Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “preclinical models”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2002

Synergistic antitumor effect of bispecific CD19 x CD3 and CD19 x CD16 diabodies in a preclinical model of non-Hodgkin's lymphoma.

To target NK cells against non-Hodgkin's lymphoma, we constructed a bispecific diabody (BsDb) with reactivity against both human CD19 and FcgammaRIII (CD16). Bacterially produced CD19 x CD16 BsDb specifically interacted with both CD19(+) and CD16(+) cells and exhibited significantly higher apparent affinity and slower dissociation from the tumor cells than from effector cells. It was able to induce specific lysis of tumor cells in the presence of isolated human NK cells or nonfractionated PBLs. The combination of the CD19 x CD16 BsDb with a previously described CD19 x CD3 BsDb and CD28 costimulation significantly increased the lytic potential of human PBLs. Treatment of SCID mice bearing an established Burkitt's lymphoma (5 mm in diameter) with human PBLs, CD19 x CD16 BsDb, CD19 x CD3 BsDb, and anti-CD28 mAb resulted in the complete elimination of tumors in 80% of animals. In contrast, mice receiving human PBLs in combination with either diabody alone showed only partial tumor regression. These data clearly demonstrate the synergistic effect of small recombinant bispecific molecules recruiting different populations of human effector cells to the same tumor target.

Animals↗
PubMed1999

Paclitaxel and radiotherapy: sequence-dependent efficacy--a preclinical model.

The optimal sequence of a paclitaxel-radiation combination was investigated in vitro in two human colon adenocarcinoma cell lines, HT29 and LoVo. Three schedules of combined treatment were tested by clonogenic and flow cytometric assays. Paclitaxel was given 24 h prior to a single radiation shot (first schedule) or 24 h (second schedule) or 48 h (third schedule) before 3 days of concomitant radiation. Dose-response data were fit to a linear quadratic model, and mean inactivation dose and sensitizer enhanced ratio were calculated. In HT29 cells, the first and second schedule resulted in an additive effect, whereas a supraadditive interaction was observed with the third combination schedule. This effect was obtained with amounts of paclitaxel lower than IC50, which did not result in cell cycle perturbation, and with low radiation dose (2 Gy) that may be given in a clinical setting. LoVo cells were less sensitive to combined treatment than HT29 cells, switching from infraadditive (first and second schedule) to additive interaction (third schedule). Posttreatment recovery studies of third schedule showed a loss of cell survival in HT29 cells but not in LoVo cells. In contrast to LoVo cells, the third schedule in HT29 cells was able to induce perturbation of cell cycle kinetics, an effective impairment of DNA repair, and apoptotic cell death. HT29 and LoVo cells showed constitutional different characteristics: HT29 cells were more sensitive to paclitaxel exposure, less radiosensitive, and had a different cell cycle redistribution after radiation exposure than LoVo cells; moreover, HT29 cells showed a major propensity to undergo apoptosis. These results suggest that the radiosensitizing effect of paclitaxel was strictly schedule dependent, and the inhibition of DNA repair, cell cycle redistribution, and apoptosis could be the mechanisms for the induction of radiosensitization by paclitaxel.

Adenocarcinoma↗
PubMed2000

Balb/c mice as a preclinical model for raltitrexed-induced gastrointestinal toxicity.

