The inhibitor of apoptosis protein Livin (ML-IAP) plays a dual role in tumorigenicity

Modes of Regulated Cell Death in Cancer

Cell suicide pathways, termed regulated cell death (RCD), play a critical role in organismal development, homeostasis, and pathogenesis. Here, we provide an overview of key RCD modalities, namely apoptosis, entosis, necroptosis, pyroptosis, and ferroptosis. We explore how various RCD modules serve as a defense mechanism against the emergence of cancer as well as the manner in which they can be exploited to drive oncogenesis. Furthermore, we outline current therapeutic agents that activate RCD and consider novel RCD-based strategies for tumor elimination. SIGNIFICANCE: A variety of antitumor therapeutics eliminate cancer cells by harnessing the devastating potential of cellular suicide pathways, emphasizing the critical importance of RCD in battling cancer. This review supplies a mechanistic perspective of distinct RCD modalities and explores the important role they play in tumorigenesis. We discuss how RCD modules serve as a double-edged sword as well as novel approaches aimed at selectively manipulating RCD for tumor eradication.

Novel targeted mtLivin nanoparticles treatment for disseminated diffuse large B-cell lymphoma

We previously showed that Livin, an inhibitor of apoptosis protein, is specifically cleaved to produce a truncated protein, tLivin, and demonstrated its paradoxical proapoptotic activity. We further demonstrated that mini-tLivin (MTV), a 70 amino acids derivative of tLivin, is a proapoptotic protein as potent as tLivin. Based on these findings, in this study we aimed to develop a venue to target MTV for the treatment of diffuse large B-cell lymphoma (DLBCL). MTV was conjugated to poly (lactide-co-glycolic acid) surface-activated nanoparticles (NPs). In order to target MTV-NPs we also conjugated CD40 ligand (CD40L) to the surface of the NPs and evaluated the efficacy of the bifunctional CD40L-MTV-NPs. In vitro, CD40L-MTV-NPs elicited significant apoptosis of DLBCL cells. In a disseminated mouse model of DLBCL, 37.5% of MTV-NPs treated mice survived at the end of the experiment. Targeting MTV-NPs using CD40L greatly improved survival and 71.4% of these mice survived. CD40L-MTV-NPs also greatly reduced CNS involvement of DLBCL. Only 20% of these mice presented infiltration of lymphoma to the brain in comparison to 77% of the MTV-NPs treated mice. In a subcutaneous mouse model, CD40L-MTV-NPs significantly reduced tumor volume in correlation with significant increased caspase-3 activity. Thus, targeted MTV-NPs suggest a novel approach to overcome apoptosis resistance in cancer.

The Multiple Roles of the IAP Super-family in cancer

The Inhibitor of Apoptosis proteins (IAPs) are a family of proteins that are mainly known for their anti-apoptotic activity and ability to directly bind and inhibit caspases. Recent research has however revealed that they have extensive roles in governing numerous other cellular processes. IAPs are known to modulate ubiquitin (Ub)-dependent signaling pathways through their E3 ligase activity and influence activation of nuclear factor κB (NF-κB). In this review, we discuss the involvement of IAPs in individual hallmarks of cancer and the current status of therapies targeting these critical proteins.

Targeting the BIR Domains of Inhibitor of Apoptosis (IAP) Proteins in Cancer Treatment

Inhibitor of apoptosis (IAP) proteins are characterized by the presence of the conserved baculoviral IAP repeat (BIR) domain that is involved in protein-protein interactions. IAPs were initially thought to be mainly responsible for caspase inhibition, acting as negative regulators of apoptosis, but later works have shown that IAPs also control a plethora of other different cellular pathways. As X-linked IAP (XIAP), and other IAP, levels are often deregulated in cancer cells and have been shown to correlate with patients' prognosis, several approaches have been pursued to inhibit their activity in order to restore apoptosis. Many small molecules have been designed to target the BIR domains, the vast majority being inspired by the N-terminal tetrapeptide of Second Mitochondria-derived Activator of Caspases/Direct IAp Binding with Low pI (Smac/Diablo), which is the natural XIAP antagonist. These compounds are therefore usually referred to as Smac mimetics (SMs). Despite the fact that SMs were intended to specifically target XIAP, it has been shown that they also interact with cellular IAP-1 (cIAP1) and cIAP2, promoting their proteasome-dependent degradation. SMs have been tested in combination with several cytotoxic compounds and are now considered promising immune modulators which can be exploited in cancer therapy, especially in combination with immune checkpoint inhibitors. In this review, we give an overview of the structural hot-spots of BIRs, focusing on their fold and on the peculiar structural patches which characterize the diverse BIRs. These structures are exploited/exploitable for the development of specific and active IAP inhibitors.

