Survivin: key regulator of mitosis and apoptosis and novel target for cancer therapeutics

Human embryonic stem cell-derived microvascular grafts for cardiac tissue preservation after myocardial infarction

We present use of a synthetic, injectable matrix metalloproteinase (MMP)-responsive, bioactive hydrogel as an in situ forming scaffold to deliver thymosin β4 (Tβ4), a pro-angiogenic and pro-survival factor, along with vascular cells derived from human embryonic stem cells (hESC) in ischemic injuries to the heart in a rat model. The gel was found to substitute the degrading extracellular matrix in the infarcted myocardium of rats and to promote structural organization of native endothelial cells, while some of the delivered hESC-derived vascular cells formed de novo capillaries in the infarct zone. Magnetic resonance imaging (MRI) revealed that the microvascular grafts effectively preserved contractile performance 3 d and 6 wk after myocardial infarction, attenuated left ventricular dilation, and decreased infarct size as compared to infarcted rats treated with PBS injection as a control (3 d ejection fraction, + ∼7%, P < 0.001; 6 wk ejection faction, + ∼12%, P < 0.001). Elevation in vessel density was observed in response to treatment, which may be due in part to elevations in human (donor)-derived cytokines EGF, VEGF and HGF (1 d). Thus, a clinically relevant matrix for dual delivery of vascular cells and drugs may be useful in engineering sustained tissue preservation and potentially regenerating ischemic cardiac tissue.

Survivin multifaceted activity in head and neck carcinoma: current evidence and future therapeutic challenges

CONCLUSIONS

Survivin expression should be studied as a potential hallmark of higher risk oral, oropharyngeal and laryngeal squamous cell carcinomas (SCCs) to develop loco-regional recurrences. These outcomes could have a significant impact on both the treatment modalities and the intensity of post-treatment follow-up. Further investigation is necessary before considering elective neck dissection in patients with laryngeal SCC with high survivin expression.

OBJECTIVES

Functioning simultaneously at cell division and apoptosis inhibition, survivin, a member of the inhibitor of apoptosis proteins family, plays a pivotal role in determining cell survival. Significant over-expression of survivin has been demonstrated in most human malignancies and correlated with more aggressive forms. This review focuses on the attempts to translate survivin biologic properties toward both a diagnostic/prognostic tool and a novel therapeutic target in head and neck SCC (HNSCC).

MATERIALS AND METHODS

An exhaustive review of literature was performed to investigate available evidence about survivin expression, biological role and therapeutic potential in HNSCC.

RESULTS

Multiple evidence indicates that, in HNSCC cell lines, survivin inhibition by gene therapy and by small molecule inhibitors significantly increases the anti-tumour activity of several cytotoxic and other targeted therapies.

MHC-restricted fratricide of human lymphocytes expressing survivin-specific transgenic T cell receptors

The apoptosis inhibitor protein survivin is overexpressed in many tumors, making it a candidate target molecule for various forms of immunotherapy. To explore survivin as a target antigen for adoptive T cell therapy using lymphocytes expressing survivin-specific transgenic T cell receptors (Tg-TCRs), we isolated HLA-A2-allorestricted survivin-specific T cells with high functional avidity. Lymphocytes expressing Tg-TCRs were derived from these T cells and specifically recognized HLA-A2+ survivin+ tumor cells. Surprisingly, HLA-A2+ but not HLA-A2- lymphocytes expressing Tg-TCRs underwent extensive apoptosis over time. This demise was caused by HLA-A2-restricted fratricide that occurred due to survivin expression in lymphocytes, which created ligands for Tg-TCR recognition. Therefore, survivin-specific TCR gene therapy would be limited to application in HLA-A2-mismatched stem cell transplantation. We also noted that lymphocytes that expressed survivin-specific Tg-TCRs killed T cell clones of various specificities derived from HLA-A2+ but not HLA-A2- donors. These results raise a general question regarding the development of cancer vaccines that target proteins that are also expressed in activated lymphocytes, since induction of high-avidity T cells that expand in lymph nodes following vaccination or later accumulate at tumor sites might limit themselves by self-MHC-restricted fratricide while at the same time inadvertently eliminating neighboring T cells of other specificities.

Keratinocyte stem cells: friends and foes

Skin and its appendages provide a protective barrier against the assaults of the environment. To perform its role, epidermis undergoes an ongoing renewal through a balance of proliferation and differentiation/apoptosis called homeostasis. Keratinocyte stem cells reside in a special microenvironment called niche in basal epidermis, adult hair follicle, and sebaceous glands. While a definite marker has yet to be detected, data raised part in humans and part in the mouse system point to a critical role of stem and its progeny transit amplifying cells in epidermal homeostasis. Stem cells are protected from apoptosis and are long resident in adult epidermis. This renders them more prone to be the origin of skin cancer. In this review, we will outline the main features of adult stem cells in mouse and humans and discuss their fate in relation to differentiation, apoptosis, and cancer.

Survivin is not induced by novel taxanes

Taxanes are a critical component of chemotherapy for breast, prostate, lung and other cancers. Initial or acquired tumor resistance to taxanes is therefore one of the most important issues in oncology. Survivin is a prosurvival gene whose expression is a poor prognostic feature. Survivin is induced acutely upon exposure to taxanes and coordinates resistance to taxane-mediated cell death, although the exact mechanism of taxane-mediated survivin induction is not clear. Here, we describe the synthesis of a series of novel taxanes, with modifications on the 7- or 10-position of the taxane backbone, as well as the side chain. We found that the novel taxanes with modifications at the 10-position have robust tubulin binding and tubulin polymerization activity. Gene expression profiling and quantitative PCR of cells treated with the 10-position conjugates reveals that the effect of treatment with a subset of these novel taxanes lacks a gene expression signature, including survivin induction, which is characteristically induced with paclitaxel treatment. Furthermore, we show that this gene expression signature is not due to differences in G2/M arrest. Cell sensitivity studies suggest that the inability to induce survivin is associated with increased drug cytotoxicity and apoptosis. This work suggests that taxanes that effectively bind tubulin need not invariably induce survivin as a mechanism of drug resistance.

Down-modulation of survivin expression and inhibition of tumor growth in vivo by EZN-3042, a locked nucleic acid antisense oligonucleotide

Survivin plays an important role in preventing apoptosis and permitting mitosis, and is highly expressed in various human cancers. EZN-3042 is a locked nucleic acid antisense oligonucleotide (LNA-AsODN) against survivin. We report the effects of EZN-3042 in animal models. In a chemical-induced liver regeneration model, treatment with a mouse homolog of EZN-3042 resulted in 80% down-modulation of survivin mRNA. In A549 and Calu-6 lung xenograft models, treatment with EZN-3042 single agent induced 60% down-modulation of survivin mRNA in tumors and 37-45% tumor growth inhibition (TGI). In Calu-6 model, when EZN-3042 was combined with paclitaxel, an 83% TGI was obtained. EZN-3042 is currently being evaluated in a Phase 1 clinical trial as a single agent and in combination with docetaxel.

