Biomedical subjects

M Puhlmann

Publications and source records attributed to M Puhlmann.

14 recordsLinked to original sources

PubMed2000

Vaccinia as a vector for tumor-directed gene therapy: biodistribution of a thymidine kinase-deleted mutant.

Tumor-directed gene therapy, such as "suicide gene" therapy, requires high levels of gene expression in a high percentage of tumor cells in vivo to be effective. Current vector strategies have been ineffective in achieving these goals. This report introduces the attenuated (thymidine kinase (TK)-negative) replication-competent vaccinia virus (VV) as a potential vector for tumor-directed gene therapy by studying the biodistribution of VV in animal tumor models. A TK-deleted recombinant VV (Western Reserve strain) expressing luciferase on a synthetic promoter was constructed. Luciferase activity was measured in vitro after transduction of a variety of human and murine tumor cell lines and in vivo after intraperitoneal (i.p.) delivery in C57BL/6 mice with 7-day i.p. tumors (10(6) MC-38 cells). Three other in vivo tumor models were examined for tumor-specific gene expression after intravenous delivery of VV (human melanoma in nude mice, adenocarcinoma liver metastasis in immunocompetent mice, and subcutaneous sarcoma in the rat). In addition, a replication-incompetent vaccinia (1 microg of psoralen and ultraviolet light, 365 nm, 4 minutes) was tested in vitro and in vivo and compared with active virus. Luciferase activity in i.p. tumors at 4 days after i.p. injection of VV was >7000-fold higher than lung, >3000-fold higher than liver, and >250-fold higher than ovary. In addition, intravenous injection of VV resulted in markedly higher tumor luciferase activity compared with any other organ in every model tested (up to 188,000-fold higher than liver and 77,000-fold higher than lung). Inactivation of the virus resulted in negligible gene expression in vivo. In summary, VV has a high transduction efficiency in tumor cells with high levels of gene expression. The results suggest a selective in vivo replication of TK-deleted VV in tumor cells. Replication competent, TK-deleted VV appears to be an ideal vector for testing the in vivo delivery of toxic genes to tumor cells.

Animals↗

PubMed2000

Complex interactions between the replicating oncolytic effect and the enzyme/prodrug effect of vaccinia-mediated tumor regression.

Replicating viruses for cancer gene therapy have beneficial antitumor effects, however, in the setting of an enzyme/prodrug system, the interactions between these viruses and the activated agents are complex. A replicating vaccinia virus expressing the cytosine deaminase gene (VVCD), which converts the prodrug 5-FC into 5-FU, was characterized in vitro and in vivo for its antitumor effects and pathogenicity. Replicating VVCD (+/-5-FC) at various MOIs was used to infect MC38 murine colon adenocarcinoma cells. At high MOIs (>0.1) virus alone was able to kill the majority (65-90%) of cells by day 5 with no additional benefit from prodrug. At low MOIs only the effect of prodrug is seen. Cell lysates demonstrated 300-fold reduced viral recovery from cells treated with both VVCD and 5-FC compared with controls treated with virus alone. Nude mice bearing subcutaneous MC38 tumors were injected with VVCD (or control) and treated with 5FC or control. Mice injected with VVCD (with or without 5FC treatment) had smaller tumors than the controls, suggesting that replicating vaccinia alone is cytotoxic to tumors in vivo. The addition of 5-FC improved the antitumor response when a low dose of virus was injected into tumors. Also, compared with mice that received virus alone, those that received VVCD and 5FC had significantly prolonged survival from virus-mediated death. In conclusion, the addition of an enzyme/prodrug system to a replicating virus can improve the antitumor response and decrease viral pathogenicity. Gene Therapy (2000) 7, 1217-1223.

Adenocarcinoma↗

PubMed2000

A phase I-II study of isolated hepatic perfusion using melphalan with or without tumor necrosis factor for patients with ocular melanoma metastatic to liver.

