A comparison of medical education in Germany and the United States: from applying to medical school to the beginnings of residency

Both Germany and the United States of America have a long tradition of science and medical excellence reaching back as far as the nineteenth century. The same tribute must be paid to the medical educational system in both countries. Despite significant initial similarities and cross-inspiration, the paths from enrolling in a medical university to graduating as a medical doctor in Germany and the US seem to have become much different. To fill a void in literature, the authors’ objective therefore is to delineate both structures of medical education in an up-to-date review and examine their current differences and similarities. Recent medical publications, legal guidelines of governmental or official organizations, articles in media, as well as the authors’ personal experiences are used as sources of this report.

Tuition loans of over $200,000 are not uncommon for students in the US after graduating from medical schools, which are often private institutions. In Germany, however, the vast majority of medical universities are tax-funded and, for this reason, free of tuition. Significant differences and surprisingly multiple similarities exist between these two systems, despite one depending on government and the other on private organizations. Germany currently employs an integrated medical curriculum that typically begins right after high school and consists of a 2-year long pre-clinical segment teaching basic sciences and a 4-year clinical segment leading medical students to the practical aspects of medicine. On the other hand, the US education is a two-stage process. After successful completion of a Bachelor’s degree in college, an American student goes through a 4-year medical program encompassing 2 years of basic science and 2 years of clinical training. In this review, we will address some of these similarities and major differences.

Optimizing adenoviral transduction of endothelial cells under flow conditions

PURPOSE

To target adenoviral vectors to cells of the vasculature and shielding vectors from inactivation by the immune system.

METHODS

Complexes of reporter gene expressing adenoviral vectors with positively charged magnetic nanoparticles were formed by electrostatic interaction in presence or absence of additional negatively charged poly(ethylene glycol)-based polymer. Transduction of HUVEC was analyzed in vitro under flow. Protection from inactivation by the immune system was analyzed by pre-incubation of AdV and complexes with neutralizing antibodies and subsequent reporter protein analysis of infected cells.

RESULTS

Physical association of AdV with MNP and polymers was demonstrated by radioactive labelling of components and co-sedimentation in a magnetic field. Ad-MNP+/-polymer resulted in efficient transduction of HUVEC, depending on MOI and flow rate in presence of magnetic field, whereas no transduction was observed without complex formation with MNP or in absence of magnetic field. Association with MNP did result in protection from neutralizing antibodies, with slightly increased protection provided by the polymer.

CONCLUSIONS

Complex formation of AdV with MNP is a viable means for targeting of vectors to areas of magnetic field gradient. Additional coating with polymer might proof useful in protection from inactivation by the immune system.

Tetracycline-regulated bone morphogenetic protein 2 gene expression in lentivirally transduced primary rabbit chondrocytes for treatment of cartilage defects

OBJECTIVE

Treatment of cartilage defects is still challenging, primarily because of the poor self-healing capacity of articular cartilage. Gene therapy approaches have gained considerable attention, but, depending on the vector system used, they can lead to either limited or unrestrained gene expression, and therefore regulation of gene expression is necessary. This study was undertaken to construct an efficient tetracycline (Tet)-regulated, lentivirally mediated system for the expression of growth factor bone morphogenetic protein 2 (BMP-2) in primary rabbit chondrocytes that will allow for the induction and termination of growth factor gene expression once cartilage regeneration is complete.

METHODS

Chondrogenic ATDC5 cells and primary rabbit chondrocytes were lentivirally transduced with different tetracycline-on (Tet-On)-regulated, self-inactivating vectors for the induction of expression of enhanced green fluorescent protein (eGFP) or BMP-2, using either a 1-vector system or a 2-vector system.

RESULTS

Expression of eGFP was induced on ATDC5 cells and chondrocytes. The highest induction rate and highest level of gene expression were reached when the spleen focus-forming virus long terminal repeat promoter was used to drive the reverse transactivator expression, after the addition of doxycycline, in chondrocytes. An up to 20-fold induction of Tet-mediated BMP-2 expression was observed on ATDC5 cells. The extent of induction and expression level of BMP-2 in chondrocytes were similar between the 1-vector system- and 2-vector system-infected cells (mean +/- SD 15.5 +/- 1.1 ng/ml and 14.6 +/- 0.4 ng/ml, respectively). In addition, prolonged induction and switching-off of BMP-2 expression, as well as repeated induction, were demonstrated. Production of proteoglycans, as shown by Alcian blue staining, demonstrated the functionality of the lentivirally expressed BMP-2 under induced conditions.

CONCLUSION

The lentivirally mediated Tet-On system is an effective strategy for efficient, repeatedly inducible expression of BMP-2 in primary rabbit chondrocytes. Therefore, use of this system in in vivo experiments may be a promising approach as a treatment strategy for cartilage defects.

Physicobiochemical synergism through gene therapy and functional tissue engineering for in vitro chondrogenesis

Mechanical and chemical stimulation have been shown to enhance in vitro chondrogenesis. The aim of this study was to analyze and compare combined physicobiochemical effects. Bovine articular chondrocytes were retrovirally transduced to express bone morphogenetic protein-2 (BMP-2) or left as naïve controls. Cells were seeded in three-dimensional polyurethane scaffolds and further cultured under static conditions or exposed to dynamic compression and shear in a joint-specific bioreactor. Four groups: control (A), load (B), BMP-2-infected (C), and BMP-2-infected plus load (D) were analyzed for DNA and glycosaminoglycan (GAG) content; collagen I, II, and X; aggrecan, (cartilage oligomeric protein (COMP), superficial zone protein, matrix metalloproteinase (MMP)-3; MMP-13 mRNA; histology; and immunohistochemistry at 7, 21, and 35 days post-seeding. Synergistic effects (D) were higher than the sum of the individual treatments (B and C) for GAG/DNA, collagen II, and COMP. Histology revealed a functional organization in D including an intense safranin O staining in C and D superior to that in A and B. Immunostaining for collagen II and aggrecan was detected in C and D and was strongest in D. The results show that both stimuli augment in vitro chondrogenesis better than in controls. Biochemical manipulation proved to be predominantly more effective than load, and synergistic effects were demonstrated.

Combined reporter gene PET and iron oxide MRI for monitoring survival and localization of transplanted cells in the rat heart

There is a need for in vivo monitoring of cell engraftment and survival after cardiac cell transplantation therapy. This study assessed the feasibility and usefulness of combined PET and MRI for monitoring cell engraftment and survival after cell transplantation.

METHODS

Human endothelial progenitor cells (HEPCs), derived from CD34+ mononuclear cells of umbilical cord blood, were retrovirally transduced with the sodium iodide symporter (NIS) gene for reporter gene imaging by (124)I-PET and labeled with iron oxides for visualization by MRI. Imaging and histologic analysis were performed on 3 groups of nude rats on days 1, 3, and 7 after intramyocardial injection of 4 million HEPCs.

