Radiation-inducible Promoter Research Articles

Efficient enhancement of the antimicrobial activity of Chlamydomonas reinhardtii extract by transgene expression and molecular modification using ionizing radiation

BackgroundIonizing radiation has been used for mutagenesis or material modification. The potential to use microalgae as a platform for antimicrobial production has been reported, but little work has been done to advance it beyond characterization to biotechnology. This study explored two different applications of ionizing radiation as a metabolic remodeler and a molecular modifier to enhance the antimicrobial activity of total protein and solvent extracts of Chlamydomonas reinhardtii cells.ResultsFirst, highly efficient transgenic C. reinhardtii strains expressing the plant-derived antimicrobial peptides, AtPR1 or AtTHI2.1, were developed using the radiation-inducible promoter, CrRPA70Ap. Low transgene expression was significantly improved through X-irradiation (12–50 Gy), with peak activity observed within 2 h. Protein extracts from these strains after X-irradiation showed enhanced antimicrobial activity against the prokaryotic bacterium, Pseudomonas syringae, and the eukaryotic fungus, Cryptococcus neoformans. In addition, X-irradiation (12 Gy) increased the growth and biomass of the transgenic strains. Second, C. reinhardtii cell extracts in ethanol were γ-irradiated (5–20 kGy), leading to molecular modifications and increased antimicrobial activity against the phytopathogenic bacteria, P. syringae and Burkholderia glumae, in a dose-dependent manner. These changes were associated with alterations in fatty acid composition. When both transgenic expression of antimicrobial peptides and molecular modification of bioactive substances were applied, the antimicrobial activity of C. reinhardtii cell extracts was further enhanced to some extent.ConclusionOverall, these findings suggest that ionizing radiation can significantly enhance the antimicrobial potential of C. reinhardtii through efficient transgene expression and molecular modification of bioactive substances, making it a valuable source of natural antimicrobial agents. Ionizing radiation can act not only as a metabolic remodeler of transgene expression in microalgae but also as a molecular modifier of the bioactive substances.

Lentiviral vector with a radiation-inducible promoter, carrying the ING4 gene, mediates radiosensitization controlled by radiotherapy in cervical cancer cells.

The presence of hypoxia in solid tumors is considered one of the major factors that contribute to radiation resistance. The aim of the present study was to establish a therapeutic system, which can be controlled by radiation itself, to enhance radiosensitivity. For this purpose, a lentiviral gene therapy vector containing the human inhibitor of growth 4 (ING4) and its upstream promoter, human early growth response factor-1 (EGR1), which possesses the radiation-inducible characteristics to activate the transcription of its downstream genes, was constructed. Downstream fluorescence proteins were investigated to ensure that the EGR1 promoter was induced by irradiation. Furthermore, ING4 open reading frame (ORF) expression was detected by western blotting. The cell cycle was analyzed by fluorescence-activated cell sorting analysis 48 h after the cells were exposed to X-rays ranging between 0 and 8 Gy. In cells stably and transiently transfected with reporter plasmids, the EGR1-driver gene was sensitive to ionizing irradiation. Furthermore, irradiation-induced ING4 gene expression was observed. The enhanced ING4 expression increased the number of cells in the G2/M phase and decreased the proportion of cells in the G1/S phase. Therefore, ING4 expression inhibited cell proliferation and was associated with less colonies being formed. Furthermore, ING4 suppressed hypoxia-inducible factor 1α expression under hypoxic conditions and promoted cell apoptosis. Overall, these results revealed that combining the EGR1 promoter and ING4 ORF using a lentivirus system may be a promising therapeutic strategy with which to enhance radiosensitivity controlled by radiation. However, further studies using in vivo models are required to confirm these findings.

