The BIRC6 gene as a novel target for therapy of prostate cancer: dual targeting of inhibitors of apoptosis

A Ubiquitination Cascade Regulating the Integrated Stress Response and Survival in Carcinomas

Systematic identification of signaling pathways required for the fitness of cancer cells will facilitate the development of new cancer therapies. We used gene essentiality measurements in 1,086 cancer cell lines to identify selective coessentiality modules and found that a ubiquitin ligase complex composed of UBA6, BIRC6, KCMF1, and UBR4 is required for the survival of a subset of epithelial tumors that exhibit a high degree of aneuploidy. Suppressing BIRC6 in cell lines that are dependent on this complex led to a substantial reduction in cell fitness in vitro and potent tumor regression in vivo. Mechanistically, BIRC6 suppression resulted in selective activation of the integrated stress response (ISR) by stabilization of the heme-regulated inhibitor, a direct ubiquitination target of the UBA6/BIRC6/KCMF1/UBR4 complex. These observations uncover a novel ubiquitination cascade that regulates ISR and highlight the potential of ISR activation as a new therapeutic strategy.

SIGNIFICANCE

We describe the identification of a heretofore unrecognized ubiquitin ligase complex that prevents the aberrant activation of the ISR in a subset of cancer cells. This provides a novel insight on the regulation of ISR and exposes a therapeutic opportunity to selectively eliminate these cancer cells. See related commentary Leli and Koumenis, p. 535. This article is highlighted in the In This Issue feature, p. 517.

Exploring the Role of the Inhibitor of Apoptosis BIRC6 in Breast Cancer: A Database Analysis

PURPOSE

The aim of the present work was to investigate the role of apoptosis inhibitor BIRC6 (baculoviral IAP repeat-containing protein 6) in breast cancer (BC), focusing particularly on its involvement in the metastatic cascade.

METHODS

We analyzed BIRC6 mRNA expression levels and copy number variations in three BC databases from The Cancer Genome Atlas comparing clinical and molecular attributes. Genomic analysis was performed using the cBioPortal platform, whereas transcriptomic studies (mRNA expression levels, correlation heatmaps, survival plots, and gene ontology) were performed using USC Xena and R. Statistical significance was set at P < .05.

RESULTS

Our bioinformatic analyses showed that there was a differential expression of BIRC6 in cancer samples when compared with normal samples. Copy number variations that involve amplification and gain of BIRC6 gene were correlated with negative hormone receptor tumors, higher prognostic indexes, younger age at diagnosis, and both chemotherapy and radiotherapy administration. Transcriptomic and gene ontology analyses showed that, under conditions of high BIRC6 mRNA levels, there are differential expression patterns in apoptotic, proliferation, and metastatic pathways.

CONCLUSION

In summary, our in silico data suggest that BIRC6 plays an antiapoptotic, pro-proliferative, and apparent prometastatic role and could be a relevant molecular target for treatment of BC tumors.

Oral Squamous Cell Carcinoma: The Role of BIRC6 Serum Level

Background

Different factors are involved in the incidence, etiology, metastasis, diagnosis, and treatment of oral squamous cell carcinoma, including apoptosis inhibitor proteins. Baculoviral IAP repeat containing protein 6 (BIRC6) is one of the apoptosis inhibitor proteins contributing to cancer cells' survival in many cancer types with diagnostic and treatment importance. This study is aimed at assessing the serum level of BIRC6 in oral squamous cell carcinoma.

Materials and Methods

In this retrospective cross-sectional study, 60 serum samples were collected from 45 male and 15 female patients with a mean age of 61 years as the case group and 28 serum samples of healthy people as a control group. The serum samples were analyzed using a commercial sandwich ELISA kit.

Results

There were no significant differences between BIRC6 serum levels in patients and healthy subjects. Moreover, we did not observe any significant relationships between BIRC6 serum levels and the patients' demographic or clinical characteristics.

Conclusions

There was no significant difference in serum BIRC6 levels in patients with oral squamous cell carcinoma and healthy individuals. Its use in determining the prognosis of squamous cell carcinoma or considering it a determinant marker in this type of cancer may not have a place. More in-depth studies for evaluating BIRC6 serum levels in oral squamous cell carcinoma patients are recommended for better insight into this protein's role in diagnosing, progression, and prognosis of the disease.

