The in vivo efficacy of ciprofloxacin or pefloxacin alone or in combination with fosfomycin was evaluated in experimental aortic valve endocarditis induced in 133 rabbits by a multidrug-susceptible or multidrugresistant strain of Pseudomonas aeruginosa. Therapy was initiated early (12 h after infection), when bacterial counts in aortic valve vegetations were relatively low, or late (48 h after infection), when vegetations contained a larger inoculum. Antibiotics were administered as a continuous 24-h intravenous infusion. Mean steady-state levels of ciprofloxacin (64 mg/kg), pefloxacin (64 mg/kg), and fosfomycin (300 mg/kg) in serum were 2.5, 4.2, and 63.9 mg/liter, respectively. For the multidrug-susceptible strain, all regimens except pefloxacin alone significantly reduced the number of CFU per gram of vegetation versus controls, whether treatment was performed early or late. For the multidrug-resistant strain, none of the regimens showed differences from untreated controls, except ciprofloxacin-fosfomycin, which significantly reduced bacterial counts in vegetations compared with controls when therapy was begun early (4.1 ؎ 1.1 log 10 CFU/g of vegetation; P < 0.001 versus the control). These data suggest that combination of fosfomycin with ciprofloxacin or pefloxacin is more effective than ciprofloxacin or pefloxacin alone for the therapy of severe infections caused by multidrugsusceptible P. aeruginosa.Severe infections caused by Pseudomonas aeruginosa are a major problem in hospitalized patients who often fail to respond to medical therapy alone (2, 23). Fluoroquinolones are frequently used in the treatment of severe gram-negative infectious diseases, and ciprofloxacin and pefloxacin have proved effective against certain P. aeruginosa infections (10). However, clinical failures have occurred because of the development of resistance during therapy (22, 23) and there has also been a worldwide emergence of P. aeruginosa strains resistant to multiple older antimicrobial agents. These events indicate a need for experimental animal studies with newer antipseudomonal regimens. Antimicrobial combinations have been proposed as a means of increasing bactericidal activity in vivo, and some data suggest a possible synergy of fluoroquinolones with other antimicrobial agents (5,14,20). Moreover, fosfomycin, a drug with remarkable activity against P. aeruginosa, has shown a synergistic bactericidal effect in vitro against multidrug-resistant P. aeruginosa when combined with ciprofloxacin (12,20).The present study was designed to evaluate the efficacy of ciprofloxacin or pefloxacin alone versus association with fosfomycin. Experiments were conducted with a rabbit model of aortic valve endocarditis induced by a multidrug-susceptible or multidrug-resistant strain of P. aeruginosa. MATERIALS AND METHODSMicroorganisms. Two clinical strains of P. aeruginosa isolated from the blood of burn unit patients with septicemia were found to be susceptible (PA1) or resistant (PA2) to multiple antibiotics. Both proved resistant to rabbit s...

Triple negative breast cancer (TNBC) is a tumor subtype characterized by the absence of overexpressed estrogen receptor-alpha (ER), progesterone receptor (PR), and HER2 receptor, encoded by ERBB2, a known proto-oncogene. This type of tumors account for approximately 15–25% of breast cancers at diagnosis, and is one of the most aggressive subtypes, with 77% of patients that live free of disease 5 years post-diagnosis. One of the most reliable predictive markers of patient outcome is the pathological complete response (pCR), which indicates that the surgical specimen removed after neoadjuvant chemotherapy contains no viable tumor cells detectable at histopathological level. For patients with pCR, the probability of surviving the disease is very high, however, pCR is observed only in about 20–30% of TNBC. On the other hand, for patients with no pCR the probablity of developing recurrent disease at 5 years is 50%.\ud \ud As pCR is strongly correlated with treatment efficacy, it is mandatory to develop methods that allow to tell as quick as possible if the treatment chosen for a given patient is efficiently working or if it should be abandoned in favor of an alternative strategy that could prove more efficacious. XenTech collection of breast cancer patient-derived xenografts (PDXs) includes 25 models of TNBC that display heterogeneous response to different chemotherapy agents. We used our models to investigate if transcriptional changes could be detected in PDXs that responded well to genotoxic agents. To do this we analyzed the gene expression profile of laser-microdissected residual tumor nodules interspersed in the murine stroma upon very efficient response to Adriamycin/Cyclophosphamide (AC). When doing so, we identified several genes of the IFN/STAT1 pathway that were over-expressed when compared to untreated tumors. This activation seems to be a transient event, as it was lost in tumors relapsing after the residual tumor nodule stage.\ud \ud The finding that residual cells from tumors strongly responding to AC treatment over-expressed IFN/STAT1 pathway-related genes prompted us to investigate whether this effect could be detected as an early event upon tumor exposure to chemotherapy. All TNBC models tested that were good responders to AC treatment displayed over-expression of IFN/STAT1 pathway-related genes as early as 3 days post-treatment, most of them reaching a plateau of intensity at day 7 post-treatment. By contrast, TNBC insensitive or low responders to AC treatment failed to show over-expression of IFN/STAT1 pathway-related genes.\ud \ud To verify if the selective over-expression of these genes in TNBC models sensitive to AC was independent of the treatment administered, Irinotecan and Capecitabine were used to treat TNBC models with heterogeneous response to these drugs. Again, we found that overexpression of IFN/STAT1 pathway-related genes was specifically identified at early stages only in TNBC models that responded well to these drugs.\ud \ud These results suggest that genes of the IFN/STAT1 pathway ...