RESULTS

In vitro studies demonstrated stable expression of functional NIS protein and normal viability of HEPCs after transduction. On day 1, after intramyocardial transplantation, iron- and NIS-labeled HEPCs were visualized successfully on MRI as a regional signal void in the healthy myocardium and on PET as (124)I accumulation. The (124)I uptake decreased on day 3 and was undetectable on day 7, and the MRI signal remained unchanged throughout the follow-up period. Histologic analysis with CD31 and CD68 antibodies confirmed the presence of either labeled or nonlabeled control transplanted HEPCs at the site of injection on day 1 but not on day 7, when only iron-loaded macrophages were seen. Furthermore, deoxyuride-5'-triphosphate biotin nick end labeling showed extensive apoptosis at the site of transplantation.

CONCLUSION

The combination of MRI and PET allows imaging of localization and survival of transplanted HEPCs together with morphologic information about the heart. Although iron labeling rapidly loses specificity for cell viability because of phagocytosis of iron particles released from dead cells, reporter gene expression provided specific information on the number of surviving cells. This multimodality approach allows complementary analysis of cell localization and viability.

Plasminogen activator inhibitor-2, but not cystatin C, inhibits the prometastatic activity of tissue inhibitor of metalloproteinases-1 in the liver

Formation of multiple and scattered metastases in target organs, leading to disruption of organ functional integrity, is the death-determining step for most lethal cancers. In the clinic, elevated expression of tissue inhibitor of metalloproteinases-1 (TIMP-1) is often associated with increased aggressiveness of cancer. We demonstrated that elevated host expression of TIMP-1 leads to the promotion of scattered liver metastases in mice, associated with increased activity of cysteine proteases (CPs). This study aimed for reduction of TIMP-1-promoted experimental liver metastases of lacZ-tagged human fibrosarcoma cells by overexpression of cystatin C, a natural inhibitor of CPs, in the murine host. Although CP inhibition reduced TIMP-induced proteolytic activity, the TIMP-1-induced increase in total tumor cell burden in livers was not significantly reduced. However, overexpression of cystatin C in livers with elevated TIMP-1 led to the formation of large multicellular metastatic foci in 42% of the mice. This formation was associated with increased expression of plasminogen activators (PAs). Additional overexpression of plasminogen activator inhibitor-2 prevented the formation of macrometastatic foci as well as the TIMP-1-induced increase in total tumor cell burden. This demonstrates that PAs are crucial for the prometastatic activity of TIMP-1 and led to the assumption that patients with elevated TIMP-1 expression may benefit from an antiproteolytic treatment directed against PAs.

The influence of the stable expression of BMP2 in fibrin clots on the remodelling and repair of osteochondral defects

Growth factors like BMP2 have been tested for osteochondral repair, but transfer methods used until now were insufficient. Therefore, the aim of this study was to analyse if stable BMP2 expression after retroviral vector (Bullet) transduction is able to regenerate osteochondral defects in rabbits. Fibrin clots colonized by control or BMP2-transduced chondrocytes were generated for in vitro experiments and implantation into standardized corresponding osteochondral defects (n=32) in the rabbit trochlea. After 4 and 12 weeks repair tissue was analysed by histology (HE, alcian-blue, toluidine-blue), immunohistochemistry (Col1, Col2, aggrecan, aggrecan-link protein), ELISA (BMP2), and quantitative RT-PCR (BMP2, Col1, Col2, Col10, Cbfa1, Sox9). In vitro clots were also analysed by BMP2-ELISA, histology (alcian-blue), quantitative RT-PCR and in addition by electron microscopy. BMP2 increased Col2 expression, proteoglycan production and cell size in vitro. BMP2 transduction by Bullet was efficient and gene expression was stable in vivo over at least 12 weeks. Proteoglycan content and ICRS-score of repair tissue were improved by BMP2 after 4 and 12 weeks and Col2 expression after 4 weeks compared to controls. However, in spite of stable BMP2 expression, a complete repair of osteochondral defects could not be demonstrated. Therefore, BMP2 is not suitable to regenerate osteochondral lesions completely.

Impact of radiation therapy on the oncolytic adenovirus dl520: implications on the treatment of glioblastoma

BACKGROUND AND PURPOSE

Viral oncolytic therapy is emerging as a new form of anticancer therapy and has shown promising preclinical results, especially in combination with radio- and chemotherapy. We recently reported that nuclear localization of the human transcription factor YB-1 in multidrug-resistant cells facilitates E1-independent adenoviral replication. The aim of this study was to evaluate the combined treatment of the conditionally-replicating adenovirus dl520 and radiotherapy in glioma cell lines in vitro and in human tumor xenografts. Furthermore, the dependency of YB-1 on dl520 replication was verified by shRNA directed down regulation of YB-1.

METHODS AND MATERIAL

Localization of YB-1 was determined by immunostaining. Glioma cell lines LN-18, U373 and U87 were infected with dl520. Induction of cytopathic effect (CPE), viral replication, viral yield and viral release were determined after viral infection, radiation therapy and the combination of both treatment modalities. The capacity of treatments alone or combined to induce tumor growth inhibition of subcutaneous U373 tumors was tested also in nude mice.

RESULTS

Quantitative real-time PCR demonstrated that the shRNA-mediated down regulation of YB-1 is leading to a dramatic decrease in adenoviral replication of dl520. Immunostaining analysis showed that the YB-1 protein was predominantly located in the cytoplasm in the perinuclear space and less abundant in the nucleus. After irradiation we found an increase of nuclear YB-1. The addition of radiotherapy increased the oncolytic effect of dl520 with enhanced viral replication, viral yield and viral release. The oncolytic activity of dl520 plus radiation inhibited the growth of subcutaneous U373 tumors in a xenograft mouse model.

CONCLUSIONS

Radiation mediated increase of nuclear YB-1 in glioma cells enhanced the oncolytic potential of adenovirus dl520.

In vivo analysis of retroviral gene transfer to chondrocytes within collagen scaffolds for the treatment of osteochondral defects

To examine a retroviral gene transfer to chondrocytes in vitro and in vivo in tissue-engineered cell-collagen constructs articular chondrocytes from rabbits and humans were isolated and transduced with VSV.G pseudotyped murine leukemia virus-derived retroviral vectors. Viral supernatants were generated by transient transfection of 293T cells using the pBullet retroviral vector carrying the nlslacZ gene, a Moloney murine leukemia virus gag/pol plasmid and a VSV.G coding plasmid. Transduction efficiency was analyzed by fluorescence-activated-cell-sorter analysis and transduced autologous chondrocytes from rabbits were seeded on collagen-scaffolds and implanted into osteochondral defects in the patellar groove of the rabbit's femur (n=10). LacZ-expression was analyzed by X-gal staining on total knee explants and histological sections. Retroviral transduction efficiency exceeded 92.3% (SEM+/-3.5%) in rabbit articular chondrocytes, 74.7% (SEM+/-1.8%) in human articular chondrocytes and 52.7% (SEM+/-5.8%) in osteoarthritic human chondrocytes. Reporter gene expression remained high after 15 weeks in 75.7% (SEM+/-8.2%) of transduced rabbit articular chondrocytes. In vivo, intraarticular beta-galactosidase activity could be determined in the majority of implanted chondrocytes in the osteochondral defects after 4 weeks.

