Tumor cell communication through EVs: new challenges and opportunities

2019 ◽  
Vol 1 (1) ◽  
pp. 27-30
Author(s):  
Cecile L. Maire ◽  
Franz L. Ricklefs
Keyword(s):  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Intercellular Communication ◽  
Liquid Biopsy ◽  
Cell Communication ◽  
Potential Utility ◽  
Challenges And Opportunities ◽  
New Challenges ◽  
Substantial Interest

Extracellular vesicles (EVs) are small, heterogeneous, lipid-bilayer particles that are potent vehicles of intercellular communication, contributing to the interaction of tumor cells with the microenvironment and promoting tumor growth. Furthermore, EVs have gained substantial interest due to their potential utility for liquid biopsy approaches in cancer.

scholarly journals ATRT-14. MACROPHAGE-TUMOR CELL INTERACTION PROMOTES ATRT PROGRESSION AND CHEMORESISTANCE

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii278-iii278
Author(s):  
Viktoria Melcher ◽  
Monika Graf ◽  
Marta Interlandi ◽  
Natalia Moreno ◽  
Flavia W de Faria ◽  
...  
Keyword(s):  
Tumor Cell ◽  
Tumor Cells ◽  
Chemotherapy Resistance ◽  
Cell Communication ◽  
Xenograft Model ◽  
Cell Interaction ◽  
Immunofluorescent Staining ◽  
Genetic Traits ◽  
Rhabdoid Tumors

Abstract Atypical teratoid/rhabdoid tumors (ATRT) are pediatric brain neoplasms that are known for their heterogeneity concerning pathophysiology and outcome. The three genetically rather uniform but epigenetically distinct molecular subgroups of ATRT alone do not sufficiently explain the clinical heterogeneity. Therefore, we examined the tumor microenvironment (TME) in the context of tumor diversity. By using multiplex-immunofluorescent staining and single-cell RNA sequencing (scRNA-seq) we unveiled the pan-macrophage marker CD68 as a subgroup-independent negative prognostic marker for survival of ATRT patients. ScRNA-seq analysis of murine ATRT-SHH, ATRT-MYC and extracranial RT (eRT) provide a delineation of the TME, which is predominantly infiltrated by myeloid cells: more specifically a microglia-enriched niche in ATRT-SHH and a bone marrow-derived macrophage infiltration in ATRT-MYC and eRT. Exploring the cell-cell communication of tumor cells with tumor-associated immune cells, we found that Cd68+ tumor-associated macrophages (TAMs) are central to intercellular communication with tumor cells. Moreover, we uncovered distinct tumor phenotypes in murine ATRT-MYC that share genetic traits with TAMs. These intermediary cells considerably increase the intratumoral heterogeneity of ATRT-MYC tumors. In vitro co-culture experiments recapitulated the capability of ATRT-MYC cells to interchange cell material with macrophages extensively, in contrast to ATRT-SHH cells. We found that microglia are less involved in the exchange of information with ATRT cells and that direct contact is a prerequisite for incorporation. A relapse xenograft model implied that intermediary cells are involved in the acquisition of chemotherapy resistance. We show evidence that TAM-tumor cell interaction is one mechanism of chemotherapy resistance and relapse in ATRT.

scholarly journals Tumor quiescence: elevating SOX2 in diverse tumor cell types downregulates a broad spectrum of the cell cycle machinery and inhibits tumor growth

BMC Cancer ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Ethan P. Metz ◽  
Erin L. Wuebben ◽  
Phillip J. Wilder ◽  
Jesse L. Cox ◽  
Kaustubh Datta ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Molecular Mechanisms ◽  
Cell Types ◽  
Cell Cycle Machinery