Experimental Study of EGFR-targeted Adenovirus Vector Mediated tRFs Silencing in Reversing Radioresistance of Cervical Squamous Cell Carcinoma

Acquired radioresistance during radiotherapy has been considered as one of the most important reasons for local recurrence or treatment failure of cervical squamous cell carcinoma (CSCC). The tRNA-derived RNA fragments (tRFs) has been reported to involve in various biological processes and may play an important role in radioresistance. The aim of the present study was to analyze the role of tRFs in tumor radiosensitivity, and explore possible mechanisms for targeted intervention of tRFs in reversing CSCC radioresistance. The radioresistant CSCC cell line (SiHa-R) was established. The expression profile of tRFs was used to determine the differentially expressed tRFs in SiHa-R cells. Tumor tissue and serum samples from patients with CSCC were collected, and the relationship between tRFs expression levels and clinical radiotherapy sensitivity was analyzed. Two recombinant replication-deficient adenovirus vectors, Ad.Egr-si-tRFs (promoter Egr-1 with high radiation activation efficiency mediated tRFs silencing sequence) and Ad.CMV-sCAR-EGF (expressed bifunctional fusion protein sCAR-EGF targeting epidermal growth factor receptor), were constructed using gene recombination technique. The dose- and time-effect of radiation-induced tRFs silencing, the expression characteristics of fusion proteins, and their effects on the radiosensitivity of CSCC were observed after targeted infection with adenovirus vectors. Targeted silencing of tRFs to reverse CSCC radioresistance in experimental treatment protocols was explored. Among the detected candidate 2207 tRFs genes, tRF-16-JUO9YED was significantly upregulated in radioresistant CSCC cells. Under the guidance of the fusion protein sCAR-EGF expressed by Ad.CMV-sCAR-EGF, Ad.Egr-si-tRFs could efficiently targeted infect CSCC cells. After tRF-16-JUO9YED silencing mediated by radiation-induced promoter Egr-1, related downstream genes JAG2, SMO, PMM2 and AGK were down-regulated in CSCC cells. It was demonstrated that EGFR-targeted adenovirus vector mediated tRFs silencing might greatly improve radiosensitivity by reducing cell proliferation, inducing more apoptosis, inhibiting migration and invasion, affecting cell cycle and differentiation in radioresistant CSCC cells. This study revealed possible involvement of dysregulated tRFs in the regulation of the process of radioresistance in CSCC cells. EGFR-targeted adenovirus vector mediated tRF-16-JUO9YED silencing may reverse CSCC radioresistance, improve tumor radiotherapy effect, and provide experimental evidence for tumor gene-radiotherapy.

PSA/PSMA Targeted Recombinant Adenovirus Vector with Radiation-induced Promoter t-PA Mediated CircRNA_100385 Silencing and Its Mechanism for Regulating Radiosensitivity in Prostate Cancer

PSA/PSMA Targeted Recombinant Adenovirus Vector with Radiation-induced Promoter t-PA Mediated CircRNA_100385 Silencing and Its Mechanism for Regulating Radiosensitivity in Prostate Cancer

CCAAT Box, Not CArG Motifs, Identify Surviving as a Highly Potent Radiation Inducible Promoter

Radiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification to alter the sensitivity of tumor cells to the effect of applied radiation. Some previous studies concluded that CArG motifs are the elements responsible for radiation mediated transcription regulation, while other concluded that CCAAT box consensus are present in low frequencies in radioresponsive genes in comparison to normal genes. Using bioinformatics we aim to detect mechanism of radiation mediated transcription regulation in the context of glioblastoma adenoviral gene therapy. The effect of radiation was tested on 6 different in-house promoters (iNOS, FLT-1, DR5, Cox-2, VEGF, and survivin) where levels of mRNA expression of these promoters were assessed using Quantitative RTPCR in D54 MG cells before and after radiation exposure. Recombinant Ad/reporter genes driven by 7 different promoters; CMV, VEGF, FLT-1, DR5, iNOS, cox-2 and Survivin were constructed. Glioma cell lines were infected with different Multiplicity of infection of the (promoter) Ad or CMV Ad. Cells were then exposed to a range of radiation (0-12Gy) at single fraction. Fluorescent Microscopy, Luc assay and X-gal staining was used to detect the level of expression of related genes. A time course experiment was carried out to look for effect of time of radiation on gene expression. These promoters were screened for the presence CArG motifs and CCAAT box consensus using NCBI Blast bioinformatics software. Radiotherapy increase the expression of gene expression by1.75-fold in DR5, 2-fold in VEGF and 0 fold Flt-1 after 2 hr of radiation. Most importantly Cells treated with RT and Ad Luc driven by Survivin promoter showed 5-fold increase in expression after 2 Gy of radiation in compare to non-irradiated cells. RNA analysis was done and has shown increase copy no. of corresponding genes in level range from 2 fold for VEGF 3 fold for iNOS and as expected 30 fold more for Survivin. Using NCBI BLAST software, none of CArG motifs were found in the different 6 promoters. Survivin with the best response to radiation had the lowest number of CCAAT box (n=2) while iNOS with the lowest response to radiation had the highest number of CCAAT (n=14) with other promoters having different numbers of CCAAT ranging between these two values. Additionally, the initiator element consensus (YYANWYY) was not found in all the responsive promoters to radiation. Survivin as a radiation inducible promoter for glioblastoma viral gene therapy is independent of CArG motifs. Low frequency of CCAAT box could be responsible for this phenomena.

Proximity of Radiation Desiccation Response Motif to the core promoter is essential for basal repression as well as gamma radiation-induced gyrB gene expression in Deinococcus radiodurans

The radioresistant D. radiodurans regulates its DNA damage regulon (DDR) through interaction between a 17bp palindromic cis-regulatory element called the Radiation Desiccation Response Motif (RDRM), the DdrO repressor and a protease IrrE. The role of RDRM in regulation of DDR was dissected by constructing RDRM sequence-, position- or deletion-variants of Deinococcal gyrB gene (DR0906) promoter and by RDRM insertion in the non-RDRM groESL gene (DR0606) promoter, and monitoring the effect of such modifications on the basal as well as gamma radiation inducible promoter activity by quantifying fluorescence of a GFP reporter. RDRM sequence-variants revealed that the conservation of sequence at the 5th and 13th position and the ends of RDRM is essential for basal repression by interaction with DdrO. RDRM position-variants showed that the sequence acts as a negative regulatory element only when located around transcription start site (TSS) and within the span of RNA polymerase (RNAP) binding region. RDRM deletion-variants indicated that the 5′ sequence of RDRM possibly possesses an enhancer-like element responsible for higher expression yields upon repressor clearance post-irradiation. The results suggest that RDRM plays both a negative as well as a positive role in the regulation of DDR in D. radiodurans.

Survivin a radiogenetic promoter for glioblastoma viral gene therapy independently from CArG motifs

BackgroundRadiogenetic therapy is a novel approach in the treatment of cancer, which employs genetic modification to alter the sensitivity of tumor cells to the effect of applied radiation.AimTo select a potent radiation inducible promoter in the context of brain tumors and to investigate if CArG radio responsive motifs or other elements in the promoter nucleotide sequences can correlate to its response to radiation.MethodsTo select initial candidates for promoter inducible elements, the levels of mRNA expression of six different promoters were assessed using Quantitative RTPCR in D54 MG cells before and after radiation exposure. Recombinant Ad/reporter genes driven by five different promoters; CMV, VEGF, FLT-1, DR5 and survivin were constructed. Glioma cell lines were infected with different multiplicity of infection of the (promoter) Ad or CMV Ad. Cells were then exposed to a range of radiation (0–12 Gy) at single fraction. Fluorescent microscopy, Luc assay and X-gal staining was used to detect the level of expression of related genes. Different glioma cell lines and normal astrocytes were infected with Ad survivin and exposed to radiation. The promoters were analyzed for presence of CArG radio-responsive motifs and CCAAT box consensus using NCBI blast bioinformatics software.ResultsRadiotherapy increases the expression of gene expression by 1.25–2.5 fold in different promoters other than survivin after 2 h of radiation. RNA analysis was done and has shown an increase in copy number of tenfold for survivin. Most importantly cells treated with RT and Ad Luc driven by survivin promoter showed a fivefold increase in expression after 2 Gy of radiation in comparison to non-irradiated cells. Presence or absence of CArG motifs did not correlate with promoter response to radiation. Survivin with the best response to radiation had the lowest number of CCAAT box.ConclusionSurvivin is a selective potent radiation inducible promoter for glioblastoma viral gene therapy and this response to radiation could be independent of CArG motifs.