Overexpression of BIRC6 driven by EGF-JNK-HECTD1 signaling is a potential therapeutic target for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive and highly lethal disease. The lack of targeted therapies and poor patient outcome have fostered efforts to discover new molecular targets to treat patients with TNBC. Here, we showed that baculoviral IAP repeat containing 6 (BIRC6) is overexpressed and positively correlated with epidermal growth factor (EGF) receptor (EGFR) in TNBC cells and tissues and that BIRC6 overexpression is associated with poor patient survival. Mechanistic studies revealed that BIRC6 stability is increased by EGF-JNK signaling, which prevents ubiquitination and degradation of BIRC6 mediated by the E3 ubiquitin ligase HECTD1. BIRC6 in turn decreases SMAC expression by inducing the ubiquitin-proteasome pathway, thereby antagonizing apoptosis and promoting the proliferation, colony formation, tumorsphere formation, and tumor growth capacity of TNBC cells. Therapeutically, the PEGylated cationic lipid nanoparticle (pCLN)-assisted delivery of BIRC6 small interfering RNA (siRNA) efficiently silences BIRC6 expression in TNBC cells, thus suppressing TNBC cell growth in vitro and in vivo, and its antitumor activity is significantly superior to that of the EGFR inhibitor gefitinib. Our findings identify an important regulatory mechanism of BIRC6 overexpression and provide a potential therapeutic option for treating TNBC.

Bioinformatics Prediction and Analysis of MicroRNAs and Their Targets as Biomarkers for Prostate Cancer: A Preliminary Study

Prostate cancer (PCa) is the second most common form of cancer in men around the world. Due to its heterogeneity, presentations range from aggressive lethal disease to indolent disease. There is a need to identify core biomarkers that are important for early detection and progression, allowing a more precise method for the treatment and management of Pca. We obtained metastatic prostate cancer associated microRNA array profiles from the GSE28029 dataset in the GEO database. MicroRNA target prediction was done using the databases, TargetScanHuman, miRDB and DIANA microT, six target genes (FOXC1, CDKN1A, BIRC2, CTNND1, ELK1 and LRP8) were found to be common among the three different databases. Differential expression of the target genes was performed via the GENT2 database in the GPL96 platform (HG-U133A). Results indicated all genes were downregulated. Gene Ontology (GO) was used to perform enrichment analysis. The GO enrichment analysis indicated that the downregulated genes were enriched in cellular response to gamma radiation, regulation of transcription and response to drugs as well as protein binding and receptor signaling protein activity. The study suggested that CDKN1A, FOXC1 and BIRC2 might be core genes for prostate cancer that play an important role in its diagnosis, development and progression.

Silencing circ‑BIRC6 inhibits the proliferation, invasion, migration and epithelial‑mesenchymal transition of bladder cancer cells by targeting the miR‑495‑3p/XBP1 signaling axis

Circular RNAs (circRNAs) regulate gene expression by acting as a 'sponge' for microRNAs (miRs) and play crucial roles in tumorigenesis, including in bladder cancer (BC). circRNA‑baculoviral IAP repeat‑containing 6 (circ‑BIRC6) has been reported to participate in the pathogenesis of several cancer types. The present study aimed to elucidate the roles and potential mechanisms of circ‑BIRC6 in the progression of BC. circ‑BIRC6 expression levels in BC cell lines were determined using reverse transcription‑quantitative PCR. Following circ‑BIRC6 knockdown, cell proliferation, invasion and migration were detected using Cell Counting Kit‑8, colony formation, Transwell and wound healing assays, respectively. Western blotting was also conducted to evaluate the expression levels of X‑box binding protein 1 (XBP1) and epithelial‑mesenchymal transition (EMT)‑associated proteins. In addition, rescue experiments were performed using by transfecting a miR‑495‑3p inhibitor into T24 cells following circ‑BIRC6 knockdown. The interactions between circ‑BIRC6, miR‑495‑3p and XBP1 was verified using dual luciferase reporter assays. Moreover, T24 cells with circ‑BIRC6 knockdown and miR‑495‑3p inhibitor transfection were used for the tumor‑bearing experiment. Tumor growth was observed and Ki‑67 expression was determined using immunohistochemistry. The results demonstrated that circ‑BIRC6 expression was upregulated in BC cell lines. Moreover, circ‑BIRC6 knockdown notably attenuated the proliferation, invasion, migration and EMT of BC cells, which was blocked by the miR‑495‑3p inhibitor. It was also identified that circ‑BIRC6 sponged miR‑495‑3p to regulate XBP1 expression. In addition, results from the xenograft experiments indicated that the knockdown of circ‑BIRC6 and miR‑495‑3p expression significantly inhibited tumor growth. It was also found that the expression levels of XBP1, Ki‑67 and EMT‑associated proteins in tumor tissues of the co‑transfection group were markedly restored compared with the circ‑BIRC6 knockdown group. In conclusion, these findings demonstrated that circ‑BIRC6 knockdown suppressed BC tumorigenesis and progression via regulation of the miR‑495‑3p/XBP1 signaling axis, offering a promising therapeutic target for the treatment of BC.

