Survivin antisense oligonucleotides effectively radiosensitize colorectal cancer cells in both tissue culture and murine xenograft models

Clinicopathological and Prognostic Significance of Inhibitor of Apoptosis Protein (IAP) Family Members in Lung Cancer: A Meta-Analysis

Lung cancer is the most common cause of cancer-related death worldwide. Approximately 85% is non-small-cell and 15% is small-cell lung cancer. The inhibitor of apoptosis proteins (IAPs) represent a heterogeneous family of anti-apoptotic proteins, some members of which have been reported to correlate with clinical outcome in lung cancer. We screened PubMed, Web of Science, and Scopus for studies that investigated the prognostic value and clinicopathological features of IAPs in lung cancer. Forty-five eligible studies with 4428 patients assessed the expression of the IAPs survivin, XIAP, livin, and BRUCE. The pooled hazard ratio (HR) of 33 studies that analyzed overall survival (OS) revealed a positive correlation between survivin expression and poor prognosis. Seven studies displayed a strong association between survivin and disease recurrence. Two studies that assessed the expression of XIAP and livin, respectively, proved a significant relationship of these IAPs with poor OS. Meta-analyses of clinicopathological variables revealed a significant association between survivin and T stage, UICC stage, the presence of lymph node metastasis, and grade of differentiation. In conclusion, high expression of distinct IAPs significantly correlates with prognosis in lung cancer. Therefore, lung cancer patients might benefit from a targeted therapy against specific IAPs.

BIRC3 and BIRC5: multi-faceted inhibitors in cancer

BACKGROUND

The evasion from apoptosis is a common strategy adopted by most tumors, and inhibitors of apoptosis proteins (IAPs) are among the most studied molecular and therapeutic targets. BIRC3 (cellular IAP2) and BIRC5 (survivin) are two of the eight members of the human IAPs family. This family is characterized by the presence of the baculoviral IAP repeat (BIR) domains, involved in protein-protein interactions. In addition to the BIR domains, IAPs also contain other important domains like the C-terminal ubiquitin-conjugating (UBC) domain, the caspase recruitment (CARD) domain and the C-terminal Ring zinc-finger (RING) domain.

MAIN BODY

BIRC3 and BIRC5 have been characterized in some solid and hematological tumors and are therapeutic targets for the family of drugs called "Smac mimetics". Many evidences point to the pro-survival and antiapoptotic role of BIRC3 in cancer cells, however, not all the data are consistent and the resulting picture is heterogeneous. For instance, BIRC3 genetic inactivation due to deletions or point mutations is consistently associated to shorter progression free survival and poor prognosis in chronic lymphocytic leukemia patients. BIRC3 inactivation has also been associated to chemoimmunotherapy resistance. On the contrary, the progression from low grade gliomas to high grade gliomas is accompanied by BIRC3 expression increase, which bears relevant prognostic consequences. Due to the relationship between BIRC3, MAP3K14 and the non-canonical NF-kB pathway, BIRC3 inactivation bears consequences also on the tumor cells relying on NF-kB pathway to survive. BIRC5, on the contrary, is commonly considered an anti-apoptotic molecule, promoting cell division and tumor progression and it is widely regarded as potential therapeutic target.

CONCLUSIONS

The present manuscript collects and reviews the most recent literature concerning the role played by BIRC3 and BIRC5 in cancer cells, providing useful information for the choice of the best therapeutic targets.

Predicting Response to Neoadjuvant Therapy in Colorectal Cancer Patients the Role of Messenger-and Micro-RNA Profiling

Colorectal cancer patients' responses to neoadjuvant therapy undergo broad inter-individual variations. The aim of this systematic review is to identify a molecular signature that is predictive of colon cancer downstaging and/or downgrading after neoadjuvant therapy. Among the hundreds analysed in the available studies, only 19 messenger-RNAs (mRNAs) and six micro-RNAs (miRNAs) were differentially expressed in responders versus non-responders in two or more independent studies. Therefore, a mRNA/miRNA signature can be designed accordingly, with limitations caused by the retrospective nature of these studies, the heterogeneity in study designs and the downgrading/downstaging assessment criteria. This signature can be proposed to tailor neoadjuvant therapy regimens on an individual basis.

Trace of survivin in cancer

Survivin is one of the most cancer-specific proteins overexpressed in almost all malignancies, but is nearly undetectable in most normal tissues in adults. Functionally, as a member of the inhibitor of apoptosis family, survivin has been shown to inhibit apoptosis and increase proliferation. The antiapoptotic function of survivin seems to be related to its ability to inhibit caspases directly or indirectly. Furthermore, the role of survivin in cell cycle division control is related to its role in the chromosomal passenger complex. Consistent with its determining role in these processes, survivin plays a crucial role in cancer progression and cancer cell resistance to anticancer drugs and ionizing radiation. On the basis of these findings, recently survivin has been investigated intensively as an ideal tumor biomarker. Thus, multiple molecular approaches such as use of the RNA interfering technique, antisense oligonucleotides, ribozyme, and small molecule inhibitors have been used to downregulate survivin regulation and inhibit its biological function consequently. In this review, all these approaches are explained and other compounds that induced apoptosis in different cell lines through survivin inhibition are also reported.

Discovery of inner centromere protein-derived small peptides for cancer imaging and treatment targeting survivin

Survivin belongs to the inhibitor of apoptosis protein family, which is consistently overexpressed in most cancer cells but rarely expressed in normal adult tissues. Therefore, the detection and inhibition of survivin are regarded as attractive strategies for cancer‐specific treatment. In this study, we designed and synthesized 7‐19 residues of inner centromere protein (INCENP)‐derived small peptides (INC peptides) as novel survivin‐targeting agents. The INC peptides showed binding affinity for the human survivin protein (K_d = 91.4‐255 nmol L⁻¹); INC_16‐22, which contains residues 16‐22 of INCENP, showed the highest affinity (91.4 nmol L⁻¹). Confocal fluorescence imaging showed consistent colocalization of FITC‐INC_16‐22 and survivin in cell lines. Nona‐arginine‐linked INC_16‐22 (r9‐INC_16‐22) rendered INC_16‐22 cells penetrable and strongly inhibited cell growth of MIA PaCa‐2 cells (52% inhibition at 1.0 µmol L⁻¹) and MDA‐MB‐231 cells (60% inhibition at 10 µmol L⁻¹) as determined by MTT assays. The exposure of MIA PaCa‐2 cells to 40 µmol L⁻¹ r9‐INC_16‐22 apparently reduced the intracellular protein expression levels of survivin. However, cleaved caspase‐3 was significantly increased in cells treated with r9‐INC_16‐22, even at 10 µmol L⁻¹, compared to untreated cells. Flow cytometry revealed that r9‐INC_16‐22 strongly induced apoptosis in MIA PaCa‐2 cells. These results indicate that the cytotoxic effects of r9‐INC_16‐22 could be mediated mainly through the disruption of survivin‐dependent antiapoptotic functions and partly because of the direct degradation of the survivin protein. Our findings suggest that INC peptides can act as useful scaffolds for novel cancer imaging and anticancer agents.

