RNAi screening identifies TAK1 as a potential target for the enhanced efficacy of topoisomerase inhibitors

HDAC6-dependent deacetylation of TAK1 enhances sIL-6R release to promote macrophage M2 polarization in colon cancer

Histone deacetylase 6 (HDAC6), a member of the HDAC family, has been identified as a potential therapeutic target for tumor therapy, but the function and underlying mechanisms of HDAC6 in colon cancer are incompletely characterized. Our study showed that the infiltration ratio of M2 macrophages was increased in colon cancer tissues with high HDAC6 expression. Similarly, the knockdown of HDAC6 in colon cancer cells inhibited cocultured macrophage M2 polarization in vitro. Analysis of the antibody chip revealed that HDAC6 promoted sIL-6R release to enhance macrophage M2 polarization. Mass spectrometry and immunoprecipitation demonstrated that, mechanistically, HDAC6 interacted with transforming growth factor β-activated kinase 1 (TAK1), deacetylated TAK1 at T178 and promoted TAK1 phosphorylation. TAK1-p38 MAPK signaling could further increase the phosphorylation and activity of ADAM17, which is responsible for shedding of IL-6R. Notably, the expression of phosphorylated TAK1 was positively correlated with HDAC6 expression and macrophage M2 polarization in human colon cancer tissues. Our study revealed a new HDAC6-TAK1-ADAM17 regulatory axis that mediates sIL-6R release and macrophage polarization in colon cancer.

Non-enzymatic function of WRN RECQL helicase regulates removal of topoisomerase-I-DNA covalent complexes and triggers NF-κB signaling in cancer

Mutation in Werner (WRN) RECQL helicase is associated with premature aging syndrome (Werner syndrome, WS) and predisposition to multiple cancers. In patients with solid cancers, deficiency of the WRN RECQL helicase is paradoxically associated with enhanced overall survival in response to treatment with TOP1 inhibitors, which stabilize pathological TOP1‐DNA‐covalent‐complexes (TOP1cc) on the genome. However, the underlying mechanism of WRN in development of chemoresistance to TOP1 inhibitors is not yet explored. Our whole‐genome transcriptomic analysis for ~25,000 genes showed robust activation of NF‐κB‐dependent prosurvival genes in response to TOP1cc. CRISPR‐Cas9 knockout, shRNA silencing, and under‐expression of WRN confer high‐sensitivity of multiple cancers to TOP1 inhibitor. We demonstrated that WRN orchestrates TOP1cc repair through proteasome‐dependent and proteasome‐independent process, unleashing robust ssDNA generation. This in turn ensues signal transduction for CHK1 mediated NF‐κB‐activation through IκBα‐degradation and nuclear localization of p65 protein. Intriguingly, our site‐directed mutagenesis and rescue experiments revealed that neither RECQL‐helicase nor DNA‐exonuclease enzyme activity of WRN (WRN^E84A, WRN^K577M, and WRN^E84A‐K577M) were required for TOP1cc removal, ssDNA generation and signaling for NF‐κB activation. In correlation with patient data and above results, the TOP1 inhibitor‐based targeted therapy showed that WRN‐deficient melanoma tumors were highly sensitive to TOP1 inhibition in preclinical in vivo mouse model. Collectively, our findings identify hitherto unknown non‐enzymatic role of WRN RECQL helicase in pathological mechanisms underlying TOP1cc processing and subsequent NF‐κB‐activation, offering a potential targeted therapy for WRN‐deficient cancer patients.

Precision Oncology with Drugs Targeting the Replication Stress, ATR, and Schlafen 11

Precision medicine aims to implement strategies based on the molecular features of tumors and optimized drug delivery to improve cancer diagnosis and treatment. DNA replication is a logical approach because it can be targeted by a broad range of anticancer drugs that are both clinically approved and in development. These drugs increase deleterious replication stress (RepStress); however, how to selectively target and identify the tumors with specific molecular characteristics are unmet clinical needs. Here, we provide background information on the molecular processes of DNA replication and its checkpoints, and discuss how to target replication, checkpoint, and repair pathways with ATR inhibitors and exploit Schlafen 11 (SLFN11) as a predictive biomarker.

