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Casein kinase II (CK2) inhibitors suppress cancer cell growth. In this study, we examined the inhibitory effects of a novel CK2 inhibitor, hematein, on tumor growth in a murine xenograft model. We found that in lung cancer cells, hematein inhibited cancer cell growth, Akt/PKB Ser129 phosphorylation, the Wnt/TCF pathway and increased apoptosis. In a murine xenograft model of lung cancer, hematein inhibited tumor growth without significant toxicity to the mice tested. Molecular docking showed that hematein binds to CK2α in durable binding sites. Collectively, our results suggest that hematein is an allosteric inhibitor of protein kinase CK2 and has antitumor activity to lung cancer.

Introduction: Heat shock protein 90 (Hsp90) is an abundant molecular chaperone that mediates the maturation and stability of a variety of proteins associated with the promotion of cell growth and survival. Inhibition of Hsp90 function leads to proteasomal degradation of its mis-folded client proteins. Recently, Hsp90 has emerged as being of prime importance to the growth and survival of cancer cells and its inhibitors have already been used in phase I and II clinical trials., Methods: We investigated how 17-allylamino-17-demethoxygeldanamycin (17-AAG), a small molecule inhibitor of Hsp90, is implicated in human malignant pleural mesothelioma (MM)., Results: We found that 17-AAG led to significant G1 or G2/M cell cycle arrest, inhibition of cell proliferation, and decrease of AKT, AKT1, and survivin expression in all human malignant pleural mesothelioma cell lines examined. We also observed significant apoptosis induction in all MM cell lines treated with 17-AAG. Furthermore, 17-AAG induced apoptosis in freshly cultured primary MM cells and caused signaling changes identical to those in 17-AAG treated MM cell lines., Conclusion: These results suggest that Hsp90 is strongly associated with the growth and survival of MM and that inhibition of Hsp90 may have therapeutic potential in the treatment of MM.

Nasopharyngeal carcinoma (NPC) is a head and neck cancer rare throughout most of the world but common in certain geographic areas, such as southern Asia. While environmental factors and genetic susceptibility play important roles in NPC pathogenesis, the Epstein-Barr virus in particular has been implicated in the molecular abnormalities leading to NPC. There is upregulation of cellular proliferation pathways such as the Akt pathway, mitogen-activated protein kinases, and the Wnt pathway. Cell adhesion is compromised due to abnormal E-cadherin and beta-catenin function. Aberrations in cell cycle are due to dysregulation of factors such as p16, cyclin D1, and cyclin E. Anti-apoptotic mechanisms are also upregulated. There are multiple abnormalities unique to NPC that are potential targets for novel treatments.

Constitutive activation of the Wnt pathway as a result of APC, AXIN1 or CTNNB1 mutations has been found in most colorectal cancers. For a long time, this aberrant Wnt activation has been thought to be independent of upstream signals. However, recent studies indicate that upstream signals retain their ability to regulate the Wnt pathway even in the presence of downstream mutations. Wnt-2 is well known for its overexpression in colorectal cancer. Galectin-3 (Gal-3), a multifunctional carbohydrate binding protein implicated in a variety of biological functions, has recently been reported to interact with beta-catenin. In this study, we investigated roles of Wnt-2 and Gal-3 in the regulation of canonical Wnt/beta-catenin signaling. We found that siRNA silencing of either Wnt-2 or Gal-3 expression inhibited TCF-reporter activity, decreased cytosolic beta-catenin level and induced apoptosis in human colorectal cancer cells containing downstream mutations. More interestingly, we showed that inhibition of both Wnt-2 and Gal-3 had synergistic effects on suppressing canonical Wnt signaling and inducing apoptosis, suggesting that aberrant canonical Wnt/beta-catenin signaling in colorectal cancer can be regulated at multiple levels. The combined inhibition of Wnt-2 and Gal-3 may be of superior therapeutic advantage to inhibition by either one of them, giving rise to a potential development of novel drugs for the targeted treatment of colorectal cancer., ((c) 2007 Wiley-Liss, Inc.)