Modulation of Respiration and Mitochondrial Dynamics by SMAC-Mimetics for Combination Therapy in Chemoresistant Cancer

Inhibitor of apoptosis proteins (IAP) are cell death regulators that bind caspases and interfere with apoptotic signalling via death receptors or intrinsic cell death pathways. BIRC4/XIAP is the most potent anti-apoptotic IAP-member and it physically interacts with caspases via its BIR2 and its BIR3 domain. These domains are also critical for the interaction with mitochondria-derived SMAC/Diablo and with the IAP protein survivin. Survivin is frequently overexpressed in neuroblastoma due to a gain of 17q and we have demonstrated that survivin confers resistance to chemotherapeutic agents and reprograms metabolism of neuroblastoma cells towards glycolysis. As regulator of mitochondrial fission and autophagy survivin acts at the crossroads of mitochondrial architecture, autophagy and cellular energy metabolism.

Methods: We tested the effect of SMAC-mimetics on the XIAP/survivin axis as modulator of cellular metabolism analysing mitochondrial morphology, metabolic intermediates and cellular survival. Finally, the impact of the combined treatment was evaluated in a xenograft neuroblastoma mouse model assessing the therapy effect on tumour size and volume.

Results: Here we demonstrated that XIAP sequesters significant amounts of survivin within the cell that can be mobilized by so called SMAC-mimetics. SMAC-mimetics are drugs that are designed to bind with high affinity to XIAP-BIR2 / BIR3 domains to release caspases and re-sensitize XIAP-overexpressing tumors for chemotherapy. However, SMAC-mimetic treatment releases also survivin from XIAP and thereby induces mitochondrial fragmentation, prevents ROS accumulation and leads to the Warburg effect, an unwanted side effect of this therapy. Importantly, cells that drift into a highly glycolytic state due to SMAC-mimetic treatment become also highly sensitive to non-genotoxic treatment with glycolysis inhibitors such as 2-Deoxy-D-glucose (2DG) in vitro and in vivo.

Conclusion: A combinational therapy of non-genotoxic SMAC-mimetics and glycolysis-inhibitors overcomes IAP-mediated cell survival in cancer and provides therefore an attractive usage of SMAC-mimetics.

Understanding Apoptosis and Apoptotic Pathways Targeted Cancer Therapeutics

Various physiological processes involve appropriate tissue developmental process and homeostasis - the pathogenesis of several diseases connected with deregulatory apoptosis process. Apoptosis plays a crucial role in maintaining a balance between cell death and division, evasion of apoptosis results in the uncontrolled multiplication of cells leading to different diseases such as cancer. Currently, the development of apoptosis targeting anticancer drugs has gained much interest since cell death induced by apoptosis causes minimal inflammation. The understanding of complexities of apoptosis mechanism and how apoptosis is evolved by tumor cells to oppose cell death has focused research into the new strategies designed to induce apoptosis in cancer cells. This review focused on the underlying mechanism of apoptosis and the dysregulation of apoptosis modulators involved in the extrinsic and intrinsic apoptotic pathway, which include death receptors (DRs) proteins, cellular FLICE inhibitory proteins (c-FLIP), anti-apoptotic Bcl-2 proteins, inhibitors of apoptosis proteins (IAPs), tumor suppressor (p53) in cancer cells along with various current clinical approaches aimed to selectively induce apoptosis in cancer cells.

Emerging Strategies of Nanomaterial-Mediated Tumor Radiosensitization

Nano-radiosensitization has been a hot concept for the past ten years, and the nanomaterial-mediated tumor radiosensitization method is mainly focused on increasing intracellular radiation deposition by high atomic number (high Z) nanomaterials, particularly gold (Au)-mediated radiation enhancement. Recently, various new nanomaterial-mediated radiosensitive approaches have been successively reported, such as catalyzing reactive oxygen species (ROS) generation, consuming intracellular reduced glutathione (GSH), overcoming tumor hypoxia, and various synergistic radiotherapy ways. These strategies may open a new avenue for enhancing the radiotherapeutic effect and avoiding its side effects. Nevertheless, reviews systematically summarizing these newly emerging methods and their radiosensitive mechanisms are still rare. Therefore, the general strategies of nanomaterial-mediated tumor radiosensitization are comprehensively summarized, particularly aiming at introducing the emerging radiosensitive methods. The strategies are divided into three general parts. First, methods on account of the intrinsic radiosensitive properties of nanoradiosensitizers for radiosensitization are highlighted. Then, newly developed synergistic strategies based on multifunctional nanomaterials for enhancing radiotherapy efficacy are emphasized. Third, nanomaterial-mediated radioprotection approaches for increasing the radiotherapeutic ratio are discussed. Importantly, the clinical translation of nanomaterial-mediated tumor radiosensitization is also covered. Finally, further challenges and outlooks in this field are discussed.

Novel CD44-downstream signaling pathways mediating breast tumor invasion

CD44, also known as homing cell adhesion molecule is a multi-structural cell molecule involved in cell-cell and cell-extracellular matrix communications. CD44 regulates a number of central signaling pathways, including PI3K/AKT, Rho GTPases and the Ras-MAPK pathways, but also acts as a growth/arrest sensor, and inhibitor of angiogenesis and invasion, in response to signals from the microenvironment. The function of CD44 has been very controversial since it acts as both, a suppressor and a promoter of tumor growth and progression. To address this discrepancy, we have previously established CD44-inducible system both in vitro and in vivo. Next, using microarray analysis, we have identified and validated Survivin, Cortactin and TGF-β2 as novel CD44-downstream target genes, and characterized their signaling pathways underpinning CD44-promoted breast cancer (BC) cell invasion. This report aims to update the literature by adding and discussing the impact of these novel three signaling pathways to better understand the CD44-signaling pathways involved in BC tumor cell invasion.

Inhibitors of apoptosis: clinical implications in cancer

Inhibitor of apoptosis (IAP) family comprises a group of endogenous proteins that function as main regulators of caspase activity and cell death. They are considered the main culprits in evasion of apoptosis, which is a fundamental hallmark of carcinogenesis. Overexpression of IAP proteins has been documented in various solid and hematological malignancies, rendering them resistant to standard chemotherapeutics and radiation therapy and conferring poor prognosis. This observation has urged their exploitation as therapeutic targets in cancer with promising pre-clinical outcomes. This review describes the structural and functional features of IAP proteins to elucidate the mechanism of their anti-apoptotic activity. We also provide an update on patterns of IAP expression in different tumors, their impact on treatment response and prognosis, as well as the emerging investigational drugs targeting them. This aims at shedding the light on the advances in IAP targeting achieved to date, and encourage further development of clinically applicable therapeutic approaches.