TAK1 Inhibitor Enhances the Therapeutic Treatment for Glioblastoma

Glioblastoma (GBM) is a brain tumor characterized by poor therapeutic response and overall survival. Despite relevant progress in conventional treatments represented by the clinical use of temozolomide (TMZ), a combination of approaches might be a possible future direction for treating GBM. Transforming growth factor-beta-activated kinase-1 (TAK1) is an essential component in genotoxic stresses-induced NF-κB-activation and mitogen-activated protein kinase (MAPK)-pathways; however, the role of TAK1 in GBM-chemoresistance remains unknown. This study aimed to verify, in GBM human cell lines, in an in vivo U87-xenograft model and in TMZ-treated-patients, the effect of TAK1 inhibition on the sensitivity of GBM cells to chemotherapy. In vitro model, using GBM cell lines, showed that 5Z-7-oxozeaenol augmented the cytotoxic effects of TMZ, blocking TMZ-induced NF-κB-activation, reducing DNA-damage and enhancing TMZ-induced apoptosis in GMB cell lines. We showed a reduction in tumor burden as well as tumor volume in the xenograft model following the treatment with 5Z-7-oxozaenol associated with TMZ. Our results showed a significant up-regulation in TAK1, p-p38, p-JNK and NF-κB in glioblastoma TMZ-treated-patients and denoted the role of 5Z-7-oxozeaenol in increasing the sensitivity of GBM cells to chemotherapy, proving to be an effective coadjuvant to current GBM chemotherapeutic regimens, suggesting a new option for therapeutic treatment of GBM.

Enhanced Protein Damage Clearance Induces Broad Drug Resistance in Multitype of Cancers Revealed by an Evolution Drug-Resistant Model and Genome-Wide siRNA Screening

Resistance to therapeutic drugs occurs in virtually all types of cancers, and the tolerance to one drug frequently becomes broad therapy resistance; however, the underlying mechanism remains elusive. Combining a whole whole-genome-wide RNA interference screening and an evolutionary drug pressure model with MDA-MB-231 cells, it is found that enhanced protein damage clearance and reduced mitochondrial respiratory activity are responsible for cisplatin resistance. Screening drug-resistant cancer cells and human patient-derived organoids for breast and colon cancers with many anticancer drugs indicates that activation of mitochondrion protein import surveillance system enhances proteasome activity and minimizes caspase activation, leading to broad drug resistance that can be overcome by co-treatment with a proteasome inhibitor, bortezomib. It is further demonstrated that cisplatin and bortezomib encapsulated into nanoparticle further enhance their therapeutic efficacy and alleviate side effects induced by drug combination treatment. These data demonstrate a feasibility for eliminating broad drug resistance by targeting its common mechanism to achieve effective therapy for multiple cancers.

Cancer biology functional genomics: From small RNAs to big dreams

The year 2021 marks the 20th anniversary of the first publications reporting the discovery of the gene silencing mechanism, RNA interference (RNAi) in mammalian cells. Along with the many studies that delineated the proteins and substrates that form the RNAi pathway, this finding changed our understanding of the posttranscriptional regulation of mammalian gene expression. Furthermore, the development of methods that exploited the RNAi pathway began the technological revolution that eventually enabled the interrogation of mammalian gene function-from a single gene to the whole genome-in only a few days. The needs of the cancer research community have driven much of this progress. In this perspective, we highlight milestones in the development and application of RNAi-based methods to study carcinogenesis. We discuss how RNAi-based functional genetic analysis of exemplar tumor suppressors and oncogenes furthered our understanding of cancer initiation and progression and explore how such studies formed the basis of genome-wide scale efforts to identify cancer or cancer-type specific vulnerabilities, including studies conducted in vivo. Furthermore, we examine how RNAi technologies have revealed new cancer-relevant molecular targets and the implications for cancer of the first RNAi-based drugs. Finally, we discuss the future of functional genetic analysis, highlighting the increasing availability of complementary approaches to analyze cancer gene function.

The MAP3K7-mTOR Axis Promotes the Proliferation and Malignancy of Hepatocellular Carcinoma Cells

Targeted therapy is currently limited for patients with hepatocellular carcinoma (HCC) due to the lack of suitable targets. Kinases play pivotal roles in many cellular biological processes, whereas dysregulation of kinases may lead to various diseases, particularly cancer. However, the role of kinases in HCC malignancy remains unclear. In this study, we employed a kinome small interfering RNA (siRNA) library, comprising 710 kinase-related genes, to screen whether any kinases were essential for cell proliferation in various HCC cell lines. Through a kinome siRNA library screening, we found that MAP3K7 was a crucial gene for HCC cell proliferation. Pharmacological or genetic ablation of MAP3K7 diminished the growth, migration, and invasion of HCC cells, including primary HCC cells. Stable knockdown of MAP3K7 attenuated tumor formation in a spheroid cell culture model and tumor xenograft mouse model. In addition, silencing MAP3K7 reduced the phosphorylation and expression of mammalian target of rapamycin (mTOR) in HCC cells. MAP3K7 expression was positively correlated with mTOR expression in tumors of patients with HCC. Higher co-expression of MAP3K7 and mTOR was significantly associated with poor prognosis of HCC. Taken together, our results revealed that the MAP3K7-mTOR axis might promote tumorigenesis and malignancy, which provides a potential marker or therapeutic target for HCC patients.