Cancer gene therapy with a retrovirally transduced IL2-IFNγ-secreting allogeneic tumorvaccine in patients with progressive hormone refractory prostate cancer—A phase I/II trial

5127

Background: The purpose of this study was to determine whether immunization with an allogeneic prostate carcinoma cell line, LNCaP, expressing recombinant interleukin-2 (IL-2) and interferon-γ (IFN-γ), would be tolerated and able to induce a prolongation of PSA doubling time in patients with progressive hormone refractory prostate cancer. Methods: 30 HLA-A0201-matched patients with progressive, hormone refractory prostate cancer, demonstrating three successive elevations in prostate specific antigen (PSA) values, received four intradermal injections on days 1, 15, 29 and 92, and then every 90 days as long as no tumor progression occurred. Three patients received a dose level of 7.5 million cells, 27 patients received 15 million cells. The primary efficacy criterion was the difference in PSA doubling time (PSA-DT) determined in the pre-treatment phase (before start of vaccination) and in the trial treatment phase (during vaccination). Results: The study was completed according to protocol. Immunostimulation could be demonstrated in most of the 30 patients (histological evaluation of injection site biopsies, serial ELISPOT analysis of PBMCs). During vaccination there was a significant prolongation of the PSA-DT compared to the pre-vaccination period that came to 81% (prolongation from 63 days to 114 days (p < 0.0035; ITT)). Twenty two of 30 patients (73%) responded to the vaccine administration as judged by prolongation of PSA-DT. In the majority of patients the administration was followed by a period of PSA stabilisation that was up to 641 days (“PSA plateau”). No dose limiting or autoimmune toxicities were seen. The median overall survival time since first vaccination was 981 days (mean value: 770 days). Conclusions: This vaccine strategy showed a prolongation of PSA-DT and was found to be safe and well tolerated. The results of this trial warrant the vaccine’s further clinical development.

No significant financial relationships to disclose.

Allogeneic retrovirally transduced, IL-2- and IFN-γ-secreting cancer cell vaccine in patients with hormone refractory prostate cancer—a phase I clinical trial

BACKGROUND

The purpose of this vaccine study was to determine the safety and feasibility of vaccination with an allogeneic prostate carcinoma cell line, LNCaP, expressing recombinant interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) and to evaluate the efficacy of inducing tumor-specific immune responses in HLA-A2-matched patients with hormone refractory prostate cancer (HRPC).

METHODS

In a dose-escalating phase I study, HLA-A2-matched HRPC patients received four vaccinations of irradiated allogeneic LNCaP cells retrovirally transduced to secrete IL-2 and IFN-gamma at study day 1, 15, 29 and 92 and subsequently every 91 days unless tumor progression was evident.

RESULTS

Three patients receiving the first dose level (7.5 million cells) showed no evidence of dose-limiting toxicity or vaccine-related adverse events including autoimmunity. One of three patients receiving the second dose level (15 million cells) developed a transient self-limiting grade 3 local injection site reaction (ulceration) after the eighth vaccination. Vaccine-induced immune responses against a broad array of prostate tumor associated antigens were detected in all six patients. Two of the three patients receiving the higher dose showed a decline in serum prostate-specific antigen (PSA) values of more than 50%, with one patient remaining on protocol for 3 years.

CONCLUSIONS

Immunisation with the allogeneic LNCaP/IL-2/IFN-gamma vaccine is safe and feasible without any dose-limiting toxicity or autoimmunity. A 50% PSA decline was achieved in two of the six patients. This encouraging data provides the scientific rationale for further investigation of the vaccine in a phase II trial.

Novel three-pronged strategy to enhance cancer cell killing in glioblastoma cell lines: histone deacetylase inhibitor, chemotherapy, and oncolytic adenovirus dl520

Resistance to radiation and chemotherapy remains an obstacle to the treatment of brain tumors. We have demonstrated that the replication-deficient adenovirus d1520, which lacks the E1A 13S protein, replicates efficiently and exhibits oncolytic potential in multidrug-resistant cells with nuclear localization of the human transcription factor YB-1. However, besides others, key factors regarding oncolytic virotherapy are limited tumor transduction rate and low replication efficiency. The objective of this study was to determine whether the chemotherapeutic agent irinotecan, by enhancing nuclear localization of YB-1, and the histone deacetylase inhibitor trichostatin A, by upregulating coxsackievirus-adenovirus receptor (CAR) expression, could augment replication of and cell lysis by adenovirus dl520 in glioblastomas in vitro. We found that trichostatin A upregulated CAR expression and that irinotecan caused increased nuclear localization of YB-1 in both glioblastoma cell lines. Irinotecan alone, and trichostatin A alone, enhanced replication of and cell lysis by dl520. Importantly, when combining both agents, the replication efficiency (maximum, 27-fold) and induction of cytopathic effect (maximum, 3.8-fold) of dl520 were further augmented significantly. These results support the hypothesis that the enhanced oncolytic effect of dl520, after incubation with chemotherapeutic agents, is mediated by an increased accumulation of YB-1 in the nucleus (due to irinotecan) and by upregulation of CAR (due to trichostatin A). Thus, therapy combining virotherapy, chemotherapy, and histone deacetylase inhibitor treatment is a novel approach to enhance the oncolytic efficacy of dl520.

Inhibition of the multidrug-resistant phenotype by targeting YB-1 with a conditionally oncolytic adenovirus: implications for combinatorial treatment regimen with chemotherapeutic agents

Bearing in mind the limited success of available treatment modalities for the therapy of multidrug-resistant tumor cells, alternative and complementary strategies need to be developed. It is known that the transcriptional activation of genes, such as MDR1 and MRP1, which play a major role in the development of a multidrug-resistant phenotype in tumor cells, involves the Y-box protein YB-1. Thus, YB-1 is a promising target for new therapeutic approaches to defeat multidrug resistance. In addition, it has been reported previously that YB-1 is an important factor in adenoviral replication because it activates transcription from the adenoviral E2-late promoter. Here, we report that an oncolytic adenovirus, named Xvir03, expressing the viral proteins E1B55k and E4orf6, leads to nuclear translocation of YB-1 and in consequence to viral replication and cell lysis in vitro and in vivo. Moreover, we show that Xvir03 down-regulates the expression of MDR1 and MRP1, indicating that recruiting YB-1 to the adenoviral E2-late promoter for viral replication is responsible for this effect. Thus, nuclear translocation of YB-1 by Xvir03 leads to resensitization of tumor cells to cytotoxic drugs. These data reveal a link between chemotherapy and virotherapy based on the cellular transcription factor YB-1 and provide the basis for formulating a model for a novel combined therapy regimen named Mutually Synergistic Therapy.

