NFkappaB signaling related molecular alterations in human neuroblastoma cells after fractionated irradiation

Anticarcinogenic Potency of EF24: An Overview of Its Pharmacokinetics, Efficacy, Mechanism of Action, and Nanoformulation for Drug Delivery

EF24, a synthetic monocarbonyl analog of curcumin, shows significant potential as an anticancer agent with both chemopreventive and chemotherapeutic properties. It exhibits rapid absorption, extensive tissue distribution, and efficient metabolism, ensuring optimal bioavailability and sustained exposure of the target tissues. The ability of EF24 to penetrate biological barriers and accumulate at tumor sites makes it advantageous for effective cancer treatment. Studies have demonstrated EF24's remarkable efficacy against various cancers, including breast, lung, prostate, colon, and pancreatic cancer. The unique mechanism of action of EF24 involves modulation of the nuclear factor-kappa B (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways, disrupting cancer-promoting inflammation and oxidative stress. EF24 inhibits tumor growth by inducing cell cycle arrest and apoptosis, mainly through inhibiting the NF-κB pathway and by regulating key genes by modulating microRNA (miRNA) expression or the proteasomal pathway. In summary, EF24 is a promising anticancer compound with a unique mechanism of action that makes it effective against various cancers. Its ability to enhance the effects of conventional therapies, coupled with improvements in drug delivery systems, could make it a valuable asset in cancer treatment. However, addressing its solubility and stability challenges will be crucial for its successful clinical application.

MMP-9 reinforces radiation-induced delayed invasion and metastasis of neuroblastoma cells through second-signaling positive feedback with NFκB via both ERK and IKK activation

Neuroblastoma (NB) progression is branded with hematogenous metastasis and frequent relapses. Despite intensive multimodal clinical therapy, outcomes for patients with progressive disease remain poor, with negligible long-term survival. Therefore, understanding the acquired molecular rearrangements in NB cells with therapy pressure and developing improved therapeutic strategies is a critical need to improve the outcomes for high-risk NB patients. We investigated the rearrangement of MMP9 in NB with therapy pressure, and unveiled the signaling that facilitates NB evolution. Radiation-treatment (RT) significantly increased MMP9 expression/activity, and the induced enzyme activity was persistently maintained across NB cell lines. Furthermore, RT-triggered NFκB transcriptional activity and this RT-induced NFκB were required/adequate for MMP9 maintenance. RT-triggered NFκB-dependent MMP9 actuated a second-signaling feedback to NFκB, facilitating a NFκB-MMP9-NFκB positive feedback cycle (PFC). Critically, MMP9-NFκB feedback is mediated by MMP9-dependent activation of IKKβ and ERK phosphotransferase activity. Beyond its tumor invasion/metastasis function, PFC-dependent MMP9 lessens RT-induced apoptosis and favors survival pathway through the activation of NFκB signaling. In addition, PFC-dependent MMP9 regulates 19 critical molecular determinants that play a pivotal role in tumor evolution. Interestingly, seven of 19 genes possess NFκB-binding sites, demonstrating that MMP9 regulates these molecules by activating NFκB. Collectively, these data suggest that RT-triggered NFκB-dependent MMP9 actuates feedback to NFκB though IKKβ- and ERK1/2-dependent IκBα phosphorylation. This RT-triggered PFC prompts MMP9-dependent survival advantage, tumor growth, and dissemination. Targeting therapy-pressure-driven PFC and/or selective inhibition of MMP9 maintenance could serve as promising therapeutic strategies for treatment of progressive NB.

Long Noncoding RNA LINC01410 Suppresses Tumorigenesis and Enhances Radiosensitivity in Neuroblastoma Cells Through Regulating miR-545-3p/HK2 Axis

Background

Abnormal expression of long noncoding RNAs (lncRNAs) was often involved in tumorigenesis and radiosensitivity of various cancers. The aim of this study was to explore the biological function and regulatory mechanism of lncRNA long intergenic non-protein coding RNA 1410 (LINC01410) in tumorigenesis and radiosensitivity of neuroblastoma (NB).