Radiation persistently promoted oxidative stress, activated mTOR via PI3K/Akt, and downregulated autophagy pathway in mouse intestine

While acute effects of toxic radiation doses on intestine are well established, we are yet to acquire a complete spectrum of sub-lethal radiation-induced chronic intestinal perturbations at the molecular level. We investigated persistent effects of a radiation dose (2Gy) commonly used as a daily fraction in radiotherapy on oxidants and anti-oxidants, and autophagy pathways, which are interlinked processes affecting intestinal homeostasis. Six to eight weeks old C57BL/6J mice (n=10) were exposed to 2Gy γ-ray. Mice were euthanized two or twelve months after radiation, intestine surgically removed, and flushed using sterile PBS. Parts of the intestine from jejunal–ilial region were fixed, frozen, or used for intestinal epithelial cell (IEC) isolation. While oxidant levels and mitochondrial status were assessed in isolated IEC, autophagy and oxidative stress related signaling pathways were probed in frozen and fixed samples using PCR-based expression arrays and immunoprobing. Radiation exposure caused significant alterations in the expression level of 26 autophagy and 17 oxidative stress related genes. Immunoblot results showed decreased Beclin1 and LC3-II and increased p62, PI3K/Akt, and mTOR. Flow cytometry data showed increased oxidant production and compromised mitochondrial integrity in irradiated samples. Immunoprobing of intestinal sections showed increased 8-oxo-dG and nuclear PCNA, and decreased autophagosome marker LC3-II in IEC after irradiation. We show that sub-lethal radiation could persistently downregulate anti-oxidants and autophagy signaling, and upregulate oxidant production and proliferative signaling. Radiation-induced promotion of oxidative stress and downregulation of autophagy could work in tandem to alter intestinal functions and have implications for post-radiation chronic gastrointestinal diseases.

Harnessing a radiation inducible promoter of Deinococcus radiodurans for enhanced precipitation of uranium

Bioremediation is an attractive option for the treatment of radioactive waste. We provide a proof of principle for augmentation of uranium bioprecipitation using the radiation inducible promoter, Pssb from Deinococcus radiodurans. Recombinant cells of D. radiodurans carrying acid phosphatase gene, phoN under the regulation of Pssb when exposed to 7kGy gamma radiation at two different dose rates of 56.8Gy/min and 4Gy/min, showed 8–9 fold increase in acid phosphatase activity. Highest whole cell PhoN activity was obtained after 2h in post irradiation recovery following 8kGy of high dose rate radiation. Such cells showed faster removal of high concentrations of uranium than recombinant cells expressing PhoN under a radiation non-inducible deinococcal promoter, PgroESL and could precipitate uranium even after continuous exposure to 0.6Gy/min gamma radiation for 10 days. Radiation induced recombinant D. radiodurans cells when lyophilized retained high levels of PhoN activity and precipitated uranium efficiently. These results highlight the importance of using a suitable promoter for removal of radionuclides from solution.

An autologous in situ tumor vaccination approach for hepatocellular carcinoma. 2. Tumor-specific immunity and cure after radio-inducible suicide gene therapy and systemic CD40-ligand and Flt3-ligand gene therapy in an orthotopic tumor model.

