Patrice Ardouin

Electrochemotherapy on liver tumours in rabbits.

Electrochemotherapy (ECT) is a new therapeutic approach combining the effects of a low-permeant cytotoxic drug, bleomycin (BLM), administered i.v. and cell-permeabilizing electric pulses (EPs) locally delivered to tumours. The transient permeabilization of the cell membrane by the EPs allows free access of BLM to its intracellular targets, largely enhancing BLMs cytotoxic effects. ECT efficacy has been proved so far on transplanted subcutaneous murine tumours and on subcutaneous metastases in humans. Here, we present the first study of the effects of ECT on tumours transplanted to livers in rabbits. We used a recently developed EP applicator consisting of an array of parallel and equidistant needles to be inserted in tissues. Effects of EPs alone or of ECT were assessed by histological analysis, tumour growth rates and survival of the treated animals. A transient blood hypoperfusion was seen in the electropulsed areas, with or without BLM, related to EP-dependent vasoconstriction but this had no major effects on cell survival. Long-term effects depended on the presence of BLM at the time of EP delivery. Almost complete tumour necrosis was observed after ECT, resulting from both BLM direct cytotoxic effects on electropermeabilized tumour cells and indirect effects on the tumour vessels. A large reduction in tumour growth rate and significantly longer survival times were scored in comparison with control rabbits. Moreover, ECT of liver tumours was well tolerated and devoid of systemic side-effects. When ECT was associated with a local interleukin 2-based immunotherapy, increased local anti-tumour effectiveness as well as a large decrease in the number of metastases were observed. Thus, ECT could become a novel treatment modality for liver tumours and other solid internal malignancies.

Therapeutic activity of CPT-11, a DNA-topoisomerase I inhibitor, against peripheral primitive neuroectodermal tumour and neuroblastoma xenografts.

The anti-tumour activity of CPT-11, a topoisomerase I inhibitor, was evaluated in four human neural-crest-derived paediatric tumour xenografts; one peripheral primitive neuroectodermal tumour (pPNET) (SK-N-MC) and three neuroblastomas. Two models, SK-N-MC and IGR-N835, were established in athymic mice from a previously established in vitro cell line. Two new neuroblastoma xenograft models, IGR-NB3 and IGR-NB8, were derived from previously untreated non-metastatic neuroblastomas. They exhibited the classic histological features of immature neuroblastoma along with N-myc amplification, paradiploidy, chromosome 1p deletions and overexpression of the human mdr 1 gene. These tumour markers have been shown to be poor prognostic factors in children treated for neuroblastoma. CPT-11 was tested against advanced stage subcutaneous tumours. CPT-11 was administered i.v. using an intermittent (q4d x 3) and a daily x 5 schedule. The optimal dosage and schedule was 40 mg kg-1 daily for 5 days. At this highest non-toxic dose, CPT-11 induced 100% tumour-free survivors on day 121 in mice bearing the pPNET SK-N-MC xenograft. For the three neuroblastoma xenografts, 38-100% complete tumour regressions were observed with a tumour growth delay from 38 to 42 days, and anti-tumour activity was clearly sustained at a lower dosage (27 mg kg-1 day-1). The efficacy of five anti-cancer drugs commonly used in paediatric oncology or in clinical development was evaluated against SK-N-MC and IGR-N835. The sensitivity of these two xenografts to cyclophosphamide, thiotepa and cisplatin was of the same order of magnitude as that of CPT-11, but they were refractory to etoposide and taxol. In conclusion, CPT-11 demonstrated significant activity against pPNET and neuroblastoma xenografts. Further clinical development of CPT-11 in paediatric oncology is warranted.