Methods

The expression of LINC01410, microRNA-329-3p (miR-545-3p) and hexokinase 2 (HK2) was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Methylthiazolyldiphenyl tetrazolium bromide (MTT) assay, colony formation assay and transwell assay were utilized to detect cell viability, colony formation and cell invasion abilities. Glucose consumption or lactate production was measured by glucose assay kit or lactate assay kit, respectively. The interaction between miR-545-3p and LINC01410 or HK2 was predicted by starBase v2.0 and verified by dual-luciferase reporter, RNA Immunoprecipitation (RIP) and RNA pull-down assays. Western blot was used to measure the protein expression of HK2. The mice xenograft model was established to investigate the role of LINC01410 in vivo.

Results

LINC01410 and HK2 were highly expressed while miR-545-3p was lowly expressed in NB tissues and cells. LINC01410 knockdown inhibited tumorigenesis by repressing cell proliferation and invasion, and increased the radiosensitivity via inhibiting colony formation rates and glycolysis. LINC01410 knockdown also suppressed tumor growth in vivo. Moreover, miR-545-3p could bind to LINC01410 and its downregulation reversed the effects of LINC01410 knockdown on tumorigenesis and radiosensitivity. Additionally, HK2 was a direct target of miR-545-3p and its overexpression attenuated the effects of miR-545-3p restoration on suppression of tumorigenesis and promotion of radiosensitivity. Besides, LINC01410 functioned as a molecular sponge of miR-545-3p to regulate HK2 expression.

Conclusion

LINC01410 interference inhibited tumorigenesis and increased radiosensitivity via regulating miR-545-3p/HK2 axis, providing a novel therapeutic strategy for NB.

Differences in sustained alterations in protein expression between livers of mice exposed to high-dose-rate and low-dose-rate radiation

Molecular mechanisms of radiation dose-rate effects are not well understood. Among many possibilities, long-lasting sustained alterations in protein levels would provide critical information. To evaluate sustained effects after acute and chronic radiation exposure, we analyzed alterations in protein expression in the livers of mice. Acute exposure consisted of a lethal dose of 8 Gy and a sublethal dose of 4 Gy, with analysis conducted 6 days and 3 months after irradiation, respectively. Chronic irradiation consisted of a total dose of 8 Gy delivered over 400 days (20 mGy/day). Analyses following chronic irradiation were done immediately and at 3 months after the end of the exposure. Based on antibody arrays of protein expression following both acute lethal and sublethal dose exposures, common alterations in the expression of two proteins were detected. In the sublethal dose exposure, the expression of additional proteins was altered 3 months after irradiation. Immunohistochemical analysis showed that the increase in one of the two commonly altered proteins, MyD88, was observed around blood vessels in the liver. The alterations in protein expression after chronic radiation exposure were different from those caused by acute radiation exposures. Alterations in the expression of proteins related to inflammation and apoptosis, such as caspase 12, were observed even at 3 months after the end of the chronic radiation exposure. The alterations in protein expression depended on the dose, the dose rate, and the passage of time after irradiation. These changes could be involved in long-term effects of radiation in the liver.

Inhibition of NF-κB Activity Enhances Sensitivity to Anticancer Drugs in Cholangiocarcinoma Cells

Cholangiocarcinoma (CCA) is a dismal cancer. At present, there is no effective chemotherapeutic regimen for CCA. This may be due to the marked resistance of CCA to chemotherapy drugs, for which a mechanism remains unknown. Nuclear factor-κB (NF-κB) is constitutively activated in a variety of cancer cells, including CCA. It has been shown to play roles in growth, metastasis, and chemoresistance of cancer. In the present study, we examined whether NF-κB is involved in the chemoresistance of CCA and whether dehydroxymethylepoxyquinomicin (DHMEQ), an effective NF-κB inhibitor, can overcome the drug resistance of CCA. Two CCA cell lines, KKU-M213 and KKU-M214, were treated with DHMEQ and/or chemotherapeutic drugs. Cell viability, apoptosis, and the expressions of the ATP-binding cassette (ABC) transporters were compared. The combination of chemotherapy drugs, 5-fluorouracil, cisplatin, and doxorubicin, with DHMEQ significantly enhanced the cytotoxicity of all chemotherapeutic drugs compared to DHMEQ or drug alone. Furthermore, the mRNA level of ABCB1, a multidrug-resistant protein, was significantly decreased in the 5-fluorouracil combined with DHMEQ-treated cells. These findings suggest that the inhibition of NF-κB by DHMEQ enhanced the chemoresponsiveness of CCA cells, possibly by reducing the expression of ABC transporter. Inhibition of NF-κB may be a potential chemodrug-sensitizing strategy for chemoresistant cancer such as CCA.

