RelB regulates manganese superoxide dismutase gene and resistance to ionizing radiation of prostate cancer cells

cFLIP in the molecular regulation of astroglia-driven neuroinflammation in experimental glaucoma

BACKGROUND

Recent experimental studies of neuroinflammation in glaucoma pointed to cFLIP as a molecular switch for cell fate decisions, mainly regulating cell type-specific caspase-8 functions in cell death and inflammation. This study aimed to determine the importance of cFLIP for regulating astroglia-driven neuroinflammation in experimental glaucoma by analyzing the outcomes of astroglia-targeted transgenic deletion of cFLIP or cFLIPL.

METHODS

Glaucoma was modeled by anterior chamber microbead injections to induce ocular hypertension in mouse lines with or without conditional deletion of cFLIP or cFLIPL in astroglia. Morphological analysis of astroglia responses assessed quantitative parameters in retinal whole mounts immunolabeled for GFAP and inflammatory molecules or assayed for TUNEL. The molecular analysis included 36-plexed immunoassays of the retina and optic nerve cytokines and chemokines, NanoString-based profiling of inflammation-related gene expression, and Western blot analysis of selected proteins in freshly isolated samples of astroglia.

RESULTS

Immunoassays and immunolabeling of retina and optic nerve tissues presented reduced production of various proinflammatory cytokines, including TNFα, in GFAP/cFLIP and GFAP/cFLIPL relative to controls at 12 weeks of ocular hypertension with no detectable alteration in TUNEL. Besides presenting a similar trend of the proinflammatory versus anti-inflammatory molecules displayed by immunoassays, NanoString-based molecular profiling detected downregulated NF-κB/RelA and upregulated RelB expression of astroglia in ocular hypertensive samples of GFAP/cFLIP compared to ocular hypertensive controls. Analysis of protein expression also revealed decreased phospho-RelA and increased phospho-RelB in parallel with an increase in caspase-8 cleavage products.

CONCLUSIONS

A prominent response limiting neuroinflammation in ocular hypertensive eyes with cFLIP-deletion in astroglia values the role of cFLIP in the molecular regulation of glia-driven neuroinflammation during glaucomatous neurodegeneration. The molecular responses accompanying the lessening of neurodegenerative inflammation also seem to maintain astroglia survival despite increased caspase-8 cleavage with cFLIP deletion. A transcriptional autoregulatory response, dampening RelA but boosting RelB for selective expression of NF-κB target genes, might reinforce cell survival in cFLIP-deleted astroglia.

RelB is a potential molecular biomarker for immunotherapy in human pan-cancer

Introduction: The nuclear factor kB (NF-κB) pathway emerges as a critical regulator of immune responses and is often dysregulated in human cancers. It consists of a family of transcription factors involved in many biological responses. Activated NF-κB subunits results in the nuclear translocation and activation of transcription, and the NF-κB pathway is known to influence the transcription of many genes. Noncanonical NF-κB and its components have been shown to have effects, usually protumorigenic, in many different cancer types. Besides, NF-κB signaling had diverse and complicated roles in cancer with studies that NF-κB could both contribute to tumor promotion and suppression of oncogenesis relying on the cellular context. RelB, a member of noncanonical NF-κB was abnormally regulated in most cancer types, however the molecular features and clinical signature of RelB expression, as well as its role in cancer immunity in human pan-cancer remains to be elucidated. Methods: We used the open databases to explore RelB expression, clinical features and the association with tumor-infiltration cells in human pan-cancer. In this study, we investigated the aberration expression and prognostic significance of RelB, and the correlation with clinicopathological characters and immune cells infiltration in various cancers. The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases were used to analyze the mRNA expression level in different cancer types. Kaplan-Meier analysis and Cox regression were used to explore the prognostic significance of RelB in human pan-cancer. Then we took advantage of the TCGA database to analyze the relationship between RelB expression and DNA methylation, the infiltration of immune cells, immune checkpoint genes, tumor mutation burden (TMB), microsatellite instability (MSI), mismatch repair (MSS). Results: Higher expression of RelB was significantly detected in human cancer tissues and a high level of RelB expression was significantly linked with a worse outcome in LGG, KIPAN, ACC, UVM, LUAD,THYM, GBM, LIHC and TGCT but associated with a favorable overall survival (OS) in SARC, SKCM and BRCA. According to the Human Protein Altas database, RelB was considered as an independent factor in breast cancer and renal cancer prognosis. GSEA results revealed that RelB was involved in many oncogenesisrelated processes and immunity-related pathways. RelB was significantly correlated with DNA methylation in 13 types of cancer. Meanwhile, RelB expression was associated with TMB in 5 types of cancer and MSI in 8 types of cancer. In the final, we analyzed the relationship between RelB expression and immune-infiltration cells in human pan-cancer, which suggested RelB could be a promising therapeutic target for cancer immunotherapy. Discussion: Our study further provided insights into a deeper understanding of RelB as a prognostic biomarker.

Current Understanding of Flavonoids in Cancer Therapy and Prevention

Cancer is a major cause of death worldwide, with multiple pathophysiological manifestations. In particular, genetic abnormalities, inflammation, bad eating habits, radiation exposure, work stress, and toxin consumption have been linked to cancer disease development and progression. Recently, natural bioactive chemicals known as polyphenols found in plants were shown to have anticancer capabilities, destroying altered or malignant cells without harming normal cells. Flavonoids have demonstrated antioxidant, antiviral, anticancer, and anti-inflammatory effects. Flavonoid type, bioavailability, and possible method of action determine these biological actions. These low-cost pharmaceutical components have significant biological activities and are beneficial for several chronic disorders, including cancer. Recent research has focused primarily on isolating, synthesizing, and studying the effects of flavonoids on human health. Here we have attempted to summarize our current knowledge of flavonoids, focusing on their mode of action to better understand their effects on cancer.

Drivers of Radioresistance in Prostate Cancer

Prostate cancer (PCa) is the second most commonly diagnosed cancer worldwide. Radiotherapy remains one of the first-line treatments in localised disease and may be used as monotherapy or in combination with other treatments such as androgen deprivation therapy or radical prostatectomy. Despite advancements in delivery methods and techniques, radiotherapy has been unable to totally overcome radioresistance resulting in treatment failure or recurrence of previously treated PCa. Various factors have been linked to the development of tumour radioresistance including abnormal tumour vasculature, oxygen depletion, glucose and energy deprivation, changes in gene expression and proteome alterations. Understanding the biological mechanisms behind radioresistance is essential in the development of therapies that are able to produce both initial and sustained response to radiotherapy. This review will investigate the different biological mechanisms utilised by PCa tumours to drive radioresistance.

