Our vision of cancer has changed during the past decades. Indeed tumors are now perceived as complex entities where tumoral and stromal components interact closely. Among the different elements of tumor stroma the cellular component play a primordial role. Bone Marrow derived mesenchymal cells (MSCs) are attracted to tumor sites and support tumor growth. Endothelial cells (ECs) play a major role in angiogenesis. While the literature documents many aspects of the cross talk between stromal and cancer cells, the role of direct hetero-cellular contact is not clearly established. Recently, Tunneling nanotubes (TnTs) have been shown to support cell-to-cell transfers of plasma membrane components, cytosolic molecules and organelles within cell lines. Herein, we have investigated the formation of heterocellular TnTs between stromal (MSCs and ECs) and cancer cells. We demonstrate that TnTs occur between different cancer cells, stromal cells and cancer-stromal cell lines. We showed that TnTs-like structure occurred in 3D anchorage independent spheroids and also in tumor explant cultures. In our culture condition, TnTs formation occurred after large membrane adhesion. We showed that intercellular transfers of cytoplasmic content occurred similarly between cancer cells and MSCs or ECs, but we highlighted that the exchange of mitochondria occurred preferentially between endothelial cells and cancer cells. We illustrated that the cancer cells acquiring mitochondria displayed chemoresistance. Our results illustrate the perfusion-independent role of the endothelium by showing a direct endothelial to cancer cell mitochondrial exchange associated to phenotypic modulation. This supports another role of the endothelium in the constitution of the metastatic niche.

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.Epithelial ovarian carcinoma (EOC) is the sixth most common malignancy in women and the leading cause of death from gynecological cancer worldwide. 1 EOC has a predisposition to metastatic involvement of the peritoneal cavity. 2,3 Late stage EOC is characterized by widespread peritoneal dissemination, ascitis and a high rate of mortality with an overall survival ranging from 20 to 30% at 5 years. 4 Platinum associated to taxanes chemotherapy, is the standard treatment for ovarian cancers, and has achieved high response rate. The development of drug-resistant cancer cells exhibiting multidrug resistance phenotype is one of the major limitations of the efficacy illustrated in the literature for platinum or taxanes chemotherapy. 4,5 Therefore, new therapeutic modalities are critical to improve overall survival in ovarian cancer. Intra-peritoneal (IP) chemotherapy emerged as one therapeutic option from the natural history of ovarian cancers (e.g., local extension to the peritoneum, chemosensitivity). Indeed it has been demonstrated that IP delivery of certain chemotherapeutic agents leads to increased peritoneal cavity drug exposure. 6 Randomized control trials demonstrated superiority of IP chemotherapy over classical intravenous therapy in patients with optimally debulked Stage III ovarian cancer. 6,7 More recently, hyperthermic ...

Treating metastasis has been challenging due to tumors complexity and heterogeneity. This complexity is partly related to the crosstalk between tumor and its microenvironment. Endothelial cells -the building blocks of tumor vasculature- have been shown to have additional roles in cancer progression than angiogenesis and supplying oxygen and nutrients. Here, we show an alternative role for endothelial cells in supporting breast cancer growth and spreading independent of their vascular functions. Using endothelial cells and breast cancer cell lines MDA-MB231 and MCF-7, we developed co-culture systems to study the influence of tumor endothelium on breast tumor development by both in vitro and in vivo approaches. Our results demonstrated that endothelial cells conferred survival advantage to tumor cells under complete starvation and enriched the CD44HighCD24Low/- stem cell population in tumor cells. Moreover, endothelial cells enhanced the pro-metastatic potential of breast cancer cells. The in vitro and in vivo results concordantly confirmed a role for endothelial Jagged1 to promote breast tumor through notch activation. Here, we propose a role for endothelial cells in enhancing breast cancer progression, stemness, and pro-metastatic traits through a perfusion-independent manner. Our findings may be beneficial in developing novel therapeutic approaches.

