Akt-activated endothelium constitutes the niche for residual disease and resistance to bevacizumab in ovarian cancer

Ovarian cancer is the second leading cause of cancer-related death in women worldwide. Despite optimal cytoreduction and adequate adjuvant therapies, initial tumor response is often followed by relapse suggesting the existence of a tumor niche. Targeted therapies have been evaluated in ovarian cancer to overcome resistant disease. Among them, antiangiogenic therapies inhibit new blood vessel growth, induce endothelial cell apoptosis, and block the incorporation of hematopoietic and endothelial progenitor cells into new blood vessels. Despite in vitro and in vivo successes, antivascular therapy with bevacizumab targeting VEGF-A has limited efficacy in ovarian cancer. The precise molecular mechanisms underlying clinical resistance to anti-VEGF therapies are not yet well understood. Among them, tumor and stromal heterogeneity might determine the treatment outcomes. The present study investigates whether abnormalities in the tumor endothelium may contribute to treatment resistance to bevacizumab and promote a residual microscopic disease. Here, we showed that ovarian cancer cells activate Akt phosphorylation in endothelial cells inducing resistance to bevacizumab leading to an autocrine loop based on FGF2 secretion. Altogether, our results point out the role of an activated endothelium in the resistance to bevacizumab and in the constitution of a niche for a residual disease.

Role of mesenchymal cells in the natural history of ovarian cancer: a review

Background

Ovarian cancer is the deadliest gynaecologic malignancy. Despite progresses in chemotherapy and ultra-radical surgeries, this locally metastatic disease presents a high rate of local recurrence advocating for the role of a peritoneal niche. For several years, it was believed that tumor initiation, progression and metastasis were merely due to the changes in the neoplastic cell population and the adjacent non-neoplastic tissues were regarded as bystanders. The importance of the tumor microenvironment and its cellular component emerged from studies on the histopathological sequence of changes at the interface between putative tumor cells and the surrounding non-neoplastic tissues during carcinogenesis.

Method

In this review we aimed to describe the pro-tumoral crosstalk between ovarian cancer and mesenchymal stem cells. A PubMed search was performed for articles published pertaining to mesenchymal stem cells and specific to ovarian cancer.

Results

Mesenchymal stem cells participate to an elaborate crosstalk through direct and paracrine interaction with ovarian cancer cells. They play a role at different stages of the disease: survival and peritoneal infiltration at early stage, proliferation in distant sites, chemoresistance and recurrence at later stage.

Conclusion

The dialogue between ovarian and mesenchymal stem cells induces the constitution of a pro-tumoral mesencrine niche. Understanding the dynamics of such interaction in a clinical setting might propose new therapeutic strategies.

Abstract 2998: Akt-activated endothelium constitute the niche for residual disease and resistance to bevacizumab in ovarian cancer

Ovarian cancer is the second leading cause of cancer-related death in women worldwide. Despite optimal cytoreduction and adequate adjuvant therapies, initial tumor response is often followed by relapse suggesting the existence of a tumor niche. Targeted therapies have been evaluated in ovarian cancer to overcome resistant disease. Among them anti-angiogenic therapies inhibit new blood vessel growth, induce endothelial cell apoptosis, and block the incorporation of haematopoietic and endothelial progenitor cells into new blood vessels. Despite in vitro and in vivo successes antivascular therapy with bevacizumab targeting VEGF has limited efficacy in ovarian cancer. The precise molecular mechanisms underlying clinical resistance to anti-VEGF therapies are not yet well understood. Among them tumor and stromal heterogeneity might determine the treatment outcomes. The present study investigates whether abnormalities in the tumor endothelium may contribute to treatment resistance to bevacizumab and promote a residual microscopic disease. Here we showed that ovarian cancer cells (OCC) activate akt phosphorylation in endothelial cells inducing resistance to bevacizumab leading to an autocrine loop based on FGF2 secretion. Altogether our results point out the role of an activated endothelium in the resistance to bevacizumab and in the constitution of a niche for a residual disease.