Blocking Wnt signaling by SFRP-like molecules inhibits in vivo cell proliferation and tumor growth in cells carrying active β-catenin

Constitutive activation of Wnt/β-catenin signaling in cancer results from mutations in pathway components, which frequently coexist with autocrine Wnt signaling or epigenetic silencing of extracellular Wnt antagonists. Among the extracellular Wnt inhibitors, the secreted frizzled-related proteins (SFRPs) are decoy receptors that contain soluble Wnt-binding frizzled domains. In addition to SFRPs, other endogenous molecules harboring frizzled motifs bind to and inhibit Wnt signaling. One of such molecules is V3Nter, a soluble SFRP-like frizzled polypeptide that binds to Wnt3a and inhibits Wnt signaling and expression of the β-catenin target genes cyclin D1 and c-myc. V3Nter is derived from the cell surface extracellular matrix component collagen XVIII. Here, we used HCT116 human colon cancer cells carrying the ΔS45 activating mutation in one of the alleles of β-catenin to show that V3Nter and SFRP-1 decrease baseline and Wnt3a-induced β-catenin stabilization. Consequently, V3Nter reduces the growth of human colorectal cancer xenografts by specifically controlling cell proliferation and cell cycle progression, without affecting angiogenesis or apoptosis, as shown by decreased [(3)H]-thymidine (in vitro) or BrdU (in vivo) incorporation, clonogenesis assays, cell cycle analysis and magnetic resonance imaging in living mice. Additionally, V3Nter switches off the β-catenin target gene expression signature in vivo. Moreover, experiments with β-catenin allele-targeted cells showed that the ΔS45 β-catenin allele hampers, but does not abrogate, inhibition of Wnt signaling by SFRP-1 or by the SFRP-like frizzled domain. Finally, neither SFRP-1 nor V3Nter affect β-catenin signaling in SW480 cells carrying nonfunctional Adenomatous polyposis coli. Thus, SFRP-1 and the SFRP-like molecule V3Nter can inhibit tumor growth of β-catenin-activated tumor cells in vivo.

The flavonoid quercetin induces cell cycle arrest and mitochondria-mediated apoptosis in human cervical cancer (HeLa) cells through p53 induction and NF-κB inhibition

With increasing use of plant-derived cancer chemotherapeutic agents, exploring the antiproliferative effects of phytochemicals has gained increasing momentum for anticancer drug design. The dietary phytochemical quercetin, modulates several signal transduction pathways associated with cell proliferation and apoptosis. The present study was undertaken to examine the effect of quercetin on cell viability, and to determine the molecular mechanism of quercetin-induced cell death by investigating the expression of Bcl-2 family proteins (Bcl-2, Bcl-xL, Mcl1, Bax, Bad, p-Bad), cytochrome C, Apaf-1, caspases, and survivin as well as the cell cycle regulatory proteins (p53, p21, cyclin D1), and NF-κB family members (p50, p65, IκB, p-IκB-α, IKKβ and ubiquitin ligase) in human cervical cancer (HeLa) cells. The results demonstrate that quercetin suppressed the viability of HeLa cells in a dose-dependent manner by inducing G2/M phase cell cycle arrest and mitochondrial apoptosis through a p53-dependent mechanism. This involved characteristic changes in nuclear morphology, phosphatidylserine externalization, mitochondrial membrane depolarization, modulation of cell cycle regulatory proteins and NF-κB family members, upregulation of proapoptotic Bcl-2 family proteins, cytochrome C, Apaf-1 and caspases, and downregulation of antiapoptotic Bcl-2 proteins and survivin. Quercetin that exerts opposing effects on different signaling networks to inhibit cancer progression is a classic candidate for anticancer drug design.

Transformation-related protein 53 expression in the early mouse embryo compromises preimplantation embryonic development by preventing the formation of a proliferating inner cell mass

The developmental viability of the preimplantation embryo requires the successful formation of a cluster of pluripotent stem cells called the inner cell mass. Development is variably compromised by a range of exogenous stressors (including their production by assisted reproductive technologies). Inbred C57BL/6 strain embryos are particularly susceptible to the stresses associated with embryo culture, whereas hybrid embryos are more resistant, and this is accounted for in part by the overexpression of transformation-related protein 53 in cultured inbred embryos compared with similarly treated hybrid embryos or embryos not subjected to culture. We show here that this loss of viability is a consequence of the Trp53-dependent reduction in the capacity of blastocysts to form a proliferating inner cell mass. Formation of the trophectodermal line was not adversely affected by these stresses.

Induction of growth arrest by miR-542-3p that targets survivin

Survivin is a protein which functions as a mitotic regulator as well as apoptosis inhibitor. In this study, we show that introduction of synthetic miR-542-3p mimetic reduced both mRNA and protein levels of survivin. In A549 cells, luciferase reporter assay revealed that miR-542-3p targeted predicted binding sites in the 3'-untranslated region (3'-UTR) of survivin. We also demonstrate that ectopic expression of miR-542-3p inhibited cell proliferation by inducing Gap 1 (G1) and Gap 2/Mitosis (G2/M) cell cycle arrest. Collectively, these results suggest that survivin is a direct target of miR-542-3p and growth inhibition by miR-542-3p may have a potential utility as an anti-cancer therapy.

Survivin knockdown and concurrent 4-HPR treatment controlled human glioblastoma in vitro and in vivo

Survivin is highly expressed in most cancers, including glioblastoma, and it plays a significant role in inhibiting apoptosis and promoting tumor growth. Treatment of cancer cells with N-(4-hydroxyphenyl) retinamide (4-HPR) induces apoptosis through destabilization of mitochondrial membrane and activation of caspase-mediated apoptotic pathways. We studied the efficacy of a combination of survivin knockdown and 4-HPR treatment to induce apoptosis and inhibit invasion, angiogenesis, and growth of human glioblastomas in vitro and in vivo. Using a plasmid encoding survivin shRNA, we downregulated survivin in glioblastoma U251MG and U118MG cells and simultaneously treated with 1 µM 4-HPR for 48 hours. Cells following treatments were subjected to the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and invasion assays. In vivo angiogenesis and tumor regression studies were performed in nude mice. TUNEL assay demonstrated apoptosis in more than 80% of cells after survivin knockdown and 4-HPR treatment. Matrigel invasion assays demonstrated marked decreases in tumor cell invasion. In vivo angiogenesis studies depicted a remarkable inhibition of neovascularization due to the knockdown of survivin and 4-HPR treatment. Imaging of intracerebral tumorigenesis and longitudinal studies on subcutaneous solid tumor formation showed dramatic decreases in tumorigenesis and solid tumor progression, respectively, after treatment with the combination. Studies to elucidate the molecular mechanisms of the inhibition of angiogenesis and tumor regression demonstrated marked decreases in proliferating cell nuclear antigen, metalloproteinase-9, vascular endothelial growth factor, basic fibroblast growth factor, and CD31 in solid tumors. Our data demonstrated that survivin knockdown and concurrent 4-HPR treatment could be a novel therapeutic strategy for controlling growth of human glioblastomas.