Diffuse hepatocellular carcinoma (HCC) is a lethal disease that radiation therapy (RT) currently has a limited role in treating because of the potential for developing fatal radiation-induced liver disease. However, recently diffuse HCC, "radio-inducible suicide gene therapy" has been shown to enhance local tumor control and residual microscopic disease within the liver for diffuse HCC, by using a combination of chemoactivation and molecular radiosensitization. We have demonstrated that the addition of recombinant adenovirus-expressing human Flt3 ligand (Adeno-Flt3L) after radio-inducible suicide gene therapy induced a Th1-biased, immune response and enhanced tumor control in an ectopic model of HCC. We hypothesized that sequential administration of recombinant adenovirus-expressing CD40L (Adeno-CD40L) could further potentiate the efficacy of our trimodal therapy with RT + HSV-TK + Adeno-Flt3L. We examined our hypothesis in an orthotopic model of diffuse HCC using BNL1ME A.7R.1 (BNL) cells in Balb/c mice. BNL murine hepatoma cells (5 × 10(4)) transfected with an expression vector of HSV-TK under the control of a radiation-inducible promoter were injected intraportally into BALB/cJ mice. Fourteen days after the HCC injection, mice were treated with a 25 Gy dose of radiation to the whole liver, followed by ganciclovir (GCV) treatment and systemic adenoviral cytokine gene therapy (Flt3L or CD40L or both). Untreated mice died in 27 ± 4 days. Radiation therapy alone had a marginal effect on survival (median = 35 ± 7 days) and the addition of HSV-TK/GCV gene therapy improved the median survival to 47 ± 6 days. However, the addition of Adeno-Flt3L to radiation therapy and HSV-TK/GCV therapy significantly (P = 0.0005) increased survival to a median of 63 ± 20 days with 44% (7/16) of the animals still alive 116 days after tumor implantation. The curative effect of Flt3L was completely abolished when using immunodeficient nude mice or mice depleted for CD4, CD8 and natural killer cells. The addition of Adeno-CD40L further improved the median survival of animals to 80 ± 15 days and this effect was abolished only when using anti-CD8 antibodies. Chromium-51 (51Cr) release assay showed cytotoxic T lymphocyte (CTL) activation, suggesting efficient dendritic cell (DC) activation with CTL activation after the treatment. Furthermore, when surviving mice were rechallenged with BNL-ETK cells on the foot pad, RT + HSV-TK/GCV + Flt3L + CD40L-treated mice developed a small tumor on day 56 but the tumor eventually disappeared after 105 days. Mice treated with RT + HSV-TK/GCV + Flt3L showed a slowed tumor growth curve compared with untreated mice. Therefore, combination therapy using Flt3L to induce DC proliferation and CD40L to enhance DC maturation holds great promise for immunomodulation of radiation therapy to enhance HCC tumor control and prevent progression of disease in patients with diffuse HCC.

Inhibition of Radiation-Induced Lung Adenocarcinoma Cell Metastasis by Adenovirus of PIAS3 Overexpression Driven by Radiation-Inducible Promoter (<i>Ad-pig3RRP-PIAS3</i>)

Radiotherapy is one of important approaches for pulmonary adenocarcinoma. However, many studies have shown that radiation can also enhance the ability of tumor cells metastasis, although the lung adenocarcinoma could be killed. The increased metastasis induced by radiation is associated with the activation of STAT3 in lung adenocarcinoma cells. Based on the importance role of STAT3 in cell proliferation and survival, we can construct an adenovirus vector of PIAS3 overexpress driven by radiation-induced promoter to inhibit the activation of STAT3 specifically. In this way, when STAT3 was activated by radiation, the expression of PIAS3 will be increased at the same time; this lead to the inhibition of invasion and metastasis caused by STAT3 in lung adenocarcinoma cells. These researches are expected to develop a novel target and method for radiotherapy and molecular therapy of lung adenocarcinoma.

