The small molecule curcumin analog FLLL32 induces apoptosis in melanoma cells via STAT3 inhibition and retains the cellular response to cytokines with anti-tumor activity

Background

We characterized the biologic effects of a novel small molecule STAT3 pathway inhibitor that is derived from the natural product curcumin. We hypothesized this lead compound would specifically inhibit the STAT3 signaling pathway to induce apoptosis in melanoma cells.

Results

FLLL32 specifically reduced STAT3 phosphorylation at Tyr705 (pSTAT3) and induced apoptosis at micromolar amounts in human melanoma cell lines and primary melanoma cultures as determined by annexin V/propidium iodide staining and immunoblot analysis. FLLL32 treatment reduced expression of STAT3-target genes, induced caspase-dependent apoptosis, and reduced mitochondrial membrane potential. FLLL32 displayed specificity for STAT3 over other homologous STAT proteins. In contrast to other STAT3 pathway inhibitors (WP1066, JSI-124, Stattic), FLLL32 did not abrogate IFN-γ-induced pSTAT1 or downstream STAT1-mediated gene expression as determined by Real Time PCR. In addition, FLLL32 did not adversely affect the function or viability of immune cells from normal donors. In peripheral blood mononuclear cells (PBMCs), FLLL32 inhibited IL-6-induced pSTAT3 but did not reduce signaling in response to immunostimulatory cytokines (IFN-γ, IL 2). Treatment of PBMCs or natural killer (NK) cells with FLLL32 also did not decrease viability or granzyme b and IFN-γ production when cultured with K562 targets as compared to vehicle (DMSO).

Conclusions

These data suggest that FLLL32 represents a lead compound that could serve as a platform for further optimization to develop improved STAT3 specific inhibitors for melanoma therapy.

Inhibition of STAT3 signaling blocks the anti-apoptotic activity of IL-6 in human liver cancer cells

Interleukin-6 (IL-6) is a multifunctional cytokine, which may block apoptosis during inflammation to protect cells under very toxic conditions. However, IL-6 also activates STAT3 in many types of human cancer. Recent studies demonstrate that high levels of IL-6 are associated with hepatocellular carcinoma, the most common type of liver cancer. Here we reported that IL-6 promoted survival of human liver cancer cells through activating STAT3 in response to doxorubicin treatment. Endogenous IL-6 levels in SNU-449 cells were higher than in Hep3B cells. Meanwhile, SNU-449 cells were more resistant to doxorubicin than Hep3B cells. Addition of IL-6 induced STAT3 activation in Hep3B cells and led to protection against doxorubicin. In contrast, neutralizing IL-6 with anti-IL-6 antibody decreased survival of SNU-449 cells in response to doxorubicin. To elucidate the mechanism of the anti-apoptotic function of IL-6, we investigated if STAT3 mediated this drug resistance. Targeting STAT3 with STAT3 siRNA reduced the protection of IL-6 against doxorubicin-induced apoptosis, indicating that STAT3 signaling contributed to the anti-apoptotic effect of IL-6. Moreover, we further explored if a STAT3 small molecule inhibitor could abolish this anti-apoptotic effect. LLL12, a STAT3 small molecule inhibitor, blocked IL-6-induced STAT3 phosphorylation, resulting in attenuation of the anti-apoptotic activity of IL-6. Finally, neutralization of endogenous IL-6 with anti-IL-6 antibody or blockade of STAT3 with LLL12 lowered the recovery in SNU-449 cells after doxorubicin treatment. Therefore, our results demonstrated that targeting STAT3 signaling could interrupt the anti-apoptotic function of IL-6 in human liver cancer cells.

Abstract 2275: A novel small molecule, LLL12, inhibits IL-6 induced STAT3 phosphorylation and nuclear translocation

The Signal Transducers and Activators of Transcription (STATs) are a family of cytoplasmic transcription factors, which participate in cellular responses to cytokines and growth factors. STAT3 is found constitutively activated in many types of cancer. Its activation occurs when the Tyrosine residue 705 (Tyr 705) is phosphorylated, monomers form dimmers, and dimmers translocate to the nucleus. Dimerized STAT3 binds to specific DNA response elements and leads to increase the transcription of its downstream genes including angiogenesis, anti-apoptosis, cell cycle progression and proliferation. Therefore, STAT3 is a potential target for cancer therapy. Evidence shows that inhibiting STAT3 using dominant-negative STAT3, antisense oligonucleotides and RNA interference induces tumor cell death.

Interleukin 6 (IL-6) is a multifunctional cytokine and its family also comprises cardiotrophine-1 (CT-1), ciliary neurotrophic factor (CNTF), IL-11, leukaemia inhibitory factor (LIF) and oncostatin M (OSM). IL-6 signals through its receptor sIL-6-6R, gp130, Janus kinases (JAKs). A growing numbers of evidence demonstrate that tumorigenesis caused by STAT3 is mediated by IL-6 signals. Therefore, targeting IL-6/STAT3 signaling should be considered for the treatment of patients with higher levels of IL-6/STAT3 signaling.

