Promotion of DNA repair by nuclear IKKβ phosphorylation of ATM in response to genotoxic stimuli

ARID1A loss induces polymorphonuclear myeloid-derived suppressor cell chemotaxis and promotes prostate cancer progression

Chronic inflammation and an immunosuppressive microenvironment promote prostate cancer (PCa) progression and diminish the response to immune checkpoint blockade (ICB) therapies. However, it remains unclear how and to what extent these two events are coordinated. Here, we show that ARID1A, a subunit of the SWI/SNF chromatin remodeling complex, functions downstream of inflammation-induced IKKβ activation to shape the immunosuppressive tumor microenvironment (TME). Prostate-specific deletion of Arid1a cooperates with Pten loss to accelerate prostate tumorigenesis. We identify polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) as the major infiltrating immune cell type that causes immune evasion and reveal that neutralization of PMN-MDSCs restricts the progression of Arid1a-deficient tumors. Mechanistically, inflammatory cues activate IKKβ to phosphorylate ARID1A, leading to its degradation via β-TRCP. ARID1A downregulation in turn silences the enhancer of A20 deubiquitinase, a critical negative regulator of NF-κB signaling, and thereby unleashes CXCR2 ligand-mediated MDSC chemotaxis. Importantly, our results support the therapeutic strategy of anti-NF-κB antibody or targeting CXCR2 combined with ICB for advanced PCa. Together, our findings highlight that the IKKβ/ARID1A/NF-κB feedback axis integrates inflammation and immunosuppression to promote PCa progression.

Inhibiting WEE1 and IKK-RELA Crosstalk Overcomes TNFα Resistance in Head and Neck Cancers

TNFα is a key mediator of immune and radiotherapy-induced cytotoxicity, but many cancers, including head and neck squamous cell carcinomas (HNSCC), display TNF resistance due to activation of the canonical IKK-NF-κB/RELA pro-survival pathway. However, toxicities associated with direct targeting of the canonical pathway point to the need to identify mechanism(s) contributing to TNFα resistance and synthetic lethal targets to overcome such resistance in cancer cells. Here, RNAi screening for modulators of TNFα-NF-κB reporter activity and cell survival unexpectedly implicated the WEE1 and CDC2 G2-M checkpoint kinases. The IKKα/β-RELA and WEE1-CDC2 signaling pathways are activated by TNFα and form a complex in cell lines derived from both human papillomavirus (-) and (+) subtypes of HNSCC. WEE1 inhibitor AZD1775 reduced IKK/RELA phosphorylation and the expression of NF-κB-dependent pro-survival proteins Cyclin D1 and BCL2. Combination of TNFα and AZD1775 enhanced caspase-mediated apoptosis in vitro, and combination treatment with radiotherapy and AZD1775 potentiated inhibition of HNSCC tumor xenograft growth in vivo, which could be significantly attenuated by TNFα depletion. These data offer new insight into the interplay between NF-κB signaling and WEE1-mediated regulation of the G2-M cell-cycle checkpoint in HNSCC.

IMPLICATIONS

Inhibiting WEE1 and IKK-RELA crosstalk could potentially enhance the effects of therapies mediated by TNFα with less systemic immune suppression and toxicity than observed with direct interruption of IKK-NF-κB/RELA signaling.

MLK4 regulates DNA damage response and promotes triple-negative breast cancer chemoresistance

Chemoresistance constitutes a major challenge in the treatment of triple-negative breast cancer (TNBC). Mixed-Lineage Kinase 4 (MLK4) is frequently amplified or overexpressed in TNBC where it facilitates the aggressive growth and migratory potential of breast cancer cells. However, the functional role of MLK4 in resistance to chemotherapy has not been investigated so far. Here, we demonstrate that MLK4 promotes TNBC chemoresistance by regulating the pro-survival response to DNA-damaging therapies. We observed that MLK4 knock-down or inhibition sensitized TNBC cell lines to chemotherapeutic agents in vitro. Similarly, MLK4-deficient cells displayed enhanced sensitivity towards doxorubicin treatment in vivo. MLK4 silencing induced persistent DNA damage accumulation and apoptosis in TNBC cells upon treatment with chemotherapeutics. Using phosphoproteomic profiling and reporter assays, we demonstrated that loss of MLK4 reduced phosphorylation of key DNA damage response factors, including ATM and CHK2, and compromised DNA repair via non-homologous end-joining pathway. Moreover, our mRNA-seq analysis revealed that MLK4 is required for DNA damage-induced expression of several NF-кB-associated cytokines, which facilitate TNBC cells survival. Lastly, we found that high MLK4 expression is associated with worse overall survival of TNBC patients receiving anthracycline-based neoadjuvant chemotherapy. Collectively, these results identify a novel function of MLK4 in the regulation of DNA damage response signaling and indicate that inhibition of this kinase could be an effective strategy to overcome TNBC chemoresistance.