Citation Format: Bella Samia Guerrouahen, Jennifer Pasquier, Nadine Abou Kaoud, Marie-Claude Beauchamp, Mahtab Maleki, Pegah Ghiabi, Raphael Lis, Ahmed Saleh, Walter H. Gotlieb, Shahin Rafii, Arash Rafii. Akt-activated endothelium constitute the niche for residual disease and resistance to bevacizumab in ovarian cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2998. doi:10.1158/1538-7445.AM2014-2998

[Feasibility and fiability of laparoscopic surgery in the uterine cancers in normal-weight patients]

OBJECTIVES

Evaluate the fiability and feasibility of laparoscopic surgery for the management of uterine cancers [endometrial cancer (EC) and early-stage cervical cancer (ESCC)] with patients who have a BMI ≤ 30 kg/m(2), within the setting of a gynaecological oncology department.

PATIENTS AND METHODS

This retrospective, monocentric and descriptive study was carried out between January 2003 and May 2011 at the Institute Claudius-Regaud, a centre for cancer diagnosis, treatment and research. A policy promoting laparoscopy as a first choice treatment has been established at the institute since 2003.

RESULTS

Two hundred and three patients were included. Eighty-five patients were early-stage cervical cancer patients and 118 patients were endometrial cancer patients. The study shows a high fiability rate for laparoscopy in non-obese patients, with a 98.8% rate for EC patients and a 98.8% rate for ESCC patients. The feasibility rates were 80.1% and 96.6%, respectively. The incidence of laparoconversion was reported at 1.2% and 3.1% for ESCC and EC patients, respectively, while the incidence of peroperative complications was 5.9% and 7.4%. The incidence of postoperative complications rank ≥ 3 according to "Memorial secondary events grading system" was 3 (3.5%) for CCUP and 3 (2.5%) for CE.

DISCUSSION AND CONCLUSION

The results of this study show high fiability and feasibility levels for the laparoscopic treatment of uterine cancers in non-obese patients. There is no need to implement the more expensive robotic-assisted surgery in this group of patients. Mastering advanced laparoscopic surgery remains a mainstay in gynaecologic oncology.

[Oncofertility program at the Montpellier university hospital 2 years after]

OBJECTIVE

Female fertility preservation in the context of cancer management is crucial for patient's health care. The aim of this study was to evaluate the oncofertility practice at our university hospital of Montpellier since 2011.

PATIENTS AND METHODS

The evaluation of management of young patients referred to Montpellier University Hospital from September 2011 to September 2013 for oncofertility counselling before cancer treatment.

RESULTS

Seventy-one patients were referred to a specialized oncofertility center. Forty-two patients (59.1%) were included in the oncofertility program. Twenty-two patients (31%) were proposed for oocyte vitrification after COS protocol, eight patients (11.3%) for ovarian tissue cryoconservation, seven patients (9.9%) for GnRH injections, three patients (4.2%) ovarian transposition and two patients (2.8%) for embryo cryopreservation. Among the 42 indications of fertility preservation, only 18 will have finally taken place.

CONCLUSION

Oncofertility counselling for young patients should now be part of the cancer management. It involves multidisciplinary teams. Further information of both oncologists and patients is needed to improve this new approach in the field of cancer treatments.

AAV-mediated persistent bevacizumab therapy suppresses tumor growth of ovarian cancer

RATIONALE

Anti-angiogenesis therapies such as bevacizumab, the monoclonal antibody to vascular endothelial growth factor (VEGF), have been used against ovarian cancer, but transient and low peritoneal drug levels are likely a factor in treatment failure. We hypothesized that a single administration of adeno-associated virus (AAV)-mediated intraperitoneal expression of bevacizumab would direct persistent expression and suppress growth and metastasis of ovarian cancer.

METHODS

AAVrh.10BevMab, a rhesus serotype 10 adeno-associated viral vector coding for bevacizumab, was evaluated for the capacity of a single intraperitoneal administration to persistently suppress peritoneal tumor growth in an intraperitoneal model of ovarian carcinomatosis with human ovarian cancer cells in nude immunodeficient mice.