Second generation of meniscus transplantation: in-vivo study with tissue engineered meniscus replacement

INTRODUCTION

The options available after meniscus loss offer only limited chances for a long-term success. In the following experimental study, we investigated the effect of meniscus tissue engineering on properties of the collagen meniscus implant (CMI).

METHODS

Autologous fibrochondrocytes, obtained per biopsy from adult Merino sheep (n=25), were released from the matrix, cultured in-vitro and seeded into CMI scaffolds (n=10, group 1). Following a 3-week in-vitro culture, the tissue engineered menisci were used for autologous transplantation. Macroscopical and histological evaluation were performed in comparison with non-seeded CMI controls (n=10, group 2) and with meniscus-resected controls (n=5, group 3) after 3 weeks (each 1 animal group 1 and 2) and 3 months.

RESULTS

The lameness score did not show any difference between the groups. Meniscus tissue was found in seven knee joints (group 1), in five knee joints (group 2) and in two knee joints (group 3). The size of the transplants reduced from 25.9+/-4.5 to 20.1+/-10.8 mm (group 1) and from 25.9+/-1.5 to 14.4+/-12.5 mm (group 2). Histologically, enhanced vascularisation, accelerated scaffold re-modelling, higher content of extra-cellular matrix and lower cell number were noted in the pre-seeded menisci in comparison with non-seeded controls. Dense high-cellular fibrous scar tissue was found in two of five cases in the resection control group.

CONCLUSION

Tissue engineering of meniscus with autologous fibrochondrocytes demonstrates a macroscopic and histological improvement of the transplants. However, further development of the methods, especially of the scaffold and of the cell-seeding procedure must prove the feasibility of this procedure for human applications.

Characterization of the recombinant adenovirus vector AdYB-1: implications for oncolytic vector development

Conditionally replicating adenoviruses are a promising new modality for the treatment of cancer. However, early clinical trials demonstrate that the efficacy of current vectors is limited. Interestingly, DNA replication and production of viral particles do not always correlate with virus-mediated cell lysis and virus release depending on the vector utilized for infection. However, we have previously reported that nuclear accumulation of the human transcription factor YB-1 by regulating the adenoviral E2 late promoter facilitates viral DNA replication of E1-deleted adenovirus vectors which are widely used for cancer gene therapy. Here we report the promotion of virus-mediated cell killing as a new function of the human transcription factor YB-1. In contrast to the E1A-deleted vector dl312 the first-generation adenovirus vector AdYB-1, which overexpresses YB-1 under cytomegalovirus promoter control, led to necrosis-like cell death, virus production, and viral release after infection of A549 and U2OS tumor cell lines. Our data suggest that the integration of YB-1 in oncolytic adenoviruses is a promising strategy for developing oncolytic vectors with enhanced potency against different malignancies.

Reduction of Experimental Human Fibrosarcoma Lung Metastasis in Mice by Adenovirus-Mediated Cystatin C Overexpression in the Host

Tumor cell invasion and metastasis are associated with degradation of components of the extracellular matrix by different proteinases. Among those, papain-like cysteine proteases, such as cathepsin B, seem to play an important role, as they are associated with poor clinical outcome in different cancers. In this study, we tested whether cystatin C, a natural extracellular inhibitor of papain-like cysteine proteases, can inhibit metastasis when overexpressed at the tumor-host interface. Local overexpression of cystatin C in liver and lungs of CD1 nu/nu mice was achieved by gene transfer with a novel adenoviral construct, which also led to the presence of 60 ng/mL of cystatin C in the serum. Three days after gene transfer, these mice were challenged by i.v. inoculation of lacZ-tagged human fibrosarcoma cells (HT1080lacZ-K15), leading to the formation of experimental lung and liver metastases. In this model, formation of experimental metastatic foci correlated with expression of cathepsin B in lungs, whereas there was no correlation with metastasis to the liver. In mice overexpressing cystatin C, the number of lung metastases was significantly reduced by 92%, as compared with mice receiving control adenovirus. The efficacy of extravasation of HT1080lacZ-K15 cells into the liver was not affected, indicating the independence of this process from the activity of cysteine-cathepsins. The present report is the first evidence of successful reduction of metastasis by inhibition of cysteine-cathepsins by cystatin C overexpression in the host microenvironment. Furthermore, organ-specific protease expression during tumor-host cell interactions could affect the success of antiproteolytic intervention against metastasis.

Nerve Replacement Strategies for Cavernous Nerves

OBJECTIVE

This article reviews novel restorative therapies for cavernous nerves that may be used to replace resected cavernous nerves at the time of pelvic surgery.

METHODS

A literature-based presentation (Medline search) on current nerve replacement strategies was conducted with emphasis on neurobiological factors contributing to the restoration of erectile function after cavernous nerve injuries.

RESULTS

A promising alternative to autologous nerve grafts for extending the length of successful nerve regeneration are artificial nerve guides. The addition of neurotrophic factors, extracellular matrix components and Schwann cells has been shown to promote cavernous nerve regeneration. Neurotrophic factors can be incorporated in the scaffold or can be supplied by cells seeded into the stroma. The regenerative capacity of these cells can be further enhanced by genetic modification with neurotrophic factor encoding genes.

CONCLUSIONS

Artificial nerve guides, especially biodegradable ones containing growth-promoting factors or cells, are a promising option for the repair of cavernous nerve lesions.

Optimization of radiation controlled gene expression by adenoviral vectors in vitro

The radiation-inducible EGR-1-promoter has been used in different gene therapy approaches in order to enhance and locally restrict therapeutic efficacy. The aim of this study was to reduce nonspecific gene expression in the absence of irradiation (IR) in an adenoviral vector. Rat rhabdomyosarcoma R1H tumor cells were infected with adenoviral vectors expressing either EGFP or HSV-TK under control of the murine EGR-1 promoter/enhancer. Cells were irradiated at 0-6 Gy. Gene expression was determined by FACS-analysis (EGFP), or crystal violet staining (HSV-TK). The bovine growth hormone polyadenylation signal (BGH pA) was used as insulating sequence and was introduced upstream or upstream and downstream of the expression cassette. Infected R1H cells displayed IR dose-dependent EGFP expression. Cells treated with IR, AdEGR.TK and ganciclovir displayed a survival of 17.3% (6 Gy). However, significant gene expression was observed in the absence of IR with EGR.TK and EGR.EGFP constructs. Introduction of BGHpA upstream or upstream and downstream of expression cassette resulted in decreased nonspecific cytotoxicity by a factor of 1.6-2.3 with minor influence on the induced level of cytotoxicity. Introduction of insulating sequences in adenoviral vectors might allow tighter temporospatial control of gene expression by the radiation-inducible EGR-1 promoter.