Like many tumors, malignant mesothelioma exhibits significant chemoresistance and resistance to apoptosis in vivo that is not seen in current in vitro models. To study the mechanisms of this multicellular resistance, biologically relevant in vitro models are necessary. Therefore, we characterized and tested human mesothelioma tissue grown in vitro as tumor fragment spheroids. After 5-10 d in culture, fragments from each of 15 human mesothelioma tumors rounded into spheroids. The tumor fragment spheroids maintained multiple characteristics of the original tumors for up to 3 mo including the presence of viable mesothelioma cells, macrophages, and a collagen-rich stroma. In 14-d-old spheroids, mesothelioma cells showed the same proliferation rate and expression of a death receptor, DR5, as in the original tumor. To determine responses to treatment, we treated tumor fragment spheroids grown from three separate tumors with agents, TNF-related apoptosis-inducing ligand (TRAIL) plus cycloheximide, that induced near total apoptosis in three human mesothelioma cell lines (M28, REN, MS-1) grown as monolayers (94 +/- 6% apoptosis; mean +/- SEM). Compared with mesothelioma cells in monolayers, mesothelioma cells in the spheroids were resistant to TRAIL plus cycloheximide (32 +/- 4% apoptosis; mean +/- SEM). Apoptotic resistance of mesothelioma cells was significantly reduced by inhibiting either the PI3K/Akt pathway with LY294002 (47 +/- 6% apoptosis) or the mTOR pathway with rapamycin (50 +/- 17% apoptosis). We conclude that human mesothelioma can be maintained in vitro in a biologically relevant model that exhibits apoptotic resistance, thereby permitting study of its tumor biology and of novel approaches to therapy.

The Wnt family of secreted glycoproteins is widely involved in cell proliferation, differentiation and oncogenesis. Many Wnt signaling genes are upregulated and activated in chronic lymphocytic leukemia. Less is known concerning acute leukemia. One subtype of acute lymphoblastoid leukemia (ALL) is characterized by a t(1;19) chromosomal translocation resulting in a fusion protein E2A-Pbx1 that promotes transformation and leukemogenesis. Wnt16 has been shown to be targeted by E2A-Pbx1. We performed a differential gene expression array in acute leukemia cell lines displaying or not displaying the t(1;19) translocation. We found that Wnt16 and many Wnt signaling-related genes were upregulated in the translocation-containing cells. As two isoforms of Wnt16, Wnt16a and Wnt16b, have been recently identified, we demonstrated by using RT-PCR and Western blot that Wnt16b (and not Wnt16a) is overexpressed in t(1;19)-containing cell lines. We then directly addressed the role played by both isoforms in this type of leukemia. Using specific short interfering RNA (siRNA) and an anti-Wnt16 antibody, we showed that targeted-Wnt16b inhibition leads to apoptotic cell death. We also demonstrated that Wnt16b mediates its effect through the canonical Wnt pathway involving dishevelled-2, beta-catenin and survivin. We thus propose that Wnt16 plays an important role in leukemogenesis, raising its therapeutic interest.

Aberrant Wnt signaling, mainly through mutations of APC and in some cases of CTNNB1 or AXIN2, has been found in the majority of colorectal cancers. Recently, frequent promoter hypermethylation was identified to cause silencing of the secreted frizzled-related protein (sFRP) family in colorectal cancer. Restoration of sFRP in colorectal cancer cells attenuates Wnt signaling even in the presence of downstream mutations. Here we show that Wnt inhibitory factor-1 (WIF-1), a different secreted antagonist of Wnt signaling, is also silenced by promoter hypermethylation in colorectal cancer cells. Restoration of WIF-1 function, Wnt-1 siRNA, or a monoclonal anti-Wnt-1 antibody that we developed attenuates Wnt-1 signaling and induces significant apoptosis in these cells containing downstream mutations and expressing Wnt-1. In addition, this monoclonal anti-Wnt-1 antibody showed synergistic effects with docetaxel in treating these colorectal cancer cells and great efficacy in treating primary colorectal cancer cultures freshly prepared from patients. Therefore, our data support the hypothesis that constitutive Wnt signaling may be required to complement downstream mutations in the evolution of colorectal cancer. Furthermore, our results suggest that blockade of the Wnt signal may have a therapeutic role in the treatment of colorectal cancer.