Abstract Background Quiescent tumor cells pose a major clinical challenge due to their ability to resist conventional chemotherapies and to drive tumor recurrence. Understanding the molecular mechanisms that promote quiescence of tumor cells could help identify therapies to eliminate these cells. Significantly, recent studies have determined that the function of SOX2 in cancer cells is highly dose dependent. Specifically, SOX2 levels in tumor cells are optimized to promote tumor growth: knocking down or elevating SOX2 inhibits proliferation. Furthermore, recent studies have shown that quiescent tumor cells express higher levels of SOX2 compared to adjacent proliferating cells. Currently, the mechanisms through which elevated levels of SOX2 restrict tumor cell proliferation have not been characterized. Methods To understand how elevated levels of SOX2 restrict the proliferation of tumor cells, we engineered diverse types of tumor cells for inducible overexpression of SOX2. Using these cells, we examined the effects of elevating SOX2 on their proliferation, both in vitro and in vivo. In addition, we examined how elevating SOX2 influences their expression of cyclins, cyclin-dependent kinases (CDKs), and p27Kip1. Results Elevating SOX2 in diverse tumor cell types led to growth inhibition in vitro. Significantly, elevating SOX2 in vivo in pancreatic ductal adenocarcinoma, medulloblastoma, and prostate cancer cells induced a reversible state of tumor growth arrest. In all three tumor types, elevation of SOX2 in vivo quickly halted tumor growth. Remarkably, tumor growth resumed rapidly when SOX2 returned to endogenous levels. We also determined that elevation of SOX2 in six tumor cell lines decreased the levels of cyclins and CDKs that control each phase of the cell cycle, while upregulating p27Kip1. Conclusions Our findings indicate that elevating SOX2 above endogenous levels in a diverse set of tumor cell types leads to growth inhibition both in vitro and in vivo. Moreover, our findings indicate that SOX2 can function as a master regulator by controlling the expression of a broad spectrum of cell cycle machinery. Importantly, our SOX2-inducible tumor studies provide a novel model system for investigating the molecular mechanisms by which elevated levels of SOX2 restrict cell proliferation and tumor growth.

Tumor Cell Thrombin/PAR-1 Signaling Drives Pancreatic Ductal Adenocarcinoma Growth and Dissemination

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1070-1070
Author(s):  
Matthew J. Flick ◽  
Cheryl Rewerts ◽  
Carolina Cruz ◽  
Joseph S. Palumbo ◽  
James P. Luyendyk ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Coagulation System ◽  
Ductal Adenocarcinoma ◽  
Parental Line ◽  
Experimental Metastasis ◽  
Primary Tumor Growth ◽  
Wild Type

Abstract Pancreatic ductal adenocarcinoma (PDAC) accounts for ~85% of diagnosed pancreatic cancers and is among the most lethal malignancies. The 5-year survival rate for pancreatic cancer patients has improved only marginally in the last 40 years (3% → 7%), with effectively no change in survival profile for patients with metastatic disease (2%). High mortality is linked to the aggressive and invasive nature of the malignancy and poor efficacy of limited treatment options, which collectively highlight the need for novel treatment strategies. Notably, analyses of pancreatic cancer in patients and animal models have demonstrated that PDAC is associated with robust coagulation system activity. Previous work has shown that patient PDAC tumor cells often express high levels of tissue factor (TF) and protease-activated receptor (PAR)-1. To determine the potential contribution of tumor cell derived-TF and PAR-1 to PDAC growth and metastasis, a novel tumor cell line (termed KPC2) was derived from mice in which PDAC tumorigenesis was induced by activation of two established pancreatic cancer alleles, KrasG12D and Trp53R172H. In transplant studies, tumor growth and experimental metastasis were evaluated using KPC2 cells in which TF or PAR-1 expression was suppressed by shRNA knockdown. In addition, the interplay of tumor-derived TF and PAR-1 with host factors in promoting tumor growth and experimental metastasis were evaluated in mice with genetically imposed deficits in coagulation system components. TF knockdown (to ~10% of the parental line) in KPC2 cells resulted in a significant diminution of both primary tumor growth and experimental metastasis. This reduction appeared to be linked to thrombin activity as primary tumor growth and experimental metastasis of parental KPC2 cells were significantly reduced in fIIlow mice (which constitutively express 10% of normal prothrombin) relative to wild-type mice. PAR-1 knockout mice displayed similar KPC2 growth and experimental metastasis to wild-type animals indicating that stromal cell-derived PAR-1 was not significant determinant. In stark contrast, shRNA-mediated knockdown of PAR-1 in KPC2 (to ~10% of the parental line) cells resulted in significantly diminished tumor growth and experimental metastasis. Diminished tumor growth was linked to reduced expression of the macrophage chemokine MCP-1 and the metalloproteinase MMP9 by the tumor cells as well as reduced thrombin-stimulated ERK phosphorylation. Our results suggest that a major mechanism of PDAC growth and dissemination is through TF/thrombin-driven PAR-1 signaling on tumor cells. Disclosures No relevant conflicts of interest to declare.