Prognostic significance of survivin in rectal cancer patients treated with surgery and postoperative concurrent chemo-radiation therapy

Background & Aims

This study is designed to investigate the expression of survivin and p53 in human rectal cancer tissues and analyze associations between expression and clinical outcomes in terms of disease recurrence and survival duration.

Results

During follow-up (median 119.0, range 6.6 to 161.3 months), tumor recurrence was detected in 50 patients (43.1%), and local recurrence developed as a first failure site in 13 patients (11.2%). Positive immunostaining of nuclear and cytoplasmic survivin was observed in about one quarter of patients, and about half of all patients had positive staining for p53. Both survivin and p53 were significant prognostic factors of disease-free survival in the univariate analyses, but only survivin remained a significant prognostic factor in the multivariate analysis.

Methods

We performed a retrospective study with 116 locally advanced rectal cancer patients who underwent total mesorectal excision (TME) followed by postoperative concurrent chemo-radiation therapy (CCRT). Immunohistochemical staining was conducted using antibodies for survivin or p53, and their expression was analyzed using an individual score that combined the percentage of positive cells and staining intensity.

Conclusions

Overexpression of nuclear and cytoplasmic survivin in locally advanced rectal cancer patients was associated with a higher recurrence rate in rectal cancer patients treated with TME followed by postoperative CCRT.

Survivin-Based Treatment Strategies for Squamous Cell Carcinoma

Survivin, an anti-apoptotic molecule abundantly expressed in most human neoplasms, has been reported to contribute to cancer initiation and drug resistance in a wide variety of human tumors. Efficient downregulation of survivin can sensitize tumor cells to various therapeutic interventions, generating considerable efforts in its validation as a new target in cancer therapy. This review thoroughly analyzes up-to-date information on the potential of survivin as a therapeutic target for new anticancer treatments. The literature dealing with the therapeutic targeting of survivin will be reviewed, discussing specifically squamous cell carcinomas (SCCs), and with emphasis on the last clinical trials. This review gives insight into the recent developments undertaken in validating various treatment strategies that target survivin in SCCs and analyze the translational possibility, identifying those strategies that seem to be the closest to being incorporated into clinical practice. The most recent developments, such as dominant-negative survivin mutants, RNA interference, anti-sense oligonucleotides, small-molecule inhibitors, and peptide-based immunotherapy, seem to be helpful for effectively downregulating survivin expression and reducing tumor growth potential, increasing the apoptotic rate, and sensitizing tumor cells to chemo- and radiotherapy. However, selective and efficient targeting of survivin in clinical trials still poses a major challenge.

Niclosamide sensitizes triple-negative breast cancer cells to ionizing radiation in association with the inhibition of Wnt/β-catenin signaling

Triple-negative breast cancer (TNBC) is one of the most difficult breast cancers to treat because there is no targeted treatment, and conventional cytotoxic chemotherapy followed by adjuvant radiation therapy is the standard of care for patients with TNBC. We herein reported that ionizing radiation (IR) induced Wnt3a, LRP6 and β-catenin expression and consequently activated Wnt/β-catenin signaling in TNBC MDA-MB-231, MDA-MB-468 and Hs578T cells. Moreover, depletion of β-catenin by shRNA sensitized TNBC cells to IR, whereas treatment of Wnt3a protein or overexpression of β-catenin resulted in radioresistance of TNBC cells. Niclosamide, a potent inhibitor of Wnt/β-catenin signaling, not only inhibited constitutive Wnt/β-catenin signaling, but also blocked IR-induced Wnt/β-catenin signaling in TNBC cells. In addition, niclosamide sensitized TNBC cells to IR, prevented Wnt3a-induced radioresistance, and overcame β-catenin-induced radioresistance in TNBC cells. Importantly, animals treated with the combination of niclosamide and γ-ray local tumor irradiation had significant inhibition of MDA-MB-231 tumor growth compared with treated with local tumor irradiation alone. These findings indicate that Wnt/β-catenin signaling pathway plays an important role in the development of radioresistance of TNBC cells, and that niclosamide had significant radiosensitizing effects by inhibiting Wnt/β-catenin signaling in TNBC cells. Our study also provides rationale for further preclinical and clinical evaluation of niclosamide in TNBC management.

Targeting survivin for therapeutic discovery: past, present, and future promises

Survivin, the smallest member of the inhibitor of apoptosis protein (IAP) family, is overexpressed in cells of almost all cancers but not in most normal tissues in adults. Survivin expression is required for cancer cell survival and knocking down its expression or inhibiting its function using molecular approaches results in spontaneous apoptosis. Thus, survivin is an attractive and perhaps ideal target for cancer drug discovery. However, a US Food and Drug Administration (FDA)-approved drug targeting survivin has yet to emerge. In this Foundation Review, we examine and evaluate various strategies that have been used to target survivin and the stages of each survivin inhibitor to help understand this lack of success. We also provide future perspectives moving forward in targeting survivin for drug discovery.

Expression and clinical significance of cyclooxygenase 2 and survivin in human gliomas

The present study aimed to determine cyclooxygenase 2 (COX-2) and survivin expression levels in glioma tissues, and to investigate their association with clinicopathological factors and patient survival. Immunohistochemistry was performed to evaluate COX-2 and survivin expression levels in paraffin-embedded surgically resected tissues from 70 patients with glioma and 7 individuals with normal brain tissues. The association between COX-2 and survivin expression levels and clinicopathological features was investigated using the χ² test, and the survival time was analyzed using the Kaplan Meier method with log-rank test. COX-2 and survivin were overexpressed in glioma tissues, and higher expression levels were observed in glioma tissues of histological grades III–IV compared with those in grade I–II tumor tissues (P<0.05); however, the expression levels were not associated with gender, age, tumor size or location (P>0.05). There was a significant positive association between the expression levels of COX-2 and survivin in the glioma tissues. Additionally, COX-2 and survivin expression levels were significantly negatively correlated with the rate of survival. In conclusion, COX-2 and survivin expression is positively associated with the pathological grade of a glioma and may contribute to glioma tumorigenesis. Therefore, COX-2 and survivin may be sensitive predictors of a negative clinical prognosis for patients with glioma.

XPO1 Inhibition Enhances Radiation Response in Preclinical Models of Rectal Cancer

PURPOSE

Combination of radiation with radiosensitizing chemotherapeutic agents improves outcomes for locally advanced rectal cancer. Current treatment includes 5-fluorouracil-based chemoradiation prior to surgical resection; however pathologic complete response varies from 15% to 20%, prompting the need to identify new radiosensitizers. Exportin 1 (XPO1, also known as chromosome region 1, CRM1) mediates the nuclear export of critical proteins required for rectal cancer proliferation and treatment resistance. We hypothesize that inhibition of XPO1 may radiosensitize cancer cells by altering the function of these critical proteins resulting in decreased radiation resistance and enhanced antitumoral effects.

