AML sensitivity to YM155 is modulated through AKT and Mcl-1

SIRT6 suppresses colon cancer growth by inducing apoptosis and autophagy through transcriptionally down-regulating Survivin

SIRT6, an evolutionarily conserved histone deacetylase, has been identified as a novel direct downstream target of Akt/FoxO3a and a tumor suppressor in colon cancer in our previous research. Nevertheless, the precise mechanisms through which SIRT6 hinders tumor development remain unclear. To ascertain whether SIRT6 directly impacts Survivin transcription, a ChIP assay was conducted using an anti-SIRT6 antibody to isolate DNA. YM155 was synthesized to explore Survivin's role in mitochondrial apoptosis, autophagy and tumor progression. Our investigation into the regulation of Survivin involved real-time fluorescence imaging in living cells, real-time PCR, immunohistochemistry, flow cytometry, and xenograft mouse assays. In this current study, we delved into the role of SIRT6 in colon cancer and established that activated SIRT6 triggers mitochondrial apoptosis by reducing Survivin expression. Subsequent examinations revealed that SIRT6 directly binds to the Survivin promoter, impeding its transcription. Notably, direct inhibition of Survivin significantly impeded colon cancer proliferation by inducing mitochondrial apoptosis and autophagy both in vitro and in vivo. More interestingly, Survivin inhibition reactivated the Akt/FoxO3a pathway and elevated SIRT6 levels, establishing a positive feedback loop. Our results identify Survivin as a novel downstream transcriptional target of SIRT6 that fosters tumor growth and holds promise as a prospective target for colon cancer therapy.

Biological relevance of alternative splicing in hematologic malignancies

Alternative splicing (AS) is a strictly regulated process that generates multiple mRNA variants from a single gene, thus contributing to proteome diversity. Transcriptome-wide sequencing studies revealed networks of functionally coordinated splicing events, which produce isoforms with distinct or even opposing functions. To date, several mechanisms of AS are deregulated in leukemic cells, mainly due to mutations in splicing and/or epigenetic regulators and altered expression of splicing factors (SFs). In this review, we discuss aberrant splicing events induced by mutations affecting SFs (SF3B1, U2AF1, SRSR2, and ZRSR2), spliceosome components (PRPF8, LUC7L2, DDX41, and HNRNPH1), and epigenetic modulators (IDH1 and IDH2). Finally, we provide an extensive overview of the biological relevance of aberrant isoforms of genes involved in the regulation of apoptosis (e. g. BCL-X, MCL-1, FAS, and c-FLIP), activation of key cellular signaling pathways (CASP8, MAP3K7, and NOTCH2), and cell metabolism (PKM).

Epigenetic balance ensures mechanistic control of MLL amplification and rearrangement

MLL/KMT2A amplifications and translocations are prevalent in infant, adult, and therapy-induced leukemia. However, the molecular contributor(s) to these alterations are unclear. Here, we demonstrate that histone H3 lysine 9 mono- and di-methylation (H3K9me1/2) balance at the MLL/KMT2A locus regulates these amplifications and rearrangements. This balance is controlled by the crosstalk between lysine demethylase KDM3B and methyltransferase G9a/EHMT2. KDM3B depletion increases H3K9me1/2 levels and reduces CTCF occupancy at the MLL/KMT2A locus, in turn promoting amplification and rearrangements. Depleting CTCF is also sufficient to generate these focal alterations. Furthermore, the chemotherapy doxorubicin (Dox), which associates with therapy-induced leukemia and promotes MLL/KMT2A amplifications and rearrangements, suppresses KDM3B and CTCF protein levels. KDM3B and CTCF overexpression rescues Dox-induced MLL/KMT2A alterations. G9a inhibition in human cells or mice also suppresses MLL/KMT2A events accompanying Dox treatment. Therefore, MLL/KMT2A amplifications and rearrangements are controlled by epigenetic regulators that are tractable drug targets, which has clinical implications.