NRF2: A crucial regulator for mitochondrial metabolic shift and prostate cancer progression

Metabolic alterations are a common survival mechanism for prostate cancer progression and therapy resistance. Oxidative stress in the cellular and tumor microenvironment dictates metabolic switching in the cancer cells to adopt, prosper and escape therapeutic stress. Therefore, regulation of oxidative stress in tumor cells and in the tumor-microenvironment may enhance the action of conventional anticancer therapies. NRF2 is the master regulator for oxidative stress management. However, the overall oxidative stress varies with PCa clinical stage, metabolic state and therapy used for the cancer. In agreement, the blanket use of NRF2 inducers or inhibitors along with anticancer therapies cause adverse effects in some preclinical cancer models. In this review, we have summarized the levels of oxidative stress, metabolic preferences and NRF2 activity in the different stages of prostate cancer. We also propose condition specific ways to use NRF2 inducers or inhibitors along with conventional prostate cancer therapies. The significance of this review is not only to provide a detailed understanding of the mechanism of action of NRF2 to regulate oxidative stress-mediated metabolic switching by prostate cancer cells to escape the radiation, chemo, or hormonal therapies, and to grow aggressively, but also to provide a potential therapeutic method to control aggressive prostate cancer growth by stage specific proper use of NRF2 regulators.

Pro-inflammatory cytokines mediate the epithelial-to-mesenchymal-like transition of pediatric posterior fossa ependymoma

Pediatric ependymoma is a devastating brain cancer marked by its relapsing pattern and lack of effective chemotherapies. This shortage of treatments is due to limited knowledge about ependymoma tumorigenic mechanisms. By means of single-nucleus chromatin accessibility and gene expression profiling of posterior fossa primary tumors and distal metastases, we reveal key transcription factors and enhancers associated with the differentiation of ependymoma tumor cells into tumor-derived cell lineages and their transition into a mesenchymal-like state. We identify NFκB, AP-1, and MYC as mediators of this transition, and show that the gene expression profiles of tumor cells and infiltrating microglia are consistent with abundant pro-inflammatory signaling between these populations. In line with these results, both TGF-β1 and TNF-α induce the expression of mesenchymal genes on a patient-derived cell model, and TGF-β1 leads to an invasive phenotype. Altogether, these data suggest that tumor gliosis induced by inflammatory cytokines and oxidative stress underlies the mesenchymal phenotype of posterior fossa ependymoma.

Clair W, Clair DS. The RelB-BLNK Axis Determines Cellular Response to a Novel Redox-Active Agent Betamethasone during Radiation Therapy in Prostate Cancer

Aberrant levels of reactive oxygen species (ROS) are potential mechanisms that contribute to both cancer therapy efficacy and the side effects of cancer treatment. Upregulation of the non-canonical redox-sensitive NF-kB family member, RelB, confers radioresistance in prostate cancer (PCa). We screened FDA-approved compounds and identified betamethasone (BET) as a drug that increases hydrogen peroxide levels in vitro and protects non-PCa tissues/cells while also enhancing radiation killing of PCa tissues/cells, both in vitro and in vivo. Significantly, BET increases ROS levels and exerts different effects on RelB expression in normal cells and PCa cells. BET induces protein expression of RelB and RelB target genes, including the primary antioxidant enzyme, manganese superoxide dismutase (MnSOD), in normal cells, while it suppresses protein expression of RelB and MnSOD in LNCaP cells and PC3 cells. RNA sequencing analysis identifies B-cell linker protein (BLNK) as a novel RelB complementary partner that BET differentially regulates in normal cells and PCa cells. RelB and BLNK are upregulated and correlate with the aggressiveness of PCa in human samples. The RelB-BLNK axis translocates to the nuclear compartment to activate MnSOD protein expression. BET promotes the RelB-BLNK axis in normal cells but suppresses the RelB-BLNK axis in PCa cells. Targeted disruptions of RelB-BLNK expressions mitigate the radioprotective effect of BET on normal cells and the radiosensitizing effect of BET on PCa cells. Our study identified a novel RelB complementary partner and reveals a complex redox-mediated mechanism showing that the RelB-BLNK axis, at least in part, triggers differential responses to the redox-active agent BET by stimulating adaptive responses in normal cells but pushing PCa cells into oxidative stress overload.

A hypothesis for the pathogenesis of radiation-induced oral mucositis: when biological challenges exceed physiologic protective mechanisms. Implications for pharmacological prevention and treatment

Oral mucositis (OM) remains a significant unmet need for patients being treated with standard concomitant chemoradiation (CRT) regimens for head and neck cancers (HNC). OM's pathogenesis is complex and includes both direct and indirect damage pathways. In this paper, the field is reviewed with emphasis on the initiating and sustaining role of oxidative stress on OM's pathobiology. A hypothesis is presented which suggests that based on OM's clinical and biological trajectory, mucosal damage is largely the consequence of cumulative CRT-induced biological changes overwhelming physiologic self-protective mechanisms. Furthermore, an individual's ability to mount and maintain a protective response is dependent on interacting pathways which are primarily determined by a multiplex consisting of genomics, epigenomics, and microbiomics. Effective biologic or pharmacologic OM interventions are likely to supplement or stimulate existing physiologic damage-control mechanisms.

Key radioresistance regulation models and marker genes identified by integrated transcriptome analysis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy that is endemic to China and Southeast Asia. Radiotherapy is the usual treatment, however, radioresistance remains a major reason for failure. This study aimed to find key radioresistance regulation models and marker genes of NPC and clarify the mechanism of NPC radioresistance by RNA sequencing and bioinformatics analysis of the differences in gene expression profiles between radioresistant and radiosensitive NPC tissues. A total of 21 NPC biopsy specimens with different radiosensitivity were analyzed by RNA sequencing. Differentially expressed genes in RNA sequencing data were identified using R software. The differentially expressed gene data derived from RNA sequencing as well as prior knowledge in the form of pathway databases were integrated to find sub‐networks of related genes. The data of RNA sequencing with the GSE48501 data from the GEO database were combined to further search for more reliable genes associated with radioresistance of NPC. Survival analyses using the Kaplan–Meier method based on the expression of the genes were conducted to facilitate the understanding of the clinical significance of the differentially expressed genes. RT‐qPCR was performed to validate the expression levels of the differentially expressed genes. We identified 1182 differentially expressed genes between radioresistant and radiosensitive NPC tissue samples. Compared to the radiosensitive group, 22 genes were significantly upregulated and 1160 genes were downregulated in the radioresistant group. In addition, 10 major NPC radiation resistance network models were identified through integration analysis with known NPC radiation resistance‐associated genes and mechanisms. Furthermore, we identified three core genes, DOCK4, MCM9, and POPDC3 among 12 common downregulated genes in the two datasets, which were validated by RT‐qPCR. The findings of this study provide new clues for clarifying the mechanism of NPC radioresistance, and further experimental studies of these core genes are warranted.