Radiation and inhibition of angiogenesis by canstatin synergize to induce HIF-1α–mediated tumor apoptotic switch

Tumor radioresponsiveness depends on endothelial cell death, which leads in turn to tumor hypoxia. Radiation-induced hypoxia was recently shown to trigger tumor radioresistance by activating angiogenesis through hypoxia-inducible factor 1-regulated (HIF-1-regulated) cytokines. We show here that combining targeted radioiodide therapy with angiogenic inhibitors, such as canstatin, enhances direct tumor cell apoptosis, thereby overcoming radio-induced HIF-1-dependent tumor survival pathways in vitro and in vivo. We found that following dual therapy, HIF-1alpha increases the activity of the canstatin-induced alpha(v)beta(5) signaling tumor apoptotic pathway and concomitantly abrogates mitotic checkpoint and tetraploidy triggered by radiation. Apoptosis in conjunction with mitotic catastrophe leads to lethal tumor damage. We discovered that HIF-1 displays a radiosensitizing activity that is highly dependent on treatment modalities by regulating key apoptotic molecular pathways. Our findings therefore support a crucial role for angiogenesis inhibitors in shifting the fate of radiation-induced HIF-1alpha activity from hypoxia-induced tumor radioresistance to hypoxia-induced tumor apoptosis. This study provides a basis for developing new biology-based clinically relevant strategies to improve the efficacy of radiation oncology, using HIF-1 as an ally for cancer therapy.

Pharmacokinetics and antitumor effects of mitoxantrone after intratumoral or intraarterial hepatic administration in rabbits

Abstract The intratumoral (i.t.) delivery of anticancer drugs aims at controlling tumor growth and thereby provides palliative treatment for liver neoplasms. Mitoxantrone is a good candidate for local or regional administration because (1) its metabolism is mainly hepatic, (2) it has a steep dose-response curve for multiple solid tumors, and (3) its fixation in tissues is sustained without vesicant effects after extravasation. We compared the tolerance, pharmacokinetics, and antitumor effects of mitoxantrone on hepatic VX2 tumors in rabbits treated with i.t. intraarterial hepatic (i.a.h.) or i.v. mitoxantrone, i.t. ethanol; or i.t. 0.9% NaCl and in control animals. Tumor growth rates (TGRs) were evaluated at 9 days after treatment. Myelosuppression was the limiting toxicity of i.v. mitoxantrone at 1.5 mg/kg (maximal tolerated dose, MTD), but neither i.t. nor i.a.h. administration led to hematologic toxicity at the same dose. The mitoxantrone retained in tumors after i.t. administration was seen as blue-stained areas of complete necrosis according to histologic analysis. Pharmacokinetic parameters showed a significantly decreased systemic exposure to the drug after both regional treatments, although the i.a.h. route appeared to have an edge over the i.t. route. TGRs were significantly reduced after i.t. mitoxantrone (81±62%), i.a.h. mitoxantrone (337±110%), and i.t. ethanol treatments (287±117%) as compared with control values (886±223%; p<0.01). Treatment with i.v. mitoxantrone (816±132%) had no antitumor effect, nor did NaCl injections (868±116%). Mitoxantrone given i.t. induced the highest antitumor effects, resulting in a 3.5-fold reduction in TGRs as compared with i.a.h. mitoxantrone and i.t. ethanol treatments (p<0.02). Treatment with i.t. mitoxantrone provided efficient antitumor therapy without producing major side effects. This method should be considered as palliative treatment for nonresectable liver tumors and other localized malignancies.

Tumorigenicity of cerebellar primitive neuro-ectodermal tumors in athymic mice correlates with poor prognosis in children

The histogenesis of medulloblastoma, also described as a cerebellar primitive neuro‐ectodermal tumor (PNET), remains controversial and unresolved. In addition, genetic markers which characterize cerebellar PNETs with poor prognosis in children have not been identified. Since xenografts can be valuable tools for better understanding the genetic events involved in cerebellar PNETs, small fragments of tumor samples from 17 children with newly diagnosed cerebellar PNETs were transplanted s.c. into female athymic Swiss mice. Eleven were non‐metastatic and 6 were metastatic PNETs. Eight tumors (47%) were tumorigenic. Histological analysis showed 6 typical medulloblastomas, 1 PNET with melanin pigment and 1 PNET with a rhabdoid phenotype. Wide heterogeneity was observed in tumor growth, with a doubling time ranging from 8 to 81 days after the first passage. Tumorigenicity was correlated with the metastatic phenotype of the tumor (p < 0.001). All the patients but one with a tumorigenic tumor relapsed and died. The survival of patients with a non‐tumorigenic PNET (67%) was significantly higher than that of patients with a tumorigenic PNET (13%) (p < 0.02). None of the xenografts or tumors from patients exhibited N‐myc‐gene alteration. Only one xenograft showed c‐myc amplification, with an abnormal 15‐kilobase fragment. None of the 17 tumors from patients showed amplification or c‐myc‐gene rearrangement. In conclusion, tumorigenicity of cerebellar PNETs strongly correlates both with the metastatic phenotype of the tumors and with the disease‐free survival of the patients. In addition, genetic events other than c‐myc‐gene amplification might be involved in cerebellar PNETs with poor prognosis.

