[Inflammatory and immune biomarkers of radiation response]. / Biomarqueurs inflammatoires et immunologiques de réponse à la radiothérapie.

In radiotherapy, the treatment is adapted to each individual to protect healthy tissues but delivers most of time a standard dose according to the tumor histology and site. The only biomarkers studied to individualize the treatment are the HPV status with radiation dose de-escalation strategies, and tumor hypoxia with dose escalation to hypoxic subvolumes using FMISO- or FAZA-PET imaging. In the last decades, evidence has grown about the contribution of the immune system to radiation tumor response. Many preclinical studies have identified some of the mechanisms involved. In this context, we have realised a systematic review to highlight potential inflammatory and immune biomarkers of radiotherapy response. Some are inside the tumor microenvironment, as lymphocyte infiltration or PD-L1 expression, others are circulating biomarkers, including different types of hematological cells, cytokines and chemokines.

FLT-PET imaging of radiation responses in murine tumors.

BACKGROUND: 3'-[F-18]fluoro-3'-deoxythymidine (FLT) traces thymidine phosphorylation catalyzed by thymidine kinase during cell proliferation. Knowing the rate of cell proliferation during cancer treatment, such as radiation therapy, would be valuable in assessing whether tumor recurrence is likely and might indicate the need for additional treatments. However, the relationship between FLT kinetics and the effects of radiation is not well-understood. Nor has the method for optimal quantification of FLT uptake within the irradiated tumor microenvironment been extensively examined. MATERIALS AND METHODS: We performed dynamic FLT-positron emission tomography (PET) studies (60 min) on 22 mice implanted subcutaneously with syngeneic mammary MCaK tumors bilaterally in the shoulder area. A day before the FLT-PET imaging, the tumor on the right side was irradiated with a single dose (0, 2.5, 5, 10, or 20 Gy) or with fractionated exposures (4x2.5 Gy given in 12 h intervals). Standardized uptake value (SUVs) of FLT on tumors at 10 and 60 min post injection were calculated; model fitting was used to estimate the kinetic parameters. Significant radiation-induced changes were shown by comparing the irradiated tumor with the control tumor in the same animal and by comparing it to nonirradiated mice. The effect of radiation on MCaK cell cycle parameters and FLT uptake was also examined in vitro. RESULTS: In vivo FLT kinetics were sensitive to radiation doses of 5 Gy and higher (administered 1 day earlier), as judged by SUV semiquantitative measures and by modeling. Single irradiation with 10 Gy had greater impact on SUVs and kinetic parameters than fractionated exposures. Overall, the uptake constant Ki appeared to be the best marker for these radiation effects. FLT uptake by irradiated cells in vitro at various doses gave similar findings, and the in vitro FLT uptake correlated well with Ki. Radiation-induced G2/M arrest appeared to influence FLT uptake, and this was more pronounced after single than fractionated doses. CONCLUSION: The kinetics of FLT uptake into murine mammary tumors was altered 1 day after radiation treatment. The dose-dependent response correlated well with in vitro FLT cellular uptake. Parameters (e.g., Ki) derived from FLT kinetics are expected to be useful for assessing the efficacy of irradiation treatment of tumors.

Tetracycline-regulated intratumoral expression of interleukin-3 enhances the efficacy of radiation therapy for murine prostate cancer.

The aim of this study was to investigate means of increasing the efficiency with which cancer cell death following local radiation therapy (RT) is translated into the generation of tumor immunity since, if this were to be achieved, it would be expected to enhance the rates of disease-free recurrence and survival. Our investigations centered around the use of interleukin-3 (IL-3), expressed intratumorally using an inducible adenoviral vector, to alter the immunogenicity of established murine TRAMP-C1 prostate cancer receiving a course of fractionated local RT (7 Gy per fraction per day for 5 days). Because high systemic levels of IL-3 can be associated with toxicity, a tetracycline-regulated gene delivery system was employed. The results show that while intratumoral IL-3 expression or RT alone caused a modest delay in TRAMP-C1 tumor growth, the combination was synergistic with 50% of mice being cured and developing a long-term, tumor-specific state of immunity. Immunological analyses performed on splenic lymphocytes demonstrated that, compared to RT or IL-3 alone, combined treatment significantly increased the number of tumor-specific IFN-gamma-secreting and cytotoxic T cells. The study demonstrates that tetracycline-regulated IL-3 gene expression within tumors can enhance the immune response to prostate cancer and this can augment the efficacy of a course of RT without additional side effects.