YM155 inhibits neuroblastoma growth through degradation of MYCN: A new role as a USP7 inhibitor

Amplification of the MYCN gene (MNA) is observed in approximately 25 to 35% of neuroblastoma patients, and is a well-recognized marker of tumor aggressiveness and poor outcome. Targeting MYCN is a novel therapy strategy to induce tumor regression. Here, we discovered that a BIRC5/Survivin inhibitor, YM155, specifically inhibits MNA neuroblastoma cell growth in vitro. We found that YM155 promotes MYCN degradation in MNA cells. Further, we found that YM155 inhibits USP7 deubiquitinase activity in vitro, using Ub-aminomethylcoumarin (Ub-AMC) as substrate. Results from in vivo studies further demonstrated that YM155 significantly inhibited the tumor growth in MNA neuroblastoma xenograft model. Our data support a novel mechanism of action of YM155 in inhibition of growth of cancer cells through inducing MYCN degradation by inibition of activity of deubiquitinase like USP7.

Comprehensive analysis for cellular senescence-related immunogenic characteristics and immunotherapy prediction of acute myeloid leukemia

In malignancies, cellular senescence is critical for carcinogenesis, development, and immunological regulation. Patients with acute myeloid leukemia (AML) have not investigated a reliable cellular senescence-associated profile and its significance in outcomes and therapeutic response. Cellular senescence-related genes were acquired from the CellAge database, while AML data were obtained from the GEO and TCGA databases. The TCGA-AML group served as a training set to construct a prognostic risk score signature, while the GSE71014 set was used as a testing set to validate the accuracy of the signature. Through exploring the expression profiles of cellular senescence-related genes (SRGs) in AML patients, we used Lasso and Cox regression analysis to establish the SRG-based signature (SRGS), which was validated as an independent prognostic predictor for AML patients via clinical correlation. Survival analysis showed that AML patients in the low-risk score group had a longer survival time. Tumor immune infiltration and functional enrichment analysis demonstrated that AML patients with low-risk scores had higher immune infiltration and active immune-related pathways. Meanwhile, drug sensitivity analysis and the TIDE algorithm showed that the low-risk score group was more susceptible to chemotherapy and immunotherapy. Cell line analysis in vitro further confirmed that the SRGs in the proposed signature played roles in the susceptibility to cytarabine and YM155. Our results indicated that SRGS, which regulates the immunological microenvironment, is a reliable predictor of the clinical outcome and immunotherapeutic response in AML.

Ym155 localizes to the mitochondria leading to mitochondria dysfunction and activation of AMPK that inhibits BMP signaling in lung cancer cells

The imidazolium compound Ym155 was first reported to be a survivin inhibitor. Ym155 potently induces cell death of many types of cancer cells in preclinical studies. However, in phase II clinical trials Ym155 failed to demonstrate a significant benefit. Studies have suggested that the cytotoxic effects of Ym155 in cancer cells are not mediated by the inhibition of survivin. Understanding the mechanism by which Ym155 induces cell death would provide important insight how to improve its efficacy as a cancer therapeutic. We demonstrate a novel mechanism by which Ym155 induces cell death by localizing to the mitochondria causing mitochondrial dysfunction. Our studies suggest that Ym155 binds mitochondrial DNA leading to a decrease in oxidative phosphorylation, decrease in TCA cycle intermediates, and an increase in mitochondrial permeability. Furthermore, we show that mitochondrial stress induced by Ym155 and other mitochondrial inhibitors activates AMP-activated kinase leading to the downregulation to bone morphogenetic protein (BMP) signaling. We provide first evidence that Ym155 initiates cell death by disrupting mitochondrial function.