Novel adjuvants from seaweed impede autophagy signaling in therapy-resistant residual pancreatic cancer

BACKGROUND

Identifying the drug-deliverables that target autophagy is crucial to finding a cure for pancreatic cancer (PC), as activated autophagy is associated with poor patient outcomes. Our recent studies recognized the anti-PC potential of an antioxidant-rich collection of seaweed polyphenols and identified potential compounds for the treatment of PC. Accordingly, we investigated whether such compounds could regulate autophagy in therapy-resistant PC cells in vitro and in residual PC in vivo.

RESULTS

Human Panc-3.27 and MiaPaCa-2 cells were exposed to fractionated irradiation (FIR) with/without ethyl acetate (EA) polyphenol from Spatoglossum asperum (SA-EA), Padina tetrastromatica (PT-EA), or Hormophysa triquerta (HT-EA). The cells were subjected to QPCR to examine transcriptional alterations in the following autophagy functional regulators: ATG3, ATG5, ATG7, ATG12, LC3A, LC3B, Beclin, Myd88, HMGB1, Rage, and TLRs 1-9. Using a clinically relevant mouse model of residual PC, we use tissue microarray (TMA) and immunohistochemistry (IHC) procedures to investigate the potential of polyphenol(s) to target ATG3, ATG5, ATG12, LC3A, LC3B, BECN1, and SURIVIN after clinical radiotherapy. Radiation significantly increased the transcription of autophagy functional regulators in both cell lines. Seaweed polyphenols completely suppressed the transcription of all investigated autophagy regulators in both cell-lines. Gene silencing approach defined the role of LC3B in radiation-induced cell survival in this setting. TMA-IHC analysis revealed the complete regulation of ATG3, ATG5, ATG12, LC3A, LC3B, BECN1, and SURVIVIN in residual PC following SA-EA, PT-EA, and HT-EA treatment.

CONCLUSIONS

These data demonstrate the autophagy blue print in therapy-resistant PC cells for the first time. Moreover, the data strongly suggest that the selected polyphenols could serve as effective adjuvants for current PC treatment modalities and may inhibit tumor relapse by comprehensively targeting therapy-orchestrated autophagy in residual cells.

Photon and carbon ion irradiation of a rat prostate carcinoma: does a higher fraction number increase the metastatic rate?

In a recent published study, we investigated the response of an experimental prostate carcinoma (R3327-AT1) after irradiation with 1, 2 or 6 fractions of carbon ions or photons, respectively. The original intention of this study was to measure the dose-dependent local control probability as well as the related relative biological effectiveness of carbon ions. However, we now report an increased metastatic rate when the number of fractions was increased from 2 to 6. In a total of 246 animals, the actuarial metastatic rates for 1, 2 and 6 fractions were 5.1 ± 3.5%, 5.7 ± 4.0% and 15.3 ± 7.1% for photons and 9.8 ± 7.5%, 4.0 ± 3.9% and 20.3 ± 6.5% for carbon ions, respectively. The increase was significant only for carbon ions (6 vs. 2 fractions,P = 0.03). Although the original experiment was not designed to investigate metastatic rates, this observation may be of general interest to researchers studying radiation-modulated metastatic activity.

Acquired tumor cell radiation resistance at the treatment site is mediated through radiation-orchestrated intercellular communication

PURPOSE

Radiation resistance induced in cancer cells that survive after radiation therapy (RT) could be associated with increased radiation protection, limiting the therapeutic benefit of radiation. Herein we investigated the sequential mechanistic molecular orchestration involved in radiation-induced radiation protection in tumor cells.

