anti-tumor agent. However, resistance to TRAIL has been reported in a number of clinical trials. In this study, we investigated the molecular mechanisms by which a novel histone deacetylase (HDAC) inhibitor, CBUD-1001, sensitizes colorectal cancer (CRC) cells to TRAIL-induced apoptosis. MATERIALS AND METHODS: Apoptotic cell death induced by CBUD-1001 and/or TRAIL was assessed on human CRC cells using the MTT assay, FACS analysis and nuclei staining. The involved molecular mechanisms were explored through western blotting analysis. RESULTS: We demonstrated that combined with CBUD-1001, TRAIL significantly enhanced TRAIL-induced apoptosis in CRC cells via mitochondria-mediated pathways. We also found that hyper-acetylation of histone by CBUD-1001 treatment leads to up-regulation of death receptor (DR) 5 in a dose- and time-dependent manner. Furthermore, we identified that enhanced sensitivity to TRAIL by combination with CBUD-1001 depends on the MAPK/CHOP axis, being a key mediator of DR5. CONCLUSION: A novel HDAC inhibitor CBUD-1001 sensitizes TRAIL-induced apoptosis via up-regulation of DR5, and that CBUD-1001 and TRAIL combination treatment offers an effective strategy to overcome TRAIL resistance in CRC cells.

A novel HDAC1 inhibitor, CBUD­1001, exerts anticancer effects by modulating the apoptosis and EMT of colorectal cancer cells.

Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies and is a leading cause of cancer­related mortality worldwide. Histone deacetylases (HDACs) are a class of enzymes responsible for the epigenetic regulation of gene expression. Some HDAC inhibitors have been shown to be efficient agents for cancer treatment. The aim of the present study was to discover a novel, potent HDAC inhibitor and demonstrate its anticancer effect and molecular mechanisms in CRC cells. A novel fluorinated aminophenyl­benzamide­based compound, CBUD­1001, was designed to specifically target HDAC1, and it was then synthesized and evaluated. CBUD­1001 exerted a potent inhibitory effect on HDAC enzyme activity and exhibited anticancer potency against CRC cell lines. Molecular docking analysis rationalized the high potency of CBUD­1001 by validating its conformation in the HDAC active site. Further investigation using CRC cells demonstrated that CBUD­1001 inhibited HDAC activity by hyper­acetylating histones H3 and H4, and it exerted an apoptotic effect by activating a mitochondrial­dependent pathway. Of note, it was found that CBUD­1001 attenuates the cell motility of CRC cells by downregulating the EMT signaling pathway. Thus, CBUD­1001 may prove to be a promising novel drug candidate for CRC therapy.

[Corrigendum] Lipocalin 2 inversely regulates TRAIL sensitivity through p38 MAPK­mediated DR5 regulation in colorectal cancer.

Following the publication of this article, an interested reader drew to our attention that Fig. 1C contained an important flaw. The Figure shows a western blot for LCN2, DR4, DR5, and actin, and it was noted that the identical bands shown for actin were also featured in a paper by the same authors published in 2017 [Lipocalin 2 negatively regulates cell proliferation and epithelial to mesenchymal transition through changing metabolic gene expression in colorectal cancer. Kim SL, Lee ST, Min IS, Park YR, Lee JH, Kim DG and Kim SW: Cancer Sci 108: 2176­2186, 2017], except that the lanes for the cell lines HCT116 and SW620 were depicted the other way around in the International Journal of Oncology article. Upon investigating the matter with the authors, they were able to confirm that the lanes were labelled incorrectly in the Figure itself; moreover, the incorrect control bands were included with the Figure. The corrected version of Fig. 1 is shown opposite, including the correct control data for Fig. 1C. This error did not have an impact on the overall meaning of the paper, or on the reported conclusions of this study. The authors regret that this error was introduced into the printed version of the paper, and apologize to the readership for any inconvenience caused. [the original article was published in International Journal of Oncology 53: 2789­2799, 2018; DOI: 10.3892/ijo.2018.4562].

Down-regulation of miR-9 promotes epithelial mesenchymal transition via regulating anoctamin-1 (ANO1) in CRC cells.

