Christophe Chantrain

Stromal Matrix Metalloproteinase-9 Regulates the Vascular Architecture in Neuroblastoma by Promoting Pericyte Recruitment

Advanced stages of neuroblastoma show increased expression of matrix metalloproteinases MMP-2 and MMP-9 (Y. Sugiura et al., Cancer Res., 58: 2209–2216, 1998) 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.

The Contribution of Bone Marrow-Derived Cells to the Tumor Vasculature in Neuroblastoma Is Matrix Metalloproteinase-9 Dependent

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.

The Matrix Metalloproteinase Inhibitor Prinomastat Enhances Photodynamic Therapy Responsiveness in a Mouse Tumor Model

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.

Computerized Quantification of Tissue Vascularization Using High-resolution Slide Scanning of Whole Tumor Sections

Assessment of tissue vascularization using immunohistochemical techniques for microvessel detection has been limited by difficulties in generating reproducible quantitative data. The distinction of individual blood vessels and the selection of microscopic fields to be analyzed remain two factors of subjectivity. In this study, we used imaging analysis software and a high-resolution slide scanner for measurement of CD31-immunostained endothelial area (EA) in whole sections of human neuroblastoma xenograft and murine mammary adenocarcinoma tumors. Imaging analysis software provided objective criteria for analysis of sections of different tumors. The use of the criteria on images of entire tumor section acquired with the slide scanner constituted a rapid method to quantify tumor vascularization. Compared with previously described methods, the “hot spot” and the “random fields” methods, EA measurements obtained with our “whole section scanning” method were more reproducible with 8.6% interobserver disagreement for the “whole section scanning” method vs 42.2% and 39.0% interobserver disagreement for the “hot spot” method and the “random fields,” respectively. Microvessel density was also measured with the whole section scanning method and provided additional data on the distribution and the size of the blood vessels. Therefore, this method constitutes a time efficient and reproducible method for quantification of tumor vascularization.

Bone Marrow Microenvironment and Tumor Progression

The bone marrow constitutes an unique microenvironment for cancer cells in three specific aspects. First, the bone marrow actively recruits circulating tumor cells where they find a sanctuary rich in growth factors and cytokines that promote their proliferation and survival. When in the bone marrow, tumor cells profoundly affect the homeostasis of the bone and the balance between osteogenesis and osteolysis. As a consequence, growth and survival factors normally sequestered into the bone matrix are released, further fueling cancer progression. Second, tumor cells actively recruit bone marrow-derived precursor cells into their own microenvironment. When in the tumors, these bone marrow-derived cells contribute to an inflammatory reaction and to the formation of the tumor vasculature. Third, bone marrow-derived cells can home in distant organs, where they form niches that attract circulating tumor cells. Our understanding of the contribution of the bone marrow microenvironment to cancer progression has therefore dramatically improved over the last few years. The importance of this new knowledge cannot be underestimated considering that the vast majority of cancer treatments such as cytotoxic and myeloablative chemotherapy, bone marrow transplantation and radiation therapy inflict a trauma to the bone marrow microenvironment. How such trauma affects the influence that the bone marrow microenvironment exerts on cancer is still poorly understood. In this article, the reciprocal relationship between the bone marrow microenvironment and tumor cells is reviewed, and its potential impact on cancer therapy is discussed.

Therapy-related acute myeloid leukemia in a child with Noonan syndrome and clonal duplication of the germline PTPN11 mutation.

A 4‐year‐old girl with Noonan syndrome (NS) and constitutive PTPN11 mutation presented with stage 4 neuroblastoma and was treated by intensive chemotherapy. During the treatment, cytogenetic analysis revealed the development of a hyperdiploid clone with duplication of the germline PTPN11 mutation in a morphologically normal bone marrow. A few months later, the patient developed acute myelomonoblastic leukemia with an additional clonal deletion of 7q. Although, we cannot conclude whether there is an association between NS and neuroblastoma, this case suggests that duplication of germline PTPN11 mutations, potentially induced by chemotherapy, contributes to leukemogenesis in patients with NS. Pediatr Blood Cancer 2007;48:101–104.

Arteriomesenteric syndrome as a cause of duodenal obstruction in children with cerebral palsy.

Two cases of gastroduodenal outlet obstruction caused by arteriomesenteric compression in children who have cerebral palsy are reported. Clinical symptoms of gastrointestinal obstruction include recurrent postprandial nausea and vomiting, upper abdominal distension, and pain. In such patients, multiple predisposing factors can contribute to the development of arteriomesenteric compression, including marked weight loss, supine position, and severe scoliosis. Upper gastrointestinal x-rays using barium contrast allow diagnostic confirmation. In our experience, this cause of acute gastroduodenal outlet obstruction may usually resolve after conservative treatment using a jejunal feeding tube passed beyond the compression, left lateral positioning, and renutrition.

Neonatal acute myeloid leukemia in an infant whose mother was exposed to diethylstilboestrol in utero.

We report on an acute myeloid leukemia in a neonate whose mother was exposed to diethylstilboestrol in utero. The newborn presented with leukemia cutis, hemorrhagic skin lesions, hyperleucocytosis and disseminated intravascular coagulation. A bone marrow examination confirmed the diagnosis of acute monocytic leukemia with a t(11;19) MLL‐ELL fusion transcript. Chemotherapy was initiated but the child developed a bilateral pulmonary infection that led to fatal respiratory distress. This case shows acute myeloid leukemia and the third pediatric leukemia reported after maternal diethylstilboestrol exposure. Pediatr Blood Cancer 2009;53:220–222.

Multiple neoplasia in a 15-year-old girl with familial adenomatous polyposis.

A 15-year-old girl with adenomatous polyposis coli gene (APC) mutation and brain tumor-polyposis syndrome developed an unusual succession of cervicocephalic tumors (medulloblastoma, meningeal low-grade myxoid tumor, and papillary thyroid carcinoma), at the age of 5, 9, and 15 years, respectively. We discuss the genetic profile of the thyroid tumor in which a large somatic deletion of APC gene was found and the physiopathology of thyroid carcinoma in patients with germline APC mutation. We also point out the uncommon phenotype in this young girl with early multiple neoplasias and the difficulties of management of such familial adenomatous polyposis patients with occurrence of extracolonic cancers that require the use of potential trigger agents as radiotherapy or chemotherapy.

Papillary thyroid carcinoma in a 9-year-old girl with ataxia-telangiectasia.

A 9‐year‐old female with ataxia‐telangiectasia (AT) presenting with papillary thyroid carcinoma and lymph nodes involvement is reported. We discuss this novel association, the general risk of neoplasic complications in these patients, the natural history of thyroid carcinoma in the pediatric population and the potential link between thyroid carcinogenesis and ataxia‐telangiectasia mutated gene (ATM) mutation. We also expose our therapeutic attitude, according to both clinical status and particular genetic background of our patient. Pediatr Blood Cancer 2008;50:1058–1060.