RESULTS

Radiation, both in the low-dose irradiation (LDIR) range (10, 50, or 100 cGy) or at a higher, challenge dose IR (CDIR), 4 Gy, induced dose-dependent and sustained NFκB-DNA binding activity. However, a robust and consistent increase was seen in CDIR-induced NFκB activity, decreased DNA fragmentation, apoptosis, and cytotoxicity and attenuation of CDIR-inhibited clonal expansion when the cells were primed with LDIR prior to challenge dose. Furthermore, NFκB manipulation studies with small interfering RNA (siRNA) silencing or p50/p65 overexpression unveiled the influence of LDIR-activated NFκB in regulating CDIR-induced DNA fragmentation and apoptosis. LDIR significantly increased the transactivation/translation of the radiation-responsive factors tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α), cMYC, and SOD2. Coculture experiments exhibit LDIR-influenced radiation protection and increases in cellular expression, secretion, and activation of radiation-responsive molecules in bystander cells. Individual gene-silencing approach with siRNAs coupled with coculture studies showed the influence of LDIR-modulated TNF-α, IL-1α, cMYC, and SOD2 in induced radiation protection in bystander cells. NFκB inhibition/overexpression studies coupled with coculture experiments demonstrated that TNF-α, IL-1α, cMYC, and SOD2 are selectively regulated by LDIR-induced NFκB.

CONCLUSIONS

Together, these data strongly suggest that scattered LDIR-induced NFκB-dependent TNF-α, IL-1α, cMYC, and SOD2 mediate radiation protection to the subsequent challenge dose in tumor cells.

Novel synthetic monoketone transmute radiation-triggered NFκB-dependent TNFα cross-signaling feedback maintained NFκB and favors neuroblastoma regression

Recently, we demonstrated that radiation (IR) instigates the occurrence of a NFκB-TNFα feedback cycle which sustains persistent NFκB activation in neuroblastoma (NB) cells and favors survival advantage and clonal expansion. Further, we reported that curcumin targets IR-induced survival signaling and NFκB dependent hTERT mediated clonal expansion in human NB cells. Herein, we investigated the efficacy of a novel synthetic monoketone, EF24, a curcumin analog in inhibiting persistent NFκB activation by disrupting the IR-induced NFκB-TNFα-NFκB feedback signaling in NB and subsequent mitigation of survival advantage and clonal expansion. EF24 profoundly suppressed the IR-induced NFκB-DNA binding activity/promoter activation and, maintained the NFκB repression by deterring NFκB-dependent TNFα transactivation/intercellular secretion in genetically varied human NB (SH-SY5Y, IMR-32, SK-PN-DW, MC-IXC and SK-N-MC) cell types. Further, EF24 completely suppressed IR-induced NFκB-TNFα cross-signaling dependent transactivation/translation of pro-survival IAP1, IAP2 and Survivin and subsequent cell survival. In corroboration, EF24 treatment maximally blocked IR-induced NFκB dependent hTERT transactivation/promoter activation, telomerase activation and consequent clonal expansion. EF24 displayed significant regulation of IR-induced feedback dependent NFκB and NFκB mediated survival signaling and complete regression of NB xenograft. Together, the results demonstrate for the first time that, novel synthetic monoketone EF24 potentiates radiotherapy and mitigates NB progression by selectively targeting IR-triggered NFκB-dependent TNFα-NFκB cross-signaling maintained NFκB mediated survival advantage and clonal expansion.

Radiation-induced TNFα cross signaling-dependent nuclear import of NFκB favors metastasis in neuroblastoma