Androgen Receptor-Mediated Nuclear Transport of NRDP1 in Prostate Cancer Cells Is Associated with Worse Patient Outcomes

Simple Summary

NRDP1 is an E3 ubiquitin ligase that has been shown by our group and others to target ErbB3 for proteasomal degradation in prostate and breast cancer cells and thereby decrease the likelihood cancer progression. Our group has found that NRDP1 can be located in the nucleus as well as the cytoplasm of prostate cancer (CaP) cells, which is unexpected as NRDP1 lacks a nuclear localization signal. Here we elucidate the mechanism by which nuclear translocation of NRDP1 can occur and demonstrate that nuclear NRDP1 retains its ubiquitin ligase activity. Our patient data and cell line studies indicate that increased levels of nuclear NRDP1 contributes CaP progression, thereby underscoring the clinical relevance of our findings and supporting continued investigation and elucidation of the specific role(s) played by NRDP1 in the nucleus of CaP cells.

Abstract

To our knowledge, our group is the first to demonstrate that NRDP1 is located in the nucleus as well as the cytoplasm of CaP cells. Subcellular fractionation, immunohistochemistry, and immunofluorescence analysis combined with confocal microscopy were used to validate this finding. Subcellular fractionation followed by western blot analysis revealed a strong association between AR and NRDP1 localization when AR expression and/or cellular localization was manipulated via treatment with R1881, AR-specific siRNA, or enzalutamide. Transfection of LNCaP with various NRDP1 and AR constructs followed by immunoprecipitation confirmed binding of NRDP1 to AR is possible and determined that binding requires the hinge region of AR. Co-transfection with NRDP1 constructs and HA-ubiquitin followed by subcellular fractionation confirmed that nuclear NRDP1 retains its ubiquitin ligase activity. We also show that increased nuclear NRDP1 is associated with PSA recurrence in CaP patients (n = 162, odds ratio; 1.238, p = 0.007) and that higher levels of nuclear NRDP1 are found in castration resistant cell lines (CWR22Rv1 and PC3) compared to androgen sensitive cell lines (LNCaP and MDA-PCa-3B). The combined data indicate that NRDP1 plays a role in mediating CaP progression and supports further investigation of both the mechanism by which nuclear transport occurs and the identification of specific nuclear targets.

The Molecular Basis of Ubiquitin-Conjugating Enzymes (E2s) as a Potential Target for Cancer Therapy

Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

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.

Inhibitory Effect of Hydroxysafflor Yellow B on the Proliferation of Human Breast Cancer MCF-7 Cells

BACKGROUND

A recent patent has been issued for hydroxysafflor yellow A (HSYA) as a drug to prevent blood circulation disorders. Hydroxysafflor yellow B (HSYB), an isomer of HSYA with antioxidative effects, has been isolated from the florets of Carthamus tinctorius. The effects of HSYB on the proliferation of cancer cells and its mechanism of action have not been investigated.

OBJECTIVE

The aims of this study were to investigate the anti-cancer effects and the molecular mechanism of HSYB for breast cancer MCF-7 cells.

METHODS

MTT assays and colony formation assays were used to assess the survival and proliferation of MCF-7 cells, respectively. Hoechst 33258 and flow cytometry were used to measure cell apoptosis and flow cytometry to determine effects on the cell cycle. Western blots were used to measure protein levels.

RESULTS

Treatment with HSYB reduced survival and proliferation of human breast cancer MCF-7 cells in a dose-dependent manner. Furthermore, HSYB arrested the MCF-7 cell cycle at the S phase and downregulated cyclin D1, cyclin E, and CDK2. Compared with a control group, HSYB suppressed the protein levels of p-PI3K, PI3K, AKT, and p-AKT in MCF-7 cells. In addition, HSYB decreased the levels of Bcl- 2, increased the levels of Bax, cleaved caspase-3 and caspase-9, and subsequently induced MCF-7 cell apoptosis.

CONCLUSION

These data demonstrate that HSYB arrests the MCF-7 cell cycle at the S phase and induces cell apoptosis. Patent US20170246228 indicates that HSYB can be potentially used for the prevention and treatment of human breast cancer.

Integrated analysis of miRNA landscape and cellular networking pathways in stage-specific prostate cancer

Dysregulation of miRNAs has been demonstrated in several human malignancies including prostate cancer. Due to tissue limitation and variable disease progression, stage-specific miRNAs changes in prostate cancer is unknown. Using chip-based microarray, we investigated global miRNA expression in human prostate cancer LNCaP, PC3, DU145 and 22Rv1 cells representing early-stage, advanced-stage and castration resistant prostate cancer in comparison with normal prostate epithelial cells. A total of 292 miRNAs were differentially expressed with 125 upregulated and 167 downregulated. These miRNAs were involved in pathways including drug resistance drug-efflux, adipogenesis, epithelial-to-mesenchymal transition, bone metamorphosis, and Th1/Th2 signaling. Regulation of miRNAs were interlinked with upstream regulators such as Argonaut 2 (AGO2), Double-Stranded RNA-Specific Endoribonuclease (DICER1), Sjogren syndrome antigen B (SSB), neurofibromatosis 2 (NF2), and peroxisome proliferator activated receptor alpha (PPARA), activated during stage-specific disease progression. Candidate target genes and pathways dysregulated in stage-specific prostate cancer were identified using CS-miRTar database and confirmed in clinical specimens. Integrative network analysis suggested some genes targeted by miRNAs include miR-17, let7g, miR-146, miR-204, miR-205, miR-221, miR-301 and miR-520 having a major effect on their dysregulation in prostate cancer. MiRNA-microarray analysis further identified miR-130a, miR-181, miR-328, miR146 and miR-200 as a panel of novel miRNAs associated with drug resistance drug-efflux and epithelial-to-mesenchymal transition in prostate cancer. Our findings provide evidence on miRNA dysregulation and its association with key functional components in stage-specific prostate cancer.