Fibrinogen is an important determinant of the metastatic potential of circulating tumor cells

Blood ◽  
2000 ◽  
Vol 96 (10) ◽  
pp. 3302-3309 ◽  
Author(s):  
Joseph S. Palumbo ◽  
Keith W. Kombrinck ◽  
Angela F. Drew ◽  
Timothy S. Grimes ◽  
John H. Kiser ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Circulating Tumor Cells ◽  
Metastatic Potential ◽  
Thrombin Inhibitor ◽  
Tumor Dissemination ◽  
Hemostatic Factors ◽  
The Impact ◽  
Deficient Mice

Abstract Detailed studies of tumor cell–associated procoagulants and fibrinolytic factors have implied that local thrombin generation and fibrin deposition and dissolution may be important in tumor growth and dissemination. To directly determine whether fibrin(ogen) or plasmin(ogen) are determinants of the metastatic potential of circulating tumor cells, this study examined the impact of genetic deficits in each of these key hemostatic factors on the hematogenous pulmonary metastasis of 2 established murine tumors, Lewis lung carcinoma and the B16-BL6 melanoma. In both tumor models, fibrinogen deficiency strongly diminished, but did not prevent, the development of lung metastasis. The quantitative reduction in metastasis in fibrinogen-deficient mice was not due to any appreciable difference in tumor stroma formation or tumor growth. Rather, tumor cell fate studies indicated an important role for fibrin(ogen) in sustained adhesion and survival of tumor cells within the lung. The specific thrombin inhibitor, hirudin, further diminished the metastatic potential of circulating tumor cells in fibrinogen-deficient mice, although the inhibitor had no apparent effect on tumor cell proliferation in vitro. The absence of plasminogen and plasmin-mediated fibrinolysis had no significant impact on hematogenous metastasis. The authors concluded that fibrin(ogen) is a critical determinant of the metastatic potential of circulating tumor cells. Furthermore, thrombin appears to facilitate tumor dissemination through at least one fibrin(ogen)-independent mechanism. These findings suggest that therapeutic strategies focusing on multiple distinct hemostatic factors might be beneficial in the containment of tumor metastasis.

Selective, User-friendly, Highly Porous, Efficient, and Rapid (SUPER) Filter for Isolation and Analysis of Rare Tumor Cells

Lab on a Chip ◽  
2021 ◽  
Author(s):  
Kaifeng Zhao ◽  
Yaoping Liu ◽  
Hua Wang ◽  
Yanling Song ◽  
Xiao-Feng Chen ◽  
...  
Keyword(s):  
Tumor Cell ◽  
Tumor Cells ◽  
Clinical Application ◽  
Liquid Biopsy ◽  
Body Fluids ◽  
Selective Separation ◽  
Rare Tumor ◽  
Filtration System ◽  
User Friendly ◽  
Highly Porous

Rapid, efficient, and selective separation of tumor cells from complex body fluids is urgently needed for clinical application of tumor-cell-based liquid biopsy. Herein, a size-selective affinity filtration system, named Selective,...

Protease Activated Receptor-1 (PAR-1) Impedes Tumor Progression

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2560-2560
Author(s):  
Gregory N. Adams ◽  
Haley Weston ◽  
Leah Rosenfeldt ◽  
Malinda Frederick ◽  
Joseph S. Palumbo
Keyword(s):  
Cell Proliferation ◽  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Prostate Tumor ◽  
Protease Activated Receptor 1 ◽  
Tumor Types ◽  
And Control