We previously reported that a novel small molecule, LLL12, inhibits STAT3 phosphorylation on Tyr 705 in human cancer cells leading to apoptosis in vitro and suppressed tumor growth in vivo. In this study, we showed that LLL12 also inhibited IL-6 induced STAT3 phosphorylation in human liver and pancreactic cancer cell lines. PANC-1 (pancreatic cancer cell) and Hep3B (liver cancer cell line) were treated with different doses of IL-6 for 30 minutes. Immunofluorecent results showed that IL-6 induced STAT3 phosphorylation on Tyr 705 in these two cancer cell lines. Western blot analysis further indicated that the induction of its phosphorylation was IL-6 dose dependent. To determine whether LLL-12 would inhibit IL-6 induced STAT3 phosphorylation, we pre-treated cells with LLL12 for 2 hours followed by IL-6 treatment for 30 minutes and found that STAT3 phosphorylation was suppressed in cells pre-treated with LLL12. LLL12 pre-treatment also blocked STAT3 translocation to the nucleus. To address whether LLL12 pre-treatment would affect STAT1 phosphorylation, we induced STAT1 with IFN-γ and found that LLL12 did not influence STAT1 phosphorylation. To assess the effects of LLL12 on other factors through IL-6/STAT3 pathway, we analyzed JAKs and observed that IL-6 had no effects on JAK1 phosphorylation, but it induced JAK2 phosphorylation. LLL12 pre-treatment did not suppress JAK2 phosphorylation. In conclusion, structure-based small molecule LLL12 selectively inhibited STAT3 phosphorylation induced by IL-6 and may be a potent agent to target IL-6/STAT3 signaling in cancer cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2275.

Abstract 3498: The cytotoxicity and genotoxicity of etoposide and other phenolic and non-phenolic agents in human myeloid leukemia HL-60 cells: role of myeloperoxidase (MPO)

The clinical efficacy of the anticancer agent etoposide (VP-16) is compromised by its ability to cause acute myeloid leukemias (t-AML) associated with MLL gene rearrangements. We proposed previously that myeloperoxidase (MPO) found in myeloid precursors converts the phenolic drug VP-16 to its phenoxyl radical (VP-16-O[[Unable to Display Character: ∙]]), which redox cycles, leading to the generation of reactive oxygen species, oxidative DNA damage linked to DNA topoisomerase II (topo II)-mediated strand cleavage, and resultant recombination events causal for t-AML. After knockdown with an shRNA for MPO in myeloid leukemia HL-60 cells, MPO activity was reduced to 13% of shRNA controls. In these MPO knockdown cells, VP-16-O[[Unable to Display Character: ∙]] formation and VP-16-induced topo II/DNA covalent complexes were reduced compared to shRNA controls demonstrating that VP-16 activity was, in part, dependent on MPO. MPO can also oxidize VP-16 to its ortho-quinone metabolite which is subsequently inactivated by conjugation with glutathione. The cytotoxicities of VP-16, curcumin (a phenolic agent), and a curcumin analog (FLLL-10) were increased in MPO knockdown cells compared to shRNA controls. Podophyllotoxin, the non-phenolic VP-16 parental compound, was equally cytotoxic in MPO knockdown and control cells. Additionally, the cytotoxicity of hydrogen peroxide, an MPO co-substrate, was unaffected by MPO levels. Results indicate that MPO converts VP-16 to a pro-oxidant, which leads to genotoxicity, while simultaneously protecting cells from drug-induced cytotoxicity likely by glutathione conjugation to VP-16 ortho-quinone. The combined results suggest a mechanism by which MPO-containing myeloid progenitor cells can be relatively protected against VP-16-induced apoptosis/cytotoxicity while suffering increased genotoxic and recombinogenic insults responsible for leukemogenesis. Support: NIH CA090787.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3498.

Abstract 4296: STAT3 is required for proliferation and tumor growth of breast cancer stem cells

Breast cancer is the leading type of cancer affecting women. It is estimated that breast cancer accounts for over a quarter of all newly diagnosed cancer cases in women. Despite advances in chemotherapy and hormonal treatment, at the present time, metastatic breast cancer remains an incurable disease. Although a large number of chemotherapeutic agents have been developed that are able to cause the regression of metastatic breast cancers, these tumors almost always recur following chemotherapy treatment. It is possible that breast cancer stem cells or breast cancer initiating cells are responsible for the drug-resistance, metastasis, and recurrence of cancer. Constitutive activation of Signal Transducers and Activators of Transcription 3 (STAT3) signaling is frequently detected in many types of cancers, including breast cancer, and has emerged as an attractive molecular target for cancer treatment. However, whether or not STAT3 is activated in breast cancer stem cells and what role STAT3 signaling plays in cancer stem cells is still unknown. If STAT3 is activated in breast cancer stem cells, targeting STAT3 may offer a promising opportunity to eliminate breast cancer stem cells and prevent the recurrence of cancer. We examined STAT3 activation in breast cancer stem cells, which are characterized by an aldehyde dehydrogenase (ALDH)-positive (ALDH+) and ALDH+/CD44+/CD24− subpopulations. Interestingly, we observed that the ALDH+ and ALDH+/CD44+/CD24− subpopulations of breast cancer cells expressed higher levels of phosphorylated STAT3, an active form of STAT3, as compared to the ALDH− and ALDH−/CD44+/CD24+ subpopulations and un-separated breast cancer cells, suggesting that STAT3 is activated in breast cancer stem cells. We also demonstrated that a novel STAT3 inhibitor, LLL12, inhibited STAT3 phosphorylation, cell viability, STAT3 downstream target gene expression, and induced apoptosis in breast cancer stem cells. In addition, the STAT3 inhibitors Stattic and LLL12 inhibited the tumorsphere forming capacity of breast cancer stem cells. Furthermore, in a mouse tumor model using breast cancer stem cells, we demonstrated that LLL12 can suppress tumor growth in vivo. This is the first report to demonstrate that persistent STAT3 phosphorylation is expressed in breast cancer stem cells and that this subpopulation of breast cancer stem cells is sensitive to STAT3 inhibitors. Our results suggest that STAT3 is a novel therapeutic target in breast cancer stem cells and inhibition of activated STAT3 in cancer stem cells may offer a more effective treatment for breast cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4296.

