Radiation-mediated control of drug delivery

The Role of Integrins for Mediating Nanodrugs to Improve Performance in Tumor Diagnosis and Treatment

Integrins are heterodimeric transmembrane proteins that mediate adhesive connections between cells and their surroundings, including surrounding cells and the extracellular matrix (ECM). They modulate tissue mechanics and regulate intracellular signaling, including cell generation, survival, proliferation, and differentiation, and the up-regulation of integrins in tumor cells has been confirmed to be associated with tumor development, invasion, angiogenesis, metastasis, and therapeutic resistance. Thus, integrins are expected to be an effective target to improve the efficacy of tumor therapy. A variety of integrin-targeting nanodrugs have been developed to improve the distribution and penetration of drugs in tumors, thereby, improving the efficiency of clinical tumor diagnosis and treatment. Herein, we focus on these innovative drug delivery systems and reveal the improved efficacy of integrin-targeting methods in tumor therapy, hoping to provide prospective guidance for the diagnosis and treatment of integrin-targeting tumors.

Effects of radiation on tumor vasculature

Radiation has been utilized as a direct cytotoxic tumorcidal modality, however, the effect of radiation on tumor vasculature influences response to anticancer therapies. Although numerous reports have demonstrated vascular changes in irradiated tumors, the findings and implications are extensive and at times contradictory depending on the radiation dose, timing, and models used. In this review, we focus on the radiation-mediated effects on tumor vasculature with respect to doses used, timing postradiation, vasculogenesis, adhesion molecule expression, permeability, and pericyte coverage, including the latest findings.

Molecular Imaging with Reporter Genes: Has Its Promise Been Delivered?

The first reporter systems were developed in the early 1980s and were based on measuring the activity of an enzyme-as a surrogate measure of promoter-driven transcriptional activity-which is now known as a reporter gene system. The initial objective and application of reporter techniques was to analyze the activity of a specific promoter (namely, the expression of a gene that is under the regulation of the specific promoter that is linked to the reporter gene). This system allows visualization of specific promoter activity with great sensitivity. In general, there are 2 classes of reporter systems: constitutively expressed (always-on) reporter constructs used for cell tracking, and inducible reporter systems sensitive to endogenous signaling molecules and transcription factors that characterize specific tissues, tumors, or signaling pathways.This review traces the development of different reporter systems, using fluorescent and bioluminescent proteins as well as radionuclide-based reporter systems. The development and application of radionuclide-based reporter systems is the focus of this review. The question at the end of the review is whether the "promise" of reporter gene imaging has been realized. What is required for moving forward with radionuclide-based reporter systems, and what is required for successful translation to clinical applications?

Enhancing Radiotherapeutic Effect With Nanoparticle-Mediated Radiosensitizer Delivery Guided By Focused Gamma Rays In Lewis Lung Carcinoma-Bearing Mouse Brain Tumor Models

Background

Targeting radiosensitizer-incorporated nanoparticles to a tumor could allow for less normal tissue toxicity with more efficient drug release, thus improving the efficacy and safety of radiation treatment. The aim of this study was to improve tumor-specific delivery and bioavailability of a nanoparticle-mediated radiosensitizer in mouse brain tumor models.

Methods

A pH-sensitive nanoparticle, chitoPEGAcHIS, was conjugated to recombinant peptide HVGGSSV that could bind to tax-interaction protein 1 (TIP-1) as a radiation-inducible receptor. Then the c-Jun N-terminal kinase (JNK) inhibitor, SP600125 was incorporated into this copolymer to fabricate a HVGGSSV-chitoPEGAcHIS-SP600125 (HVSP-NP) nanoradiosensitizer. In vitro and in vivo radiation treatment were performed using a Gamma Knife unit. The tumor targetability of HVSP-NP was estimated by optical bioluminescence. Synergistic therapeutic effects of radiation treatment and HVSP-NP were investigated in Lewis lung carcinoma (LLC) cell-bearing mouse brain tumor models.

