Source Of Cancer-associated Fibroblasts Research Articles

Distance-depending transcriptome changes of pancreatic stellate cells in paracrine pancreatic ductal adenocarcinoma co-culture models

Pancreatic stellate cells (PSC) are one source of cancer-associated fibroblasts (CAF) and play, therefore, an essential role in pancreatic ductal adenocarcinoma (PDA). Paracrine signalling between PDA cells and CAF has been widely studied, yet external influences on paracrine crosstalk are poorly understood. This study aimed to gain a deeper insight into the communication of PSC and cancer cells under different co-culture conditions via analysis of PSC gene expression profiles. Two contactless co-culture models with tumor cells from the p48-Cre; lox-stop-lox-KrasG12D/+; lox-stop-lox-Trp53R172H/+ mouse model (KPC) and murine PSC separated through a microporous membrane and grown in different compartments (standard co-culture) or on different sides of the same membrane (inverse co-culture), were established. RNA-Sequencing analysis of PSC mRNA was performed 24 h and 72 h after co-culture with KPC cells. For selected genes, results were confirmed by quantitative RT-PCR and immunocytochemistry. Standard co-culture displayed 19 differentially expressed genes (DEG) at 24 h and 52 DEG at 72 h. In inverse co-culture, 800 DEG at 24 h and 2213 DEG at 72 h were enriched. PSC showed great heterogeneity in their gene expression profiles; however, mutually regulated genes of both co-cultures, such as VCAN and CHST11, could be identified. VCAN-protein–protein interaction-network analysis revealed several shared genes between co-culture models, such as SDC4 and FN1. In conclusion, PSC show a varying susceptibility to cancer cell signals depending on the co-culture method, with intensified transcriptome changes with closer proximity.

ITGA7 loss drives the differentiation of adipose-derived mesenchymal stem cells to cancer-associated fibroblasts.

Cancer-associated fibroblasts (CAFs) represent a major cellular component of the tumor (pre-)metastatic niche and play an essential role in omental dissemination of ovarian cancer. The omentum is rich in adipose, and adipose-derived mesenchymal stem cells (ADSCs) have been identified as a source of CAFs. However, the molecular events driving the phenotype shift of ADSCs remain largely unexplored. In this research, we focus on integrins, transmembrane receptors that have been widely involved in cellular plasticity. We found that integrin α7(ITGA7) was the only member of the integrin family that positively correlated with both overall survival and progression-free survival in ovarian cancer through GEPIA2. The immunohistochemistry signal of ITGA7 was apparent in the tumor stroma, and a lower omental ITGA7 level was associated with metastasis. Primary ADSCs were isolated from the omentum of patients with ovarian cancer and identified by cellular morphology, biomarkers, and multilineage differentiation. The conditional medium of ovarian cancer cells induced ITGA7 expression decrease and phenotypic changes in ADSCs. Downregulation of ITGA7 in primary omental ADSCs led to decrease in stemness properties and emerge of characteristic morphology and biomarkers of CAFs. Moreover, the conditioned medium of ADSCs with ITGA7 depletion exhibited enhanced abilities to improve the migration and invasion of ovarian cancer cells in vitro. Overall, these findings indicate that loss of ITGA7 may induce the differentiation of ADSCs to CAFs that contribute to a tumor-supportive niche.

Nudifloside, a Secoiridoid Glucoside Derived from Callicarpa nudiflora, Inhibits Endothelial-to-Mesenchymal Transition and Angiogenesis in Endothelial Cells by Suppressing Ezrin Phosphorylation.