Raltitrexed (RTX) is an antifolate thymidylate synthase (TS) inhibitor used for the treatment of advanced colorectal cancer. RTX induces proliferating tissue toxicities that are largely confined to the intestine, with diarrhea being a severe side effect in a small but significant minority of patients. Similarly, weight loss and diarrhea were observed in BALB/c mice, and a maximum tolerated dose (MTD) was determined as approximately 5-10 mg/kg/day x 5 days. At an equivalent dose of 10 mg/kg/day x 5 days (dl-5), DBA2 mice lost considerably less weight, leading to a higher MTD (>500 mg/kg/day x 5 days), and there was no evidence of diarrhea. Histopathological consequences of damage, such as changes in small intestinal crypt architecture and villus atrophy induced by the 10-mg/kg/day dose, were greater and of longer duration in BALB/c mice. A higher dose of RTX (100 mg/kg/day x 5) induced weight loss and histopathological damage similar to that seen in BALB/c mice (10 mg/kg/ day x 5) but was of later onset, nadir, and recovery. Small changes to the colon were only observed in BALB/c mice. Pretreatment levels of plasma thymidine, deoxyuridine (approximately 1 microM), and folate (approximately40 ng/ml) were similar in both mouse strains. A single injection of radiolabeled RTX (5 mg/kg/ day) did not lead to any marked difference 24 h later in the total drug concentration and distribution of polyglutamates (comprising 70-80% of drug extracted) in the liver, kidney, and intestinal epithelium (large and small intestine) between the two mouse strains. Further studies used a RIA to measure RTX polyglutamate formation in tissues at various times and drug doses. This led to the conclusion that, although there was a higher accumulation of RTX in BALB/c small intestinal epithelium (days 4-6), it may be an effect secondary to another undetermined cause of increased drug sensitivity. This model represents a vehicle by which the etiology and treatment of severe clinical toxicity induced by RTX may be evaluated.

Animals↗
PubMed2000

Direct identification of human tumor-associated peptide antigens and a preclinical model to evaluate their use.

Although the arsenal of a healthy immune system includes both circulating antibodies and cellular components such as T cells, the latter seem to be particularly important in tumor immunology. Under normal conditions, the immune system does not react to the body's cells, which may be described as expressing "self" antigens on the cell surface. When a cell becomes cancerous, however, novel antigens are expressed on the cell surface. These novel "tumor" antigens are recognized as foreign by the body's immune system, and the cells that express them are destroyed or incapacitated. Whereas antibodies may react directly with protein antigens, T cells instead recognize peptide antigens presented by class I and class II molecules of the major histocompatibility complex (MHC). All cells normally break down proteins that they have made. The class I antigen-processing pathway has evolved to display peptides produced by this breakdown process as a way to provide information to cytotoxic T cells about what the cell is making. The display of new peptides as a result of infection or transformation can stimulate cytotoxic T cells to kill the cell. In addition, antigen-processing cells such as dendritic cells engulf dead or dying cells and degradeproteins into peptide fragments. These peptides are then displayed by the MHC class II molecules and presented to T helper cells, which augment the activity of the cytotoxic T cells. Cytotoxic T lymphocytes have recently been isolated from human tumors (especially melanoma) and are critical to the development of promising immunotherapeutic agents. As we shall discuss, these cells can recognize antigens that are common to tumors from different patients. We shall also explore how advances in instrumentation and the use of transgenic mice have increased our understanding of tumor-associated peptides to the point where we can begin to strive for a peptide-based therapeutic vaccine. The caveats for such therapy will also be addressed.

Animals↗
PubMed2001

Angiogenesis inhibitor TNP-470 during bone marrow transplant: safety in a preclinical model.

High-dose therapy with stem cell rescue is a treatment option for patients with advanced solid tumors. Although this approach has promise for some pediatric cancers, especially neuroblastoma, it is limited by the risk of relapse posttransplant as well as concern about possible reinfused tumor cells in autologous stem cell products. Antiangiogenic agents given during and after recovery from high-dose therapy with stem cell rescue may decrease the risk of relapse. TNP-470 is an antiangiogenic agent now in clinical trials. Although it inhibits the growth of bone marrow (BM) colony-forming cells in vitro, no significant hematological toxicity has been seen in Phase I trials. To assess the feasibility of using antiangiogenic agents during the period of posttransplant hematopoietic engraftment, we have developed a model of stem cell transplant in mice. Mice were lethally irradiated and then rescued with stem cells containing a transgene expressed in the hematopoietic lineage. Mice were then treated with TNP-470 or placebo, and assessed for survival, successful engraftment, and kinetics of engraftment. Both treated and control mice demonstrated reliable multilineage engraftment as well as normal lymphoid maturation with no excess mortality in the treated group. WBCs were lower but still within the normal range at d+28 in mice treated with bolus TNP-470, but not in those treated with continuous infusion TNP-470, compared with controls. These data indicate that inhibitors of angiogenesis do not adversely impact engraftment after stem cell transplantation.