Prediction of flap necrosis with laser induced indocyanine green fluorescence in a rat model

Prediction of necrosis has a clinical relevance in all fields of plastic surgery. The new application of indocyanine green (ICG) fluoroscopy in plastic surgery allows an objective quantification of skin perfusion and a high topographical resolution. The aim of the present study is to determine threshold values for flap perfusion under well-defined experimental conditions. Twenty random pattern flaps with a length to width ratio of 4:1 (8 x 2 cm(2)) were dissected on the anterior abdominal wall of 20 male Sprague-Dawley rats. ICG fluoroscopy was performed at the end of the operation. The animals were sacrificed at the seventh postoperative day with a reliable necrosis of the distal part of the flaps. Postoperative ICG fluoroscopy then was analysed both in regions that will survive and undergo necrosis. At day 7 a mean area of 5.5 cm(2) (57% of the total flap area) survived and a mean of 3.8 cm(2) (43%) became necrotic. The surviving part of the flap had a mean perfusion index of 62% compared to reference skin. The distal parts of the flap that necrotised showed an average perfusion index of only 19% postoperatively. Differences were statistically highly significant (p<0.001). Indocyanine green fluoroscopy is a useful tool to evaluate perfusion topographically and predict necrosis. From a statistical point of view a perfusion index of less than 25% of the reference skin can be considered as a sign of developing flap necrosis.

Non-invasive imaging of cardiac transgene expression with PET: comparison of the human sodium/iodide symporter gene and HSV1-tk as the reporter gene

PURPOSE

Genes encoding for intracellular enzymes or transmembrane proteins are suitable as reporters, but may differ in terms of applicability for cardiac imaging. The aim of this study was to compare the human sodium iodide symporter gene (hNIS) with the herpes simplex virus type 1 thymidine kinase gene (HSV1-tk) as the reporter gene in non-invasive imaging of cardiac transgene expression with positron emission tomography (PET).

METHODS

Equal doses of adenoviral vectors encoding for hNIS, wild-type HSV1-tk, mutant HSV1-sr39tk or LacZ as the control gene were directly injected into the myocardium of 34 animals. Two days later, dynamic PET was performed with a clinical scanner, using reporter probes specific for the respective reporter gene. Imaging with (13)N-ammonia was also performed to identify cardiac regions of interest.

RESULTS

Kinetics differed significantly: (124)I as the probe for hNIS showed rapid early uptake, remaining stable over time. Maximal myocardial concentration was 3.61+/-1.15%. The nucleoside (18)F-FHBG, as the specific probe for HSV1-sr39tk, showed increasing uptake over time, but maximal accumulation was significantly lower (1.45+/-0.54%, P=0.0009). (124)I-FIAU, as the specific probe for wild-type HSV1-tk, showed early uptake with subsequent washout. Maximal accumulation was lowest (0.63+/-0.23%, P<0.0001). Post-mortem analysis by autoradiography and gamma counting confirmed the in vivo data.

CONCLUSION

Reporter genes encoding for transporter proteins such as hNIS are an attractive alternative to overexpression of intracellular enzymes for cardiac gene product imaging. hNIS yielded higher signal intensity and imaging contrast for PET than did HSV1-tk and HSV1-sr39tk. Therefore, this approach may be preferable for the future monitoring of cardiac gene- or cell-based therapy.

[Nerve repair strategies for restoration of erectile function after radical pelvic surgery]

Iatrogenic cavernous nerve lesions occurring during radical pelvic surgery often lead to irreversible erectile dysfunction. The nerve defects after excision of the neurovascular bundles must be reconstructed by interposition grafting to supply a permissive scaffold for oriented axonal regrowth. The use of autologous nerve grafts for the repair of human cavernous nerves during radical prostatectomy has been controversial regarding the limited success achieved with bilateral nerve grafting. Artificial nerve guides consisting of natural or synthetic materials have been successfully used for bridging peripheral nerve defects. The combination with Schwann cells, neurotrophic factors and extracellular matrix components has been shown to promote cavernous nerve regeneration.

Cardiac reporter gene imaging using the human sodium/iodide symporter gene

OBJECTIVE

Imaging of reporter gene expression holds promise for noninvasive monitoring of cardiovascular molecular therapy. We investigated the feasibility of myocardial gene expression imaging in living rats using the human sodium/iodide symporter gene (hNIS) and widely available scintigraphic techniques.

METHODS

We injected adenovirus expressing hNIS under control of cytomegalovirus promoter (Ad(hNIS)) directly into left ventricular myocardium of Wistar rats. For detection of reporter gene expression, dynamic gamma-camera imaging was performed following intravenous injection of (123)Iodide or (99m)Technetium.

RESULTS

For both radiotracers, focal cardiac accumulation was identified as early as 10 min, and remained detectable until 2 hrs after injection, while it was not present in animals injected with LacZ control virus. Intensity of tracer accumulation gradually decreased when decreasing titers of Ad(hNIS) were applied. Treatment with sodium perchlorate (a blocker of hNIS) abolished cardiac tracer uptake after Ad(hNIS)-infection. Serial imaging after cardiac gene transfer demonstrated a peak of tracer signal between days 1 and 3, and a subsequent decrease until day 12. Postmortem analysis of hearts yielded significant correlation between in vivo radiotracer accumulation and ex vivo gamma-counting. Autoradiography demonstrated specific regional radioactivity in Ad(hNIS)-infected myocardial areas.

CONCLUSIONS

hNIS offers a practical and reliable approach for myocardial gene expression imaging. Using suitable vectors, hNIS may be coexpressed with therapeutic genes or stably expressed in stem cells for future monitoring of cardiovascular molecular therapy.

PET of cardiac transgene expression: comparison of 2 approaches based on herpesviral thymidine kinase reporter gene

PET of reporter gene expression holds promise for noninvasive monitoring of gene therapy. Previously, 2 approaches based on the herpes simplex virus type 1 thymidine kinase gene (HSV1-tk) have been successfully applied to the heart. Wild-type HSV1-tk was imaged with (124)I-labeled 2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyl-5-iodouracil (FIAU), and a mutant HSV1-tk (HSV1-sr39tk) was imaged with (18)F-labeled 9-[4-fluoro-3-(hydroxymethyl)butyl]guanine (FHBG). The aim of this study was to compare these 2 combinations with regard to specificity, imaging contrast, and reporter probe kinetics using dynamic PET in small and large animals.