Results

The SP600125 JNK inhibitor effectively reduced DNA damage repair to irradiated LLC cells. A pH sensitivity assay indicated that HVSP-NP swelled at acidic pH and increased in diameter, and its release rate gradually increased. Optical bioluminescence assay showed that radiation induced TIP-1 expression in mouse brain tumor and that the nanoradiosensitizer selectively targeted irradiated tumors. Radiation treatment with HVSP-NP induced greater apoptosis and significantly inhibited tumor growth compared to radiation alone.

Conclusion

As a novel nanoradiosensitizer, HVSP-NP was found to be able to selectively target irradiated tumors and significantly increase tumor growth delay in LLC-bearing mouse brain tumor models. This research shows that delivering a pH-sensitive nanoradiosensitizer to a brain tumor in which TIP-1 is induced by radiation can result in improved radiosensitizer-release in an acidic microenvironment of tumor tissue and in created synergistic effects in radiation treatment.

Radiation-Induced Transformation of Immunoregulatory Networks in the Tumor Stroma

The implementation of novel cancer immunotherapies in the form of immune checkpoint blockers represents a major advancement in the treatment of cancer, and has renewed enthusiasm for identifying new ways to induce antitumor immune responses in patients. Despite the proven efficacy of neutralizing antibodies that target immune checkpoints in some refractory cancers, many patients do not experience therapeutic benefit, possibly owing to a lack of antitumor immune recognition, or to the presence of dominant immunosuppressive mechanisms in the tumor microenvironment (TME). Recent developments in this field have revealed that local radiotherapy (RT) can transform tumors into in situ vaccines, and may help to overcome some of the barriers to tumor-specific immune rejection. RT has the potential to ignite tumor immune recognition by generating immunogenic signals and releasing neoantigens, but the multiple immunosuppressive forces in the TME continue to represent important barriers to successful tumor rejection. In this article, we review the radiation-induced changes in the stromal compartments of tumors that could have an impact on tumor immune attack. Since different RT regimens are known to mediate strikingly different effects on the multifarious elements of the tumor stroma, special emphasis is given to different RT schedules, and the time after treatment at which the effects are measured. A better understanding of TME remodeling following specific RT regimens and the window of opportunity offered by RT will enable optimization of the design of novel treatment combinations.

Tumor radiosensitization by monomethyl auristatin E: mechanism of action and targeted delivery

Intrinsic tumor resistance to radiotherapy limits the efficacy of ionizing radiation (IR). Sensitizing cancer cells specifically to IR would improve tumor control and decrease normal tissue toxicity. The development of tumor-targeting technologies allows for developing potent radiosensitizing drugs. We hypothesized that the anti-tubulin agent monomethyl auristatin E (MMAE), a component of a clinically approved antibody-directed conjugate, could function as a potent radiosensitizer and be selectively delivered to tumors using an activatable cell-penetrating peptide targeting matrix metalloproteinases and RGD-binding integrins (ACPP-cRGD-MMAE). We evaluated the ability of MMAE to radiosensitize both established cancer cells and a low-passage cultured human pancreatic tumor cell line using clonogenic and DNA damage assays. MMAE sensitized colorectal and pancreatic cancer cells to IR in a schedule- and dose-dependent manner, correlating with mitotic arrest. Radiosensitization was evidenced by decreased clonogenic survival and increased DNA double-strand breaks in irradiated cells treated with MMAE. MMAE in combination with IR resulted in increased DNA damage signaling and activation of CHK1. To test a therapeutic strategy of MMAE and IR, PANC-1 or HCT-116 murine tumor xenografts were treated with nontargeted free MMAE or tumor-targeted MMAE (ACPP-cRGD-MMAE). While free MMAE in combination with IR resulted in tumor growth delay, tumor-targeted ACPP-cRGD-MMAE with IR produced a more robust and significantly prolonged tumor regression in xenograft models. Our studies identify MMAE as a potent radiosensitizer. Importantly, MMAE radiosensitization can be localized to tumors by targeted activatable cell-penetrating peptides.