Exploring solid-phase proximity ligation assay for survivin detection in urine

Urine-based biomarkers are a rational and promising approach for the detection of bladder cancer due to the proximity of urine to the location of the tumor site and the non-invasive nature of its sampling. A well-known and highly investigated biomarker for bladder cancer is survivin. For detection of very small amounts of urinary survivin protein a highly sensitive assay was developed. The assay is based on the immuno-PCR technology, more precisely a solid-phase proximity ligation assay (spPLA). The limit of detection for the survivin spPLA was 1.45 pg/mL, resulting in an improvement of the limit of detection by a factor of approximately 23 compared to the previously in-house developed survivin ELISA. A key step in development was the initial isolation of survivin by a molecular fishing rod based on magnetic beads. Interfering matrix compounds pose a special challenge for further analytical application, but can be overcome by this isolation step. The assay is designed to work with only 500 μL of voided urine. The survivin spPLA showed a sensitivity of 30% and specificity of 89% for bladder cancer detection in this study of 110 bladder cancer cases and 133 clinical controls. Moreover, the results demonstrated again that survivin is a useful complementary marker in combination with UBC^® Rapid by increasing the overall sensitivity to 70% with a specificity of 86%. Although the performance for detection of bladder cancer was rather low, the herein developed assay might serve as a new tool for survivin biomarker research in diverse human fluids, even if the biological matrix is complex or survivin is only present in small amounts.

Identification of U937JAK3-M511I Acute Myeloid Leukemia Cells as a Sensitive Model to JAK3 Inhibitor

Mutated JAK3 has been considered a promising target for cancer therapy. Activating mutations of JAK3 are observed in 3.9%-10% of acute myeloid leukemia (AML) patients, but it is unclear whether AML cells are sensitive to JAK3 inhibitors, and no disease-related human AML cell model has been reported. We have identified U937 as the first human AML cell line expressing the JAK3^M511I activated mutation and confirmed that JAK3 inhibitors sensitively suppress the proliferation of U937 AML cells.

Inhibition of Sp1-mediated survivin and MCL1 expression cooperates with SLC35F2 and myeloperoxidase to modulate YM155 cytotoxicity to human leukemia cells

Although YM155 is reported to suppress survivin (also known as BIRC5) expression in cancer cells, its cytotoxic mechanism in human acute myeloid leukemia (AML) cells has not been clearly resolved. In this study, we analyzed the mechanistic pathways that modulate the sensitivity of human AML U937 and HL-60 cells to YM155. YM155 induced apoptosis in AML cells, which was characterized by p38 MAPK phosphorylation and downregulation of survivin and MCL1 expression. Phosphorylated p38 MAPK causes autophagy-mediated Sp1 degradation, thereby inhibiting the transcription of survivin and MCL1. The reduction of survivin and MCL1 levels further facilitated Sp1 protein degradation through autophagy. The restoration of Sp1, survivin, or MCL1 expression protected U937 and HL-60 cells from YM155-mediated cytotoxicity. U937 and HL-60 cells were continuously exposed to hydroquinone (HQ) to generate U937/HQ and HL-60/HQ cells, which showed increased SLC35F2 expression. The increase in SLC35F2 expression led to an increase in the sensitivity of U937/HQ cells to YM155-mediated cytotoxicity, whereas no such effect was observed in HL-60/HQ cells. Of note, myeloperoxidase (MPO) activity in HL-60 and HL-60/HQ cells enhanced YM155 cytotoxicity in these cells, and the enforced expression of MPO also increased the sensitivity of U937 cells to YM155. Taken together, we conclude that p38 MAPK-modulated autophagy inhibits Sp1-mediated survivin and MCL1 expression, which, in turn, leads to the death of U937 and HL-60 cells following YM155 treatment. In addition, our data indicate that SLC35F2 increases the sensitivity of U937 cells to YM155-mediated cytotoxicity, whereas MPO enhances YM155 cytotoxicity in U937 and HL-60 cells.