METHODS

Similar titers of adenovirus-expressing wild-type HSV1-tk (Ad(tk)), mutant HSV1-sr39tk (Ad(sr39tk)), or control genes were directly injected into the myocardium of 24 rats and 8 pigs. Two days later, dynamic PET was performed with a clinical scanner during the 120 min after injection of (124)I-FIAU (Ad(tk) animals and controls) or (18)F-FHBG (Ad(sr39tk) animals and controls). Imaging with (13)N-ammonia was performed to identify cardiac regions of interest.

RESULTS

In rats, significant cardiac (124)I-FIAU accumulation occurred in images obtained early (10-30 min) after Ad(tk) injection. Because of tracer washout, however, no difference between Ad(tk)-injected animals and controls was seen in the images obtained later. For (18)F-FHBG, specific myocardial accumulation greater than background levels was detected in Ad(sr39tk)-injected animals at early imaging and, in contrast to (124)I-FIAU accumulation, increased over time until the latest imaging (105-120 min). At maximum, cardiac (18)F-FHBG concentration showed a 4.15 +/- 1.65-fold increase compared with controls (105-120 min), and cardiac (124)I-FIAU concentration reached a maximal increase of 1.34 +/- 0.38-fold compared with controls (10-30 min, P = 0.0014). Global cardiac reporter probe kinetics in rats were confirmed by regional myocardial analysis in pig hearts. Transgene expression was specifically visualized by both approaches. The highest target-to-background ratio of (124)I-FIAU in Ad(tk)-infected pig myocardium was 1.50 +/- 0.20, versus 2.64 +/- 0.49 for (18)F-FHBG in Ad(sr39tk)-infected areas (P = 0.01). In vivo results were confirmed by ex vivo counting and autoradiography.

CONCLUSION

Both reporter gene/probe combinations were feasible for noninvasive imaging of cardiac transgene expression in different species. Specific probe kinetics suggest different myocardial handling of pyrimidine (FIAU) and acycloguanosine (FHBG) derivatives. The results favor (18)F-FHBG with mutant HSV1-sr39tk because of continuous accumulation over time and higher imaging contrast.

Coexpression of herpesviral thymidine kinase reporter gene and VEGF gene for noninvasive monitoring of therapeutic gene transfer: an in vitro evaluation

Coexpression of a reporter gene and a therapeutic gene may allow for noninvasive monitoring of cardiac gene therapy. We sought to evaluate the usefulness of an adenoviral vector expressing mutant herpesviral thymidine kinase reporter gene (HSV1-sr39tk) and vascular endothelial growth factor (VEGF) 121 in independent expression cassettes (Ad4tk).

METHODS

Accumulation of 14C-2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil (FIAU) and 9-(4-18F-fluoro-3-hydroxymethylbutyl)guanine (FHBG) as reporter probes, and secretion of VEGF into medium, were determined for Ad4tk-infected H9c2 rat cardiac cells in vitro.

RESULTS

In vitro tracer uptake increased with increasing vector concentration and over time. It was comparable to cells infected with adenovirus expressing only wild-type HSV1-tk (reporter probe: 14C-FIAU) or mutant HSV1-sr39tk (reporter probe: 18F-FHBG). No significant uptake was observed in cells infected with adenovirus expressing VEGF alone. With increasing vector concentration, Ad4tk-infected cells increasingly released VEGF into medium. VEGF production correlated significantly with cellular reporter probe uptake (r = 0.93; P = 0.0003).

CONCLUSION

The usefulness of a vector coexpressing HSV1-tk and VEGF for noninvasive imaging of expression of a therapeutic transgene has been demonstrated in vitro. This approach may allow for future in vivo monitoring of cardiac angiogenesis gene therapy.

Adenovirus-mediated overexpression of tissue inhibitor of metalloproteinases-1 in the liver: efficient protection against T-cell lymphoma and colon carcinoma metastasis

BACKGROUND

Matrix metalloproteinases (MMPs) are critical for metastasis of tumor cells. Tissue inhibitor of metalloproteinases-1 (TIMP-1), a natural MMP inhibitor, was shown to reduce metastasis in different models. Here, we investigated whether increased TIMP-1 levels in the liver achieved by adenoviral gene transfer will effectively inhibit liver metastasis of two independent tumor cell lines.

METHOD

TIMP-1 was transferred with adenoviral vectors into the livers of DBA/2 and Balb/c mice, which were subsequently challenged by hematogenous experimental metastases of the T-cell lymphoma cell line L-CI.5s or the colorectal carcinoma cell line CT-26, respectively.

RESULTS

MMP-9 expression in the liver was induced upon metastasis in both tumor types. Adenoviral gene transfer led to high transduction efficacy as indicated by lacZ expression in 60% of hepatocytes. TIMP-1, a key inhibitor of MMP-9, was expressed at 10(5)-fold higher levels by adenoviral gene transfer as compared with levels achieved in TIMP-1 transgenic mice, previously shown to be inefficient to reduce T-cell lymphoma metastasis. High local and systemic (serum) levels of TIMP-1 led to substantial (94%) reduction of T-cell lymphoma and colorectal carcinoma (73%) experimental liver metastasis.

CONCLUSIONS

Adenoviral gene transfer led to systemic and local TIMP-1 levels sufficient to inhibit metastasis of a highly aggressive T-cell lymphoma, pointing at the requirement of threshold levels for effective anti-metastatic efficacy. This approach was also efficient in a colon carcinoma solid tumor model. We propose that viral gene transfer of TIMP-1 can provide a suitable defense strategy to prevent metastatic spread to the liver.

Use of the norepinephrine transporter as a reporter gene for non-invasive imaging of genetically modified cells

BACKGROUND

The norepinephrine transporter (NET) is a high-affinity transporter for catecholamines. Its expression is almost exclusively restricted to the sympathetic nervous system. In this study we evaluated whether the NET can be used as a reporter gene for non-invasive imaging of genetically modified cells with radiolabeled probes.

METHODS

Human A431, HT1080 and murine CMS-5 cells were retrovirally transduced with bovine NET cDNA. Transduced and parental cells were incubated in vitro with [(131)I]meta-iodobenzylguanidine ([(131)I]MIBG). The specificity of tracer uptake was determined by adding the NET inhibitor imipramine. Rat PC12 cells served as positive controls. Parental and A431NET cells were xenotransplanted into nude mice and tumor uptake of [(123)I]MIBG in vivo was determined after tracer administration.