Abstract 4502: Synthesis and evaluation of curcumin-like compounds as inhibitors of the JAK/STAT pathway in cancer

Curcumin is an attractive lead compound for drug discovery and development. It displays a range of remarkable and diverse biological activities due to its interaction with numerous biological targets including the receptor tyrosine kinase Janus Kinase 2 (JAK2) which transduces cytokine and growth factor mediated signals by activating signal transducer and activator of transcription 3 (STAT3). The significant role of JAK-STAT pathway activation in the development, progression, and survival of cancer has been widely recognized since the 1980s. Based on our interest in developing more potent curcumin analogs which act as inhibitors of the JAK-STAT pathway we synthesized a series of monoketone curcumin analogs that bear a strong structural resemblance to AG490 and WP1066; known synthetic small molecule inhibitors of JAK2. A thorough investigation of the SAR of these compounds was pursued to elucidate which parts of the molecules are essential for the anti-proliferative activity. Thus hybrid molecules containing structural motifs found in all three classes of compounds were synthesized and screened using breast, prostate and colon cancer cell lines. Enzyme-linked immunosorbent assay (ELISA) measuring the relative amount of STAT3 phosphorylation was utilized to determine whether the anti-proliferative activity of these compounds was directly related to inhibition of the JAK-STAT pathway, and therefore whether these three classes of compounds exhibit similar cytotoxic mechanisms of action. Our results showed that although the monoketone curcumin analogs displayed potent cytotoxicity; they failed to inhibit STAT3 phosphorylation. The WP1066 analogs also showed potent cytotoxicity correlating directly to STAT3 inhibition. The pyridine and the halogen at the C3 position of the pyridine ring are essential for activity and appear to have a synergistic effect. Longer aliphatic chains at the benzylic position enhanced the cytotoxic activity and aromatic substitution usually led to a decrease in activity. Different structural modifications of the AG490 analogs by protection of the catechol moiety and/or changing the relative position of the substituents did not result in remarkable change in cytotoxic activity. We concluded that although the monoketone curcumin analogs bear remarkable structural resemblance to WP1066 and AG490, they do not inhibit the JAK-STAT pathway and may have a different anti-proliferative mechanism of action.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4502.

Novel STAT3 phosphorylation inhibitors exhibit potent growth-suppressive activity in pancreatic and breast cancer cells

The constitutive activation of signal transducer and activator of transcription 3 (STAT3) is frequently detected in most types of human cancer where it plays important roles in survival, drug resistance, angiogenesis, and other functions. Targeting constitutive STAT3 signaling is thus an attractive therapeutic approach for these cancers. We have recently developed novel small-molecule STAT3 inhibitors, known as FLLL31 and FLLL32, which are derived from curcumin (the primary bioactive compound of turmeric). These compounds are designed to bind selectively to Janus kinase 2 and the STAT3 Src homology-2 domain, which serve crucial roles in STAT3 dimerization and signal transduction. Here we show that FLLL31 and FLLL32 are effective inhibitors of STAT3 phosphorylation, DNA-binding activity, and transactivation in vitro, leading to the impediment of multiple oncogenic processes and the induction of apoptosis in pancreatic and breast cancer cell lines. FLLL31 and FLLL32 also inhibit colony formation in soft agar and cell invasion and exhibit synergy with the anticancer drug doxorubicin against breast cancer cells. In addition, we show that FLLL32 can inhibit the induction of STAT3 phosphorylation by IFNalpha and interleukin-6 in breast cancer cells. We also show that administration of FLLL32 can inhibit tumor growth and vascularity in chicken embryo xenografts as well as substantially reduce tumor volumes in mouse xenografts. Our findings highlight the potential of these new compounds and their efficacy in targeting pancreatic and breast cancers that exhibit constitutive STAT3 signaling.