The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and have important implications in tumorigenesis. Frequent promoter hypermethylation of SFRPs has been identified in human cancer. Restoration of SFRP function attenuates Wnt signaling and induces apoptosis in a variety of cancer types. Wnt signaling is known to inhibit apoptosis through activation of beta-catenin/Tcf-mediated transcription. Recently, we identified aberrant Wnt activation as a result of Dishevelled overexpression in malignant mesothelioma. Here, we report that silencing of SFRP4 is correlated with promoter hypermethylation in beta-catenin-deficient mesothelioma cell lines. Reexpression of SFRP4 in these beta-catenin-deficient mesothelioma cell lines blocks Wnt signaling, induces apoptosis, and suppresses growth. Conversely, knocking down SFRP4 by small interfering RNA in cell lines expressing both SFRP4 and beta-catenin stimulates Wnt signaling, promotes cell growth, and inhibits chemodrug-induced apoptosis. Our results suggest that methylation silencing of SFRP4 may play an important role in aberrant Wnt activation in mesothelioma even in the absence of beta-catenin. Our data also suggest that beta-catenin-independent noncanonical pathway(s) may be involved in the apoptotic inhibition caused by activation of Wnt signaling.

In this report, we have demonstrated that Wnt-2 protein is overexpressed in freshly resected human non-small-cell lung cancer (NSCLC) tissues. We have also developed a monoclonal antibody against the N-terminus of human Wnt-2 protein. This monoclonal antibody induces apoptosis in human NSCLC cell lines that overexpress Wnt-2 protein. Incubation of this antibody with normal human airway cells lacking Wnt-2 expression does not induce apoptosis. Wnt-2 signaling blockade by the anti-Wnt-2 antibody is confirmed by downregulation of cytosolic beta-catenin and reduction in TCF-dependent transcriptional activity (TOPFLASH assay). In addition, Wnt-2-specific small interfering RNA (siRNA) treatment in the NSCLC cell line A549 also downregulated cytosolic beta-catenin and induced apoptosis. Moreover, downregulation of an inhibitor of apoptosis family protein, Survivin, was noticed both in the Wnt-2 antibody- and siRNA-treated NSCLC cells, suggesting that inhibition of Wnt-2-mediated signaling induces apoptosis through inactivating Survinin.

Activation of the Wnt/beta-catenin signaling pathway has been associated with human cancers. To test whether Wnt-2 signal is a survival factor in human melanoma cells and thus represents a potential therapeutic target, we investigated the effects of inhibition of Wnt-2 signaling in human melanoma cell lines. We have developed a novel monoclonal antibody against the NH(2) terminus of the human Wnt-2 ligand that induces apoptosis in human melanoma cells overexpressing Wnt-2. Whereas incubation of this antibody with normal cells lacking Wnt-2 expression does not induce apoptosis, Wnt-2 signaling blockade by the ligand-binding antibody is confirmed by down-regulation of Dishevelled and beta-catenin. Wnt-2 small interfering RNA treatment in these cells yielded similar apoptotic effects and downstream changes. Down-regulation of an inhibitor of apoptosis family protein, survivin, was observed in both the Wnt-2 antibody-treated and small interfering RNA-treated melanoma cell lines, suggesting that the antibody induces apoptosis by inactivating survivin. In an in vivo study, this monoclonal anti-Wnt-2 antibody suppresses tumor growth in a xenograft model. These findings suggest that the anti-Wnt-2 monoclonal antibody may be useful for the treatment of patients with malignant melanoma.

It is known that Wnt-1 signaling inhibits apoptosis by activating beta-catenin/tcf-mediated transcription. Here, we show that blocking Wnt-1 signaling in beta-catenin-deficient mesothelioma cell lines H28 and MS-1 induces apoptotic cell death. Both Wnt-1 small interfering RNA (siRNA) and Dishevelled siRNA induced significant apoptosis in these cell lines. A small molecule inhibitor of c-Jun NH(2)-terminal kinase inhibited the apoptotic cell killing induced by either Wnt-1 siRNA or Dishevelled siRNA in these cells. Our data suggest that beta-catenin-independent noncanonical pathway(s), i.e., Wnt/JNK pathway, may play a role in the apoptotic inhibition caused by Wnt-1 signaling.