The tumor stroma plays an essential role in tumor growth, resistance to therapy and occurrence of metastatic phenotype. Tumor vessels have been considered as passive conducts for nutrients but several studies have demonstrated secretion of pro-tumoral factors by endothelial cells. The failure of anti-angiogenic therapies to meet expectations raised by pre-clinical studies prompt us to better study the cross-talk between endothelial and cancer cells. Here, we hypothesized that tumor cells and the endothelium secrete bio-active microparticles (MPs) participating to a functional cross-talk. We characterized the cancer cells MPs, using breast and ovarian cancer cell lines (MCF7, MDA-MB231, SKOV3, OVCAR3 and a primary cell lines, APOCC). Our data show that MPs from mesenchymal-like cell lines (MDA-MB231, SKOV3 and APOCC) were able to promote an activation of endothelial cells through Akt phosphorylation, compared to MPs from epithelial-like cell lines (OVCAR3 and MCF7). The MPs from mesenchymal-like cells contained increased angiogenic molecules including PDGF, IL8 and angiogenin. The endothelial activation was associated to increased Arf6 expression and MPs secretion. Endothelial activation functionalized an MP dependent pro-tumoral vascular niche promoting cancer cells proliferation, invasiveness, stem cell phenotype and chemoresistance. MPs from cancer and endothelial cells displayed phenotypic heterogeneity, and participated to a functional cross-talk where endothelial activation by cancer MPs resulted in increased secretion of EC-MPs sustaining tumor cells. Such cross-talk may play a role in perfusion independent role of the endothelium.Electronic supplementary materialThe online version of this article (doi:10.1007/s12307-013-0142-2) contains supplementary material, which is available to authorized users.

BackgroundEndothelial cells (ECs) are responsible for creating a tumor vascular niche as well as producing angiocrine factors. ECs demonstrate functional and phenotypic heterogeneity when located under different microenvironments. Here, we describe a tumor-stimulated mesenchymal phenotype in ECs and investigate its impact on tumor growth, stemness, and invasiveness.MethodsXenograft tumor assay in NOD/SCID mice and confocal imaging were conducted to show the acquisition of mesenchymal phenotype in tumor-associated ECs in vivo. Immunocytochemistry, qPCR and flow cytometry techniques showed the appearance of mesenchymal traits in ECs after contact with breast tumor cell lines MDA-MB231 or MCF-7. Cell proliferation, cell migration, and sphere formation assays were applied to display the functional advantages of mesenchymal ECs in tumor growth, invasiveness, and enrichment of tumor initiating cells. qPCR and western blotting were used to investigate the mechanisms underlying EC mesenchymal transition.ResultsOur results showed that co-injection of ECs and tumor cells in NOD/SCID mice significantly enhanced tumor growth in vivo with tumor-associated ECs expressing mesenchymal markers while maintaining their intrinsic endothelial trait. We also showed that a mesenchymal phenotype is possibly detectable in human neoplastic breast biopsies as well as ECs pre-exposed to tumor cells (ECsMes) in vitro. The ECsMes acquired prolonged survival, increased migratory behavior and enhanced angiogenic properties. In return, ECsMes were capable of enhancing tumor survival and invasiveness. The mesenchymal phenotypes in ECsMes were the result of a contact-dependent transient phenomenon and reversed upon removal of the neoplastic contexture. We showed a synergistic role for TGFβ and notch pathways in this phenotypic change, as simultaneous inhibition of notch and TGFβ down-regulated Smad1/5 phosphorylation and Jag1KD tumor cells were unable to initiate the process.ConclusionsOverall, our data proposed a crosstalk mechanism between tumor and microenvironment where tumor-stimulated mesenchymal modulation of ECs enhanced the constitution of a transient mesenchymal/endothelial niche leading to significant increase in tumor proliferation, stemness, and invasiveness. The possible involvement of notch and TGFβ pathways in the initiation of mesenchymal phenotype may propose new stromal targets.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0386-3) contains supplementary material, which is available to authorized users.