Targeting epigenetics using synthetic lethality in precision medicine

Technological breakthroughs in genomics have had a significant impact on clinical therapy for human diseases, allowing us to use patient genetic differences to guide medical care. The "synthetic lethal approach" leverages on cancer-specific genetic rewiring to deliver a therapeutic regimen that preferentially targets malignant cells while sparing normal cells. The utility of this system is evident in several recent studies, particularly in poor prognosis cancers with loss-of-function mutations that become "treatable" when two otherwise discrete and unrelated genes are targeted simultaneously. This review focuses on the chemotherapeutic targeting of epigenetic alterations in cancer cells and consolidates a network that outlines the interplay between epigenetic and genetic regulators in DNA damage repair. This network consists of numerous synergistically acting relationships that are druggable, even in recalcitrant triple-negative breast cancer. This collective knowledge points to the dawn of a new era of personalized medicine.

WEE1 inhibition targets cell cycle checkpoints for triple negative breast cancers to overcome cisplatin resistance

Cisplatin is one of the most commonly used therapeutic drugs for cancer therapy, yet prolonged cisplatin treatment frequently results in drug resistance. To enhance therapeutic effect of cisplatin, we conducted a high throughput screening using a kinase library containing 704 kinases against triple negative breast cancer (TNBC) cells. We demonstrated that cisplatin activates ATR, CHK1 and WEE1, which shut down DNA replication and attenuate cisplatin induced-lethality. WEE1 inhibition sensitizes TNBCs and cisplatin resistant cancer cells to cisplatin-induced lethality, because it not only impairs DNA replication checkpoint more profoundly than inhibition of ATR or CHK1, but also defects G2-M cell cycle checkpoint. Finally, we demonstrated that combined cisplatin treatment and WEE1 inhibition synergistically inhibits xenograft cancer growth accompanied by markedly reduced expression of TNBC signature genes. Thus targeting DNA replication and G2-M cell cycle checkpoint simultaneously by cisplatin and WEE1 inhibition is promising for TNBCs treatment, and for overcoming their cisplatin resistance.

Upregulation of p38 pathway accelerates proliferation and migration of MDA-MB-231 breast cancer cells

Tumor cells capture the signaling pathways used by normal tissue to promote their own survival and dissemination and among them, the NF-κB and MAPK pathways (ERK, JNK and p38). MAPK activation has ambiguous effects on tumor cell fate depending on cell type, cancer stage and the engaged MAPK isoforms. A synthetic peptide named LyeTx II, derived from the venom of the Brazilian spider Lycosa erythrognatha, was capable of increasing MDA-MB-231 aggressive breast cancer cell proliferation as indicated by MTT and BrdU (5-bromo-2'-deoxyuridine) incorporation assay and cell migration. A correlation has been established between the accelerated proliferation and migration observed in the presence of LyeTx II and the upregulation of p38 MAPK phosphorylation. The use of the selective inhibitor of p38α/β (SB203580) abrogated the peptide effect in MDA-MB-231 cells. Besides, an augment of the canonical NF-κB pathway activation considered as crucial in cancer progression was noted after cell incubation with LyeTx II. Importantly, activation of p38 and NF-κB pathways was dependent on TAK1 activity. Together, these data suggest that TAK1-p38 pathway may represent an interesting target for treatment of aggressive breast cancers.

TAK1 inhibitor NG25 enhances doxorubicin-mediated apoptosis in breast cancer cells

Doxorubicin (Dox, Adriamycin) has been widely used in breast cancer treatment. But its severe cardio-toxic side effects limited the clinical use. Dox treatment can induce DNA damage and other accompanying effects in cancer cells, and subsequently activates nuclear factor κB (NF-κB) pathway which has a strong pro-survival role in different types of malignancy. We hypothesize that blocking NF-κB pathway may sensitize breast cancer cells to Dox chemotherapy. TGFβ-activated kinase-1 (TAK1) is a key intracellular molecule participating in genotoxic stresses-induced NF-κB activation. Targeting TAK1 as a strategy to enhance cancer treatment efficacy has been studied in several malignancies. We showed that NG25, a synthesized TAK1 inhibitor, greatly enhanced Dox treatment efficacy in a panel of breast cancer cell lines. In this pre-clinical study, we found that NG25 partially blocked Dox-induced p38 phosphorylation and IκBα degradation and enhanced Dox-induced cytotoxic effects and apoptosis in all breast cancer cell lines tested. Taken together, we provided clear evidence that NG25 sensitizes the breast cancer cells to Dox treatment in vitro. This combination may be an effective and feasible therapeutic option maximizing Dox efficacy and meanwhile minimizing Dox side effects in treating breast cancer.