Inhibition of cyclooxygenase-2-dependent survivin mediates decursin-induced apoptosis in human KBM-5 myeloid leukemia cells

We demonstrate that decursin induces apoptosis via regulation of cyclooxygenase-2 (COX-2) and survivin in leukemic KBM-5 cells. By activating an apoptotic machinery, decursin is cytotoxic to KBM-5 cells. In this apoptotic process, decursin can activate caspase family members and triggers PARP cleavage. At the same time, the expression of COX-2 and survivin in the cells is downregulated. Furthermore, decursin is in synergy with COX-2 inhibitor, celecoxib or NS398 for the induction of apoptosis. Overall, these results suggest that decursin, via inhibiting COX-2 and survivin, sensitizes human leukemia cells to apoptosis and is a potential chemotherapeutic agent to treat this disease.

Survivin withdrawal by nuclear export failure as a physiological switch to commit cells to apoptosis

Apoptosis is a tightly controlled process regulated by many signaling pathways; however, the mechanisms and cellular events that decide whether a cell lives or dies remain poorly understood. Here we showed that when a cell is under apoptotic stress, the prosurvival protein Survivin redistributes from the cytoplasm to the nucleus, thus acting as a physiological switch to commit the cell to apoptosis. The nuclear relocalization of Survivin is a result of inefficient assembly of functional RanGTP-CRM1-Survivin export complex due to apoptotic RanGTP gradient collapse. Subsequently, Survivin undergoes ubiquitination, which not only physically prevents its diffusion back to the cytoplasm but also facilitates its degradation. Together, this spatial and functional regulation of Survivin abolishes its cytoprotective effect toward the apoptotic executors and thus commits a cell to apoptosis. Our data indicate that the withdrawal of Survivin is a novel and active physiological regulatory mechanism that tilts the survival balance and promotes the progression of apoptosis.

Serum levels of HMGB1, survivin, and VEGF in patients with advanced non-small cell lung cancer during chemotherapy

Recently, several reports have suggested that HMGB1 (the high-mobility group box-1) plays a key role in tumor angiogenesis through multiple mechanisms, including up-regulation of proangiogenic factors. This study was conducted to investigate the prognostic role and the effects of chemotherapy on serum (ELISA) angiogenic factors: HMGB1, survivin and VEGF (Vascular Endothelial Growth Factor) in patients with advanced stage non-small cell lung cancer (NSCLC). The study entered 40 patients (31 man) and 15 healthy volunteers (control group). Peripheral blood samples were taken before and after four cycles of chemotherapy. The mean serum HMGB1 and VEGF levels were significantly higher in patients with advanced NSCLC than in controls (p=0.024, p=0.028, respectively). The levels of survivin in NSCLC patients were comparable to controls. No correlation was found between HMGB1, survivin and VEGF concentrations and the histological type and staging of lung cancer. Similarly, no correlation was revealed between the concentrations of HMGB1, survivin and VEGF and the effect of chemotherapy. However, in patients with NSCLC, HMGB1 positevely correlated with survivin (R=0.814, p=0.007) before chemotherapy, and negatively with VEGF (R=-0.841, p=0.035) after chemotherapy. When the cut-off values of serum HMGB1, survivin and VEGF (2.38 ng/ml, 81.92 pg/ml, 443.26 pg/ml, respectively) were used, the prognoses of high and low groups were not different. Concluding, patients with NSCLC have a higher serum concentration of HMGB1 and VEGF, while survivin levels are comparable to healthy individuals. In our opinion, determination of HMGB1, survivin and VEGF concentrations has no clinical significance in the prognosis of the survival time in lung cancer.

Epigenetic methylation and expression of caspase 8 and survivin in hepatocellular carcinoma

Caspase 8 and survivin are known as key molecules of apoptosis in hepatocellular carcinoma (HCC). The purpose of the present study was to investigate the relationship between promoter methylation and expression and apoptotic function of caspase 8 and survivin in HCC. Promoter methylation of the caspase 8 and survivin gene was analyzed in 73 primary HCC using methylation-specific polymerase chain reaction. The relationship between immunohistochemical expression of gene products and proliferative/apoptotic indices, and clinicopathological parameters was also investigated. Twenty-five (34%) and 24 (33%) patients had promoter methylation of caspase 8 and survivin gene. Immunohistochemical staining of caspase 8 and survivin was observed in 35 (48%) and 32 (44%). The methylation of caspase 8 and survivin demonstrated a negative correlation with immunohistochemical expression of gene products (P= 0.049 and P= 0.001). Methylation of caspase 8 and positive expression of its gene product was significantly correlated with high apoptotic indices (P= 0.032 and P= 0.026). Nuclear survivin expression was significantly correlated with high proliferative index (P= 0.001). On survival analysis, positive nuclear survivin expression was associated with a poor prognosis in HCC (P= 0.043). In conclusion, epigenetic alteration by promoter methylation of caspase 8 and survivin may constitute an important regulatory mechanism for expression of those genes in HCC.

Anterior gradient-2 plays a critical role in breast cancer cell growth and survival by modulating cyclin D1, estrogen receptor-alpha and survivin

Introduction

Anterior-gradient 2 (AGR2) is an estrogen-responsive secreted protein. Its upregulation has been well documented in a number of cancers, particularly breast cancer, for which mixed data exist on the prognostic implications of AGR2 expression. Although emerging evidence indicates that AGR2 is associated with poor prognosis, its function and impact on cancer-relevant pathways have not been elucidated in breast cancer.

Methods

To investigate the biologic role of AGR2 in breast cancer, AGR2 was transiently knocked down, by using siRNA, in T47 D and ZR-75-1 (estrogen receptor-α (ER)-positive) and MDA-MB-231 and SK-BR-3 (ER-negative) human breast cancer cell lines. The impact of silencing AGR2 was evaluated in both anchorage-dependent and anchorage-independent growth (soft agar, spheroid) assays. Cell-cycle profiles in ER-positive cell lines were determined with BrdU incorporation, and cell death was measured with Annexin V, JC-1, and F7-26 staining. After transiently silencing AGR2 or stimulating with recombinant AGR2, modulation of key regulators of growth and survival pathways was assessed with Western blot. Combination studies of AGR2 knockdown with the antiestrogens tamoxifen and fulvestrant were carried out and assessed at the level of anchorage-dependent growth inhibition and target modulation (cyclin D1, ER).

Results

AGR2 knockdown inhibited growth in anchorage-dependent and anchorage-independent assays, with a more-pronounced effect in ER-positive cell lines. Cyclin D1 levels and BrdU incorporation were reduced with AGR2 knockdown. Conversely, cyclin D1 was induced with recombinant AGR2. AGR2 knockdown induced cell death in ZR-75-1 and T47 D cells, and also downregulated survivin and c-Myc. Evidence of AGR2-ER crosstalk was demonstrated by a reduction of ER at the protein level after transiently silencing AGR2. AGR2 knockdown in combination with fulvestrant or tamoxifen did not preclude the efficacy of the antiestrogens, but enhanced it. In addition, p-Src, implicated in tamoxifen resistance, was downregulated with AGR2 knockdown.