Ascertaining function-specific orchestration of NFκB in response to radiation may reveal a molecular blue-print that dictates induced relapse and metastasis of the neuroblastoma. We recently demonstrated that sustained activation of NFκB caused by ionizing radiation (IR)-initiated TNFα-NFκB feedback signaling leads to radioresistance and recurrence of neuroblastoma. We investigated whether muting IR-triggered or TNFα-dependent second-signaling feedback-dependent NFκB nuclear import results in limiting IR-altered invasion and metastasis. Neuroblastoma cells were exposed to 2 Gy and incubated for 1 h or 24 h. The cells were then treated with an NFκB-targeting peptide blocker, SN50. Upon confirming the blockade in DNA-binding activity, transcription driven transactivation of NFκB and secretion of soluble TNFα, transcriptional alterations of 93 tumor invasion/metastasis genes were assessed by using QPCR profiling and then were selectively validated at the protein level. Exposure to 2 Gy induced 63, 42 and 71 genes in surviving SH-SY5Y, IMR-32 and SK-N-MC cells, respectively. Blocking post-translational nuclear import of NFκB comprehensively inhibited both initial activation of genes (62/63, 34/42 and 65/71) triggered by IR and also TNFα-mediated second signaling-dependent sustained (59/63, 32/42 and 71/71) activation of tumor invasion and metastasis signaling molecules. Furthermore, alterations in the proteins MMP9, MMP2, PYK-2, SPA-1, Dnmt3b, Ask-1, CTGF, MMP10, MTA-2, NF-2, E-Cadherin, TIMP-2 and ADAMTS1 and the results of our scratch-wound assay validate the role of post-translational NFκB in IR-regulated invasion/metastasis. These data demonstrate that IR-induced second-phase (post-translational) NFκB activation mediates TNFα-dependent second signaling and further implies that IR induced NFκB in cells that survive after treatment regulates tumor invasion/metastasis signaling.

Molecular basis of 'hypoxic' breast cancer cell radio-sensitization: phytochemicals converge on radiation induced Rel signaling

BACKGROUND

Heterogeneously distributed hypoxic areas are a characteristic property of locally advanced breast cancers (BCa) and generally associated with therapeutic resistance, metastases, and poor patient survival. About 50% of locally advanced BCa, where radiotherapy is less effective are suggested to be due to hypoxic regions. In this study, we investigated the potential of bioactive phytochemicals in radio-sensitizing hypoxic BCa cells.

METHODS

Hypoxic (O2-2.5%; N2-92.5%; CO2-5%) MCF-7 cells were exposed to 4 Gy radiation (IR) alone or after pretreatment with Curcumin (CUR), curcumin analog EF24, neem leaf extract (NLE), Genistein (GEN), Resveratrol (RES) or raspberry extract (RSE). The cells were examined for inhibition of NFκB activity, transcriptional modulation of 88 NFκB signaling pathway genes, activation and cellular localization of radio-responsive NFκB related mediators, eNos, Erk1/2, SOD2, Akt1/2/3, p50, p65, pIκBα, TNFα, Birc-1, -2, -5 and associated induction of cell death.

RESULTS

EMSA revealed that cells exposed to phytochemicals showed complete suppression of IR-induced NFκB. Relatively, cells exposed EF24 revealed a robust inhibition of IR-induced NFκB. QPCR profiling showed induced expression of 53 NFκB signaling pathway genes after IR. Conversely, 53, 50, 53, 53, 53 and 53 of IR-induced genes were inhibited with EF24, NLE, CUR, GEN, RES and RSE respectively. In addition, 25, 29, 24, 16, 11 and 21 of 35 IR-suppressed genes were further inhibited with EF24, NLE, CUR, GEN, RES and RSE respectively. Immunoblotting revealed a significant attenuating effect of IR-modulated radio-responsive eNos, Erk1/2, SOD2, Akt1/2/3, p50, p65, pIκBα, TNFα, Birc-1, -2 and -5 with EF24, NLE, CUR, GEN, RES or RSE. Annexin V-FITC staining showed a consistent and significant induction of IR-induced cell death with these phytochemicals. Notably, EF24 robustly conferred IR-induced cell death.

CONCLUSIONS

Together, these data identifies the potential hypoxic cell radio-sensitizers and further implies that the induced radio-sensitization may be exerted by selectively targeting IR-induced NFκB signaling.

Irreversible EGFR inhibitor EKB-569 targets low-LET γ-radiation-triggered rel orchestration and potentiates cell death in squamous cell carcinoma