Generation of reactive oxygen species is the primary mode of action and cause of survivin suppression by sepantronium bromide (YM155)

Survivin is a lucrative broad-spectrum drug target for different cancer types, including triple negative breast cancer (TNBC). Sepantronium bromide (YM155) is the first of its class of survivin suppressants and was found to be quite effective in pre-clinical models of TNBC. However, in clinical trials when given in combination with docetaxel, YM55 failed to provide any added advantage. To understand if the clinical outcome is due to YM155 being ineffective or due to an inappropriate choice of combination, we need to elucidate its true mode of action. Hence, to explain the unexpected and unexplained observations pertaining to YM155 biology and its mode of action, we developed isogenic pairs of YM155-sensitive and -resistant TNBC cell lines and characterized them in detail by various biochemical assays. We found that YM155 generates reactive oxygen species (ROS) in the mitochondria in addition to the previously discovered redox cycling pathway. Both survivin suppression and DNA damage are secondary effects resulting from the ROS which contribute to the drug's cytotoxic effects on TNBC cells. Indeed, adaptation to both these pathways was important in conferring YM155 resistance. Finally, we uncovered a unique connection between the ROS and control of survivin expression involving a ROS/AKT/FoxO/survivin axis in TNBC cells. Together, by deciphering the true mode of action of YM155, we present a possible explanation for its poor clinical efficacy when used in combination with docetaxel. The results and conclusions presented here provide the information needed to effectively use YM155 in combination therapy.

Splicing machinery genomics events in acute myeloid leukaemia (AML): in search for therapeutic targets, diagnostic and prognostic biomarkers

Acute myeloid leukemia (AML) is the most common form of acute leukaemia and has the highest mortality rate. Screening for mutations in patients with AML has shown that in many cases genes carrying mutations are involved in the alternate splicing of mRNA. These include members of the Serine Arginine (SR) family of splicing factors, as well as components of the spliceosome. Mutations in associated genes also affect the function of members of the heterogeneous nuclear ribonucleoproteins (hnRNPs). These mutations in splicing factors can lead to changes in the expression of different isoforms whose splicing is controlled by these splicing factors. These different isoforms may have completely different functions, for example, members of the BCl-2 family are alternately spliced to give rise to pro and anti-apoptotic members. Mutations in the splicing factors that control the splicing of these mRNAs can lead to changes in the expression level of these isoforms. In this review we will examine the mechanics of the regulation of the various splice isoforms and how this drives the development of tumors. This information is pertinent for drug discovery, and the splicing factors with the most promise for pharmacological control will be discussed.

YM155-Adapted Cancer Cell Lines Reveal Drug-Induced Heterogeneity and Enable the Identification of Biomarker Candidates for the Acquired Resistance Setting

Survivin is a drug target and its suppressant YM155 a drug candidate mainly investigated for high-risk neuroblastoma. Findings from one YM155-adapted subline of the neuroblastoma cell line UKF-NB-3 had suggested that increased ABCB1 (mediates YM155 efflux) levels, decreased SLC35F2 (mediates YM155 uptake) levels, decreased survivin levels, and TP53 mutations indicate YM155 resistance. Here, the investigation of 10 additional YM155-adapted UKF-NB-3 sublines only confirmed the roles of ABCB1 and SLC35F2. However, cellular ABCB1 and SLC35F2 levels did not indicate YM155 sensitivity in YM155-naïve cells, as indicated by drug response data derived from the Cancer Therapeutics Response Portal (CTRP) and the Genomics of Drug Sensitivity in Cancer (GDSC) databases. Moreover, the resistant sublines were characterized by a remarkable heterogeneity. Only seven sublines developed on-target resistance as indicated by resistance to RNAi-mediated survivin depletion. The sublines also varied in their response to other anti-cancer drugs. In conclusion, cancer cell populations of limited intrinsic heterogeneity can develop various resistance phenotypes in response to treatment. Therefore, individualized therapies will require monitoring of cancer cell evolution in response to treatment. Moreover, biomarkers can indicate resistance formation in the acquired resistance setting, even when they are not predictive in the intrinsic resistance setting.

