A syngeneic mouse glioma model for study of glioblastoma therapy.

Animal models of human tumors serve a vital role in the development and testing of new anticancer therapies. Since the immune system is likely to play an essential role in tumor eradication, there is a particular need for modeling human disease in immunocompetent hosts. Few models of glioma have been developed in immunocompetent mice that are commercially available and none of these tumors have histological and antigenic characteristics of human gliomas. We have used a cell line, 4C8, derived from a spontaneous glioma-like tumor that arose in a transgenic mouse to develop a new glioma model. The intracranial injection of 4C8 cells into immunocompetent syngeneic B6D2F1 mice resulted in tumors that were densely cellular, developed a pseudopallisading pattern of necrosis, and expressed GFAP; all important features of human malignant gliomas. The average neurological endpoint was 51 days after intracranial injection. The 4C8 cells also grew rapidly in the flank, retaining histologic features seen in intracranial tumors. Flank tumors reached an average volume of 100 mm3, a volume ideal for therapy testing, by 34 days postinjection. These results suggest that the 4C8 mouse glioma model is an excellent system in which to test new antiglioma therapies for use in humans.

A simple, reproducible technique for establishing leptomeningeal tumors in nude rats.

The incidence of leptomeningeal carcinomatosis is on the rise and current treatment modalities have limited efficacy. The development of new treatment strategies has been hampered by the lack of an appropriate animal model that accurately parallels the clinical condition. We have developed a new surgical technique for the establishment of leptomeningeal tumors in rats. Our technique is simple, reproducible and associated with low morbidity and mortality. Tumor implantation resulted in a defined neurological endpoint and a reproducible time course of disease progression using both human medulloblastoma and breast carcinoma cell lines. This animal model provides an appropriate system for testing conventional and new biologic therapies in both early and late stages of leptomeningeal disease.

A novel multiply-mutated HSV-1 strain for the treatment of human brain tumors.

A promising approach for the therapeutic treatment of brain tumors utilizes replication-competent, neuroattenuated herpes simplex virus-1 (HSV-1) mutants. This approach requires mutation of HSV-1 to eliminate killing of normal, nondividing cells of the brain (e.g., neurons). We have generated a HSV-1 double-mutant, designated 3616UB, by interrupting the uracil DNA glycosylase (UNG) gene in a previously studied ICP34.5 mutant, R3616. The HSV-1-encoded UNG gene is required for efficient HSV-1 replication in nondividing cells, but is dispensable for replication in rapidly dividing cells. The specific function of the HSV-1 ICP34.5 gene is not completely clear, but it is thought to be necessary for viral replication in cells of the nervous system, because, when mutated, the resultant viral strains are fully neuroattenuated. Strain 3616UB did not replicate in primary neuronal cultures in vitro or in mouse brain, but efficiently killed six of six human tumor cell lines within 6 days in vitro and successfully infected and replicated within brain tumor xenografts. The potential safety of 3616UB for human use is enhanced by an unexpected hypersensitivity to the antiherpetic drug ganciclovir. These data suggest that 3616UB may be effective for the treatment of human brain tumors. Intratumoral injection of 3616UB into human medulloblastoma or angiosarcoma xenografts established in severe combined immunodeficient (SCID) mice produced significant growth arrest and some tumor regressions. Strain 3616UB was as effective as R3616 in this therapy study and did not cause any obvious distress in the treated animals. Together, the data show that 3616UB is a very safe alternative to other HSV-1 mutants because the presence of two mutations reduces the possibility of recombinational events in situ that could lead to the generation of virulent viral progeny during 3616UB therapy.

High protein diets are associated with increased bacterial translocation in septic guinea pigs.

During sepsis, body protein stores are decreased due to an increase in protein catabolism. The utilization of nutritional support with high-protein diets has been used as a solution to the problem of sepsis-induced protein loss. Work from our laboratory, however, has shown that diets low in protein (5% of total calories) improve survival in septic animals as compared to high protein (20%) diets. The present study investigated the relationship between low-protein diets and improved survival by determining whether septic animals receiving high-protein diets have increased bacterial translocation. Sepsis was induced in guinea pigs by the implantation of an osmotic minipump into the peritoneal cavity containing an equal mixture of Escherichia coli (10(8)) and Staphylococcus aureus (10(8)) or saline. On Day 3 postlaparotomy, the animals were randomized to one of four groups. The groups consisted of septic and nonseptic animals that received a diet with 5 or 20% of total calories as protein. Following 4 days of diet all animals received an instillation of 14C labeled E. coli (10(10)). Four hours later the animals were sacrificed and blood, mesenteric lymph nodes, spleen, lungs, and liver were removed for determination of radionuclide counts. Results indicated that the septic animals that received the high protein diet had more bacterial translocation, as indexed by higher radionuclide counts in the MLN, liver, lung and blood. These findings suggest that a low protein, enterally fed diet may improve survival in septic patients by decreasing the incidence of bacterial translocation.

Anabolic impact of cimaterol in conjunction with enteral nutrition following burn trauma.

