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Women diagnosed with high-grade serous ovarian cancers (HGSOC) are still likely to exhibit a bad prognosis, particularly when suffering from HGSOC of the Mesenchymal molecular subtype (50% cases). These tumors show a desmoplastic reaction with accumulation of extracellular matrix proteins and high content of cancer-associated fibroblasts. Using patient-derived xenograft mouse models of Mesenchymal and Non-Mesenchymal HGSOC, we show here that HGSOC exhibit distinct stiffness depending on their molecular subtype. Indeed, tumor stiffness strongly correlates with tumor growth in Mesenchymal HGSOC, while Non-Mesenchymal tumors remain soft. Moreover, we observe that tumor stiffening is associated with high stromal content, collagen network remodeling, and MAPK/MEK pathway activation. Furthermore, tumor stiffness accompanies a glycolytic metabolic switch in the epithelial compartment, as expected based on Warburg’s effect, but also in stromal cells. This effect is restricted to the central part of stiff Mesenchymal tumors. Indeed, stiff Mesenchymal tumors remain softer at the periphery than at the core, with stromal cells secreting high levels of collagens and showing an OXPHOS metabolism. Thus, our study suggests that tumor stiffness could be at the crossroad of three major processes, i.e. matrix remodeling, MEK activation and stromal metabolic switch that might explain at least in part Mesenchymal HGSOC aggressiveness.

The tumour stroma is an active participant during cancer progression. Stromal cells promote tumour progression and metastasis through multiple mechanisms including enhancing tumour invasiveness and angiogenesis, and suppressing immune surveillance. We report here that miR-126/miR-126 * , a microRNA pair derived from a single precursor, independently suppress the sequential recruitment of mesenchymal stem cells and inflammatory monocytes into the tumour stroma to inhibit lung metastasis by breast tumour cells in a mouse xenograft model. miR-126/miR-126 * directly inhibit stromal cell-derived factor-1 alpha (SDF-1α) expression, and indirectly suppress the expression of chemokine (C–C motif) ligand 2 (Ccl2) by cancer cells in an SDF-1α-dependent manner. miR-126/miR-126 * expression is downregulated in cancer cells by promoter methylation of their host gene Egfl7 . These findings determine how this microRNA pair alters the composition of the primary tumour microenvironment to favour breast cancer metastasis, and demonstrate a correlation between miR-126/126 * downregulation and poor metastasis-free survival of breast cancer patients. Wang and colleagues show that miR-126 and miR-126 * suppress metastasis by inhibiting the production of the Sdf-1α cytokine in mouse mammary tumours, resulting in decreased recruitment of mesenchymal stem cells and inflammatory monocytes to the tumour stroma.

In recent years it has become clear that the therapeutic properties of bone marrow-derived mesenchymal stromal cells (MSC) are related not only to their ability to differentiate into different lineages but also to their capacity to suppress the immune response. We here studied the influence of MSC on macrophage function. Using mouse thioglycolate-elicited peritoneal macrophages (M) stimulated with LPS, we found that MSC markedly suppressed the production of the inflammatory cytokines TNF-alpha, IL-6, IL-12p70 and interferon-gamma while increased the production of IL-10 and IL-12p40. Similar results were observed using supernatants from MSC suggesting that factor(s) constitutively released by MSC are involved. Supporting a role for PGE(2) we observed that acetylsalicylic acid impaired the ability of MSC to inhibit the production of inflammatory cytokines and to stimulate the production of IL-10 by LPS-stimulated M. Moreover, we found that MSC constitutively produce PGE2 at levels able to inhibit the production of TNF-alpha and IL-6 by activated M. MSC also inhibited the up-regulation of CD86 and MHC class II in LPS-stimulated M impairing their ability to activate antigen-specific T CD4+ cells. On the other hand, they stimulated the uptake of apoptotic thymocytes by M. Of note, MSC turned M into cells highly susceptible to infection with the parasite Trypanosoma cruzi increasing more than 5-fold the rate of M infection. Using a model of inflammation triggered by s.c. implantation of glass cylinders, we found that MSC stimulated the recruitment of macrophages which showed a low expression of CD86 and the MHC class II molecule Ia(b) and a high ability to produce IL-10 and IL-12p40, but not IL-12 p70. In summary, our results suggest that MSC switch M into a regulatory profile characterized by a low ability to produce inflammatory cytokines, a high ability to phagocyte apoptotic cells, and a marked increase in their susceptibility to infection by intracellular pathogens.