There are no satisfactory treatment options for patients with ocular melanoma metastatic to liver, and after liver metastases are identified, median survival is only between 2 and 7 months. Because liver metastases are the sole or life-limiting component of disease in the vast majority of patients who recur, we reasoned that complete vascular isolation and perfusion of the liver might result in clinically meaningful regression of disease. Between September 1994 and July 1999, 22 patients (13 women and 9 men; mean age, 49 years) with ocular melanoma metastatic to liver were treated with a 60-min hyperthermic isolated hepatic perfusion (IHP) using melphalan alone (1.5-2.5 mg/kg, n = 11) or with tumor necrosis factor (TNF, 1.0 mg, n = 11). Via a laparotomy, IHP inflow was via the hepatic artery alone (n = 17) or hepatic artery and portal vein (n = 5) and outflow from an isolated segment of inferior vena cava. Most patients had advanced tumor burden with a mean percentage of hepatic replacement of 25% (range, 10-75%) and a median number of metastatic nodules of 25 (range, 5 to >50). Complete vascular isolation was confirmed in all patients using a continuous intraoperative leak monitoring technique with 131I radiolabeled albumin. There was one treatment mortality (5%). The overall response rate in 21 patients was 62% including 2 radiographic complete responses (9.5%) and 11 partial responses (52%). The overall median duration of response was 9 months (range, 5-50) and was significantly longer in those treated with TNF than without (14 versus 6 months, respectively; P = 0.04). Overall median survival in 22 patients was 11 months. These data indicate that a single 60-min IHP can result in significant regression of advanced hepatic metastases from ocular melanoma. TNF appears to significantly prolong the duration of response.

Adult↗

PubMed1999

Tumor-specific gene delivery using recombinant vaccinia virus in a rabbit model of liver metastases.

BACKGROUND: Several approaches to gene therapy for cancer have yielded promising results in rodent models. The translation of these results to the clinical realm has been delayed by the lack of tumor models in large animals. We investigated the pattern of transgene (i. e., foreign or introduced gene) expression and virus vector elimination after systemic gene delivery using a thymidine kinase-negative vaccinia virus in a rabbit model of disseminated liver metastases. METHODS: VX-2 rabbit carcinoma cells were maintained by serial transplantation in the thigh muscles of New Zealand White rabbits, and disseminated liver metastases were established by direct injection of tumor cells into the portal vein of the animals. Different doses of a recombinant thymidine kinase-negative vaccinia virus vector encoding the firefly luciferase reporter gene (i.e., transgene) were injected into tumor-bearing rabbits. Transgene activity in tumors and other organs was measured at multiple time points thereafter. The pattern of development of antibodies against the vaccinia virus vector was also examined. Two-tailed Student's paired t test was used for comparisons of transgene activity. RESULTS: Transgene expression was increased in tumors by at least 16-fold in comparison with expression in other tissues by day 4 after vector injection (all P<. 001) and was maintained for approximately 1 week, providing evidence of tumor-specific gene delivery in this model. Rapid elimination of the circulating vector by the host immune system was observed. Anti-vector antibodies were detectable in serum as early as day 6 and were maintained for more than 3 months. CONCLUSIONS: Tumor-specific gene delivery is possible after systemic injection of a thymidine kinase-negative vaccinia virus vector in a model of rabbit liver metastases. Although the period of transgene expression appears limited because of a rapid immune response, the therapeutic window might be sufficient for an enzyme/prodrug gene therapy approach in clinical application.

Animals↗

PubMed1999

Sensitization of tumor necrosis factor alpha-resistant human melanoma by tumor-specific in vivo transfer of the gene encoding endothelial monocyte-activating polypeptide II using recombinant vaccinia virus.

Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine with potent experimental antitumor activity. Its clinical use in cancer treatment is severely limited by its considerable toxicity after systemic administration, and it is currently confined to isolated limb and organ perfusion settings. In this report, we introduce a novel concept of TNF-alpha-based gene therapy using the TNF-sensitizing properties of endothelial cell monocyte-activating polypeptide II (EMAP-II). We hypothesized that transfer of the EMAP-II gene into established TNF-resistant human melanomas would render these tumors sensitive to subsequent systemic TNF-alpha treatment. To achieve tumor selective gene delivery, we constructed a recombinant vaccinia virus encoding the human EMAP-II gene (vvEMAP). In vitro transfection of human melanoma cells led to the production of EMAP-II by these cells. Supernatants of vvEMAP-transfected tumor cells mediated the induction of tissue factor in endothelial cells. We characterized the pattern of gene expression after systemic administration of a recombinant vaccinia virus encoding a reporter gene in a murine in vivo model of s.c. human melanoma. Gene expression in tumor tissue was increased 100-fold as compared with normal tissue, providing evidence for tumor-selective gene delivery. Finally, human melanomas in nude mice were sensitized in vivo by transferring the EMAP-II gene using vvEMAP. Subsequent systemic administration of TNF-alpha led to tumor regression and growth inhibition of these previously TNF-resistant tumors (P < 0.05). This approach using gene therapy to sensitize primarily unresponsive tumors toward TNF-alpha may enhance the usefulness of TNF-alpha in clinical treatment strategies by increasing the window for the therapeutic application of the cytokine, thus reducing the dose necessary for antitumor responses and subsequently reduce toxicity.

Animals↗

PubMed1999

Systemic administration of a recombinant vaccinia virus expressing the cytosine deaminase gene and subsequent treatment with 5-fluorocytosine leads to tumor-specific gene expression and prolongation of survival in mice.

Suicide gene therapy using the cytosine deaminase (CD) gene and 5-fluorocytosine (5-FC) has shown promising results for the treatment of colon carcinoma cells in vitro. Efficient viral infection and tumor-specific gene delivery is crucial for clinically measurable treatment effects. After proving efficient gene transfer in vitro, we demonstrate here that genes can be delivered to metastatic liver tumors in vivo in a highly selective manner using systemic delivery of a thymidine kinase-deleted (TK-) recombinant vaccinia virus (Western Reserve strain). When the vector was administered systemically in C57BL/6 mice or nude/athymic mice with established disseminated MC38 liver metastases, transgene expression in tumors was usually 1,000 to 10,000-fold higher compared with other organs (n = 160; P < 0.0001). This tumor-specific gene transfer leads to significant tumor responses and subsequent survival benefits after the transfer of the CD gene to liver metastases and subsequent systemic treatment with the prodrug 5-FC (P < 0.0001). We describe reporter gene and survival experiments both in immunocompetent and athymic nude mice, establishing a gene expression pattern over time and characterizing the treatment effects of the virus delivery/prodrug system. Cure rates of up to 30% in animals with established liver metastases show that suicide gene therapy using TK- vaccinia virus as a vector may be a promising system for the clinical application of tumor-directed gene therapy.

Adenocarcinoma↗

PubMed1999

Thymidine kinase-deleted vaccinia virus expressing purine nucleoside phosphorylase as a vector for tumor-directed gene therapy.

Tumor-directed gene therapy faces many obstacles. Lack of tissue targeting and low in vivo transduction efficiency represent some of the limitations for a successful therapeutic outcome. A thymidine kinase-deleted mutant vaccinia virus has been shown in marker studies to replicate selectively in tumor tissue in animal models. Purine nucleoside phosphorylase (PNP), from E. coli, converts the nontoxic prodrug 6-methylpurine deoxyriboside (6-MPDR) to the toxic purine 6-methylpurine. In this study, we investigated the cytotoxic properties of PNP, expressed by an optimized synthetic early/late promoter in a vaccinia virus (vMPPNP). In vitro cytotoxicity of psoralen-inactivated vMPPNP (1 microg of psoralen, 4 min of LWUV [365 nm]) at the maximum tolerated dose (MTD) of 6-MPDR (80 microM) reduced cell viability by day 3 to 1.7%. At an MOI of 0.002, replication-competent vMPPNP and 6-MPDR (80 microM) caused reduction of cell viability to 19.8% within 4 days. Furthermore, there was complete abrogation of viral replication after intracellular conversion of prodrug into the active toxin. The potency of such a system was similar among all histologies tested. Finally, the cytotoxic efficacy has been shown to be more rapid and complete than that of cytosine deaminase (CD), a more established enzyme/prodrug system. When virus was delivered intraperitoneally into athymic mice with hepatic metastases, followed by administration of prodrug, there was a significant prolongation of survival and a 30% cure rate. In summary, owing to its tumor-targeting capabilities, high transduction efficiency, and high gene expression, a vaccinia virus expressing PNP could prove to be a potent and valuable vector for tumor-targeted gene therapy.

