Tumor associated mesenchymal stem cells protects ovarian cancer cells from hyperthermia through CXCL12.

Hyperthermic intraperitoneal chemotherapy (HIPEC) has shown promise in treatment of ovarian carcinosis. Despite its efficiency for the treatment of peritoneal carcinosis from digestive tract neoplasia, it has failed to demonstrate significant benefit in ovarian cancers. It is therefore essential to understand the mechanism underlying resistance to HIPEC in ovarian cancers. Mesenchymal stem cells (MSC) play an important role in the development of ovarian cancer metastasis and resistance to treatments. A recent study suggests that MSCs may be cytotoxic for cancer cells upon heat shock. In contrast, we describe the protective role of MSC against hyperthermia. Using cytokine arrays we determined that the tumor associated MSC (TAMC) secrete pro-tumoral cytokines. We studied the effect of hyperthermia in co-culture setting of TAMC or BM-MCS associated with ovarian cancer cell lines (SKOV3 and CaOV3) with polyvariate flow cytometry. We demonstrate that hyperthermia does not challenge survival of TAMC or bone marrow derived MSC (BM-MSC). Both TAMC and BM-MSC displayed strong protective effect inducing thermotolerance in ovarian cancer cells (OCC). Transwell experiments demonstrated the role of secreted factors. We showed that CXCL12 was inducing thermotolerance and that inhibition of CXCL12/CXCR4 interaction restored cytotoxicity of hyperthermia in co-culture experiments. Contrary to the previous published study we demonstrated that TAMC and BM-MSC co-cultured with OCC induced thermotolerance in a CXCL12 dependant manner. Targeting the interaction between stromal and cancer cells through CXCL12 inhibition might restore hyperthermia sensitivity in ovarian cancers, and thus improve HIPEC efficiency.

Hospicells derived from ovarian cancer stroma inhibit T-cell immune responses.

With metastatic disease at diagnosis for 70% of patients, ovarian cancer represents the most lethal gynecological malignancy. Ovarian carcinomas are aggressive malignancies that can evade immune surveillance and frequently develop into metastases. The tumor microenvironment is decisive for preventing immune attack but, in the case of ovarian carcinoma, the mechanisms are unclear. We recently isolated a novel type of stromal cell from the ascitis of patients with ovarian carcinoma that interacts with epithelial ovarian cancers conferring them chemoresistance. These cells, called Hospicells, have the cell surface markers CD9, CD10, CD29, CD146 and CD166. Here, we investigated whether Hospicells also have immunomodulatory functions that might interfere with immunity to cancer. We report that Hospicells inhibit the proliferation of human CD4(+), CD8(+) and Vgamma9Vdelta2 T cells in vitro and the production of cytokines by these immune cells. The immunosuppression of CD4(+) T cells is independent of direct contact with the Hospicells and is mainly due to nitric oxide produced by the inducible nitric oxide synthase and to products of the tryptophan degradation by indoleamine 2,3-dioxygenase. We proposed that Hospicells in the microenvironment of the tumor mediate immunosuppression of T cells and thus allow ovarian cancers to evade immune surveillance. Targeting of Hospicells could be an alternative to strong chemotherapy through the recovery of immune responses against tumor cells.

Anti-endothelial cell antibodies determination by cyto-ELISA: a comparative study between three cell types used as substrates.