RESULTS

The data demonstrates that AAVrh10.BevMab mediates persistent and high levels of bevacizumab in the peritoneal cavity following a single intraperitoneal administration in mice. In AAVrh10.BevMab treated A2780 human ovarian cancer-bearing mice, tumor growth was significantly suppressed (p<0.05) and the area of blood vessels in the tumor was decreased (p<0.04). Survival of mice with A2780 xenografts or SK-OV3 xenografts was greatly prolonged in the presence of AAVrh10.BevMab (p<0.001). Administration of AAVrh10.BevMab 4days after A2780-luciferase cell implantation reduced tumor growth (p<0.01) and increased mouse survival (p<0.0001). Combination of AAVrh10.BevMab with cytotoxic reagents paclitaxel or topotecan proved to be more effective in increasing survival than treatment with cytotoxic reagent alone.

CONCLUSION

A single administration of AAVrh10.BevMab provides sustained and high local expression of bevacizumab in the peritoneal cavity, and significantly suppresses peritoneal carcinomatosis and increases survival in an ovarian cancer murine model.

[Circulating tumor cells: cornerstone of personalized medicine]

Cancer treatment has evolved toward personalized medicine. It is mandatory for clinicians to ascertain tumor biological features in order to optimize patients' treatment. Identification and characterization of circulating tumor cells demonstrated a prognostic value in many solid tumors. Here, we describe the main technologies for identification and characterization of circulating tumor cells and their clinical application in gynecologic and breast cancers.

Where cancer genomics should go next: a clinician's perspective

Large-scale, genomic studies of specific tumors such as The Cancer Genome Atlas have provided a better understanding of the alterations of pathways involved in the development of solid tumors including glioblastoma, breast cancer, ovarian and endometrial cancers, colon cancer and lung squamous cell carcinoma. This tremendous effort of the scientific community has confirmed the view that cancer actually represents a wide variety of diseases originating from different organs. These studies showed that TP53 and PI3KCA are the two most mutated genes in all types of cancers and that 30-70% of all solid tumors harbor potentially 'actionable' mutations that can be exploited for patient stratification or treatment optimization. Translation of this huge oncogenomic data set to clinical application in personalized medicine programs is now the main challenge for the future. The gap between our basic knowledge and clinical application is still wide. Closing the gap will require translational personalized trials, which may initiate a radical change in our routine clinical practice in oncology.

Angiocrine factors deployed by tumor vascular niche induce B cell lymphoma invasiveness and chemoresistance

Tumor endothelial cells (ECs) promote cancer progression in ways beyond their role as conduits supporting metabolism. However, it is unknown how vascular niche-derived paracrine factors, defined as angiocrine factors, provoke tumor aggressiveness. Here, we show that FGF4 produced by B cell lymphoma cells (LCs) through activating FGFR1 upregulates the Notch ligand Jagged1 (Jag1) on neighboring ECs. In turn, upregulation of Jag1 on ECs reciprocally induces Notch2-Hey1 in LCs. This crosstalk enforces aggressive CD44(+)IGF1R(+)CSF1R(+) LC phenotypes, including extranodal invasion and chemoresistance. Inducible EC-selective deletion of Fgfr1 or Jag1 in the Eμ-Myc lymphoma model or impairing Notch2 signaling in mouse and human LCs diminished lymphoma aggressiveness and prolonged mouse survival. Thus, targeting the angiocrine FGF4-FGFR1/Jag1-Notch2 loop inhibits LC aggressiveness and enhances chemosensitivity.

Mesenchymal cell interaction with ovarian cancer cells induces a background dependent pro-metastatic transcriptomic profile

BACKGROUND

The cross talk between the stroma and cancer cells plays a major role in phenotypic modulation. During peritoneal carcinomatosis ovarian cancer cells interact with mesenchymal stem cells (MSC) resulting in increased metastatic ability. Understanding the transcriptomic changes underlying the phenotypic modulation will allow identification of key genes to target. However in the context of personalized medicine we must consider inter and intra tumoral heterogeneity. In this study we used a pathway-based approach to illustrate the role of cell line background in transcriptomic modification during a cross talk with MSC.