Animals↗

PubMed1999

[Value of tumor debulking in gastrointestinal tumors].

Tumor debulking of gastrointestinal tumors for the reduction of tumor mass is intended to improve subsequent treatment efficacy. However, in advanced malignant disease, this therapy is often associated with increased morbidity and lethality. Adjuvant therapies cannot be initiated when needed. Therefore, long-term survival remains unaffected. Advances in biomedical science provide preliminary explanations for these therapeutic problems. Modern therapeutic concepts like neoadjuvant therapy for locally advanced tumors are based on these findings. The probability of complete R0 resections, necessary to improve long-term survival, can be enhanced by these therapies. The ongoing prospective neoadjuvant studies for gastrointestinal tumors are already very encouraging.

Combined Modality Therapy↗

PubMed1999

Regional versus systemic delivery of recombinant vaccinia virus as suicide gene therapy for murine liver metastases.

OBJECTIVE: Specific and efficient tumor-targeted gene delivery is the major goal for successful cancer gene therapy. SUMMARY BACKGROUND DATA: A recombinant thymidine kinase-deleted vaccinia virus (vv) encoding the firefly luciferase (luc) reporter gene or the prodrug converter gene cytosine deaminase (CD) was constructed. The authors compared the extent, duration, and pattern of transgene (luc) expression in vivo after portal venous, intraperitoneal, or intravenous virus administration and survival after treatment with the vv containing CD followed by the prodrug 5-fluorocytosine (5-FC) in a murine model of disseminated liver metastases from colon cancer. METHODS: Recombinant vv containing the luc transgene within the thymidine kinase locus was administered to mice with isolated liver metastases from an MC38 adenocarcinoma. Transgene expression was determined in tumor and organs at various time points. Tumor-bearing mice were treated with recombinant vv containing CD and 5-FC or with appropriate controls and followed for survival. RESULTS: Tumor-specific gene delivery was achieved irrespective of administration route, with gene expression in tumors increased by up to 100,000-fold compared with normal tissues. There was significantly increased transgene expression in tumor after portal venous or intraperitoneal virus administration (p = 0.001 vs. systemic). Treatment using a CD-expressing vv and systemic 5-FC resulted in a significant survival benefit in all treatment groups compared with controls (p < 0.007); there was no additional benefit for portal venous or intraperitoneal virus administration. CONCLUSIONS: Suicide gene therapy using vv with the CD/5-FC system leads to tumor-specific gene expression and improved survival and can result in cure of established liver metastases.

Adenocarcinoma↗

PubMed1996

[Diagnostic problems in acute appendicitis and indications for laparoscopic appendectomy].

A retrospective study analyzing the outcome of 400 appendectomies for acute appendicitis in two different hospitals revealed a negative appendectomy rate of over 25%. As a consequence we altered the operative strategy by employing diagnostic laparoscopy in combination with laparoscopic appendectomy in all uncertain cases while still carrying out a conventional appendectomy when there was diagnostic certainty. Preliminary results show that laparoscopic appendectomy is a safe procedure and that the new concept reduces the negative appendectomy rate.

Acute Disease↗

PubMed1995

Sterilization of partially demineralized bone matrix: the effects of different sterilization techniques on osteogenetic properties.

Transplantation of allogenic bone requires the thorough examination of donors as well as the careful processing and storage of samples in order to minimize potential infection. Other problems associated with allogenic transplants such as low osteoinductive properties and immunological reactions led to the development of partially demineralized bone matrix (PDBM). This highly osteogenic bone extract is largely free of antigens and easy to produce. However, in order to exclude the potential risk of infection, PDBM should be sterilized prior to implantation. It was the purpose of this study to investigate the influence of various sterilization techniques on the osteoinductive properties of PDBM. Seventy-six drill defects with a diameter of 0.6 cm in the tibia of 11 Merino sheep were filled with PDBM as well as autogenic or allogenic cancellous bone. Prior to implantation the PDBM was sterilized using autoclavation, gamma irradiation, ethylene oxide, or ethanol. Twelve empty drill holes served as controls. The extent of new bone formation was ascertained by histological, fluorescent-optical, and microradiographical examinations 3 and 6 weeks postoperatively. Furthermore, the amount of newly formed bone was measured quantitatively. Apart from autoclaved PDBM, all matrix grafts showed excellent new bone formation after sterilization, exceeding the results of allogenic cancellous bone.