Osteosarcoma (OS) is an aggressive bone malignancy with a high relapse rate despite combined treatment with surgery and multiagent chemotherapy. As for other cancers, OS-associated microenvironment may contribute to tumor initiation, growth, and metastasis. We consider mesenchymal stromal cells (MSC) as a relevant cellular component of OS microenvironment, and have previously found that the interaction between MSC and tumor cells is bidirectional: tumor cells can modulate their peripheral environment that in turn becomes more favorable to tumor growth through metabolic reprogramming. Here, we determined the effects of MSC on OS stemness and migration, two major features associated with recurrence and chemoresistance. The presence of stromal cells enhanced the number of floating spheres enriched in cancer stem cells (CSC) of the OS cell population. Furthermore, the co-culturing with MSC stimulated the migratory capacity of OS via TGFβ1 and IL-6 secretion, and the neutralizing antibody anti-IL-6 impaired this effect. Thus, stromal cells in combination with OS spheres exploit a vicious cycle where the presence of CSC stimulates mesenchymal cytokine secretion, which in turn increases stemness, proliferation, migration, and metastatic potential of CSC, also through the increase of expression of adhesion molecules like ICAM-1. Altogether, our data corroborate the concept that a comprehensive knowledge of the interplay between tumor and stroma that also includes the stem-like fraction of tumor cells is needed to develop novel and effective anti-cancer therapies.

BackgroundTumor-infiltrating lymphocytes (TILs) and their subsets contribute to breast cancer prognosis. We investigated the prognostic impact of CD3+, CD8+ and FOXP3+ TILs in patients with early intermediate/high-risk breast cancer treated with adjuvant anthracycline-based chemotherapy within two randomized trials conducted by our Group.MethodsWe examined 1011 patients (median follow-up 130.9 months) and their tumors for total, stromal (s) and intratumoral (i) CD3, CD8 and FOXP3 lymphocyte density (counts/mm2) on tissue-microarray cores by immunohistochemistry. Morphological sTIL density on whole H&E-stained sections was also evaluated.ResultsThe majority of TILs were CD3+. Total CD3 and CD8, sCD3 and sCD8, iCD3 and iCD8, sFOXP3 and iFOXP3 were strongly correlated (Spearman’s rho values > 0.6). High individual lymphocytic subsets and sTIL density were strongly associated with high tumor grade, higher proliferation and HER2-positive and triple-negative tumors (all p values < 0.001). Higher sTIL density (10% increments), high density of almost each individual marker and all-high profiles conferred favorable prognosis. However, when adjusted for sTIL density, stromal and intratumoral lymphocytic subsets lost their prognostic significance, while higher sTIL density conferred up to 15% lower risk for relapse. Independently of sTIL density, higher total CD3+ and CD8+ TILs conferred 35% and 28% lower risk for relapse, respectively.ConclusionsStromal and intratumoral CD3+, CD8+ and FOXP3+ TIL density do not seem to add prognostic information over the morphologically assessed sTIL density, which is worth introducing in routine histology reports.

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) in culture are derived from BM stromal cells or skeletal stem cells. Whereas MSCs have been exploited in clinical medicine, the identification of MSC-specific markers has been limited. Here, we report that a cell surface and secreted protein, Meflin, is expressed in cultured MSCs, fibroblasts and pericytes, but not other types of cells including epithelial, endothelial and smooth muscle cells. In vivo , Meflin is expressed by immature osteoblasts and chondroblasts. In addition, Meflin is found on stromal cells distributed throughout the BM and on pericytes and perivascular cells in multiple organs. Meflin maintains the undifferentiated state of cultured MSCs and is downregulated upon their differentiation, consistent with the observation that Meflin-deficient mice exhibit increased number of osteoblasts and accelerated bone development. In the bone and BM, Meflin is more highly expressed in primitive stromal cells that express platelet-derived growth factor receptor α and Sca-1 than the Sca-1-negative adipo-osteogenic progenitors, which create a niche for hematopoiesis. Those results are consistent with a decrease in the number of clonogenic colony-forming unit-fibroblasts within the BM of Meflin-deficient mice. These preliminary data suggest that Meflin is a potential marker for cultured MSCs and their source cells in vivo .