Aberrant activation of the Wingless-type (Wnt)/beta-catenin signaling pathway is associated with a variety of human cancers. Little is known regarding the role that Wnt ligands play in human carcinogenesis. To test whether a Wnt-1 signal is a survival factor in human cancer cells and thus may serve as a potential cancer therapeutic target, we investigated the effect of inhibition of Wnt-1 signaling in a variety of human cancer cell lines, including non small cell lung cancer, breast cancer, mesothelioma, and sarcoma. Both monoclonal antibody and RNA interference (RNAi) were used to inhibit Wnt-1 signaling. We found that incubation of a monoclonal anti-Wnt-1 antibody induced apoptosis and caused downstream protein changes in cancer cells overexpressing Wnt-1. In contrast, apoptosis was not detected in cells lacking or having minimal Wnt-1 expression after the antibody incubation. RNAi targeting of Wnt-1 in cancer cells overexpressing Wnt-1 demonstrated similar downstream protein changes and induction of apoptosis. The antibody also suppressed tumor growth in vivo. Our results indicate that both monoclonal anti-Wnt-1 antibody and Wnt-1 siRNA inhibit Wnt-1 signaling and can induce apoptosis in human cancer cells. These findings hold promise as a novel therapeutic strategy for cancer.

Malignant pleural mesothelioma is a rare and aggressive tumor characterized by rapid progression, late metastases, and poor prognosis. In this study, we investigated the expression of survivin, a member of the inhibitors of apoptosis protein gene family, in mesothelioma and an antisense oligonucleotide-based gene therapy for mesothelioma using survivin as a target. Initially, we documented the expression of survivin in human mesothelioma cell lines and fresh tissues using reverse transcription-PCR and Western blot analysis. Our results showed that survivin was overexpressed in 7 of 8 (87.5%) mesothelioma cell lines assayed and in all (12 of 12; 100%) freshly resected mesothelioma tissues analyzed. To investigate the use of survivin as a therapeutic target on mesothelioma, we carried out transfections with antisurvivin oligonucleotides to induce apoptosis in mesothelioma cell lines MS-1 and H28. Results from cellular transfection and subsequent analysis using the flow cytometry demonstrated that antisurvivin oligonucleotides induced significantly greater apoptosis rates in the survivin-positive mesothelioma cell line H28 (42.5%) as compared with the control oligonucleotides (16.2%; P < 0.001). The survivin-negative cell line LRK1A (survivin-/-) did not apoptose with antisense oligonucleotides. Furthermore, time course evaluation by Western blot analysis showed that survivin was inhibited by antisurvivin oligonucleotides within 12 h after transfection. Our results show, for the first time, that survivin, an inhibitors of apoptosis protein family gene member, is highly overexpressed in malignant pleural mesothelioma. Down-regulation of survivin by a targeted antisense oligonucleotide appears to be an effective gene therapy approach to the treatment of mesothelioma.

Acute myeloid leukemia (AML) is the most lethal form of AML due to disease relapse. Cyclin dependent kinase 8 (CDK8) is a serine/threonine kinase that belongs to the family of Cyclin-dependent kinases and is an emerging target for the treatment of AML. MK256, a potent, selective, and orally available CDK8 inhibitor was developed to target AML. We sought to examine the anticancer effect of MK256 on AML. In CD34+/CD38- leukemia stem cells, we found that MK256 induced differentiation and maturation. Treatment of MK256 inhibited proliferation of AML cell lines. Further studies of the inhibitory effect suggested that MK256 not only downregulated phosphorylated STAT1(S727) and STAT5(S726), but also lowered mRNA expressions of MCL-1 and CCL2 in AML cell lines. Efficacy of MK256 was shown in MOLM-14 xenograft models, and the inhibitory effect on phosphorylated STAT1(S727) and STAT5(S726) with treatment of MK256 was observed in vivo. Pharmacologic dynamics study of MK256 in MOLM-14 xenograft models showed dose-dependent inhibition of the STAT pathway. Both in vitro and in vivo studies suggested that MK256 could effectively downregulate the STAT pathway. In vitro ADME, pharmacological kinetics, and toxicity of MK256 were profiled to evaluate the drug properties of MK256. Our results show that MK256 is a novel CDK8 inhibitor with a desirable efficacy and safety profile and has great potential to be a promising drug candidate for AML through regulating the STAT pathway.