Role of HOXC10 in Cancer

The HOXC10 gene, a member of the HOX genes family, plays crucial roles in mammalian physiological processes, such as limb morphological development, limb regeneration, and lumbar motor neuron differentiation. HOXC10 is also associated with angiogenesis, fat metabolism, and sex regulation. Additional evidence suggests that HOXC10 dysregulation is closely associated with various tumors. HOXC10 is an important transcription factor that can activate several oncogenic pathways by regulating various target molecules such as ERK, AKT, p65, and epithelial mesenchymal transition-related genes. HOXC10 also induces drug resistance in cancers by promoting the DNA repair pathway. In this review, we summarize HOXC10 gene structure and expression as well as the role of HOXC10 in different human cancer processes. This review will provide insight into the status of HOXC10 research and help identify novel targets for cancer therapy.

Determining the prognostic significance of IKKα in prostate cancer

BACKGROUND

As the survival of castration-resistant prostate cancer (CRPC) remains poor, and the nuclear factor-κB (NF-κB) pathways play key roles in prostate cancer (PC) progression, several studies have focused on inhibiting the NF-κB pathway through generating inhibitory κB kinase subunit α (IKKα) small molecule inhibitors. However, the identification of prognostic markers able to discriminate which patients could benefit from IKKα inhibitors is urgently required. The present study investigated the prognostic value of IKKα, IKKα phosphorylated at serine 180 (p-IKKα S180) and threonine 23 (p-IKKα T23), and their relationship with the androgen receptor (AR) and Ki67 proliferation index to predict patient outcome.

METHODS

A cohort of 115 patients with hormone-naïve PC (HNPC) and CRPC specimens available were used to assess tumor cell expression of proteins within both the cytoplasm and the nucleus by immunohistochemistry. The expression levels were dichotomized (low vs high) to determine the associations between IKKα, AR, Ki67, and patients'Isurvival. In addition, an analysis was performed to assess potential IKKα associations with clinicopathological and inflammatory features, and potential IKKα correlations with other cancer pathways essential for CRPC growth.

RESULTS

High levels of cytoplasmic IKKα were associated with a higher cancer-specific survival in HNPC patients with low AR expression (hazards ratio [HR], 0.33; 95% confidence interval [CI] log-rank, 0.11-0.98; P = .04). Furthermore, nuclear IKKα (HR, 2.60; 95% CI, 1.27-5.33; P = .01) and cytoplasmic p-IKKα S180 (HR, 2.10; 95% CI, 1.17-3.76; P = .01) were associated with a lower time to death from recurrence in patients with CRPC. In addition, high IKKα expression was associated with high levels of T-cells (CD3+ P = .01 and CD8+ P = .03) in HNPC; however, under castration conditions, high IKKα expression was associated with high levels of CD68+ macrophages (P = .04), higher Gleason score (P = .01) and more prostate-specific antigen concentration (P = .03). Finally, we identified crosstalk between IKKα and members of the canonical NF-κB pathway in the nucleus of HNPC. Otherwise, IKKα phosphorylated by noncanonical NF-κB and Akt pathways correlated with members of the canonical NF-κB pathway in CRPC.

CONCLUSION

The present study reports that patients with CRPC expressing high levels of nuclear IKKα or cytoplasmic p-IKKα S180, which associated with a lower time to death from recurrence, may benefit from IKKα inhibitors.