Radiation Resistance: A Matter of Transcription Factors

Currently, radiation therapy is one of the standard therapies for cancer treatment. Since the first applications, the field of radiotherapy has constantly improved, both in imaging technologies and from a dose-painting point of view. Despite this, the mechanisms of resistance are still a great problem to overcome. Therefore, a more detailed understanding of these molecular mechanisms will allow researchers to develop new therapeutic strategies to eradicate cancer effectively. This review focuses on different transcription factors activated in response to radiotherapy and, unfortunately, involved in cancer cells’ survival. In particular, ionizing radiations trigger the activation of the immune modulators STAT3 and NF-κB, which contribute to the development of radiation resistance through the up-regulation of anti-apoptotic genes, the promotion of proliferation, the alteration of the cell cycle, and the induction of genes responsible for the Epithelial to Mesenchymal Transition (EMT). Moreover, the ROS-dependent damaging effects of radiation therapy are hampered by the induction of antioxidant enzymes by NF-κB, NRF2, and HIF-1. This protective process results in a reduced effectiveness of the treatment, whose mechanism of action relies mainly on the generation of free oxygen radicals. Furthermore, the previously mentioned transcription factors are also involved in the maintenance of stemness in Cancer Stem Cells (CSCs), a subset of tumor cells that are intrinsically resistant to anti-cancer therapies. Therefore, combining standard treatments with new therapeutic strategies targeted against these transcription factors may be a promising opportunity to avoid resistance and thus tumor relapse.

Resveratrol Inhibits Ischemia-Induced Myocardial Senescence Signals and NLRP3 Inflammasome Activation

Aims

The aim of this study was to investigate whether resveratrol (RSV) could ameliorate ischemia- and hypoxia-associated cardiomyocyte apoptosis and injury via inhibiting senescence signaling and inflammasome activation.

Materials and Methods

Mice were treated with RSV by gastric tube (320 mg/kg/day) or vehicle one week before left coronary artery ligation or sham surgery until the end of the experiments. After pressure–volume loop analysis, mouse hearts were harvested for histopathological (including PSR, TTC, TUNEL staining, immunohistochemistry, and immunofluorescence) and molecular analysis by western blotting and RT-PCR. In addition, neonatal rat cardiomyocytes (NRCMs), cardiac fibroblasts (CFs), and macrophages were isolated for in vitro experiments. Key Findings. RSV treatment decreased mortality and improved cardiac hemodynamics. RSV inhibited the expression of senescence markers (p53, p16, and p19), inflammasome markers (NLRP3 and Cas1 p20), and nuclear translocation of NF-κB, hence alleviating infarction area, fibrosis, and cell apoptosis. RSV also inhibited expression of interleukin- (IL-) 1β, IL-6, tumor necrosis factor-α, and IL-18 in vivo. In in vitro experiment, RSV prevented hypoxia-induced NRCM senescence and apoptosis. After inhibition of sirtuin 1 (Sirt1) by EX27, RSV failed to inhibit p53 acetylation and expression. Moreover, RSV could inhibit expression of NLRP3 and caspase 1 p20 in NRCMs, CFs, and macrophages, respectively, in in vitro experiments. Significance. Our findings revealed that RSV protected against ischemia-induced mouse heart injury in vivo and hypoxia-induced NRCM injury in vitro via regulating Sirt1/p53-mediated cell senescence and inhibiting NLRP3-mediated inflammasome activation.

DNA-PKcs is activated under nutrient starvation and activates Akt, MST1, FoxO3a, and NDR1

BACKGROUND

Presence of unperfused regions containing cells under hypoxia and nutrient starvation; contributes to radioresistance in solid human tumors. We have previously reported that cultured cells; under nutrient starvation show resistance to ionizing radiation compare with cells under normal; condition, and that nutrient starvation increases ATM activity, which causes cellular resistance to; ionizing radiation (Murata et al., BBRC2018). For further investigation of molecular mechanisms; underlying radioresistance of cells under nutrient starvation, effects of nutrient starvation on activity; of DNA-PKcs have been investigated because both DNA-PKcs and ATM belong to the PIKK family; and are required for DNA DSBs repair. In addition to DNA-PKcs, effects of nutrient starvation on; activities of FoxO3a and its regulators Akt, MST1 and AMPK have been investigated because FoxO3a; mediates cellular responses to stress and is activated under nutrient starvation.

METHODS

A human glioblastoma cell line, T98G was used to examine the effects of nutrient starvation on activities and expression of DNA-PKcs, Akt, MST1, FoxO3a, NDR1, and AMPK. To elucidate; signal transduction pathways for FoxO3a activation under nutrient starvation, we examined effects of; specific inhibitors or siRNA for DNA-PKcs or Akt on activities and expression of MST1, FoxO3, NDR1, andAMPK.

RESULTS

Under nutrient starvation, phosphorylations of DNA-PKcs at Ser2056, Akt at Ser473, MST at Thr183, FoxO3a at Ser413, NDR1 at Ser281 and Thr282, and AMPK at Thr172 were increased, which suggests their activation. Nutrient starvation did not affect expression of DNA-PKcs, Akt, MST1, or NDR1, with decreased expression of FoxO3a and increased expression of AMPK. Inhibition; of DNA-PK suppressed phosphorylation of Akt under nutrient starvation. Inhibition of DNA-PK or; Akt suppressed phosphorylations of MST1, FoxO3a, and NDR1 under nutrient starvation, which; suggests DNA-PKcs and Akt activate MST1, FoxO3a, and NDR1. Inhibition of DNA-PK did not; suppress phosphorylation ofAMPK under nutrient starvation.

CONCLUSION

Our data suggest that DN-PKcs is activated under nutrient starvation and activates AktMST1, FoxO3a, and NDR1.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

miR-17-3p Downregulates Mitochondrial Antioxidant Enzymes and Enhances the Radiosensitivity of Prostate Cancer Cells

Radioresistance remains to be a major obstacle in the management of patients with advanced prostate cancer (PCa). We have identified a mature miR-17-3p processed from the 3' arm of precursor miR-17, which appeared to be able to inhibit three major antioxidant enzymes located in mitochondria, i.e., manganese superoxide dismutase (MnSOD), glutathione peroxidase 2 (Gpx2), and thioredoxin reductase 2 (TrxR2). Here we show that upregulation of miR-17-3p remarkably sensitized PCa cells to ionizing radiation (IR). Reductions of the three antioxidants led to increasing cellular reactive oxygen species (ROS) accumulation as well as declining mitochondrial respiration. The miR-17-3p-mediated dysfunction of mitochondrial antioxidants apparently sensitizing IR therapy was manifested in vitro and in vivo. Substantially, the miR-17-3p effect on suppression of the antioxidants can be efficiently eliminated or attenuated by transfecting with either an miR-17-3p inhibitor or each of the related antioxidant cDNA expression constructs. Overall, in addition to the insights into the functional assessments for the duplex of miR-17-5p and miR-17-3p, the present study highlights the rigorous evidence that demonstrated suppression of multiple mitochondrial antioxidants by a single microRNA (miRNA), thereby providing a promising approach to improve radiotherapy for advanced PCa by targeting mitochondrial function.

RelB plays an oncogenic role and conveys chemo-resistance to DLD-1 colon cancer cells

Background

Nuclear transcription factor kappa B (NF-κB) subunits exhibit crucial roles in tumorigenesis and chemo-sensitivity. Recent studies suggest that RelB, the key subunit of the alternative NF-κB pathway, plays a critical role in the progression of diverse human malignancies. However, the significance of RelB in colorectal cancer (CRC) remains unclear. Here, we systematically explored the functions of the alternative NF-κB subunit RelB in colon cancer cells and its underlying mechanism.