Pharmacology and antitumour effects of intraportal pirarubicin on experimental liver metastases

Early liver metastases have a predominant portal blood supply. Intraportal (i.port.) vein administration of cytotoxics could theoretically achieve enhanced drug concentrations in tumour cells and be effective as adjuvant therapy after resection of colorectal carcinoma. Pirarubicin (which has a higher hepatic extraction than doxorubicin) was investigated on liver metastases of the VX2 rabbit tumour, which were of less than 2 mm in diameter 7 days after cells injection into the portal vein. To evaluate antitumour activity, 24 rabbits were randomised into three groups 7 days after implantation: (a) control, (b) i.v. pirarubicin, (c) i.port. pirarubicin at doses of 2 mg kg-1 in both groups. Portal infusions led to no hematological or hepatic toxicity. Pharmacokinetic parameters showed a significantly reduced systemic exposure after i.port. administration. Fourteen days after treatment, livers and lungs were analysed. The mean number (+/- s.d.) of tumour foci was (a) 8.62 (+/- 5.4), (b) 4.62 (+/- 3.2), (c) 2.25 (+/- 1.4) (P < 0.05 a vs c). The mean tumour area was (a) 6.31 (+/- 6.1), (b) 1.31 (+/- 2.2), (c) 0.43 (+/- 0.4 cm2) (P < 0.05 a vs c) and the percentage (95% C.I.) of rabbits with lung metastasis was: (a) 87.5% (47-99%), (b) 75% (35-97%), (c) 12.5% (3-52%) (P < 0.02 b vs c). Intraportal pirarubicin seems to be well tolerated and more efficient than i.v. administration, particularly in preventing extrahepatic dissemination.

IL-2 production by dendritic cells is not critical for the activation of cognate and innate effectors in draining lymph nodes

Dendritic cells (DC) are unique antigen‐presenting cells capable of triggering NK cell effector functions and priming naive T cells in vivo. Microbial stimulation induces early IL‐2 production by mouse DC. Previous reports demonstrated that IL‐2 is enriched at the site of DC/T cell interaction and promotes allogeneic T cell proliferation. However, the direct role of DC‐derived IL‐2 in the differentiation of cytotoxic T lymphocytes and in NK cell triggering in vivo has not been investigated. Lipopolysaccharide (LPS) stimulation of mouse bone morrow‐derived DC results in early IL‐2 production unless IL‐4 is introduced in DC cultures. Here we show that IL‐2 produced by LPS‐activated DC is dispensable for cognate T cell responses since IL‐2 loss of function DC elicit OVA‐specific Tc1 effector and memory lymphocytes in draining lymph nodes in a setting where ex vivo cultured DC do not transfer antigens to host DC. Moreover, adoptively transferred IL‐2 loss of function DC maintain their capacity to trigger NK cell proliferation/recruitment in lymph nodes. Therefore, immediate inducible IL‐2 production by DC following microbial infection might play a regulatory role at ports of entry rather than in secondary lymphoid organs.

Verapamil-reversing concentrations induce blood flow changes that could counteract in vivo the MDR-1-modulating effects.

Background. Intraarterial hepatic (IAH) administration of verapamil should achieve mdr‐1‐reversing concentrations with reduced cardiac toxicity. The authors have explored the tolerance of its IAH administration and its effects on doxorubicin pharmacodynamics.