METHODS

We used two ovarian cancer cell lines as a surrogate for different ovarian cancer subtypes: OVCAR3 for an epithelial and SKOV3 for a mesenchymal subtype. We co-cultured them with MSCs. Genome wide gene expression was determined after cell sorting. Ingenuity pathway analysis was used to decipher the cell specific transcriptomic changes related to different pro-metastatic traits (Adherence, migration, invasion, proliferation and chemoresistance).

RESULTS

We demonstrate that co-culture of ovarian cancer cells in direct cellular contact with MSCs induces broad transcriptomic changes related to enhance metastatic ability. Genes related to cellular adhesion, invasion, migration, proliferation and chemoresistance were enriched under these experimental conditions. Network analysis of differentially expressed genes clearly shows a cell type specific pattern.

CONCLUSION

The contact with the mesenchymal niche increase metastatic initiation and expansion through cancer cells' transcriptome modification dependent of the cellular subtype. Personalized medicine strategy might benefit from network analysis revealing the subtype specific nodes to target to disrupt acquired pro-metastatic profile.

Microparticles mediated cross-talk between tumoral and endothelial cells promote the constitution of a pro-metastatic vascular niche through Arf6 up regulation

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.

Microenvironment mesenchymal cells protect ovarian cancer cell lines from apoptosis by inhibiting XIAP inactivation

Epithelial ovarian carcinoma is characterized by high frequency of recurrence (70% of patients) and carboplatin resistance acquisition. Carcinoma-associated mesenchymal stem cells (CA-MSC) have been shown to induce ovarian cancer chemoresistance through trogocytosis. Here we examined CA-MSC properties to protect ovarian cancer cells from carboplatin-induced apoptosis. Apoptosis was determined by Propidium Iodide and Annexin-V-FITC labelling and poly-ADP-ribose polymerase cleavage analysis. We showed a significant increase of inhibitory concentration 50 and a 30% decrease of carboplatin-induced apoptosis in ovarian cancer cells incubated in the presence of CA-MSC-conditioned medium (CM). A molecular analysis of apoptosis signalling pathway in response to carboplatin revealed that the presence of CA-MSC CM induced a 30% decrease of effector caspases-3 and -7 activation and proteolysis activity. CA-MSC secretions promoted Akt and X-linked inhibitor of apoptosis protein (XIAP; caspase inhibitor from inhibitor of apoptosis protein (IAP) family) phosphorylation. XIAP depletion by siRNA strategy permitted to restore apoptosis in ovarian cancer cells stimulated by CA-MSC CM. The factors secreted by CA-MSC are able to confer chemoresistance to carboplatin in ovarian cancer cells through the inhibition of effector caspases activation and apoptosis blockade. Activation of the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway and the phosphorylation of its downstream target XIAP underlined the implication of this signalling pathway in ovarian cancer chemoresistance. This study reveals the potentialities of targeting XIAP in ovarian cancer therapy.

Abstract B69: Preferential transfer of mitochondria from endothelial to cancer cells through tunneling nanotubes modulates chemoresistance

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.

Citation Format: Jennifer Pasquier, Bella s. Guerrouahen, Hamda Al. Thawadi, Nadine Abu Kaoud, Mahtab Maleki, Frank Le Foll, Arash Rafii. Preferential transfer of mitochondria from endothelial to cancer cells through tunneling nanotubes modulates chemoresistance. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B69.

Abstract B70: Akt-activated endothelium constitute a niche for residual disease and resistance to bevacizumab in ovarian cancer

Background. Ovarian cancer is the second leading cause of cancer-related death in women worldwide. Despite optimal cytoreduction and adequate adjuvant therapy, initial tumor response is often followed by relapse. Targeted therapies have been evaluated in ovarian cancer to overcome resistant disease. Among them anti-angiogenic therapies inhibit new blood vessel growth, induce endothelial cell apoptosis, and block the incorporation of haematopoietic and endothelial progenitor cells into new blood vessels. Despite in-vitro and in vivo successes anti-vascular therapy with bevacizumab targeting VEGF has limited efficacy in ovarian cancer. Anti-angiogenic treatment increases hypoxia, and might lead to tumor rebound and drug resistance. The precise molecular mechanisms underlying clinical resistance to anti-VEGF therapies are not well understood.

