Marc Grégoire

Antitumor virotherapy consists of the use of replication-competent viruses to infect and kill tumor cells preferentially, without damaging healthy cells. Vaccine-attenuated strains of measles virus (MV) are good candidates for this approach. Attenuated MV uses the CD46 molecule as a major entry receptor into cells. This molecule negatively regulates the complement system and is frequently overexpressed by cancer cells to escape lysis by the complement system. MV exhibits oncolytic properties in many cancer types in vitro, and in mouse models. Phase I clinical trials using MV are currently underway. Here, we review the state of this therapeutic approach, with a focus on the effects of MV on the antitumor immune response.

Lung and colorectal cancers are responsible for approximately 2 million deaths each year worldwide. Despite continual improvements, clinical management of these diseases remains challenging and development of novel therapies with increased efficacy is critical to address these major public health issues. Oncolytic viruses have shown promising results against cancers that are resistant to conventional anticancer therapies. Vaccine strains of measles virus (MV) exhibit such natural antitumor properties by preferentially targeting cancer cells. We tested the ability of live-attenuated Schwarz strain of MV to specifically infect tumor cells derived from human lung and colorectal adenocarcinomas and demonstrated that live-attenuated MV exhibits oncolytic properties against these two aggressive neoplasms. We also showed that Schwarz MV was able to prevent uncontrollable growth of large, established lung and colorectal adenocarcinoma xenografts in nude mice. Moreover, MV oncolysis is associated within vivoactivation of caspase-3 in colorectal cancer model, as shown by immunohistochemical staining. Our results provide new arguments for the use of MV as an antitumor therapy against aggressive human malignancies.

Dendritic cells (DCs) are professional antigen-presenting cells involved in the control and initiation of immune responses. in vivo, DCs exposed at the periphery to maturation stimuli migrate to lymph nodes, where they receive secondary signals from CD4+ T helper cells. These DCs become able to initiate CD8+ cytotoxic T lymphocyte (CTL) responses. However, in vitro investigations concerning human monocyte-derived DCs have never focused on their functional properties after such sequential maturation. Here, we studied human DC phenotypes and functions according to this sequential exposure to maturation stimuli. As first signals, we used TNF-alpha/polyI:C mimicking inflammatory and pathogen stimuli and, as second signals, we compared activated CD4+ T helper cells to a combination of CD40-L/IFN-gamma. Our results show that a sequential activation with activated CD4+ T cells dramatically increased the maturation of DCs in terms of their phenotype and cytokine secretion compared to DCs activated with maturation stimuli delivered simultaneously. Furthermore, this sequential maturation led to the induction of CTL with a long-term effector and central memory phenotypes. Thus, sequential delivery of maturation stimuli, which includes CD4(+) T cells, should be considered in the future to improve the induction of long-term CTL memory in DC-based immunotherapy.

(2010). Dendritic cell vaccination as a treatment modality for mesothelioma. Expert Review of Respiratory Medicine: Vol. 4, No. 3, pp. 311-314. doi: 10.1586/ers.10.33

Malignant pleural mesothelioma (MPM) is a rare malignancy of the pleura with a very poor prognosis. Treatments evaluated for malignant mesothelioma, including chemotherapy, radiotherapy and surgery are of limited efficacy. However, the fact that the tumors of some patients with MPM regress spontaneously or respond to immunotherapy suggests that the immune system may respond to MPM under some circumstances. In this respect, animal studies have demonstrated immunoreactivity of MPM to different immunotherapies. In the case of MPM, several clinical studies have demonstrated a correlation between the presence of a lymphocyte infiltrate and a better prognosis and humoral response directed against specific antigens related to tumor. Thus, MPM immunotherapy is undoubtedly a highly promising but also very challenging approach to the treatment of this disease that has slipped through the defense lines of the immune system. This article reviews past and recent developments of the clinical strategies that concern immunotherapy of mesothelioma.

Elevated amounts of soluble mesothelin‐related proteins (SMRP) have already been reported in sera and pleural effusions from mesothelioma patients, providing a useful diagnostic marker for malignant pleural mesothelioma (MPM). However, the origin of SMRP is not yet understood. Production of SMRP could be related to abnormal splicing events leading to synthesis of a secreted protein (release) or to an enzymatic cleavage from membrane‐bound mesothelin (ectodomain shedding). To test these hypotheses, we used a panel of mesothelioma cells established in culture from pleural effusions of MPM patients. Our in vitro results confirmed specific mesothelin expression and SMRP production in supernatants from epithelioid MPM cell lines, thus providing a relevant cellular model to study soluble mesothelin production mechanisms. The expression of mesothelin‐encoding RNA variants was screened by reverse transcription–polymerase chain reaction experiments. Protease involvement in mesothelin cleavage from the cellular surface was investigated by treatment of MPM cells with GM6001, a broad‐spectrum MMP‐ and ADAM‐family inhibitor. GM6001 treatment significantly impaired SMRP production by MPM cell lines, in favor of an enzymatic‐mediated shedding process. In addition, a splice variant transcript of mesothelin (variant 3) was detected in these MPM cell lines, in accordance with the release of a secreted part of the protein. Our results indicate that both mechanisms could be implicated in soluble mesothelin production by epithelioid mesothelioma cells. (Cancer Sci 2008; 99: 590–594)

Malignant pleural mesothelioma (MPM) is a rare malignancy of the pleura with a very poor prognosis. Treatments evaluated for malignant mesothelioma, including chemotherapy, radiotherapy and surgery are of limited efficacy. Given that some patients with MPM bear tumours regressing spontaneously or responding to immunotherapy suggests that the immune system may respond to MPM under some circumstances. Animal studies have also demonstrated immunoreactivity to MPM to different immunotherapies. Clinical trials investigating new trends in the treatment of stage I and II malignant mesothelioma have shown both immunotherapy and systemic chemo-immunotherapy to be efficacious. In addition, recent progresses in early detection techniques also provide hope that patients can be treated efficiently, at an earlier stage and well monitored. Thus, immunotherapy of cancer is undoubtedly a highly promising but also very challenging approach in the treatment of a disease that has slipped through the defence lines of the immune system. This article will review past and recent developments of such a clinical strategy.

Dendritic cells (DC) are powerful antigen‐presenting cells that have drawn many attentions due to the recent development of anti‐cancer vaccines. Clinical grade production of monocyte‐derived DC (Mo‐DC) is extensively studied, and many efforts are made to develop and improve clinical standard operating procedures. Most of the parameters involved, such as the cytokines and maturation agents, have been widely assessed. However, very few are investigated about how culture medium and additional protein components affect DC yield, viability and maturation. Thus, our study aimed to compare the impact of standard culture medium on Mo‐DC differentiation and maturation. Commercially available media for hematopoietic cell culture as well as different protein supplementations, that is foetal calf serum (FCS), autologous plasma (AP), human serum (HS) and human serum albumin (HSA) were tested. Culture yields, cell viability and DC maturation were investigated. Differentiation yields were similar between the conditions used. However, we evidenced significant differences in terms of cytotoxicity and DC maturation (phenotypic and functional). This underscores the importance of defining culture medium composition in clinical standard operating procedures to insure quality control, and also when preparing DC for experimental uses.