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At least 127 records · Page 7Linked to original sources
PubMed2005

Vascular targeting and antiangiogenesis agents induce drug resistance effector GRP78 within the tumor microenvironment.

Therapeutic targeting of the tumor vasculature that destroys preexisting blood vessels of the tumor and antiangiogenesis therapy capitalize on the requirement of tumor cells on an intact vascular supply for oxygen and nutrients for growth, expansion and metastasis to the distal organs. Whereas these classes of agents show promise in delaying tumor progression, they also create glucose and oxygen deprivation conditions within the tumor that could trigger unintended prosurvival responses. The glucose-regulated protein GRP78, a major endoplasmic reticulum chaperone, is inducible by severe glucose depletion, anoxia, and acidosis. Here we report that in a xenograft model of human breast cancer, treatment with the vascular targeting agent, combretastatin A4P, or the antiangiogenic agent, contortrostatin, promotes transcriptional activation of the Grp78 promoter and elevation of GRP78 protein in surviving tumor cells. We further show that GRP78 is overexpressed in a panel of human breast cancer cells that has developed resistance to a variety of drug treatment regimens. Suppression of GRP78 through the use of lentiviral vector expressing small interfering RNA sensitizes human breast cancer cells to etoposide-mediated cell death. Our studies imply that antivascular and antiangiogenesis therapy that results in severe glucose and oxygen deprivation will induce GRP78 expression that could lead to drug resistance.

Angiogenesis Inhibitors↗
PubMed1998

Interleukin 2 expression by tumor cells alters both the immune response and the tumor microenvironment.

Microenvironmental conditions within solid tumors can have marked effects on the growth of the tumors and their response to therapies. The disorganized growth of tumors and their attendant vascular systems tends to result in areas of the tumors that are deficient in oxygen (hypoxic). Cells within these hypoxic areas are more resistant to conventional therapies such as radiation and chemotherapy. Here, we examine the hypoxic state of EMT6 mouse mammary tumors and the location of host cells within the different areas of the tumors to determine whether such microenvironmental conditions might also affect their ability to be recognized by the immune system. Hypoxia within tumors was quantified by flow cytometry and visualized by immunohistochemistry using a monoclonal antibody (ELK3-51) against cellular adducts of 2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetam ide (EF5), a nitroimidazole compound that binds selectively to hypoxic cells. Thy-1+ cells, quantified using a monoclonal antibody, were found only in the well-oxygenated areas. The location of these Thy-1+ cells was also examined in EMT6 tumors that had been transfected with the gene for interleukin-2 (IL-2) because these tumors contain greatly increased numbers of host cells. Surprisingly, we found that IL-2-transfected tumors had significantly decreased hypoxia compared to parental tumors. Furthermore, using the fluorescent dye Hoechst 33342, an in vivo marker of perfused vessels, combined with immunochemical staining of PECAM-1 (CD31) as a marker of tumor vasculature, we found increased vascularization in the IL-2-transfected tumors. Thus, expression of IL-2 at the site of tumor growth may enhance tumor immunity not only by inducing the generation of tumor-reactive CTLs but also by allowing increased infiltration of activated T cells into the tumors.

Animals↗
PubMed2006

Modulation of immune response by B7 family molecules in tumor microenvironments.

The importance of co-stimulatory and co-inhibitory molecules has been confirmed on a grand scale; with the identification of new B7 family molecules, possessing both immune activating and inhibiting functions, this family has exploded onto the scene of immune regulation. Nowhere, however, has the role of B7 family members been more apparent than in the fight against cancer. In this review, we will discuss recent data regarding the essential and complex role of B7 family members in regulating the immune response within tumor microenvironment.

Animals↗
PubMed2005

Enzymatic remodeling of heparan sulfate proteoglycans within the tumor microenvironment: growth regulation and the prospect of new cancer therapies.