Cyclin-dependent kinase 7 (CDK7) is a protein kinase that plays a major role in transcription initiation. Yes-associated protein (YAP) is a main effector of the Hippo/YAP signalling pathway. Here, we investigated the role of CDK7 on YAP regulation in human malignant pleural mesothelioma (MPM). We found that in microarray samples of human MPM tissue, immunohistochemistry staining showed correlation between the expression level of CDK7 and YAP (n = 70, r = .513). In MPM cells, CDK7 expression level was significantly correlated with GTIIC reporter activity (r = .886, P = .019). Inhibition of CDK7 by siRNA decreased the YAP protein level and the GTIIC reporter activity in the MPM cell lines 211H, H290 and H2052. Degradation of the YAP protein was accelerated after CDK7 knockdown in 211H, H290 and H2052 cells. Inhibition of CDK7 reduced tumour cell migration and invasion, as well as tumorsphere formation ability. Restoration of the CDK7 gene rescued the YAP protein level and GTIIC reporter activity after siRNA knockdown in 211H and H2052 cells. Finally, we performed a co-immunoprecipitation analysis using an anti-YAP antibody and captured the CDK7 protein in 211H cells. Our results suggest that CDK7 inhibition reduces the YAP protein level by promoting its degradation and suppresses the migration and invasion of MPM cells. Cyclin-dependent kinase 7 may be a promising therapeutic target for MPM.

Human non‑small cell lung cancer (NSCLC) is associated with an extremely poor prognosis especially for the 40% of patients who develop brain metastasis, and few treatment strategies exist. Cucurbitacin E (CuE), an oxygenated tetracyclic triterpenoid isolated from plants particularly of the family Cucurbitaceae, has shown anti‑tumorigenic properties in several types of cancer, yet the mechanism remains unclear. Yes‑associated protein (YAP), a main mediator of the Hippo signaling pathway, promotes tumorigenesis, drug resistance and metastasis in human NSCLC. The present study was designed to ascertain whether CuE inhibits YAP and its downstream gene expression in the human NSCLC cell lines H2030‑BrM3 (K‑rasG12C mutation) and PC9‑BrM3 (EGFRΔexon19 mutation), which have high potential for brain metastasis. The efficacy of CuE in suppressing brain metastasis of H2030‑BrM3 cells in a murine model was also investigated. It was found that after CuE treatment in H2030‑BrM3 and PC9‑BrM3 cells, YAP protein expression was decreased, and YAP signaling GTIIC reporter activity and expression of the downstream genes CTGF and CYR61 were significantly (P

Malignant pleural mesothelioma (MPM) is an aggressive cancer for which more effective treatments are needed. In this study, strong to moderate staining of MET and ERK5 was detected in 67.1 and 48% of the analyzed 73 human mesothelioma tumors, and significant correlation of MET and ERK5 expression was identified (P

Although oncogene-targeted therapy often elicits profound initial tumor responses in patients, responses are generally incomplete because some tumor cells survive initial therapy as residual disease that enables eventual acquired resistance. The mechanisms underlying tumor cell adaptation and survival during initial therapy are incompletely understood. Here, through the study of EGFR mutant lung adenocarcinoma, we show that NF-κB signaling is rapidly engaged upon initial EGFR inhibitor treatment to promote tumor cell survival and residual disease. EGFR oncogene inhibition induced an EGFR-TRAF2-RIP1-IKK complex that stimulated an NF-κB-mediated transcriptional survival program. The direct NF-κB inhibitor PBS-1086 suppressed this adaptive survival program and increased the magnitude and duration of initial EGFR inhibitor response in multiple NSCLC models, including a patient-derived xenograft. These findings unveil NF-κB activation as a critical adaptive survival mechanism engaged by EGFR oncogene inhibition and provide rationale for EGFR and NF-κB co-inhibition to eliminate residual disease and enhance patient responses.