Conclusions

Transiently silencing AGR2 in ER-positive breast cancer cell lines inhibited cell growth and cell-cycle progression and induced cell death. Breast cancer drivers (ER and cyclin D1) as well as cancer-signaling nodes (pSrc, c-Myc, and survivin) were demonstrated to be downstream of AGR2. Collectively, the data presented support the utility of anti-AGR2 therapy in ER-positive breast cancers because of its impact on cancer-relevant pathways.

Inactivation of PI3k/Akt signaling pathway and activation of caspase-3 are involved in tanshinone I-induced apoptosis in myeloid leukemia cells in vitro

Tanshinone I (Tan I), a diterpene quinone extracted from herbal medicine Salvia miltiorrhiza Bunge, has recently been reported to have antitumor effects. As the mechanism of its proapoptotic effects on human myeloid leukemia cells has not been extensively studied, we performed an in-depth evaluation of the effects of Tan I on apoptosis in human K562 and HL-60 cells. The results revealed that Tan I could inhibit the growth of leukemia cells and cause apoptosis in a time- and dose-dependent manner. Apoptosis was observed clearly by flow cytometry and Hoechst 33258 staining, as well as DNA fragmentation analysis. After treatment by Tan I for 48 h, the percentage of disruption of mitochondrial membrane potential (Δψm) was increased in a dose-dependent manner. Western blotting analysis demonstrated the cleavage of caspase-3 zymogen protein and a dose-dependent cleavage of poly-(ADP-ribose) polymerase. Tan I-induced apoptosis was accompanied by a significant decrease in survivin and an increase in Bax. Moreover, Tan I treatment remarkably downregulated the phosphorylation of both P85/PI3K and Akt in a time-dependent manner, and the PI3K/AKT-specific inhibitor (LY294002) mimicked the apoptosis-inducing effects of Tan I. We therefore conclude that the induction of apoptosis by Tan I in these leukemia cells is mainly related to the disruption of Δψm, the upregulation of Bax expression, and the activation of caspase-3. This process is highly correlated with the inactivation of PI3K/Akt/survivin signaling pathways. The results indicate that Tan I may serve as an effective adjunctive reagent in the treatment of leukemia.

Lignans inhibit cell growth via regulation of Wnt/beta-catenin signaling

As aberrant activation of Wnt/beta-catenin signaling is one of the major mechanisms of carcinogenesis in colon cancer, identification of inhibitors of this pathway may aid in colon cancer prevention. We investigated the ability of the lignans arctiin, matairesinol and arctigenin from Saussurea salicifolia to inhibit Wnt/beta-catenin signaling in SW480 human colon cancer cells. The lignans inhibited SW480 cell growth. In addition, the transcriptional activity of a reporter construct containing the TCF binding element (TBE) was decreased after the treatment with all three lignans. Although arctiin, matairesinol and arctigenin have similar structures, arctigenin affected Wnt/beta-catenin signaling most significantly. Further, arctigenin reduced the level of beta-catenin by inducing its phosphorylation and thus its degradation. Arctigenin also decreased expression of the beta-catenin/TCF downstream genes CCND1, survivin and CTNNB1, and induced apoptosis. These results suggest that arctigenin, an aglycone with a methoxyl group, potently inhibits the growth of human colon cancer cells via the Wnt/beta-catenin signaling pathway.

Radiation-induced cell death mechanisms

The main goal when treating malignancies with radiation therapy is to deprive tumor cells of their reproductive potential. One approach to achieve this is by inducing tumor cell apoptosis. Accumulating evidences suggest that induction of apoptosis alone is insufficient to account for the therapeutic effect of radiotherapy. It has become obvious in the last few years that inhibition of the proliferative capacity of malignant cells following irradiation, especially with solid tumors, can occur via alternative cell death modalities or permanent cell cycle arrests, i.e., senescence. In this review, apoptosis and mitotic catastrophe, the two major cell deaths induced by radiation, are described and dissected in terms of activating mechanisms. Furthermore, treatment-induced senescence and its relevance for the outcome of radiotherapy of cancer will be discussed. The importance of p53 for the induction and execution of these different types of cell deaths is highlighted. The efficiency of radiotherapy and radioimmunotherapy has much to gain by understanding the cell death mechanisms that are induced in tumor cells following irradiation. Strategies to use specific inhibitors that will manipulate key molecules in these pathways in combination with radiation might potentiate therapy and enhance tumor cell kill.

Receptor activation and inhibition in cellular response to chemotherapeutic combinational mimicries: the concept of divergent targeting

The antiproliferative effect of tandem somatostatin receptor (SSTR) activation, epidermal growth factor receptor (EGFR) inhibition, and induction of DNA damage was analyzed using octreotide (OCT), a SSTR agonist, the clinical DNA methylating agent temozolomide (TMZ), Iressa, an EGFR inhibitor, and dual EGFR-DNA targeting agents termed "combi-molecules". Using SSTR-expressing glioma cells harbouring low levels of EGFR (U87MG) or transfected to overexpress EGFR (U87/EGFR) or a variant (U87/EGFRvIII), we showed that Iressa, alone or in combination with the DNA damaging agent TMZ, and combi-molecules RA2 and RA5 inhibited EGF-induced phosphorylation of EGFR in U87MG and more moderately in U87/EGFR and U87/EGFRvIII transfected cells. This translated into equivalent levels of Erk 1/2 inhibition. Activation of SSTRs with OCT did not modulate the effects of the various treatments on Erk 1/2 phosphorylation. Likewise, SSTR activation did not alter TMZ- or DNA-damaging combi-molecules, RA2 and RA5, induced p53 activation nor upregulation. However, SSTR activation significantly shifted TMZ-, RA2- and RA5-induced cell-cycle arrest to earlier phases (i.e., G2/M to late S, late S to S, S to G1). Further analysis showed that apoptosis was not induced. This was in agreement with the fact that p53 activation did not induce Bax upregulation nor did EGFR inhibition promote Bad dephosphorylation. Moreover, enhancement of survivin, an anti-apoptotic protein, expression was observed. The results in toto suggest that the combination of SSTR activation with EGFR inhibition and DNA damage affects cell-cycle progression but a disconnection between the targeted signalling pathways in these brain tumour cells precludes synergistic cell-killing by the triple growth inhibitory events.

MYC in oncogenesis and as a target for cancer therapies

MYC proteins (c-MYC, MYCN, and MYCL) regulate processes involved in many if not all aspects of cell fate. Therefore, it is not surprising that the MYC genes are deregulated in several human neoplasias as a result from genetic and epigenetic alterations. The near "omnipotency" together with the many levels of regulation makes MYC an attractive target for tumor intervention therapy. Here, we summarize some of the current understanding of MYC function and provide an overview of different cancer forms with MYC deregulation. We also describe available treatments and highlight novel approaches in the pursuit for MYC-targeting therapies. These efforts, at different stages of development, constitute a promising platform for novel, more specific treatments with fewer side effects. If successful a MYC-targeting therapy has the potential for tailored treatment of a large number of different tumors.