Heparan sulfate proteoglycans (HSPGs), via their interactions with numerous effector molecules such as FGF-2, IL-8, and VEGF, regulate the biological activity of cells by acting as co-receptors that promote signaling. The extent and nature of their role as co-receptors is often misregulated in cancer as manifested by alterations in HSPG structure and expression level. This misregulation of HSPGs can aid in promoting the malignant phenotype. In addition to expression-related changes in HSPGs, recent discoveries indicate that HSPGs localized within the tumor microenvironment can be attacked by enzymes that alter proteoglycan structure resulting in dramatic effects on tumor growth and metastasis. This review focuses on remodeling of HSPGs by three distinct mechanisms that occur in vivo; (i) shedding of proteoglycan extracellular domains from cell surfaces, (ii) fragmentation of heparan sulfate chains by heparanase, and (iii) removal of sulfates from the 6-O position of heparan sulfate chains by extracellular sulfatases. Assessing or monitoring the remodeling of HSPGs has important implications for tumor diagnosis and patient prognosis while therapeutic manipulation of the remodeling process represents an exciting new possibility for treating cancer.

Animals↗
PubMed2007

Tumor microenvironment abnormalities: causes, consequences, and strategies to normalize.

A solid tumor is an organ-like entity comprised of neoplastic cells and non-transformed host stromal cells embedded in an extracellular matrix. The expression of various genes is influenced by interactions among these cells, surrounding matrix, and their local physical and biochemical microenvironment. The products encoded by these genes, in turn, control the pathophysiological characteristics of the tumor, and give rise to the abnormal organization, structure, and function of tumor blood vessels. These abnormalities contribute to heterogeneous blood flow, vascular permeability, and microenvironment. Proliferating tumor cells produce solid stress which compresses blood and lymphatic vessels. As a result of vessel leakiness and lack of functional lymphatics, interstitial fluid pressure is significantly elevated in solid tumors. Each of these abnormalities forms a physiological barrier to the delivery of therapeutic agents to tumors. Furthermore, the metabolic microenvironment in tumors such as hypoxia and acidosis hinder the efficacy of anti-tumor treatments such as radiation therapy and chemotherapy. A judicious application of anti-angiogenic therapy has the potential to overcome these problems by normalizing the tumor vessels and making them more efficient for delivery of oxygen and drugs. Combined anti-angiogenic and conventional therapies have shown promise in the clinic.

Animals↗
PubMed2003

Modulation of cell death in the tumor microenvironment.

The microenvironment of solid human tumors is characterized by heterogeneity in oxygenation. Hypoxia arises early in the process of tumor development because rapidly proliferating tumor cells outgrow the capacity of the host vasculature. Formation of solid tumors thus requires coordination of angiogenesis with continued tumor cell proliferation. However, despite such neovascularization, hypoxia is persistent and frequently found in tumors at the time of diagnosis. Tumors with low oxygenation have a poor prognosis, and strong evidence suggests this is because of the effects of hypoxia on malignant progression, angiogenesis, metastasis, and therapy resistance. The presence of viable hypoxic cells is likely a reflection of the development of hypoxia tolerance resulting from modulation of cell death in the microenvironment. This acquired feature has been explained on the basis of clonal selection-the hypoxic microenvironment selects cells capable of surviving in the absence of normal oxygen availability. However, the persistence and frequency of hypoxia in solid tumors raises a second potential explanation. We suggest that stable microregions of hypoxia may play a positive role in tumor growth. Although hypoxia inhibits cell proliferation and in tumor cells will eventually induce cell death, hypoxia also provides angiogenic and metastatic signals. The development of hypoxia tolerance will thus allow prolonged survival in the absence of oxygen and generation of a persistent angiogenic signal. We will discuss the concept of hypoxia tolerance and review mechanisms used by cancer cells to acquire this phenotype. The concept of hypoxia tolerance has important implications for current and future therapeutic approaches. Most therapeutic efforts to combat hypoxia have focused on targeting the presence of hypoxia itself. Our hypothesis predicts that targeting the biological responses to hypoxia and the pathways leading to hypoxia tolerance may also be attractive therapeutic strategies.

Apoptosis↗
PubMed2005

Commutators of PAR-1 signaling in cancer cell invasion reveal an essential role of the Rho-Rho kinase axis and tumor microenvironment.