Targeting of TGF-β-activated protein kinase 1 inhibits chemokine (C-C motif) receptor 7 expression, tumor growth and metastasis in breast cancer

TGF-β-activated protein kinase 1 (TAK1) is a critical mediator in inflammation, immune response and cancer development. Our previous study demonstrated that activation of TAK1 increases the expression of chemokine (C-C motif) receptor 7 (CCR7) and promotes lymphatic invasion ability of breast cancer cells. However, the expression and association of activated TAK1 and CCR7 in breast tumor tissues is unknown and the therapeutic effect by targeting TAK1 is also unclear. We showed that activated TAK1 (as indicated by phospho-TAK1) and its binding protein TAB1 are strongly expressed in breast tumor tissues (77% and 74% respectively). In addition, increase of phospho-TAK1 or TAB1 is strongly associated with over-expression of CCR7. TAK1 inhibitor 5Z-7-Oxozeaenol (5Z-O) inhibited TAK1 activity, suppressed downstream signaling pathways including p38, IκB kinase (IKK) and c-Jun N-terminal kinase (JNK) and reduced CCR7 expression in metastatic MDA-MB-231 cells. In addition, 5Z-O repressed NF-κB- and c-JUN-mediated transcription of CCR7 gene. Knockdown of TAB1 attenuated CCR7 expression and tumor growth in an orthotopic animal study. More importantly, lymphatic invasion and lung metastasis were suppressed. Collectively, our results demonstrate that constitutive activation of TAK1 is frequently found in human breast cancer and this kinase is a potential therapeutic target for this cancer.

Identifying Novel Candidate Genes Related to Apoptosis from a Protein-Protein Interaction Network

Apoptosis is the process of programmed cell death (PCD) that occurs in multicellular organisms. This process of normal cell death is required to maintain the balance of homeostasis. In addition, some diseases, such as obesity, cancer, and neurodegenerative diseases, can be cured through apoptosis, which produces few side effects. An effective comprehension of the mechanisms underlying apoptosis will be helpful to prevent and treat some diseases. The identification of genes related to apoptosis is essential to uncover its underlying mechanisms. In this study, a computational method was proposed to identify novel candidate genes related to apoptosis. First, protein-protein interaction information was used to construct a weighted graph. Second, a shortest path algorithm was applied to the graph to search for new candidate genes. Finally, the obtained genes were filtered by a permutation test. As a result, 26 genes were obtained, and we discuss their likelihood of being novel apoptosis-related genes by collecting evidence from published literature.

Synergistic action of 5Z-7-oxozeaenol and bortezomib in inducing apoptosis of Burkitt lymphoma cell line Daudi

Treatment failure in cancer chemotherapy is largely due to the toxic effects of chemotherapeutic agents on normal cells/tissues. The proteasome inhibitor bortezomib has been successfully applied to treat multiple myeloma (MM), but there are some common adverse reactions in the clinic including peripheral neuropathy (PN). The TAK1 selective inhibitor 5Z-7-oxozeaenol has been widely studied in cancer therapy. Here, we investigated the potential synergy of bortezomib and 5Z-7-oxozeaenol in Burkitt's lymphoma (BL) cell lines. Cell viability assay showed that co-treatment of bortezomib at 8 nM, representing a one-eighth concentration for growth arrest, and 5Z-7-oxozeaenol at 2 μM, a dose that exhibited insignificant cytotoxic effects, synergistically induced apoptosis in the cell line Daudi. In parallel with the increasing dose of the bortezomib, and 5Z-7-oxozeaenol at 0.5 μM, lower colony formation efficiencies were seen in the cell line Daudi. Western blotting analysis verified that TAK1 inhibition by 5Z-7-oxozeaenol completely blocked JNK, p38, Erk, IKK, and IκB phosphorylation, which was almost instantly activated by TAK1 both directly or indirectly. Both agents synergistically prevented nuclear translocation of NF-κB, a characteristic of NF-κB inactivation. Moreover, a synergistic effect of bortezomib and 5Z-7-oxozeaenol on Western blotting analysis and flow cytometry was disclosed. Collectively, our results indicated that the proteasome inhibitor bortezomib and the TAK1 inhibitor 5Z-7-oxozeaenol displayed synergy on inhibiting BL cell apoptosis by inhibiting NF-κB activity.

Inhibition of ovarian cancer cell growth by a novel TAK1 inhibitor LYTAK1

PURPOSE

Transforming growth factor-β-activating kinase 1 (TAK1) has been implicated in promoting ovarian cancer progression. Here, we evaluated the anti-ovarian cancer effect of LYTAK1, a novel and specific TAK1 inhibitor.

METHODS

Established or primary human ovarian cancer cells were treated with LYTAK1, and its cytotoxicity and underlying mechanisms were analyzed using in vitro and in vivo assays.