Effects of short-term celecoxib treatment in patients with invasive transitional cell carcinoma of the urinary bladder

High-grade invasive transitional cell carcinoma (InvTCC) kills >14,000 people yearly in the United States, and better therapy is needed. Cyclooxygenase-2 (Cox-2) is overexpressed in bladder cancer. Cox inhibitors have caused remission of InvTCC in animal studies, and cancer regression was associated with doubling of the apoptotic index in the tumor. The purpose of this study was to determine the apoptosis-inducing effects of celecoxib (a Cox-2 inhibitor) in InvTCC in humans. Patients (minimum of 10 with paired tumor samples) with InvTCC who had elected to undergo cystectomy were enrolled. The main study end point was induction of apoptosis in tumor tissues. Patients received celecoxib (400 mg twice daily p.o. for a minimum of 14 days) between the time of diagnosis [transurethral resection of bladder tumor (TURBT)] and the time of cystectomy (standard frontline treatment for InvTCC). Terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling assay and immunohistochemistry were done on TURBT and cystectomy samples. Of 13 cases treated with celecoxib, no residual invasive cancer was identified in 3 patients at the time of cystectomy (post celecoxib). Of the 10 patients with residual cancer, 7 had induction of apoptosis in their tumor. Induction of apoptosis was less frequent (3 of 13 cases; P < 0.04) in control patients not receiving a Cox inhibitor. Expression of vascular endothelial growth factor in the tumor cells decreased more frequently (P < 0.026) in the treated patients as compared with nontreated control cases. The biological effects of celecoxib treatment (increased apoptosis) justify further study of the antitumor effects of Cox-2 inhibitors in InvTCC.

Intracellular targets of RGDS peptide in melanoma cells

Background

RGD-motif acts as a specific integrins-ligand and regulates a variety of cell-functions via extracellular action affecting cell-adhesion properties. However, increasing evidence identifies additional RGDS-functions at intracellular level. Previous reports show RGDS-internalization in endothelial cells, cardiomyocytes and lymphocytes, indicating intracellular targets such as caspase-8 and caspase-9, and suggest RGDS specific activity at cytoplasmic level. Given the role RGDS-peptides play in controlling proliferation and apoptosis in several cell types, investigating intracellular targets of RGDS in melanoma cells may un-reveal novel molecular targets and key pathways, potentially useful for a more effective approach to melanoma treatment.

Results

In the present study we show for the first time that RGDS-peptide is internalized in melanoma cells in a time-dependent way and exerts strong anti-proliferative and pro-apoptotic effects independently from its extracellular anti-adhesive action. RGES control-peptide did not show biological effects, as expected; nevertheless it is internalized, although with slower kinetics. Survivin, a known cell-cycle and survival-regulator is highly expressed in melanoma cells. Co-immunoprecipitation assays in cell lysates and overlay assays with the purified proteins showed that RGDS interacts with survivin, as well as with procaspase-3, -8 and -9. RGDS-peptide binding to survivin was found to be specific, at high affinity (Kd 27.5 μM) and located at the survivin C-terminus. RGDS-survivin interaction appeared to play a key role, since RGDS lost its anti-mitogenic effect in survivin-deprived cells with a specific siRNA.

Conclusions

RGDS inhibits melanoma growth with an adhesion-independent mechanism; it is internalized in melanoma cells and specifically interacts with survivin. The present data may indicate a novel role of RGDS-containing peptides physiologically released from the extracellular matrix and may suggest a possible novel anti-proliferation strategy in melanoma.

1,25-dihydroxyvitamin D3 enhances the apoptotic activity of MDM2 antagonist nutlin-3a in acute myeloid leukemia cells expressing wild-type p53

The tumor suppressor p53 is often referred to as "the guardian of the genome" because of its central role in the cellular response to oncogenic stress and prevention of tumor development. Mutations of p53 in acute myeloid leukemia (AML) are rare but resistance to chemotherapy has been reported because of the deregulation of the p53 signaling and differentiation pathways. It is known that the interaction of the vitamin D metabolite 1,25-dihydroxyvitamin D(3) (1,25D) with its functional vitamin D receptor leads to differentiation, G(1) arrest, and increased cell survival in p53-null AML cells. However, there are no reports on the effect of 1,25D in leukemia cells expressing wild-type p53. Here, we examine vitamin D signaling in AML cells MOLM-13 and OCI-AML3 expressing wild-type p53 in the presence and absence of the MDM2 antagonist nutlin-3. We find that 1,25D alone induces monocytic differentiation in these cell lines similar to that seen in p53-null AML cells, suggesting that the presence of wild-type p53 is compatible with activation of vitamin D signaling. Combination of nutlin-3a with 1,25D accelerated programmed cell death, likely because of enhanced nutlin-induced upregulation of the proapoptotic PIG-6 protein and downregulation of antiapoptotic BCL-2, MDMX, human kinase suppressor of Ras 2, and phosphorylated extracellular signal-regulated kinase 2.

Influence of Etoposide on anti-apoptotic and multidrug resistance-associated protein genes in CD133 positive U251 glioblastoma stem-like cells

It has been hypothesized that cancer stem cell is responsible for the refractoriness of glioblastoma therapy. This study is to observe the influence of Etoposide on anti-apoptotic and multidrug resistance-associated protein genes in glioblastoma stem-like cells. U251 glioblastoma cells were cultured and CD133 positive cancer stem-like cells were isolated and identified. Cell counting kit-8 assay, cell morphology and flow cytometry were employed for assaying cell survival condition. Real-time quantitative PCR was chosen for detecting mRNA expression of livin, livinalpha, livinbeta, survivin, MRP1 and MRP3. As results, after Etoposide intervention, the U251 stem-like cells showed more resistant property, more intact morphology and lower apoptotic rate than that in U251 cells (p<0.05). It could be found that the expression of livinbeta in U251 stem-like cells was significantly higher (p<0.05). After Etoposide intervention, only livinalpha was suppressed markedly (p<0.05), while livin expression was not notably decreased with livinbeta increased on the contrary (p<0.05). MRP1 and MRP3 in U251 stem-like cells were significantly higher than that in cancer cells, and after chemotherapy, the expression of MRP1 increased notably (p<0.05). But the expression of survivin and MRP3 did not show these features. In conclusion, after Etoposide intervention glioblastoma stem-like cells showed a stronger resistance to apoptosis and death, and the anti-apoptotic gene livinbeta was more related with the high survival rate and MRP1 appeared to be more related with transporting chemotherapeutics out of glioblastoma stem-like cells.

Executioners of apoptosis in pancreatic {beta}-cells: not just for cell death

Pancreatic beta-cell mass is dynamic and is regulated by beta-cell proliferation, neogenesis, and apoptosis. Under physiological conditions, apoptosis is tightly regulated with a slow, net rise in beta-cell mass over time. Excessive beta-cell apoptosis is an important contributor to both type 1 and type 2 diabetes development. Therefore, much effort has been given recently to better understand the mechanisms of apoptosis that occur both during physiological homeostasis and during the course of both types of diabetes. Caspases are the executioners of apoptosis that ultimately result in cell suicide. In mammals, there are 14 caspases, of which many participate in the apoptotic pathways. Genetic mouse models have been important tools for elucidation of the specific apoptotic pathways that play an essential role in beta-cell apoptosis under physiological and pathological conditions. This review focuses on the diverse roles of each of the specific caspases and their regulators, unveiling both the classical apoptotic roles as well as emerging nonapoptotic roles.