Angiogenesis Inhibitors↗
PubMed2001

Evaluation of farnesyl:protein transferase and geranylgeranyl:protein transferase inhibitor combinations in preclinical models.

Farnesyl:protein transferase (FPTase) inhibitors (FTIs) were originally developed as potential anticancer agents targeting the ras oncogene and are currently in clinical trials. Whereas FTIs inhibit the farnesylation of Ha-Ras, they do not completely inhibit the prenylation of Ki-Ras, the allele most frequently mutated in human cancers. Whereas farnesylation of Ki-Ras is blocked by FTIs, Ki-Ras remains prenylated in FTI-treated cells because of its modification by the related prenyltransferase, geranylgeranyl:protein transferase type I (GGPTase-I). Hence, cells transformed with Ki-ras tend to be more resistant to FTIs than Ha-ras-transformed cells. To determine whether Ki-ras-transformed cells can be targeted by combining an FTI with a GGPTase-I inhibitor (GGTI), we evaluated potent, selective FTIs, GGTIs, and dual prenylation inhibitors (DPIs) that have both FTI and GGTI activity. We find that in human PSN-1 pancreatic tumor cells, which harbor oncogenic Ki-ras, and in other tumor lines having either wild-type or oncogenic Ki-ras, treatment with an FTI/GGTI combination or with a DPI blocks Ki-Ras prenylation and induces markedly higher levels of apoptosis relative to FTI or GGTI alone. We demonstrate that these compounds can inhibit their enzyme targets in mice by monitoring pancreatic and tumor tissues from treated animals for inhibition of prenylation of Ki-Ras, HDJ2, a substrate specific for FPTase, and Rap1A, a substrate specific for GGPTase-I. Continuous infusion (72 h) of varying doses of GGTI in conjunction with a high, fixed dose of FTI causes a dose-dependent inhibition of Ki-Ras prenylation. However, a 72-h infusion of a GGTI, at a dose sufficient to inhibit Ki-Ras prenylation in the presence of an FTI, causes death within 2 weeks of the infusion when administered either as monotherapy or in combination with an FTI. DPIs are also lethal after a 72-h infusion at doses that inhibit Ki-Ras prenylation. Because 24 h infusion of a high dose of DPI is tolerated and inhibits Ki-Ras prenylation, we compared the antitumor efficacy from a 24-h FTI infusion to that of a DPI in a nude mouse/PSN-1 tumor cell xenograft model and in Ki-ras transgenic mice with mammary tumors. The FTI and DPI were dosed at a level that provided comparable inhibition of FPTase. The FTI and the DPI displayed comparable efficacy, causing a decrease in growth rate of the PSN-1 xenograft tumors and tumor regression in the transgenic model, but neither treatment regimen induced a statistically significant increase in tumor cell apoptosis. Although FTI/GGTI combinations elicit a greater apoptotic response than either agent alone in vitro, the toxicity associated with GGTI treatment in vivo limits the duration of treatment and, thus, may limit the therapeutic benefit that might be gained by inhibiting oncogenic Ki-Ras through dual prenyltransferase inhibitor therapy.

Alkyl and Aryl Transferases↗
PubMed1998

Preclinical models for Chlamydia pneumoniae and cardiovascular disease: hypercholesterolemic mice.