Testing of the Survivin Suppressant YM155 in a Large Panel of Drug-Resistant Neuroblastoma Cell Lines

The survivin suppressant YM155 is a drug candidate for neuroblastoma. Here, we tested YM155 in 101 neuroblastoma cell lines (19 parental cell lines, 82 drug-adapted sublines). Seventy seven (77) cell lines displayed YM155 IC₅₀s in the range of clinical YM155 concentrations. ABCB1 was an important determinant of YM155 resistance. The activity of the ABCB1 inhibitor zosuquidar ranged from being similar to that of the structurally different ABCB1 inhibitor verapamil to being 65-fold higher. ABCB1 sequence variations may be responsible for this, suggesting that the design of variant-specific ABCB1 inhibitors may be possible. Further, we showed that ABCC1 confers YM155 resistance. Previously, p53 depletion had resulted in decreased YM155 sensitivity. However, TP53-mutant cells were not generally less sensitive to YM155 than TP53 wild-type cells in this study. Finally, YM155 cross-resistance profiles differed between cells adapted to drugs as similar as cisplatin and carboplatin. In conclusion, the large cell line panel was necessary to reveal an unanticipated complexity of the YM155 response in neuroblastoma cell lines with acquired drug resistance. Novel findings include that ABCC1 mediates YM155 resistance and that YM155 cross-resistance profiles differ between cell lines adapted to drugs as similar as cisplatin and carboplatin.

Emerging Effects of Sepantronium Bromide (YM155) on MOLT-4 Cell Line Apoptosis Induction and Expression of Critical Genes Involved in Apoptotic Pathways

Purpose: Sepantronium bromide (YM155) is a Survivin inhibitor which recently advanced as an anticancer agent in phase II clinical trials. Survivin belongs to IAP (inhibitor of apoptosis) gene family and is a pivotal target for treatment due to its overexpression and oncogenic function in many malignancies, including acute lymphoblastic leukemia (ALL). Although survivin is a specific target for YM155, recent reports have shown that it has many other crucial targets that regulate its anti-apoptotic effects. The aim of this study was to investigate whether YM155 could have an effect on cell death-inducing genes as well as inducing apoptosis in T-ALL MOLT4- cell line. Methods: We treated MOLT-4 cells with increasing concentrations of YM155 and then cell viability was determined using MTT (methyl thiazolyl tetrazolium) assay. Also, the rate of induction of apoptosis in MOLT-4 cells and the target genes expression levels were evaluated by Annexin V/PI and real-time PCR, respectively. Results: YM155 inhibited cell growth in MOLT-4 cells. This outcome is achieved by inducing apoptosis and a significant increase in the expression level of P53, MiR-9, caspase 3 and decreasing the mRNA expression levels of survivin, Sirtuin1(SIRT1), member of anti-apoptotic proteins family (Bcl-2), and epithelial-to-mesenchymal transition (EMT) initiating factors Snail1and Zeb2. Conclusion: The results showed that use of YM155 can be a potential drug therapy in T-ALL patients with promising effects on apoptosis induction.

Adaptation to chronic exposure to sepantronium bromide (YM155), a prototypical survivin suppressant is due to persistent DNA damage-response in breast cancer cells

Sepantronium bromide (YM155), originally developed against the anti-apoptotic protein survivin, performed exceptionally well in pre-clinical and phase I clinical trials. However, in phase II trials of several cancer types including breast cancer it performed poorly. Additionally, no definitive correlation between survivin level and response to therapy was found. In an attempt to understand the true reason of the late-stage failure of this promising drug, we developed YM155-resistant MCF-7 breast cancer cell line and characterized side-by-side with the drug-naïve parental cell line. Chronic YM155 treatment resulted in downregulation of survivin expression yet triggered cellular responses typical of adaptation to persistent DNA damage. Lowering endogenous antioxidant glutathione level and activity of cell cycle check-point kinase restored YM155 activity. Thus, contrary to its development as a survivin suppressant, YM155 primarily acts as a chemotherapeutic drug causing oxidative stress-mediated DNA damage. Adaptation to long-term exposure to YM155 can be prevented and/or overcome by interfering with detoxification and DNA damage-response pathways. Finally, proteins associated with DNA damage-response pathway will be more appropriate as predictive biomarkers of YM155 in breast tumor cells.