MicroRNA‑330‑5p inhibits osteosarcoma cell growth and invasion by targeting the proto‑oncogene survivin

Increasing evidence has suggested the crucial role of the dysregulation of microRNAs (miRNAs) in osteosarcoma (OS) progression. MicroRNA (miR)-330-5p has been reported to exert tumor suppressive effects in various types of human cancer. However, the role of miR-330-5p in the development of OS and the underlying mechanism remain to be clarified. In the present study, miR-330-5p expression was found to be significantly decreased in OS tissues and cell lines. In addition, low miR-330-5p expression was highly correlated with the overall survival and clinical stage of OS. Overexpression of miR-330-5p inhibited the viability, migration and invasion, and promoted the apoptosis of OS cells, as well as induced cell cycle arrest at the G₂/M phase. Subsequently, the proto-oncogene survivin was identified as a functional target of miR-330-5p, and this was validated using a luciferase reporter assay. It was also demonstrated that survivin expression was markedly increased in OS tissues, and that it was negatively correlated with the expression of miR-330-5p. Furthermore, overexpression of survivin significantly abrogated the tumor-suppressive effect induced by miR-330-5p on OS cells. In conclusion, these results revealed that the miR-330-5p/survivin axis has a significant tumor-suppressive effect on OS, and may serve as a diagnostic and therapeutic target for the treatment of OS.

Linc01194 acts as an oncogene in colorectal carcinoma and is associated with poor survival outcome

Background

The incidence of colorectal cancer ranks among the top three malignant tumors, attributing to more than 50,000 deaths in the United States every year. Survival rate is directly correlated with TNM stage at diagnosis, and identifying the molecules involved in the cancer development process will provide directions to better investigate the mechanisms of colorectal cancer.

Materials and methods

Bioinformatics analysis of differentially expressed long noncoding RNAs (lncRNAs), survival analysis, cell proliferation assay, migration assay, and Western blot analysis were performed.

Results

Fifty-one lncRNAs were identified between the early stage and late-stage groups. In the survival analysis, we found that Linc01194 is correlated with poor survival of colon cancer patients. In addition, by suppressing the expression of Linc01194 in colon cancer cell lines, cell proliferation and migration were inhibited. Western blot showed that N-cadherin and vimentin were downregulated, whereas E-cadherin was upregulated indicating that the process of epithelial–mesenchymal transition (EMT) was restrained.

Conclusion

Linc01194 promotes the proliferation and migration ability of colon cancer cells by activating EMT. It acts as an oncogene in colorectal carcinoma and is associated with worse survival outcome.

Positive feedback loop between mitochondrial fission and Notch signaling promotes survivin-mediated survival of TNBC cells

Mitochondrial morphology is remodeled by continuous dynamic cycles of fission and fusion. Emerging data have shown that the disturbance of balance between mitochondrial fission and fusion is involved in the progression of several types of neoplasms. However, the status of mitochondrial dynamics and its potential biological roles in breast cancer (BC), particularly in triple negative BC (TNBC) are not fully clear. Here, we reported that the mitochondrial fission was significantly increased in BC tissues, especially in the TNBC tissues, when compared with that in the corresponding peritumor tissues. Meanwhile, our data showed that Drp1 was upregulated, while Mfn1 was downregulated in TNBC. Moreover, elevated mitochondrial fission was associated with poorer prognosis in TNBC patients. Mitochondrial fission promoted the survival of TNBC cells both in vitro and in vivo. Furthermore, we identified a positive feedback loop between mitochondrial fission and Notch signaling pathway in TNBC cells, as proved by the experimental evidence that the activation of Notch signaling enhanced Drp1-mediated mitochondrial fission and Drp1-mediated mitochondrial fission in turn promoted the activation of Notch signaling, which ultimately promoted the cell survival of TNBC via increasing survivin expression level. Inhibition of either Notch1 or Drp1 significantly impaired the activation of the other, leading to the suppression of TNBC cell survival and proliferation. Collectively, our data reveal a novel mechanism that the positive feedback loop between mitochondrial fission and Notch signaling promotes the survival, proliferation and apoptotic resistance of TNBC cells via increasing survivin expression and thus favors cancer progression.