Hypothesis. We hypothesized that abnormalities in the tumor endothelium may contribute to treatment resistance and produce and promote a residual microscopic disease and resistance to bevacizumab.

Methods. We showed that Akt pathway is activated in vitro and in vivo in ovarian cancer endothelium. We used Akt-activated endothelial cells (EC) that replicate tumor endothelium biology, and their control, HUVEC to investigate the anti-angiogenic activity of bevacizumab by angiogenesis and migration assays. We conducted XTT assay to examine the effect of bevacizumab on proliferation of VEGF producing human ovarian cancer cell lines. Expression of FGF-2, phospho-AKT was assessed by western blotting and flow cytometry. Finally, using a feeder-free matrigel and spheroid models of ovarian cancer we examined the effect of bevacizumab on residual disease.

Results. We demonstrated that ovarian cancer cells (OCC) activate the endothelium, which displays resistance to bevacizumab. Bevacizumab had no effect on the proliferation of Akt-activated EC, but significantly inhibited angiogenesis and delayed wound healing in HUVEC. We showed the existence of an autocrine loop based on FGF-2 secretion. We demonstrate the role of Akt-activated EC in supporting expansion and self-renewal of OCC in a residual disease context.

Conclusion. Our data point out the role of an activated endothelium in the constitution of the residual disease and resistance to bevacizumab.

Citation Format: Bella S. Guerrouahen, Jennifer Pasquier, Nadine Abu Kaoud, Marie-Claude Beauchamp, Pegah Ghiabi, Mahtab Maleki, Raphael Lis, Ahmed Saleh, Walter H. Gotlieb, Shahin Rafii, Arash Rafii. Akt-activated endothelium constitute a niche for residual disease and resistance to bevacizumab in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B70.

Abstract A74: Microparticles mediate cross-talk between tumoral and endothelial cells and promote the constitution of an angiocrine pro-metastatic niche through Arf6 up regulation

During the past few years, evidences in the literature point out the crucial role of the microenvironment in tumor growth, resistance to therapy and occurrence of metastatic phenotype. Tumor vessels have been considered for a long time as passive conducts for nutriments but more recently several studies have also demonstrated secretion of pro-tumoral factors by endothelial cells. It seems therefore mandatory to clearly identify the mechanisms mediating cross-talk between tumor cells and endothelial cells.

Here, we hypothetize that tumor cell and endothelium secrete bio-active microparticles (MPs) that are actively uptaken by the other cell type and that are participating to a functional cross-talk. We characterized the cancer cells MPs, using 2 cells lines from breast cancer (MCF7, MDA-MB231) and 2 from ovarian cancer (SKOV3, OVCAR3) and the endothelium secreted MPs using E4orf1-activated endothelium.

Our data show that MPs from mesenchymal-like metastatic cell lines (MDA-MB231 and SKOV3) were able to promote an angiocrine switch of endothelial cells (activation of akt signaling) compared to MPs from epithelial-like cell lines (OVCAR3 and MCF7). The angiocrine switch increased Arf6 expression and functionalized an MP dependent vascular niche enhancing tumor cells pro-metastatic proprieties. We also show that angiocrine endothelial MPs enhanced tumor cells pro-metastatic proprieties and cancer stemness.

All together we demonstrated that cancer cell derived MPs induced or sustain both an angiogenic but also an angiocrine switch of the endothelium. This has great implication in terms of tumor biology as indeed while the emphasis has mainly been on the angiogenic properties, the angiocrine pro-tumoral effect might be the cause for therapeutic resistance as well as residual and recurrent disease.