Expression of antiapoptotic proteins livin and survivin in pediatric AML patients, as prognostic markers

OBJECTIVE

Survivin and livin are highly expressed in various malignancies and their expression levels may be related to unfavorable prognosis. The aim was to investigate the relationships of these two markers with some prognostic factors and with survival of the children with acute myeloid leukemia (AML).

METHODS

Livin and survivin expression was investigated quantitatively by immunohistochemistry staining technique in 43 primary formalin-fixed, paraffin-embedded bone marrow blocks in pediatric age group (<18 years).

RESULTS

Both survivin and livin were expressed in 81.4% of AML patients. Livin expression showed significant positive association with high level of primary WBC (p = .002). Survivin expression showed significant positive correlations with risk of relapse (p ≤ .001) and high level of primary WBC (p = .003). The relationship of overall survival (OS) of the patients with livin and survivin expression, were investigated separately in disease subtypes. Significant association was observed between survivin expression and shorter OS regardless of subtypes including acute promyelocytic (APL) (p = .01) and nonacute promyelocytic leukemia (non-APL) (p = .008). Also, significant association of livin expression with shorter OS was detected, but only in APL subgroup (p = .046). Nevertheless, in Cox regression model after adjusting for disease subtypes, stage and cytogenetics; survivin and livin showed no significant association with OS (p > .05).

CONCLUSION

Livin and survivin showed significant associations with some poor prognostic factors of AML. Although survivin in both subtypes and livin in non APL subtype, showed a significant relationship with shorter OS, none of them was determined as independent prognostic factors. Further studies with larger sample size are suggested.

Livin/BIRC7 expression as malignancy marker in adrenocortical tumors

Livin/BIRC7 is a member of the inhibitors of apoptosis proteins family, which are involved in tumor development through the inhibition of caspases. Aim was to investigate the expression of livin and other members of its pathway in adrenocortical tumors and in the adrenocortical carcinoma (ACC) cell line NCI-H295R.

The mRNA expression of livin, its isoforms α and β, XIAP, CASP3 and DIABLO was evaluated by qRT-PCR in 82 fresh-frozen adrenal tissues (34 ACC, 25 adenomas = ACA, 23 normal adrenal glands = NAG). Livin protein expression was assessed by immunohistochemistry in 270 paraffin-embedded tissues (192 ACC, 58 ACA, 20 NAG). Livin, CASP3 and cleaved caspase-3 were evaluated in NCI-H295R after induction of livin overexpression.

Relative livin mRNA expression was significantly higher in ACC than in ACA and NAG (0.060 ± 0.116 vs 0.004 ± 0.014 and 0.002 ± 0.009, respectively, p < 0.01), being consistently higher in tumors than in adjacent NAG and isoform β more expressed than α. No significant differences in CASP3, XIAP and DIABLO levels were found among these groups. In immunohistochemistry, livin was localized in both cytoplasm and nuclei. The ratio between cytoplasmic and nuclear staining was significantly higher in ACC (1.51 ± 0.66) than in ACA (0.80 ± 0.35) and NAG (0.88 ± 0.27; p < 0.0001). No significant correlations were observed between livin expression and histopathological parameters or clinical outcome. In NCI-H295R cells, the livin overexpression slightly reduced the activation of CASP3, but did not correlate with cell viability.

In conclusion, livin is specifically over-expressed in ACC, suggesting that it might be involved in adrenocortical tumorigenesis and represent a new molecular marker of malignancy.

Paramyxoviruses activation by host proteases in cultures of normal and cancer cells