Despite considerable efforts in understanding the biology and genetics of cancer, most currently available treatments fail to achieve tumor eradication in the majority of patients. Key to more effective therapies is adequate disease classification and subsequent patient stratification. In addition, it is important to understand the mechanisms of drug-response or resistance and identify novel targets amenable to therapeutic intervention. It is increasingly recognized that at the preclinical stage, testing therapeutic strategies and validating target relevance in more predictive models closely mimicking clinical disease such as patient derived xenografts (PDXs), may translate into improved clinical efficacy and lower rate of drug attrition. XenTech collection of over 120 runing PDX models is one of the largest in the world. PDX models were established by grafting post-surgery human tumor fragments in the interscapular region of immunodeficient mice. These deeply characterized PDX models can be used for in vivo preclinical assays. Such preclinical platform is a reliable surrogate of patient cohorts and can address several aims: 1. Evaluate tumor response to treatment. PDXs can be subjected to parallel evaluation of tumor response to various treatment protocols. Drug-response profile is linked to tumor histotype and molecular features in order to identify predictive markers of drug response to assist treatment choice. 2. Assess treatment-driven tumor eradication. The ability of a treatment to induce complete tumor response is assessed by monitoring tumor regression over a long period. Most tumors, despite complete macroscopic regression, are still present as latent microscopic nodular islands that may give rise to tumor recurrence. Molecular characterization of tumor foci responsible for tumor relapse may be performed to identify genes/pathways involved in residual tumor cell survival, which may provide new diagnostic and/or therapeutic targets for designing novel adjuvant treatment strategies. 3. Development of bioluminescent metastatic models to study the mechanisms of tumor invasion and to test anti-metastatic therapy. 4. Non-invasive molecular imaging technology to monitor tumor metabolism, vascularization and apoptosis. 5. Constitution of preclinical panels of rare malignancies to obtain phase II-like tumor cohorts. Development of new therapies for rare tumors is rendered difficult by the unavailability of patient cohorts wide enough to set up robust clinical trials. To assist the clinical need, these panels would allow the evaluation of new and more efficient therapies. We describe here in detail our PDX collection and illustrate how it represents a powerful tool to identify preferential therapeutic options for patients by exploring and improving anti-cancer therapeutic strategies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5273. doi:1538-7445.AM2012-5273

Background: The ability of tumor cells to spread and form metastasis is one of the key parameters used to classify tumor aggressiveness. Metastasis detection at diagnosis or during follow-up post-surgery is associated with poor prognosis. The lack of pertinent models to investigate the biology of metastasis renders problematic the set-up of anti-metastasis therapies. We took advantage of our tumorgraft collection to develop models suitable to assess anti-metastatic therapy. Furthermore, to enable measurement of metastasis response to treatment, we labeled tumors with lentivirus-mediated luciferase insertion into tumor cells, allowing the follow up of metastasis formation by non invasive imaging. Methods: In order to obtain a bioluminescent model, upon tumor resection, HBCx-12B tumor cells were dissociated and transduced with a defective lentivirus bearing the firefly luciferase gene. One million cells were injected subcutaneously in different strains of immunocompromised mice (RAG γC−/−; RAG γC−/− FLK; Nude; SCID; NOD SCID), tumor growth and metastasis formation were monitored throughout passages by whole body visualization using the Xenogen IVIS® Lumina. Mice were imaged over 10 to 24 weeks, and in order to prolong the follow-up window for metastasis detection, tumor resection was performed when primary tumor size reached 500 mm3. During this period, bioluminescence was measured every two weeks to assess metastasis appearance and progression. Bio-imaging allowed metastasis detection with a threshold of 100 to 400 cells per metastatic focus. The presence of metastases was confirmed by both histological analysis, and ex vivo organ fluorescence imaging. The pro-drug 5-aminolevulinic acid was injected intravenously, transformed into protoporphyrin IX, a fluorescent compound accumulated into tumor cells. Results: Metastases developped in all tested strains with different efficiency. RAG γC −/− and SCID strains had the highest susceptibility, with fast and high metastasis incidence. RAG γC (9/9), RAG γC−/− FLK (2/2) and SCID (4/5) mice presented lung metastases after an average of 50-day independently of the passage, while metastases developed in 1/7 in nude mice after 90 days. Histological examination confirmed the adenocarcinomatous origin of metastases, extravading into the lung arteriolar vessels. Conclusions and perspectives: Bioluminescent metastasis models could be successfully established by growing luciferase-enginered tumorgrafts into appropriate strains of immunocompromised mice. At present, other bioluminescent models of melanoma, pancreatic, and breast cancer tumorgrafts are being validated as metastatic. The establishment of bioluminescent metastasis models of different types of cancer will provide an useful tool to explore the biology of metastasis development and anti-metastatic therapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C47.

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