EKB-569 (Pelitinib), an irreversible EGFR tyrosine kinase inhibitor has shown potential therapeutic efficiency in solid tumors. However, cell-killing potential in combination with radiotherapy and its underlying molecular orchestration remain to be explored. The objective of this study was to determine the effect of EKB-569 on ionizing radiation (IR)-associated NFκB-dependent cell death. SCC-4 and SCC-9 cells exposed to IR (2Gy) with and without EKB-569 treatment were analyzed for transactivation of 88 NFκB pathway molecules, NFκB DNA-binding activity, translation of the NFκB downstream mediators, Birc1, 2 and 5, cell viability, metabolic activity and apoptosis. Selective targeting of IR-induced NFκB by EKB-569 and its influence on cell-fate were assessed by overexpressing (p50/p65) and silencing (ΔIκBα) NFκB. QPCR profiling after IR exposure revealed a significant induction of 74 NFκB signal transduction molecules. Of those, 72 were suppressed with EKB-569. EMSA revealed a dose dependent inhibition of NFκB by EKB-569. More importantly, EKB-569 inhibited IR-induced NFκB in a dose-dependent manner, and this inhibition was sustained up to at least 72 h. Immunoblotting revealed a significant suppression of IR-induced Birc1, 2 and 5 by EKB-569. We observed a dose-dependent inhibition of cell viability, metabolic activity and apoptosis with EKB-569. EKB-569 significantly enhanced IR-induced cell death and apoptosis. Blocking NFκB improved IR-induced cell death. Conversely, NFκB overexpression negates EKB-569 -induced cell-killing. Together, these pre-clinical data suggest that EKB-569 is a radiosensitizer of squamous cell carcinoma and may mechanistically involve selective targeting of IR-induced NFκB-dependent survival signaling. Further pre-clinical in-vivo studies are warranted.

Impact of curcumin, raspberry extract, and neem leaf extract on rel protein-regulated cell death/radiosensitization in pancreatic cancer cells

OBJECTIVES

Nuclear factor κB (NF-κB) plays an intrinsic role in promoting growth, angiogenesis, and metastasis in pancreatic cancer (PC) and serves as a mechanism underlying therapeutic resistance. Accordingly, we investigated the efficacy of bioactive phytochemicals in inhibiting radiotherapy (RT)-induced NF-κB activity, signaling, and NF-κB-dependent regulation of cell death.

METHODS

Panc-1, BxPC-3, and MIA PaCa-2 cells exposed to 10 Gy (single high dose [SDR]) or 2 Gy/d for 5 days (fractionated radiation [FIR]) with or without curcumin (CUR), neem leaf extract (NLE), or black raspberry extract (RSE) were analyzed.

RESULTS

Radiotherapy profoundly induced NF-κB-DNA-binding activity with relatively robust activation after FIR. Curcumin, NLE, and RSE significantly inhibited both constitutive and RT-induced NF-κB. Furthermore, quantitative polymerase chain reaction profiling of 88 NF-κB pathway molecules demonstrated that CUR, NLE, and RSE comprehensively, yet differentially inhibited FIR/SDR-induced genes. Functionally, CUR, NLE, and RSE markedly conferred RT-inhibited cell viability/survival, robustly activated caspase-3/7 activity, and subsequent cell death. More importantly, NF-κB overexpression and silencing studies demonstrate that these compounds potentiate RT-induced cell death by targeting RT-induced NF-κB.

CONCLUSIONS

These data strongly imply that CUR, NLE, and RSE may serve as effective "deliverables" to potentiate RT in PC cure and further throw light that these phytochemicals-induced cell killing may involve selective regulation of RT-induced NF-κB.

Radiation-triggered tumor necrosis factor (TNF) alpha-NFkappaB cross-signaling favors survival advantage in human neuroblastoma cells

Induced radioresistance in the surviving cancer cells after radiotherapy could be associated with clonal selection leading to tumor regrowth at the treatment site. Previously we reported that post-translational modification of IκBα activates NFκB in response to ionizing radiation (IR) and plays a key role in regulating apoptotic signaling. Herein, we investigated the orchestration of NFκB after IR in human neuroblastoma. Both in vitro (SH-SY5Y, SK-N-MC, and IMR-32) and in vivo (xenograft) studies showed that IR persistently induced NFκB DNA binding activity and NFκB-dependent TNFα transactivation and secretion. Approaches including silencing NFκB transcription, blocking post-translational NFκB nuclear import, muting TNF receptor, overexpression, and physiological induction of either NFκB or TNFα precisely demonstrated the initiation and occurrence of NFκB → TNFα → NFκB positive feedback cycle after IR that leads to and sustains NFκB activation. Selective TNF-dependent NFκB regulation was confirmed with futile inhibition of AP-1 and SP-1 in TNF receptor muted cells. Moreover, IR increased both transactivation and translation of Birc1, Birc2, and Birc5 and induced metabolic activity and clonal expansion. This pathway was further defined to show that IR-induced functional p65 transcription (not NFκB1, NFκB2, or c-Rel) is necessary for activation of these survival molecules and associated survival advantage. Together, these results demonstrate for the first time the functional orchestration of NFκB in response to IR and further imply that p65-dependent survival advantage and initiation of clonal expansion may correlate with an unfavorable prognosis of human neuroblastoma.