Methods

Stably transfected RelB-shRNA DLD-1 cells were established using Lipofectamine 2000. NF-κB DNA-binding capability was quantified using an ELISA-based NF-κB activity assay. Cell growth was monitored by an x-Celligence system. Cell proliferation was analyzed by a CCK-8 and a Brdu proliferation assay. Response to 5-FU was assessed by an x-Celligence system. Cell apoptosis and cell cycle was detected using flow cytometry analyses. Cell migration and invasion abilities were detected by an x-Celligence system, Transwell inserts, and wound-healing assays. RelB expression and its clinical significance were analyzed using the CRC tissue microarray. The expression of NF-κB signaling subunits, AKT/mTOR signaling molecules, cell cycle related proteins, MMP2, MMP9, and Integrin β-1 were measured by Western blotting analyses.

Results

The RelB-silencing inhibited cell growth of DLD-1 cells. The RelB-silencing exerted the anti-proliferative by downregulation of AKT/mTOR signaling. The RelB-silencing caused G₀–G₁ cell cycle arrested likely due to decreasing the expression of Cyclin D1 and CDK4, concomitant with increased expression of p27^Kip1. The RelB-silencing enhanced cytotoxic effect of 5-FU and induced cell accumulation in S-phase. The RelB-silencing impaired the migration and invasion potential of DLD-1 cells, which was related to downregulation of MMP2, MMP9, and Integrin β-1. Importantly, the RelB expression was correlated with depth of tumor invasion, lymph node metastasis, metastasis stage, and pTNM stage. High-RelB expression was significantly correlated with poor overall survival in CRC patients.

Conclusion

Our studies here provided evidence that RelB plays an oncogenic role and conveys chemo-resistance to 5-FU. RelB can be considered as an independent indicator of prognosis in CRC.

The Role of the Nuclear Factor κB Pathway in the Cellular Response to Low and High Linear Energy Transfer Radiation

Astronauts are exposed to considerable doses of space radiation during long-term space missions. As complete shielding of the highly energetic particles is impracticable, the cellular response to space-relevant radiation qualities has to be understood in order to develop countermeasures and to reduce radiation risk uncertainties. The transcription factor Nuclear Factor κB (NF-κB) plays a fundamental role in the immune response and in the pathogenesis of many diseases. We have previously shown that heavy ions with a linear energy transfer (LET) of 100–300 keV/µm have a nine times higher potential to activate NF-κB compared to low-LET X-rays. Here, chemical inhibitor studies using human embryonic kidney cells (HEK) showed that the DNA damage sensor Ataxia telangiectasia mutated (ATM) and the proteasome were essential for NF-κB activation in response to X-rays and heavy ions. NF-κB’s role in cellular radiation response was determined by stable knock-down of the NF-κB subunit RelA. Transfection of a RelA short-hairpin RNA plasmid resulted in higher sensitivity towards X-rays, but not towards heavy ions. Reverse Transcriptase real-time quantitative PCR (RT-qPCR) showed that after exposure to X-rays and heavy ions, NF-κB predominantly upregulates genes involved in intercellular communication processes. This process is strictly NF-κB dependent as the response is completely absent in RelA knock-down cells. NF-κB’s role in the cellular radiation response depends on the radiation quality.

HZ08 suppresses RelB-activated MnSOD expression and enhances Radiosensitivity of prostate Cancer cells

Background

The development of radioresistance is one of main causes for therapeutic failure of prostate cancer (PCa). The present study aims to investigate the function and the related mechanism by which HZ08 sensitizes radiotherapeutic efficiency to treat aggressive PCa cells.

Methods

PCa cells were pretreated with HZ08 (6,7-dimethoxy-1-(3,4-dimethoxy) benzyl-2-(N-n-octyl-N′-cyano) guanyl-1,2,3,4-tetrahydroisoquinoline) and followed by ionizing radiation (IR) treatment. Cytotoxicity in the treated cells was analyzed to assess the radiosensitization capacity of HZ08 by flow cytometry, MTT and colony survival assays. The cellular levels of reactive oxygen species (ROS) and oxygen consumption rates (OCR) were measured using specific ROS detection probes and a Seahorse XF96 Analyzer, respectively. RelB binding to the NF-κB intronic enhancer region of the human SOD2 gene was determined using a ChIP assay. The levels of phosphorylation of PI3K, Akt and IKKα were quantified and further confirmed using a PI3K inhibitor. Finally, the synergistic effect of HZ08 on radiosensitization of PCa cells was validated using a mouse xenograft tumor model.

Results

HZ08 enhanced radiosensitivity of PCa cells through increasing ROS and declining mitochondrial respiration due to suppression of mitochondrial antioxidant enzyme MnSOD. Mechanistically, HZ08 appeared to inhibit PI3K/Akt/IKKα signaling axis, resulting in transcriptional repression of MnSOD expression by preventing RelB nuclear translocation.

Conclusions

HZ08 can serve as a useful radiosensitizing agent to improve radiotherapy for treating aggressive PCa cells with high level of constitutive RelB. The present study suggests a promising approach for enhancing radiotherapeutic efficiency to treat advanced PCa by inhibiting antioxidant defense function.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0849-5) contains supplementary material, which is available to authorized users.

NF-κB pathways in the development and progression of colorectal cancer

Nuclear factor-κB (NF-κB) has been widely implicated in the development and progression of cancer. In colorectal cancer (CRC), NF-κB has a key role in cancer-related processes such as cell proliferation, apoptosis, angiogenesis, and metastasis. The role of NF-κB in CRC is complex, owed to the cross talk with other signaling pathways. Although there is sufficient evidence gained from cell lines and animal models that NF-κB is involved in cancer-related processes, because of a lack of studies in human tissue, the clinical evidence of its importance is limited in patients with CRC. This review summarizes evidence relating to how NF-κB is involved in the development and progression of CRC and comments on future work to be carried out.

Clair DK, Kyprianou N. Profiles of Radioresistance Mechanisms in Prostate Cancer

Radiation therapy (RT) is commonly used for the treatment of localized prostate cancer (PCa). However, cancer cells often develop resistance to radiation through unknown mechanisms and pose an intractable challenge. Radiation resistance is highly unpredictable, rendering the treatment less effective in many patients and frequently causing metastasis and cancer recurrence. Understanding the molecular events that cause radioresistance in PCa will enable us to develop adjuvant treatments for enhancing the efficacy of RT. Radioresistant PCa depends on the elevated DNA repair system and the intracellular levels of reactive oxygen species (ROS) to proliferate, self-renew, and scavenge anti-cancer regimens, whereas the elevated heat shock protein 90 (HSP90) and the epithelial-mesenchymal transition (EMT) enable radioresistant PCa cells to metastasize after exposure to radiation. The up-regulation of the DNA repairing system, ROS, HSP90, and EMT effectors has been studied extensively, but not targeted by adjuvant therapy of radioresistant PCa. Here, we emphasize the effects of ionizing radiation and the mechanisms driving the emergence of radioresistant PCa. We also address the markers of radioresistance, the gene signatures for the predictive response to radiotherapy, and novel therapeutic platforms for targeting radioresistant PCa. This review provides significant insights into enhancing the current knowledge and the understanding toward optimization of these markers for the treatment of radioresistant PCa.