A new approach to the validation of tissue microarrays.

Although tissue microarrays (TMA) have been widely used for a number of years, it is still not clear how many core biopsies should be taken to determine a reliable value for percentage positivity or how much heterogeneity in marker expression influences this number. The first aim of this study was to validate the human visual semi-quantitative scoring system for positive staining of tumour tissue with the exact values determined from computer-generated images. The second aim was to determine the minimum number of core biopsies needed to estimate percentage positivity reliably when the immunohistochemical staining pattern is heterogeneous and scored in a non-binary way. Tissue sections from ten colorectal cancer specimens were stained for carbonic anhydrase IX (CA IX). The staining patterns were digitized and 400 artificial computer-generated images were generated to test the accuracy of the human scoring system. To determine the minimal number of core biopsies needed to account for tumour heterogeneity, 50 (artificial) core biopsies per section were taken from the tumoural region of the ten digitally recorded full tissue sections. Based on the semi-quantitative scores from the 50 core biopsies per section, 2500 x n (n = 1-10 core biopsies) experimental core biopsies were then generated and scores recorded. After comparison with field-by-field analysis from the tumoural region of the whole tissue section, the number of core biopsies that need to be taken to minimize the influence of heterogeneity could be determined. In conclusion, visual scoring accurately estimated the percentage positivity and the percentage tumour present in a section, as judged by comparison with the artificial images. The exact number of core biopsies that has to be examined to determine tumour marker positivity using TMAs is affected by the degree of heterogeneity in the expression pattern of the protein, but for most purposes at least four is recommended.

alpha-Fetoprotein-specific tumor immunity induced by plasmid prime-adenovirus boost genetic vaccination.

alpha-Fetoprotein (AFP) is a potential target for immunotherapy in hepatocellular carcinoma; both the murine and human T-cell repertoires can recognize AFP-derived epitopes in the context of the MHC. Protective immunity can be generated with AFP-engineered dendritic cell-based vaccines. We now report a DNA-based immunization strategy using a prime-boost approach: coadministration of plasmid DNA encoding murine AFP and murine granulocyte-macrophage colony-stimulating factor followed by boosting with an AFP-expressing nonreplicating adenoviral vector. This immunization strategy can elicit a high frequency of Th1-type AFP-specific cells leading to tumor protective immunity in mice at levels comparable with AFP-engineered dendritic cells. This cell-free mode of immunization is better suited for large-scale vaccine efforts for patients with hepatocellular carcinoma.

CD40 cross-linking bypasses the absolute requirement for CD4 T cells during immunization with melanoma antigen gene-modified dendritic cells.

Genetic immunization of mice with dendritic cells (DCs) engineered to express a melanoma antigen generates antigen-specific, MHC-restricted, CD4-dependent protective immune responses. We wanted to determine the role of CD4 cells and CD40 ligation of MART-1 gene-modified DC in an animal model of immunotherapy for murine melanoma. CD4 knock-out (CD4KO) or antibody-depleted mice were immunized with DC adenovirally transduced with the MART-1 gene (AdVMART1/DC) with or without CD40 cross-linking. Tumor protection was absent in CD4-depleted mice, but protection was reestablished when the CD40 receptor was engaged using three different constructs. Transduction of DCs with vectors expressing the Th1 cytokines interleukin (IL)-2, IL-7, or IL-12 could not reproduce the CD40-mediated maturation signal in this model. CD8 T-cell depletion in CD4KO mice immunized with CD40-ligated DCs abrogated the protective response. Pooled analysis of CD40 cross-linking of AdVMART1/DC administered to wild-type C57BL/6 mice revealed an overall enhancement of antitumor immunity. However, this effect was inconsistent between replicate studies. In conclusion, maturation of AdVMART1-transduced DCs through the CD40 ligation pathway can promote a protective CD8 T-cell-mediated immunity that is independent of CD4 T-cell help.

The role of tumor necrosis factor signaling pathways in the response of murine brain to irradiation.