MicroRNA-9 (miR-9) has been reported to play a suppressive or promoting role according to cancer type. In this study, we investigated the effects of anoctamin-1 (ANO1) and miR-9 on colorectal cancer (CRC) cell proliferation, migration, and invasion and determined the underlying molecular mechanisms. Thirty-two paired CRC tissues and adjacent normal tissues were analyzed for ANO1 expression using quantitative real-time PCR (qRT-PCR). HCT116 cells were transiently transfected with miR-9 mimic, miR-9 inhibitor, or si-ANO1. Cell proliferation was determined by MTT, and flow cytometric analysis, while cell migration and invasion were assayed by trans-well migration and invasion assay in HCT116 cells. ANO1 was validated as a target of miR-9 using luciferase reporter assay and bioinformatics algorithms. We found that ANO1 expression was up-regulated in CRC tissues compared with adjacent normal tissues. ANO1 expression was associated with advanced tumor stage and lymph node metastasis, and there was an inverse relationship between miR-9 and ANO1 mRNA expression in CRC specimens, but no significant difference was found between miR-9 and ANO1 expression. ANO1 is a direct target of miR-9, and overexpression of miR-9 suppressed both mRNA and protein expression of ANO1 and inhibited cell proliferation, migration, and invasion of HCT116 cells. We also showed that overexpression of miR-9 suppressed expression of p-AKT, cyclin D1, and p-ERK in HCT116 cells. We conclude that miR-9 inhibits CRC cell proliferation, migration, and invasion by directly targeting ANO1, and miR-9/ANO1 could be a potential therapeutic target for CRC.

Lipocalin 2 inversely regulates TRAIL sensitivity through p38 MAPK-mediated DR5 regulation in colorectal cancer.

TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis through death receptors (DRs)4 and/or 5 expressed on the cell surface. Multiple clinical trials are underway to evaluate the antitumor activity of recombinant human TRAIL and agonistic antibodies to DR4 or DR5. However, their therapeutic potential is limited by the high frequency of cancer resistance. In this study, we provide evidence demonstrating the role of lipocalin 2 (LCN2) in the TRAIL-mediated apoptosis of human colorectal cancer (CRC). By analyzing the mRNA expression data of 71 CRC tissues from patients, we found that DR5 was preferentially expressed in CRC tissues with a low LCN2 expression level compared to tissues with a high LCN2 expression level. Moreover, we analyzed the association between DR5 and LCN2 expression and this analysis revealed that DR5 expression in CRC tended to be inversely associated with LCN2 expression. By contrast, no association was found between the DR4 and LCN2 expression levels. The expression patterns of LCN2 in human CRC cell lines also exhibited an inverse association with DR5 expression. The knockdown of LCN2 by siRNA in the TRAIL­resistant CRC cells expressing high levels of LCN2 led to a significant increase in TRAIL-induced apoptosis through the upregulation of DR5 protein and mRNA expression. The mechanism through which LCN2 silencing sensitized the CRC cells to TRAIL was dependent on the extrinsic pathway of apoptosis. In addition, we identified that the knockdown of LCN2 enhanced the sensitivity of the cells to TRAIL through the p38 MAPK/CHOP-dependent upregulation of DR5. Taken together, the findings of this study suggest that LCN2 is responsible for TRAIL sensitivity and LCN2 may thus prove to be a promising target protein in DR-targeted CRC therapy.

MiRNA-206 suppresses PGE2-induced colorectal cancer cell proliferation, migration, and invasion by targetting TM4SF1.