Radiation-Induced Oral Mucositis

Radiation-induced oral mucositis (RIOM) is a major dose-limiting toxicity in head and neck cancer patients. It is a normal tissue injury caused by radiation/radiotherapy (RT), which has marked adverse effects on patient quality of life and cancer therapy continuity. It is a challenge for radiation oncologists since it leads to cancer therapy interruption, poor local tumor control, and changes in dose fractionation. RIOM occurs in 100% of altered fractionation radiotherapy head and neck cancer patients. In the United Sates, its economic cost was estimated to reach 17,000.00 USD per patient with head and neck cancers. This review will discuss RIOM definition, epidemiology, impact and side effects, pathogenesis, scoring scales, diagnosis, differential diagnosis, prevention, and treatment.

Protein Kinase C Epsilon Cooperates with PTEN Loss for Prostate Tumorigenesis through the CXCL13-CXCR5 Pathway

PKCε, an oncogenic member of the PKC family, is aberrantly overexpressed in epithelial cancers. To date, little is known about functional interactions of PKCε with other genetic alterations, as well as the effectors contributing to its tumorigenic and metastatic phenotype. Here, we demonstrate that PKCε cooperates with the loss of the tumor suppressor Pten for the development of prostate cancer in a mouse model. Mechanistic analysis revealed that PKCε overexpression and Pten loss individually and synergistically upregulate the production of the chemokine CXCL13, which involves the transcriptional activation of the CXCL13 gene via the non-canonical nuclear factor κB (NF-κB) pathway. Notably, targeted disruption of CXCL13 or its receptor, CXCR5, in prostate cancer cells impaired their migratory and tumorigenic properties. In addition to providing evidence for an autonomous vicious cycle driven by PKCε, our studies identified a compelling rationale for targeting the CXCL13-CXCR5 axis for prostate cancer treatment.

RelB Expression Determines the Differential Effects of Ascorbic Acid in Normal and Cancer Cells

Cancer cells typically experience higher oxidative stress than normal cells, such that elevating pro-oxidant levels can trigger cancer cell death. Although pre-exposure to mild oxidative agents will sensitize cancer cells to radiation, this pre-exposure may also activate the adaptive stress defense system in normal cells. Ascorbic acid is a prototype redox modulator that when infused intravenously appears to kill cancers without injury to normal tissues; however, the mechanisms involved remain elusive. In this study, we show how ascorbic acid kills cancer cells and sensitizes prostate cancer to radiation therapy while also conferring protection upon normal prostate epithelial cells against radiation-induced injury. We found that the NF-κB transcription factor RelB is a pivotal determinant in the differential radiosensitization effects of ascorbic acid in prostate cancer cells and normal prostate epithelial cells. Mechanistically, high reactive oxygen species concentrations suppress RelB in cancer cells. RelB suppression decreases expression of the sirtuin SIRT3 and the powerful antioxidant MnSOD, which in turn increases oxidative and metabolic stresses in prostate cancer cells. In contrast, ascorbic acid enhances RelB expression in normal cells, improving antioxidant and metabolic defenses against radiation injury. In addition to showing how RelB mediates the differential effects of ascorbic acid on cancer and normal tissue radiosensitivities, our work also provides a proof of concept for the existence of redox modulators that can improve the efficacy of radiotherapy while protecting against normal tissue injury in cancer settings. Cancer Res; 77(6); 1345-56. ©2017 AACR.

Transcription Factors in the Cellular Response to Charged Particle Exposure

Charged particles, such as carbon ions, bear the promise of a more effective cancer therapy. In human spaceflight, exposure to charged particles represents an important risk factor for chronic and late effects such as cancer. Biological effects elicited by charged particle exposure depend on their characteristics, e.g., on linear energy transfer (LET). For diverse outcomes (cell death, mutation, transformation, and cell-cycle arrest), an LET dependency of the effect size was observed. These outcomes result from activation of a complex network of signaling pathways in the DNA damage response, which result in cell-protective (DNA repair and cell-cycle arrest) or cell-destructive (cell death) reactions. Triggering of these pathways converges among others in the activation of transcription factors, such as p53, nuclear factor κB (NF-κB), activated protein 1 (AP-1), nuclear erythroid-derived 2-related factor 2 (Nrf2), and cAMP responsive element binding protein (CREB). Depending on dose, radiation quality, and tissue, p53 induces apoptosis or cell-cycle arrest. In low LET radiation therapy, p53 mutations are often associated with therapy resistance, while the outcome of carbon ion therapy seems to be independent of the tumor's p53 status. NF-κB is a central transcription factor in the immune system and exhibits pro-survival effects. Both p53 and NF-κB are activated after ionizing radiation exposure in an ataxia telangiectasia mutated (ATM)-dependent manner. The NF-κB activation was shown to strongly depend on charged particles' LET, with a maximal activation in the LET range of 90-300 keV/μm. AP-1 controls proliferation, senescence, differentiation, and apoptosis. Nrf2 can induce cellular antioxidant defense systems, CREB might also be involved in survival responses. The extent of activation of these transcription factors by charged particles and their interaction in the cellular radiation response greatly influences the destiny of the irradiated and also neighboring cells in the bystander effect.

HSP90 Inhibitor Geldanamycin as a Radiation Response Modificator in Human Blood Cells

Heat shock protein 90 (Hsp90) is a highly conserved molecular chaperone, involved in the folding, assembly, stabilization and activation of numerous proteins with unrelated amino acid sequences and functions. Geldanamycin (GA), a natural benzoquinone, can inhibit the chaperone activity of Hsp90. It has been shown that GA can produce superoxide anions and increase the intracellular oxidative stress, which, in addition to the direct inhibition of Hsp90, might also contribute to the modifying effects of the inhibitor on the early response in human mononuclear cells exposed to ionizing radiation. The present study shows that GA antagonizes the radiation-induced suppression on MnSOD and catalase, key enzymes of the radical scavenging systems. By significantly up-regulating catalase levels over the entire range of doses from 0.5 to 4 Gy, the inhibitor of Hsp90 exerted adaptive protection and modified the early radiation response of the human blood cells.

Therapeutic Implications for Overcoming Radiation Resistance in Cancer Therapy

Ionizing radiation (IR), such as X-rays and gamma (γ)-rays, mediates various forms of cancer cell death such as apoptosis, necrosis, autophagy, mitotic catastrophe, and senescence. Among them, apoptosis and mitotic catastrophe are the main mechanisms of IR action. DNA damage and genomic instability contribute to IR-induced cancer cell death. Although IR therapy may be curative in a number of cancer types, the resistance of cancer cells to radiation remains a major therapeutic problem. In this review, we describe the morphological and molecular aspects of various IR-induced types of cell death. We also discuss cytogenetic variations representative of IR-induced DNA damage and genomic instability. Most importantly, we focus on several pathways and their associated marker proteins responsible for cancer resistance and its therapeutic implications in terms of cancer cell death of various types and characteristics. Finally, we propose radiation-sensitization strategies, such as the modification of fractionation, inflammation, and hypoxia and the combined treatment, that can counteract the resistance of tumors to IR.