Molecular-genetic imaging of cancer

Molecular-genetic imaging of cancer using nonviral delivery systems has great potential for clinical application as a safe, efficient, noninvasive tool for visualization of various cellular processes including detection of cancer, and its attendant metastases. In recent years, significant effort has been expended in overcoming technical hurdles to enable clinical adoption of molecular-genetic imaging. This chapter will provide an introduction to the components of molecular-genetic imaging and recent advances on each component leading to safe, efficient clinical applications for detecting cancer. Combination with therapy, namely, generating molecular-genetic theranostic constructs, will provide further impetus for clinical translation of this promising technology.

Sequential targeted delivery of paclitaxel and camptothecin using a cross-linked "nanosponge" network for lung cancer chemotherapy

The applicability of a HVGGSSV peptide targeted "nanosponge" drug delivery system for sequential administration of a microtubule inhibitor (paclitaxel) and topoisomerase I inhibitor (camptothecin) was investigated in a lung cancer model. Schedule-dependent combination treatment with nanoparticle paclitaxel (NP PTX) and camptothecin (NP CPT) was studied in vitro using flow cytometry and confocal imaging to analyze changes in cell cycle, microtubule morphology, apoptosis, and cell proliferation. Results showed significant G2/M phase cell cycle arrest, changes in microtubule dynamics that produced increased apoptotic cell death and decreased proliferation with initial exposure to NP PTX, followed by NP CPT in lung cancer cells. In vivo molecular imaging and TEM studies validated HVGGSSV-NP tumor binding at 24 h and confirmed the presence of Nanogold labeled HVGGSSV-NPs in tumor microvascular endothelial cells. Therapeutic efficacy studies conducted with sequential HVGGSSV targeted NP PTX and NP CPT showed 2-fold greater tumor growth delay in combination versus monotherapy treated groups, and 4-fold greater delay compared to untargeted and systemic drug controls. Analytical HPLC/MS methods were used to quantify drug content in tumor tissues at various time points, with significant paclitaxel and camptothecin levels in tumors 2 days postinjection and continued presence of both drugs up to 23 days postinjection. The efficacy of the NP delivery system in sequential treatments was corroborated in both in vitro and in vivo lung cancer models showing increased G2/M phase arrest and microtubule disruption, resulting in enhanced apoptotic cell death, decreased cell proliferation and vascular density.

ADAM-15 disintegrin-like domain structure and function

The ADAM (a disintegrin-like and metalloproteinase) proteins are a family of transmembrane cell-surface proteins with important functions in adhesion and proteolytic processing in all animals. Human ADAM-15 is the only member of the ADAM family with the integrin binding motif Arg-Gly-Asp (RGD) in its disintegrin-like domain. This motif is also found in most snake venom disintegrins and other disintegrin-like proteins. This unique RGD motif within ADAM-15 serves as an integrin ligand binding site, through which it plays a pivotal role in interacting with integrin receptors, a large family of heterodimeric transmembrane glycoproteins. This manuscript will present a review of the RGD-containing disintegrin-like domain structures and the structural features responsible for their activity as antagonists of integrin function in relation to the canonical RGD template.

Radiation-guided drug delivery to mouse models of lung cancer

PURPOSE

The purpose of this study was to achieve improved cancer-specific delivery and bioavailability of radiation-sensitizing chemotherapy using radiation-guided drug delivery.

EXPERIMENTAL DESIGN

Phage display technology was used to isolate a recombinant peptide (HVGGSSV) that binds to a radiation-inducible receptor in irradiated tumors. This peptide was used to target nab-paclitaxel to irradiated tumors, achieving tumor-specificity and enhanced bioavailability of paclitaxel.