Late effects after radiotherapy for brain tumors can be severe and tend to limit the efficacy of this treatment modality. The mechanisms governing the development of late radiation-induced lesions in the brain are not clear, but they are preceded by cycles of molecular and cellular events including production of cytokines, one of which is tumor necrosis factor (TNF)-alpha. There is literature to support possible roles for TNF-alpha as a contributor to edema, gliosis, and demyelination in the brain, all of which are histopathologically associated with radiation-induced brain damage. We have examined the role of TNF-alpha signaling in the response to brain irradiation using TNFRp55- or TNFRp75-deficient and control mice. Mice lacking TNFRp75 exhibited increased early radiation-induced apoptosis in putative stem cell regions of the brain. At 1 month, they had decreased proliferative responses in the same regions, and by 3 months they were demonstrating dose-dependent seizures and other severe neurological abnormalities that were not seen in control or TNFRp55-/- mice. Seizure activity correlated with the onset of extensive demyelination, and by 6 months, levels of myelin basic protein in irradiated TNFRp75-/- mice were approximately 40% of those seen in the other two strains; the animals were moribund and had to be euthanized. These observations indicate that radiation-induced TNF-alpha, acting through TNFRp75, protects against the development of late complications of brain irradiation.

Molecular pathways that modify tumor radiation response.

Aberrant expression of signal transduction molecules in pathways controlling cell survival, proliferation, death, or differentiation are a common feature of all tumors. The identification of the molecules that are involved allows the development of novel tumor-specific strategies. Not surprisingly, targeting these pathways often also results in radiosensitization. The efficacy of such directed therapies may, however, be limited by the heterogeneity and the multiple mutations that are associated with the cancerous state. A more robust alternative may be to target global mechanisms of cellular control. The ubiquitin/proteasome degradation pathway is one candidate for such therapeutic intervention. This pathway is the main posttranscriptional mechanism that controls levels of many short-lived proteins involved in regulation of cell cycle progression, DNA transcription, DNA repair, and apoptosis. Many of these proteins are involved in various malignancies and/or radiation responses. In recent years, proteasome inhibitors have gained interest as a promising new group of antitumor drugs. PS-341, a reversible inhibitor of proteasome chymotryptic activity, is currently being tested in phase I clinical trials. In this study, we show that proteasome inhibition by PS-341 can alter cellular radiosensitivity in vitro and in vivo, in addition to having direct antitumor effects.

The proteasome in cancer biology and treatment.

During the last 30 years, investigation of the transcriptional and translational mechanisms of gene regulation has been a major focus of molecular cancer biology. More recently, it has become evident that cancer-related mutations and cancer-related therapies also can affect post-translational processing of cellular proteins and that control exerted at this level can be critical in defining both the cancer phenotype and the response to therapeutic intervention. One post-translational mechanism that is receiving considerable attention is degradation of intracellular proteins through the multicatalytic 26S proteasome. This follows growing recognition of the fact that protein degradation is a well-regulated and selective process that can differentially control intracellular protein expression levels. The proteasome is responsible for the degradation of all short-lived proteins and 70-90% of all long-lived proteins, thereby regulating signal transduction through pathways involving factors such as AP1 and NFKB, and processes such as cell cycle progression and arrest, DNA transcription, DNA repair/misrepair, angiogenesis, apoptosis/survival, growth and development, and inflammation and immunity, as well as muscle wasting (e.g. in cachexia and sepsis). In this review, we discuss the potential involvement of the proteasome in both cancer biology and cancer treatment.

Can short-term administration of dexamethasone abrogate radiation-induced acute cytokine gene response in lung and modify subsequent molecular responses?

PURPOSE: To investigate the effects of short-term administration of dexamethasone (DEX) on radiation-induced responses in the mouse lung, focusing on expression of pro-inflammatory cytokine and related genes. METHODS AND MATERIALS: At indicated times after thoracic irradiation and/or drug treatment, mRNA expression levels of cytokines (mTNF-alpha, mIL-1 alpha, mIL-1 beta, mIL-2, mIL-3, mIL-4, mIL-5, mIL-6, mIFN-gamma) and related genes in the lungs of C3H/HeN mice were measured by RNase protection assay. RESULTS: Radiation-induced pro-inflammatory cytokine mRNA expression levels in lung peak at 6 h after thoracic irradiation. DEX (5 mg/kg) suppresses both basal cytokine mRNA levels and this early response when given immediately after irradiation. However, by 24 h, in mice treated with DEX alone or DEX plus radiation, there was a strong rebound effect that lasted up to 3 days. Modification of the early radiation-induced response by DEX did not change the second wave of cytokine gene expression in the lung that occurs at 1 to 2 weeks, suggesting that early cytokine gene induction might not determine subsequent molecular events. A single dose of DEX attenuated, but did not completely suppress, increases in cytokine mRNA levels induced by lipopolysaccharide (2.5 mg/kg) treatment, but, unlike with radiation, no significant rebound effect was seen. Five days of dexamethasone treatment in the pneumonitic phase also inhibited pro-inflammatory cytokine gene expression and, again, there was a rebound effect after withdrawal of the drug. CONCLUSIONS: Our findings suggest that short-term use of dexamethasone can temporarily suppress radiation-induced pro-inflammatory cytokine gene expression, but there may be a rebound after drug withdrawal and the drug does little to change the essence and course of the pneumonitic process.