The ubiquitin ligase CHIP inactivates NF-κB signaling and impairs the ability of migration and invasion in gastric cancer cells

Ubiquitin modification of proteins influences cellular processes related to carcinogenesis. The carboxyl terminus of Hsc-70-interacting protein (CHIP), as U-box-type ubiquitin ligase, induces ubiquitination and proteasome-mediated degradation of its substrate proteins. In this study, the role of CHIP in diverse aspects of gastric cancer cells was investigated. CHIP overexpression in the AGS gastric cancer cells caused impaired tumor growth. CHIP overexpression significantly inhibited the migration and invasion of the AGS cells. Moreover, we found that not only RelA/p65 but also RelB, the NF-κB subunits, was negatively regulated by CHIP, likely owing to the TRAF2 reduction. Downregulated target genes of NF-κB subunits, including MMP-2 and -9, integrin β-1 and Bcl-2 were involved in these processes. We also showed that the expression level of CHIP was frequently decreased in gastric cancer tissues and the low level of CHIP expression might be an indicator of an unfavorable prognosis. Taken together, these observations provide functional evidence for CHIP behaviors as a tumor suppressor in gastric cancer.

Molecular signatures in the prevention of radiation damage by the synergistic effect of N-acetyl cysteine and qingre liyan decoction, a traditional chinese medicine, using a 3-dimensional cell culture model of oral mucositis

Qingre Liyan decoction (QYD), a Traditional Chinese medicine, and N-acetyl cysteine (NAC) have been used to prevent radiation induced mucositis. This work evaluates the protective mechanisms of QYD, NAC, and their combination (NAC-QYD) at the cellular and transcriptional level. A validated organotypic model of oral mucosal consisting of a three-dimensional (3D) cell tissue-culture of primary human keratinocytes exposed to X-ray irradiation was used. Six hours after the irradiation, the tissues were evaluated by hematoxylin and eosin (H and E) and a TUNEL assay to assess histopathology and apoptosis, respectively. Total RNA was extracted and used for microarray gene expression profiling. The tissue-cultures treated with NAC-QYD preserved their integrity and showed no apoptosis. Microarray results revealed that the NAC-QYD caused the upregulation of genes encoding metallothioneins, HMOX1, and other components of the Nrf2 pathway, which protects against oxidative stress. DNA repair genes (XCP, GADD45G, RAD9, and XRCC1), protective genes (EGFR and PPARD), and genes of the NFκB pathway were upregulated. Finally, tissue-cultures treated prophylactically with NAC-QYD showed significant downregulation of apoptosis, cytokines and chemokines genes, and constrained damage-associated molecular patterns (DAMPs). NAC-QYD treatment involves the protective effect of Nrf2, NFκB, and DNA repair factors.

Blockage of RelB expression by gene silencing enhances the radiosensitivity of androgen‑independent prostate cancer cells

Levels of the nuclear factor‑kappa B (NF‑κB) alternative pathway member RelB have been shown to correlate with the effect of radiation therapy in prostate cancer. RelB expression was evaluated by immunohistochemistry in normal prostate, benign prostate hyperplasia and prostate cancer specimens. RM‑1 cells were pretreated with RelB siRNA prior to radiation therapy, and RelB expression in cytoplasmic and nuclear extracts was detected by real‑time polymerase chain reaction and western blot analysis. The apoptotic rates of experimental RM‑1 cell groups were assessed by flow cytometry. A clonogenic growth array was used to evaluate the radiosensitivity of RM‑1 cell groups. The NF‑κB family member RelB was expressed at a high level in prostate cancer specimens. Compared with irradiated control cells, RM‑1 cells transfected with RelB siRNA and treated with radiation therapy demonstrated a significant downregulation of RelB expression in the cytoplasm and nucleus. Notably, flow cytometry revealed that pretreatment of RM‑1 cells with RelB siRNA enhanced the apoptotic rate in response to radiation therapy compared with controls. Clonogenic growth assay results revealed enhanced radiosensitivity of RelB siRNA cells at various dosage points compared with control groups. Blockage of the alternative NF‑κB pathway via RelB silencing is a promising approach to enhance the radiosensitivity of prostate cancer.

The RelB alternative NF-kappaB subunit promotes autophagy in 22Rv1 prostate cancer cells in vitro and affects mouse xenograft tumor growth in vivo

Background

The involvement of NF-κB signaling in prostate cancer (PCa) has largely been established through the study of the classical p65 subunit. Nuclear localization of p65 in PCa patient tissues has been shown to correlate with biochemical recurrence, while in vitro studies have demonstrated that the classical NF-κB signaling pathway promotes PCa progression and metastatic potential. More recently, the nuclear location of RelB, a member of the alternative NF-κB signaling, has also been shown to correlate with the Gleason score. The current study aims to clarify the role of alternative NF-κB in PCa cells by exploring, in vitro and in vivo, the effects of RelB overexpression on PCa biology.

Methods

Using a lentivirus-expression system, we constitutively overexpressed RelB or control GFP into 22Rv1 cells and monitored alternative transcriptional NF-κB activity. In vivo, tumor growth was assessed after the injection of 22Rv1-derived cells into SCID mice. In vitro, the impact of RelB on 22Rv1 cell proliferation was evaluated in monolayer culture. The anchorage-independent cell growth of derived-22Rv1 cells was assessed by soft agar assay. Apoptosis and autophagy were evaluated by Western blot analysis in 22Rv1-derived cells cultured in suspension using poly-HEMA pre-coated dishes.

Results

The overexpression of RelB in 22Rv1 cells induced the constitutive activation of the alternative NF-κB pathway. In vivo, RelB expression caused a lag in the initiation of 22Rv1-induced tumors in SCID mice. In vitro, RelB stimulated the proliferation of 22Rv1 cells and reduced their ability to grow in soft agar. These observations may be reconciled by our findings that, when cultured in suspension on poly-HEMA pre-coated dishes, 22Rv1 cells expressing RelB were more susceptible to cell death, and more specifically to autophagy controlled death.

Conclusions

This study highlights a role of the alternative NF-κB pathway in proliferation and the controlled autophagy. Thus, the interplay of these properties may contribute to tumor survival in stress conditions while promoting PCa cells growth contributing to the overall tumorigenicity of these cells.

Loss of p27 upregulates MnSOD in a STAT3-dependent manner, disrupts intracellular redox activity and enhances cell migration

Cell migration is a dynamic process that is central to a variety of physiological functions as well as disease pathogenesis. The modulation of cell migration by p27 (officially known as CDKN1B) has been reported, but the exact mechanism(s) whereby p27 interacts with downstream effectors that control cell migration have not been elucidated. By systematically comparing p27(+/+) mouse embryonic fibroblasts (MEFs) with genetically ablated p27(-/-) MEFs using wound-healing, transwell and time-lapse microscopic analyses, we provide direct evidence that p27 inhibits both directional and random cell migration. Identical results were obtained with normal and cancer epithelial cells using complementary knockdown and overexpression approaches. Additional studies revealed that overexpression of manganese superoxide dismutase (MnSOD, officially known as SOD2) and reduced intracellular oxidation played a key role in increased cell migration in p27-deficient cells. Furthermore, we identified signal transducer and activator of transcription 3 (STAT3) as the transcription factor responsible for p27-regulated MnSOD expression, which was further mediated by ERK- and ATF1-dependent transactivation of the cAMP response element (CRE) within the Stat3 promoter. Collectively, our data strongly indicate that p27 plays a crucial negative role in cell migration by inhibiting MnSOD expression in a STAT3-dependent manner.