Background: Previous investigations in pancreatic cancer suggest a prognostic role for α -smooth muscle actin ( α -SMA) expression and stromal density in the peritumoural stroma. The aim of this study was to further validate the impact of α -SMA expression and stromal density in resectable pancreatic cancer patients treated with adjuvant gemcitabine compared with untreated patients. Methods: CONKO-001 was a prospective randomised phase III study investigating the role of adjuvant gemcitabine as compared with observation. Tissue samples of 162 patients were available for immunohistochemistry on tissue microarrays to evaluate the impact of α -SMA expression and stromal density impact on patient outcome. Results: High α -SMA expression in tumour stroma was associated with worse patient outcome (DFS: P= 0.05, OS: P= 0.047). A dense stroma reaction was associated with improved disease-free survival (DFS) and overall survival (OS) in the overall study population (DFS: P= 0.001, OS: P= 0.001). This positive prognostic impact was restricted to patients with no adjuvant treatment (DFS: P< 0.001, OS: P <0.001). In multivariable analysis, α -SMA and stromal density expression were independently predictive factors for survival. Conclusions: Our data confirm the negative prognostic impact of high α -SMA expression in pancreatic cancer patients after curatively intended resection. In contrast to former investigations, we found a positive prognostic impact for a dense stroma. This significant influence was restricted to patients who received no adjuvant therapy.

Fibroblasts are ubiquitous cells that demonstrate remarkable diversity. However, their origin and pathways of differentiation remain poorly defined. Here, we show that connective tissue growth factor (CTGF; also known as CCN2) is sufficient to induce human bone marrow mesenchymal stem/stromal cells (MSCs) to differentiate into fibroblasts. CTGF-stimulated MSCs lost their surface mesenchymal epitopes, expressed broad fibroblastic hallmarks, and increasingly synthesized collagen type I and tenacin-C. After fibroblastic commitment, the ability of MSCs to differentiate into nonfibroblastic lineages - including osteoblasts, chondrocytes, and adipocytes - was diminished. To address inherent heterogeneity in MSC culture, we established 18 single MSC-derived clones by limiting dilution. CTGF-treated MSCs were alpha-SMA-, differentiating into alpha-SMA+ myofibroblasts only when stimulated subsequently with TGF-beta1, suggestive of stepwise processes of fibroblast commitment, fibrogenesis, and pathological fibrosis. In rats, in vivo microencapsulated delivery of CTGF prompted postnatal connective tissue to undergo fibrogenesis rather than ectopic mineralization. The knowledge that fibroblasts have a mesenchymal origin may enrich our understanding of organ fibrosis, cancer stroma, ectopic mineralization, scarring, and regeneration.

The regenerative and immunomodulatory activity of mesenchymal stromal cells (MSCs) is partially mediated by secreted vesicular factors. Extracellular vesicles (EVs) exocytosed by MSCs are gaining increased attention as prospective non-cellular therapeutics for a variety of diseases. However, the lack of suitable in vitro assays to monitor the therapeutic potential of EVs currently restricts their application in clinical studies. We have evaluated a dual in vitro immunomodulation potency assay that reproducibly reports the inhibitory effect of MSCs on induced T-cell proliferation and the alloantigen-driven mixed leukocyte reaction of pooled peripheral blood mononuclear cells in a dose-dependent manner. Phytohemagglutinin-stimulated T-cell proliferation was inhibited by MSC-derived EVs in a dose-dependent manner comparable to MSCs. In contrast, inhibition of alloantigen-driven mixed leukocyte reaction was only observed for MSCs, but not for EVs. Our results support the application of a cell-based in vitro potency assay for reproducibly determining the immunomodulatory potential of EVs. Validation of this assay can help establish reliable release criteria for EVs for future clinical studies.

Human adipose-derived stromal cells (hASCs) are a promising cell source for bone tissue engineering. However, before the clinical application of hASCs for the treatment of bone defects, key questions require answers, including whether pre-osteoinduction (OI) and flow cytometric cell purification are indispensible steps for in vivo bone formation by hASCs. In this study, hASCs were purified by flow cytometric cell sorting (FCCS). The osteogenic capabilities of hASCs and purified hASCs with or without pre-osteoinduction were examined through in vitro and in vivo experiments. We found that pre-OI enhanced the in vitro osteogenic capacity of hASCs. However, 8 weeks after in vivo implantation, there were no significant differences between hASCs and hASCs that had undergone OI (hASCs+OI) or between purified hASCs and purified hASCs+OI (P>0.05). Interestingly, we also found that purified hASCs had an osteogenic potential similar to that of unpurified hASCs in vitro and in vivo. These results suggest that FCCS and in vitro pre-OI are not requirements for in vivo bone formation by hASCs.