MiRNA (miR)-206 plays a tumor suppressor role in various cancer types. Here, we investigated whether miR-206 is involved in prostaglandin E2 (PGE2)-induced epithelial-mesenchymal transition (EMT) in colorectal cancer (CRC) cells through the targetting of transmembrane 4 L six family member 1 (TM4SF1).The effect of PGE2 on growth and apoptosis of CRC cells was evaluated using the MTT assay and flow cytometry analysis, respectively. TM4SF1 and miR-206 expression levels were determined with quantitative polymerase chain reaction (qRT-PCR) in CRC tissues and cell lines. The concentration of PGE2 in the serum of CRC patients and healthy controls was measured with an ELISA kit. A miR-206 or TM4SF1 construct was transfected into cells with PGE2. Transwell migration and invasion assays were used to examine cell migration and invasion properties. Additionally, a luciferase assay was performed to determine whether TM4SF1 was directly targetted by miR-206.We found that miR-206 was down-regulated and TM4SF1 was up-regulated in human CRC tissues and cell lines. Moreover, miR-206 was negatively correlated with TM4SF1 expression. Bioinformatics analysis and a luciferase reporter assay revealed that miR-206 directly targetted the 3'-untranslated region (UTR) of TM4SF1, and TM4SF1 expression was reduced by miR-206 overexpression at both the mRNA and protein levels. Additionally, PGE2 significantly suppressed the expression of miR-206 and increased the expression of TM4SF1 in CRC cells. PGE2 induction led to enhanced CRC cell proliferation, migration, and invasion. Moreover, the overexpression of miR-206 decreased CRC cell proliferation, migration, and invasion compared with control group in PGE2-induced cells, and these effects could be recovered by the overexpression of TM4SF1. Overexpression of miR-206 also suppressed the expression of ß-catenin, VEGF, MMP-9, Snail, and Vimentin and enhanced E-cadherin expression in PGE2-induced cells. These results could be reversed by the overexpression of TM4SF1. At last, up-regulation of miR-206 suppressed expression of p-AKT and p-ERK by targetting TM4SF1 in PGE2-induced cells.Our results provide further evidence that miR-206 has a protective effect on PGE2-induced colon carcinogenesis.

Parthenolide suppresses hypoxia-inducible factor-1α signaling and hypoxia induced epithelial-mesenchymal transition in colorectal cancer.

Activation of hypoxia-inducible factor 1α (HIF­1α) is frequently observed in solid tumors and it has been associated with various pathophysiological processes, including epithelial­mesenchymal transition (EMT). Previously, we reported that parthenolide (PT), an inhibitor of nuclear factor-κB (NF-κB), is a promising anticancer agent because it promotes apoptosis of human colorectal cancer (CRC). Here, we investigated a new molecular mechanism by which PT acts on HIF­1α and hypoxia contributing to EMT by NF­κB inhibition. Cell viability, DNA binding activity, vascular cell tube formation and cell motility were studied after treatment of PT in hypoxic or normoxic condition. Moreover, effects of PT on hypoxia signaling and hypoxia-induced EMT signaling were investigated. We also examined the inhibitory effect of PT on CRC progression in xenografts. We demonstrated that PT markedly inhibits hypoxia dependent HIF­1α activity and angiogenesis by preventing NF-κB activation. We also report that PT decreases the level of proteins associated with glucose metabolism, angiogenesis, development and survival that are regulated by HIF­1α. Furthermore, we verified that PT protects the morphological change from epithelial to mesenchymal state, inhibits matrix metalloproteinase (MMP) enzyme activity and decreases cell motility involved in the -regulation of the hypoxia-induced EMT markers. In addition, PT inhibits growth in CRC xenograft models and regulates NF­κB, HIF­1α and EMT specific marker in tissue specimens. Our data demonstrated that PT can inhibit HIF­1α signaling and hypoxia-induced EMT, suggesting a novel molecular mechanism for HIF­1α mediated cancer progression and metastasis.

Lipocalin 2 negatively regulates cell proliferation and epithelial to mesenchymal transition through changing metabolic gene expression in colorectal cancer.

Lipocalin 2 (LCN2), a member of the lipocalin superfamily, plays an important role in oncogenesis and progression in various types of cancer. However, the expression pattern and functional role of LCN2 in colorectal cancer (CRC) is still poorly understood. The purpose of the present study was to investigate whether LCN2 is associated with proliferation and the epithelial-mesenchymal transition (EMT) in CRC and to elucidate the underlying signaling pathways. LCN2 was preferentially expressed in CRC cells compared to normal tissues. However, LCN2 expression was significantly lower in metastatic or advanced-stage CRC than in non-metastatic or early stage CRC. Knockdown of LCN2 using small interfering RNA (siRNA) in CRC cells expressing a high level of LCN2 induced cell proliferation and a morphological switch from an epithelial to mesenchymal state. Furthermore, downregulation of LCN2 in CRC cells increased cell migration and invasion involved in the regulation of EMT markers. Knockdown of LCN2 also induced glucose consumption and lactate production, accompanied by an increase in energy metabolism-related genes. Taken together, our findings indicated that LCN2 negatively modulated proliferation, EMT and energy metabolism in CRC cells. Accordingly, LCN2 may be a candidate metastasis suppressor and potential therapeutic target in CRC.

Parthenolide promotes apoptotic cell death and inhibits the migration and invasion of SW620 cells.