RESULTS

Optical imaging studies showed that HVGGSSV-guided nab-paclitaxel selectively targeted irradiated tumors and showed 1.48 ± 1.66 photons/s/cm(2)/sr greater radiance compared with SGVSGHV-nab-paclitaxel, and 1.49 ± 1.36 photons/s/cm(2)/sr greater than nab-paclitaxel alone (P < 0.05). Biodistribution studies showed >5-fold increase in paclitaxel levels within irradiated tumors in HVGGSSV-nab-paclitaxel-treated groups as compared with either nab-paclitaxel or SGVSGHV-nab-paclitaxel at 72 hours. Both Lewis lung carcinoma and H460 lung carcinoma murine models showed significant tumor growth delay for HVGGSSV-nab-paclitaxel as compared with nab-paclitaxel, SGVSGHV-nab-paclitaxel,and saline controls. HVGGSSV-nab-paclitaxel treatment induced a significantly greater loss in vasculature in irradiated tumors compared with unirradiated tumors, nab-paclitaxel, SGVSGHV-nab-paclitaxel, and untreated controls.

CONCLUSIONS

HVGGSSV-nab-paclitaxel was found to bind specifically to the tax-interacting protein-1 (TIP-1) receptor expressed in irradiated tumors, enhance bioavailability of paclitaxel, and significantly increase tumor growth delay as compared with controls in mouse models of lung cancer. Here we show that targeting nab-paclitaxel to radiation-inducible TIP-1 results in increased tumor-specific drug delivery and enhanced biological efficacy in the treatment of cancer.

Tumor cell and tumor vasculature targeted liposomes for neutron capture therapy

Treatment of cancer using boron neutron capture therapy requires the specific accumulation of a relatively high concentration of 10B into tumor cells or tumor vasculature. In this paper, targeted liposomes were evaluated as carriers of 10B for this purpose. Na2 10B12H12 was successfully encapsulated into liposomes and relatively high amounts of 10B could be targeted to ovarian carcinoma cells (OVCAR-3) and endothelial cells (HUVEC). This was achieved by coupling a monoclonal antibody or an RGD peptide to the liposomes. The results suggest that targeted liposomes could meet the requirements of successful neutron capture therapy in the near future.

Viral infection and human disease--insights from minimotifs

Short functional peptide motifs cooperate in many molecular functions including protein interactions, protein trafficking, and posttranslational modifications. Viruses exploit these motifs as a principal mechanism for hijacking cells and many motifs are necessary for the viral life-cycle. A virus can accommodate many short motifs in its small genome size providing a plethora of ways for the virus to acquire host molecular machinery. Host enzymes that act on motifs such as kinases, proteases, and lipidation enzymes, as well as protein interaction domains, are commonly mutated in human disease, suggesting that the short peptide motif targets of these enzymes may also be mutated in disease; however, this is not observed. How can we explain why viruses have evolved to be so dependent on motifs, yet these motifs, in general do not seem to be as necessary for human viability? We propose that short motifs are used at the system level. This system architecture allows viruses to exploit a motif, whereas the viability of the host is not affected by mutation of a single motif.

The Role of Integrins in Cancer and the Development of Anti-Integrin Therapeutic Agents for Cancer Therapy

Integrins have been reported to mediate cell survival, proliferation, differentiation, and migration programs. For this reason, the past few years have seen an increased interest in the implications of integrin receptors in cancer biology and tumor cell aggression. This review considers the potential role of integrins in cancer and also addresses why integrins are present attractive targets for drug design. It discusses of the several properties of the integrin-based chemotherapeutic agents currently under consideration clinically and provides an insight into cancer drug development using integrin as a target.

Radiation-guided P-selectin antibody targeted to lung cancer

PURPOSE

P-selectin expression is significantly increased in tumor microvasculature following exposure to ionizing radiation. The purpose of this study was to image radiation-induced P-selectin expression in vivo using optical imaging and gamma camera imaging in a heterotopic lung cancer model by using ScFv antibodies to P-selectin.

PROCEDURES

In vitro studies using endothelial cells were done using 3 Gy radiation and selected ScFv antibodies to P-selectin. In vivo studies were performed using Lewis lung carcinoma cells subcutaneously injected into the hind limbs of nude mice. Mice were treated with 6 Gy radiation and sham radiation 10 days post-inoculation. P-selectin expression was assessed with near-infrared imaging using Cy7 labeled antibody, and gamma camera imaging using( 111)In-DTPA labeled antibody.