Radiation-inducible promoters mediated puma gene in the treatment of oral squamous cell carcinoma

Radiation-inducible promoters mediated puma gene in the treatment of oral squamous cell carcinoma

Gamma Irradiation and Targeted Radionuclides Enhance the Expression of the Noradrenaline Transporter Transgene Controlled by the Radio-Inducible p21WAF1/CIP1 Promoter

The use of radiation-inducible promoters to drive transgene expression offers the possibility of temporal and spatial regulation of gene activation. This study assessed the potential of one such promoter element, p21(WAF1/CIP1) (WAF1), to drive expression of the noradrenaline transporter (NAT) gene, which conveys sensitivity to radioiodinated meta-iodobenzylguanidine (MIBG). An expression vector containing NAT under the control of the radiation-inducible WAF1 promoter (pWAF/NAT) was produced. The non-NAT expressing cell lines UVW (glioma) and HCT116 (colorectal cancer) were transfected with this construct to assess radiation-controlled WAF1 activation of the NAT gene. Transfection of UVW and HCT cells with pWAF/NAT conferred upon them the ability to accumulate [(131)I]MIBG, which led to increased sensitivity to the radiopharmaceutical. Pretreatment of transfected cells with γ radiation or the radiopharmaceuticals [(123)I]MIBG or [(131)I]MIBG induced dose- and time-dependent increases in subsequent [(131)I]MIBG uptake and led to enhanced efficacy of [(131)I]MIBG-mediated cell kill. Gene therapy using WAF1-driven expression of NAT has the potential to expand the use of this therapeutic modality to tumors that lack a radio-targetable feature.

An oncolytic adenovirus regulated by a radiation-inducible promoter selectively mediates hSulf-1 gene expression and mutually reinforces antitumor activity of I131-metuximab in hepatocellular carcinoma

Gene therapy and antibody approaches are crucial auxiliary strategies for hepatocellular carcinoma (HCC) treatment. Previously, we established a survivin promoter-regulated oncolytic adenovirus that has inhibitory effect on HCC growth. The human sulfatase-1 (hSulf-1) gene can suppress the growth factor signaling pathways, then inhibit the proliferation of cancer cells and enhance cellular sensitivity to radiotherapy and chemotherapy. I131-metuximab (I131-mab) is a monoclonal anti-HCC antibody that conjugated to I131 and specifically recognizes the HAb18G/CD147 antigen on HCC cells. To integrate the oncolytic adenovirus-based gene therapy and the I131-mab-based radioimmunotherapy, this study combined the CArG element of early growth response-l (Egr-l) gene with the survivin promoter to construct a radiation-inducible enhanced promoter, which was used to recombine a radiation-inducible oncolytic adenovirus as hSulf-1 gene vector. When I131-mab was incorporated into the treatment regimen, not only could the antibody produce radioimmunotherapeutic effect, but the I131 radiation was able to further boost adenoviral proliferation. We demonstrated that the CArG-enhanced survivin promoter markedly improved the proliferative activity of the oncolytic adenovirus in HCC cells, thereby augmenting hSulf-1 expression and inducing cancer cell apoptosis. This novel strategy that involved multiple, synergistic mechanisms, including oncolytic therapy, gene therapy and radioimmunotherapy, was demonstrated to exert an excellent anti-cancer outcome, which will be a promising approach in HCC treatment.