EXPERIMENTAL DESIGN

To test our hypothesis, we used the selective XPO1 inhibitor, selinexor, to inhibit nuclear export in combination with radiation fractions similar to that given in clinical practice for rectal cancer: hypofractionated short-course radiation dosage of 5 Gy per fraction or the conventional long-course radiation dosage of 1 Gy fractions. Single and combination treatments were tested in colorectal cancer cell lines and xenograft tumor models.

RESULTS

Combination treatment of radiotherapy and selinexor resulted in an increase of apoptosis and decrease of proliferation compared with single treatment, which correlated with reduced tumor size. We found that the combination promoted nuclear survivin accumulation and subsequent depletion, resulting in increased apoptosis and enhanced radiation antitumoral effects.

CONCLUSIONS

Our findings suggest a novel therapeutic option for improving radiation sensitivity in the setting of rectal cancer and provide the scientific rationale to evaluate this combination strategy for clinical trials.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

Curcumin Induces Pancreatic Adenocarcinoma Cell Death Via Reduction of the Inhibitors of Apoptosis

OBJECTIVES

The inhibitor of apoptosis (IAP) proteins are critical modulators of chemotherapeutic resistance in various cancers. To address the alarming emergence of chemotherapeutic resistance in pancreatic cancer, we investigated the efficacy of the turmeric derivative curcumin in reducing IAP protein and mRNA expression resulting in pancreatic cancer cell death.

METHODS

The pancreatic adenocarcinoma cell line PANC-1 was used to assess curcumin's effects in pancreatic cancer. Curcumin uptake was measured by spectral analysis and fluorescence microscopy. AlamarBlue and Trypan blue exclusion assays were used to determine PANC-1 cell viability after curcumin treatment. Visualization of PANC-1 cell death was performed using Hoffman Modulation Contrast microscopy. Western blot, and polymerase chain reaction analyses were used to evaluate curcumin's effects on IAP protein and mRNA expression.

RESULTS

Curcumin enters PANC-1 cells and is ubiquitously present within the cell after treatment. Furthermore, curcumin reduces cell viability and induces morphological changes characteristic of cell death. Additionally, curcumin decreases IAP protein and mRNA expression in PANC-1 cells.

CONCLUSIONS

These data demonstrate that PANC-1 cells are sensitive to curcumin treatment. Futthermore, curcumin is a potential therapeutic tool for overcoming chemotherapeutic resistance mediated by IAPs. Together, this data supports a role for curcumin as part of the therapeutic approach for the treatment of pancreatic cancer.

Differential effect of phosphorylation-defective survivin on radiation response in estrogen receptor-positive and -negative breast cancer

Survivin is a key member of the inhibitor of apoptosis protein family, and is considered a promising therapeutic target due to its universal overexpression in cancers. Survivin is implicated in cellular radiation response through its role in apoptosis, cell division, and DNA damage response. In the present study, analysis of publically available data sets showed that survivin gene expression increased with breast cancer stage (p < 0.00001) and was significantly higher in estrogen receptor-negative cancers as compared to estrogen receptor-positive cancers (p = 9e-46). However, survivin was prognostic in estrogen receptor-positive tumors (p = 0.03) but not in estrogen receptor-negative tumors (p = 0.28). We assessed the effect of a survivin dominant-negative mutant on colony-formation (2D) and mammosphere-formation (3D) efficiency, and radiation response in the estrogen receptor-positive MCF7 and estrogen receptor-negative SUM149 breast cancer cell lines. The colony-formation efficiency was significantly lower in the dominant-negative survivin-transduced cells versus control MCF7 cells (0.42 vs. 0.58, p < 0.01), but it was significantly higher in dominant-negative population versus control-transduced SUM149 cells (0.29 vs. 0.20, p < 0.01). A similar, non-significant, trend in mammosphere-formation efficiency was observed. We compared the radiosensitivity of cells stably expressing dominant-negative survivin with their controls in both cell lines under 2D and 3D culture conditions following exposure to increasing doses of radiation. We found that the dominant-negative populations were radioprotective in MCF7 cells but radiosensitive in SUM149 cells compared to the control-transduced population; further, Taxol was synergistic with the survivin mutant in SUM149 but not MCF7. Our data suggests that survivin modulation influences radiation response differently in estrogen receptor-positive and estrogen receptor-negative breast cancer subtypes, warranting further investigation.

Survivin as a therapeutic target in Sonic hedgehog-driven medulloblastoma

Medulloblastoma (MB) is a highly malignant brain tumor that occurs primarily in children. Although surgery, radiation and high-dose chemotherapy have led to increased survival, many MB patients still die from their disease, and patients who survive suffer severe long-term side effects as a consequence of treatment. Thus, more effective and less toxic therapies for MB are critically important. Development of such therapies depends in part on identification of genes that are necessary for growth and survival of tumor cells. Survivin is an inhibitor of apoptosis protein that regulates cell cycle progression and resistance to apoptosis, is frequently expressed in human MB and when expressed at high levels predicts poor clinical outcome. Therefore, we hypothesized that Survivin may have a critical role in growth and survival of MB cells and that targeting it may enhance MB therapy. Here we show that Survivin is overexpressed in tumors from patched (Ptch) mutant mice, a model of Sonic hedgehog (SHH)-driven MB. Genetic deletion of survivin in Ptch mutant tumor cells significantly inhibits proliferation and causes cell cycle arrest. Treatment with small-molecule antagonists of Survivin impairs proliferation and survival of both murine and human MB cells. Finally, Survivin antagonists impede growth of MB cells in vivo. These studies highlight the importance of Survivin in SHH-driven MB, and suggest that it may represent a novel therapeutic target in patients with this disease.