RESULTS

We demonstrated that LYTAK1 blocked TAK1-nuclear factor kappa B activation, and potently inhibited growth of established (SKOV3, CaOV3 and A2780 lines) or primary (patient-derived) human ovarian cancer cells, where TAK1 was over-expressed and over-activated. While the normal ovarian epithelial cells (IOSE-80), with low TAK1 expression, were minimally affected by the same LYTAK1 treatment. In ovarian cancer cells, LYTAK1 mainly induced necrosis (but not apoptosis), which was associated with mitochondrial permeability transition pore (mPTP) opening, the latter was evidenced by mitochondrial membrane potential reduction. Inhibition of mPTP, either by its inhibitor sanglifehrin A or cyclosporine A, as well as by siRNA-mediated knockdown of cyclophilin-D or voltage-dependent anion channel, attenuated LYTAK1-induced necrosis and cytotoxicity in ovarian cancer cells. In vivo, LYTAK1 oral administration suppressed growth of SKOV3 xenografts in nude mice, and its activity could be further enhanced by co-treatment of paclitaxel (Taxol).

CONCLUSIONS

These data reveal the therapeutic potential of LYTAK1 as an agent targeting the pro-oncogenic TAK1 in ovarian cancer.

MiR-377 targets E2F3 and alters the NF-kB signaling pathway through MAP3K7 in malignant melanoma

Background

The incidence of cutaneous malignant melanoma continues to rise, and once the disease metastasizes it is almost inevitably fatal. We recently reported that a large miRNAs cluster on human chromosome 14q32, implicated in many types of cancers, is significantly down-regulated in melanoma. miR-377, one of the miRNAs located within this cluster, was studied here.

Methods

qRT-pCR was used to quantify miR-377 levels in melanoma cell lines and samples. Melanoma cell lines ectopically expressing miR-377 were generated by stable transfection, mRNA expression was assessed using mRNA arrays and protein expression was assessed by Western blot analysis. Potential targets of miR-377 were identified through luciferase reporter assays. Cellular proliferation, migration and soft-agar colony formation were monitored in control and miR-377-expressing cells using cell biology techniques.

Results

miR-377 is expressed in normal melanocytes but not in melanoma cell lines or samples. Its ectopic stable expression in melanoma cell lines decreased their proliferative and migratory capacity and their colony-forming capability. mRNA arrays of melanoma cells over-expressing miR-377 pointed to several down-regulated mRNAs that have putative binding sites for miR-377 in their 3′UTR, of which both E2F3 and MAP3K7 were found to be direct targets of miR-377.

E2F3, a potent transcriptional inducer of cell-cycle progression, was found to be elevated in melanoma cell lines, but decreased following ectopic expression of miR-377. Ectopic miR-377 also led to a decrease in the activity of a reporter plasmid containing three E2F DNA-binding sites linked to a luciferase cDNA sequence, demonstrating that miR-377 down-regulates E2F3-induced transcription.

MAP3K7 (known as TAK1), a serine/threonine kinase along the MAPK signaling pathway, was over-expressed in melanoma but decreased following ectopic expression of miR-377. MAP3K7 is involved in the activation of NF-κB. MiR-377 over-expression led to decreased activity of a reporter plasmid containing two NF-κB DNA-binding sites and to decreased output along the NF-kB signaling pathway.

Conclusion

Our results suggest that miR-377 is an important negative regulator of E2F and MAP3K7/NF-kB signaling pathway in melanoma cells; it is tempting to speculate that its silencing in melanoma promotes the tumorigenic and metastatic potential of the cells through activation of these pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0338-9) contains supplementary material, which is available to authorized users.

LYTAK1, a novel TAK1 inhibitor, suppresses KRAS mutant colorectal cancer cell growth in vitro and in vivo

KRAS mutation in colorectal cancer (CRC) activates transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) to promote tumor progression. In the current study, we explored the potential effect of LYTAK1, a novel TAK1 inhibitor, against KRAS mutant CRC cells in vitro and in vivo. We found that LYTAK1 dose-dependently inhibited KRAS mutant CRC cell (HT-29 and SW-620 lines) growth, and induced cell cycle G1-S arrest. Further, LYTAK1 activated apoptosis in HT-29 cells and SW-620 cells, and apoptosis inhibitors almost reversed LYTAK1-mediated growth inhibition. While in KRAS wild-type (WT) CRC cell lines (DLD-1 and HCT-116), LYTAK1 had almost no effect on cell growth, cell cycle progression, or cell apoptosis. In KRAS mutant HT-29 cells and SW-260 cells, LYTAK1 blocked TAK1 activation or phosphorylation at Thr-184/187. Activation of nuclear factor κB (NF-κB) in these cells, detected by phosphorylations of p65 and IκB kinase α (IKKα) as well as expression of NF-κB-regulated gene cyclin D1, was significantly inhibited by LYTAK1. Further, LYTAK1 treatment resulted in downregulation of β-catenin and Wnt response gene Axin 2, indicating Wnt inactivation. In vivo, oral LYTAK1 significantly inhibited HT-29 xenograft growth in nude mice. Together, these results show that LYTAK1 inhibits KRAS mutant CRC cell growth both in vitro and in vivo. LYTAK1 might be investigated as a novel agent against CRC with KRAS mutation.