RESULTS

In vitro studies showed antibody binding to P-selectin in radiation treated endothelial cells. In vivo optical imaging and gamma camera imaging studies showed significant tumor-specific binding to P-selectin in irradiated tumors compared to unirradiated tumors.

CONCLUSIONS

Optical imaging and gamma camera imaging are effective methods for visualizing in vivo targeting of radiation-induced P-selectin in lung tumors. This study suggests that fluorescent-labeled and radiolabeled ScFv antibodies can be used to target radiation-induced P-selectin for the tumor-specific delivery of therapeutic drugs and radionuclides in vivo.

Radionuclide carriers for targeting of cancer

This review describes strategies for the delivery of therapeutic radionuclides to tumor sites. Therapeutic approaches are summarized in terms of tumor location in the body, and tumor morphology. These determine the radionuclides of choice for suggested targeting ligands, and the type of delivery carriers. This review is not exhaustive in examples of radionuclide carriers for targeted cancer therapy. Our purpose is two-fold: to give an integrated picture of the general strategies and molecular constructs currently explored for the delivery of therapeutic radionuclides, and to identify challenges that need to be addressed. Internal radiotherapies for targeting of cancer are at a very exciting and creative stage. It is expected that the current emphasis on multidisciplinary approaches for exploring such therapeutic directions should enable internal radiotherapy to reach its full potential.

Combined effects of radiotherapy and endostatin gene therapy in melanoma tumor model

PEgr-Endostatin-EGFP plasmid was constructed to investigate its expression properties induced by ionizing irradiation and the effect of pEgr-Endostatin-EGFP gene-radiotherapy on melanoma tumor-bearing mice. The pEgr-Endostatin-EGFP plasmid was transfected into B16 cell line with liposome. The expression property of endostatin was investigated by RT-PCR and that of EGFP was detected by flow cytometry. Tumor-bearing mice were treated by the plasmid injection and 2 Gy X-irradiation of three fractions. Tumor growth was observed for 18 days after treatment. Change of tumor capillary formation was measured with histochemistry assay at the end of the experiment. The expression of GFP in B16 melanoma cells was detected after X-irradiation with 0.05-20 Gy. Time-course studies showed that the expression of GFP in B16 cells reached its peak at 8 h after irradiation with 2 Gy. The injection of pEgr-Endostatin-EGFP recombinant plasmid into the implanted B16 melanoma in C57BL/6J mice followed by local X-irradiation could significantly inhibit tumor growth with inhibition of intratumor micro-vessel density. The inhibitory effect of pEgr-Endostatin-EGFP gene-radiotherapy on the growth of B16 melanoma is correlated with the marked decrease of intratumoral vascularization. The present data point to the potential of an anti-angiogenic approach in gene-radiotherapy of cancer.

Adhesion molecules in radiotherapy

Recent studies have documented changes in adhesion molecule expression and function after exposure to ionizing radiation. Adhesion molecules mediate cell-cell and cell-matrix interactions and are essential for a variety of physiological and pathological processes including maintenance of normal tissue integrity as well as tumor development and progression. Consequently, modulation of adhesion molecules by radiation may have a role in radiation-induced tumor control and normal tissue damage by interfering with cell signaling, radioresistance, metastasis, angiogenesis, carcinogenesis, immune response, inflammation and fibrosis. In addition, the interactions of radiation with adhesion molecules could have a major impact in developing new strategies to increase the efficacy of radiation therapy. Remarkable progress has been made in recent years to design targeted drug delivery to radiation-up-regulated adhesion molecules. Furthermore, the inhibition of adhesion, migration, invasion and angiogenesis by blocking adhesion receptors may represent a new therapeutic approach to improve tumor control and decrease radiation toxicity. This review is focused on current data concerning the mechanistic interactions of radiation with adhesion molecules and the possible clinical-pathological implications in radiotherapy.