Overcoming chemotherapy drug resistance by targeting inhibitors of apoptosis proteins (IAPs)

Inhibitors of apoptosis (IAPs) are a family of proteins that play a significant role in the control of programmed cell death (PCD). PCD is essential to maintain healthy cell turnover within tissue but also to fight disease or infection. Uninhibited, IAPs can suppress apoptosis and promote cell cycle progression. Therefore, it is unsurprising that cancer cells demonstrate significantly elevated expression levels of IAPs, resulting in improved cell survival, enhanced tumor growth and subsequent metastasis. Therapies to target IAPs in cancer has garnered substantial scientific interest and as resistance to anti-cancer agents becomes more prevalent, targeting IAPs has become an increasingly attractive strategy to re-sensitize cancer cells to chemotherapies, antibody based-therapies and TRAIL therapy. Antagonism strategies to modulate the actions of XIAP, cIAP1/2 and survivin are the central focus of current research and this review highlights advances within this field with particular emphasis upon the development and specificity of second mitochondria-derived activator of caspase (SMAC) mimetics (synthetic analogs of endogenously expressed inhibitors of IAPs SMAC/DIABLO). While we highlight the potential of SMAC mimetics as effective single agent or combinatory therapies to treat cancer we also discuss the likely clinical implications of resistance to SMAC mimetic therapy, occasionally observed in cancer cell lines.

Fluoxetine induces autophagic cell death via eEF2K-AMPK-mTOR-ULK complex axis in triple negative breast cancer

OBJECTIVES

Triple negative breast cancer (TNBC) is a complex and intrinsically aggressive tumour with poor prognosis, and the discovery of targeted small-molecule drugs for TNBC treatment still remains in its infancy. In this study, we aimed to discover a small-molecule agent for TNBC treatment and illuminate its potential mechanisms.

MATERIALS AND METHODS

Cell viability was detected by using methylthiazoltetrazolium (MTT) assay. Electron microscopy, GFP-LC3 transfection, monodansylcadaverine staining and apoptosis assay were performed to determine Fluoxetine-induced autophagy and apoptosis. Western blotting and siRNA transfection were carried out to investigate the mechanisms of Fluoxetine-induced autophagy. iTRAQ-based proteomics analysis was used to explore the underlying mechanisms.

RESULTS

We have demonstrated that Fluoxetine had remarkable anti-proliferative activities and induced autophagic cell death in MDA-MB-231 and MDA-MB-436 cells. The mechanism for Fluoxetine-induced autophagic cell death was associated with inhibition of eEF2K and activation of AMPK-mTOR-ULK complex axis. Further iTRAQ-based proteomics and network analyses revealed that Fluoxetine-induced mechanism was involved in BIRC6, BNIP1, SNAP29 and Bif-1.

CONCLUSIONS

These results demonstrate that Fluoxetine induces apoptosis and autophagic cell death in TNBC, which will hold a promise for the future TNBC therapy.

BIRC6 mediates imatinib resistance independently of Mcl-1

Baculoviral IAP repeat containing 6 (BIRC6) is a member of the inhibitors of apoptosis proteins (IAPs), a family of functionally and structurally related proteins that inhibit apoptosis. BIRC6 has been implicated in drug resistance in several different human cancers, however mechanisms regulating BIRC6 have not been extensively explored. Our phosphoproteomic analysis of an imatinib-resistant chronic myelogenous leukemia (CML) cell line (MYL-R) identified increased amounts of a BIRC6 peptide phosphorylated at S480, S482, and S486 compared to imatinib-sensitive CML cells (MYL). Thus we investigated the role of BIRC6 in mediating imatinib resistance and compared it to the well-characterized anti-apoptotic protein, Mcl-1. Both BIRC6 and Mcl-1 were elevated in MYL-R compared to MYL cells. Lentiviral shRNA knockdown of BIRC6 in MYL-R cells increased imatinib-stimulated caspase activation and resulted in a ~20-25-fold increase in imatinib sensitivity, without affecting Mcl-1. Treating MYL-R cells with CDK9 inhibitors decreased BIRC6 mRNA, but not BIRC6 protein levels. By contrast, while CDK9 inhibitors reduced Mcl-1 mRNA and protein, they did not affect imatinib sensitivity. Since the Src family kinase Lyn is highly expressed and active in MYL-R cells, we tested the effects of Lyn inhibition on BIRC6 and Mcl-1. RNAi-mediated knockdown or inhibition of Lyn (dasatinib/ponatinib) reduced BIRC6 protein stability and increased caspase activation. Inhibition of Lyn also increased formation of an N-terminal BIRC6 fragment in parallel with reduced amount of the BIRC6 phosphopeptide, suggesting that Lyn may regulate BIRC6 phosphorylation and stability. In summary, our data show that BIRC6 stability is dependent on Lyn, and that BIRC6 mediates imatinib sensitivity independently of Mcl-1 or CDK9. Hence, BIRC6 may be a novel target for the treatment of drug-resistant CML where Mcl-1 or CDK9 inhibitors have failed.