Paeonol attenuates inflammation by targeting HMGB1 through upregulating miR-339-5p

Sepsis is a life-threatening disease caused by infection. Inflammation is a key pathogenic process in sepsis. Paeonol, an active ingredient in moutan cortex (a Chinese herb), has many pharmacological activities, such as anti-inflammatory and antitumour actions. Previous studies have indicated that paeonol inhibits the expression of HMGB1 and the transcriptional activity of NF-κB. However, its underlying mechanism is still unknown. In this study, microarray assay and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results confirmed that paeonol could significantly up-regulate the expression of miR-339-5p in RAW264.7 cells stimulated by LPS. Dual-luciferase assays indicated that miR-339-5p interacted with the 3′ untranslated region (3′-UTR) of HMGB1. Western blot, immunofluorescence and enzyme-linked immunosorbent assay (ELISA) analyses indicated that miR-339-5p mimic and siHMGB1 both negatively regulated the expression and secretion of inflammatory cytokines (e.g., HMGB1, IL-1β and TNF-α) in LPS-induced RAW264.7 cells. Studies have confirmed that IKK-β is targeted by miR-339-5p, and we further found that paeonol could inhibit IKK-β expression. Positive mutual feedback between HMGB1 and IKK-β was observed when we silenced HMGB1 or IKK-β. These results indicated that paeonol could attenuate the inflammation mediated by HMGB1 and IKK-β by upregulating miR-339-5p expression. In addition, we constructed CLP model mice by cecal ligation and puncture. Paeonol was used to intervene to investigate its anti-inflammatory effect in vivo. The results showed that paeonol could improve the survival rate of sepsis mice and protect the kidney of sepsis mice.

HOXC10 promotes gastric cancer cell invasion and migration via regulation of the NF-κB pathway

Homeobox gene C10 (HOXC10), known to regulate cell differentiation and proliferation, is upregulated in gastric cancer (GC). The mechanism underlying HOXC10 involvement in GC metastasis is unclear. Herein, we found that HOXC10 is overexpressed in GC relative to normal controls. In the 73 GC patients tissue microarrays (TMA) tested, HOXC10 expression was closely related with tumor-node-metastasis (TNM) stage, lymph node metastasis, and distant metastasis. HOXC10 overexpression tended to associate with low 5-year cumulative survival. Cox regression analysis identified HOXC10 as an independent prognostic factor for poor patient survival. HOXC10 promoted GC cell invasion and migration, regulated the expression of activated ATM and markers of NF-κB signaling. HOXC10 may promote invasion and migration of GC by regulating ATM/NF-κB signaling pathway. HOXC10 should be explored as a clinical marker of GC prognosis.

Context-Dependent Role of IKKβ in Cancer

Inhibitor of nuclear factor kappa-B kinase subunit beta (IKKβ) is a kinase principally known as a positive regulator of the ubiquitous transcription factor family Nuclear Factor-kappa B (NF-κB). In addition, IKKβ also phosphorylates a number of other proteins that regulate many cellular processes, from cell cycle to metabolism and differentiation. As a consequence, IKKβ affects cell physiology in a variety of ways and may promote or hamper tumoral transformation depending on hitherto unknown circumstances. In this article, we give an overview of the NF-κB-dependent and -independent functions of IKKβ. We also summarize the current knowledge about the relationship of IKKβ with cellular transformation and cancer, obtained mainly through the study of animal models with cell type-specific modifications in IKKβ expression or activity. Finally, we describe the most relevant data about IKKβ implication in cancer obtained from the analysis of the human tumoral samples gathered in The Cancer Genome Atlas (TCGA) and the Catalogue of Somatic Mutations in Cancer (COSMIC).

Prognostic value of GRIM-19, NF-κB and IKK2 in patients with high-grade serous ovarian cancer

AIMS

High grade serous carcinoma (HGSC) is an aggressive tumour, and most patients relapse after treatment, acquiring resistance to platinum-based chemotherapy. One of the resistance mechanisms proposed is apoptosis evasion triggered by drug-related cytotoxic effect in the cell. In this context, this study aims to evaluate the protein expression of GRIM-19, NF-κB and IKK2, their association with chemotherapy response and to determine their prognostic values in HGSC.

METHODS

GRIM-19, NF-κB and IKK2 expression was evaluated by immunohistochemistry (IHC) in 71 patients with HGSC selected between 2003 and 2013, whose underwent primary debulking surgery with complete cytoreduction. Protein expression was analyzed in relation to platinum response groups, tumour progression, clinicopathological data and survival.