Selective delivery of therapeutic agents for the diagnosis and treatment of cancer

Research activity aimed towards achieving specific and targeted delivery of cancer therapeutics has expanded tremendously in the last decade, resulting in new ways of directing drugs to tumours, as well as new types of drugs. The available strategies exploit differences in the nature of normal and cancer cells and their microenvironment. The discovery and validation of cancer-associated markers, as well as corresponding ligands, is pivotal for developing selective delivery technology for cancer. Although most current clinical trials are either monoclonal antibody- or gene-based, methodological advances in combinatorial libraries of peptides, single chain variable fragments and small organic molecules are expected to change this scenario in the near future. Nanotechnology platforms today allow systematic and modular combinations of therapeutic agents and tumour-binding moieties that may generate novel, personalised agents for selective delivery in cancer. This paper discusses recent developments and future prospects of targeted delivery technologies in the management of cancer.

Alcalase‐Catalyzed, Kinetically Controlled Synthesis of a Precursor Dipeptide of RGDS in Organic Solvents

The protease-catalyzed, kinetically controlled synthesis of a precursor dipeptide of RGDS, Z-Asp-Ser-NH2 in organic solvents was studied. Alcalase, an industrial alkaline protease, was used to catalyze the synthesis of the target dipeptide in water-organic cosolvents systems with Z-Asp-OMe as the acyl donor and Ser-NH2 as the nucleophile. Acetonitrile was selected as the organic solvent from acetonitrile, ethanol, methanol, DMF, DMSO, ethyl acetate, 2-methyl-2-propanol, and chloroform tested under the experimental conditions. The conditions of the synthesis reaction were optimized by examining the effects of several factors, including water content, temperature, pH, and reaction time on the Z-Asp-Ser-NH2 yields. The optimum conditions are pH 10.0, 35 degrees C, in acetonitrile/Na2CO3-NaHCO3 buffer system (85:15, v/v), 6 h, with a dipeptide yield of 75.5%.

Radiation-guided drug delivery to tumor blood vessels results in improved tumor growth delay

Tumor blood vessels are biological targets for cancer therapy. In this study, a tumor vasculature targeting system that consisted of liposomes and lectin (WGA) was built. Liposomes were used to carry a number of liposome-friendly anti-tumoral agents along with WGA, a lectin which posseses a specific affinity for binding to inflamed endothelial cells. In order to target tumor vasculature, inflammation of endothelial cells was induced by radiation. Because ionizing radiation induces an inflammatory response in tumor vasculature, lectin-conjugates were utilized to determine whether radiation can be used to target drug delivery to tumor vessels. Wheat germ agglutinin (WGA) is one such lectin that binds to inflamed microvasculature. WGA was conjugated to liposomes containing cisplatin and administered to tumor bearing mice. Tumor growth delay was used to analyze the efficacy of cytotoxicity. FITC-conjugated WGA accumulated within irradiated tumor microvasculature. WGA was conjugated to liposomes and labeled with 111In. This demonstrated radiation-inducible tumor-selective binding. WGA-liposome-conjugates were loaded with Cisplatin and administered to mice bearing irradiated tumors. Tumors treated with a combination of liposome encapsulated cisplatin together with radiation showed a significant increase in tumor growth delay as compared to radiation alone. These findings demonstrate that ionizing radiation can be used to guide drug delivery to tumor microvasculature.

A novel RGDS-analog inhibits angiogenesis in vitro and in vivo

In this study the anti-angiogenic action of a novel non-peptide RGDS-analog named RAM was tested in vitro and in vivo. RAM inhibited FGF-2-induced chemotaxis by 80% in an adhesion-independent way. Further, it induced HUVEC-apoptosis in collagen-seeded HUVEC, indicating that such pro-apoptotic effect was adhesion-independent. In vivo studies revealed that RAM inhibited FGF-2 induced angiogenesis by 60% in the mouse Matrigel-assay and in the chicken-egg chorion-allantoic membrane assay. Finally, RAM was markedly more stable in serum as compared to the template RGDS and after 24 h incubation in 100% serum was significantly more active than RGDS. Taken together these results show that RAM exerts anti-chemotactic and pro-apoptotic effects, by an unexpected adhesion-independent mechanism, as we have recently shown for the template RGDS molecule [Blood 103 (2004) 4180], and has in vivo relevant anti-angiogenic properties, with marked stability in serum; therefore, RAM represents a novel promising anti-angiogenic molecule.