Callicarpa nudiflora is a traditional folk medicine in China used for eliminating stasis to subdue swelling. Several compounds from Callicarpa nudiflora have been proved to show anti-inflammatory, haemostasis, hepatitis, and anti-proliferative effects. Tumor endothelial cells play crucial roles in tumor-induced angiogenesis. Recently, it was demonstrated that ECs may be the important source of cancer associated fibroblasts (CAFs) through endothelial to mesenchymal transition (EndoMT). In this study, we evaluated the effects of nudifloside (NDF), a secoiridoid glucoside from Callicarpa Nudiflora, on TGF-β1-induced EndoMT and VEGF-induced angiogenesis, and the underlying mechanisms were also involved. It was found that NDF significantly inhibited enhanced migration, invasion and F-actin assembly in endothelial cells (ECs) exposed in TGF-β1. NDF obviously reversed expression of several biomarkers associated with EndoMT and recovered the morphological characteristics of ECs and tube-like structure induced by TGF-β1. Furthermore, treatment of NDF resulted in a significant destruction of VEGF-induced angiogenesis in vitro and ex vivo. Data from co-immunoprecipitation assay provided the evidence that Ezrin phosphorylation and the interaction with binding protein can be inhibited by NDF, which can be confirmed by data from Ezrin silencing assay. Collectively, the application of NDF inhibited TGF-β1-induced EndoMT and VEGF-induced angiogenesis in ECs by reducing Ezrin phosphorylation.

Macrophages are primed to transdifferentiate into fibroblasts in malignant ascites and pleural effusions

Cancer-associated fibroblasts (CAFs) play an important role in cancer progression. However, the origin of CAFs remains unclear. This study shows that macrophages in malignant ascites and pleural effusions (cavity fluid-associated macrophages: CAMs) transdifferentiate into fibroblast-like cells. CAMs obtained from gastrointestinal cancer patients were sorted by flow cytometry and cultured in vitro. CD45+CD14+ CAMs transdifferentiated into CD45−CD90+ fibroblast-like cells that exhibited spindle shapes. Then, cDNA microarray analysis showed that the CD45−CD90+ fibroblast-like cells (macrophage-derived CAFs: MDCAFs) had a fibroblast-specific gene expression signature and produced growth factors for epithelial cell proliferation. Human colon cancer cells transplanted into immunodeficient mice with MDCAFs formed larger tumors than cancer cells alone. Gene ontology analyses showed the involvement of TGFβ signaling and cell-matrix adhesion in MDCAFs, and transdifferentiation of CAMs into MDCAFs was canceled by inhibiting TGFβ and cell adhesion. Furthermore, the acquired genetic alterations in hematopoietic stem cells (HSCs) were shared in CAMs and MDCAFs. Taken together, CAMs could be a source of CAFs and might originate from HSCs. We propose the transdifferentiation process of CAMs into MDCAFs as a new therapeutic target for fibrosis associated with gastrointestinal cancer.

CD34+ Stromal Cells/Telocytes as a Source of Cancer-Associated Fibroblasts (CAFs) in Invasive Lobular Carcinoma of the Breast

Several origins have been proposed for cancer-associated fibroblasts (CAFs), including resident CD34+ stromal cells/telocytes (CD34+SCs/TCs). The characteristics and arrangement of mammary CD34+SCs/TCs are well known and invasive lobular carcinoma of the breast (ILC) is one of the few malignant epithelial tumours with stromal cells that can express CD34 or αSMA, which could facilitate tracking these cells. Our objective is to assess whether tissue-resident CD34+SCs/TCs participate in the origin of CAFs in ILCs. For this purpose, using conventional and immunohistochemical procedures, we studied stromal cells in ILCs (n:42) and in normal breasts (n:6, also using electron microscopy). The results showed (a) the presence of anti-CD34+ or anti-αSMA+ stromal cells in varying proportion (from very rare in one of the markers to balanced) around nests/strands of neoplastic cells, (b) a similar arrangement and location of stromal cells in ILC to CD34+SCs/TCs in the normal breast, (c) both types of stromal cells coinciding around the same nest of neoplastic cells and (d) the coexpression of CD34 and αSMA in stromal cells in ILC. In conclusion, our findings support the hypothesis that resident CD34+SCs/TCs participate as an important source of CAFs in ILC. Further studies are required in this regard in other tumours.