Multiplication of paramyxovirus Sendai and Newcastle disease virus (NDV) was studied in cultures of normal and tumor cells. Production of noninfectious virus with uncleaved F0 was observed in canine kidney cell line MDCK (line H) and its derivatives carrying tetracycline-regulated expression of transmembrane protease HAT or TMPRSS2 with trypsin-like cleavage specificity. Under tetracycline induction, a cleavage F0 (65 kD)>F1 (50 kD)+F2(15 kD) and production of infectious virus were observed in these cell cultures. Under tetracycline induction, the additional subunit 38K (m.w. 38 kDa) of the F protein was detected both in infected MDCK-HAT cells and in newly synthesized Sendai virus in addition to F0, F1 and F2, indicating thereby a second HAT-sensitive proteolytic site in the F0 molecule. Highly infectious virus containing cleaved F1+F2 was produced in cultures of cancer cells Caco-2 and H1299. Virus Sendai synthesized in H1299 cells contained 38 K subunit indicating a cleavage of the F0 at a second site by H1299 host cell proteases. Levels of cleaved F1+F2 and infectious virions were higher at the late stage of infection in cancer cells, suggesting thus the induction of virus-activating proteases in Caco-2 and H1299 cells under infection with paramyxoviruses. NDV virus was found to induce more rapid death of cancer cells Caco-2 than Sendai virus. Cooperatively, the obtained data show that cancer cells in distinction to nonmalignant cells can synthesize protease(s) activating infectivity of paramyxoviruses. Thus, they are more vulnerable to paramyxovirus infection than normal cells.

Targeting Cell Survival Proteins for Cancer Cell Death

Escaping from cell death is one of the adaptations that enable cancer cells to stave off anticancer therapies. The key players in avoiding apoptosis are collectively known as survival proteins. Survival proteins comprise the Bcl-2, inhibitor of apoptosis (IAP), and heat shock protein (HSP) families. The aberrant expression of these proteins is associated with a range of biological activities that promote cancer cell survival, proliferation, and resistance to therapy. Several therapeutic strategies that target survival proteins are based on mimicking BH3 domains or the IAP-binding motif or competing with ATP for the Hsp90 ATP-binding pocket. Alternative strategies, including use of nutraceuticals, transcriptional repression, and antisense oligonucleotides, provide options to target survival proteins. This review focuses on the role of survival proteins in chemoresistance and current therapeutic strategies in preclinical or clinical trials that target survival protein signaling pathways. Recent approaches to target survival proteins-including nutraceuticals, small-molecule inhibitors, peptides, and Bcl-2-specific mimetic are explored. Therapeutic inventions targeting survival proteins are promising strategies to inhibit cancer cell survival and chemoresistance. However, complete eradication of resistance is a distant dream. For a successful clinical outcome, pretreatment with novel survival protein inhibitors alone or in combination with conventional therapies holds great promise.

Targeting Cell Survival Proteins for Cancer Cell Death

Escaping from cell death is one of the adaptations that enable cancer cells to stave off anticancer therapies. The key players in avoiding apoptosis are collectively known as survival proteins. Survival proteins comprise the Bcl-2, inhibitor of apoptosis (IAP), and heat shock protein (HSP) families. The aberrant expression of these proteins is associated with a range of biological activities that promote cancer cell survival, proliferation, and resistance to therapy. Several therapeutic strategies that target survival proteins are based on mimicking BH3 domains or the IAP-binding motif or competing with ATP for the Hsp90 ATP-binding pocket. Alternative strategies, including use of nutraceuticals, transcriptional repression, and antisense oligonucleotides, provide options to target survival proteins. This review focuses on the role of survival proteins in chemoresistance and current therapeutic strategies in preclinical or clinical trials that target survival protein signaling pathways. Recent approaches to target survival proteins-including nutraceuticals, small-molecule inhibitors, peptides, and Bcl-2-specific mimetic are explored. Therapeutic inventions targeting survival proteins are promising strategies to inhibit cancer cell survival and chemoresistance. However, complete eradication of resistance is a distant dream. For a successful clinical outcome, pretreatment with novel survival protein inhibitors alone or in combination with conventional therapies holds great promise.

Therapeutic potential of oncolytic Newcastle disease virus: a critical review

Newcastle disease virus (NDV) features a natural preference for replication in many tumor cells compared with normal cells. The observed antitumor effect of NDV appears to be a result of both selective killing of tumor cells and induction of immune responses. Genetic manipulations to change viral tropism and arming the virus with genes encoding for cytokines improved the oncolytic capacity of NDV. Several intracellular proteins in tumor cells, including antiapoptotic proteins (Livin) and oncogenic proteins (H-Ras), are relevant for the oncolytic activity of NDV. Defects in the interferon system, found in some tumor cells, also contribute to the oncolytic selectivity of NDV. Notwithstanding, NDV displays effective oncolytic activity in many tumor types, despite having intact interferon signaling. Taken together, several cellular systems appear to dictate the selective oncolytic activity of NDV. Some barriers, such as neutralizing antibodies elicited during NDV treatment and the extracellular matrix in tumor tissue appear to interfere with spread of NDV and reduce oncolysis. To further understand the oncolytic activity of NDV, we compared two NDV strains, ie, an attenuated virus (NDV-HUJ) and a pathogenic virus (NDV-MTH-68/H). Significant differences in amino acid sequence were noted in several viral proteins, including the fusion precursor (F0) glycoprotein, an important determinant of replication and pathogenicity. However, no difference in the oncolytic activity of the two strains was noted using human tumor tissues maintained as organ cultures or in mouse tumor models. To optimize virotherapy in clinical trials, we describe here a unique organ culture methodology, using a biopsy taken from a patient’s tumor before treatment for ex vivo infection with NDV to determine the oncolytic potential on an individual basis. In conclusion, oncolytic NDV is an excellent candidate for cancer therapy, but more knowledge is needed to ensure success in clinical trials.