Hepatocyte-specific deletion of the antiapoptotic protein myeloid cell leukemia-1 triggers proliferation and hepatocarcinogenesis in mice

Regulation of hepatocellular apoptosis is crucial for liver homeostasis. Increased sensitivity of hepatocytes toward apoptosis results in chronic liver injury, whereas apoptosis resistance is linked to hepatocarcinogenesis and nonresponsiveness to therapy-induced cell death. Recently, we have demonstrated an essential role of the antiapoptotic Bcl-2 family member Myeloid cell leukemia-1 (Mcl-1) in hepatocyte survival. In mice lacking Mcl-1 specifically in hepatocytes (Mcl-1(Deltahep)), spontaneous apoptosis caused severe liver damage. Here, we demonstrate that chronically increased apoptosis of hepatocytes coincides with strong hepatocyte proliferation resulting in hepatocellular carcinoma (HCC). Liver cell tumor formation was observed in >50% of Mcl-1(Deltahep) mice already by the age of 8 months, whereas 12-month-old wild-type (wt) and heterozygous Mcl-1(flox/wt) mice lacked tumors. Tumors revealed a heterogenous spectrum ranging from small dysplastic nodules to HCC. The neoplastic nature of the tumors was confirmed by histology, expression of the HCC marker glutamine synthetase and chromosomal aberrations. Liver carcinogenesis in Mcl-1(Deltahep) mice was paralleled by markedly increased levels of Survivin, an important regulator of mitosis which is selectively overexpressed in common human cancers.

CONCLUSION

This study provides in vivo evidence that increased apoptosis of hepatocytes not only impairs liver homeostasis but is also accompanied by hepatocyte proliferation and hepatocarcinogenesis. Our findings might have implications for understanding apoptosis-related human liver diseases.

Regulation of survivin by PI3K/Akt/p70S6K1 pathway

PI3K activation is commonly observed in many human cancer cells. Survivin expression is elevated in cancer cells, and induced by some growth factors through PI3K activation. However, it is not clear whether PI3K activation is sufficient to induce survivin expression. To investigate the role of PI3K pathway in the regulation of survivin, we expressed an active form of PI3K, v-P3k in chicken embryonic fibroblast cells (CEF), and found that overexpression of PI3K-induced survivin mRNA expression. Forced expression of wild-type but not mutant tumor suppressor PTEN in CEF decreased survivin mRNA levels. PI3K regulates survivin expression through Akt activation. To further investigate downstream target of PI3K and Akt in regulating the expression of survivin mRNA, we found that PI3K and Akt-induced p70S6K1 activation and that overexpression of p70S6K1 alone was sufficient to induce survivin expression. The treatment of CEF cells by rapamycin decreased the survivin mRNA expression. This result demonstrated that p70S6K1 is an important target downstream of PI3K and Akt in regulating suvivin mRNA expression. The knockdown of survivin mRNA expression by its specific siRNA induced apoptosis of cancer cells when the cells were treated with LY294002 or taxol. Taken together, these results demonstrated that PI3K/Akt/p70S6K1 pathway is essential for regulating survivin mRNA expression.

Survivin is a potential mediator of prostate cancer metastasis

PURPOSE

We examined whether Survivin expression is associated with an increased risk of metastasis in prostate cancer.

METHODS AND MATERIALS

A total of 205 patients with T1 (23%) and T2 (77%) prostate cancer were treated with conventional external beam radiation therapy from 1991 to 1993 at the Massachusetts General Hospital. Of the patients, 62 had adequate and suitable-stained tumor material for Survivin analysis. Median follow-up was 102 months (range, 5-127 months). Distant failure was determined on the basis of clinical criteria. In preclinical studies, replication-deficient adenovirus encoding phosphorylation-defective Survivin Thr34→Ala dominant-negative mutant pAd-S(T34A) or short hairpin RNA (shRNA) was used to inhibit Survivin in prostate cancer models, and the cell motility, morphology, and metastasis were investigated.

RESULTS

Our correlative data on men with early-stage (T1/T2) prostate cancers treated at Massachusetts General Hospital by definitive radiotherapy indicated that overexpression of Survivin (positive staining in ≥10% cells) was associated with a significantly increased risk for the subsequent development of distant metastasis (p = 0.016) in the univariate analysis. In the multivariate analysis, overexpression of Survivin remained an independent predictor of distant metastasis (p = 0.008). The inhibition of Survivin dramatically inhibited invasiveness of prostate cancer cells in the in vitro invasion assay and spontaneous metastasis in the Dunning prostate cancer in vivo model. Furthermore, attenuation of Survivin resulted in changes in the microtubule cytoskeleton, loss of cellular polarity, and loss of motility.

CONCLUSIONS

This study suggests that Survivin may be a potentially important prognostic marker and promising therapeutic target in metastatic prostate cancer.

Learning about cancer from frogs: analysis of mitotic spindles in Xenopus egg extracts

The mitotic spindle is responsible for correctly segregating chromosomes during cellular division. Disruption of this process leads to genomic instability in the form of aneuploidy, which can contribute to the development of cancer. Therefore, identification and characterization of factors that are responsible for the assembly and regulation of the spindle are crucial. Not only are these factors often altered in cancer, but they also serve as potential therapeutic targets. Xenopus egg extract is a powerful tool for studying spindle assembly and other cell cycle-related events owing, in large part, to the ease with which protein function can be manipulated in the extract. Importantly, the spindle factors that have been characterized in egg extract are conserved in human spindle assembly. In this review, we explain how the extract is prepared and manipulated to study the function of individual factors in spindle assembly and the spindle checkpoint. Furthermore, we provide examples of several spindle factors that have been defined functionally using the extract system and discuss how these factors are altered in human cancer.

Potential role of caveolin-1 in acetaminophen-induced hepatotoxicity

Caveolin-1 (Cav-1) is a membrane scaffolding protein, which functions to regulate intracellular compartmentalization of various signaling molecules. In the present studies, transgenic mice with a targeted disruption of the Cav-1 gene (Cav-1(-/-)) were used to assess the role of Cav-1 in acetaminophen-induced hepatotoxicity. Treatment of wild-type mice with acetaminophen (300 mg/kg) resulted in centrilobular hepatic necrosis and increases in serum transaminases. This was correlated with decreased expression of Cav-1 in the liver. Acetaminophen-induced hepatotoxicity was significantly attenuated in Cav-1(-/-) mice, an effect that was independent of acetaminophen metabolism. Acetaminophen administration resulted in increased hepatic expression of the oxidative stress marker, lipocalin 24p3, as well as hemeoxygenase-1, but decreased glutathione and superoxide dismutase-1; no differences were noted between the genotypes suggesting that reduced toxicity in Cav-1(-/-) mice is not due to alterations in antioxidant defense. In wild-type mice, acetaminophen increased mRNA expression of the pro-inflammatory cytokines, interleukin-1beta, and monocyte chemoattractant protein-1 (MCP-1), as well as cyclooxygenase-2, while 15-lipoxygenase (15-LOX), which generates anti-inflammatory lipoxins, decreased. Acetaminophen-induced changes in MCP-1 and 15-LOX expression were greater in Cav-1(-/-) mice. Although expression of tumor necrosis factor-alpha, a potent hepatocyte mitogen, was up-regulated in the liver of Cav-1(-/-) mice after acetaminophen, expression of proliferating cell nuclear antigen and survivin, markers of cellular proliferation, were delayed, which may reflect the reduced need for tissue repair. Taken together, these data demonstrate that Cav-1 plays a role in promoting inflammation and toxicity during the pathogenesis of acetaminophen-induced injury.