RESULTS

In vitro stably transduced cells showed a 66- to 120-fold higher [(131)I]MIBG uptake than parental cells. Incubation with imipramine reduced [(131)I]MIBG uptake of transduced cells to the level found in parental cells. More than 70% of the initial radioactivity was retained in all transduced cell lines after 2 h incubation with tracer-free medium. [(131)I]MIBG uptake in PC12 cells, which express the NET endogenously, was 20- to 28-fold lower than in transduced cells. In vivo, A431NET tumors demonstrated a 33-fold higher [(123)I]MIBG uptake than parental tumors. Gamma camera images 24 h after tracer injection showed no tracer uptake in parental A431 tumors, but clear images of A431NET tumors.

CONCLUSIONS

Transduction of tumor cells with NET cDNA causes highly specific uptake and significant retention of catecholamine analogs in vitro and in vivo. These characteristics make the NET suitable as a reporter gene for non-invasive monitoring of gene transfer.

Noninvasive Imaging of Transgene Expression by Use of Positron Emission Tomography in a Pig Model of Myocardial Gene Transfer

BACKGROUND

Radionuclide imaging of reporter gene expression may be useful for noninvasive monitoring of clinical cardiac gene therapy. Experience until now, however, has been limited to small animals.

METHODS AND RESULTS

To evaluate feasibility in a clinically applicable setting, pigs were studied by conventional positron emission tomography (PET) 2 days after regional intramyocardial injection of control adenovirus or adenovirus carrying herpesviral thymidine kinase reporter gene (HSV1-tk). Myocardial blood flow was quantified by use of [13N]ammonia. Subsequently, kinetics of the reporter substrate [124I]-2'-fluoro-2'-deoxy-5-iodo-1-beta-d-arabino-furanosyluracil (FIAU) were assessed over a period of 2 hours. Areas infected with adenovirus expressing HSV1-tk showed significantly elevated FIAU retention during the first 30 minutes after injection. At later times, washout was observed, and retention was not different from that in areas infected with control virus or remote myocardium. Early in vivo FIAU uptake correlated with ex vivo images, autoradiography, and immunohistochemistry for reporter gene product after euthanasia. After intramyocardial injection of both adenoviruses, myocardial blood flow was mildly elevated compared with that in remote areas, consistent with histological signs of regional inflammation.

CONCLUSIONS

In vivo quantification of regional myocardial transgene expression is feasible with clinical PET methodology, the radioiodinated reporter probe FIAU, and the HSV1-tk reporter gene. Radioactivity efflux after specific initial uptake was not observed previously in tumor studies, suggesting that tissue-specific differences in nucleoside metabolism influence reporter probe kinetics. By coregistering reporter gene expression with additional biological parameters such as myocardial blood flow, PET allows for noninvasive characterization of the success of cardiac gene transfer along with its functional correlates.

Increase of Anti-Metastatic Efficacy by Selectivity- But Not Affinity-Optimization of Synthetic Serine Protease Inhibitors

Although tumors frequently show elevated protease activities, the concept of anti-proteolytic cancer therapy has lost momentum after failure of clinical trials with broad-spectrum matrix metalloproteinase inhibitors. Thus we need to adapt our design strategies for protease inhibitors. Here, we employed a series of seven structurally fine-modulated and pharmacokinetically closely related synthetic 4-amidinobenzylamine-based inhibitors with distinct selectivity for prototypical serine proteases in a murine T cell lymphoma liver metastasis model. This in vivo screening revealed efficacy of urokinase inhibitors but no correlation between urokinase selectivity or affinity and anti-metastatic effect. In contrast, factor Xa-selective inhibitors were more potent, demonstrating factor Xa or a factor Xa-like serine protease likely to be more determinant in this model. Factor Xa selectivity, but not affinity, significantly improved anti-metastatic efficacy. For example, factor Xa inhibitors CJ-504 and CJ-510 exert similar affinity for factor Xa (K(i)=14 nM versus 8.8 nM) but CJ-504 was 70-fold more selective for factor Xa. This correlated with higher anti-metastatic efficacy (58.8% with CJ-504; 28.2% with CJ-510). Our results show that among the protease inhibitors employed that have affinities in the nanomolar range, the strategy of selectivity-optimization is superior to further improvement of affinity to significantly enhance anti-metastatic efficacy. This appreciation may be important for the future rational design of new anti-proteolytic agents for cancer therapy.

Increase in gelatinase-specificity of matrix metalloproteinase inhibitors correlates with antimetastatic efficacy in a T-cell lymphoma model

The recognition that matrix metalloproteinases (MMPs) facilitate tumor cell invasion and metastasis has led to the development of synthetic MMP inhibitors (MMPIs) as cancer therapeutic agents. Because several Phase III trials failed recently to show efficacy of broad-spectrum MMPIs in advanced cancer, the feasibility of MMPs as therapeutic targets has been challenged. However, it has not yet been determined whether MMPIs that have increased specificity may have greater benefit. We show that MMP-9 expression closely correlates with the progression of liver metastasis in a T-cell lymphoma model. MMPIs with greater selectivity/specificity for MMP-9 in vitro showed greater efficacy against liver metastasis in vivo. These data demonstrate a link between increased specificity of MMPIs and enhanced anticancer activity.

YB-1 relocates to the nucleus in adenovirus-infected cells and facilitates viral replication by inducing E2 gene expression through the E2 late promoter

The adenovirus early proteins E1A and E1B-55kDa are key regulators of viral DNA replication, and it was thought that targeting of p53 by E1B-55kDa is essential for this process. Here we have identified a previously unrecognized function of E1B for adenovirus replication. We found that E1B-55kDa is involved in targeting the transcription factor YB-1 to the nuclei of adenovirus type 5-infected cells where it is associated with viral inclusion bodies believed to be sites of viral transcription and replication. We show that YB-1 facilitates E2 gene expression through the E2 late promoter thus controlling E2 gene activity at later stages of infection. The role of YB-1 for adenovirus replication was demonstrated with an E1-minus adenovirus vector containing a YB-1 transgene. In infected cells, AdYB-1 efficiently replicated and produced infectious progeny particles. Thus, adenovirus E1B-55kDa protein and the host cell factor YB-1 act jointly to facilitate adenovirus replication in the late phase of infection.

Uptake of radiolabeled 2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyluracil in cardiac cells after adenoviral transfer of the herpesvirus thymidine kinase gene: the cellular basis for cardiac gene imaging

BACKGROUND

Gene therapy is a promising approach for the treatment of cardiac diseases. Coexpression of therapeutic genes with a suitable marker gene would allow for the noninvasive imaging of successful gene transfer and expression via radiolabeled marker substrates. In the present study, such an approach was first applied to cardiac tissue.