Inhibition of livin expression suppresses cell proliferation and enhances chemosensitivity to cisplatin in human lung adenocarcinoma cells

Livin is a novel member of the inhibitor of apoptosis protein family that has been reported to be overexpressed in various types of human malignancy. Although several studies have demonstrated that livin may be used as an effective target for tumor therapy, few studies have investigated its role in human lung adenocarcinoma. In the present study, two different methods were used in order to investigate the tumor‑suppressing effect of livin in human lung adenocarcinoma cells. Firstly, small interfering (si)RNA technology was used to down regulate livin expression; siRNA-mediated knockdown of livin was confirmed using reverse transcription quantitative polymerase chain reaction and western blot analysis, and cell proliferations was assessed using an MTT assay in vitro. Secondly, inhibition of livin expression was induced through the synergistic inhibitory effect between flavopiridol and tumor necrosis factor‑related apoptosis-inducing ligand (TRAIL). Experimental results revealed that, following transfection of the livin gene-silencing vector, the gene expression of livin was markedly decreased, SPC-A1 cell proliferation was significantly reduced and the therapeutic effect of the chemotherapy drug cisplatin was markedly improved. This growth inhibitory effect was also observed in the flavopiridol and TRAIL combination treatment group. In the flavopiridol and TRAIL combination treatment group, the protein expression of livin was significantly reduced and the survival rate of SPC‑A1 cells was significantly lower than the flavopiridol and TRAIL single operation group. In conclusion, the RNA silencing and the synergistic inhibitory effect between flavopiridol with TRAIL was able to effectively inhibit the expression of livin, significantly decrease SPC-A1 tumor cell proliferation and significantly enhance sensitivity to the chemotherapy drug cisplatin. These findings suggest that livin may be used as a novel target for tumor gene therapy.

Expression of the apoptosis inhibitor livin in colorectal adenoma-carcinoma sequence: correlations with pathology and outcome

The inhibitor of apoptosis family member livin is expressed in several types of cancer but not in most benign tissues, and it has been considered to be a poor prognostic mark in various malignancies. However, livin expression and its prognostic relevance have not been evaluated in colorectal adenoma-carcinoma sequence. In this study, we analyzed the difference of livin expression among normal mucosa, adenoma, and adenocarcinoma and investigated the relationship of livin expression in carcinomas with clinicopathological variables using immunohistochemistry and real-time reverse transcription-PCR. We observed that the expression of livin protein was mainly present on base of colorectal crypts in adenoma and throughout the epithelium in carcinoma, whereas did not present in accompanying normal mucosa, and the expression of livin messenger RNA (mRNA) in adenocarcinomas was significantly higher than in adenomas and in normal mucosa (P = 0.001, respectively), whereas, compared with normal mucosa, the expression level of livin mRNA was up-regulated in adenomas but no significant difference (P = 0.196). We also found that the expression levels of livin mRNA in rectal cancer was significantly higher than those in colonic cancer, and livin mRNA expression was strongly related to colorectal cancer invasive depth but not to clinical tumor stage, differentiation, lymph node metastasis, tumor morphological category and pathological type, and patient's age and gender. These findings support the possibility that the livin gene may play a role in colorectal tumorigenesis, and increased expression of livin mRNA may serve as a new target for colorectal cancer treatment.