Abstract B95: A novel small molecule, LLL12 inhibits STAT3 phosphorylation and activities and exhibits potent growth suppressive activity in human hepatocellular carcinoma cells

Hepatocellular carcinoma is a major worldwide public health problem, and the third most frequent cause of cancer deaths after lung and stomach cancers. Hepatocellular carcinoma is a highly malignant tumor type with average survival rates that are currently less than 1 year following diagnosis. The etiology of hepatocellular carcinoma is still not well understood but involves a multi-step process of signaling protein dysregulation, which includes STAT3. The constitutive activation of STAT3 is frequently detected in clinical incidences of hepatocellular carcinoma and in more than 50% of human hepatocellular carcinoma cell lines but not in normal human hepatocytes. Constitutive STAT3 signaling contributes to hepatocellular carcinoma progression by promoting angiogenesis, survival, metastasis, and growth of hepatocellular carcinoma cells. Recent evidence suggests that the blockade of aberrant STAT3 signal pathway can be exploited as a therapeutic strategy for hepatocellular carcinoma. We have developed a novel small molecular STAT3 inhibitor LLL12 based on computer-aided rational design, which inhibits STAT3 activity by binding to its Src homology 2 (SH2) domain. LLL12 can inhibit STAT3 tyrosine 705 phosphroylation, STAT3 DNA binding activitivies. and prevent STAT translocation into the nucleus, thus decrease the transcription of target genes. And LLL12 also can inhibit IL-6 induced STAT3 phorsphorylation in Hep3B hepatocellular carcinoma cell. Our previous data show it can inhibit breast cancer (MDA-MB231 cells), brain tumor (U87 cells), and pancreatic cancer (PANC-1 cells) in vitro and in vivo. In this study, we report that LLL12 can selectively inhibit proliferation and induce apoptosis in SNU398, SNU387, Hep3B, and SNU449 hepatocellular carcinoma cells in vitro. Furthermore, the LLL12 can significantly inhibit tumor growth of SNU398 hepatocellular carcinoma cell line xenograft in nude mice at the dose of 5mg/kg. Collectively, our results show LLL12 could be used as a targeted drug candidate to target STAT3 for chemoprevention or treatment of Hepatocellular carcinoma in human.

Citation Information: Cancer Prev Res 2010;3(1 Suppl):B95.

Abstract A54: STAT3 as a novel therapeutic target in human breast cancer stem cells

The American Cancer Society estimates that over 200,000 new cases of invasive breast cancer and over 40,000 deaths are expected among women in United States each year. Despite advances in chemotherapy and hormonal treatment, at the present time, metastatic breast cancer remains an incurable disease. Although a large number of chemotherapeutic agents have been developed that are able to cause the regression of metastatic breast cancers, these tumors almost always recur following chemotherapy treatment. It is possible that breast cancer stem cells or breast cancer initiating cells are responsible for the drug-resistance, metastasis, and recurrence of cancer. Constitutive activation of Signal Transducers and Activators of Transcription 3 (STAT3) signaling is frequently detected in many types of cancers, including breast cancer, and has emerged as an attractive molecular target for cancer treatment. However, whether or not STAT3 is activated in breast cancer stem cells and what role STAT3 signaling plays in cancer stem cells is still unknown. If STAT3 is activated in breast cancer stem cells, targeting STAT3 may offer a promising opportunity to eliminate breast cancer stem cells and prevent the recurrence of cancer. We examined STAT3 activation in breast cancer stem cells, which are characterized by an aldehyde dehydrogenase (ALDH)-positive subpopulation. Interestingly, we observed that the ALDH-positive subpopulation of breast cancer cells expressed higher levels of phosphorylated STAT3, an active form of STAT3, as compared to the ALDH-negative subpopulation and un-separated breast cancer cells, suggesting that STAT3 is activated in breast cancer stem cells. We also demonstrated that a novel STAT3 inhibitor, LLL12, inhibited STAT3 phosphorylation, cell viability, STAT3 downstream target gene expression, and induced apoptosis in breast cancer stem cells. In addition, the STAT3 inhibitors Stattic and LLL12 reduced ALDH-positive subpopulation and inhibited their tumorsphere forming capacity. Furthermore, in our pilot study in a mouse tumor model using breast cancer stem cells, we demonstrated that LLL12 can suppress tumor growth in vivo. This is the first report to demonstrate that persistent STAT3 phosphorylation is expressed in breast cancer stem cells and that this subpopulation of breast cancer stem cells is sensitive to STAT3 inhibitors. Our results suggest that STAT3 is a novel therapeutic target in breast cancer stem cells and inhibition of activated STAT3 in cancer stem cells may offer a more effective treatment for breast cancer.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A54.