Abstract PO028: Embryonic protein NODAL as a potential modulator of the tumour microenvironment: Breast cancer secretome reprogramming and fibroblast activation

Abstract The tumour microenvironment (TME), consisting of stromal cell types including fibroblasts, endothelial, immune and mesenchymal stromal cells (MSCs), is an important mediator of breast cancer (BCa) progression. BCa cells regulate the composition of the TME by secreting a myriad of factors; however, mechanisms governing the dynamic reciprocity between BCa and TME components are largely unknown. Cancer-associated fibroblasts (CAFs) are a major stromal component in many BCa and have been shown to be activated by BCa cells. MSCs recruited to the TME are an important source of CAFs in many cancers; therefore, characterizing the factors involved in MSC recruitment could provide additional avenues for therapeutic intervention by disrupting the TME in BCa. NODAL, an embryonic morphogen belonging to the TGF-beta superfamily, is clinically associated with BCa progression, and has been shown to sustain BCa stem cells and to promote tumour growth, metastasis, and vascularization. Herein, we report that NODAL expression positively correlates with the presence of CAFs in the stroma of triple-negative human BCa tissues, as determined by NODAL and a-smooth muscle Actin (SMA) staining. Further, our in vitro studies show that NODAL directly induces primary fibroblast activation and chemotaxis. Proteomic analysis of the conditioned media of NODAL-overexpressing MDA-MB-231 and SUM149 BCa cells by mass spectrometry reveal that NODAL reprograms BCa secretomes by simultaneously altering levels of chemokines (e.g. CXCL1), growth factors (e.g. PDGFRA) and cytokines (e.g. IL-6), and that the NODAL-regulated secretome, but not NODAL directly, impacts the ability of BCa cells to affect MSC chemotaxis. We provide evidence that IL-6 promotes MSC chemotaxis, and further discuss the context-dependent effects of NODAL in BCa cell lines. Collectively, our results suggest that factors present in NODAL-regulated secretomes may induce MSC recruitment to the breast TME, where they may contribute to CAF population, therefore demonstrating a hitherto unappreciated role of NODAL as a dynamic regulator of breast TME components. Citation Format: Dylan Dieters-Castator, Paola M. Dantonio, Matt Piaseczny, Guihua Zhang, Jiahui Liu, Miljan Kuljanin, Stephen Sherman, Michael Jewer, Katherine Quesnel, Eun-Young Kang, Martin Köbel, Gabrielle M. Siegers, Andrew Leask, David Hess, Gilles Lajoie, Lynne-Marie Postovit. Embryonic protein NODAL as a potential modulator of the tumour microenvironment: Breast cancer secretome reprogramming and fibroblast activation [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PO028.

Abstract I01: Mechanisms and consequences of pancreatic cancer stromal evolution

Abstract The mechanisms underlying evolution of tumor-associated stroma remain poorly understood. Pancreatic ductal adenocarcinoma (PDAC) is the archetype of a fibroinflammatory malignancy, with 50-90% of tumor volume occupied by a dense, desmoplastic stroma. Cancer-associated fibroblasts (CAFs) are the key cell type driving the stromal reaction in PDAC. Recent reports suggest that PDAC CAFs represent a heterogeneous population of cells from diverse origins, potentially including cell types that support and others that suppress tumor growth. Pancreatic stellate cells (PSCs) are lipid-storing cells in healthy pancreas that can transdifferentiate to an activated CAF phenotype. PSCs have been suggested as the predominant source of CAFs in the PDAC microenvironment. However, proper lineage tracing studies have never been performed, such that the relative contribution and specific functions of PSCs in the tumor microenvironment are unknown. We have taken advantage of a novel mouse model we developed to track PSC differentiation and function during pancreatic tumor progression in vivo. This model leverages the unique lipid-storing origin of PSC-derived CAFs, and enables their distinction from CAFs of non-PSC origin for the first time. We hypothesized that PSC-derived fibroblasts in the PDAC microenvironment are a proinflammatory and tumor-supportive subset of PDAC CAFs, and thus represent a viable therapeutic target. Our preliminary data support the notion that PSCs contribute to only a subset of the CAF population in the tumor microenvironment, and the functions of these distinct populations are entirely unknown. Our data also highlight a potential role for genetic alterations in the epithelial compartment in orchestration of stromal fibroblast evolution. Using our model, we have interrogated PDAC stromal heterogeneity and functional significance, analyzed the distinguishing features of CAF subpopulations from disparate origins, and determined the significance of genetic alterations in the epithelial compartment on stromal cell fate and function. Together, these studies have the potential to lay the foundation for development of stroma-targeted therapies based on careful lineage tracing and molecular data. These findings shed light on mechanisms of stromal evolution during pancreatic tumorigenesis, and potentially identify distinct CAF populations of relevance in additional solid tumors. Citation Format: Mara Sherman. Mechanisms and consequences of pancreatic cancer stromal evolution [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr I01.