tLivin displays flexibility by promoting alternative cell death mechanisms

Livin is a member of the Inhibitor of Apoptosis (IAP) protein family that inhibits apoptosis triggered by a variety of stimuli. We previously demonstrated that while Livin inhibits caspase activity, caspases can cleave Livin to produce a truncated protein, tLivin and that this newly formed tLivin paradoxically induces cell death. However to date, the mechanism of tLivin-induced cell death is not fully understood. In this study, we set out to characterize the form of cell death mediated by tLivin. Here we demonstrate that, unlike most death-promoting proteins, tLivin is a flexible inducer of cell death capable of promoting necrosis or apoptosis in different cell lines. The unusual flexibility of tLivin is displayed by its ability to activate an alternative form of cell death when apoptosis is inhibited. Thus, tLivin can promote more than one form of cell death in the same cell type. Interestingly, in cells where tLivin induces necrosis, deletion of the caspase binding BIR domain results in tLivin-induced apoptosis, suggesting the BIR domain can potentially hamper the ability of tLivin to induce apoptosis. We further elucidate that tLivin activates the JNK pathway and both tLivin-induced apoptosis and necrosis are partially mediated by JNK activity. Acquired resistance to apoptosis, common in many tumors, impinges on the efficiency of conventional anti-cancer agents that function primarily by inducing apoptosis. The ability of tLivin to induce death of apoptosis-compromised cells makes it an attractive candidate for targeted cancer therapy.

Chalcones with electron-withdrawing and electron-donating substituents: anticancer activity against TRAIL resistant cancer cells, structure-activity relationship analysis and regulation of apoptotic proteins

In the present study, a series of 46 chalcones were synthesised and evaluated for antiproliferative activities against the human TRAIL-resistant breast (MCF-7, MDA-MB-231), cervical (HeLa), ovarian (Caov-3), lung (A549), liver (HepG2), colorectal (HT-29), nasopharyngeal (CNE-1), erythromyeloblastoid (K-562) and T-lymphoblastoid (CEM-SS) cancer cells. The chalcone 38 containing an amino (-NH2) group on ring A was the most potent and selective against cancer cells. The effects of the chalcone 38 on regulation of 43 apoptosis-related markers in HT-29 cells were determined. The results showed that 20 apoptotic markers (Bad, Bax, Bcl-2, Bcl-w, Bid, Bim, CD40, Fas, HSP27, IGF-1, IGFBP-4, IGFBP-5, Livin, p21, Survivin, sTNF-R2, TRAIL-R2, XIAP, caspase-3 and caspase-8) were either up regulated or down regulated.

Differential regulation of the apoptotic machinery during megakaryocyte differentiation and platelet production by inhibitor of apoptosis protein Livin

Livin is a member of the inhibitor of apoptosis proteins (IAP) family of intracellular antiapoptotic proteins that act by binding and inhibiting caspases. Upon strong apoptotic stimuli, it is then specifically cleaved by caspases to produce a truncated protein (tLivin) with a paradoxical proapoptotic activity. Intriguingly, we have detected robust protein levels of Livin in normal mature bone marrow megakaryocyte (MK) and platelets. To evaluate the potential role of Livin in thrombopoiesis, we used the human BCR-ABL+ cell line, LAMA-84, and cord blood CD34+ cells to induce differentiation toward MKs. Upon differentiation, induced by phorbol myristate acetate and concurrent with increase in Livin protein expression, LAMA-84 cells formed functional platelet-like particles. Livin overexpression in CD34+ progenitor cells induced higher endoreplication in the MKs generated. Furthermore, overexpression of Livin increased the ability of both primary MKs and differentiated LAMA-84 cells to produce functional platelets. In the differentiated LAMA-84 cells, we observed accumulation of proapoptotic tLivin concomitant with increased caspase-3 activity. Downregulation of Livin with small interfering RNA in both leukemic and primary MK cells decreased their ability to produce functional platelets. We suggest that Livin has a role in thrombopoiesis by regulating the apoptotic and antiapoptotic balance in MK endoreplication and platelet production.

Knockdown of Livin inhibits growth and invasion of gastric cancer cells through blockade of the MAPK pathway in vitro and in vivo

