Expression of p53, or targeting towards EGFR, enhances the oncolytic potency of conditionally replicative adenovirus against neuroblastoma.

BACKGROUND: Advanced stage and relapsing neuroblastoma (NB) has a poor prognosis with frequent treatment failures, warranting new treatment options and enhanced local tumor control. Treatment with conditionally replicative adenoviruses (CRAds) has shown effectiveness in various preclinical cancer models, but has not yet been evaluated for local control of NB. Here, we tested the efficacy of the CRAd AdDelta24 and of two AdDelta24 derivatives against NB. Derivative AdDelta24-425S11 infects cells deficient in coxsackie/adenovirus receptor (CAR) via the epidermal growth factor receptor (EGFR). Derivative AdDelta24-p53 expresses the tumor suppressor protein p53 to promote oncolysis. METHODS: Expression of CAR and EGFR, and p53 pathway and DNA damage responses were analyzed in six NB cell lines and two xenografts derived from primary NB using immunohistochemistry, reporter gene transactivation, Western blot and fluorescence-activated cell sorting (FACS) analysis. Efficacy of AdDelta24, AdDelta24-425S11 and AdDelta24-p53 against NB was evaluated in vitro by cell viability analysis and in vivo by monitoring subcutaneous xenograft tumor growth in mice and by histological analysis of treated tumors. RESULTS: Neuroblastoma cell lines were sensitive to oncolysis by AdDelta24, with a higher susceptibility of those with functional p53 and intact DNA damage responses. Compared to AdDelta24, AdDelta24-p53 exhibited enhanced oncolytic potency on all NB cell lines independent of their p53 status and AdDelta24-425S11 was more effective against CAR-low IGR-NB8 cells. Moreover, five daily intratumoral injections of 10(8) plaque-forming units (pfu) of AdDelta24-p53 or AdDelta24-425S11 into subcutaneous IGR-NB8 and IGR-N91 xenografts at an advanced tumor stage yielded significant tumor growth delays (TGD). In contrast, at this dose, AdDelta24 did not cause significant TGD of neuroblastoma xenografts. Injection of AdDelta24-p53 was associated with extensive cell lysis, apoptotic cell death, and fibrous fascicles in the tumors. CONCLUSION: CRAds expressing p53 and targeted towards EGFR appear promising new agents for local control in the treatment of neuroblastoma.

In vivo echographic evidence of tumoral vascularization and microenvironment interactions in metastatic orthotopic human neuroblastoma xenografts.

Human neuroblastoma (NB) is the second most frequent solid tumor of childhood and represents a highly heterogeneous disease at clinical and biologic levels. Little progress has been made to improve the poor prognosis of patients with high-stage NB. Tumor progression and metastatic dissemination still represent major obstacles to the successful treatment of advanced stage disease. In order to develop and evaluate new, targeted, therapeutic strategies, fully defined and biologically relevant in vivo models of NB are strongly needed. We have developed an orthotopic model of metastatic human NB in the nude mouse, using 2 well-characterized NB cell lines. Tumor growth, vascular properties and metastatic patterns were investigated using a sensitive and newly developed in vivo echographic technology in addition to immunohistochemistry and PCR analyses. Results show that implantation of low numbers of NB cells directly into the adrenal gland of nude mice resulted in rapid and homogeneous tumor growth without tumor morbidity. Nude mice were shown to rapidly develop highly vascularized adrenal tumors that selectively metastasized to the liver and bone marrow. In addition, the newly formed mouse vessels in orthotopic but not in heterotopic tumors, were found to express the highly angiogenic alphavbeta3 integrin marker, indicating the development of a truly malignant neovasculature in orthotopic conditions only. This observation confirms the impact of the regional microenvironment on tumor biology and suggests the existence of cross-talk with the tumor cells. In conclusion, such model faithfully reproduces the growth, vascular and metastatic patterns as observed in patients. It therefore represents a powerful and biologically relevant tool to improve our understanding of the biology of NB and to develop and assess new antiangiogenic and metastasis-targeted therapies.

Negative preclinical results with stealth nanospheres-encapsulated Doxorubicin in an orthotopic murine brain tumor model.

Previous results have shown that PEG-coated poly(hexadecylcyanoacrylate) (PEG-PHDCA) nanospheres displayed a significant accumulation within an orthotopic 9L gliosarcoma model, after i.v. administration to rats. Hence, the aim of the present study was to evaluate in the same model the pre-clinical efficacy of this carrier when loaded with Doxorubicin, an anticancer drug which poorly distributes in the CNS. Free and nanospheres-encapsulated Doxorubicin were administered with a multiple dose treatment. Their maximum tolerated dose (MTD) and increase in life span were respectively assessed in healthy and intracranially 9L-bearing rats. A comparative biodistribution study of Doxorubicin-loaded and unloaded PEG-PHDCA nanospheres was also performed in the tumor-bearing group. The results showed that the cumulative MTD of nanoparticulate doxorubicin was 1.5 times higher than this of free Doxorubicin. Nevertheless, encapsulated Doxorubicin was unable to elicit a better therapeutic response in the 9L gliosarcoma. Biodistribution study revealed that the Doxorubicin-loaded nanospheres accumulated to a 2.5-fold lesser extent in the 9L tumor as compared to the unloaded nanospheres and that they were mainly localized in the lungs and the spleen. Such a typical profile indicated aggregation with plasma proteins as a consequence of the positive surface charge of these loaded particles; this ionic interaction resulting from drug encapsulation was mainly responsible for 9L treatment failure.

Oncolytic activity of p53-expressing conditionally replicative adenovirus AdDelta24-p53 against human malignant glioma.

Prognosis of malignant glioma is poor, and results of treatment remain mediocre. Conditionally replicative adenoviruses hold promise as alternative anticancer agents for the treatment of malignant glioma. Here, we evaluated the conditionally replicative adenovirus AdDelta24 and its recently developed derivative AdDelta24-p53, which expresses functional p53 tumor suppressor protein while replicating in cancer cells, for treatment of malignant glioma. In comparison to its parent AdDelta24, AdDelta24-p53 killed most malignant glioma cell lines and primary glioblastoma multiforme short-term cultures more effectively, irrespective of their p53 status. Moreover, AdDelta24-p53 caused more frequent regression and more delayed growth of IGRG121 xenografts derived from a glioblastoma multiforme in vivo. Five intratumoral injections of 10(7) pfu AdDelta24 gave 24 days median tumor growth delay (P < 0.01), 30% tumor regressions, and 30% animals surviving >120 days tumor-free or with a minimal tumor residual. The same dose of AdDelta24-p53 caused >113 days of median tumor growth delay (P < 0.001), 70% tumor regressions, and 60% animals surviving >120 days tumor-free or with a minimal tumor residual. Antitumor effects in vivo were associated with extensive conditionally replicative adenovirus replication, apoptosis induction, and tumor morphology changes, including dissociation, inflammatory cell infiltration, and necrosis. We conclude that conditionally replicative adenoviruses expressing p53 are promising new agents for treatment of malignant glioma.