Seroepidemiologic studies have shown an association of Chlamydia pneumoniae antibody with atherosclerosis. Compelling additional evidence has accumulated, in that the organism has been found within atherosclerotic lesions throughout the arterial tree by multiple methods. C. pneumoniae has also been isolated from coronary and carotid atheromatous plaques. Although these studies support a potential role for C. pneumoniae in atherogenesis, confirmation of a causal relationship requires the use of animal models and intervention studies. We have focused on the evaluation of mouse models to address the hypothesis that, following upper respiratory tract infection, lung macrophages are infected, disseminate to the aorta, and alter the onset or progression of atherogenesis. ApoE-deficient knock-out and C57BL/6J mice were used. The apoE-deficient mouse develops atherosclerotic lesions spontaneously on a regular diet in a time- and age-dependent manner. This knock-out strain was developed on the background of the C57BL/6J mouse, which only develops atherosclerosis on a high-fat/high-cholesterol diet. To investigate whether infected macrophages constitute a vehicle for dissemination of C. pneumoniae in vivo, mice were inoculated intranasally or intraperitoneally. The organism was detected in harvested alveolar and peritoneal macrophages at all time points following intranasal and intraperitoneal inoculations, respectively, and in peripheral blood mononuclear cells following inoculation by both routes. In another experiment, alveolar and peritoneal macrophages from intranasally and intraperitoneally inoculated mice were adoptively transferred by intraperitoneal injection to uninfected mice. Subsequently, C. pneumoniae was detected in lung, spleen, abdominal lymph nodes and/or thymus of recipient mice. In control experiments, UV-inactivated C. pneumoniae DNA was not detected in alveolar or peritoneal macrophages beyond 5 min after inoculation in vivo. These cumulative results demonstrate that C. pneumoniae infects macrophages in vivo and that macrophages can serve as a vehicle for dissemination to other sites. To answer the question of whether the organism disseminates to and persists in the aorta, 8-week-old mice were infected intranasally. Following single or multiple inoculations in apoE-deficient mice, C. pneumoniae was detected in the lung and aorta for 20 weeks postinfection. In contrast, in C57BL/6J mice, the organism did not persist in the aorta following a single intranasal inoculation, but could be detected up to 7 weeks postinfection in multiply inoculated mice. Significantly, in apoE-deficient mice with developed atherosclerotic lesions, the organism was found in foam cells within the lesions by immunocytochemical staining. These studies show that persistent C. pneumoniae infection occurs in atherosclerotic lesions in the aorta in the apoE-deficient knock-out mouse model. Infection of the aorta also occurred in C57BL/6J mice but was more transient. Both models should be useful in studying the pathogenic role of C. pneumoniae in atherogenesis and for determining if therapy prevents dissemination of infection. To this end, we have evaluated the susceptibility of C. pneumoniae to roxithromycin, a new macrolide, in vitro in cell culture and in vivo in the apoE-deficient mouse model. In vitro results compare favorably with other new macrolides, quinolines, and tetracyline. Preliminary studies in the apoE model of persistent infection suggest that the organism is detected less frequently in the lung and aorta by PCR following treatment. These promising preliminary studies warrant further investigation.

Journal Article↗
PubMed2003

Tissue engineering of bone and cartilage. From the preclinical model to the patient.

Tissue engineering studies are complex in nature and involve many stages of testing before an experimental construct is ripe for human clinical trials. Biocompatibility questions, toxicological problems, pharmacological aspects, safety issues and proof of the principle itself represent but a few of the concerns that must be addressed. This contribution deals with the different types of animal experiment that are usually undertaken in tissue engineering studies. During the initial phase, small animal models are used to screen all potential components of the proposed construct, such as matrix, cells and signalling substances. In the second, the principle itself is put to the test using an appropriate defect model in a suitable animal species. Careful consideration of these latter two aspects is of paramount importance, many factors having to be considered and special requirements satisfied for meaningful experimentation. Finally, clinically relevant models are set up in animals to furnish basic information respecting the construct's suitability and ripeness for testing in human clinical trials.