Livin, a novel member of the human inhibitors of apoptosis protein family, has been shown to be critical for tumor progression and poor prognosis for several types of malignancies. However, limited reports exist regarding the biological functions of Livin in human gastric cancer (GC). The present study investigated the clinical significance of Livin and caspase-3 (CAS-3) in human GC using immunohistochemistry assay, and explore the potential using RNA interference to knockdown Livin expression, including the subsequent effects on tumor growth and invasion in GC cells in vitro and in vivo. Our results showed that the rate of positive expression of Livin was significantly higher in GC tissues compared to that in adjacent non-cancer tissues (ANCT) (64.1 vs. 30.8%, P<0.001), while CAS-3 was lower in GC tissues than in ANCT (33.3 vs. 66.7%, P=0.001). Livin expression was positively correlated with tumor differentiation and lymph node metastases (P=0.009; P=0.007), while CAS-3 was negatively correlated with them (P=0.036; P=0.002) in patients with GC. Furthermore, knockdown of Livin inhibited cell proliferative activities and invasive potential, and induced cell in situ apoptosis in GC cells, accompanied with decreased expression of p38 MAPK, VEGF and MMP-2 and increased expression of CAS-3. In addition, the tumor volumes in the SGC7901 subcutaneous nude mouse model treated with Lv-shLivin was significantly smaller compared to those of the PBS group (P<0.01). Taken together, our findings indicate that the expression of Livin is increased in human GC and correlates with tumor differentiation and lymph node metastases, while knockdown of Livin inhibits cell growth and invasion through blockade of the MAPK pathway in GC cells, suggesting that Livin may be a potential therapeutic target for the treatment of GC.

Saponin B, a novel cytostatic compound purified from Anemone taipaiensis, induces apoptosis in a human glioblastoma cell line

Glioblastoma multiforme (GBM) is one of the most common malignant brain tumors. Saponin B, a novel compound isolated from the medicinal plant, Anemone taipaiensis, has been found to have a strong time- and dose-dependent cytostatic effect on human glioma cells and to suppress the growth of U87MG GBM cells. In this study, we investigated whether saponin B induces the apoptosis of glioblastoma cells and examined the underlying mechanism(s) of action of saponin B. Saponin B significantly suppressed U87MG cell proliferation. Flow cytometric analysis of DNA in the U87MG cells confirmed that saponin B blocked the cell cycle at the S phase. Furthermore, treatment of the U87MG cells with saponin B induced chromatin condensation and led to the formation of apoptotic bodies, as observed under a fluorescence microscope, and Annexin V/PI assay further suggested that phosphatidylserine (PS) externalization was apparent at higher drug concentrations. Treatment with saponin B activated the receptor-mediated pathway of apoptosis, as western blot analysis revealed the activation of Fas-l. Saponin B increased the Bax and caspase-3 ratio and decreased the protein expression of Bcl-2. The results from the present study demonstrate that the novel compound, saponin B, effectively induces the apoptosis of GBM cells and inhibits glioma cell growth and survival. Therefore, saponin B may be a potential candidate for the development of novel cancer therapeutics with antitumor activity against gliomas.

Expedient synthesis of highly potent antagonists of inhibitor of apoptosis proteins (IAPs) with unique selectivity for ML-IAP

A series of novel, potent antagonists of the inhibitor of apoptosis proteins (IAPs) were synthesized in a highly convergent and rapid fashion (≤6 steps) using the Ugi four-component reaction as the key step, thus enabling rapid optimization of binding potency. These IAP antagonists compete with caspases 3, 7, and 9 for inhibition by X chromosome-linked IAP (XIAP) and bind strongly (nanomolar binding constants) to several crucial members of the IAP family of cancer pro-survival proteins to promote apoptosis, with a particularly unique selectivity for melanoma IAP (ML-IAP). Experiments in cell culture revealed powerful cancer cell growth inhibitory activity in multiple (breast, ovarian, and prostate) cell lines with single agent toxicity at low nanomolar levels against SKOV-3 human ovarian carcinoma cells. Administration of the compounds to human foreskin fibroblast cells revealed no general toxicity to normal cells. Furthermore, computational modeling was performed, revealing key contacts between the IAP proteins and antagonists, suggesting a structural basis for the observed potency.

Livin expression may be regulated by miR-198 in human prostate cancer cell lines

Livin has been recently described as an inhibitor of apoptosis, which is established to be associated with a variety of cancers. Metastatic prostate cancer cell line DU145 expresses high level of Livin mRNA yet low level of its protein. Thus, we hypothesised that Livin was regulated by some miRNAs in prostate cancer cells. Livin mRNA and protein expression were investigated by reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blot, respectively. Hairpin RT-PCR was performed to analyse suspected miRNAs. Livin 3'-untranslated region (3'-UTR) wild type and mutant dual-luciferase reporter vectors were constructed. The miRNAs targeting Livin were predicted by the online software - TargetScan and miRBase, and then validated by dual luciferase reporter gene assay. We found that post-transcriptional inhibition of Livin occurred in DU145 cells, assumedly due to the miRNA pathway. Among 6 candidate miRNAs, miR-198 expression was identified to be negatively correlated with Livin expression level in some prostate cancer cell lines. Further study revealed miR-198-mediated repression of Livin expression. Therefore, the regulation of Livin expression may involve miR-198 in prostate cancer cell lines.