BACKGROUND/AIMS: Parthenolide (PT), a principle component derived from feverfew (Tanacetum parthenium), is a promising anticancer agent and has been shown to promote apoptotic cell death in various cancer cells. In this study, we focused on its functional role in apoptosis, migration, and invasion of human colorectal cancer (CRC) cells. METHODS: SW620 cells were employed as representative human CRC cells. We performed the MTT assay and cell cycle analysis to measure apoptotic cell death. The wound healing, Transwell migration, and Matrigel invasion assays were performed to investigate the effect of PT on cell migration/invasion. Western blotting was used to establish the signaling pathway of apoptosis and cell migration/invasion. RESULTS: PT exerts antiproliferative effect and induces apoptotic cell death of SW620 cells. In addition, PT prevents cell migration and invasion in a dose-dependent manner. Moreover, PT markedly suppressed migration/invasion-related protein expression, including E-cadherin, ß-catenin, vimentin, Snail, cyclooxygenase-2, matrix metalloproteinase-2 (MMP-2), and MMP-9 in SW620 cells. PT also inhibited the expression of antiapoptotic proteins (Bcl-2 and Bcl-xL) and activated apoptosis terminal factor (caspase-3) in a dose-dependent manner. CONCLUSIONS: Our results suggest that PT is a potential novel therapeutic agent for aggressive CRC treatment.

Combined Parthenolide and Balsalazide Have Enhanced Antitumor Efficacy Through Blockade of NF-κB Activation.

Balsalazide is a colon-specific prodrug of 5-aminosalicylate that is associated with a reduced risk of colon cancer in patients with ulcerative colitis. Parthenolide, a strong NF-κB inhibitor, has recently been demonstrated to be a promising therapeutic agent, promoting apoptosis of cancer cells. In the current study, the antitumor effect of balsalazide combined with parthenolide in human colorectal cancer cells and colitis-associated colon cancers (CAC) was investigated. The results demonstrate that the combination of balsalazide and parthenolide markedly suppress proliferation, nuclear translocation of NF-κB, IκB-α phosphorylation, NF-κB DNA binding, and expression of NF-κB targets. Apoptosis via NF-κB signaling was confirmed by detecting expression of caspases, p53 and PARP. Moreover, treatment of a CAC murine model with parthenolide and balsalazide together resulted in significant recovery of body weight and improvement in histologic severity. Administration of parthenolide and balsalazide to CAC mice also suppressed carcinogenesis as demonstrated by uptake of 18F-fluoro-2-deoxy-D-glucose (FDG) using micro-PET/CT scans. These results demonstrate that parthenolide potentiates the efficacy of balsalazide through synergistic inhibition of NF-κB activation and the combination of dual agents prevents colon carcinogenesis from chronic inflammation. IMPLICATIONS: This study represents the first evidence that combination therapy with balsalazide and parthenolide could be a new regimen for colorectal cancer treatment. Mol Cancer Res; 15(2); 141-51. ©2016 AACR.

MicroRNA-9 suppresses cell migration and invasion through downregulation of TM4SF1 in colorectal cancer.

Transmembrane-4-L6 family 1 (TM4SF1) is upregulated in colorectal carcinoma (CRC). However, the mechanism leading to inhibition of the TM4SF1 is not known. In the present study, we investigated the regulation of TM4SF1 and function of microRNAs (miRNAs) in CRC invasion and metastasis. We analyzed 60 colon cancers and paired normal specimens for TM4SF1 and miRNA-9 (miR-9) expression using quantitative real-time PCR. A bioinformatics analysis identified a putative miR-9 binding site within the 3'-UTR of TM4SF1. We also found that TM4SF1 was upregulated in CRC tissues and CRC cell lines. The expression of TM4SF1 was positively correlated with clinical advanced stage and lymph node metastasis. Moreover, a luciferase assay revealed that miR-9 directly targeted 3'-UTR-TM4SF1. Overexpression of miR-9 inhibited expression of TM4SF1 mRNA and protein, wound healing, transwell migration and invasion of SW480 cells, whereas, overexpression of anti-miR-9 and siRNA-TM4SF1 inversely regulated the TM4SF1 mRNA and protein level in HCT116 cells. Furthermore, miR-9 suppressed not only TM4SF1 expression but also MMP-2, MMP-9 and VEGF expression. In clinical specimens, miR-9 was generally down-regulated in CRC and inversely correlated with TM4SF1 expression. These results suggest that miR-9 functions as a tumor-suppressor in CRC, and that its suppressive effects mediate invasion and metastasis by inhibition of TM4SF1 expression. Our results also indicate that miR-9 might be a novel target for the treatment of CRC invasion and metastasis.