Inducing death in tumor cells: roles of the inhibitor of apoptosis proteins

The heterogeneous group of diseases collectively termed cancer results not just from aberrant cellular proliferation but also from a lack of accompanying homeostatic cell death. Indeed, cancer cells regularly acquire resistance to programmed cell death, or apoptosis, which not only supports cancer progression but also leads to resistance to therapeutic agents. Thus, various approaches have been undertaken in order to induce apoptosis in tumor cells for therapeutic purposes. Here, we will focus our discussion on agents that directly affect the apoptotic machinery itself rather than on drugs that induce apoptosis in tumor cells indirectly, such as by DNA damage or kinase dependency inhibition. As the roles of the Bcl-2 family have been extensively studied and reviewed recently, we will focus in this review specifically on the inhibitor of apoptosis protein (IAP) family. IAPs are a disparate group of proteins that all contain a baculovirus IAP repeat domain, which is important for the inhibition of apoptosis in some, but not all, family members. We describe each of the family members with respect to their structural and functional similarities and differences and their respective roles in cancer. Finally, we also review the current state of IAPs as targets for anti-cancer therapeutics and discuss the current clinical state of IAP antagonists.

BIRC6 Targeting as Potential Therapy for Advanced, Enzalutamide-Resistant Prostate Cancer

Purpose: Enzalutamide resistance has emerged as a major problem in the management of castration-resistant prostate cancer (CRPC). Research on therapy resistance of CRPCs has primarily focused on the androgen receptor pathway. In contrast, there is limited information on antiapoptotic mechanisms that may facilitate the treatment resistance. The inhibitor of apoptosis proteins (IAP) family is well recognized for its role in promoting treatment resistance of cancers by inhibiting drug-induced apoptosis. Here, we examined whether BIRC6, an IAP family member, has a role in enzalutamide resistance of CRPCs and could provide a therapeutic target for enzalutamide-resistant CRPC.Experimental Design: Use of enzalutamide-resistant CRPC models: (i) the transplantable, first high-fidelity LTL-313BR patient-derived enzalutamide-resistant CRPC tissue xenograft line showing primary enzalutamide resistance, (ii) MR42D and MR49F CRPC cells/xenografts showing acquired enzalutamide resistance. Specific BIRC6 downregulation in these models was produced using a BIRC6-targeting antisense oligonucleotide (ASO-6w2). Gene expression was determined by qRT-PCR and gene expression profiling. Molecular pathways associated with growth inhibition were assessed via gene enrichment analysis.Results: Of eight IAPs examined, BIRC6 was the only one showing elevated expression in both enzalutamide-resistant CRPC models. Treatment with ASO-6w2 markedly suppressed growth of LTL-313BR xenografts and increased tumor apoptosis without inducing major host toxicity. Pathway enrichment analysis indicated that GPCR and matrisome signaling were the most significantly altered pathways. Furthermore, ASO-6w2 inhibited expression of prosurvival genes that were upregulated in the LTL-313BR line.Conclusions:BIRC6 targeting inhibited the growth of enzalutamide-resistant CRPC models and may represent a new option for clinical treatment of advanced, enzalutamide-resistant prostate cancer. Clin Cancer Res; 23(6); 1542-51. ©2016 AACR.

MiR-34a and miR-203 Inhibit Survivin Expression to Control Cell Proliferation and Survival in Human Osteosarcoma Cells

Elevated expression of survivin is observed in a number of cancer types, including human osteosarcoma. Few studies have demonstrated that survivin expression levels can be considered an independent predictor of survival for human osteosarcoma patients. However, the underlying molecular mechanisms of survivin in the process of human osteosarcoma carcinogenesis remain unclear. In the current study, we evaluated the biological effects of survivin knockdown on osteosarcoma cell proliferation, colony formation rate, and sensitivity to the chemotherapeutic agent cisplatin. We found that two different osteosarcoma cell lines, U2OS and Saos-2, have relatively higher expression levels of survivin, and specific knockdown of survivin resulted in a number of effects, such as inhibition of cell proliferation, decreased colony formation rate, cell cycle arrest at G2/M phase, induction of apoptosis, and increased sensitivity to cisplatin. In addition, we identified two microRNAs, miR-34a and miR-203, that are aberrantly expressed in human osteosarcoma cells and specifically target survivin by inhibiting its expression, therefore repressing osteosarcoma cell maintenance and proliferation.

Downregulation of miR-129-2 by promoter hypermethylation regulates breast cancer cell proliferation and apoptosis

Aberrant expression of the miR-129 family has been found in several types of cancer, yet its expression and potential biologic role in breast cancer remain largely unknown. In the present study, we found that miR-129-2 was consistently downregulated in the breast cancer specimens and cell lines. Overexpression of miR-129-2-3p markedly suppressed breast cancer cell proliferation and induced its apoptosis. In addition, a luciferase reporter assay revealed that miR-129-2-3p suppressed BCL2L2 expression. Furthermore, BCL2L2 was able to reverse miR-129-2-3p-mediated cell apoptosis, indicating that BCL2L2 plays a crucial role in mediating the tumor-suppressive role of miR-129-2-3p. Moreover, bisulfite DNA sequencing PCR (BSP) analysis identified that promoter hypermethylation was responsible for the downregulation of miR-129-2 in breast cancer. Collectively, our findings indicate that miR-129-2 is downregulated in breast cancer cells by promoter hypermethylation. Moreover, downregulation of miR-129-2 results in BCL2L2 overexpression and disease progression in breast cancer patients.