We recently reported that proteinase-activated receptors type I (PAR-1) are coupled to both negative and positive invasion pathways in colonic and kidney cancer cells cultured on collagen type I gels. Here, we found that treatments with the cell-permeant analog 8-Br-cGMP and the soluble guanylate cyclase activator BAY41-2272, and Rho kinase (ROK) inhibition by Y27632 or a dominant negative form of ROK lead to PAR-1-mediated invasion through differential Rac1 and Cdc42 signaling. Hypoxia or the counteradhesive matricellular protein SPARC/BM-40 (SPARC: secreted protein acidic rich in cysteine) overexpressed during cancer progression also commutated PAR-1 to cellular invasion through the cGMP/protein kinase G (PKG) cascade, RhoA inactivation, and Rac1-dependent or -independent signaling. Cultured primary cancer cells isolated from peritoneal and pleural effusions from patients with colon cancer or other malignant tumors harbored PAR-1, as shown by RT-PCR and FACS analyses. These malignant effusions also contained high levels of activated thrombin and fibrin, and induced a proinvasive response in HCT8/S11 human colorectal cancer cells. Our data underline the essential role of the tumor microenvironment and of several commutators targeting cGMP/PKG signaling and the RhoA-ROK axis in the control of PAR-1 proinvasive activity and metastatic potential of cancer cells in distant organs and peritoneal or pleural cavities. We also add new insights into the mechanisms linking the coagulation mediators thrombin and PAR-1 in the context of blood coagulation disorders and venous thrombosis often observed in cancer patients, as described in 1865 by Armand Trousseau.

Aged↗
PubMed2005

Targeting the local tumor microenvironment with vaccinia virus expressing B7.1 for the treatment of melanoma.

Immunotherapy for the treatment of metastatic melanoma remains a major clinical challenge. The melanoma microenvironment may lead to local T cell tolerance in part through downregulation of costimulatory molecules, such as B7.1 (CD80). We report the results from the first clinical trial, to our knowledge, using a recombinant vaccinia virus expressing B7.1 (rV-B7.1) for monthly intralesional vaccination of accessible melanoma lesions. A standard 2-dose-escalation phase I clinical trial was conducted with 12 patients. The approach was well tolerated with only low-grade fever, myalgias, and fatigue reported and 2 patients experiencing vitiligo. An objective partial response was observed in 1 patient and disease stabilization in 2 patients, 1 of whom is alive without disease 59 months following vaccination. All patients demonstrated an increase in postvaccination antibody and T cell responses against vaccinia virus. Systemic immunity was tested in HLA-A*0201 patients who demonstrated an increased frequency of gp100 and T cells specific to melanoma antigen recognized by T cells 1 (MART-1), also known as Melan-A, by ELISPOT assay following local rV-B7.1 vaccination. Local immunity was evaluated by quantitative real-time RT-PCR, which suggested that tumor regression was associated with increased expression of CD8 and IFN-gamma. The local delivery of vaccinia virus expressing B7.1 was well tolerated and represents an innovative strategy for altering the local tumor microenvironment in patients with melanoma.

Adult↗
PubMed2005

Tumor microenvironment: what can effusions teach us?

Malignant effusions, which are composed of malignant pleural and peritoneal fluid, are an unusual manifestation of cancer and frequently portend a poor prognosis. Neoplastic cells that disseminate into cavities containing effusions are highly metastatic and possess a strong autonomous proliferative drive while concurrently being stimulatory of exudative effusions. Most effusions will respond to transient therapeutic intervention, including the obliteration of potential space via pleurodesis. Cure, however, is rare, thus making effusions a biologically, biochemically, and clinically important topic of study. The local microenvironment that supports malignant growth, invasion, and dissemination of the solid primary tumor into the vasculature is composed of activated stroma that includes scaffolding consisting of materials that promote the tumor function, and vascular structures to provide conduits for travel and nutrient delivery. Less is understood about the tumor-cell microenvironment in malignant effusions. The fluid nature of such a microenvironment when compared with the solid primary tumor may have significant implications for disease dissemination and progression. Dissecting the signaling activity and components of such microenvironments will improve our understanding and ultimately our ability to provide better patient care.

Ascitic Fluid↗
PubMed2002

T cells from the tumor microenvironment of patients with progressive myeloma can generate strong, tumor-specific cytolytic responses to autologous, tumor-loaded dendritic cells.