T cell responses to HLA-A*0201-restricted peptides derived from human alpha fetoprotein.

alpha fetoprotein (AFP)-derived peptide epitopes can be recognized by human T cells in the context of MHC class I. We determined the identity of AFP-derived peptides, presented in the context of HLA-A*0201, that could be recognized by the human (h) T cell repertoire. We screened 74 peptides and identified 3 new AFP epitopes, hAFP(137-145), hAFP(158-166), and hAFP(325-334), in addition to the previously reported hAFP(542-550.) Each possesses two anchor residues and stabilized HLA-A*0201 on T2 cells in a concentration-dependent class I binding assay. The peptides were stable for 2-4 h in an off-kinetics assay. Each peptide induced peptide-specific T cells in vitro from several normal HLA-A*0201 donors. Importantly, these hAFP peptide-specific T cells also were capable of recognizing HLA-A*0201(+)/AFP(+) tumor cells in both cytotoxicity assays and IFN-gamma enzyme-linked immunospot assays. The immunogenicity of each peptide was tested in vivo with HLA-A*0201/K(b)-transgenic mice. After immunization with each peptide emulsified in CFA, draining lymph node cells produced IFN-gamma on recognition of cells stably transfected with hAFP. Furthermore, AFP peptide-specific T cells could be identified in the spleens of mice immunized with dendritic cells transduced with an AFP-expressing adenovirus (AdVhAFP). Three of four AFP peptides could be identified by mass spectrometric analysis of surface peptides from an HLA-A*0201 human hepatocellular carcinoma (HCC) cell line. Thus, compelling immunological and physiochemical evidence is presented that at least four hAFP-derived epitopes are naturally processed and presented in the context of class I, are immunogenic, and represent potential targets for hepatocellular carcinoma immunotherapy.

Ionizing radiation affects 26s proteasome function and associated molecular responses, even at low doses.

BACKGROUND AND PURPOSE: Ionizing radiation is known to activate certain signal transduction pathways, the regulation of which could involve post-transcriptional as well as transcriptional mechanisms. One of the most important post-transcriptional pathways in eukaryotic cells is the ATP- and ubiquitin-dependent degradation of proteins by the 26s proteasome. This process controls initiation of many cellular stress responses, as well as inflammatory responses under control of the transcription factor NF-kappaB. The literature on the relationship between radiation and inflammation seems somewhat paradoxical. At high doses, radiation is generally pro-inflammatory. On the other hand, low dose radiation has a long history of use in the treatment of inflammatory disease. This suggests the involvement of multiple mechanisms that may operate differentially at different dose levels. MATERIALS AND METHODS: In this paper, the ability of different doses of ionizing radiation to directly affect 26s proteasome activity was tested in ECV 304 cells. Proteasome activity, IkappaBalpha protein levels, and NF-kappaB activation were monitored. RESULTS: Inhibition of chymotrypsin-like 20s and 26s proteasome activity was observed immediately after low- and high-dose irradiation either of cells or purified proteasomes. The inhibitory effect was independent of the availability of the known endogenous proteasome inhibitor heat shock protein 90 (hsp90). Levels of IkappaBalpha, a physiological 26s proteasome substrate, were increased only at low doses (0.25 Gy) and unaltered at higher doses whereas only the highest doses (8 and 20 Gy) activated NF-kappaB. CONCLUSIONS: We conclude that the proteasome is a direct target of ionizing radiation and suggest that inhibition of proteasome function provides a molecular framework within which low dose anti-inflammatory effects of radiation, and radiation-induced molecular responses in general, should be considered.

Adenovirus-interleukin-12-mediated tumor regression in a murine hepatocellular carcinoma model is not dependent on CD1-restricted natural killer T cells.