Suppressive Effect of Constructed shRNAs against Apollon Induces Apoptosis and Growth Inhibition in the HeLa Cell Line

Background:

Cervical cancer is the second most common female cancer worldwide. Inhibitors of apoptosis proteins (IAPs) block apoptosis; therefore, therapeutic strategies targeting IAPs have attracted the interest of researchers in recent years. Apollon, a member of IAPs, inhibits apoptosis and cell death. RNA interference is a pathway in which small interfering RNA (siRNA) or shRNA (short hairpin RNA) inactivates the expression of target genes. The purpose of this study was to determine the effect of constructed shRNAs on apoptosis and growth inhibition through the suppression of apollon mRNA in HeLa cell line.

Methods:

Three shRNAs with binding ability to three different target sites of the first region of apollon gene were designed and cloned in pRNAin-H1.2/Neo vector. shRNA plasmids were then transfected in HeLa cells using electroporation. Down-regulation effects of apollon and the viability of HeLa cells were analyzed by RT-PCR, lactate dehydrogenase assay, and MTT assay, respectively. Also, the induction and morphological markers of apoptosis were evaluated by caspase assay and immunocytochemistry method.

Results:

The expression of shRNA in HeLa cells caused a significant decrease in the level of apollon mRNA1. In addition, shRNA1 effectively increased the mRNA level of Smac (as the antagonist of apollon), reduced the viability of HeLa cells and exhibited immunocytochemical apoptotic markers in this cell line.

Conclusion:

Apollon gene silencing can induce apoptosis and growth impairment in HeLa cells. In this regard, apollon can be considered a candidate therapeutic target in HeLa cells as a positive human papillomavirus cancer cell line.

Survivin and Tumorigenesis: Molecular Mechanisms and Therapeutic Strategies

Survivin is the smallest member of the inhibitor of apoptosis protein family, which has key roles in regulating cell division and inhibiting apoptosis by blocking caspase activation. Survivin is highly expressed in most human cancers, such as lung, pancreatic and breast cancers, relative to normal tissues. Aberrant survivin expression is associated with tumor cell proliferation, progression, angiogenesis, therapeutic resistance, and poor prognosis. Studies on the underlying molecular mechanisms indicate that survivin is involved in the regulation of cytokinesis and cell cycle progression, as well as participates in a variety of signaling pathways such as the p53, Wnt, hypoxia, transforming growth factor, and Notch signaling pathways. In this review, recent progress in understanding the molecular basis of survivin is discussed. Therapeutic strategies targeting survivin in preclinical studies are also briefly summarized.

Peroxisome Proliferator-Activated Receptor β/δ Alleviates Early Brain Injury After Subarachnoid Hemorrhage in Rats

BACKGROUND AND PURPOSE

Early brain injury is proposed to be the primary cause of the poor outcome after subarachnoid hemorrhage (SAH), which is closely related to the neural apoptosis. To date, the relationship between peroxisome proliferator-activated receptor β/δ (PPARβ/δ) and nuclear factor-κB/matrix metalloproteinase-9 (NF-κB/MMP-9) pathway, both of which are closely related to apoptotic effects, has been poorly studied in SAH. The present study was undertaken to evaluate the effects of PPARβ/δ on early brain injury and NF-κB/MMP-9 pathway after SAH in rats.

METHODS

SAH model was established by injecting nonheparinized autologous arterial blood into the prechiasmatic cistern in male Sprague-Dawley rats. Adenoviruses or small interfering RNAs were injected into the right lateral cerebral ventricle to, respectively, up- or downregulate PPARβ/δ expression before SAH. All animals were assessed with a neurological score and then killed at 24 hours after SAH surgery. The indexes of brain water content, blood-brain barrier permeability, and apoptosis were used to detect brain injury. The expression of PPARβ/δ, NF-κB, and MMP-9 were measured by immunohistochemistry, gelatin zymography, and Western Blot methods, respectively. In addition, GW0742, a specific agonist of PPARβ/δ, was used to treat SAH in rats, the effects of which were evaluated by neurological scoring and Evans blue extravasation.

RESULTS

Overexpression of PPARβ/δ by adenoviruses treatment significantly ameliorated brain injury with improvement in neurological deficits, brain edema, blood-brain barrier impairment, and neural cell apoptosis at 24 hours after SAH in rats, whereas downregulation of PPARβ/δ by small interfering RNAs administration resulted in the reverse effects of the above. The expression levels of NF-κB and MMP-9 were markedly downregulated when PPARβ/δ increased after PPARβ/δ adenovirus transfection and upregulated when PPARβ/δ decreased by PPARβ/δ small interfering RNAs treatment. Moreover, GW0742 improved neurological deficits and reduced Evans blue extravasation at 24 hours after SAH.