Most untreated cancer patients develop progressive tumors. We tested the capacity of T lymphocytes from patients with clinically progressive, multiple myeloma to develop killer function against fresh autologous tumor. In this malignancy, it is feasible to reproducibly evaluate freshly isolated tumor cells and T cells from the marrow tumor environment. When we did this with seven consecutive patients, with all clinical stages of disease, we did not detect reactivity to autologous cancer cells. However, both cytolytic and IFN-gamma-producing responses to autologous myeloma were generated in six of seven patients after stimulation ex vivo with dendritic cells that had processed autologous tumor cells. The antitumor effectors recognized fresh autologous tumor but not nontumor cells in the bone marrow, myeloma cell lines, dendritic cells loaded with tumor-derived Ig, or allogeneic tumor. Importantly, these CD8(+) effectors developed with similar efficiency by using T cells from both the blood and the bone marrow tumor environment. Therefore, even in the setting of clinical tumor progression, the tumor bed of myeloma patients contains T cells that can be activated readily by dendritic cells to kill primary autologous tumor.

Bone Marrow Cells↗
PubMed1994

The tumor microenvironment: possible role of integrins and the extracellular matrix in tumor biological behavior of intratubular germ cell neoplasia and testicular seminomas.

In the present study, we examined the distribution of integrin subunits and extracellular matrix proteins in normal testis, intratubular germ cell neoplasia (ITGCN), and primary and metastatic seminomas. Compared to normal testis in ITGCN, Sertoli cells showed increased expression of alpha 3, alpha 6, and beta 1 integrin subunits. Malignant intratubular germ cells stained for alpha 3, alpha 6, and beta 1 integrin subunits. Progression of ITGCN to invasive seminoma was associated with loss of alpha 3 integrin subunit expression by tumor cells. Consequent to this loss, it can be speculated that the strong expression on ITGCN may be related to the noninvasive character of the lesion as is also known from other noninvasive tumors. All tumors showed a strong expression of alpha 6 and beta 1 integrin subunits. The alpha 5 integrin subunit was weakly expressed in primary seminomas in all stages. No differences were observed in integrin expression between primary and metastatic tumors. The distribution of extracellular matrix proteins was heterogeneous and revealed clear architectural differences between seminomas that may reflect different stages of tumor stroma formation. To our knowledge, the results presented in this study provide the first information on the possible role of tumor-extracellular matrix interactions in the biological behavior of ITGCN and testicular seminomas.

Extracellular Matrix Proteins↗
PubMed1996

Implications of acidic tumor microenvironment for neoplastic growth and cancer treatment: a computer analysis.

The acidic microenvironment found in most solid tumors appears to be a main regulator for the self-organized development of neoplastic growth and invasion. Induced by mitogenic stimulation and/or oncogenic alterations in their signal transduction network, tumor cells develop an improved capability for acid extrusion. This clamps intracellular pH to slightly alkaline values permissive for growth and proliferation and provides tumor cells with an enhanced resistance against acidic extracellular conditions. Since rapid tumor cell growth under hypoxic conditions is accompanied by glycolytic metabolism, and consequently, acid production, acid export is further enhanced. Local extracellular acidification is facilitated by microcirculatory inadequacy resulting in both reduced buffering capacity and functional heterogeneity inside the tumor. Significant microenvironmental pH gradients promote tumor cell invasion and inhibit the immune response. The scenario is checked by means of a dynamic computer model. The stochastic minimal model supports the hypothesis that acidification of the microenvironment by malignant cells cannot only be regarded as a supplementary side effect of tumor cell metabolism, but rather as a strategic principle to 'enslave' processes normally counteracting neoplastic growth and invasion. The results are discussed with respect to current concept for cancer treatment.

Animals↗
PubMed2026

Impact of Genomic Mutations on the Transcriptional Pathways and Tumor Microenvironment Landscape of Localized Early Prostate Cancer.

BACKGROUND: The management of intermediate-risk early prostate cancer (PCa) is challenging due to the difficulty in distinguishing indolent from aggressive tumors. This study explores the association between genomic alterations and the tumor and its microenvironment (TME) and implications for disease progression. METHODS: We performed multi-omic profiling in a cohort of 53 localized PCa using targeted sequencing, transcriptional, and proteomic spatial profiling. RESULTS: Somatic mutations and copy number alterations in RB1 (21%), PTEN (18%), and TP53 (9%) were identified. Kaplan-Meier analysis revealed that alterations in the RB and Cell Cycle pathways, particularly aberrations in PTEN, TP53, or RB1, were associated with shorter biochemical recurrence-free survival (p&#x2009;<&#x2009;0.001). Spatial proteomic analysis demonstrated a complex immune landscape in patients with mutations. The tumor compartment demonstrated higher expression of immune checkpoint markers, T-cell activation proteins, and proliferation markers; and a TME that is enriched with CD8&#x2009;+&#x2009;T cells and antigen-presenting cells, but also with immunosuppressive M2 macrophages, suggesting adaptive immune resistance. CONCLUSIONS: Our analysis demonstrates that genomic alterations in PTEN, TP53, or RB1 are not only prognostic for poor outcomes but are also associated with a unique, immunologically complex TME in this Brazilian cohort.