ATR inhibitors VE-821 and VX-970 sensitize cancer cells to topoisomerase i inhibitors by disabling DNA replication initiation and fork elongation responses

Camptothecin and its derivatives, topotecan and irinotecan, are specific topoisomerase I (Top1) inhibitors and potent anticancer drugs killing cancer cells by producing replication-associated DNA double-strand breaks, and the indenoisoquinoline LMP-400 (indotecan) is a novel Top1 inhibitor in clinical trial. To develop novel drug combinations, we conducted a synthetic lethal siRNA screen using a library that targets nearly 7,000 human genes. Depletion of ATR, the main transducer of replication stress, came as a top candidate gene for camptothecin synthetic lethality. Validation studies using ATR siRNA and the ATR inhibitor VE-821 confirmed marked antiproliferative synergy with camptothecin and even greater synergy with LMP-400. Single-cell analyses and DNA fiber combing assays showed that VE-821 abrogates the S-phase replication elongation checkpoint and the replication origin-firing checkpoint induced by camptothecin and LMP-400. As expected, the combination of Top1 inhibitors with VE-821 inhibited the phosphorylation of ATR and Chk1; however, it strongly induced γH2AX. In cells treated with the combination, the γH2AX pattern changed over time from the well-defined Top1-induced damage foci to an intense peripheral and diffuse nuclear staining, which could be used as response biomarker. Finally, the clinical derivative of VE-821, VX-970, enhanced the in vivo tumor response to irinotecan without additional toxicity. A key implication of our work is the mechanistic rationale and proof of principle it provides to evaluate the combination of Top1 inhibitors with ATR inhibitors in clinical trials.

TAK1 inhibitor 5Z-7-oxozeaenol sensitizes neuroblastoma to chemotherapy

Treatment failure in high risk neuroblastoma is largely due to development of chemoresistance. NF-κB activation is one of the resistance mechanisms for cancer cells to escape from chemotherapy-induced cell-death. TAK1 is an essential component in genotoxic stresses-induced NF-κB activation; however, the role of TAK1 in the development of chemoresistance in neuroblastoma remains unknown. Using a panel of neuroblastoma cell lines, we found that TAK1 inhibitor 5Z-7-oxozeaenol significantly augmented the cytotoxic effects of doxorubicin (Dox) and etoposide (VP-16) on neuroblastoma cell lines. TAK1 inhibition also enhanced the inhibitory effect of Dox and VP-16 on anchorage-independent growth. Treatment of neuroblastoma cells with 5Z-7-oxozeaenol blocked Dox- and VP16-induced NF-κB activation and enhanced Dox- and VP16-induced apoptosis. Moreover, 5Z-7-oxozeaenol was able to overcome the established chemoresistance in LA-N-6 neuroblastoma cells. Using an orthotopic neuroblastoma mouse model, we found that 5Z-7-oxozeaenol significantly enhanced chemotherapeutic efficacy in vivo. Together, our results provide a proof-of-concept that TAK1 inhibition significantly increases the sensitivity of neuroblastoma cells to chemotherapy-induced cell-death and can serve as an effective adjunct to current chemotherapeutic regimens for high risk diseases.

TAK1 regulates hepatic cell survival and carcinogenesis

TGF-β-activated kinase 1 (TAK1 or MAP3K7) is an intracellular hub molecule that regulates both nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways that play key roles in development, cell survival, immune response, metabolism, and carcinogenesis. TAK1 activity is tightly regulated by its binding proteins, TAB1 and TAB2/TAB3, as well as by post-translational modification including ubiquitination and phosphorylation. Accumulating evidence demonstrates that TAK1 plays a role in tumor initiation, progression, and metastasis as a tumor prompter or tumor suppressor. An understanding of the role of TAK1 in liver physiology and diseases is required for the development of therapeutic agencies targeting TAK1. In this review, we highlight the activation mechanism and pathophysiological roles of TAK1 in the liver.