New curcumin analogues exhibit enhanced growth-suppressive activity and inhibit AKT and signal transducer and activator of transcription 3 phosphorylation in breast and prostate cancer cells

Curcumin, the active component of turmeric, has been shown to protect against carcinogenesis and prevent tumor development in cancer. To enhance its potency, we tested the efficacy of synthetic curcumin analogues, known as FLLL11 and FLLL12, in cancer cells. We examined the impact of FLLL11 and FLLL12 on cell viability in eight different breast and prostate cancer cell lines. FLLL11 and FLLL12 (IC(50) values 0.3-5.7 and 0.3-3.8 micromol/L, respectively) were substantially more potent than curcumin (IC(50) values between 14.4-50 micromol/L). FLLL11 and FLLL12 were also found to inhibit AKT phosphorylation and downregulate the expression of HER2/neu. In addition, we demonstrate for the first time that FLLL11 and FLLL12 inhibit phosphorylation of signal transducer and activator of transcription (STAT) 3, an oncogene frequently found to be persistently active in many cancer types. The inhibition of STAT3 signaling was confirmed by the inhibition of STAT3 DNA binding and STAT3 transcriptional activity. Furthermore, FLLL11 and FLLL12 were more effective than curcumin in inhibiting cell migration and colony formation in soft agar as well as inducing apoptosis in cancer cells. These results indicate that FLLL11 and FLLL12 exhibit more potent activities than curcumin on the inhibition of STAT3, AKT, and HER-2/neu, as well as inhibit cancer cell growth and migration, and may thus have translational potential as chemopreventive or therapeutic agents for breast and prostate cancers.

New structural analogues of curcumin exhibit potent growth suppressive activity in human colorectal carcinoma cells

BACKGROUND

Colorectal carcinoma is one of the major causes of morbidity and mortality in the Western World. Novel therapeutic approaches are needed for colorectal carcinoma. Curcumin, the active component and yellow pigment of turmeric, has been reported to have several anti-cancer activities including anti-proliferation, anti-invasion, and anti-angiogenesis. Clinical trials have suggested that curcumin may serve as a potential preventive or therapeutic agent for colorectal cancer.

METHODS

We compared the inhibitory effects of curcumin and novel structural analogues, GO-Y030, FLLL-11, and FLLL-12, in three independent human colorectal cancer cell lines, SW480, HT-29, and HCT116. MTT cell viability assay was used to examine the cell viability/proliferation and western blots were used to determine the level of PARP cleavages. Half-Maximal inhibitory concentrations (IC50) were calculated using Sigma Plot 9.0 software.

RESULTS

Curcumin inhibited cell viability in all three of the human colorectal cancer cell lines studied with IC50 values ranging between 10.26 microM and 13.31 microM. GO-Y030, FLLL-11, and FLLL-12 were more potent than curcumin in the inhibition of cell viability in these three human colorectal cancer cell lines with IC50 values ranging between 0.51 microM and 4.48 microM. In addition, FLLL-11 and FLLL-12 exhibit low toxicity to WI-38 normal human lung fibroblasts with an IC-50 value greater than 1,000 microM. GO-Y030, FLLL-11, and FLLL-12 are also more potent than curcumin in the induction of apoptosis, as evidenced by cleaved PARP and cleaved caspase-3 in all three human colorectal cancer cell lines studied.

CONCLUSION

The results indicate that the three curcumin analogues studied exhibit more potent inhibitory activity than curcumin in human colorectal cancer cells. Thus, they may have translational potential as chemopreventive or therapeutic agents for colorectal carcinoma.

Anti-angiogenic and vascular disrupting effects of C9, a new microtubule-depolymerizing agent

BACKGROUND AND PURPOSE

The critical role of blood supply in the growth of solid tumours makes blood vessels an ideal target for anti-tumour drug discovery. The anti-angiogenic and vascular disrupting activities of C9, a newly synthesized microtubule-depolymerizing agent, were investigated with several in vitro and in vivo models. Possible mechanisms involved in its activity were also assessed.

EXPERIMENTAL APPROACH

Microtubule-depolymerizing actions were assessed by surface plasmon resonance binding, competitive inhibition and cytoskeleton immunofluorescence. Anti-angiogenic and vascular disrupting activities were tested on proliferation, migration, tube formation with human umbilical vein endothelial cells, and in rat aortic ring, chick chorioallantoic membrane and Matrigel plug assays. Western blots and Rho activation assays were employed to examine the role of Raf-MEK-ERK (mitogen-activated ERK kinase, extracellular signal-regulated kinase) and Rho/Rho kinase signalling.

KEY RESULTS

C9 inhibited proliferation, migration and tube formation of endothelial cells and inhibited angiogenesis in aortic ring and chick chorioallantoic membrane assays. C9 induced disassembly of microtubules in endothelial cells and down-regulated Raf-MEK-ERK signalling activated by pro-angiogenic factors. In addition, C9 disrupted capillary-like networks and newly formed vessels in vitro and rapidly decreased perfusion of neovasculature in vivo. Endothelial cell contraction and membrane blebbing induced by C9 in neovasculature was dependent on the Rho/Rho kinase pathway.

CONCLUSIONS AND IMPLICATIONS

Anti-angiogenic and vascular disruption by C9 was associated with changes in morphology and function of endothelial cells, involving the Raf-MEK-ERK and Rho/Rho kinase signalling pathways. These findings strongly suggest that C9 is a new microtubule-binding agent that could effectively target tumour vasculature.