Humans↗
PubMed2026

Multinucleated Giant Cells in Human Pancreatic Cancer Are a Distinct Macrophage Population Undergoing a DNA Damage Response and Associated with an Aggressive Tumor Microenvironment.

Macrophages (M&#x3d5;) constitute a dominant and functionally diverse immune population within the microenvironment of pancreatic ductal adenocarcinoma (PDAC), yet how M&#x3d5; heterogeneity contributes to the tumor remains poorly defined. In an institutional cohort of 145 PDAC specimens, we identified a population of multinucleated giant cells (MGC) of M&#x3d5; origin, an entity previously described in chronic inflammation but rarely in cancer. CD68+ MGCs were present in 28% of tumors, enriched in squamous, nonglandular regions, and more frequent after neoadjuvant chemotherapy. By integrating spatial transcriptomics and quantitative imaging, we defined the features of these cells, which, compared with MGCs in nonneoplastic inflammatory lesions, lacked canonical polarization markers (HLA-DR and CD163) and displayed a distinctive transcriptional program characterized by upregulation of the POLR2K, TUBA8, COX5B, and VDAC1 genes, which encode proteins involved in DNA repair, oxidative stress, and MYC signaling. Spatial analyses revealed activation of hypoxia and extracellular matrix-remodeling pathways in MGC-associated niches, and experimental hypoxia promoted MGC formation in vitro. Consistent with these data, we found that in the The Cancer Genome Atlas (TCGA) Pancreatic Adenocarcinoma (PAAD) dataset a M&#x3d5; MGC gene signature was enriched in the squamous PDAC subtype and correlated with poorer overall survival (P = 0.018). Morphometric and immunofluorescence analyses further showed increased 53BP1+Ki67+ nuclei and nuclear atypia in MGCs, indicating ongoing proliferation despite DNA damage. Together, these data identify MGCs of M&#x3d5; origin as an immune cell state shaped by hypoxia and stress signaling, associated with aggressive tumor phenotypes, and potentially exploitable as an immune classifier in PDAC.

Humans↗
PubMed2004

Thrombospondin-1 associated with tumor microenvironment contributes to low-dose cyclophosphamide-mediated endothelial cell apoptosis and tumor growth suppression.

Low-dose cyclophosphamide (LDC) induces selective apoptosis of endothelial cells within the vascular bed of tumors. Here, we investigated a hypothesis that the effect of LDC is mediated by the pro-apoptotic action of endogenous inhibitors of angiogenesis. Tumors treated with LDC demonstrate similar expression of matrix metalloproteinases and also basement membrane-derived angiogenesis inhibitors when compared with wild-type tumors, whereas the expression of thrombospondin-1 (TSP-1) is significantly elevated in LDC-treated tumors. We used mice with an absence of type XVIII collagen (endostatin) or type IV collagen alpha3 chain (tumstatin) or TSP-1 to assess the contribution of these endogenous inhibitors of angiogenesis on LDC-mediated tumor suppression. Lack of TSP-1 in the host in addition to tumor cells leads to diminished capacity of LDC to suppress tumor growth, whereas the absence of endostatin and tumstatin did not alter the effect of LDC. LDC treatment predominantly induces selective expression of TSP-1 in tumor cells and peri-vascular cells and facilitates apoptosis of proliferating endothelial cells, with minimal direct effect on tumor cells and peri-vascular cells. These studies indicate that TSP-1 contributes to tumor growth suppression induced by LDC and suggest that tumors that express high basal level of TSP-1 may be more susceptible to tumor suppression by such a regimen. This study also makes a strong case for TSP-1 expression levels as a potential predictive marker for the successful use of LDC in cancer patients.

Angiogenesis Inhibitors↗