Fibroblast growth factor receptor 3 interacts with and activates TGFβ-activated kinase 1 tyrosine phosphorylation and NFκB signaling in multiple myeloma and bladder cancer

Cancer is a major public health problem worldwide. In the United States alone, 1 in 4 deaths is due to cancer and for 2013 a total of 1,660,290 new cancer cases and 580,350 cancer-related deaths are projected. Comprehensive profiling of multiple cancer genomes has revealed a highly complex genetic landscape in which a large number of altered genes, varying from tumor to tumor, impact core biological pathways and processes. This has implications for therapeutic targeting of signaling networks in the development of treatments for specific cancers. The NFκB transcription factor is constitutively active in a number of hematologic and solid tumors, and many signaling pathways implicated in cancer are likely connected to NFκB activation. A critical mediator of NFκB activity is TGFβ-activated kinase 1 (TAK1). Here, we identify TAK1 as a novel interacting protein and target of fibroblast growth factor receptor 3 (FGFR3) tyrosine kinase activity. We further demonstrate that activating mutations in FGFR3 associated with both multiple myeloma and bladder cancer can modulate expression of genes that regulate NFκB signaling, and promote both NFκB transcriptional activity and cell adhesion in a manner dependent on TAK1 expression in both cancer cell types. Our findings suggest TAK1 as a potential therapeutic target for FGFR3-associated cancers, and other malignancies in which TAK1 contributes to constitutive NFκB activation.

Inhibition of polo-like kinase 1 in glioblastoma multiforme induces mitotic catastrophe and enhances radiosensitisation

Glioblastoma multiforme (GBM) is the most common primary brain tumour in the United States of America (USA) with a median survival of approximately 14 months. Low survival rates are attributable to the aggressiveness of GBM and a lack of understanding of the molecular mechanisms underlying GBM. The disruption of signalling pathways regulated either directly or indirectly by protein kinases is frequently observed in cancer cells and thus the development of inhibitors of specific kinases has become a major focus of drug discovery in oncology. To identify protein kinases required for the survival of GBM we performed a siRNA-based RNAi screen focused on the human kinome in GBM. Inhibition of the polo-like kinase 1 (PLK1) induced a reduction in the viability in two different GBM cell lines. To assess the potential of inhibiting PLK1 as a treatment strategy for GBM we examined the effects of a small molecule inhibitor of PLK1, GSK461364A, on the growth of GBM cells. PLK1 inhibition arrested cells in the mitotic phase of the cell cycle and induced cell kill by mitotic catastrophe. GBM engrafts treated with GSK461364A showed statistically significant inhibition of tumour growth. Further, exposure of different GBM cells to RNAi or GSK461364A prior to radiation resulted in an increase in their radiosensitivity with dose enhancement factor ranging from 1.40 to 1.53 with no effect on normal cells. As a measure of DNA double strand breaks, γH2AX levels were significantly higher in the combined modality as compared to the individual treatments. This study suggests that PLK1 is an important therapeutic target for GBM and can enhance radiosensitivity in GBM.

Drugging topoisomerases: lessons and challenges

Topoisomerases are ubiquitous enzymes that control DNA supercoiling and entanglements. They are essential during transcription and replication, and topoisomerase inhibitors are among the most effective and most commonly used anticancer and antibacterial drugs. This review consists of two parts. In the first part ("Lessons"), it gives background information on the catalytic mechanisms of the different enzyme families (6 different genes in humans and 4 in most bacteria), describes the "interfacial inhibition" by which topoisomerase-targeted drugs act as topoisomerase poisons, and describes clinically relevant topoisomerase inhibitors. It generalizes the interfacial inhibition principle, which was discovered from the mechanism of action of topoisomerase inhibitors, and discusses how topoisomerase inhibitors kill cells by trapping topoisomerases on DNA rather than by classical enzymatic inhibition. Trapping protein-DNA complexes extends to a novel mechanism of action of PARP inhibitors and could be applied to the targeting of transcription factors. The second part of the review focuses on the challenges for discovery and precise use of topoisomerase inhibitors, including targeting topoisomerase inhibitors using chemical coupling and encapsulation for selective tumor delivery, use of pharmacodynamic biomarkers to follow drug activity, complexity of the response determinants for anticancer activity and patient selection, prospects of rational combinations with DNA repair inhibitors targeting tyrosyl-DNA-phosphodiesterases 1 and 2 (TDP1 and TDP2) and PARP, and the unmet need to develop inhibitors for type IA enzymes.