Inhibition of lymphatic metastases by a survivin dominant-negative mutant

Metastasis is the most lethal attribute of human malignancy. High-level expression of survivin is involved in both carcinogenesis and angiogenesis in cancer. Previous studies indicate that a mutation of the threonine residue at position 34 (Thr34Ala) of survivin generates a dominant-negative mutant that induces apoptosis, inhibits angiogenesis, and suppresses highly metastatic breast carcinoma in mouse models. We investigated the efficacy of gene therapy with a survivin dominant-negative mutant and possible factors related to lymph node metastasis. The metastasis rate was compared between each group in order to find a survivin-targeted therapy against lymphangiogenesis in its earliest stages. We established lymph node metastasis models and treated animals with H22 tumors with Lip-mSurvivinT34A (Lip-mS), Lip-plasmid (Lip-P), or normal saline (NS). Eight days after the last dose, five randomly chosen mice from each group were sacrificed. We detected the apoptotic index, microvessel density (MVD), lymphatic microvessel density (LMVD), and the expression of VEGF-D with immunohistochemistry. After the remaining animals were sacrificed, we compared the tumor-infiltrated lymph nodes in each group. Administration of mSurvivinT34A plasmid complexed with cationic liposome (DOTAP/chol) resulted in the efficacious inhibition of tumor growth and lymph node metastasis within the mouse H22 tumor model. These responses were associated with tumor cell apoptosis, and angiogenesis and lymphangiogenesis inhibition. Our results suggested that Lip-mSurvivinT34A induced apoptosis and inhibited tumor angiogenesis and lymphangiogenesis, thus suppressing tumor growth and lymphatic metastasis. The mSurvivinT34A survivin mutant is a promising strategy of gene therapy to inhibit lymphatic metastasis.

Antichemosensitizing effect of resveratrol in cotreatment with oxaliplatin in HCT116 colon cancer cell

Purpose

Although oxaliplatin is one of the most widely used chemotherapeutic agents for the treatment of advanced stages of colorectal cancers in clinic, cancer cells often develop oxaliplatin drug resistance. Thus, overcoming oxaliplatin drug resistance is a major issue in the successful treatment for advanced stages of colorectal malignancy. In order to maximize oxaliplatin therapy, we examined whether resveratrol, a natural phytochemical known to have chemopreventive effects on cancers, can have a chemosensitizing effect upon cotreatment with oxaliplatin. Survivin, a small inhibitor of apoptosis protein (IAP), expression is examined using HCT116 colon cancer cells.

Methods

In order to examine resveratrol chemosensitizing effect upon oxaliplatin cotreatment, survivin transcripts and protein expression, cell proliferation, and apoptotic responses were evaluated using HCT116 cells. Reverse transcription polymerase chain reaction (RT-PCR), Western blot, crystal violet staining analyses were performed. For survivin specific inhibition, YM155 molecule was used.

Results

Although oxaliplatin significantly suppressed survivin transcripts and protein expression level in HCT116 cells, resveratrol cotreatment induced restoration of survivin expression level of both transcripts and protein. Apoptotic induction by oxaliplatin only treatment was nullified upon resveratrol cotreatment. Induction of survivin restoration upon resveratrol cotreatment also occurred when survivin specific inhibitor, YM155, was used. In addition to survivin restoration, resveratrol cotreatment also induced restoration of Bcl-2/caspase-3 expression suppressed by oxaliplatin only treatment.

Conclusion

Resveratrol has an antichemosensitizing effect upon cotreatment with oxaliplatin in HCT colon cancer cells. This antichemosensitizing effect of resveratrol can be cell-type specific. However, clinical use of resveratrol cotreatment with oxaliplatin should be approached cautiously.

Identification of a microRNA expression signature for chemoradiosensitivity of colorectal cancer cells, involving miRNAs-320a, -224, -132 and let7g

BACKGROUND AND PURPOSE

Preoperative chemoradiotherapy (CRT) represents the standard treatment for locally advanced rectal cancer. Tumor response and progression vary considerably. MicroRNAs represent master regulators of gene expression, and may therefore contribute to this diversity.

MATERIAL AND METHODS

Genome-wide microRNA (miRNA) profiling was performed for 12 colorectal cancer (CRC) cell lines and an individual in vitro signature of chemoradiosensitivity was established. Functional relevance of selected miRNAs was established by transfecting miRNA-mimics into SW480 and SW837 cells. The prognostic value of selected miRNAs was assessed in 128 pretherapeutic patient biopsies.

RESULTS

Thirty-six miRNAs were identified to significantly correlate with sensitivity to CRT (Q < 0.05) including miR-320a and other miRNAs involved in the MAPK-, TGF- and Wnt-pathway. Transfection of selected miRNAs (let-7g, miR-132, miR-224, miR-320a) each induced a shift of sensitivity. High expression of let-7 g was associated with a good prognosis in rectal cancer patients (P = 0.03).

CONCLUSIONS

This is the first report of a miRNA expression signature for in vitro chemoradiosensitivity of CRC cell lines. Many of the identified miRNAs have not been linked to the response to CRT and may represent potential molecular targets to sensitize resistant cancers. If further validated, let7g expression may serve as predictive biomarker.

Druggable protein interaction sites are more predisposed to surface pocket formation than the rest of the protein surface

Despite intense interest and considerable effort via high-throughput screening, there are few examples of small molecules that directly inhibit protein-protein interactions. This suggests that many protein interaction surfaces may not be intrinsically “druggable” by small molecules, and elevates in importance the few successful examples as model systems for improving our fundamental understanding of druggability. Here we describe an approach for exploring protein fluctuations enriched in conformations containing surface pockets suitable for small molecule binding. Starting from a set of seven unbound protein structures, we find that the presence of low-energy pocket-containing conformations is indeed a signature of druggable protein interaction sites and that analogous surface pockets are not formed elsewhere on the protein. We further find that ensembles of conformations generated with this biased approach structurally resemble known inhibitor-bound structures more closely than equivalent ensembles of unbiased conformations. Collectively these results suggest that “druggability” is a property encoded on a protein surface through its propensity to form pockets, and inspire a model in which the crude features of the predisposed pocket(s) restrict the range of complementary ligands; additional smaller conformational changes then respond to details of a particular ligand. We anticipate that the insights described here will prove useful in selecting protein targets for therapeutic intervention.

Identifying small-molecule inhibitors of protein interactions has traditionally presented a challenge for modern screening methods, despite interest stemming from the fact that such interactions comprise the underlying mechanisms for cell proliferation, differentiation, and survival. This suggests that many protein interaction surfaces may not be intrinsically “druggable” by small molecules, and elevates in importance the few successful examples as model systems for improving our understanding of factors contributing to druggability. Here we describe a new approach for exploring protein fluctuations leading to surface pockets suitable for small molecule binding. We find that the presence of such pockets is indeed a signature of druggable protein interaction sites, suggesting that “druggability” is a property encoded on a protein surface through its propensity to form pockets. We anticipate that the insights described here will prove useful in selecting protein targets for therapeutic intervention.

Radiotherapy response in microsatellite instability related rectal cancer

Preoperative radiotherapy may improve the resectability and subsequent local control of rectal cancers. However, the extent of radiation induced regression in these tumours varies widely between individuals. To date no reliable predictive marker of radiation sensitivity in rectal cancer has been identified. At the cellular level, radiation injury initiates a complex molecular network of DNA damage response (DDR) pathways that leads to cell cycle arrest, attempts at re-constituting the damaged DNA and should this fail, then apoptosis. This review presents the details which suggest the roles of DNA mismatch repair proteins, the lack of which define a distinct subset of colorectal cancers with microsatellite instability (MSI), in the DDR pathways. Hence routine assessment of the MSI status in rectal cancers may potentially serve as a predictor of radiotherapy response, thereby improving patient stratification in the administration of this otherwise toxic treatment.

