Christophe Chantrain

Advanced stages of neuroblastoma show increased expression of matrix metalloproteinases MMP-2 and MMP-9, that have been implicated in many steps of tumor progression, suggesting that they play a contributory role. Using pharmacological and genetic approaches, we have examined the role of these MMPs in progression of SK-N-BE (2).10 human neuroblastoma tumors orthotopically xenotransplanted into immunodeficient mice. Mice treated with Prinomastat, a synthetic inhibitor of MMPs, showed an inhibition of tumor cell proliferation in implanted tumors and a prolonged survival (50 versus 39 days in control group, P < 0.035). Treatment with Prinomastat did not affect formation of liver metastases (P = 0.52) but inhibited intravascular colonization by the tumor cells in the lung by 73.8% (P = 0.03) and angiogenesis in both primary tumors and experimental liver metastases. The primary tumors from Prinomastat-treated mice showed a 39.3% reduction in endothelial area detected by PECAM/CD31 staining in tumor sections (P < 0.001), primarily due to the presence of smaller vessels (P = 0.004). MMP-2 is expressed by neuroblastoma tumor cells and stromal cells, whereas MMP-9 is exclusively expressed by stromal cells, particularly vascular cells. To examine the contribution of MMP-9 to tumor angiogenesis, we generated RAG1/MMP-9 double-deficient mice. We observed a significant inhibition of angiogenesis in the immunodeficient RAG1/MMP-9 double-deficient mice orthotopically implanted with tumor cells (P = 0.043) or implanted s.c. with a mixture of tumor cells and Matrigel (P < 0.001). Using an FITC-labeled lectin, we demonstrated an inhibition in the architecture of the tumor vasculature in MMP-9-deficient mice, resulting in fewer and smaller blood vessels. These changes were associated with a 48% decrease in pericytes present along microvessels. Taken together, the data demonstrate that in neuroblastoma, stromally derived MMP-9 contributes to angiogenesis by promoting blood vessel morphogenesis and pericyte recruitment.

Autoimmune lymphoproliferative syndrome (ALPS) is a genetic disorder characterized by early-onset, chronic, nonmalignant lymphoproliferation, autoimmune manifestations, and susceptibility to lymphoma. The majority of ALPS patients carry heterozygous germline (ALPS-FAS) or somatic mutations (ALPS-sFAS) of the TNFRSF6 gene coding for FAS. Although the clinical features of ALPS have been described previously, long-term follow-up data on morbidity and mortality are scarce. We performed a retrospective analysis of clinical and genetic features of 90 ALPS-FAS and ALPS-sFAS patients monitored over a median period of 20.5 years. Heterozygous germline mutations of TNFRSF6 were identified in 83% of probands. Somatic TNFRSF6 mutations were found in 17% of index cases (all located within the intracellular domain of FAS). Sixty percent of the ALPS-FAS patients with mutations in the extracellular domain had a somatic mutation affecting the second allele of TNFRSF6; age at onset was later in these patients. No other genotype-phenotype correlations could be found. Long-term analysis confirmed a trend toward spontaneous remission of lymphoproliferation in adulthood but mixed outcomes for autoimmune manifestations. We observed significant and potentially life-threatening disease and treatment-related morbidity, including a high risk of sepsis after splenectomy that calls for careful long-term monitoring of ALPS patients. We also noted a significantly greater occurrence of disease-related symptoms in male than in female patients.

The contribution of the tumor stroma to cancer progression has been increasingly recognized. We had previously shown that in human neuroblastoma tumors orthotopically implanted in immunodeficient mice, stromal-derived matrix metalloproteinase-9 (MMP-9) contributes to the formation of a mature vasculature by promoting pericyte recruitment along endothelial cells. Here we show that MMP-9 is predominantly expressed by bone marrow-derived CD45-positive leukocytes. Using a series of bone marrow transplantation experiments in MMP-9(+/+) and MMP-9(-/-) mice xenotransplanted with human neuroblastoma tumors, we show that bone marrow-derived MMP-9 is critical for the recruitment of leukocytes from bone marrow into the tumor stroma and for the integration of bone marrow-derived endothelial cells into the tumor vasculature. Expression of MMP-9 by bone marrow-derived cells in the tumor stroma is also critical for the formation of a mature vasculature and coverage of endothelial cells with pericytes. Furthermore, in primary human neuroblastoma tumor specimens of unfavorable histology, we observed a higher level of tumor infiltration with MMP-9 expressing phagocytic cells and a higher degree of coverage of endothelial cells by pericytes when compared with tumor specimens with a favorable histology. Taken together, the data show that in neuroblastoma, MMP-9 plays a critical role in the recruitment of bone marrow-derived cells to the tumor microenvironment where they positively contribute to angiogenesis and tumor progression.

Photodynamic therapy (PDT) clinical results are promising; however, tumor recurrences can occur and, therefore, methods for improving treatment efficacy are needed. PDT elicits direct tumor cell death and microvascular injury as well as expression of angiogenic, inflammatory, and prosurvival molecules. Preclinical studies combining antiangiogenic drugs or cyclooxygenase-2 inhibitors with PDT show improved treatment responsiveness (A. Ferrario et al., Cancer Res 2000;60:4066-9; A. Ferrario et al., Cancer Res 2002;62:3956-61). In the present study, we evaluated the role of Photofrin-mediated PDT in eliciting expression of matrix metalloproteinases (MMPs) and modulators of MMP activity. We also examined the efficacy of a synthetic MMP inhibitor, Prinomastat, to enhance tumoricidal activity after PDT, using a mouse mammary tumor model. Immunoblot analysis of extracts from PDT-treated tumors demonstrated strong expression of MMPs and extracellular MMP inducer along with a concomitant decrease in expression of tissue inhibitor of metalloproteinase-1. Gelatin zymography and enzyme activity assays performed on protein extracts from treated tumors confirmed the induction of both latent and enzymatically active forms of MMP-9. Immunohistochemical analysis indicated that infiltrating inflammatory cells and endothelial cells were primary sources of MMP-9 expression after PDT, whereas negligible expression was observed in tumor cells. Administration of Prinomastat significantly improved PDT-mediated tumor response (P = 0.02) without affecting normal skin photosensitization. Our results indicate that PDT induces MMPs and that the adjunctive use of an MMP inhibitor can improve PDT tumor responsiveness.