Citation Format: Jennifer Pasquier, Hamda Al. Thawadi, Nadine Abu Kaoud, Pegah Ghiabi, Mahtab Maleki, Bella S. Guerrouahen, Arash Rafii. Microparticles mediate cross-talk between tumoral and endothelial cells and promote the constitution of an angiocrine pro-metastatic niche through Arf6 up regulation. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A74.

Endothelial cells provide a niche for placental hematopoietic stem/progenitor cell expansion through broad transcriptomic modification

Umbilical cord blood (UCB) is an attractive source of hematopoietic stem cells (HSCs). However, the number of HSCs in UCB is limited, and attempts to amplify them in vitro remain inefficient. Several publications have documented amplification of hematopoietic stem/progenitor cells (HSPCs) on endothelial or mesenchymal cells, but the lack of homogeneity in culture conditions and HSC definition impairs direct comparison of these results. We investigated the ability of different feeder layers, mesenchymal progenitors (MPs) and endothelial cells (ECs), to amplify hematopoietic stem/progenitor cells. Placental derived HSPCs (defined as Lin(-)CD45(-/dim)CD34(+)CD38(-)CD90(+)) were maintained on confluent feeder layers and the number of cells and their marker expression were monitored over 21 days. Although both types of feeder layers supported hematopoietic expansion, only endothelial cells triggered amplification of Lin(-)CD45(-/dim)CD34(+)CD38(-)CD90(+) cells, which peaked at 14 days. The amplified cells differentiated into all cell lineages, as attested by in vitro colony-forming assays, and were capable of engraftment and multi-lineage differentiation in sub-lethally irradiated mice. Mesenchymal progenitors promoted amplification of CD38(+) cells, previously defined as precursors with more limited differentiation potential. A competitive assay demonstrated that hematopoietic stem/progenitor cells had a preference for interacting with endothelial cells in vitro. Cytokine and transcriptomic analysis of both feeder cell types identified differences in gene expression that correlated with propensity of ECs and MPs to support hematopoietic cell amplification and differentiation respectively. Finally, we used RNA sequencing of endothelial cells and HSPCs to uncover relevant networks illustrating the complex interaction between endothelial cells and HSPCs leading to stem/progenitor cell expansion.

Molecular signatures of tissue-specific microvascular endothelial cell heterogeneity in organ maintenance and regeneration

Microvascular endothelial cells (ECs) within different tissues are endowed with distinct but as yet unrecognized structural, phenotypic, and functional attributes. We devised EC purification, cultivation, profiling, and transplantation models that establish tissue-specific molecular libraries of ECs devoid of lymphatic ECs or parenchymal cells. These libraries identify attributes that confer ECs with their organotypic features. We show that clusters of transcription factors, angiocrine growth factors, adhesion molecules, and chemokines are expressed in unique combinations by ECs of each organ. Furthermore, ECs respond distinctly in tissue regeneration models, hepatectomy, and myeloablation. To test the data set, we developed a transplantation model that employs generic ECs differentiated from embryonic stem cells. Transplanted generic ECs engraft into regenerating tissues and acquire features of organotypic ECs. Collectively, we demonstrate the utility of informational databases of ECs toward uncovering the extravascular and intrinsic signals that define EC heterogeneity. These factors could be exploited therapeutically to engineer tissue-specific ECs for regeneration.

Adaptation of a commonly used, chemically defined medium for human embryonic stem cells to stable isotope labeling with amino acids in cell culture

Metabolic labeling with stable isotopes is a prominent technique for comparative quantitative proteomics, and stable isotope labeling with amino acids in cell culture (SILAC) is the most commonly used approach. SILAC is, however, traditionally limited to simple tissue culture regimens and only rarely employed in the context of complex culturing conditions as those required for human embryonic stem cells (hESCs). Classic hESC culture is based on the use of mouse embryonic fibroblasts (MEFs) as a feeder layer, and as a result, possible xenogeneic contamination, contribution of unlabeled amino acids by the feeders, interlaboratory variability of MEF preparation, and the overall complexity of the culture system are all of concern in conjunction with SILAC. We demonstrate a feeder-free SILAC culture system based on a customized version of a commonly used, chemically defined hESC medium developed by Ludwig et al. and commercially available as mTeSR1 [mTeSR1 is a trade mark of WiCell (Madison, WI) licensed to STEMCELL Technologies (Vancouver, Canada)]. This medium, together with adjustments to the culturing protocol, facilitates reproducible labeling that is easily scalable to the protein amounts required by proteomic work flows. It greatly enhances the usability of quantitative proteomics as a tool for the study of mechanisms underlying hESCs differentiation and self-renewal. Associated data have been deposited to the ProteomeXchange with the identifier PXD000151.