[Molecular signaling pathways. Mechanisms and clinical use]

This brief summary on the role of experimental radiation oncology highlights several new research topics and research approaches that offer great potential for the optimization of modern radiation oncology. In addition, many areas of research, such as hypoxia, angiogenesis, the immune system, and metabolism, to name a few, comprise a substantial part of our current knowledge of tumor and radiation biology. Which new insights and therapeutic possibilities via the Human Cancer Genome Project or new processes, such as next generation sequencing may offer, cannot be easily foreseen at present. However, we do know for certain: radiation biology has and will continue to contribute to improvements in radiation oncology.

Survivin, a target to modulate the radiosensitivity of Ewing's sarcoma

BACKGROUND AND PURPOSE

Radiotherapy constitutes an essential element in the multimodal therapy of Ewing's sarcoma. Compared to other sarcomas, Ewing tumors normally show a good response to radiotherapy. However, there are consistently tumors with a radioresistant phenotype, and the underlying mechanisms are not known in detail. Here we investigated the association between survivin protein expression and the radiosensitivity of Ewing's sarcoma in vitro.

MATERIAL AND METHODS

An siRNA-based knockdown approach was used to investigate the influence of survivin expression on cell proliferation, double-strand break (DSB) induction and repair, apoptosis and colony-forming ability in four Ewing's sarcoma cell lines with and without irradiation.

RESULTS

Survivin protein and mRNA were upregulated in all cell lines tested in a dose-dependent manner. As a result of survivin knockdown, STA-ET-1 cells showed reduced cell proliferation, an increased number of radiation-induced DSBs, and reduced repair. Apoptosis was increased by knockdown alone and increased further in combination with irradiation. Colony formation was significantly reduced by survivin knockdown in combination with irradiation.

CONCLUSION

Survivin is a radiation-inducible protein in Ewing's sarcoma and its down-regulation sensitizes cells toward irradiation. Survivin knockdown in combination with radiation inhibits cell proliferation, repair, and colony formation significantly and increases apoptosis more than each single treatment alone. This might open new perspectives in the radiation treatment of Ewing's sarcoma.

A novel small molecule FL118 that selectively inhibits survivin, Mcl-1, XIAP and cIAP2 in a p53-independent manner, shows superior antitumor activity

Drug/radiation resistance to treatment and tumor relapse are major obstacles in identifying a cure for cancer. Development of novel agents that address these challenges would therefore be of the upmost importance in the fight against cancer. In this regard, studies show that the antiapoptotic protein survivin is a central molecule involved in both hurdles. Using cancer cell-based survivin-reporter systems (US 7,569,221 B2) via high throughput screening (HTS) of compound libraries, followed by in vitro and in vivo analyses of HTS-derived hit-lead compounds, we identified a novel anticancer compound (designated FL118). FL118 shows structural similarity to irinotecan. However, while the inhibition of DNA topoisomerase 1 activity by FL118 was no better than the active form of irinotecan, SN-38 at 1 µM, FL118 effectively inhibited cancer cell growth at less than nM levels in a p53 status-independent manner. Moreover, FL118 selectively inhibited survivin promoter activity and gene expression also in a p53 status-independent manner. Although the survivin promoter-reporter system was used for the identification of FL118, our studies revealed that FL118 not only inhibits survivin expression but also selectively and independently inhibits three additional cancer-associated survival genes (Mcl-1, XIAP and cIAP2) in a p53 status-independent manner, while showing no inhibitory effects on control genes. Genetic silencing or overexpression of FL118 targets demonstrated a role for these targets in FL118's effects. Follow-up in vivo studies revealed that FL118 exhibits superior antitumor efficacy in human tumor xenograft models in comparison with irinotecan, topotecan, doxorubicin, 5-FU, gemcitabine, docetaxel, oxaliplatin, cytoxan and cisplatin, and a majority of mice treated with FL118 showed tumor regression with a weekly × 4 schedule. FL118 induced favorable body-weight-loss profiles (temporary and reversible) and was able to eliminate large tumors. Together, the molecular targeting features of FL118 plus its superior antitumor activity warrant its further development toward clinical trials.

Survivin expression can predict the effect of chemoradiotherapy for advanced lower rectal cancer

BACKGROUND

Chemoradiotherapy (CRT) has been used to improve local control and survival in patients with advanced rectal carcinoma. However, a significant proportion of patients show poor response to adjuvant CRT. We thus investigated the usefulness of survivin expression as a predictive marker of the CRT response and its characteristics.

METHODS

Forty-three patients with lower rectal cancer who underwent CRT were investigated. All patients received preoperative CRT consisting of TS-1 concurrent with 40 Gy of pelvic irradiation followed by curative resection. The relationship between clinical response, or pathological response, and the expression of survivin of pre-CRT biopsy specimens was evaluated by immunohistochemistry and compared with post-CRT expression.

RESULTS

Positive expression of survivin was observed in 26 of 43 patients (60%) in pre-CRT specimens. Survivin was positively expressed in 77% of stable disease cases, and 43% of partial response (p < 0.05). Regarding the correlation between pathological response and survivin expression, positive expression of survivin was recognized in 75% (18 of 24) of Grade 0 + 1 cases, 50% (7 of 14) of Grade 2 cases, and 20% (1 of 5) of Grade 3 cases. A reverse correlation was recognized between pathological responses and survivin expression (p < 0.05). There were differences in the tumor differentiation between the survivin-positive group and the negative group (p < 0.05). The expression concordance rate was 66% between pre- and post-CRT tissues. In post-CRT tissues, nuclear survivin expression disappeared completely and cytoplasmic expression increased, especially in responder cases.

CONCLUSION

Survivin expression in biopsy could be an important predictive factor of preoperative CRT response.

XIAP as a radioresistance factor and prognostic marker for radiotherapy in human rectal adenocarcinoma

A differential responsiveness of patients to ionizing radiation is observed after preoperative radiotherapy for rectal adenocarcinoma that might be related, in part, to an apoptosis defect. To establish if proteins of the apoptotic cascades [pro-apoptotic: active caspase 3, 8, and 9 and DIABLO (direct inhibitor of apoptosis-binding protein with low pI); anti-apoptotic: XIAP (X-linked inhibitor of apoptosis)] are involved, we analyzed their profile in radioresistant (SW480) and radiosensitive (SW48) human colorectal cell lines. We demonstrated that, after irradiation, the SW48 cells increased the expression of the pro-apoptotic proteins, whereas the SW480 cells increased the expression of the anti-apoptotic protein XIAP. Moreover, XIAP knockdown in SW480 cells enhanced the basal and radiation-induced apoptotic index; the propensity of the SW480 cells to undergo apoptosis after radiation was higher compared with SW48 cells. In a translational study of 38 patients with rectal carcinoma, we analyzed the apoptotic profile for tumor and noncancerous tissue for each biopsy specimen using IHC. According to their response to preoperative radiotherapy, patients were classified into two groups: responsive and nonresponsive. Although no difference in expression of caspase 3, 8, or 9 was observed in the tumor/normal tissue ratio between responsive and nonresponsive patients, the ratio decreased for DIABLO and increased for XIAP. In conclusion, inhibition of XIAP rescues cellular radiosensitivity and both DIABLO and XIAP might be potential predictive markers of radiation responsiveness in rectal adenocarcinoma.