YM155 sensitizes TRAIL-induced apoptosis through cathepsin S-dependent down-regulation of Mcl-1 and NF-κB-mediated down-regulation of c-FLIP expression in human renal carcinoma Caki cells

YM155, a small-molecule survivin inhibitor, has been reported for its anti-cancer activity in various cancer cells. In this study, we investigated the effect of YM155 to enhance TRAIL-mediated apoptosis in human renal carcinoma cells. We found that YM155 alone had no effect on apoptosis, however, combined treatment with YM155 and TRAIL markedly induced apoptosis in human renal carcinoma cells (Caki, ACHN, and A498), breast cancer cells (MDA-MB231), and glioma cells (U251MG), but not normal cells [mesangial cell (MC) and human skin fibroblast (HSF)]. YM155 induced down-regulation of Mcl-1 expression at the post-translational levels, and the overexpression of Mcl-1 markedly inhibited YM155 plus TRAIL-induced apoptosis. Furthermore, YM155 induced down-regulation of c-FLIP mRNA expression through inhibition of NF-κB transcriptional activity. Ectopic expression of c-FLIP markedly blocked YM155-induced TRAIL sensitization. Taken together, our results suggested that YM155 sensitizes TRAIL-mediated apoptosis via down-regulation of Mcl-1 and c-FLIP expression in renal carcinoma Caki cells.

EGFR-mediated interleukin enhancer-binding factor 3 contributes to formation and survival of cancer stem-like tumorspheres as a therapeutic target against EGFR-positive non-small cell lung cancer

OBJECTIVES

YM155, an inhibitor of interleukin enhancer-binding factor 3 (ILF3), significantly suppresses cancer stemness property, implying that ILF3 contributes to cell survival of cancer stem cells. However, the molecular function of ILF3 inhibiting cancer stemness remains unclear. This study aimed to uncover the potential function of ILF3 involving in cell survival of epidermal growth factor receptor (EGFR)-positive lung stem-like cancer, and to investigate the potential role to improve the efficacy of anti-EGFR therapeutics.

MATERIALS AND METHODS

The association of EGFR and ILF3 in expression and regulations was first investigated in this study. Lung cancer A549 cells with deprivation of ILF3 were created by the gene-knockdown method and then RNAseq was applied to identify the putative genes regulated by ILF3. Meanwhile, HCC827- and A549-derived cancer stem-like cells were used to investigate the role of ILF3 in the formation of cancer stem-like tumorspheres.

RESULTS

We found that EGFR induced ILF3 expression, and YM155 reduced EGFR expression. The knockdown of ILF3 reduced not only EGFR expression in mRNA and protein levels, but also cell proliferation in vitro and in vivo, demonstrating that ILF3 may play an important role in contributing to cancer cell survival. Moreover, the knockdown and inhibition of ILF3 by shRNA and YM155, respectively, reduced the formation and survival of HCC827- and A549-derived tumorspheres through inhibiting ErbB3 (HER3) expression, and synergized the therapeutic efficacy of afatinib, a tyrosine kinase inhibitor, against EGFR-positive A549 lung cells.

CONCLUSION

This study demonstrated that ILF3 plays an oncogenic like role in maintaining the EGFR-mediated cellular pathway, and can be a therapeutic target to improve the therapeutic efficacy of afatinib. Our results suggested that YM155, an ILF3 inhibitor, has the potential for utilization in cancer therapy against EGFR-positive lung cancers.