CONCLUSIONS

PPARβ/δ's overexpression may attenuate early brain injury after rats' SAH administration, which reduces neural apoptosis possibly through blocking NF-κB/MMP-9 pathway.

Novel roles of androgen receptor, epidermal growth factor receptor, TP53, regulatory RNAs, NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, and matrix metalloproteinase-9 in prostate cancer and prostate cancer stem cells

Approximately one in six men will be diagnosed with some form of prostate cancer in their lifetime. Over 250,000 men worldwide die annually due to complications from prostate cancer. While advancements in prostate cancer screening and therapies have helped in lowering this statistic, better tests and more effective therapies are still needed. This review will summarize the novel roles of the androgen receptor (AR), epidermal growth factor receptor (EGFR), the EGFRvIII variant, TP53, long-non-coding RNAs (lncRNAs), microRNAs (miRs), NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, (NGAL), matrix metalloproteinase-9 (MMP-9), the tumor microenvironment and cancer stem cells (CSC) have on the diagnosis, development and treatment of prostate cancer.

Dichotomy in the Epigenetic Mark Lysine Acetylation is Critical for the Proliferation of Prostate Cancer Cells

The dynamics of lysine acetylation serve as a major epigenetic mark, which regulates cellular response to inflammation, DNA damage and hormonal changes. Microarray assays reveal changes in gene expression, but cannot predict regulation of a protein function by epigenetic modifications. The present study employs computational tools to inclusively analyze microarray data to understand the potential role of acetylation during development of androgen-independent PCa. The data revealed that the androgen receptor interacts with 333 proteins, out of which at least 92 proteins were acetylated. Notably, the number of cellular proteins undergoing acetylation in the androgen-dependent PCa was more as compared to the androgen-independent PCa. Specifically, the 32 lysine-acetylated proteins in the cellular models of androgen-dependent PCa were mainly involved in regulating stability as well as pre- and post-processing of mRNA. Collectively, the data demonstrate that protein lysine acetylation plays a crucial role during the transition of androgen-dependent to -independent PCa, which importantly, could also serve as a functional axis to unravel new therapeutic targets.

Knockdown of the Inhibitor of Apoptosis BRUCE Sensitizes Resistant Breast Cancer Cells to Chemotherapeutic Agents

Background and objectives

Management of patients with breast cancer often fails because of inherent or acquired resistance to chemotherapy. BRUCE (BIR repeat containing ubiquitin-conjugating enzyme) is a member of the inhibitor of apoptosis protein (IAP) family. It has various cellular functions including suppression of apoptosis and promotion of cytokinesis. Furthermore, it pays a critical role in promotion of DNA damage repair and preservation of genome stability, a new function recently reported by our group. Although BRUCE is expressed in breast cancer cell lines, its expression in human primary breast tumors and its contribution to chemoresistance in breast cancers has not been explored. Chemotherapeutic drugs are used in the treatment of breast cancer patients. However, they are not effective to all patients and patients often develop resistance. Consequently we explored if BRUCE protein level, as judged by immunohistochemistry (IHC), is higher in primary breast tumors than normal breast tissue. We also examined if depletion of BRUCE, using a lentiviral shRNA approach, enhances cell sensitivity to multiple chemotherapeutic agents, including cisplatin, an agent that induces DNA damage by generating DNA cross-links, and taxol, a microtubule stabilizer and mitotic inhibitor. The reason for including these two chemotherapeutic agents in this study is that they hit two essential cellular processes of DNA repair and cytokinesis in which BRUCE plays critical roles.

Results and methods

IHC analysis of BRUCE revealed significantly higher levels of BRUCE in primary breast tumors than normal breast tissue. Knockdown of BRUCE protein expression by lentiviral shRNA resulted in increased sensitivity to cisplatin in the resistant breast cancer MDB-MD-231 cell line. Moreover, depletion of BRUCE in this cell line achieved a more profound level of cell killing when coupled to low doses of cisplatin and taxol combined, rather than either drug used alone.

Conclusions

Our data suggest that elevated protein levels of BRUCE in breast tumors may contribute to chemoresistance in breast cancer patients. In support of this suggestion, our data demonstrate that a reduction in BRUCE expression in breast cancer cell lines increases the toxicity of several chemotherapeutic agents. In all likelihood, the contribution of increased BRUCE levels to chemoresistance are likely due to its roles in suppression of apoptosis, promotion of cytokinesis and facilitation of DNA damage repair. These observations suggest that therapeutic suppression of BRUCE could improve chemosensitivity in chemo-resistant breast cancer patients. Therefore, future development of effective inhibitors of BRUCE could benefit patients with high BRUCE expression and chemoresistance.