Characterization of STAT3 activation and expression in canine and human osteosarcoma

Background

Dysregulation of signal transducer and activator of transcription 3 (STAT3) has been implicated as a key participant in tumor cell survival, proliferation, and metastasis and is often correlated with a more malignant tumor phenotype. STAT3 phosphorylation has been demonstrated in a subset of human osteosarcoma (OSA) tissues and cell lines. OSA in the canine population is known to exhibit a similar clinical behavior and molecular biology when compared to its human counterpart, and is often used as a model for preclinical testing of novel therapeutics. The purpose of this study was to investigate the potential role of STAT3 in canine and human OSA, and to evaluate the biologic activity of a novel small molecule STAT3 inhibitor.

Methods

To examine STAT3 and Src expression in OSA, we performed Western blotting and RT-PCR. OSA cells were treated with either STAT3 siRNA or small molecule Src (SU6656) or STAT3 (LLL3) inhibitors and cell proliferation (CyQUANT), caspase 3/7 activity (ELISA), apoptosis (Western blotting for PARP cleavage) and/or viability (Wst-1) were determined. Additionally, STAT3 DNA binding after treatment was determined using EMSA. Expression of STAT3 targets after treatment was demonstrated with Western blotting, RT-PCR, or gel zymography.

Results

Our data demonstrate that constitutive activation of STAT3 is present in a subset of canine OSA tumors and human and canine cell lines, but not normal canine osteoblasts. In both canine and human OSA cell lines, downregulation of STAT3 activity through inhibition of upstream Src family kinases using SU6656, inhibition of STAT3 DNA binding and transcriptional activities using LLL3, or modulation of STAT3 expression using siRNA, all resulted in decreased cell proliferation and viability, ultimately inducing caspase-3/7 mediated apoptosis in treated cells. Furthermore, inhibition of either Src or STAT3 activity downregulated the expression of survivin, VEGF, and MMP2, all known transcriptional targets of STAT3.

Conclusion

These data suggest that STAT3 activation contributes to the survival and proliferation of human and canine OSA cells, thereby providing a potentially promising target for therapeutic intervention. Future investigational trials of LLL3 in dogs with spontaneous OSA will help to more accurately define the role of STAT3 in the clinical setting.

Modulation of DNA methylation by a sesquiterpene lactone parthenolide

Hypermethylation of 5'-cytosine-guanosine islands of tumor suppressor genes resulting in their silencing has been proposed to be a hallmark of various tumors. Modulation of DNA methylation with DNA methylation inhibitors has been shown to result in cancer cell differentiation or apoptosis and represents a novel strategy for chemotherapy. Currently, effective DNA methylation inhibitors are mainly limited to decitabine and 5-azacytidine, which still show unfavorable toxicity profiles in the clinical setting. Thus, discovery and development of novel hypomethylating agents, with a more favorable toxicity profile, is essential to broaden the spectrum of epigenetic therapy. Parthenolide, the principal bioactive sesquiterpene lactone of feverfew, has been shown to alkylate Cys(38) of p65 to inhibit nuclear factor-kappaB activation and exhibit anti-tumor activity in human malignancies. In this article, we report that parthenolide 1) inhibits DNA methyltransferase 1 (DNMT1) with an IC(50) of 3.5 microM, possibly through alkylation of the proximal thiolate of Cys(1226) of the catalytic domain by its gamma-methylene lactone, and 2) down-regulates DNMT1 expression possibly associated with its SubG(1) cell-cycle arrest or the interruption of transcriptional factor Sp1 binding to the promoter of DNMT1. These dual functions of parthenolide result in the observed in vitro and in vivo global DNA hypomethylation. Furthermore, parthenolide has been shown to reactivate tumor suppressor HIN-1 gene in vitro possibly associated with its promoter hypomethylation. Hence, our study established parthenolide as an effective DNA methylation inhibitor, representing a novel prototype for DNMT1 inhibitor discovery and development from natural structural-diversified sesquiterpene lactones.

Structure-activity relationship studies of curcumin analogues

Two series of curcumin analogues, a total of twenty-four compounds, were synthesized and evaluated. The most potent compound, compound 23, showed potent growth inhibitory activities on both prostate and breast cancer lines with IC(50) values in sub-micromolar range, fifty times more potent than curcumin. Curcumin analogues might be potential anti-tumor agents for breast and prostate cancers.

Microscopic polyarteritis presenting with chest infections and acute appendicitis

We describe a 38-year-old male with antineutrophil cytoplasmic auto-antibody (ANCA) positive microscopic polyarteritis who presented with recurrent chest infections, lung haemorrhage, renal insufficiency and acute appendicitis. Appendectomy was followed by resolution of abdominal symptoms and the surgical specimen revealed vasculitis of the serosal vessels. A renal biopsy was performed because of impaired renal function and this revealed focal necrotising glomerulonephritis with absence of immune deposits. Chest infections were treated with antibiotics resulting in partial clinical response, but pulmonary symptoms relapsed and a complete resolution was achieved only after plasma exchange and the administration of cyclophosphamide. Our observation emphasises the protean manifestations of microscopic polyarteritis and the relationship between ANCA and disease activity.