Down-regulation of GRIM-19 expression is associated with hyperactivation of STAT3-induced gene expression and tumor growth in human cervical cancers

Cervical cancer is the most common malignant disease responsible for the deaths of a large number of women in the developing world. Although certain strains of human papillomavirus (HPV) have been identified as the cause of this disease, events that lead to formation of malignant tumors are not fully clear. STAT3 is a major oncogenic transcription factor involved in the development and progression of a number of human tumors. However, the mechanisms that result in loss of control over STAT3 activity are not understood. Gene associated with Retinoid-Interferon-induced Mortality-19 (GRIM-19) is a tumor-suppressive protein identified using a genetic technique in the interferon/retinoid-induced cell death pathway. Here, we show that reduction in GRIM-19 protein levels occur in a number of primary human cervical cancers. Consequently, these tumors tend to express a high basal level of STAT3 and its downstream target genes. More importantly, using a surrogate model, we show that restoration of GRIM-19 levels reestablishes the control over STAT3-dependent gene expression and tumor growth in vivo. GRIM-19 suppressed the expression of tumor invasion- and angiogenesis-associated factors to limit tumor growth. This study identifies another major novel molecular pathway inactivated during the development of human cervical cancer.

Impaired neurogenesis, learning and memory and low seizure threshold associated with loss of neural precursor cell survivin

BACKGROUND

Survivin is a unique member of the inhibitor of apoptosis protein (IAP) family in that it exhibits antiapoptotic properties and also promotes the cell cycle and mediates mitosis as a chromosome passenger protein. Survivin is highly expressed in neural precursor cells in the brain, yet its function there has not been elucidated.

RESULTS

To examine the role of neural precursor cell survivin, we first showed that survivin is normally expressed in periventricular neurogenic regions in the embryo, becoming restricted postnatally to proliferating and migrating NPCs in the key neurogenic sites, the subventricular zone (SVZ) and the subgranular zone (SGZ). We then used a conditional gene inactivation strategy to delete the survivin gene prenatally in those neurogenic regions. Lack of embryonic NPC survivin results in viable, fertile mice (SurvivinCamcre) with reduced numbers of SVZ NPCs, absent rostral migratory stream, and olfactory bulb hypoplasia. The phenotype can be partially rescued, as intracerebroventricular gene delivery of survivin during embryonic development increases olfactory bulb neurogenesis, detected postnatally. SurvivinCamcre brains have fewer cortical inhibitory interneurons, contributing to enhanced sensitivity to seizures, and profound deficits in memory and learning.

CONCLUSIONS

The findings highlight the critical role that survivin plays during neural development, deficiencies of which dramatically impact on postnatal neural function.

Analysis of newly established EST databases reveals similarities between heart regeneration in newt and fish

BACKGROUND

The newt Notophthalmus viridescens possesses the remarkable ability to respond to cardiac damage by formation of new myocardial tissue. Surprisingly little is known about changes in gene activities that occur during the course of regeneration. To begin to decipher the molecular processes, that underlie restoration of functional cardiac tissue, we generated an EST database from regenerating newt hearts and compared the transcriptional profile of selected candidates with genes deregulated during zebrafish heart regeneration.

RESULTS

A cDNA library of 100,000 cDNA clones was generated from newt hearts 14 days after ventricular injury. Sequencing of 11520 cDNA clones resulted in 2894 assembled contigs. BLAST searches revealed 1695 sequences with potential homology to sequences from the NCBI database. BLAST searches to TrEMBL and Swiss-Prot databases assigned 1116 proteins to Gene Ontology terms. We also identified a relatively large set of 174 ORFs, which are likely to be unique for urodele amphibians. Expression analysis of newt-zebrafish homologues confirmed the deregulation of selected genes during heart regeneration. Sequences, BLAST results and GO annotations were visualized in a relational web based database followed by grouping of identified proteins into clusters of GO Terms. Comparison of data from regenerating zebrafish hearts identified biological processes, which were uniformly overrepresented during cardiac regeneration in newt and zebrafish.

CONCLUSION

We concluded that heart regeneration in newts and zebrafish led to the activation of similar sets of genes, which suggests that heart regeneration in both species might follow similar principles. The design of the newly established newt EST database allows identification of molecular pathways important for heart regeneration.

A novel mouse model of inflammatory bowel disease links mammalian target of rapamycin-dependent hyperproliferation of colonic epithelium to inflammation-associated tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

Silencing of galectin-3 changes the gene expression and augments the sensitivity of gastric cancer cells to chemotherapeutic agents

Galectin-3 is known to modulate cell proliferation and apoptosis and is highly expressed in human cancers, but its function in gastric cancer is still controversial. Here, we examined the role of galectin-3 in gastric cancer cells by silencing it with synthetic double-stranded siRNA. After silencing of galectin-3, cell numbers decreased and cell shape changed. Galectin-3 siRNA treatment also induced G(1) arrest. DNA microarray analysis was used to assess changes in gene expression following galectin-3 silencing. We found that silencing of galectin-3 caused changes in gene expression. RT-PCR and real-time PCR were utilized for validation of the changes found in microarray studies. Western blot analysis confirmed changes in the expression of proteins of interest: cyclin D1, survivin, XIAP, XAF, PUMA, and GADD45alpha. Generally, it tended to increase the expression of several pro-apoptotic genes, and to decrease the expression of cell cycle progressive genes. We also confirmed that changes in the expression of these genes were caused by galectin-3 overexpression. Finally, we demonstrated that silencing of galectin-3 enhanced apoptosis induction with chemotherapeutic agents by further reducing the expression of anti-apoptotic and/or cell survival molecules such as survivin, cyclin D1, and XIAP, and increasing the expression of pro-apoptotic XAF-1. We conclude that galectin-3 is involved in cancer progression and malignancy by modulating the expression of several relevant genes, and inhibition of galectin-3 may be an approach to improve chemotherapy of gastric cancers.

Long-term maintenance of prognostic value of survivin and its relationship with p53 in T4 breast cancer patients

A large proportion of human tumors show deregulated expression of a variety of proteins that play a crucial role in the execution of the apoptotic program. Survivin belongs to the family of inhibitor of apoptosis proteins which were originally identified in baculoviruses. Ectopic expression of survivin conveys resistance to apoptosis to a variety of stimuli, and survivin is one of the most abundantly overexpressed genes in human tumors such as breast cancer. In this study we examined the expression of survivin protein in a series of T4 breast cancers to identify any correlation with long-term patient outcomes. Moreover, we investigated the hypothesis of a possible association between p53 and survivin as a factor further complicating the outcome. Archival specimens from 53 T4 breast cancer patients were included in the study and treated for the immunohistochemical localization of survivin and p53 using the streptavidin-biotin alkaline phosphatase method. The immunoreactivity was evaluated semiquantitatively according to the percentage of cells stained. Forty percent of tumors were positive for survivin. Statistical analysis revealed that survivin expression negatively influenced the 5- and 10-year disease-free and overall patient survival. In multivariate analysis, survivin expression was a significant independent prognostic indicator of worse outcome in overall survival [hazard ratio (HR)=2.61]. Our results showed that survivin is associated with a worse prognosis in patients with T4 breast cancer, and remarkably its prognostic relevance is maintained even long-term. Notably, p53 (HR=3.2) seems to negatively enhance the effect of survivin on survival.