Meflin-Positive Cancer-Associated Fibroblasts Inhibit Pancreatic Carcinogenesis.

Cancer-associated fibroblasts (CAF) constitute a major component of the tumor microenvironment. Recent observations in genetically engineered mouse models and clinical studies have suggested that there may exist at least two functionally different populations of CAFs, that is, cancer-promoting CAFs (pCAF) and cancer-restraining CAFs (rCAF). Although various pCAF markers have been identified, the identity of rCAFs remains unknown because of the lack of rCAF-specific marker(s). In this study, we found that Meflin, a glycosylphosphatidylinositol-anchored protein that is a marker of mesenchymal stromal/stem cells and maintains their undifferentiated state, is expressed by pancreatic stellate cells that are a source of CAFs in pancreatic ductal adenocarcinoma (PDAC). In situ hybridization analysis of 71 human PDAC tissues revealed that the infiltration of Meflin-positive CAFs correlated with favorable patient outcome. Consistent herewith, Meflin deficiency led to significant tumor progression with poorly differentiated histology in a PDAC mouse model. Similarly, genetic ablation of Meflin-positive CAFs resulted in poor differentiation of tumors in a syngeneic transplantation model. Conversely, delivery of a Meflin-expressing lentivirus into the tumor stroma or overexpression of Meflin in CAFs suppressed the growth of xenograft tumors. Lineage tracing revealed that Meflin-positive cells gave rise to α-smooth muscle actin-positive CAFs that are positive or negative for Meflin, suggesting a mechanism for generating CAF heterogeneity. Meflin deficiency or low expression resulted in straightened stromal collagen fibers, which represent a signature for aggressive tumors, in mouse or human PDAC tissues, respectively. Together, the data suggest that Meflin is a marker of rCAFs that suppress PDAC progression. SIGNIFICANCE: Meflin marks and functionally contributes to a subset of cancer-associated fibroblasts that exert antitumoral effects.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/20/5367/F1.large.jpg.

MRTF-A controls myofibroblastic differentiation of human multipotent stromal cells and their tumour-supporting function in xenograft models

Tumour growth and metastatic colonization is strongly influenced by the tumour stroma, including cancer-associated fibroblasts (CAF). Multipotent mesenchymal stromal cells (MSC) are a possible source of CAF following myofibroblastic differentiation, and we have previously shown that MSC support tumour growth. Triggered by tumour cell-derived factors like transforming growth factor β1 (TGF-β1), myofibroblastic MSC differentiation is associated with the increased expression of markers including alpha smooth muscle actin (α-SMA). Here we show that myocardin-related transcription factor A (MRTF-A) plays an important role in myofibroblastic differentiation of primary human MSC in vitro and their tumour-supporting function in vivo. Recombinant TGF-β1 or tumour cell conditioned medium (TCM) elevated α-SMA, calponin 1 and collagen 1 A1 (COL1A1) amount on mRNA and protein level in MSC. This correlated with increased MRTF-A activity during MSC differentiation. MRTF-A knockdown by siRNA or shRNA impaired TGF-β1 and TCM induction of α-SMA and calponin 1, but not of COL1A1. Mixed xenograft experiments using HCT8 colorectal carcinoma cells and primary MSC of different donors revealed a significant reduction in tumour weight and volume upon MRTF-A knockdown in MSC. Our study suggests that MRTF-A is involved in the functional differentiation of MSC towards a tumour-promoting CAF phenotype in vivo.