Dynamics of p53 and NF-κB regulation in response to DNA damage and identification of target proteins suitable for therapeutic intervention

Background

The genome is continuously attacked by a variety of agents that cause DNA damage. Recognition of DNA lesions activates the cellular DNA damage response (DDR), which comprises a network of signal transduction pathways to maintain genome integrity. In response to severe DNA damage, cells undergo apoptosis to avoid transformation into tumour cells, or alternatively, the cells enter permanent cell cycle arrest, called senescence. Most tumour cells have defects in pathways leading to DNA repair or apoptosis. In addition, apoptosis could be counteracted by nuclear factor kappa B (NF-κB), the main anti-apoptotic transcription factor in the DDR. Despite the high clinical relevance, the interplay of the DDR pathways is poorly understood. For therapeutic purposes DNA damage signalling processes are induced to induce apoptosis in tumour cells. However, the efficiency of radio- and chemotherapy is strongly hampered by cell survival pathways in tumour cells. In this study logical modelling was performed to facilitate understanding of the complexity of the signal transduction networks in the DDR and to provide cancer treatment options.

Results

Our comprehensive discrete logical model provided new insights into the dynamics of the DDR in human epithelial tumours. We identified new mechanisms by which the cell regulates the dynamics of the activation of the tumour suppressor p53 and NF-κB. Simulating therapeutic intervention by agents causing DNA single-strand breaks (SSBs) or DNA double-strand breaks (DSBs) we identified candidate target proteins for sensitization of carcinomas to therapeutic intervention. Further, we enlightened the DDR in different genetic diseases, and by failure mode analysis we defined molecular defects putatively contributing to carcinogenesis.

Conclusion

By logic modelling we identified candidate target proteins that could be suitable for radio- and chemotherapy, and contributes to the design of more effective therapies.

Roles of the kinase TAK1 in TRAF6-dependent signaling by CD40 and its oncogenic viral mimic, LMP1

The Epstein-Barr virus (EBV)-encoded protein latent membrane protein 1 (LMP1) is essential for EBV-mediated B cell transformation and plays a critical role in the development of post-transplant B cell lymphomas. LMP1 also contributes to the exacerbation of autoimmune diseases such as systemic lupus erythematosus (SLE). LMP1 is a functional mimic of the tumor necrosis factor receptor (TNFR) superfamily member CD40, and relies on TNFR-associated factor (TRAF) adaptor proteins to mediate signaling. However, LMP1 activation signals to the B cell are amplified and sustained compared to CD40 signals. We previously demonstrated that LMP1 and CD40 use TRAF molecules differently. Although associating with CD40 and LMP1 via separate mechanisms, TRAF6 plays a significant role in signal transduction by both. It is unknown whether TRAF6 mediates CD40 versus LMP1 functions via distinct or shared pathways. In this study, we tested the hypothesis that TRAF6 uses the kinase TAK1 to trigger important signaling pathways following both CD40 and LMP1 stimulation. We determined that TAK1 was required for JNK activation and interleukin-6 (IL-6) production mediated by CD40 and LMP1, in both mouse and human B cells. Additionally, TRAF3 negatively regulated TRAF6-dependent, CD40-mediated TAK1 activation by limiting TRAF6 recruitment. This mode of regulation was not observed for LMP1 and may contribute to the dysregulation of LMP1 compared to CD40 signals.

DNA damage-dependent NF-κB activation: NEMO turns nuclear signaling inside out

The dimeric transcription factor nuclear factor κB (NF-κB) functions broadly in coordinating cellular responses during inflammation and immune reactions, and its importance in the pathogenesis of cancer is increasingly recognized. Many of the signal transduction pathways that trigger activation of cytoplasmic NF-κB in response to a broad array of immune and inflammatory stimuli have been elaborated in great detail. NF-κB can also be activated by DNA damage, though relatively less is known about the signal transduction mechanisms that link DNA damage in the nucleus with activation of NF-κB in the cytoplasm. Here, we focus on the conserved signaling pathway that has emerged that promotes NF-κB activation following DNA damage. Post-translational modification of NF-κB essential modulator (NEMO) plays a central role in linking the cellular DNA damage response to NF-κB via the ataxia telangiectasia mutated (ATM) kinase. Accumulating evidence suggests that DNA damage-dependent NF-κB activation may play significant biological roles, particularly during lymphocyte differentiation and progression of human malignancies.

Targeting of TAK1 in inflammatory disorders and cancer

The transcription factors nuclear factor-κB (NF-κB) and activating protein-1 (AP-1) are critical regulators of stress responses, immunity, inflammation and cancer. A large variety of cellular stimuli utilize these signaling pathways through a common upstream kinase transforming growth factor-β-activated kinase 1 (TAK1). TAK1 was originally identified as a mitogen-activated kinase kinase kinase (MAP3K) activated by transforming growth factor-β (TGF-β); however, it has been characterized as a key regulator in inflammatory and immune signaling pathways. In addition, microbial proteins and components of host cell signaling scramble for the TAK1 complex in innate immunity. This review highlights the recent advances in the activation mechanisms and physiological functions of TAK1. Research targeting TAK1 raises the potential for new therapeutic options for inflammatory disorders, including cancer.