METHODS AND RESULTS

The combination of the herpesvirus thymidine kinase reporter gene (HSV1-tk) and radiolabeled 2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyluracil (FIAU) was evaluated. H9c2 rat cardiomyoblasts were infected in vitro with a replication-defective HSV1-tk-containing adenovirus and a negative control virus. The intracellular uptake of [(14)C]FIAU increased with increasing multiplicity of infection and with time after infection. Uptake in negative controls remained <15% of positive controls. Additionally, vectors were applied intramyocardially in Wistar rats. The marker substrate [(125)I]FIAU was injected intravenously 3 days later, and animals were killed after 24 hours. Autoradiographically, regional transgene expression was clearly identified in animals receiving the adenovirus containing HSV1-tk (3. 4+/-2.2-fold increase of radioactivity at vector administration site compared with remote myocardium), whereas nonspecific uptake in negative controls was low (<10% of positive controls).

CONCLUSIONS

Using an adenoviral vector, HSV1-tk can be successfully expressed in cardiac cells in vitro and in vivo, yielding high uptake of radiolabeled FIAU. The results suggest that imaging transgene expression in the heart is feasible and may be used to monitor gene therapy noninvasively.

Gene transfer of human interferon gamma complementary DNA into a renal cell carcinoma line enhances MHC-restricted cytotoxic T lymphocyte recognition but suppresses non-MHC-restricted effector cell activity

Even though renal cell carcinomas (RCC) are thought to be immunogenic, many tumors express variations in surface molecules and intracellular proteins that hinder induction of optimal antitumor responses. Interferon gamma (IFNgamma) stimulation can correct some of these deficiencies. Therefore, we introduced the complementary DNA (cDNA) encoding human IFNgamma into a well-characterized RCC line that has been selected for development of an allogeneic tumor cell vaccine for treatment of patients with metastatic disease. Studies were performed to determine how endogenous IFNgamma expression influences tumor cell immunogenicity. IFNgamma transductants showed minimal increases in surface expression of MHC class I and adhesion molecules but expression of class II molecules was induced. Proteins of the transporter associated with antigen processing (TAP) and low molecular weight polypeptide (LMP) were constitutively expressed at high levels. The transductants stimulated allospecific cytotoxic T lymphocytes (CTL); however, they were not better than unmodified tumor cells in this capacity. Endogenous IFNgamma expression enhanced tumor cell recognition by MHC-restricted, tumor antigen-specific CTL but suppressed recognition by non-MHC-restricted cytotoxic cells. Thus, the functional consequences of IFNgamma expression varied with respect to the type of effector cell and were not always beneficial for tumor cell recognition.

In vivo imaging of herpes simplex virus type 1 thymidine kinase gene expression: early kinetics of radiolabelled FIAU

Previous studies have shown that the herpes simplex virus type 1 thymidine kinase gene (HSV1-tk), in combination with appropriate radiolabelled substrates (e.g. [I*]-2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyluracil, I*-FIAU, where the asterisk indicates that any of the various radioactive iodine isotopes can be used), can be used as a reporter gene for in vivo monitoring of gene transfer and expression. The aim of our study was to examine the early kinetics of I*-FIAU and the possibility of utilising iodine-123-labelled FIAU for imaging of gene expression. CMS-5 fibrosarcoma cells were transduced in vitro with the retroviral vector STK containing the HSV1-tk gene. BALB/c mice were inoculated subcutaneously with HSV1-tk(+) and tk(-) cells into both flanks. FAU (2'-fluoro-2'-deoxy-1-beta-D-arabinofuranosyluracil was radioiodinated (123I, 125I) using the iodogen method. High-performance liquid chromatography purification resulted in high specific activity and radiochemical purity for both tracers ([123I]FIAU and [125I]FIAU). Biodistribution studies and gamma camera imaging were performed at 0.5, 1, 2 and 4 h p.i. In addition, the genomic DNA of the tumours was isolated for measurement of the activity accumulation resulting from the [125I]FIAU incorporation. Biodistribution studies 0.5 h p.i. showed tumour/blood and tumour/muscle ratios of 3.8 and 7.2, respectively, for the HSV1-tk(+) tumours, and 0.6 and 1.2, respectively, for negative control tumours. Fast renal elimination of the tracer from the body resulted in rapidly increasing tumour/blood and tumour/muscle ratios which reached values of 32 and 88 at 4 h p.i., respectively. Tracer clearance from blood was bi-exponential, with an initial half-life of 0.6 h followed by a half-life of 4.6 h. The tracer half-life in herpes simplex viral thymidine kinase-expressing tumours was 35.7 h. The highest activity accumulation (20.3%+/-5.7% ID/g) in HSV1-tk(+) tumours was observed 1 h p.i. At that time, about 46% of the total activity found in HSV1-tk(+) tumours was incorporated into genomic DNA. Planar gamma camera imaging showed a distinct tracer accumulation as early as 0.5 h p.i., with an increase in contrast over time. These results suggest that sufficient tumour/background ratios for in vivo imaging of HSV1-tk expression with [123I]FIAU are reached as early as 1 h p.i.

Tumor necrosis factor-alpha and interferon-gamma, but not HTLV-I tax, are likely factors in the epidermotropism of cutaneous T-cell lymphoma via induction of interferon-inducible protein-10

We have previously shown that Interferon-Inducible Protein-10 (IP-10), a cytokine chemotactic for CD4-positive lymphocytes, is overexpressed by lesional epidermal keratinocytes and probably accounts for the epidermotropism of cutaneous T-cell lymphoma (CTCL). The tax gene of human T-lymphotropic virus-I (HTLV-I) immortalizes CD4-positive lymphocytes, induces IFN-gamma, and has been detected in patients with classical CTCL who are seronegative for HTLV-I. TNF-alpha is synergistic with IFN-gamma for the induction of IP-10. We therefore decided to define the presence of tax, IFN-gamma, TNF-alpha, and IP-10 in lesions of 19 adults with classical CTCL who were seronegative for HTLV-I. Lesional mRNAs for actin, TNF-alpha, IFN-gamma, and tax were detected by reverse-transcriptase polymerase chain reaction (RT-PCR) amplification. In addition IP-10, TNF-alpha, and IFN-gamma were detected and localized with immunocytochemistry of frozen sections. In agreement with previous observations IP-10 was overexpressed in lesional keratinocytes of all 19 patients. By RT-PCR, mRNA for IFN-gamma was detected in lesions of 8, and for TNF-alpha in lesions of 13 patients. By immunocytochemistry, TNF-alpha was expressed by lesional keratinocytes in 10 of 13 tested patients, whereas IFN-gamma was focally expressed by lesional lymphocytes and faintly by lesional keratinocytes in 9 of 13 tested patients. tax mRNA was not detected in lesions of any patient, but was easily detectable in cutaneous lesions or peripheral blood of control patients who were seropositive for HTLV-I. We conclude that TNF-alpha and IFN-gamma may cause epidermotropism by inducing IP-10. However, the tax gene of HTLV-I does not appear to be involved in the pathogenesis of classical CTCL.