Ovarian stromal cells as a source of cancer-associated fibroblasts in human epithelial ovarian cancer: A histopathological study.

Fibroblasts are a major component of cancer tissue and known to contribute to cancer progression. However, it remains unknown whether they are derived from local fibroblasts or of other origin. This study was designed to identify the contribution of local stromal cells to cancer stroma in human epithelial ovarian cancer. Seventy-six cases of surgically resected primary ovarian carcinoma (48 cases confined to the ovaries and 28 cases with distant metastases) and 17 cases of secondary ovarian tumor (e.g. colon cancer metastasized to the ovary) were enrolled in this study. The tissues were immunostained for forkhead box protein L2 (FOXL2), a transcription factor crucial for ovarian development and function, and markers for cancer-associated fibroblasts (CAFs) and inflammatory cells. Under normal condition, FOXL2 expression was restricted to ovarian stromal cells and some other types of cells in female genital tracts and never found in other sites of the body. FOXL2-positive cells were found in all primary and secondary tumors in the ovary, and were the dominant stromal cells in most cases. In contrast, only a few FOXL2-positive cells were found in peritoneal seeding sites of four serous carcinoma cases, and all the other tumors at extraovarian sites had no FOXL2-positive cells. FOXL2-positive cells in the ovarian lesion variably expressed CAFs markers, such as alpha-smooth muscle actin and fibroblast activating protein, as determined by double immunostaining. Background inflammation, but not histological subtype or origin of the neoplasm seemed to correlate with the proportion of FOXL2-positive cells. These results suggest that ovarian stromal cells are the main source of cancer stroma in the ovary but do not seem to move to distant sites via circulation together with tumor cells. Our results also support the hypothesis that cancer-associated fibroblasts may originate locally, which was previously demonstrated using animal models.

Regulation of pancreatic stellate cell activation by Notch3

BackgroundActivated pancreatic stellate cells (PaSCs) are the key cellular source of cancer-associated fibroblasts in the pancreatic stroma of patients with pancreatic ductal adenocarcinoma (PDAC), however, the activation mechanism of PaSCs is not yet known. The Notch signaling pathway, components of which are expressed in stromal cells, is involved in the fibrosis of several organs, including the lung and liver. In the current study, we investigated whether Notch signal transduction is involved in PaSC activation in PDAC.MethodsThe expression of Notch signaling pathway components in human PDAC was examined via immunohistochemical staining and assessed in mouse PaSCs using RT-qPCR and western blotting. Notch3 expression in both PDAC stromal cells and activated mouse PaSCs was evaluated using immunofluorescence, RT-qPCR and western blotting. The impact of siRNA-mediated Notch3 knockdown on PaSC activation was detected with RT-qPCR and western blotting, and the impact on PaSC proliferation and migration was detected using CCK-8 assays and scratch experiments. The effect of conditioned medium from PaSCs activated with Notch3 siRNA on pancreatic cancer (LTPA) cells was also detected with CCK-8 assays and scratch experiments. The data were analyzed for statistical significance using Student’s t-test.ResultsNotch3 was overexpressed in both human PDAC stromal cells and activated mouse PaSCs, and Notch3 knockdown with Notch3 siRNA decreased the proliferation and migration of mouse PaSCs. The levels of markers related to PaSC activation, such as α-smooth muscle actin (α-SMA), collagen I and fibronectin, decreased in response to Notch3 knockdown, indicating that Notch3 plays an important role in PaSC activation. Furthermore, we confirmed that inhibition of PaSC activation via Notch3 siRNA reduced the proliferation and migration of PaSC-induced mouse pancreatic cancer (LTPA) cells.ConclusionsNotch3 inhibition in PaSCs can inhibit the activation, proliferation and migration of PaSCs and reduce the PaSC-induced pro-tumorigenic effect. Therefore, Notch3 silencing in PaSCs is a potential novel therapeutic option for patients with PDAC.