RESULTS

Positive IKK2 expression was related to resistance (p = 0.011), shorter disease-free survival (p = 0.001) and overall survival (p = 0.026) and was also a risk factor for relapse (p = 0.002) and death (p = 0.032). The association between IKK2 and NF-κB positivity predicted a subgroup with shorter overall survival (p = 0.004), disease-free survival (p = 0.003) and resistance to platinum-based chemotherapy (p = 0.036). NF-κB positivity was associated with worse overall survival (p = 0.005) and disease-free survival (p = 0.027) and was a positive predictor for relapse (p = 0.032) and death (p = 0.008). Higher expression of GRIM-19 was associated with higher disease-free survival (p = 0.039) and was a negative predictor for relapse (p = 0.046).

CONCLUSIONS

GRIM-19 is a potential predictor of prognosis and disease recurrence in HGSC. IKK2 and NF-κB are related to poor prognosis and are potential predictors of response to platinum-based chemotherapy in HGSC. IHC analyses of GRIM19, IKK2 and NF-κB may be important in the attempt to provide prognostic values for relapse and response to treatment in patients with HGSC.

Sensitization of melanoma cells to alkylating agent-induced DNA damage and cell death via orchestrating oxidative stress and IKKβ inhibition

Nitrosourea represents one of the most active classes of chemotherapeutic alkylating agents for metastatic melanoma. Treatment with nitrosoureas caused severe systemic side effects which hamper its clinical use. Here, we provide pharmacological evidence that reactive oxygen species (ROS) induction and IKKβ inhibition cooperatively enhance nitrosourea-induced cytotoxicity in melanoma cells. We identified SC-514 as a ROS-inducing IKKβ inhibitor which enhanced the function of nitrosoureas. Elevated ROS level results in increased DNA crosslink efficiency triggered by nitrosoureas and IKKβ inhibition enhances DNA damage signals and sensitizes nitrosourea-induced cell death. Using xenograft mouse model, we confirm that ROS-inducing IKKβ inhibitor cooperates with nitrosourea to reduce tumor size and malignancy in vivo. Taken together, our results illustrate a new direction in nitrosourea treatment, and reveal that the combination of ROS-inducing IKKβ inhibitors with nitrosoureas can be potentially exploited for melanoma therapy.

Hypoxic preconditioning decreases nuclear factor κB activity via Disrupted in Schizophrenia-1

Nuclear factor κB is a key mediator of inflammation during conditions of hypoxia. Here, we used models of hypoxic pre-conditioning as mechanism to decrease nuclear factor κB activity induced by hypoxia. Our initial studies suggested that Disrupted in Schizophrenia-1 may be induced by hypoxic pre-conditioning and possibly involved in the regulation of nuclear factor κB. In this study we used Disrupted in Schizophrenia-1 exogenous over-expression and knock-down to determine its effect on ataxia telangiectasia mutated--nuclear factor κB activation cascade. Our results demonstrated that hypoxic pre-conditioning significantly increased the expression of Disrupted in Schizophrenia-1 at mRNA and protein levels both in vitro and in vivo. Over-expression of Disrupted in Schizophrenia-1 significantly attenuated the hypoxia-mediated ataxia telangiectasia mutated phosphorylation and prevented its cytoplasm translocation where it functions to activate nuclear factor κB. We further determined that Disrupted in Schizophrenia-1 activated the protein phosphatase 2A, preventing the phosphorylation of ataxia telangiectasia mutated serine-1981, the main regulatory site of ataxia telangiectasia mutated activity. Cellular levels of Disrupted in Schizophrenia-1 protein significantly decreased nuclear factor κB activation profiles and pro-inflammatory gene expression. Taken together, these results demonstrate that hypoxic pre-conditioning decreases the activation of nuclear factor κB through the transcriptional induction of Disrupted in Schizophrenia-1.

A novel pVHL-independent but NEMO-driven pathway in renal cancer promotes HIF stabilization

Activation of hypoxia-inducible factor (HIF) is due to loss of von Hippel-Lindau protein (pVHL) function in most clear cell renal cell carcinomas (ccRCCs). Here we describe a novel pVHL-independent mechanism of HIF regulation and identify nuclear factor (NF)-κB essential modulator (NEMO) as a hitherto unknown oncogenic factor influencing human ccRCC progression. Over 60% of human ccRCCs (n=157) have negative or weak NEMO protein expression by immunohistochemistry. Moderate/strong NEMO protein expression is more frequent in VHL wild-type ccRCCs. We show that NEMO stabilizes HIFα via direct interaction and independently of NF-κB signaling in vitro. NEMO prolongs tumor cell survival via regulation of apoptosis and activation of epithelial-to-mesenchymal transition, facilitating tumor metastasis. Our findings suggest that NEMO-driven HIF activation is involved in progression of ccRCC. Therefore, NEMO may represent a clinically relevant link between NF-κB and the VHL/HIF pathways. Targeting NEMO with specific inhibitors in patients with metastatic ccRCC could be a novel treatment approach in patients with ccRCC expressing functional pVHL.