Parthenolide induces apoptosis in colitis-associated colon cancer, inhibiting NF-κB signaling.

Recently, the nuclear factor (NF)-κB inhibitor parthenolide (PT) was identified as a promising anticancer agent for the promotion of cancer cell apoptosis. Additionally, our previous study demonstrated that PT administration suppresses tumor growth in a xenograft model of colorectal cancer cells via regulation of the B-cell lymphoma-2 (Bcl-2) family. However, the role of PT in the development of colitis-associated colon cancer (CAC) is poorly understood. Therefore, the aim of the present study was to investigate the effects of PT administration on CAC using a murine model. Azoxymethane (AOM) and dextran sulfate sodium (DSS) were administered to induce experimental CAC in the following three groups of treated mice: i) AOM and DSS plus vehicle; ii) AOM, DSS and 2 mg/kg PT; and iii) AOM, DSS and 4 mg/kg PT. It was demonstrated that the histological acuteness of AOM/DSS-induced CAC was significantly reduced following the administration of PT, resulting in decreased NF-κB p65 expression levels via a blockade of phosphorylation and subsequent degradation of inhibitor of κB-α (IκBα). Furthermore, PT administration appeared to enhance the process of carcinogenesis via the downregulation of the antiapoptotic proteins Bcl-2 and Bcl-extra large, mediated by inhibition of NF-κB activation. Apoptosis and caspase-3 expression were markedly increased in the PT-treated group. These findings indicate that PT inhibits IκBα phosphorylation and NF-κB activation, resulting in the initiation of apoptosis and the eventual suppression of CAC development. The beneficial effects of PT treatment observed in the experimental CAC model indicate the potential chemopreventive and therapeutic role of PT in CAC.

Balsalazide Potentiates Parthenolide-Mediated Inhibition of Nuclear Factor-κB Signaling in HCT116 Human Colorectal Cancer Cells.

BACKGROUND/AIMS: Balsalazide is an anti-inflammatory drug used in the treatment of inflammatory bowel disease. Balsalazide can reduce inflammatory responses via several mechanisms, including inhibition of nuclear factor-κB (NF-κB) activity. Parthenolide (PT) inhibits NF-κB and exerts promising anticancer effects by promoting apoptosis. The present investigated the antitumor effects of balsalazide, combined with PT, on NF-κB in a representative human colorectal carcinoma cell line, HCT116. METHODS: We counted cells and conducted annexin-V assays and cell cycle analysis to measure apoptotic cell death. Western blotting was used investigate the levels of proteins involved in apoptosis. RESULTS: PT and balsalazide produced synergistic anti-proliferative effects and induced apoptotic cell death. The combination of balsalazide and PT markedly suppressed nuclear translocation of the NF-κB p65 subunit and the phosphorylation of inhibitor of NF-κB. Moreover, PT and balsalazide dramatically enhanced NF-κB p65 phosphorylation. Apoptosis, through the mitochondrial pathway, was confirmed by detecting effects on Bcl-2 family members, cytochrome c release, and activation of caspase-3 and -8. CONCLUSIONS: Combination treatment with PT and balsalazide may offer an effective strategy for the induction of apoptosis in HCT116 cells.

Parthenolide enhances sensitivity of colorectal cancer cells to TRAIL by inducing death receptor 5 and promotes TRAIL-induced apoptosis.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent. Recombinant human TRAIL has been evaluated in clinical trials, however, various malignant tumors are resistant to TRAIL. Parthenolide (PT) has recently been demonstrated as a highly effective anticancer agent and has been suggested to be used for combination therapy with other anticancer agents. In this study, we investigate the molecular mechanisms by which PT sensitizes colorectal cancer (CRC) cells to TRAIL-induced apoptosis. HT-29 (TRAIL-resistant) and HCT116 (TRAIL-sensitive) cells were treated with PT and/or TRAIL. The results demonstrated that combined treatment induced apoptosis which was determined using MTT, cell cycle analysis, Annexin V assay and Hoechst 33258 staining. Interestingly, we confirmed that HCT116 cells have much higher death receptor (DR) 5 than HT-29 cells and PT upregulates DR5 protein level and surface expression in both cell lines. Apoptosis through the mitochondrial pathway was confirmed by detecting regulation of Bcl-2 family members, p53 cytochrome C release, and caspase cascades. These results suggest that PT sensitizes TRAIL-induced apoptosis via upregulation of DR5 and mitochondria-dependent pathway. Combination treatment using PT and TRAIL may offer an effective strategy to overcome TRAIL resistance of certain CRC cells.