Abstract P4-04-24: Metastatic lymph node fibroblasts maintain similar profile of stromal biomarkers registered in primary breast carcinomas

Abstract Background: Lymph node metastasis is the predominant dissemination route of breast carcinoma (BC) and remains as an important prognostic indicator of this disease. Several studies demonstrated a similar gene profiling or gene/biological markers assessed by immunohistochemistry in neoplastic epithelial cells at both sites. Recent evidence pointed that cancer associated fibroblasts (CAFs) play a critical role in breast cancer progression and migration. The evidence of CAFs in close association to epithelial tumor cells within lymph node metastasis raised the possibility of a common source of CAFs in these two lesions. However, little is known about the differentially expressed genes or proteins between fibroblasts of the primary tumor and its nodal metastasis. The contribution of CAFs in lymph node colonization is still unknown. Objective: Our aim was to compare the profile of biomarkers between fibroblasts in lymph nodes and those found in the primaries. We compared differences in frequency of activated CAFs through the expression of α-SMA and S100A4 in 43 matched pairs of invasive breast carcinomas and respective macro-metastatic lymph nodes arrayed in TMAs. We also investigated a panel of immunohistochemical biomarkers associated to TGFβ1 (that induces α-SMA and myofibroblast differentiation in CAFs) including CXCR4, pAKT, pm-TOR and c-myc. In addition the frequency of all these markers were assessed in samples of matched disease free lymph nodes obtained from the same patients (which contain fibroblastic reticular cells, limited to the exterior capsule). Results: CAFs characterization confirmed the positive expression of α-SMA (approximately 50%) and S100A4 (100%) on fibroblasts of both sites in contrast to uninvolved lymph nodes, which were uniformly negative. As expected, CAFs were ER, PR, Her-2, CD9 and p53 negative at both sites. As KI67 labeling rate was always lower than 10% in fibroblasts they were considered negative. Comparison between fibroblasts from the stromal component of the primaries and respective lymph nodes indicated that the frequency of TGFβ1, CXCR4 and pAKT positivity was similar whereas a significant lower rate of c-myc and pm-TOR frequency was observed in the metastatic lymph nodal fibroblasts. All biological markers were negative in normal lymph nodes highlighting their association with activated fibroblasts. None of the markers showed association with presence/absence of lymph node metastasis or with other clinic-pathological parameters. Primary carcinomas lacked any potential associations among the evaluated biological markers in fibroblast cells, however, in the stromal tissue of lymph nodes, significant relationships between TGFβ1 and CXCR4, pAKT and c-myc, were observed. Conclusion: Our results indicated the presence of activated fibroblasts expressing α-SMA and S100A4 in fibroblasts of breast cancer primaries as well in their matched metastatic lymph nodes. High concordance for the expression of the analyzed biomarkers in matched pairs of breast cancer primaries and metastatic lymph nodes suggested the maintenance of a similar supportive microenvironment in metastatic sites. Financial Support: FAPESP and CNPq. Citation Format: Fiorita GL Mundim, Fatima S Pasini, Suely Nonogaki, Fernando A Soares, M Mitzi Brentani, Angela F Logullo. Metastatic lymph node fibroblasts maintain similar profile of stromal biomarkers registered in primary breast carcinomas [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-04-24.

Bone marrow derived "fibrocytes" contribute to tumor proliferation and fibrosis in gastric cancer.