Inhibitors of NF-κB derived from thalidomide

A series of compounds originally derived from thalidomide were synthesized and evaluated. The most potent compounds in this series, 5HPP-33 and compound 20, inhibited NF-kappaB activation in HeLa cells. Preliminary study indicated that the mechanism of inhibition of NF-kappaB activation is through inhibition of its translocation from the cytoplasm to the nucleus.

Development of keratinocyte growth factor receptor tyrosine kinase inhibitors for the treatment of cancer

BACKGROUND

The mammary glands of adult female animals are remarkably sensitive to keratinocyte growth factor (KGF). KGF acts at the KGF receptor (KGFR) to produce a rapid and profound stimulation of breast cancer cell proliferation and motility. Further, KGF-induced motility in breast cancer cells is mediated via the Erk1/2 signaling pathway. Thus, enhancement of KGF/KGFR signal transduction may be an early step in the metastatic progression of breast cancer. Receptor modeling of KGFR was used to identify selective KGFR tyrosine kinase inhibitor (TKI) molecules with high receptor affinity. The present study describes the synthesis and biological activity of three of the KGFR TKI compounds.

MATERIALS AND METHODS

Computer modeling of the KGFR was used to create a virtual library of compounds that have the potential to bind with high affinity to the KGFR. Three of these compounds were synthesized and tested in this study. The compounds were tested for their ability to inhibit KGF-mediated breast cancer cell proliferation and motility using a culture wounding assay. In addition, the effect of the most potent KGFR TKI compound on the relative density of cell membrane KGFR was measured using immunocytochemistry.

RESULTS

It was observed that the KGFR TKIs decreased KGF-mediated activity as predicted by computer modeling. In addition, the most potent inhibitor also reduced the density of the KGFR on the membrane of the cancer cells.

CONCLUSION

The novel inhibitors identified in this project are selective KGFR inhibitors which appear to reduce the expression of KGFR on cancer cells. These results may lead to the development of a novel class of anticancer agents for the chemoprevention of metastatic cancer development and provide a new approach in the treatment of breast cancer.

Immunohistochemical analysis of steroid sulfatase in human tissues

Steroid sulfatase (EC 3.1.6.2) is an enzyme that removes the sulfate group from 3beta-hydroxysteroid sulfates. This enzyme is best known for its role in estrogen production via the fetal adrenal-placental pathway during pregnancy; however, it also has important functions in other physiological and pathological steroid pathways. The objective of this study was to examine the distribution of steroid sulfatase in normal human tissues and in breast cancers using immunohistochemistry, employing a newly developed steroid sulfatase antibody. A rabbit polyclonal antiserum was generated against a peptide representing a conserved region of the steroid sulfatase protein. In Western blotting experiments using human placental microsomes, this antiserum crossreacted with a 65 kDa protein, the reported size of steroid sulfatase. The antiserum also crossreacted with single protein bands in Western blots of microsomes from two human breast cancer cell lines (MDA-MB-231 and MCF-7) and from rat liver; however, there were some size differences in the immunoreactive bands among tissues. The steroid sulfatase antibody was used in immunohistochemical analyses of individual human tissue slides as well as a human tissue microarray. For single tissues, human placenta and liver showed strong positive staining against the steroid sulfatase antibody. ER+/PR+ breast cancers also showed relatively strong levels of steroid sulfatase immunoreactivity. Normal human breast showed moderate levels of steroid sulfatase immunoreactivity, while ER-/PR- breast cancer showed weak immunoreactivity. This confirms previous reports that steroid sulfatase is higher in hormone-dependent breast cancers. For the tissue microarray, most tissues showed some detectable level of steroid sulfatase immunoreactivity, but there were considerable differences among tissues, with skin, liver and lymph nodes having the highest immunoreactivity and brain tissues having the lowest. These data reveal the utility of immunohistochemistry in evaluation of steroid sulfatase activity among tissues. The newly developed antibody should be useful in studies of both humans and rats.

Synthesis of 4′-Hydroxy-3′-piperidinomethylchalcone Derivatives and Their Cytotoxicity Against PC-3 Cell Lines

A new series of mono Mannich bases of 4'-hydroxychalcones 2a-e carrying a variety of aryl groups was synthesized and the in vitro cytotoxic activities of the new compounds were screened against PC-3 cell lines. Bioactivities of 2a-e, which are reported for the first time in this study, were compared against their precursor 4'-hydroxychalcones 1a-e. Compound 2b was found to be the most potent (IC(50 )= 3.7 microM) among the compounds synthesized. In addition, the compounds 1a-c and 2d showed moderate cytotoxicity. Incorporation of the 3'-piperidinomethyl group in 1b and 1d raised the potency by 1.68 and 2.19 times respectively and, therefore, seemed to be a noteworthy molecular modification. Correlations were noted between cytotoxicity and one or more physiochemical constants of the aryl ring as well as log P values for the compounds 2a-e. The significant improvement of cytotoxicity of 2b, 2d, and 2e against PC-3 cell lines compared with their chalcone precursors suggests that the incorporation of a piperidinomethyl group is a useful molecular modification and further development of these compounds as candidate cytotoxic agents may be warranted.