Redox-modulated phenomena and radiation therapy: the central role of superoxide dismutases

SIGNIFICANCE

Ionizing radiation is a vital component in the oncologist's arsenal for the treatment of cancer. Approximately 50% of all cancer patients will receive some form of radiation therapy as part of their treatment regimen. DNA is considered the major cellular target of ionizing radiation and can be damaged directly by radiation or indirectly through reactive oxygen species (ROS) formed from the radiolysis of water, enzyme-mediated ROS production, and ROS resulting from altered aerobic metabolism.

RECENT ADVANCES

ROS are produced as a byproduct of oxygen metabolism, and superoxide dismutases (SODs) are the chief scavengers. ROS contribute to the radioresponsiveness of normal and tumor tissues, and SODs modulate the radioresponsiveness of tissues, thus affecting the efficacy of radiotherapy.

CRITICAL ISSUES

Despite its prevalent use, radiation therapy suffers from certain limitations that diminish its effectiveness, including tumor hypoxia and normal tissue damage. Oxygen is important for the stabilization of radiation-induced DNA damage, and tumor hypoxia dramatically decreases radiation efficacy. Therefore, auxiliary therapies are needed to increase the effectiveness of radiation therapy against tumor tissues while minimizing normal tissue injury.

FUTURE DIRECTIONS

Because of the importance of ROS in the response of normal and cancer tissues to ionizing radiation, methods that differentially modulate the ROS scavenging ability of cells may prove to be an important method to increase the radiation response in cancer tissues and simultaneously mitigate the damaging effects of ionizing radiation on normal tissues. Altering the expression or activity of SODs may prove valuable in maximizing the overall effectiveness of ionizing radiation.

MnSOD in oxidative stress response-potential regulation via mitochondrial protein influx

SIGNIFICANCE

The mitochondrial antioxidant manganese superoxide dismutase (MnSOD) is encoded by genomic DNA and its dismutase function is fully activated in the mitochondria to detoxify free radical O2(•-) generated by mitochondrial respiration. Accumulating evidence shows an extensive communication between the mitochondria and cytoplasm under oxidative stress. Not only is the MnSOD gene upregulated by oxidative stress, but MnSOD activity can be enhanced via the mitochondrial protein influx (MPI).

RECENT ADVANCES

A cluster of MPI containing cytoplasmic/nuclear proteins, such as cyclins, cyclin-dependent kinases, and p53 interact with and alter MnSOD activity. These proteins modulate MnSOD superoxide scavenging activity via post-translational modifications in the mitochondria. In addition to well-established pathways in gene expression, recent findings suggest that MnSOD enzymatic activity can also be enhanced by phosphorylation of specific motifs in mitochondria. This review attempts to discuss the pre- and post-translational regulation of MnSOD, and how these modifications alter MnSOD activity, which induces a cell adaptive response to oxidative stress.

CRITICAL ISSUES

MnSOD is biologically significant to aerobic cells. Its role in protecting the cells against the deleterious effects of reactive oxygen species is evident. However, the exact network of MnSOD-associated cellular adaptive reaction to oxidative stress and its post-translational modifications, especially its enzymatic enhancement via phosphorylation, is not yet fully understood.

FUTURE DIRECTIONS

The broad discussion of the multiple aspects of MnSOD regulation, including gene expression, protein modifications, and enzymatic activity, will shed light onto the unknown mechanisms that govern the prosurvival networks involved in cellular and mitochondrial adaptive response to genotoxic environment.

Superoxide mediates acute liver injury in irradiated mice lacking sirtuin 3

AIMS

This study determined whether acute radiation-induced liver injury seen in Sirtuin3(-/-) mice after exposure to Cs-137 γ-rays was mediated by superoxide anion (O2(•-)).

RESULTS

Male wild-type (WT) and SIRT3(-/-) mice were given 2×2 Gy whole-body radiation doses separated by 24 h and livers were harvested 20 h after the second dose. Ex vivo measurements in fresh frozen liver sections demonstrated 50% increases in dihydroethidium oxidation from SIRT3(-/-) animals, relative to WT animals, before irradiation, but this increase was not detected 20 h after radiation exposure. In addition, irradiated livers from SIRT3(-/-) animals showed significant hydropic degeneration, loss of MitoTracker Green FM staining, increased immunohistochemical staining for 3-nitrotyrosine, loss of Ki67 staining, and increased mitochondrial localization of p53. These parameters of radiation-induced injury were significantly attenuated by an intraperitoneal injection of 2 mg/kg of the highly specific superoxide dismutase mimic, GC4401, 30 min before each fraction.

INNOVATION

Sirtuin 3 (SIRT3) is believed to regulate mitochondrial oxidative metabolism and antioxidant defenses in response to acute radiation-induced liver injury. This work provides strong evidence for the causal role of O2(•-) in the liver injury process initiated by whole-body irradiation in SIRT3(-/-) mice.

CONCLUSION

These results support the hypothesis that O2(•-) mediates acute liver injury in SIRT3(-/-) animals exposed to whole-body γ-radiation and suggest that GC4401 could be used as a radio-protective compound in vivo.

Redox-mediated and ionizing-radiation-induced inflammatory mediators in prostate cancer development and treatment

SIGNIFICANCE

Radiation therapy is widely used for treatment of prostate cancer. Radiation can directly damage biologically important molecules; however, most effects of radiation-mediated cell killing are derived from the generated free radicals that alter cellular redox status. Multiple proinflammatory mediators can also influence redox status in irradiated cells and the surrounding microenvironment, thereby affecting prostate cancer progression and radiotherapy efficiency.

RECENT ADVANCES

Ionizing radiation (IR)-generated oxidative stress can regulate and be regulated by the production of proinflammatory mediators. Depending on the type and stage of the prostate cancer cells, these proinflammatory mediators may lead to different biological consequences ranging from cell death to development of radioresistance.

CRITICAL ISSUES

Tumors are heterogeneous and dynamic communication occurs between stromal and prostate cancer cells, and complicated redox-regulated mechanisms exist in the tumor microenvironment. Thus, antioxidant and anti-inflammatory strategies should be carefully evaluated for each patient at different stages of the disease to maximize therapeutic benefits while minimizing unintended side effects.

FUTURE DIRECTIONS

Compared with normal cells, tumor cells are usually under higher oxidative stress and secrete more proinflammatory mediators. Thus, redox status is often less adaptive in tumor cells than in their normal counterparts. This difference can be exploited in a search for new cancer therapeutics and treatment regimes that selectively activate cell death pathways in tumor cells with minimal unintended consequences in terms of chemo- and radio-resistance in tumor cells and toxicity in normal tissues.