YM155 exerts potent cytotoxic activity against quiescent (G0/G1) multiple myeloma and bortezomib resistant cells via inhibition of survivin and Mcl-1

YM155, a novel small molecule inhibitor of survivin, shows broad anticancer activity. Here, we have focused on the cytotoxic activity of YM155 against multiple myeloma (MM) including cytokinetically quiescent (G₀/G₁) cells and bortezomib resistant cells. YM155 strongly inhibited the growth of MM cell lines with the IC₅₀ value of below 10 nM. YM155 also showed potent anti-myeloma activity in mouse xenograft model. YM155 suppressed the expression of survivin and rapidly directed Mcl-1 protein for proteasome degradation. YM155 abrogated the interleukin-6-induced STAT3 phosphorylation, subsequently blocked Mcl-1 expression and induced apoptosis in MM cells. Triple-color flow cytometric analysis revealed that YM155 potently induced cell death of MM cells in G₀ phase. Quiescent primary MM cells were also sensitive to YM155. We established bortezomib-resistant MM cell line, U266/BTZR1, which possess a point mutation G322A. YM155 exhibited similar cytotoxic potency against U266/BTZR1 compared with parental cells. Interestingly, survivin expression was markedly elevated in U266/BTZR1 cells. Treatment with YM155 significantly down-regulated this increased survivin and Mcl-1 expression in U266/BTZR1 cells. In conclusion, our data indicate that YM155 exhibits potent cytotoxicity against quiescent (G₀/G₁) MM cells and bortezomib-resistant cells. These unique features of YM155 may be beneficial for the development of new therapeutic strategies to eliminate quiescent MM cells and overcome bortezomib resistance.

Survivin inhibitor YM155 induces mitochondrial dysfunction, autophagy, DNA damage and apoptosis in Bcl-xL silenced glioma cell lines

Because the anti-apoptotic protein Bcl-xL is overexpressed in glioma, one might expect that inhibiting or silencing this gene would promote tumor cell killing. However, our studies have shown that this approach has limited independent activity, but may tip the balance in favor of apoptosis induction in response to other therapeutic interventions. To address this issue, we performed a pharmacological screen using a panel of signaling inhibitors and chemotherapeutic agents in Bcl-xL silenced cells. Although limited apoptosis induction was observed with a series of inhibitors for receptor tyrosine kinases, PKC inhibitors, Src family members, JAK/STAT, histone deacetylase, the PI3K/Akt/mTOR pathway, MAP kinase, CDK, heat shock proteins, proteasomal processing, and various conventional chemotherapeutic agents, we observed a dramatic potentiation of apoptosis in Bcl-xL silenced cells with the survivin inhibitor, YM155. Treatment with YM155 increased the release of cytochrome c, smac/DIABLO and apoptosis inducing-factor, and promoted loss of mitochondrial membrane potential, activation of Bax, recruitment of LC3-II to the autophagosomes and apoptosis in Bcl-xL silenced cells. We also found an additional mechanism for the augmentation of apoptosis due to abrogation of DNA double-strand break repair mediated by Rad51 repression and enhanced accumulation of γH2AX. In summary, our observations may provide a new insight into the link between Bcl-xL and survivin inhibition for the development of novel therapies for glioma. © 2016 Wiley Periodicals, Inc.

Aberrant splicing and drug resistance in AML

The advent of next-generation sequencing technologies has unveiled a new window into the heterogeneity of acute myeloid leukemia (AML). In particular, recurrent mutations in spliceosome machinery and genome-wide aberrant splicing events have been recognized as a prominent component of this disease. This review will focus on how these factors influence drug resistance through altered splicing of tumor suppressor and oncogenes and dysregulation of the apoptotic signaling network. A better understanding of these factors in disease progression is necessary to design appropriate therapeutic strategies recognizing specific alternatively spliced or mutated oncogenic targets.