Endogenous production of TNFalpha is a potent trigger of NFkappaB activation by irradiation in human monocytic cells THP-1

Irradiation causes DNA damage and induces neoplastic transformation. In response to irradiation, cells induce genes or activate proteins that protect themselves from the external insult. Nuclear factor kappaB (NFkappaB) activates transcription of target genes and plays important roles in inflammation. We studied the mechanism(s) for activation of NFkappaB by irradiation in human monocytic cells THP-1. Gel mobility shift assays showed that irradiation stimulated the NFkappaB-DNA binding activity of nuclear extracts from these cells. Western blot analysis using polyclonal antibody against phosphorylated IkappaB protein showed that irradiation increased the levels of phosphorylated IkappaB. The production of tumor necrosis factor alpha (TNFalpha) was stimulated by irradiation in these cells. Treatment with exogenously added TNFalpha also stimulated the NFkappaB binding activity with concomitant degradation of IkappaB. Further study found that the activation of NFkappaB by irradiation was inhibited by a neutralizing anti-TNFalpha antibody. Macrophages from TNFalpha-deficient mice were also defective in the irradiation-induced activation of NFkappaB. These results indicate that endogenous production of TNFalpha in macrophages/monocytes is required for NFkappaB activation by irradiation. Our data also suggest that TNFalpha in monocytes/macrophages exposed to irradiation is involved in signal transduction network initiation.

Differences in ICAM-1 and TNF-alpha expression between large single fraction and fractionated irradiation in mouse brain

PURPOSE

To elucidate the brain molecular response to irradiation. The expression of the intercellular adhesion molecule (ICAM-1) and tumour necrosis factor-alpha (TNF-alpha) in the mouse brain was compared after single-dose and fractionated whole-brain irradiation.

MATERIALS AND METHODS

Mice received a single dose of 2, 10 or 20 Gy or a fractionated dose (2 Gy day(-1)) of 10, 20 or 40 Gy. ICAM-1, and TNF-alpha mRNA expression were quantified by the highly sensitive real-time polymerase chain reaction technique. Expression of ICAM-1 protein was quantified by dual-labelled monoclonal antibody assay.

RESULTS

After a 20-Gy single dose, there was an increase in ICAM-1 and TNF-alpha mRNA levels (14- and 11-fold, respectively) as well as a significant increase in the level of ICAM-1 protein (p=0.0243). The expression of ICAM-1 and TNF-alpha mRNA increased at the end of the 40-Gy fractionated regimen (3.55- and 2.30-fold, respectively).

CONCLUSIONS

The molecular response of the brain to single-dose irradiation was rapid, while its response to fractionated irradiation was slow. This finding is consistent with clinical observations and could be of use when designing strategies to mitigate radiation sequelae.

Transcriptional Targeting in Cancer Gene Therapy

Cancer gene therapy has been one of the most exciting areas of therapeutic research in the past decade. In this review, we discuss strategies to restrict transcription of transgenes to tumour cells. A range of promoters which are tissue-specific, tumour-specific, or inducible by exogenous agents are presented. Transcriptional targeting should prevent normal tissue toxicities associated with other cancer treatments, such as radiation and chemotherapy. In addition, the specificity of these strategies should provide improved targeting of metastatic tumours following systemic gene delivery. Rapid progress in the ability to specifically control transgenes will allow systemic gene delivery for cancer therapy to become a real possibility in the near future.

The Promise of Integrins as Effective Targets for Anticancer Agents

This review will briefly describe integrin function, address why integrins are attractive targets for chemotherapeutic drug design, and discuss some ongoing studies aimed at inhibiting integrin activity. Integrins are cell surface heterodimeric receptors. They modulate many cellular processes including: growth, death (apoptosis), adhesion, migration, and invasion by activating several signaling pathways. Many potential chemotherapeutic agents target integrins directly (eg, polypeptides, monoclonal antibodies, adenovirus vectors). These agents may be clinically useful in controlling the metastatic spread of cancer.