The cytokine interleukin-12 (IL-12) has shown potent antitumor activity in several tumor models. Recently, natural killer (NK) T cells have been proposed to mediate the antitumor effects of IL-12. In this study, the antitumor response of IL-12 was investigated in a gene therapeutic model against s.c. growing mouse hepatocellular carcinomas using an adenoviral vector expressing murine IL-12 (AdVmIL-12). An adenoviral-based system was chosen because of the ability of adenoviruses to transduce dividing and nondividing cells and because of their high transduction efficiencies. Our goals were to examine the efficacy of AdVmIL-12 in a hepatocellular carcinoma model and to investigate the mechanism of the AdVmIL-12-mediated antitumor response with specific interest in the role of NK T cells. Our studies demonstrate that intratumoral AdVmIL-12-mediated regression of s.c. hepatocellular tumors is associated with rapid antitumor responses. AdVmIL-12 treatment was associated with an immune cellular infiltrate consisting of CD4 and CD8 T lymphocytes, macrophages, NK cells, and NK T cells. Antibody ablation of CD4 and CD8 T cells and use of NK cell-defective beige mice failed to abrogate the response to AdVmIL-12. Studies in T-cell- and B-cell-deficient severe combined immunodeficient and recombinase activating gene-2-deficient mice and T-cell-, B-cell-, and NK cell-defective severe combined immunodeficient/beige mice also failed to abrogate this response. AdVmIL-12 retained potent antitumor activity in mice with specific genetic defects in immune cellular cytotoxicity (perforin knockout mice) and costimulation (CD28 knockout mice). Use of mice with specific NK T cell deficiencies, Valpha14 T-cell receptor and CD1 knockout mice, also failed to abrogate the response to AdVmIL-12. Histological and immunohistochemical studies of AdVmIL-12-treated tumors showed extensive inhibition of neovascularization and a marked decrease in factor VIII-stained endothelial cells. Our studies indicate that the antitumor response of AdVmIL-12 is independent of direct cytotoxic cellular immunity (specifically, the function of NK T cells) and suggest that the initial mechanisms of AdVmIL-12-mediated tumor regression involve inhibition of angiogenesis.

Mechanisms mediating the effects of IL-3 gene expression on tumor growth.

IL-3 gene expression within tumors leads to host-cell infiltration, particularly by macrophages, slower tumor growth, and enhanced immunogenicity. Surprisingly, tumor-associated macrophages (TAMs) from within FSAN-JmIL3 tumors had decreased expression of TNF-alpha and iNOS. On short-term culture, TAMs from FSAN-JmIL3 tumors regained their capacity to produce TNF-alpha and NO, indicating that they were primed in vivo. In vitro experiments were unable to demonstrate differences between FSAN-JmIL3 and FSAN tumor cells in their ability to stimulate TNF-alpha production by TAMs. In the absence of evidence that TAM activation was responsible for the slower growth of FSAN-JmIL3 tumors, the response of tumor cells to these effector molecules was studied. TNF-alpha and NO were cytotoxic for FSAN-JmIL3 cells but growth stimulatory for FSAN. These tumor-related phenotypic changes may contribute as much if not more than functional changes in host infiltrating cells to the slower growth of FSAN-JmIL3 tumors in vivo.

Effect of macrophage-derived apolipoprotein E on established atherosclerosis in apolipoprotein E-deficient mice.

Apolipoprotein E-deficient (apoE(-/-)) mice have hyperlipidemia and develop spontaneous atherosclerosis in a time-dependent manner. Although macrophage-derived apoE has been shown to prevent the development of atherosclerosis in apoE(-/-) mice, whether it would induce regression of established atherosclerosis is unknown. To determine this, 8-week-old apoE(-/-) mice were transplanted with apoE(+/+) bone marrow. Four weeks after transplantation, when plasma cholesterol levels had reached normal levels, a group of mice (n=12) were killed and their aortic lesions were measured and used as a baseline to judge regression. Twelve and 20 weeks after transplantation, aortic lesion areas of the mice were 9340+/-2184 micrometer(2) (mean+/-SEM, n=8) and 12 211+/-1433 micrometer(2) (n=9), respectively, values not significantly different from the lesion areas of the baseline mice (12 347+/-2487 micrometer(2); n=12, P>0.05). In contrast, apoE(-/-) mice reconstituted with apoE(-/-) bone marrow developed severe atherosclerotic lesions (453 036+/-29 767 micrometer(2), n=7) 20 weeks after transplantation. These data suggest that macrophage-derived apoE was insufficient to induce significant regression of established atherosclerotic lesions in apoE(-/-) mice, although it was sufficient to eliminate hypercholesterolemia and prevent progression of aortic lesions.