Extracellular matrix constituents interfere with Newcastle disease virus spread in solid tissue and diminish its potential oncolytic activity

Advanced melanoma cells, characterized by resistance to chemotherapy, have been shown to be highly sensitive to oncolysis by Newcastle disease virus (NDV). In the present study, we investigated the capacity of NDV to specifically infect and spread into solid tissues of human melanoma and lung carcinoma, in vivo and ex vivo. For this purpose a new model of SCID-beige mice implanted with human melanoma was developed. Surprisingly, the replication competent NDV-MTH and the attenuated, single-cycle replication NDV-HUJ strains, demonstrated a similar oncolytic activity in the melanoma-implanted mice. Further, ex vivo analysis, using organ cultures derived from the melanoma tissues indicated a limited spread of the two NDV strains in the tissue. Extracellular matrix (ECM) molecules, notably heparin sulfate and collagen, were found to limit viral spread in the tissue. This observation was validated with yet another solid tumour of human lung carcinoma. Taken together, the results indicate that the ECM acts as a barrier to virus spread within solid tumour tissues and that this restriction must be overcome to achieve effective oncolysis with NDV.

The clinical effect of the inhibitor of apopotosis protein livin in melanoma

OBJECTIVE

The inhibitor of apoptosis protein (IAP) livin is frequently overexpressed in melanoma. Livin binds caspases and thereby inhibits apoptosis. We found that caspases cleave livin to produce a truncated form with a paradoxical proapoptotic activity.

METHODS

We assessed the correlation of livin expression with survival among 114 melanoma patients treated with an autologous melanoma vaccine. In 52 patients, resection resulted in no evidence of disease (NED) and 62 remained with active disease (WAD). Protein levels were assessed using Western blot.

RESULTS

We found livin protein expression in 44/114 samples (38.4%). Median overall survival was 1.4 years in NED patients with high levels of livin protein, 8.4 years in those with low-intermediate levels and not reached in patients who did not express livin (p = 0.025). The corresponding overall survival was 2.3 years among WAD patients with high levels of livin protein, 11.3 years in those with low-intermediate levels and, paradoxically, only 4.0 years in patients who did not express livin (p = 0.012).

CONCLUSION

Livin protein expression may play a role in the progression of melanoma and correlates with survival. A high level of the protein is associated with a poor prognosis. However, in WAD patients low to intermediate level of livin, rather than absence of the protein, is associated with a favorable prognosis. This is probably due to the paradoxical proapoptotic activity of this important regulator of apoptosis.

siRNA directed against Livin inhibits tumor growth and induces apoptosis in human glioma cells

Livin, a novel member of the human inhibitors of apoptosis protein family, plays an important role in tumor progression and occurrence by inhibiting cell apoptosis. It is selectively expressed in the most common human neoplasms and appears to be involved in tumor cell resistance to chemotherapeutic agents. The present study was designed to investigate the potential of using RNA interference (RNAi) technique to downregulate Livin expression, and the subsequent effect on human glioma cells. The results showed that knockdown of Livin expression by short interfering RNA (siRNA) significantly inhibited glioma cell proliferation and increased cell apoptosis through cell arrest in the G(1)/G(0) phase of cell cycle in vitro. Furthermore, Livin siRNA significantly suppressed tumor growth in nude mice. Together, these findings suggest that RNAi-mediated downregulation of Livin expression could lead to potent antitumor activity in glioma cells and might serve as a novel therapeutic strategy in clinic.

Livin-α promotes cell proliferation by regulating G1-S cell cycle transition in prostate cancer

BACKGROUND

Prostate cancer is the third most common cancer and the second leading cause of cancer death for males in US. Livin has recently been described as a cancer-associated member of inhibitor of apoptosis proteins family, highly expressed in prostate cancer. Livin gene encodes two splicing variants, termed Livin-α and Livin-β. We hypothesized that deregulation of proliferation could be due in part to Livin expression.

METHODS

Pathological analysis of Livin was performed in 20 prostate cancer tissues and 5 benign prostatic hyperplasia tissues. The expression of Livin isoforms was also investigated by Western blot in prostate cancer cell lines LNCaP and PC3. The role of Livin-α in vitro was further studied. Using Livin-α knockdown and overexpression models, cell cycle analysis, Ki-67 immunocytostaining, and MTT assay were performed respectively.