Functional analyses of ATM, ATR and Fanconi anemia proteins in lung carcinoma : ATM, ATR and FA in lung carcinoma

Background

ATM and ATR are kinases implicated in a myriad of DNA-damage responses. ATM kinase inhibition radiosensitizes cells and selectively kills cells with Fanconi anemia (FA) gene mutations. ATR kinase inhibition sensitizes cells to agents that induce replication stress and selectively kills cells with ATM and TP53 mutations. ATM mutations and FANCF promoter-methylation are reported in lung carcinomas.

Methods

We undertook functional analyses of ATM, ATR, Chk1 and FA proteins in lung cancer cell lines. We included Calu6 that is reported to be FANCL-deficient. In addition, the cancer genome atlas (TCGA) database was interrogated for alterations in: 1) ATM, MRE11A, RAD50 and NBN; 2) ATR, ATRIP and TOPBP1; and 3) 15 FA genes.

Results

No defects in ATM, ATR or Chk1 kinase activation, or FANCD2 monoubiquitination were identified in the lung cancer cell lines examined, including Calu6, and major alterations in these pathways were not identified in the TCGA database. Cell lines were radiosensitized by ATM kinase inhibitor KU60019, but no cell killing by ATM kinase inhibitor alone was observed. While no synergy between gemcitabine or carboplatin and ATR kinase inhibitor ETP-46464 was observed, synergy between gemcitabine and Chk1 kinase inhibitor UCN-01 was observed in 54 T, 201 T and H460, and synergy between carboplatin and Chk1 kinase inhibitor was identified in 201 T and 239 T. No interactions between ATM, ATR and FA activation were observed by either ATM or ATR kinase inhibition in the lung cancer cell lines.

Conclusions

Analyses of ATM serine 1981 and Chk1 serine 345 phosphorylation, and FANCD2 monoubiquitination revealed that ATM and ATR kinase activation and FA pathway signaling are intact in the lung cancer cell lines examined. As such, these posttranslational modifications may have utility as biomarkers for the integrity of DNA damage signaling pathways in lung cancer. Different sensitization profiles between gemcitabine and carboplatin and ATR kinase inhibitor ETP-46464 and Chk1 kinase inhibitor UCN-01 were observed and this should be considered in the rationale for Phase I clinical trial design with ATR kinase inhibitors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1649-3) contains supplementary material, which is available to authorized users.

A quasi-quantitative dual multiplexed immunoblot method to simultaneously analyze ATM and H2AX Phosphorylation in human peripheral blood mononuclear cells

Pharmacologic inhibition of DNA repair may increase the efficacy of many cytotoxic cancer agents. Inhibitors of DNA repair enzymes including APE1, ATM, ATR, DNA-PK and PARP have been developed and the PARP inhibitor olaparib is the first-in-class approved in Europe and the USA for the treatment of advanced BRCA-mutated ovarian cancer. Sensitive pharmacodynamic (PD) biomarkers are needed to further evaluate the efficacy of inhibitors of DNA repair enzymes in clinical trials. ATM is a protein kinase that mediates cell-cycle checkpoint activation and DNA double-strand break repair. ATM kinase activation at DNA double-strand breaks (DSBs) is associated with intermolecular autophosphorylation on serine-1981. Exquisite sensitivity and high stoichiometry as well as facile extraction suggest that ATM serine-1981 phosphorylation may be a highly dynamic PD biomarker for both ATM kinase inhibitors and radiation- and chemotherapy-induced DSBs. Here we report the pre-clinical analytical validation and fit-for-purpose biomarker method validation of a quasi-quantitative dual multiplexed immunoblot method to simultaneously analyze ATM and H2AX phosphorylation in human peripheral blood mononuclear cells (PBMCs). We explore the dynamics of these phosphorylations in PBMCs exposed to chemotherapeutic agents and DNA repair inhibitors in vitro, and show that ATM serine-1981 phosphorylation is increased in PBMCs in sarcoma patients treated with DNA damaging chemotherapy.