Burn injury is characterized by increased energy expenditure, weight loss, and muscle protein wasting. Studies have shown that beta 2-adrenergic agonists have anabolic properties in the presence of increased metabolism. This study investigated the effects of the beta 2-agonist cimaterol in burned animals receiving enteral nutrition. Guinea pigs with gastrostomies were given a 30% total body surface area burn and fed for 14 days. Animals received saline or cimaterol (0.15 mg/kg, SC) twice daily. Energy expenditure was determined before burn and on postburn days 3, 6, 9, and 12. On day 14, the soleus, gastrocnemius muscles, and heart were excised and weighed as a measure of muscle catabolism and anabolism. Carcass weight was determined to measure muscle catabolism. Cimaterol increased (p < 0.05) total protein content, gastrocnemius muscle, and carcass weights. The soleus muscle and heart weights, and resting metabolic rates showed no significant differences. Results suggest enteral nutrition with cimaterol decreases burn-induced muscle catabolism.

Post injury hypermetabolic response and magnitude of translocation: prevention by early enteral nutrition.

The relationship between hypermetabolism and bacterial translocation was investigated in guinea pigs receiving a 40% burn. Animals were infused intragastrically with a complete enteral diet or Ringer's solution for 48 h, given 10(10) 14C-labeled Escherichia coli intragastrically, and killed 4 h later. Resting metabolic expenditure (RME), translocation (dpm of the 14C-labeled E. coli) to the portal blood and ileal mucosa, plasma cortisol, and urinary vanillylmandelic acid (VMA) were determined. Enterally fed animals had significantly lower RME, cortisol, VMA, and dpm, but higher mucosal and body weight than the Ringer's group. Disintegrations per minute (dpm) in the blood were positively correlated with RME (r = 0.856), cortisol (r = 0.872), VMA (r = 0.759), and dpm mucosa (r = 0.836) and inversely correlated with mucosal weight (r = -0.883). We conclude that bacterial translocation is reduced by early feeding and is an important cause of hypermetabolism and stress hormone production after burn injury.

Role of early enteral feeding and acute starvation on postburn bacterial translocation and host defense: prospective, randomized trials.

OBJECTIVES: To investigate the effect of: a) starvation during the preburn period and b) immediate postburn enteral nutrition on the permeability of the gut to microorganisms and the ability of the host to kill translocated bacteria. DESIGN: Prospective, randomized, experimental trials. SETTING: Laboratory. SUBJECTS: Balb/c mice and Hartley guinea pigs. INTERVENTIONS: In the first experiment, mice were starved for 0, 6, 12, 18, or 24 hrs before receiving gavage with 10(10) 14C-labeled Escherichia coli and a 20% burn injury. In the second experiment, guinea pigs received a 40% burn injury and were randomized to receive a complete enteral diet (175 kcal/kg/day) or infusion of an equal volume of lactated Ringer's solution via a previously placed gastrostomy for 6, 24, or 48 hrs. After each feeding period, 10(10) 14C Escherichia coli were infused intragastrically. In both experiments, the animals were killed 4 hrs after gavage, and mesenteric lymph nodes, spleen, liver, lungs, peritoneal fluid, and blood were harvested aseptically. MEASUREMENTS: For each tissue or fluid, the number of viable E. coli and radionuclide counts of the 14C E. coli were measured and the percentage of translocated bacteria that remained alive was calculated. MAIN RESULTS: In mice, 18 and 24 hrs of preburn starvation increased translocation only to the mesenteric lymph nodes, but it also enhanced bacterial killing in all tested tissues. Guinea pigs that were fed enterally for 6, 24, and 48 hrs postburn had significantly lower bacterial translocation in all tissues compared with animals infused with lactated Ringer's solution. Additionally, enhanced killing of translocating organisms was observed after 24 and 48 hrs of feeding. CONCLUSIONS: Starvation preburn has different consequences than starvation postburn on translocation and bacterial killing. Postburn enteral nutrition decreases the load of viable bacteria in the tissues via a double mechanism: an initial decreased translocation and a subsequent improved ability to kill bacteria that do translocate.

Influence of dietary fiber on microbial growth in vitro and bacterial translocation after burn injury in mice.

Translocation of enteric bacteria from the gut to the mesenteric lymph nodes and beyond can cause life-threatening infection and multiple-organ failure in immunocompromised and traumatized patients. One of the conditions that promotes bacterial translocation is disruption of the normal gut flora, which results in bacterial overgrowth. In vitro methods were used to determine whether the fibers pectin, cellulose, chitosan, kaolin, lignin, or soy had bactericidal properties. Our results indicated that only chitosan and lignin significantly reduce microbial growth in vitro. A burned mouse model (20% total-body surface area) was used to study the effects of dietary lignin, cellulose, pectin, and chitosan on burn-induced bacterial translocation. Animals were fed a standard mouse diet containing no fiber, pectin, cellulose, lignin, or chitosan (10% of diet) for 14 days ad libitum. On day 14, all animals were burned. Four hours later the animals were killed and the mesenteric lymph nodes, spleen, liver, and cecum were aseptically harvested for determination of quantitative aerobic microbial growth. The animals which received chitosan, and lignin to a lesser extent, added to their diet had significantly lower levels of bacteria in the cecum, mesenteric lymph nodes, and liver. We suggest that addition of chitosan and possibly lignin to the diet may reduce the amount of bacterial translocation after burn injury, presumably by reducing the bacterial population of the cecum.