Radiosensitizing effect of the novel Hsp90 inhibitor NVP-AUY922 in human tumour cell lines silenced for Hsp90α

BACKGROUND

Hsp90 inhibitors can enhance the tumour sensitivity to ionising radiation (IR). However, Hsp90 inhibition leads to the up-regulation of anti-apoptotic Hsp90 and Hsp70, which might diminish the radiosensitizing effects of the inhibitors. Therefore, inhibition of the up-regulation of Hsp90 by siRNA might be a promising strategy to enhance drug-mediated radiosensitization.

MATERIALS AND METHODS

The expression of Hsp90α was silenced in A549 and GaMG tumour cell lines by siRNA treatment. Pre-silenced for Hsp90α cells were treated with NVP-AUY922, a novel Hsp90 inhibitor, for 24 h and then irradiated. Radiation response was determined by colony-forming ability. The expression of several marker proteins was analysed by Western blot. DNA damage and repair were assessed by histone γH2AX measurements.

RESULTS

We found that transfection with siRNA against Hsp90α reduced Hsp90α at mRNA and protein levels. Pre-silencing of Hsp90α reduced NVP-AUY922-mediated up-regulation of Hsp90α but it did not increase drug-mediated radiosensitization in both tumour cell lines. As revealed by Western blot, pre-silencing of Hsp90α followed by NVP-AUY922 did not change the expression of Hsp90 client proteins (Akt, Raf-1, Cdk1 and Cdk4) compared with drug treatment alone, suggesting unchanged chaperone function in transfected cells.

CONCLUSION

Pre-silencing of Hsp90α followed by Hsp90 inhibition did not enhance the radiosensitizing effect of NVP-AUY922 in both tested tumour cell lines. Future work will be done on stable transfection with shRNA against Hsp90α or simultaneous silencing of both Hsp90 isoforms, Hsp90α and Hsp90β, in order to optimize tumour cell killing.

Inhibitor of apoptosis proteins: fascinating biology leads to attractive tumor therapeutic targets

Cell death inhibition is a very successful strategy that cancer cells employ to combat the immune system and various anticancer therapies. Inhibitor of apoptosis (IAP) proteins possess a wide range of biological activities that promote cancer survival and proliferation. One of them, X-chromosome-linked IAP is a direct inhibitor of proapoptotic executioners, caspases. Cellular IAP proteins regulate expression of antiapoptotic molecules and prevent assembly of proapoptotic protein signaling complexes, while survivin regulates cell division. In addition, amplifications, mutations and chromosomal translocations of IAP genes are associated with various malignancies. Several therapeutic strategies have been designed to target IAP proteins, including a small-molecule approach that is based on mimicking the IAP-binding motif of an endogenous IAP antagonist - the second mitochondrial activator of caspases. Other strategies involve antisense nucleotides and transcriptional repression. The main focus of this article is to provide an update on IAP protein biology and perspectives on the development of IAP-targeting therapeutics.

Induction of apoptosis by survivin silencing through siRNA delivery in a human breast cancer cell line

Post-transcriptional silencing of antiapoptotic genes is a promising strategy for cancer therapy, but delivering short interfering RNA (siRNA) molecules against such targets is challenging due to inability of anionic siRNA to cross cellular membranes. Lipid substitution on small molecular weight, nontoxic polyethylenimine (PEI) has been investigated as a promising approach for effective siRNA delivery. In this study, we report on the ability of low molecular weight, lipid-substituted PEI to deliver siRNA against the antiapoptotic protein survivin. Toxicity of a library of lipid-substituted PEIs, as well as their siRNA delivery and survivin silencing efficiency, was evaluated in MDA-MB-231 human breast cancer cells. A significant increase in cellular delivery of siRNA was observed as a result of lipid substitution. Most significant downregulation of survivin was established by caprylic acid-substituted polymers, which resulted in significant levels of apoptosis induction and resultant loss of cell viability. Survivin downregulation prior to anticancer drug treatment decreased the IC(50) of several drugs by 50- to 120-fold. Our experiments indicated an effective downregulation of survivin, a cell protective protein upregulated in tumor cells, by delivering siRNA with hydrophobically modified PEI. This study introduces a promising delivery system for safe and effective siRNA delivery that will be suitable for further investigation in preclinical animal models.

High survivin expression as a predictor of poor response to preoperative chemoradiotherapy in locally advanced rectal cancer

PURPOSE

To evaluate seven molecular markers including cyclooxygenase -2, epidermal growth factor receptor, Ki-67, p21, survivin, thymidylate synthase, and vascular endothelial growth factor for prediction of response to preoperative chemoradiotherapy in locally advanced rectal cancer.

MATERIALS AND METHODS

Fifty-four patients with clinical T3-4 and/or node-positive rectal cancer who underwent preoperative chemoradiotherapy followed by surgical resection were enrolled into this study. Preoperative chemoradiotherapy consisted of 50.4 Gy of pelvic irradiation with concomitant 5-fluorouracil or oral capecitabine. Expression of molecular markers in pretreatment paraffin-embedded tumor biopsy specimens was assessed by immunohistochemical staining on the tissue microarray. Tumor downstaging was used as an endpoint for evaluation of tumor response.

RESULTS

Tumor downstaging was observed in 22 patients (41%), and pathologic complete remission in 7 patients (13%). Among seven molecular markers, only survivin expression was significantly related with tumor downstaging: 26% with high survivin expression (>75% in extent) vs. 72% with low survivin expression (p = 0.0011). However, other six molecular markers were found not to have any correlation with tumor downstaging.

CONCLUSIONS

High survivin expression in pretreatment tumor biopsy was associated with less tumor downstaging after preoperative chemoradiotherapy for locally advanced rectal cancer.