New approaches to radiation protection

Radioprotectors are compounds that protect against radiation injury when given prior to radiation exposure. Mitigators can protect against radiation injury when given after exposure but before symptoms appear. Radioprotectors and mitigators can potentially improve the outcomes of radiotherapy for cancer treatment by allowing higher doses of radiation and/or reduced damage to normal tissues. Such compounds can also potentially counteract the effects of accidental exposure to radiation or deliberate exposure (e.g., nuclear reactor meltdown, dirty bomb, or nuclear bomb explosion); hence they are called radiation countermeasures. Here, we will review the general principles of radiation injury and protection and describe selected examples of radioprotectors/mitigators ranging from small-molecules to proteins to cell-based treatments. We will emphasize agents that are in more advanced stages of development.

An unconventional role of BMP-Smad1 signaling in DNA damage response: a mechanism for tumor suppression

The genome is under constant attack by self-produced reactive oxygen species and genotoxic reagents in the environment. Cells have evolved a DNA damage response (DDR) system to sense DNA damage, to halt cell cycle progression and repair the lesions, or to induce apoptosis if encountering irreparable damage. The best studied DDR pathways are the PIKK-p53 and PIKK-Chk1/2. Mutations in these genes encoding DDR molecules usually lead to genome instability and tumorigenesis. It is worth noting that there exist unconventional pathways that facilitate the canonical pathways or take over in the absence of the canonical pathways in DDR. This review will summarize on several unconventional pathways that participate in DDR with an emphasis on the BMP-Smad1 pathway, a known regulator of mouse development and bone remodeling.

Regulation of anoikis by deleted in breast cancer-1 (DBC1) through NF-κB

Anoikis-resistance of tumor cells is critical for anchorage-independent growth and metastasis. The inflammatory-response transcription factor NF-κB contributes to anoikis-resistance and tumor progression through mechanisms that are understood incompletely. Deleted in breast cancer-1 (DBC1) protein (KIAA1967) is over-expressed in several tumor types, and correlates with a poorer prognosis in some cases. We report here that DBC1 suppressed anoikis in normal epithelial and breast cancer cell lines. DBC1 interacted with IKK-β, stimulating its kinase activity, promoting NF-κB transcriptional activity through the phosphorylation of relA serine-536 and enhancing the expression of the NF-κB target genes, c-FLIP and bcl-xl. Our results indicate that DBC1 is an important co-factor for the control of the IKK-β-NF-κB signaling pathway that regulates anoikis.

Proteasome inhibition increases recruitment of IκB kinase β (IKKβ), S536P-p65, and transcription factor EGR1 to interleukin-8 (IL-8) promoter, resulting in increased IL-8 production in ovarian cancer cells

Proinflammatory and pro-angiogenic chemokine interleukin-8 (IL-8, CXCL8) contributes to ovarian cancer progression through its induction of tumor cell proliferation, survival, angiogenesis, and metastasis. Proteasome inhibition by bortezomib, which has been used as a frontline therapy in multiple myeloma, has shown only limited effectiveness in ovarian cancer and other solid tumors. However, the responsible mechanisms remain elusive. Here, we show that proteasome inhibition dramatically increases the IL-8 expression and release in ovarian cancer cells. The responsible mechanism involves an increased nuclear accumulation of IκB kinase β (IKKβ) and an increased recruitment of the nuclear IKKβ, p65-phosphorylated at Ser-536, and the transcription factor early growth response-1 (EGR-1) to the endogenous IL-8 promoter. Coimmunoprecipitation studies identified the nuclear EGR-1 associated with IKKβ and with p65, with preferential binding to S536P-p65. Both IKKβ activity and EGR-1 expression are required for the increased IL-8 expression induced by proteasome inhibition in ovarian cancer cells. Interestingly, in multiple myeloma cells the IL-8 release is not increased by bortezomib. Together, these data indicate that the increased IL-8 release may represent one of the underlying mechanisms responsible for the decreased effectiveness of proteasome inhibition in ovarian cancer treatment and identify IKKβ and EGR-1 as potential new targets in ovarian cancer combination therapies.