BackgroundCasein kinase 2 (CK2) is involved in various cellular events such as proliferation, apoptosis, and the cell cycle. CK2 overexpression is associated with multiple human cancers and may therefore be a promising target for cancer therapy. To identity novel classes of inhibitors for CK2, we screened a natural product library obtained from National Cancer Institute.MethodsThe quantitative luminescent kinase assay ADP-Glo™ was used to screen CK2 inhibitors from the natural product library. The same assay was used to determine cell-free dose-dependent response of CK2 inhibitors and conduct a kinetic study. Docking was performed to predict the binding patterns of selected CK2 inhibitors. Western blot analysis was used to evaluate Akt phosphorylation specific to CK2 and apoptosis effect. The cell viability assay CellTiter-Glo(®) was used to evaluate the inhibition effects of CK2 inhibitors on cancer cells.ResultsWe identified coumestrol as a novel reversible ATP competitive CK2 inhibitor with an IC(50) value of 228 nM. Coumestrol is a plant-derived compound that belongs to the class of phytoestrogens, natural compounds that mimic the biological activity of estrogens. In our study, coumestrol showed high selectivity among 13 kinases. The hydrogen bonds formed between coumestrol and the amino acids in the ATP binding site were first reviewed by a molecular docking study that suggested a possible interaction of coumestrol with the hinge region of ATP site of CK2. In addition, coumestrol inhibited cancer cell growth partially through down-regulation of CK2-specific Akt phosphorylation. Finally, coumestrol exerted strong inhibition effects on the growth of three cancer cell lines.ConclusionOur study shows that coumestrol, a novel ATP competitive and cell permeable CK2 inhibitor with submicromolar IC(50), had inhibition effects on the growth of three cancer cell lines and may represent a promising class of CK2 inhibitors.

BackgroundCasein kinase 2 (CK2) is dysregulated in various human cancers and is a promising target for cancer therapy. To date, there is no small molecular CK2 inhibitor in clinical trial yet. With the aim to identify novel CK2 inhibitors, we screened a natural product library.MethodsWe adopted cell-based proliferation and CK2 kinase assays to screen CK2 inhibitors from a natural compound library. Dose-dependent response of CK2 inhibitors in vitro was determined by a radioisotope kinase assay. Western blot analysis was used to evaluate down stream Akt phosphorylation and apoptosis. Apoptosis was also evaluated by annexin-V/propidium iodide (PI) labeling method using flow cytometry. Inhibition effects of CK2 inhibitors on the growth of cancer and normal cells were evaluated by cell proliferation and viability assays.ResultsHematein was identified as a novel CK2 inhibitor that is highly selective among a panel of kinases. It appears to be an ATP non-competitive and partially reversible CK2 inhibitor with an IC50 value of 0.55 muM. In addition, hematein inhibited cancer cell growth partially through down-regulation of Akt phosphorylation and induced apoptosis in these cells. Furthermore, hematein exerted stronger inhibition effects on the growth of cancer cells than in normal cells.ConclusionIn this study, we showed that hematein is a novel selective and cell permeable small molecule CK2 inhibitor. Hematein showed stronger growth inhibition effects to cancer cells when compared to normal cells. This compound may represent a promising class of CK2 inhibitors.

Background: Casein kinase 2 (CK2) is involved in various cellular events such as proliferation, apoptosis, and the cell cycle. CK2 overexpression is associated with multiple human cancers and may therefore be a promising target for cancer therapy. To identity novel classes of inhibitors for CK2, we screened a natural product library obtained from National Cancer Institute. Methods: The quantitative luminescent kinase assay ADP-Glo™ was used to screen CK2 inhibitors from the natural product library. The same assay was used to determine cell-free dose-dependent response of CK2 inhibitors and conduct a kinetic study. Docking was performed to predict the binding patterns of selected CK2 inhibitors. Western blot analysis was used to evaluate Akt phosphorylation specific to CK2 and apoptosis effect. The cell viability assay CellTiter-Glo® was used to evaluate the inhibition effects of CK2 inhibitors on cancer cells. Results: We identified coumestrol as a novel reversible ATP competitive CK2 inhibitor with an IC50 value of 228 nM. Coumestrol is a plant-derived compound that belongs to the class of phytoestrogens, natural compounds that mimic the biological activity of estrogens. In our study, coumestrol showed high selectivity among 13 kinases. The hydrogen bonds formed between coumestrol and the amino acids in the ATP binding site were first reviewed by a molecular docking study that suggested a possible interaction of coumestrol with the hinge region of ATP site of CK2. In addition, coumestrol inhibited cancer cell growth partially through down-regulation of CK2-specific Akt phosphorylation. Finally, coumestrol exerted strong inhibition effects on the growth of three cancer cell lines. Conclusion: Our study shows that coumestrol, a novel ATP competitive and cell permeable CK2 inhibitor with submicromolar IC50, had inhibition effects on the growth of three cancer cell lines and may represent a promising class of CK2 inhibitors. [ABSTRACT FROM AUTHOR]