Cyto-ELISA has been widely used to investigate anti-endothelial cell antibodies (AECAs); however, because various types of endothelial cells have been used, the results among studies differ. The aim of our study was to analyze and compare the results when determining AECAs in patients with connective tissue disease (CTD). We did so using a cyto-ELISA with different cells as antigenic substrates: two different endothelial cells, one microvascular (HMEC-1) and one from human bone marrow (HBMEC), and one epithelial cell line from breast adenocarcinoma as negative controls (MDA-MB-231). In this trial, we performed a retrospective study in 60 patients with CTD [46 with systemic lupus erythematosus, 8 with Sjögren's syndrome, and 6 with systemic sclerosis] and 32 healthy volunteers. Using cyto-ELISA, the antibody against a cell was considered positive when the optical density (OD) obtained was higher than the mean OD obtained in the control group + 2 standard deviations (upper normal range). Patients were classified into three groups according to the OD obtained with the different cell lines: group 1: patients without any antibody; group 2: patients with specific AECAs; and group 3: patients with nonspecific AECAs. According to this classification, we found that 43.3% of patients with CTD have specific AECAs, and 28.3% have nonspecific antibodies. Our study delineates the heterogeneity of AECAs in patients with CTD. The use of HBMEC in cyto-ELISA may increase the sensitivity of the test, and the use of nonendothelial cells as negative controls may improve its specificity.

Oncologic trogocytosis with Hospicells induces the expression of N-cadherin by breast cancer cells.

In breast cancers, the appearance of metastasis is synonymous with poor prognosis. The metastatic process is usually associated with epithelial-mesenchymal transition (EMT) which is often induced by several soluble factors produced either by the tumour cells themselves or by cells constituting the tumour microenvironment. The aim of the present study was to determine whether the mesenchymal properties given by some molecules such as N-cadherin, for instance, could be acquired by cancer cells via the trogocytosis process with cells of the tumour microenvironment. Hospicells are stromal cells which were first isolated from cancer cell aggregates of patients with ovarian cancer. We recently showed that these cells are immunosuppressive for T lymphocyte functions and confer chemoresistance to cancer cells by the transfer of the MDR protein via trogocytosis. In this study, we showed that a mammary cancer cell line (MDA-MB-231) acquires patches of membrane via oncologic trogocytosis with Hospicells. This unidirectional and active process depends on actin polymerization and can be increased via inhibition of the Src family and decreased via inhibition of PI3K. Trogocytosis between Hospicells and MDA-MB-231 does not lead to the direct acquisition of N-cadherin but rather it leads to the production of soluble factor(s) which induce de novo expression of N-cadherin by the cancer cells. The novelty here is that this factor is produced only if cancer cells interact and undergo trogocytosis with Hospicells. This new expression could confer a more invasive phenotype to the cancer cells and thus can explain the correlation of the presence of Hospicells with the number of invaded lymph nodes in patients with mammary adenocarcinoma.

Oncologic trogocytosis of an original stromal cells induces chemoresistance of ovarian tumours.

BACKGROUND: The microenvironment plays a major role in the onset and progression of metastasis. Epithelial ovarian cancer (EOC) tends to metastasize to the peritoneal cavity where interactions within the microenvironment might lead to chemoresistance. Mesothelial cells are important actors of the peritoneal homeostasis; we determined their role in the acquisition of chemoresistance of ovarian tumours. METHODOLOGY/PRINCIPAL FINDINGS: We isolated an original type of stromal cells, referred to as "Hospicells" from ascitis of patients with ovarian carcinosis using limiting dilution. We studied their ability to confer chemoresistance through heterocellular interactions. These stromal cells displayed a new phenotype with positive immunostaining for CD9, CD10, CD29, CD146, CD166 and Multi drug resistance protein. They preferentially interacted with epithelial ovarian cancer cells. This interaction induced chemoresistance to platin and taxans with the implication of multi-drug resistance proteins. This contact enabled EOC cells to capture patches of the Hospicells membrane through oncologic trogocytosis, therefore acquiring their functional P-gp proteins and thus developing chemoresistance. Presence of Hospicells on ovarian cancer tissue micro-array from patients with neo-adjuvant chemotherapy was also significantly associated to chemoresistance. CONCLUSIONS/SIGNIFICANCE: This is the first report of trogocytosis occurring between a cancer cell and an original type of stromal cell. This interaction induced autonomous acquisition of chemoresistance. The presence of stromal cells within patient's tumour might be predictive of chemoresistance. The specific interaction between cancer cells and stromal cells might be targeted during chemotherapy.