A novel mouse model of inflammatory bowel disease links mammalian target of rapamycin-dependent hyperproliferation of colonic epithelium to inflammation-associated tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

Vorinostat enhances the activity of temsirolimus in renal cell carcinoma through suppression of survivin levels

PURPOSE

The mammalian target of rapamycin (mTOR) inhibitor temsirolimus has exhibited promising anticancer activity for the treatment of renal cell cancers (RCC). Survivin expression has been implicated in drug resistance and reducing its levels with the histone deacetylase (HDAC) inhibitor vorinostat may enhance the anticancer activity of temsirolimus.

EXPERIMENTAL DESIGN

The sensitivity of RCC cell lines to the combination of temsirolimus and vorinostat was determined by measuring cell viability, clonogenic survival, and apoptosis. The effects of this combination on survivin levels were determined in vitro and in vivo. Survivin expression was silenced using small interfering RNA to evaluate its role in determining sensitivity to temsirolimus and vorinostat. The effect of the combination on angiogenesis was also determined in RCC xenograft models.

RESULTS

Vorinostat synergistically improved the anticancer activity of temsirolimus in a panel of RCC cell lines in vitro and in two xenograft models in vivo. While each single agent led to a modest decrease in survivin levels, the combination dramatically reduced its expression, which correlated with an induction of apoptosis. Silencing survivin levels induced apoptosis and significantly improved the efficacy of temsirolimus and vorinostat. In addition, the temsirolimus/vorinostat combination led to a strong reduction in angiogenesis.

CONCLUSIONS

Vorinostat augmented the anticancer activity of temsirolimus in both in vitro and in vivo models of RCC. The effectiveness of the combination was due to a decrease in survivin levels and corresponding induction of apoptosis, and enhanced inhibition of angiogenesis. Targeting survivin may be a promising therapeutic strategy to improve RCC therapy.

New specific molecular targets for radio-chemotherapy of rectal cancer

Patients with locally advanced rectal cancer often receive preoperative radio-chemotherapy (RCT). The mechanisms of tumour response to radiotherapy are not understood. The aim of this study was to identify the effects of RCT on gene expression in rectal tumour and normal rectal tissue. For that purpose tissue samples from 21 patients with resectable adenocarcinomas were collected for use in whole genome-microarray based gene expression analysis. A factorial experimental design allowed us to determine the effect of RCT on tumour tissue alone by removing the effect of radiation on normal tissue. This resulted in 1327 differentially expressed genes in tumour tissue with p<0.05. In addition to known markers for radio-chemotherapy, a Gene Set Enrichment Analysis (GSEA) showed a significant enrichment in gene sets associated with cell adhesion and leukocyte transendothelial migration. The profound change of cell adhesion molecule expression in rectal tumour tissue could either increase the risk of metastasis, or decrease the tumour's invasive potential.

Caspase 2-mediated tumor suppression involves survivin gene silencing

One of the pivotal functions of endogenous tumor suppression is to oppose aberrant cell survival, but the molecular requirements of this process are not completely understood. Here, we show that caspase 2, a death effector with largely unknown functions, represses transcription of the survivin gene, a general regulator of cell division and cytoprotection in tumors. This pathway involves caspase 2 proteolytic cleavage of the NFκB activator, RIP1. In turn, loss of RIP1 abolishes transcription of NFκB target genes, including survivin, resulting in deregulated mitotic transitions, enhanced apoptosis, and suppression of tumorigenicity, in vivo. Therefore, caspase 2 functions as an endogenous inhibitor of NFκB-dependent cell survival, and this mechanism may contribute to tumor suppression in humans.

Survivin: a potential prognostic marker and chemoradiotherapeutic target for colorectal cancer

OBJECTIVE

The aim of our study was to explore the expression of survivin gene in colorectal cancer (CRC) and its possibility as a molecular target for CRC chemoradiotherapy.

MATERIALS AND METHODS

Immunohistochemistry was performed to detect the expression of survivin in 68 CRC specimens. The correlations between survivin expression and clinicopathological factors and prognosis were evaluated. RNA interference was employed to downregulate survivin expression. The effects of survivin downregulation on chemoradiotherapy of CRC cells were evaluated.

RESULTS

The staining of survivin protein was strongly positive in the cytoplasm of CRC cells. Its expression was significantly correlated with tumor differentiation, Duke's stage, lymph node metastasis. Moreover, the elevated survivin expression was an independent factor for predicting the prognosis of CRC patients. Survivin downregulation could also enhance chemosensitivity or radiosensitivity of colorectal cells.

CONCLUSIONS

Survivin might be an independent prognostic factor and a potential target for the chemoradiotherapy of CRC patients.

EM011 activates a survivin-dependent apoptotic program in human non-small cell lung cancer cells

Background

Lung cancer remains a leading cause of cancer death among both men and women in the United States. Treatment modalities available for this malignancy are inadequate and thus new drugs with improved pharmacological profiles and superior therapeutic indices are being continually explored. Noscapinoids constitute an emerging class of anticancer agents that bind tubulin but do not significantly alter the monomer/polymer ratio of tubulin. EM011, a rationally-designed member of this class of non-toxic agents, is more potent than the lead molecule, noscapine.

Results

Here we report that EM011 inhibited proliferation of a comprehensive panel of lung cancer cells with IC₅₀'s ranging from 4-50 μM. In A549 human non-small cell lung cancer cells, the antiproliferative activity was mediated through blockage of cell-cycle progression by induction of a transient but robust mitotic arrest accompanied by activation of the spindle assembly checkpoint. The mitotically-arrested A549 cells then override the activated mitotic checkpoint and aberrantly exit mitosis without cytokinesis resulting in pseudo G1-like multinucleated cells that either succumb directly to apoptosis or continue another round of the cell-cycle. The accumulated enormous DNA perhaps acts as genotoxic stress to trigger cell death. EM011-induced apoptotic cell death in A549 cells was associated with a decrease of the Bcl2/BAX ratio, activation of caspase-3 and cleavage of PARP. Furthermore, EM011 induced downregulation of survivin expression over time of treatment. Abrogation of survivin led to an increase of cell death whereas, overexpression caused decreased apoptosis.

Conclusion

These in vitro data suggest that EM011 mediates antiproliferative and proapoptotic activity in non-small cell A549 lung cancer cells by impeding cell-cycle progression and attenuating antiapoptotic signaling circuitries (viz. Bcl2, survivin). The study provides evidence for the potential usefulness of EM011 in chemotherapy of lung cancer.