Background: Casein kinase 2 (CK2) is dysregulated in various human cancers and is a promising target for cancer therapy. To date, there is no small molecular CK2 inhibitor in clinical trial yet. With the aim to identify novel CK2 inhibitors, we screened a natural product library. Methods: We adopted cell-based proliferation and CK2 kinase assays to screen CK2 inhibitors from a natural compound library. Dose-dependent response of CK2 inhibitors in vitro was determined by a radioisotope kinase assay. Western blot analysis was used to evaluate down stream Akt phosphorylation and apoptosis. Apoptosis was also evaluated by annexin-V/propidium iodide (PI) labeling method using flow cytometry. Inhibition effects of CK2 inhibitors on the growth of cancer and normal cells were evaluated by cell proliferation and viability assays. Results: Hematein was identified as a novel CK2 inhibitor that is highly selective among a panel of kinases. It appears to be an ATP non-competitive and partially reversible CK2 inhibitor with an IC50 value of 0.55 µM. In addition, hematein inhibited cancer cell growth partially through down-regulation of Akt phosphorylation and induced apoptosis in these cells. Furthermore, hematein exerted stronger inhibition effects on the growth of cancer cells than in normal cells. Conclusion: In this study, we showed that hematein is a novel selective and cell permeable small molecule CK2 inhibitor. Hematein showed stronger growth inhibition effects to cancer cells when compared to normal cells. This compound may represent a promising class of CK2 inhibitors. [ABSTRACT FROM AUTHOR]

Aberrant Wnt signaling, mainly through mutations of APC and in some cases of CTNNB1 or AXIN2, has been found in the majority of colorectal cancers. Recently, frequent promoter hypermethylation was identified to cause silencing of the secreted frizzled-related protein (sFRP) family in colorectal cancer. Restoration of sFRP in colorectal cancer cells attenuates Wnt signaling even in the presence of downstream mutations. Here we show that Wnt inhibitory factor-1 (WIF-1), a different secreted antagonist of Wnt signaling, is also silenced by promoter hypermethylation in colorectal cancer cells. Restoration of WIF-1 function, Wnt-1 siRNA, or a monoclonal anti-Wnt-1 antibody that we developed attenuates Wnt-1 signaling and induces significant apoptosis in these cells containing downstream mutations and expressing Wnt-1. In addition, this monoclonal anti-Wnt-1 antibody showed synergistic effects with docetaxel in treating these colorectal cancer cells and great efficacy in treating primary colorectal cancer cultures freshly prepared from patients. Therefore, our data support the hypothesis that constitutive Wnt signaling may be required to complement downstream mutations in the evolution of colorectal cancer. Furthermore, our results suggest that blockade of the Wnt signal may have a therapeutic role in the treatment of colorectal cancer.Oncogene (2005) 24, 3054-3058. doi:10.1038/sj.onc.1208511 Published online 14 February 2005 [ABSTRACT FROM AUTHOR]

Secreted frizzled-related proteins (sFRPs) comprise a family of five secreted glycoproteins that antagonize Wnt signaling. Aberrant activation and upregulation of the Wnt pathway is a key feature of many cancers. Thus, role of sFRP as a negative regulator of Wnt signaling may have important implications in tumorigenesis, and its downregulation has been correlated with human cancers. Recently, we reported Wnt signaling and dishevelled (Dvl) overexpression in malignant pleural mesothelioma (MM). Here, we report significant transcriptional downregulation of the SFRP gene family in MM primary tissues and cell lines as well as several other cancer cell lines (breast, lung, glioma, and cervical) compared to normal cells. One or more SFRPs were downregulated in approximately 85%(18 of 21) of primary MM tumor specimens compared to normal pleural tissue. Eight of the nine cancer cell lines we examined showed silencing of the SFRP family. Methylation-specific PCR (MSP) analysis showed that SFRP1, SFRP4, and SFRP5 gene promoters are frequently methylated in MM primary tissue (>80%). Furthermore, transfection of the SFRP gene construct into MM cell lines lacking SFRP expression resulted in apoptosis and growth suppression. Our results suggest that methylation silencing of SFRPs may be one of the important mechanisms of aberrant Wnt signaling activation in MM.Oncogene (2004) 23, 6672-6676. doi:10.1038/sj.onc.1207881 Published online 28 June 2004 [ABSTRACT FROM AUTHOR]