Preferential transfer of mitochondria from endothelial to cancer cells through tunneling nanotubes modulates chemoresistance

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.

Mesenchymal stem cells enhance ovarian cancer cell infiltration through IL6 secretion in an amniochorionic membrane based 3D model

BACKGROUND

The early peritoneal invasion of epithelial ovarian cancer (EOC) by tumoral aggregates presents in ascites is a major concern. The role of the microenvironment seems to be important in this process but the lack of adequate models to study cellular interactions between cancer cells and stromal cells does not allow to uncover the molecular pathways involved. Our goal was to study the interactions between ovarian cancer cells (OCC) and mesenchymal stem cells (MSC) using a 3D model.

METHODS

We used millimetric pieces of amniochorionic membrane - referred to as amniotic membrane scaffold (AMS) - to create 3D peritoneal nodules mimicking EOC early invasion. We were able to measure the distribution and the depth of infiltration using confocal microsopy. We extracted MSC from the amniochorionic membrane using the markers CD34-, CD45-, CD73+, CD90+, CD105+ and CD29+ at the Fluorescence Activated Cell Sorting (FACS) analysis. We used transwell and wound healing tests to test OCC migration and invasion in vitro.

RESULTS

Here we show that OCC tumors were located in regions rich in MSC (70%). The tumors infiltrated deeper within AMS in regions rich in MSC (p<0.001). In vitro tests revealed that higher IL6 secretion in a context of MSC-OCC co-culture could enhance migration and invasion of OCC. After IL6 receptor antagonism, OCC infiltration was significantly decreased, mostly in regions rich in MSCs, indicating that recruitment and tridimensional invasion of OCC was dependent of IL6 secretion.

CONCLUSIONS

The use of tridimensional models using AMS could be a useful tool to decipher early molecular events in ovarian cancer metastasis. Cytokine inhibitors interrupting the cross-talk between OCCs and MSCs such as IL6 should be investigated as a new therapeutic approach in ovarian cancer.

Human embryonic stem cell derived mesenchymal progenitors express cardiac markers but do not form contractile cardiomyocytes

Mesenchymal progenitors or stromal cells have shown promise as a therapeutic strategy for a range of diseases including heart failure. In this context, we explored the growth and differentiation potential of mesenchymal progenitors (MPs) derived in vitro from human embryonic stem cells (hESCs). Similar to MPs isolated from bone marrow, hESC derived MPs (hESC-MPs) efficiently differentiated into archetypical mesenchymal derivatives such as chondrocytes and adipocytes. Upon treatment with 5-Azacytidine or TGF-β1, hESC-MPs modified their morphology and up-regulated expression of key cardiac transcription factors such as NKX2-5, MEF2C, HAND2 and MYOCD. Nevertheless, NKX2-5⁺ hESC-MP derivatives did not form contractile cardiomyocytes, raising questions concerning the suitability of these cells as a platform for cardiomyocyte replacement therapy. Gene profiling experiments revealed that, although hESC-MP derived cells expressed a suite of cardiac related genes, they lacked the complete repertoire of genes associated with bona fide cardiomyocytes. Our results suggest that whilst agents such as TGF-β1 and 5-Azacytidine can induce expression of cardiac related genes, but treated cells retain a mesenchymal like phenotype.