A randomized phase III multi-institutional study of TNFerade biologic with 5-FU and radiotherapy for locally advanced pancreatic cancer: Final results

4055 Background: TNFerade biologic (TNF) is a novel means of selective delivery of TNF-α to tumor cells by gene transfer through intratumoral (IT) injection. TNF is a replication deficient adenovirus vector containing TNF-α cDNA ligated downstream from a radiation-inducible Egr-1 promoter, allowing spatiotemporal constraint of TNF-α production to the radiation field. Herein we report the final results of a multi-center, randomized, open-label, controlled phase III trial of TNF with chemoradiotherapy for locally advanced pancreatic ductal adenocarcinoma (PDA). Methods: Pts with locally advanced PDA were randomized 1:2 to standard of care (SOC; 5-FU/RT followed by GEM) versus TNF + SOC. RT dose was 50.4 Gy in 28 fractions. Concurrent 5-FU (200 mg/m2/day IV) started on day 1 of RT each wk. TNF was injected IT ~4 hrs prior to RT weekly by percutaneous (PTA) or endoscopic (EUS) approach. 4 wks after RT, GEM (1000 mg/m2 IV) was given until progression or toxicity. Results: Of 277 pts, 187 were randomized to TNF and 90 to SOC. Demographic/baseline characteristics were similar between arms (all NS), as was GEM received (67 vs. 68%; 7.0 vs. 7.6 total wks). Median f/up was 9.1 mos (range, 0.1-50.5). Median OS for TNF by ITT analysis was 10.1 mos (95% CI, 9.1-11.7) vs. 10.0 mos (95% CI, 7.6-11.2) for SOC (p=0.6). TNF delivery method did not affect OS (9.4 mos for PTA vs. 11.5 for EUS; p=0.7). Baseline CA19-9 > 1000 was found to impart independent risk to TNF pts (HR=1.7; p=0.02). Subgroup analysis (SGA) of 86 pts with T1-T3 disease showed an OS benefit for TNF compared to SOC (10.9 vs. 9.0 mos, respectively; p=0.04). TNF resulted in more grade 1-2 fever/chills (p<0.001) as well as grade 3 (p<0.001) and 4 (p=0.05) toxicities (commonly lymphopenia, hypo/hyperkalemia, abd/chest pain) than SOC. Use of PTA vs. EUS did not affect grade 3/4 toxicity rates. Conclusions: TNF + SOC did not prolong OS for locally advanced PDA. SGA reveals a possible OS benefit for early stage (T1-T3) tumors and CA19-9 < 1000. PTA and EUS injection achieved similar rates of efficacy and toxicity. Grade 1-2 toxicity typical of systemic exposure to TNF-α (pyrexia/hypotension/chills) was common, but grade 3-4 was minimal.

Genetic background and 227Thorium as risk factors in biologically based models for induction of bone cancer in mice

We explore the potential for the biologically based two-stage clonal expansion model to make statements about the influence of genetic factors on the steps in the model. We find evidence that the different susceptibility of BALB/C and CBA/Ca mice to bone cancer after (227)Thorium injection may be mostly due to different promotional responses to radiation. In BALB/C×CBA/Ca back-crossed mice, we analyzed the specific contribution of two individual loci in the carcinogenic process. This analysis suggests that the two high- or low-risk alleles are acting on promotion or on the background parameters, but not on radiation-induced initiation. Taken together with the comparison of CBA/Ca and BALB/C mice, this hints at the possibility that the two loci are candidates for modifying radiation-induced promotion.

Radiation-inducible promoter mediated puma gene for the treatment of tongue squamous cell carcinoma

Radiation-inducible promoter mediated puma gene for the treatment of tongue squamous cell carcinoma

Co-expression of interleukin 12 enhances antitumor effects of a novel chimeric promoter-mediated suicide gene therapy in an immunocompetent mouse model

The human telomerase reverse transcriptase (hTERT) promoter has been widely used in target gene therapy of cancer. However, low transcriptional activity limited its clinical application. Here, we designed a novel dual radiation-inducible and tumor-specific promoter system consisting of CArG elements and the hTERT promoter, resulting in increased expression of reporter genes after gamma-irradiation. Therapeutic and side effects of adenovirus-mediated horseradish peroxidase (HRP)/indole-3-acetic (IAA) system downstream of the chimeric promoter were evaluated in mice bearing Lewis lung carcinoma, combining with or without adenovirus-mediated interleukin 12 (IL12) gene driven by the cytomegalovirus promoter. The combination treatment showed more effective suppression of tumor growth than those with single agent alone, being associated with pronounced intratumoral T-lymphocyte infiltration and minor side effects. Our results suggest that the combination treatment with HRP/IAA system driven by the novel chimeric promoter and the co-expression of IL12 might be an effective and safe target gene therapy strategy of cancer.