Curcumin regulates low-linear energy transfer γ-radiation-induced NFκB-dependent telomerase activity in human neuroblastoma cells

PURPOSE

We recently reported that curcumin attenuates ionizing radiation (IR)-induced survival signaling and proliferation in human neuroblastoma cells. Also, in the endothelial system, we have demonstrated that NFκB regulates IR-induced telomerase activity (TA). Accordingly, we investigated the effect of curcumin in inhibiting IR-induced NFκB-dependent hTERT transcription, TA, and cell survival in neuroblastoma cells.

METHODS AND MATERIALS

SK-N-MC or SH-SY5Y cells exposed to IR and treated with curcumin (10-100 nM) with or without IR were harvested after 1 h through 24 h. NFκB-dependent regulation was investigated either by luciferase reporter assays using pNFκB-, pGL3-354-, pGL3-347-, or pUSE-IκBα-Luc, p50/p65, or RelA siRNA-transfected cells. NFκB activity was analyzed using an electrophoretic mobility shift assay and hTERT expression using the quantitative polymerase chain reaction. TA was determined using the telomerase repeat amplification protocol assay and cell survival using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium bromide and clonogenic assay.

RESULTS

Curcumin profoundly inhibited IR-induced NFκB. Consequently, curcumin significantly inhibited IR-induced TA and hTERT mRNA at all points investigated. Furthermore, IR-induced TA is regulated at the transcriptional level by triggering telomerase reverse transcriptase (TERT) promoter activation. Moreover, NFκB becomes functionally activated after IR and mediates TA upregulation by binding to the κB-binding region in the promoter region of the TERT gene. Consistently, elimination of the NFκB-recognition site on the telomerase promoter or inhibition of NFκB by the IκBα mutant compromises IR-induced telomerase promoter activation. Significantly, curcumin inhibited IR-induced TERT transcription. Consequently, curcumin inhibited hTERT mRNA and TA in NFκB overexpressed cells. Furthermore, curcumin enhanced the IR-induced inhibition of cell survival.

CONCLUSIONS

These results strongly suggest that curcumin inhibits IR-induced TA in an NFκB dependent manner in human neuroblastoma cells.

Low-dose γ-radiation-induced oxidative stress response in mouse brain and gut: regulation by NFκB-MnSOD cross-signaling

Radiation-induced amplification of reactive oxygen species (ROS) may be a sensing mechanism for activation of signaling cascades that influence cell fate. However, the regulated intrinsic mechanisms and targets of low-dose ionizing radiation (LDIR) are still unclear. Accordingly, we investigated the effects of LDIR on NFκB signal transduction and manganese superoxide dismutase (SOD2) activity in mice brain and gut. LDIR resulted in both dose-dependent and persistent NFκB activation in gut and brain. QPCR displayed a dose- and tissue-dependent differential modulation of 88 signaling molecules. With stringent criteria, a total of 15 (2cGy), 43 (10cGy) and 19 (50cGy) genes were found to be commonly upregulated between brain and gut. SOD2 immunostaining showed a LDIR-dose dependent increase. Consistent with the NFκB results, we observed a persistent increase in SOD2 activity after LDIR. Moreover, muting of LDIR-induced NFκB attenuated SOD2 transactivation and cellular localization. These results imply that exposure of healthy tissues to LDIR results in induced NFκB and SOD2 activity and transcriptional activation of NFκB-signal transduction/target molecules. More importantly, the results suggest that NFκB initiates a feedback response through transcriptional activation of SOD2 that may play a key role in the LDIR-induced oxidative stress response and may control the switch that directs cell fate.