Enhancement of 5-fluorouracil-induced in vitro and in vivo radiosensitization with MEK inhibition

PURPOSE

Gastrointestinal cancers frequently exhibit mutational activation of the Ras/MAPK pathway, which is implicated in resistance to ionizing radiation (IR) and chemotherapy. Concurrent radiotherapy and 5-fluorouracil (5-FU) based chemotherapy is commonly used for treatment of gastrointestinal malignancies. We previously reported radiosensitization with selumetinib, an inhibitor of MEK1/2. The purpose of the current study was to evaluate if selumetinib could enhance radiosensitivity induced by 5-FU.

EXPERIMENTAL DESIGN

Clonogenic survival assays were carried out with the HT29 (colorectal), HCT116 (colorectal), and MiaPaca-2 (pancreatic) cell lines using pre-IR treatment with selumetinib, 5-FU and 5-FU+selumetinib. Cell proliferation was determined using a tetrazolium conversion assay. Mitotic catastrophe and DNA repair were analyzed using immunocytochemistry. Flow cytometry was used to analyze cell cycle and apoptosis. Growth delay was used to determine effects of 5-FU+selumetinib on in vivo tumor radiosensitivity.

RESULTS

Pre-IR treatment with 5-FU+selumetinib significantly decreased clonogenic survival compared with either agent alone. Dose modifying factors at a surviving fraction of 0.1 for 5-FU+selumetinib was 1.78, 1.52, and 1.3 for HT29, HCT116, and MiaPaca-2, respectively. Cell proliferation was decreased by treatment with selumetinib+5-FU as compared with single agent treatment regardless of treatment sequencing. Enhancement of 5-FU cytotoxicity and 5-FU mediated radiosensitization with selumetinib treatment was accompanied by an increase in mitotic catastrophe and apoptosis, and reductions in Stat3 phosphorylation and survivin expression. In vivo, an additive growth delay was observed with 5-FU+selumetinib+3Gy versus 5-FU+3Gy and selumetinib alone.

CONCLUSION

These data suggest that selumetinib can be used with 5-FU to augment radiation response.

Targeting inhibitor of apoptosis proteins for therapeutic intervention

The inhibitors of apoptosis (IAP) proteins have emerged over the last decade as important targets for therapeutic intervention in human malignancies. Overexpression of IAPs has been implicated in cell survival and resistance against stress-induced apoptosis brought on by radiation and/or chemotherapeutics (currently the standard-of-care in a variety of different cancer diseases). In addition, evasion from death receptor-mediated apoptosis and regulation of NF-κB pathways and cell division have also been associated with IAP proteins. Efforts to target IAP proteins in tumors have focused mainly on designing small molecules that mimic the IAP-binding motif of the endogenous IAP antagonist, second mitochondrial activator of caspases. In addition, several other IAP-targeting strategies, including antisense oligonucleotides and transcriptional repression, have also been initiated, with the hope of providing therapeutic benefit to cancer patients.

Survivin is a novel target of CD44-promoted breast tumor invasion

The hyaluronan (HA) receptor CD44 plays an essential role in cell-cell or cell-extracellular matrix communications and is a bioactive signal transmitter. Although a number of studies have described the function of CD44 in breast cancer (BC) metastasis, the underlying mechanisms have yet to be determined. By using a validated tetracycline-off-regulated CD44 expression system in the MCF-7 cell line combined with microarray analysis, we identified survivin (SVV) as a potential downstream transcriptional target of CD44. To test the hypothesis that SVV underpins CD44-promoted BC cell invasion, we combined molecular and pharmacologic approaches and showed that CD44 induction increased SVV expression levels, which in turn promotes BC cell invasion. Further, clinical analysis of breast tissue samples showed that SVV expression patterns paralleled those of the standard form of CD44 during breast tumor progression. More interestingly, we identified the PI3K/E2F1 pathway as a potential molecular link between HA/CD44 activation and SVV transcription. In addition to identifying SVV as a target for HA/CD44 signaling, this investigation provides a better understanding of the molecular mechanisms that underpin the novel function of SVV in breast cancer metastasis.

Metal-free imidazolium salts inhibit the growth of hepatocellular carcinoma in a mouse model

Imidazolium salts (IMSs) are precursors to N-heterocyclic carbenes (NHCs), which are routinely used as ligands or organo-catalysts in synthetic chemistry. We recently identified several IMSs as anti-fibrotic agents in liver fibrosis, which often has a consequence in the oncogenesis of hepatocellular carcinoma (HCC). Here, we investigate the potential anti-tumor property of three IMSs (named IBN-1, IBN-9, and DPIM) in HCC cell lines and in a xenograft mouse model. Our results showed that both IBN-1 and IBN-9 significantly inhibited the cell proliferation and arrested HCC cells in the G1-phase, whereas DPIM did not have any anti-tumor activity. When tested in a Huh7 HCC xenograft mouse model, IBN-1 reduced the tumor volume by 31% (P<0.05), however accompanied by a 9% loss in body weight (P<0.005), suggesting a general toxicity. In contrast, IBN-9 significantly reduced the tumor volume by 45% (P<0.05) and 60% (P<0.01) at doses of 0.6 and 1.5 g/l in drinking water, respectively, without any loss in body weight. Our in vitro and in vivo data suggested that IBN-1 and IBN-9 inhibited the growth of HCC by suppressing the expression of Survivin and Cyclin-dependent kinases. The current study provides a proof of concept for using the metal-free IMSs to develop novel anti-cancer agents.

Terameprocol (tetra-O-methyl nordihydroguaiaretic acid), an inhibitor of Sp1-mediated survivin transcription, induces radiosensitization in non-small cell lung carcinoma

INTRODUCTION

Survivin, an inhibitor of apoptosis protein and key regulator of mitosis, is up-regulated in a variety of cancers and is often associated with a worse prognosis. Terameprocol down-regulates the Sp1-mediated transcription of survivin and Cdk1, which is important for cell cycle progression and many other proteins. Survivin inhibition has previously been shown to result in the induction of apoptosis and radiosensitization.

METHODS

This study examined the effects of terameprocol administration on survivin transcription and expression in HCC2429 and H460 lung cancer cells. We also examined the combined effects of radiation and terameprocol on apoptosis and radiosensitivity.

RESULTS

Using immunoblot analysis and luciferase assays, we confirmed that terameprocol decreases survivin transcription and protein expression. Ultimately, however, decreases in survivin expression failed to correlate with an increase in apoptosis. Nonetheless, clonogenic assay revealed that terameprocol induces increased radiosensitization in HCC2429 (dose enhancement ratio = 1.26, p = 0.019) and H460 (dose enhancement ratio = 1.18, p = 0.001) cells. Additionally, the data show no effect of terameprocol on cell cycle in either HCC2429 or H460 cells.

CONCLUSIONS

Terameprocol significantly enhances the sensitivity of non-small cell lung carcinoma cell lines to radiation therapy, although the mechanism of action remains unclear. Further study is warranted to assess the potential of terameprocol as an agent that may enhance the therapeutic ratio of radiotherapy in lung cancer.