RESULTS

Livin expression positive ratio was shown to be 5.4%, 23.6%, 52.4%, 73.4% in benign prostatic hyperplasia, low, medium, and high grade of prostate cancer respectively, and Livin was positively correlated with clinical pathological grades of prostate cancer. Livin-α was expressed in both LNCaP and PC3; meanwhile; Livin-β was only detected in the PC3. Livin-α siRNA not only resulted in G(1)-S cell cycle arrest, but also strongly correlated with the descended proliferation index and survival rate in LNCaP. In comparison, overexpression of Livin-α resulted in an accelerated S phase entry combined with elevated proliferation index and survival in LNCaP.

CONCLUSIONS

Livin-α may promote cell proliferation by regulating G(1)-S cell cycle transition and possibly play an important part in initiation of prostate cancer.

Expression and functional role of inhibitor-of-apoptosis protein livin (BIRC7) in neuroblastoma

We evaluated the expression of the inhibitor-of-apoptosis protein (IAP)livin (BIRC7)in 59 cases ofneuroblastoma (NBL) by quantitative RT-PCR. We also examined the role of livin in protecting tumor cells from chemotherapy drugs. Livin expression varied significantly amongtumors. High levels of expression were observed in 17 of 39 patients with advanced stages (stages 3 and 4) and 6 of 20 patients with localized stages (stages 1 and 2). Livin-transfected, MYCN-amplified NBL cells showed increased resistance to doxorubicin and etoposide. Conversely, livin knockdown with siRNA enhanced spontaneous and drug-induced apoptosis in NBL cells. Multivariate analysis of prognostic factors showed that high livin expression worsened prognosis for patients with MYCN-amplified tumors. Our data suggest that (i) livin is frequently expressed in NBL and protects tumor cells with amplified MYCN oncogene from genotoxic agents; (ii) the antiapoptotic effect of livin in NBL is blocked by siRNA; (iii) in the sample studied, high livin expression enhanced the adverse prognostic impact of MYCN amplification. These findings suggest that livin may contribute to drug resistance in NBL.

Isolation of peptides blocking the function of anti-apoptotic Livin protein

Livin (ML-IAP) is a cancer-associated member of the inhibitor of apoptosis protein (IAP) family. By yeast two-hybrid screening of a randomized peptide expression library, we isolated short linear peptides that specifically bind to Livin, but not to other IAPs. Intracellular expression of the peptides sensitized livin-expressing cancer cells toward different pro-apoptotic stimuli. The bioactive peptides neither showed sequence homologies to Smac-derived IAP inhibitors, nor did they interfere with the binding of Livin to Smac. Intracellular expression of the peptides did not affect the levels or the subcellular distribution of Livin. Growth of livin-expressing tumor cells was inhibited in colony formation assays by the Livin-targeting peptides. These findings provide evidence that the targeted inhibition of Livin by peptides represents a viable approach for the apoptotic sensitization and growth inhibition of tumor cells. The inhibitory peptides isolated here could form a novel basis for the development of therapeutically useful Livin inhibitors.

The oncolytic activity of Newcastle disease virus NDV-HUJ on chemoresistant primary melanoma cells is dependent on the proapoptotic activity of the inhibitor of apoptosis protein Livin

Patients with advanced melanoma usually do not benefit from conventional chemotherapy treatment. There is therefore a true need for a new kind of therapy for melanoma. One factor responsible for the poor prognosis of melanoma is the inhibitor of apoptosis protein (IAP) family member Livin. In this study, we applied a novel approach for the treatment of melanoma, using a unique strain of the oncolytic Newcastle disease virus (NDV-HUJ). We found that, unlike chemotherapeutic drugs, NDV-HUJ, a one-cycle replicating virus, overcomes the resistance to apoptosis of melanoma primary cultures that over express the Livin protein. In contrast, melanoma tumor cells that do not express Livin are relatively resistant to NDV-HUJ treatment. Furthermore, we show that NDV-HUJ-induced oncolysis is attributed to the dual function of Livin: although Livin inhibits apoptosis through the inhibition of caspases, under the robust apoptotic stimulation of NDV-HUJ, caspases can cleave Livin to create a truncated protein with a paradoxical proapoptotic activity. Thus, NDV-HUJ is a potent inducer of apoptosis that can overcome the antiapoptotic effect of Livin and allow cleavage of Livin into the proapoptotic tLivin protein. Moreover, the results indicate that the interferon system, which is functional in melanoma, is not involved in NDV-induced oncolysis. Taken together, our data offer the possibility of a new viral oncolytic treatment for chemoresistant melanoma.