BackgroundCancer-associated fibroblasts (CAFs) in the stroma are considered to play important roles for gastric cancer proliferation, invasion, and fibrosis, but the source of CAFs and their interaction with cancer cells in the microenvironment have not been fully determined. Here we elucidated the role of bone marrow-derived cells, fibrocytes, in development of gastric cancers, as represented by scirrhous gastric cancer.Materials and methodsIn co-culturing MKN45 gastric cancer cells and purified fibrocytes from healthy volunteers, migration and endothelial mesenchymal transition associated gene expression were evaluated using western blot analysis. Also, mouse xenograft models of MKN45 with or without fibrocytes were conducted to investigate their tumorigenicity and immunohistological differences of tumors.ResultsCo-culture of fibrocytes with MKN45 resulted in morphological changes from cobblestone-shape to spindle-shape and enhanced expression of α-SMA and collagen type I in fibrocytes, suggesting that co-culture with gastric cancer cells may have induced the differentiation of fibrocytes to myofibroblasts. Furthermore, enhanced expression of SDF-1 in MKN45 and CXCR4 in fibrocytes were also determined. Mouse xenograft models inoculated with MKN45 and fibrocytes revealed significantly larger tumors than those inoculated with MKN45 cells alone, and the stroma in co-inoculated tumors consisted of myofibroblasts and fibrosis. Mouse-derived cells expressing both CD45 and type I collagen were also observed in co-inoculated tumors.ConclusionFibrocytes derived from bone marrow may migrate into the microenvironment of gastric cancer by SDF-1/CXCR4 system, and enhance the tumor proliferation and fibrosis as CAFs.

Discovery of Endothelium and Mesenchymal Properties of Primo Vessels in the Mesentery

Recent evidences demonstrated that endothelial-to-mesenchymal transition (EndMT) has a crucial role in cancer and is recognized as a unique source of cancer-associated fibroblasts (CAFs). Primo vascular system (PVS) is a new circulatory system which may play an important role in cancer metastasis and regeneration. In the current study, we applied previously established time-saving method to identify primo vessels and further investigated the immunocytochemical properties of primo vessels. Both primo vessels and primary primo vessel cells in the mesentery expressed endothelial markers and fibroblast markers. Double-labeling experiments demonstrated that endothelial and fibroblast markers are coexpressed in primo vessels. In addition, under the stimulation of TGF-β1 in vitro, primary primo vessel cells differentiated into fibroblasts. Therefore, we found that primo vessels in the mesentery had a transitional structure between endothelium and mesenchymal. This is a new finding of EndMT in normal postnatal animals.

The role of endothelial–mesenchymal transition in development and pathological process

Epithelial-mesenchymal transition is an important developmental process, participates in tumor's formation, invasion, and metastasis and has been extensively studied. Recently, endothelial-mesenchymal transition (EndMT), a newly recognized type of cellular transdifferentiation, has been demonstrated to participate in a number of diseases by causing morphology changes and pathological processes. Previous studies showed that EndMT was a critical process of embryonic cardiac development. Not only that recent advances also suggested that EndMT occurred postnatally in cancer and cardiac fibrosis and emerged as a possible source of cancer-associated fibroblasts (CAFs). CAFs were found to acquire properties that promoted tumor development and metastasis formation. Resident endothelial cells undergoing EndMT lose their endothelial markers, acquire a mesenchymal or myofibroblastic phenotype, express mesenchymal cell products such as α-smooth muscle actin and type I collagen and develop invasive and migratory abilities. EndMT-derived cells are believed to function as fibroblasts in damaged tissue and may therefore have an important role in pathological process. However, little is known about the signaling mechanisms that cause endothelial cells to transform into mesenchymal cells. Transforming growth factor-β, Notch, or other signaling pathways could direct or interact to mediate EndMT. Therefore, to explore the signaling mechanisms of EndMT may provide novel therapeutic strategies for treating cancer.

The advancement of cancer-associated fibroblasts in lung cancer

癌相关成纤维细胞（cancer-associated fibroblasts, CAFs）是肿瘤组织中被癌细胞激活的成纤维细胞，具有成肌纤维细胞的特性。CAFs表型恶性转换与肿瘤演进密切相关，同时CAFs是肿瘤微环境的主要组织成分。本文主要从以下方面结合肺癌进行综述：①CAFs的来源及其形态学特征，CAFs异质性及其表型时、空转换的临床意义；②CAFs的研究现状及临床应用中的问题；③CAFs与肺癌侵袭与转移的关系；④CAFs对肺癌预后及其治疗的影响。