Animals↗

PubMed1994

[Bridging long tibial shaft defects by partially demineralized bone matrix].

The problems arising from the transplantation of autogenic and allogenic bone have significantly limited the use of these methods. Hence, there is an ever increasing demand for suitable transplant materials that could be readily available to orthopaedic surgeons throughout the country. Although the advantages of demineralized bone matrix over allogenic cancellous bone have been shown in numerous experimental studies, its broad clinical application has so far been limited. The purpose of this study was to investigate the osteogenic properties of partially demineralized bone matrix in clinically relevant and realistic conditions. Tibial defects 5 cm in length in 24 merino sheep were bridged by way of medullary nailing and filled with various preparations of bone matrix. Cortical bone displaying poor vascularization and rotation instability of the osteosynthesis ensured extremely difficult testing conditions for the transplant. Postoperatively, the extent of new bone formation was evaluated by means of regular X-ray examinations over a period of 12-20 weeks. In addition, histological, fluorescent-optical and microradiographic examinations of the final specimen were carried out. Good new bone formation regularly followed the transplantation of partially demineralized bone matrix with a particle size of 750 microns. Complete bridging of the defect was achieved when small amounts of bone marrow were added. The use of bone matrix with a smaller or larger particle size did not influence the rate of new bone formation perceptibly.

Animals↗

PubMed1994

[Laparoscopic cholecystectomy--experiences in a British district general hospital].

In the first year after the introduction of the new technique a complication rate of 3.3% was calculated from the evaluation of 118 laparoscopic cholecystectomies. The only severe complication noted was a perforation of the transverse colon following the insertion of a 10 mm port. Henceforth, open laparoscopy is performed in difficult cases. Hereby, to ensure a more secure sealing of the initial incision, an endotracheal tube can be used as the camera port. The conversion rate was found to be 9%, whereby in 50% of acute cholecystitis an open procedure had to be adopted. The use of a Nd-Yag-Laser in 24 cases proved to be of no apparent advantage. Intraoperative cholangiograms were carried out selectively to demonstrate the anatomical situation, or in cases where common bile duct stones were suspected. Within a year, it was possible to reduce the mean operating time from 130 min to 80 min. The postoperative stay was on average 3.7 days. From an economic point of view, the substantially shorter hospitalisation period outweighs the longer operating time. However, more stringent and precise standards with respect to an overall concept in diagnosing and treating common bile duct stones would be beneficial.

Cholecystectomy, Laparoscopic↗

PubMed1992

[The effect of various sterilization procedures on the osteoinductive properties of demineralized bone matrix].

To minimize potential infection following the transplantation of allogeneic bone, extremely rigorous selection of donors and careful processing and storage of samples are required. Other major problems related to allogeneic transplants, such as reduced osteogenic properties and immunological reactions, led to the development of demineralized bone matrix (DBM). This osteoinductive bone extract is largely free of antigens and is easy to produce. However, to eliminate the potential risk of infection, DBM should be sterilized prior to implantation. The purpose of this study was to investigate the influence of different sterilization techniques on the osteoinductive properties of DBM. A series of 76 cortical defects (drill holes) 0.6 cm in diameter in the tibiae of 11 Merino sheep were filled with DBM in addition to autogeneic and allogeneic cancellous bone. Prior to implantation DBM was sterilized by autoclaving, gamma irradiation, or application of ethylene oxide or ethyl alcohol. A further 12 drill holes were left empty as controls. The formation of new bone was examined 3 and 6 weeks postoperatively, using histological, fluorescent-optical and microradiographical techniques. The amount of newly formed bone was also quantified. Apart from autoclaved DBM all matrix grafts showed excellent new bone formation following sterilization, by far exceeding the formation with allogeneic cancellous bone.

Animals↗