Abstract Activation of cell signaling by thrombin through Protease Activated Receptor-1 (PAR-1) represents one important interface between blood coagulation and cell activation in response to injury and inflammation. In the context of cancer, PAR-1 has been suggested to promote tumor growth through mechanisms coupled to tumor cell proliferation, tumor cell migration, and the development of a supportive tumor stroma. Consistent with this view, both tumor cells and stromal cells express high levels of PAR-1, and elevated PAR-1 expression has been correlated with a poor prognosis across several tumor types. In the current studies, we tested the hypothesis that PAR-1 is a critical driver of tumorigenesis and tumor growth using murine models of genetically-induced prostate and intestinal tumor growth. To define the role of PAR-1 in prostate tumor progression, we interbred mice expressing the TRAMP transgene (transgenic adenocarcinoma of the mouse prostate; SV40 Large T antigen under the control of a probasin promoter) to PAR-1-deficient mice (PAR-1-/-) in order to generate male TRAMP mice with and without PAR-1 expression for detailed analyses of prostate tumor growth. Surprisingly, prostate tumors harvested from PAR-1-/- mice were significantly larger than those harvested from PAR-1+/+ mice. In order to begin to address the PAR-1 expressing cellular compartments responsible for prostate tumor inhibition, we subcutaneously inoculated immunocompetent C57Bl/6-derived PAR-1-/- and control mice with tumor cells derived from a C57Bl/6 TRAMP mouse. TRAMP-derived tumors grew indistinguishably in PAR-1-/- and control mice, suggesting that stromal-cell associated PAR-1 is dispensable for prostate tumor growth. We next tested the effect of tumor cell-intrinsic inhibition of PAR-1 in TRAMP tumor cells by viral transduction with a construct containing an shRNA against murine PAR-1 in parallel to a non-specific shRNA construct. Diminishing tumor cell-associated PAR-1 expression resulted in significantly more rapid tumor growth in vivo. In order to better define the role of tumor cell-intrinsic PAR-1 we harvested TRAMP tumor cells from a PAR-1 deficient mouse and grew these cells in vitro. We transduced these PAR-1-deficient prostate tumor cells with viral vectors conferring expression of WT murine PAR-1 (PAR-1+), a PAR-1 mutant lacking the thrombin cleavage (R41A mutant) or empty vector (PAR-1-). PAR-1- cells grew robustly and similarly to the parental cells in vitro with a doubling time of approximately 48 hours. Cells expressing the R41A mutant PAR-1 also grew robustly and similarly to PAR-1 deficient cells. However, PAR-1+ cells failed to show any signs of cell proliferation over the span of a 4 day observation period. Furthermore, PAR-1 expression dramatically altered the ability of TRAMP cells to demonstrate signs of cell spreading as measured by the frequency of pseudopodia per cell. As a means of determining the role of PAR-1 in tumorigenesis and tumor growth in another spontaneously occurring setting, we interbred PAR-1-/- mice with APCMin/+ mice genetically predisposed to intestinal adenoma formation due to loss of heterozygosity of the tumor suppressor adenomatous polyposis coli gene. Blinded quantitative histological analyses of the intestinal tracts of PAR-1-/- and PAR-1+/+ APCMin/+ mice revealed that PAR-1 deficiency resulted in a significant 2-fold increase in the number of adenomas observed. Furthermore, the adenomas observed in PAR-1-/- mice were significantly larger based on morphometric analyses of adenoma surface area in histological sections. In sum, these data demonstrate a surprising and unexpected role for PAR-1 in the inhibition of tumor growth in the context of two distinct tumor types. Disclosures No relevant conflicts of interest to declare.

Fibrinogen is an important determinant of the metastatic potential of circulating tumor cells

Blood ◽  
2000 ◽  
Vol 96 (10) ◽  
pp. 3302-3309 ◽  
Author(s):  
Joseph S. Palumbo ◽  
Keith W. Kombrinck ◽  
Angela F. Drew ◽  
Timothy S. Grimes ◽  
John H. Kiser ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Circulating Tumor Cells ◽  
Metastatic Potential ◽  
Thrombin Inhibitor ◽  
Tumor Dissemination ◽  
Hemostatic Factors ◽  
The Impact ◽  
Deficient Mice