Animals↗
PubMedDate not supplied

Resistance developing after long-term ganciclovir prodrug treatment in a preclinical model of NSCLC.

BACKGROUND: We recently demonstrated a 100% increase in the survival period with ganciclovir (GCV) therapy in mice hearing orthotopic HSV-TK-positive non-small cell lung cancer (NSCLC) tumors. However, long-term survival was not achieved. The aim of the present study was to evaluate tumor growth during extended GCV therapy and to monitor the herpes simplex virus thymidine kinase (HSV-TK) gene and protein in tumors at different time points. MATERIALS AND METHODS: The human NSCLC cell line KNS 62 was retrovirally transduced with the HSV-TK30 gene. Cell suspensions in which 100% or 25% of the cells were TK30-positive were inoculated subcutaneously in SCID bg mice. Tumor growth was evaluated during GCV therapy and HSV-TK DNA, RNA and protein were analyzed at different time points using PCR, RT-PCR and immunoblotting. RESULTS: HSV-TK DNA, RNA and TK30 protein were demonstrated in the tumors 21 days after subcutaneous tumor inoculation. TK-positive tumors regressed during GCV therapy and tumors in which 25% of the cells were TK-positive grew significantly more slowly than control tumors did. After 4 weeks of GCV therapy, HSV-TK DNA, RNA and TK protein were not detectable in the remaining tumors, which were therefore resistant to further GCV therapy. CONCLUSION: Prodrug therapy of the NSCLC cell line KNS 62, including bystander effects, is sufficient. Nevertheless, GCV-resistant tumors develop after functional loss of the TK gene. In the clinical context, further studies will need to evaluate immunological bystander effects or combinations with other drugs.

Animals↗
PubMed2005

[Preclinical models of prostate cancer].

Although prostate cancer is a major cause of cancer death and morbidity in Western countries, one major hindrance in the study of the biology of prostate cancer has been the limited number of laboratory models, compared with the number of models available for other neoplasms. For a long time, only three cell lines, namely LNCaP, PC3, and DU145, were routinely used to study prostate cancer in the lab. The success rate to establish cell lines from human prostate cancer tissues is low, in the 1% range. Currently, only about 10 prostate cancer cell lines are available, and many of them do not reproduce typical features of the human disease, like androgen receptor expression or prostate specific antigen (PSA) secretion. Spontaneous models in animals (including rat and dog) are practically not convenient for research purposes. Several in vivo models were artificially established by transforming prostate cells by potent oncogenes. Other models were developed by injecting prostate cancer cell lines into the prostate (orthotopic model), the vessel, or the bones of immuno-deficient mice, to mimic localized and metastatic prostate cancer. This was successfully done with the MDA PCa2b cell line. This cell line was also used to generate an in vitro model of bone metastases by a co-culture system with osteoblasts. This model allows to study the paracrine cross-talk between the two cell compartments and the resulting molecular modifications. The objective of the present article is to review the currently available model systems of prostate cancer.

Animals↗
PubMed1991

The effects of hetrazepine PAF antagonists in preclinical models of asthma.

In different disease related animal models of asthma selective and potent hetrazepine paf-antagonists (like the hetrazepines WEB 2086 and WEB 2170) inhibit (i) allergen-induced bronchoconstriction, (ii) antigen-induced infiltrations of eosinophils, (iii) lung-edema formation by antigen, (iv) late phase response and (v) bronchial hyperreactivity to antigen. In addition the formation and release of other mediators (like leukotrienes, thromboxanes, histamine) are inhibited in vivo, although a direct interaction of hetrazepinoic paf-antagonists with these mediators has been excluded. The participation of paf in a chain of pathophysiological events involving other mediators, and the possibility of synergistic interactions, open up the possibility that antagonists of paf may have apparent effects extending beyond those anticipated for a single mediator.

Anaphylaxis↗