High-prevalence and broad spectrum of Cell Adhesion and Extracellular Matrix gene pathway mutations in epithelial ovarian cancer

Background

Ovarian cancer is the most deadly gynecological cancer because of late diagnosis, frequently with diffuse peritoneal metastases. Recent findings have shown that serous epithelial ovarian cancer has a narrow mutational spectrum with TP53 being the most frequently targeted when single genes are considered. It is, however, important to understand which pathways as a whole may be targeted for mutation.

Findings

Previously published mutational data provided by the cancer genome atlas networks findings on ovarian cancer was searched for statistically significant enrichment of genes in pathways. These pathways were then searched in all patients to identify the spectrum of mutations. Statistical significance was further shown through in-silico permutations of exome sequences using empirically observed mutation rates. We detected mutations in the cell adhesion pathway genes in more than 89% of serous epithelial ovarian cancer patients. This level of near universal mutational targeting of the cell adhesion pathway, including the extracellular matrix pathway, is previously unreported in epithelial ovarian cancer.

Conclusions

Taken together with previous studies on the role of cell adhesion and extracellular matrix gene expression in ovarian cancer and metastasis, our results identify pathways for which the mutational prevalence has previously been overlooked using single gene approaches. Analysis of mutations at the pathway level will be critical in studying heterogeneous diseases such as ovarian cancer.

Multi-center evaluation of post-operative morbidity and mortality after optimal cytoreductive surgery for advanced ovarian cancer

PURPOSE

While optimal cytoreduction is the standard of care for advanced ovarian cancer, the related post-operative morbidity has not been clearly documented outside pioneering centers. Indeed most of the studies are monocentric with inclusions over several years inducing heterogeneity in techniques and goals of surgery. We assessed the morbidity of optimal cytoreduction surgery for advanced ovarian cancer within a short inclusion period in 6 referral centers dedicated to achieve complete cytoreduction.

PATIENTS AND METHODS

The 30 last optimal debulking surgeries of 6 cancer centers were included. Inclusion criteria included: stage IIIc- IV ovarian cancer and optimal surgery performed at the site of inclusion. All post-operative complications within 30 days of surgery were recorded and graded using the Memorial secondary events grading system. Student-t, Chi2 and non-parametric statistical tests were performed.

RESULTS

180 patients were included. There was no demographic differences between the centers. 63 patients underwent surgery including intestinal resections (58 recto-sigmoid resection), 24 diaphragmatic resections, 17 splenectomies. 61 patients presented complications; One patient died post-operatively. Major (grade 3-5) complications requiring subsequent surgeries occurred in 21 patients (11.5%). 76% of patients with a major complication had undergone an ultraradical surgery (P = 0.004).

CONCLUSION

While ultraradical surgery may result in complete resection of peritoneal disease in advanced ovarian cancer, the associated complication rate is not negligible. Patients should be carefully evaluated and the timing of their surgery optimized in order to avoid major complications.

Gene expression analysis of matched ovarian primary tumors and peritoneal metastasis

Background

Ovarian cancer is the most deadly gynecological cancer due to late diagnosis at advanced stage with major peritoneal involvement. To date most research has focused on primary tumor. However the prognosis is directly related to residual disease at the end of the treatment. Therefore it is mandatory to focus and study the biology of meatastatic disease that is most frequently localized to the peritoneal caivty in ovarian cancer.

Methods

We used high-density gene expression arrays to investigate gene expression changes between matched primary and metastatic (peritoneal) lesions.

Results

Here we show that gene expression profiles in peritoneal metastasis are significantly different than their matched primary tumor and these changes are affected by underlying copy number variation differences among other causes. We show that differentially expressed genes are enriched in specific pathways including JAK/STAT pathway, cytokine signaling and other immune related pathways. We show that underlying copy number variations significantly affect gene expression. Indeed patients with important differences in copy number variation displayed greater gene expression differences between their primary and matched metastatic lesions.

Conclusions

Our analysis shows a very specific targeting at both the genomic and transcriptomic level to upregulate certain pathways in the peritoneal metastasis of ovarian cancer. Moreover, while primary tumors use certain pathways we identify distinct differences with metastatic lesions. The variation between primary and metastatic lesions should be considered in personalized treatment of ovarian cancer.