Evaluation of the cytotoxicity of some mono-mannich bases and their corresponding azine derivatives against androgen-independent prostate cancer cells

Mono-Mannich bases derived from acetophenones, 1-aryl-3-amino- 1 -propanone hydrochlorides (Igl-Ig4), and their corresponding azine derivatives, N, N'-bis(3-amino-l-aryl-propylidene) hydrazine dihydrochlorides (DI-D4), were designed and synthesized as cellular thiol alkylating agents. The aryl portion was replaced by a phenyl group in Ig1, Ig2, Ig3, D1, D2, and D3, and by a p-hydroxyphenyl group in Ig4 and D4. The amine side chain was replaced by a dimethylamine group in Igl, D1, Ig4 and D4, by a piperidine group in Ig2 and D2, and by a morpholine group in Ig3 and D3. The cytotoxic activity of the compounds was tested against the androgen-independent prostate cancer cell line PC-3. The relationship between cytotoxicity and pKa value of the amine group and partition coefficients of the compounds was also investigated. Azine derivative D4 was found to be the most potent among all the compounds tested and the cytotoxicity increased 1.73 fold compared with the mono-Mannich base Ig4 in PC-3 cells. On the other hand, conversion of mono-Mannich bases Igl-Ig3 to their corresponding azine derivatives DI-D3 decreased the cytotoxicity considerably. Substitution of the hydroxyl group at the para position of the aromatic ring in azine derivative D4 increased the cytotoxicity, and a rational explanation in this regard is described in length. The results emerged from this investigation guide the future expansion of these series of compounds.

A novel steroidal selective steroid sulfatase inhibitor KW-2581 inhibits sulfated-estrogen dependent growth of breast cancer cells in vitro and in animal models

We screened a series of 17beta-(N-alkylcarbamoyl)-estra-1,3,5(10)trine-3-O-sulfamate derivatives, and describe here a potent and selective steroid sulfatase (STS) inhibitor with antitumor effects in breast cancer models in vitro and in vivo. In biochemical assays using crude enzymes isolated from recombinant Chinese hamster ovary cells expressing human arylsulfatses (ARSs), one of the best compounds, KW-2581, inhibited STS activity with an IC(50) of 4.0 nM, while > 1000-fold higher concentrations were required to inhibit the other ARSs. The failure to stimulate the growth of MCF-7 human breast cancer cells as well as in uteri in ovariectomized rats indicated the lack of estrogenicity of this compound. In MCF-7 cells transfected with the STS gene, termed MCS-2 cells, KW-2581 inhibited the growth of cells stimulated by estrone sulfate (E1S) but also 5-androstene-3beta, 17beta-diol 3-sulfate (ADIOLS) and dehydroepiandrostenedione 3-sulfate. We found that oral administration of KW-2581 inhibited both E1S- and ADIOLS-stimulated growth of MCS-2 cells in a mouse hollow fiber model. In a nitrosomethylurea-induced rat mammary tumor model, KW-2581 induced regression of E1S-stimulated tumor growth as effectively as tamoxifen or another STS inhibitor, 667 Coumate. Dose-response studies in the same rat model demonstrated that more than 90% inhibition of STS activity in tumors was necessary to induce tumor shrinkage. STS activity in tumors has well correlated with that in leukocytes, suggesting that STS activity in leukocytes could be used as an easily detectable pharmacodynamic marker. These findings demonstrate that KW-2581 is a candidate for development as a therapeutic agent for the treatment of hormone receptors-positive breast cancer.

Inhibition of steroid sulfatase activity and cell proliferation in ZR-75-1 and BT-474 human breast cancer cells by KW-2581 in vitro and in vivo

In the present study, we found that two hormone receptor-positive human breast cancer cell lines, ZR-75-1 and BT-474, naturally expressed steroid sulfatase (STS) protein and had catalytic activity to produce estrone from estrone sulfate (E1S) with a comparable level to those in human breast cancer tissues. E1S at physiological concentrations stimulated the growth of those cells. A novel steroidal STS inhibitor, KW-2581 inhibited the STS activity of ZR-75-1 cells with an IC(50) of 13 nM, a potency equal to or higher than that of the non-steroidal STS inhibitor, 667 COUMATE. The inhibitory effect of KW-2581 was enhanced by pre-incubation with STS enzyme, suggests being irreversible inhibition. KW-2581 inhibited the E1S-stimulated growth of ZR-75-1 cells with an IC(50) of 0.18 nM, but failed to inhibit the growth stimulated by 17beta-estradiol. Expression of E1S-induced progesterone receptors in ZR-75-1 cells was reduced by treatment of KW-2581 at concentrations as low as 0.1 nM. Oral administration of KW-2581 for 4 weeks caused tumor shrinkage in a mouse xenograft model. Tumor STS activity had been completely (>95%) eliminated by 24 hours after the last administration. These findings suggest that KW-2581 has considerable potential for therapeutic development as a novel anti-hormonal drug for treatment of breast cancer.