Parthenolide Sensitizes Human Colorectal Cancer Cells to Tumor Necrosis Factor-related Apoptosis-inducing Ligand through Mitochondrial and Caspase Dependent Pathway.

BACKGROUND/AIMS: Combination therapy utilizing tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in conjunction with other anticancer agents, is a promising strategy to overcome TRAIL resistance in malignant cells. Recently, parthenolide (PT) has proved to be a promising anticancer agent, and several studies have explored its use in combination therapy. Here, we investigated the molecular mechanisms by which PT sensitizes colorectal cancer (CRC) cells to TRAIL-induced apoptosis. METHODS: HT-29 cells (TRAIL-resistant) were treated with PT and/or TRAIL for 24 hours. The inhibitory effect on proliferation was detected using the 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Annexin V staining, cell cycle analysis, and Hoechst 33258 staining were used to assess apoptotic cell death. Activation of an apoptotic pathway was confirmed by Western blot. RESULTS: Treatment with TRAIL alone inhibited the proliferation of HCT 116 cells in a dose-dependent manner, whereas proliferation was not affected in HT-29 cells. Combination PT and TRAIL treatment significantly inhibited cell growth and induced apoptosis of HT-29 cells. We observed that the synergistic effect was associated with misregulation of B-cell lymphoma 2 (Bcl-2) family members, release of cytochrome C to the cytosol, activation of caspases, and increased levels of p53. CONCLUSION: Combination therapy using PT and TRAIL might offer an effetive strategy to overcome TRAIL resistance in certain CRC cells.

Parthenolide exerts inhibitory effects on angiogenesis through the downregulation of VEGF/VEGFRs in colorectal cancer.

Parthenolide (PT) is responsible for the bioactivities of feverfew (Tanacetum parthenium). Apart from its potent anti-inflammatory effects, this compound has been reported to induce apoptosis in various cancer cells. However, little is known about its role in the process of tumor angiogenesis. In the present study, we investigated the effects and potential mechanisms of action of PT on angiogenesis in human colorectal cancer (CRC). The anti-angiogenic effects of PT were evaluated in cultured human umbilical vein endothelial cells (HUVECs) and in the human CRC cell lines, HT-29, SW620 and HCT116. PT markedly inhibited vascular cell migration and capillary-like structure formation even at a dose which had not effects on cell viability. PT also suppressed the expression of angiogenic biomarker proteins [vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)1 and VEGFR2] in both the HUVECs and CRC cells. Additionally, PT effectively inhibited tumor neovascularization in a HT-29 xenograft model. These results indicate that PT suppresses angiogenesis by reducing the expression of VEGF and its receptors and may be a viable drug candidate in anti-angiogenesis therapies for human CRC.

Synergistic antitumor effect of 5-fluorouracil in combination with parthenolide in human colorectal cancer.

Parthenolide (PT), a NF-κB inhibitor, has recently been demonstrated as a promising anticancer agent that promotes apoptosis of cancer cells. 5-fluorouracil (5-FU) has been a drug of choice for treatment of colorectal cancer (CRC). Unfortunately, many of the therapies that use 5-FU alone or in combination with other agents are likely to become ineffective due to drug resistance. In the present study, we investigated the antitumor effect of PT combined with 5-FU on a human CRC cell line, SW620. The results demonstrated that combination of PT and 5-FU induced apoptosis which was determined using MTT, cell cycle analysis, annexin-V assay, and Hoechst 33258 staining. Apoptosis through the mitochondrial pathway was confirmed by detecting regulation of Bcl-2 family members, cytochrome C release, and activation of caspase 3 and 9. Moreover, intra-peritoneal injection of PT and 5-FU showed significant inhibition of tumor growth in the xenograft model. These results demonstrate that PT exhibits anticancer activity in human colorectal cancer in vitro and in vivo. These findings provide an efficacious strategy to overcome 5-FU resistance in certain CRC.