Detailed studies of tumor cell–associated procoagulants and fibrinolytic factors have implied that local thrombin generation and fibrin deposition and dissolution may be important in tumor growth and dissemination. To directly determine whether fibrin(ogen) or plasmin(ogen) are determinants of the metastatic potential of circulating tumor cells, this study examined the impact of genetic deficits in each of these key hemostatic factors on the hematogenous pulmonary metastasis of 2 established murine tumors, Lewis lung carcinoma and the B16-BL6 melanoma. In both tumor models, fibrinogen deficiency strongly diminished, but did not prevent, the development of lung metastasis. The quantitative reduction in metastasis in fibrinogen-deficient mice was not due to any appreciable difference in tumor stroma formation or tumor growth. Rather, tumor cell fate studies indicated an important role for fibrin(ogen) in sustained adhesion and survival of tumor cells within the lung. The specific thrombin inhibitor, hirudin, further diminished the metastatic potential of circulating tumor cells in fibrinogen-deficient mice, although the inhibitor had no apparent effect on tumor cell proliferation in vitro. The absence of plasminogen and plasmin-mediated fibrinolysis had no significant impact on hematogenous metastasis. The authors concluded that fibrin(ogen) is a critical determinant of the metastatic potential of circulating tumor cells. Furthermore, thrombin appears to facilitate tumor dissemination through at least one fibrin(ogen)-independent mechanism. These findings suggest that therapeutic strategies focusing on multiple distinct hemostatic factors might be beneficial in the containment of tumor metastasis.

scholarly journals A Ticket to Ride: The Implications of Direct Intercellular Communication via Tunneling Nanotubes in Peritoneal and Other Invasive Malignancies

2020 ◽  
Vol 10 ◽  
Author(s):  
Emil Lou
Keyword(s):  
Tumor Growth ◽  
Cancer Progression ◽  
Intercellular Communication ◽  
Ex Vivo ◽  
Cell Communication ◽  
Filamentous Actin ◽  
Tunneling Nanotubes ◽  
Intercellular Transfer

It is well established that the role of the tumor microenvironment (TME) in cancer progression and therapeutic resistance is crucial, but many of the underlying mechanisms are still being elucidated. Even with better understanding of molecular oncology and identification of genomic drivers of these processes, there has been a relative lag in identifying and appreciating the cellular drivers of both invasion and resistance. Intercellular communication is a vital process that unifies and synchronizes the diverse components of the tumoral infrastructure. Elucidation of the role of extracellular vesicles (EVs) over the past decade has cast a brighter light on this field. And yet even with this advance, in addition to diffusible soluble factor-mediated paracrine and endocrine cell communication as well as EVs, additional niches of intratumoral communication are filled by other modes of intercellular transfer. Tunneling nanotubes (TNTs), tumor microtubes (TMs), and other similar intercellular channels are long filamentous actin-based cellular conduits (in most epithelial cancer cell types, ~15-500 µm in length; 50–1000+ nm in width). They extend and form direct connections between distant cells, serving as conduits for direct intercellular transfer of cell cargo, such as mitochondria, exosomes, and microRNAs; however, many of their functional roles in mediating tumor growth remain unknown. These conduits literally create a physical bridge to create a syncytial network of dispersed cells amidst the intercellular stroma-rich matrix. Emerging evidence suggests that they provide a cellular mechanism for induction and emergence of drug resistance and contribute to increased invasive and metastatic potential. They have been imaged in vitro and also in vivo and ex vivo in tumors from human patients as well as animal models, thus not only proving their existence in the TME, but opening further speculation about their exact role in the dynamic niche of tumor ecosystems. TNT cellular networks are upregulated between cancer and stromal cells under hypoxic and other conditions of physiologic and metabolic stress. Furthermore, they can connect malignant cells to benign cells, including vascular endothelial cells. The field of investigation of TNT-mediated tumor-stromal, and tumor-tumor, cell-cell communication is gaining momentum. The mixture of conditions in the microenvironment exemplified by hypoxia-induced ovarian cancer TNTs playing a crucial role in tumor growth, as just one example, is a potential avenue of investigation that will uncover their role in relation to other known factors, including EVs. If the role of cancer heterocellular signaling via TNTs in the TME is proven to be crucial, then disrupting formation and maintenance of TNTs represents a novel therapeutic approach for ovarian and other similarly invasive peritoneal cancers.

scholarly journals Leveling Up the Controversial Role of Neutrophils in Cancer: When the Complexity Becomes Entangled

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2486
Author(s):  
Ronit Vogt Sionov
Keyword(s):  
Tumor Growth ◽  
Tumor Cell ◽  
Cancer Cells ◽  
Tumor Cells ◽  
Immune Cell ◽  
Neutrophil Function ◽  
The Body ◽  
Cathepsin G ◽  
Metastatic Sites