RelB regulates Bcl-xl expression and the irradiation-induced apoptosis of murine prostate cancer cells

Apoptosis in prostate cancer (PCa) induced by ionizing radiation (IR) is believed to play a critical role in radioresistance. Bcl-xl, an important member of the anti-apoptotic Bcl-2 family, has critical roles in tumor progression and development. The aim of the present study was to investigate the association of Bcl-xl expression and radiosensitivity from murine PCa RM-1 cells. An adenovirus-mediated RNA interference technique was employed to inhibit the expression of the RelB gene. RelB proteins were detected upon irradiation following transfection with small interfering (si)RelB, as shown by western blot analysis. The radiosensitivity of the RM-1 cells was determined by clonogenic assays. The apoptosis of the RM-1 cells were detected by flow cytometry assay, then quantitative polymerase chain reaction assays were performed to determine the expression level of Bcl-xl mRNA in the RM-1 cells. Radiation treatment increased the RelB protein levels from the cytosol and nucleus in the RM-1 cells. The protein expression levels of RelB in the pLentilox-sh-RelB-transfected RM-1 cells were significantly lower than in the negative interference group following radiation treatment. The percentage of cells undergoing apoptosis in the siRelB-RM-1 group was significantly higher than that in the control group following radiation treatment. Finally, a positive link between Bcl-xl expression and RelB activity was established in the RM-1 cells. Inhibition of RelB correlates with a decrease in expression of Bcl-xl. In conclusion, adenovirus-mediated siRNA targeting RelB inhibits Bcl-xl expression, enhances radiosensitivity and regulates the irradiation-induced apoptosis of the murine PCa RM-1 cell line.

RelB, together with RelA, sustains cell survival and confers proteasome inhibitor sensitivity of chronic lymphocytic leukemia cells from bone marrow

Although the biological factors that contribute to the pathogenesis of chronic lymphocytic leukemia (CLL) remain widely unresolved, it has been suggested that dysregulated cell survival and proliferation are fundamental to this process. Constitutive classical nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation protects CLL B-cells from cell death and plays a critical role in the acquisition of chemoresistance. RelB, representing the alternative NF-κB activity, functions specifically in lymphoid organogenesis and B-cell maturation. RelB indeed plays a tumor-supportive role and confers radiation resistance in tumors. However, the involvement of RelB in CLL has not been addressed. Here, we analyzed the NF-κB activation in 67 of CLL bone marrow (BM). Both the RelA and RelB activity were detected in CLL B-cells from BM, in spite of inevitable variability. Low RelB activity was linked to a favorable prognosis of CLL. The migration and adhesion abilities of CLL B-cells were not affected by the RelB activity. High RelB activity, together with the RelA activity, maintained basal survival of cells. The induction of RelA and RelB expression in the nucleus was responsible for better survival of CLL B-cells supported by bone marrow stromal cells. In addition, the presence of high RelB activity in CLL B-cells was correlated with sensitivity to proteasome inhibitor but not fludarabine. Taken together, we provided evidences that not only RelA but also RelB, subunits of NF-κB family, played an important role in the cellular behaviors of CLL cells from BM. The strength of RelB activity influenced the prognosis of CLL patients.

KEY MESSAGE

RelB, with RelA activity, maintained the basal survival of CLL cells from BM. RelB, with RelA, conferred the proteasome inhibitor sensitivity of CLL cells. Induction of RelA and RelB was responsible for the better survival of CLL B-cells. The strength of RelB activity influenced the prognosis of CLL patients.

Oxidative stress due to radiation in CD34(+) hematopoietic progenitor cells: protection by IGF-1

Radiation exerts direct as well as indirect effects on DNA through the generation of reactive oxygen species (ROS). Irradiated hematopoietic progenitor cells (HPCs) experience DNA strand breaks, favoring genetic instability, due to ROS generation. Our aim was to study the effect of a range of radiation doses in HPCs and the possible protective mechanisms activated by insulin-like growth factor-1 (IGF-1). ROS generation was evaluated, in the presence or absence of IGF-1 in liquid cultures of human HPCs-CD34(+) irradiated with 1-, 2- and 5-Gy X-rays, using a flow cytometry assay. Manganese superoxide dismutase (MnSOD) expression was studied by western blot analysis and visualized by an immunofluorescence assay. Apoptosis was estimated using the following assays: Annexin-V assay, DNA degradation assay, BCL-2/BAX mRNA and protein levels and caspase-9 protein immunofluorescence visualization. Viability and clonogenic potential were studied in irradiated HPCs. The generation of superoxide anion radicals at an early and a late time point was increased, while the hydrogen peroxide generation at a late time point was stable. IGF-1 presence further enhanced the radiation-induced increase of MnSOD at 24 h post irradiation. IGF-1 inhibited the mitochondria-mediated pathway of apoptosis by regulating the m-RNA and protein expression of BAX, BCL-2 and the BCL-2/BAX ratio and by decreasing caspase-9 protein expression. IGF-1 presence in culture media of irradiated cells restored the clonogenic capacity and the viability of HPCs as well. In conclusion, IGF-1 protects HPCs-CD34(+) from radiation effects, by eliminating the oxidative microenvironment through the enhancement of MnSOD activation and by regulating the mitochondria-mediated pathway of apoptosis.

NF-κB signaling pathways: role in nervous system physiology and pathology

Intracellular pathways related to cell survival regulate neuronal physiology during development and neurodegenerative disorders. One of the pathways that have recently emerged with an important role in these processes is nuclear factor-κB (NF-κB). The activity of this pathway leads to the nuclear translocation of the NF-κB transcription factors and the regulation of anti-apoptotic gene expression. Different stimuli can activate the pathway through different intracellular cascades (canonical, non-canonical, and atypical), contributing to the translocation of specific dimers of the NF-κB transcription factors, and each of these dimers can regulate the transcription of different genes. Recent studies have shown that the activation of this pathway regulates opposite responses such as cell survival or neuronal degeneration. These apparent contradictory effects depend on conditions such as the pathway stimuli, the origin of the cells, or the cellular context. In the present review, the authors summarize these findings and discuss their significance with respect to survival or death in the nervous system.

Effects of cyclohexanone analogues of curcumin on growth, apoptosis and NF-κB activity in PC-3 human prostate cancer cells

Curcumin is a non-nutritive yellow pigment found in the spice turmeric, which is derived from the rhizome of the plant Curcuma longa Linn. Six cyclohexanone analogues of curcumin (A(1)-A(6)) were investigated for their effects on growth and apoptosis in PC-3 human prostate cancer cells. The ability of these compounds to inhibit NF-κB activity in PC-3 cells was also determined. Five out of the six curcumin analogues (A(2)-A(6)) had stronger inhibitory effects compared to curcumin on the growth of cultured PC-3 cells. Compounds A(2)-A(6) also had stronger stimulatory effects on apoptosis in PC-3 cells than curcumin, and these curcumin analogues more potently inhibited NF-κB activity than curcumin. The inhibitory effects of these compounds on NF-κB activity correlated with their effects on growth inhibition and apoptosis stimulation in PC-3 cells. The results of the present study provide a rationale for in vivo studies with A(2)-A(6) using suitable animal models of prostate cancer.