Radiation-inducible promoter mediated PUMA Gene in the the treatment of Tca8113

Objective: The aim of this study is to explore the therapeutic effect of the PUMA gene mediated by ra- diation-inducible promoters in the treatment of ton- gue squamous cell carcinoma. Methods: Recombi- nant pcDNA3.1 (+)/E-PUMA was constructed, in which the PUMA gene was mediated by a synthetic radiation inducible promoter. The recombined plas-mids were transfected into the Tca8113 cell and xeno- grafts of human tongue squamous carcinoma in na- ked mice respectively. After 24 h, the tumors were tr- eated with 3 Gy of irradiation to upregulate the PU- MA gene expression. PUMA mRNA was detected by RT-PCR. Proliferating cell nuclear antigen (PCNA) and apoptosis were detected by immunohistochemi- cal method and in situ end-labeling (ISEL) respecti- vely. The data were analyzed using the SPSS11.0 soft- ware package for chi-square test. RESULTS: Com-pared with the control group, the comparative survi- val rate of Tca8113 cells in the PUMA/IR group was markedly decreased and the xenografts were signify- cantly suppressed. Up-regulation of PUMA gene ex- pression was observed in the Tca8113 cells and in the xenografts after irradiation. The apoptosis indices of the Tca8113 cells and xenograft with irradiation were markedly higher than those without irradiation. At the same time, the proliferation indices of the Tca- 8113 cells and xenografts with irradiation were mark- edly lower than those without irradiation. Conclu- sions: radiation-induc ible promoters can serve as molecular switches to improve the expression of PU- MA gene in tongue squamous cell carcinoma both in vivo and in vitro. Low-dose induction radiation can significantly improve therapeutic efficiency.

Cancer risks after radiation exposure in middle age.

Epidemiological data show that radiation exposure during childhood is associated with larger cancer risks compared with exposure at older ages. For exposures in adulthood, however, the relative risks of radiation-induced cancer in Japanese atomic bomb survivors generally do not decrease monotonically with increasing age of adult exposure. These observations are inconsistent with most standard models of radiation-induced cancer, which predict that relative risks decrease monotonically with increasing age at exposure, at all ages. We analyzed observed cancer risk patterns as a function of age at exposure in Japanese atomic bomb survivors by using a biologically based quantitative model of radiation carcinogenesis that incorporates both radiation induction of premalignant cells (initiation) and radiation-induced promotion of premalignant damage. This approach emphasizes the kinetics of radiation-induced initiation and promotion, and tracks the yields of premalignant cells before, during, shortly after, and long after radiation exposure. Radiation risks after exposure in younger individuals are dominated by initiation processes, whereas radiation risks after exposure at later ages are more influenced by promotion of preexisting premalignant cells. Thus, the cancer site-dependent balance between initiation and promotion determines the dependence of cancer risk on age at radiation exposure. For example, in terms of radiation induction of premalignant cells, a quantitative measure of the relative contribution of initiation vs promotion is 10-fold larger for breast cancer than for lung cancer. Reflecting this difference, radiation-induced breast cancer risks decrease with age at exposure at all ages, whereas radiation-induced lung cancer risks do not. For radiation exposure in middle age, most radiation-induced cancer risks do not, as often assumed, decrease with increasing age at exposure. This observation suggests that promotional processes in radiation carcinogenesis become increasingly important as the age at exposure increases. Radiation-induced cancer risks after exposure in middle age may be up to twice as high as previously estimated, which could have implications for occupational exposure and radiological imaging.