Neutrophils are the most abundant immune cell in the circulation of human and act as gatekeepers to discard foreign elements that have entered the body. They are essential in initiating immune responses for eliminating invaders, such as microorganisms and alien particles, as well as to act as immune surveyors of cancer cells, especially during the initial stages of carcinogenesis and for eliminating single metastatic cells in the circulation and in the premetastatic organs. Since neutrophils can secrete a whole range of factors stored in their many granules as well as produce reactive oxygen and nitrogen species upon stimulation, neutrophils may directly or indirectly affect carcinogenesis in both the positive and negative directions. An intricate crosstalk between tumor cells, neutrophils, other immune cells and stromal cells in the microenvironment modulates neutrophil function resulting in both anti- and pro-tumor activities. Both the anti-tumor and pro-tumor activities require chemoattraction towards the tumor cells, neutrophil activation and ROS production. Divergence is seen in other neutrophil properties, including differential secretory repertoire and membrane receptor display. Many of the direct effects of neutrophils on tumor growth and metastases are dependent on tight neutrophil–tumor cell interactions. Among them, the neutrophil Mac-1 interaction with tumor ICAM-1 and the neutrophil L-selectin interaction with tumor-cell sialomucins were found to be involved in the neutrophil-mediated capturing of circulating tumor cells resulting in increased metastatic seeding. On the other hand, the anti-tumor function of neutrophils was found to rely on the interaction between tumor-surface-expressed receptor for advanced glycation end products (RAGE) and Cathepsin G expressed on the neutrophil surface. Intriguingly, these two molecules are also involved in the promotion of tumor growth and metastases. RAGE is upregulated during early inflammation-induced carcinogenesis and was found to be important for sustaining tumor growth and homing at metastatic sites. Cathepsin G was found to be essential for neutrophil-supported lung colonization of cancer cells. These data level up the complexity of the dual role of neutrophils in cancer.

scholarly journals Platelet microRNAs inhibit primary tumor growth via broad modulation of tumor cell mRNA expression in ectopic pancreatic cancer in mice

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261633
Author(s):  
Jeremy G. T. Wurtzel ◽  
Sophia Lazar ◽  
Sonali Sikder ◽  
Kathy Q. Cai ◽  
Igor Astsaturov ◽  
...  
Keyword(s):  
Gene Expression ◽  
Tumor Growth ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Solid Tumor ◽  
Primary Tumor ◽  
Primary Tumor Growth ◽  
Primary Tumors ◽  
Solid Tumor Growth

We investigated the contributions of platelet microRNAs (miRNAs) to the rate of growth and regulation of gene expression in primary ectopic tumors using mouse models. We previously identified an inhibitory role for platelets in solid tumor growth, mediated by tumor infiltration of platelet microvesicles (microparticles) which are enriched in platelet-derived miRNAs. To investigate the specific roles of platelet miRNAs in tumor growth models, we implanted pancreatic ductal adenocarcinoma cells as a bolus into mice with megakaryocyte-/platelet-specific depletion of mature miRNAs. We observed an ~50% increase in the rate of growth of ectopic primary tumors in these mice compared to controls including at early stages, associated with reduced apoptosis in the tumors, in particular in tumor cells associated with platelet microvesicles—which were depleted of platelet-enriched miRNAs—demonstrating a specific role for platelet miRNAs in modulation of primary tumor growth. Differential expression RNA sequencing of tumor cells isolated from advanced primary tumors revealed a broad cohort of mRNAs modulated in the tumor cells as a function of host platelet miRNAs. Altered genes comprised 548 up-regulated transcripts and 43 down-regulated transcripts, mostly mRNAs altogether spanning a variety of growth signaling pathways–notably pathways related to epithelial-mesenchymal transition—in tumor cells from platelet miRNA-deleted mice compared with those from control mice. Tumors in platelet miRNA-depleted mice showed more sarcomatoid growth and more advanced tumor grade, indicating roles for host platelet miRNAs in tumor plasticity. We further validated increased protein expression of selected genes associated with increased cognate mRNAs in the tumors due to platelet miRNA depletion in the host animals, providing proof of principle of widespread effects of platelet miRNAs on tumor cell functional gene expression in primary tumors in vivo. Together, these data demonstrate that platelet-derived miRNAs modulate solid tumor growth in vivo by broad-spectrum restructuring of the tumor cell transcriptome.

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