246 research outputs found
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Role of a Fibronectin-Enriched Extracellular Matrix Niche in Promoting Isolation Stress-Tolerance in Pancreatic Cancer
No full textPancreatic cancer is notoriously known for being aggressive and resistant to chemotherapy. It has one of the highest rates of recurrence among all cancers and a poor survival rate even after treatment. The tumor microenvironment in pancreatic cancer, also known as a “niche”, is characterized by the deposition of a dense extracellular matrix (ECM). To establish a tumor at a primary or metastatic site, tumor-initiating cells (TICs) must adapt and survive in a highly hostile environment characterized by hypoxia, nutrient deprivation, and oxidative stress, together known as isolation stress. TICs accomplish this by gaining stem-like features which ultimately lead to a stress-tolerant phenotype. Pancreatic cancer cells upregulate a receptor called lysophosphatidic acid receptor-4 (LPAR4) in response to isolation stress. LPAR4 expression is necessary and sufficient to establish a tumor-initiating niche, which plays an important role in cancer progression. A characteristic of this niche is the enrichment of the ECM component fibronectin (FN), which interacts with cells through cell-surface integrin receptors. These interactions activate various signaling molecules such as the transcriptional regulator Yes-associated protein (YAP), consequently driving cancer stemness. In this study, I investigate the adaptive gain of a stress-tolerant phenotype in LPAR4- cells mediated by a FN-enriched ECM deposited by LPAR4+ cells. I report that the ectopic expression of LPAR4 in pancreatic cancer cells is sufficient to induce a stress-tolerant phenotype and YAP activation, through the elevated expression of FN. Knockout of FN in LPAR4+ cells can hamper YAP activation, emphasizing the crucial role of FN in YAP signaling. Furthermore, the ECM deposited by LPAR4+ cells is sufficient to confer the stress-tolerant phenotype to neighboring LPAR4- cells through paracrine signaling by a fibronectin-dependent pathway, leading to integrin-mediated activation of YAP and expression of YAP targets CTGF and CYR61. A pure FN-matrix is sufficient to induce YAP activation in LPAR4- cells, indicating that FN is the key ECM component that interacts with cell surface integrin receptors to drive cancer stemness in response to isolation stress. Together, all these factors help tumor-initiating cells to survive isolation stress, resist chemotherapy, and form aggressive tumors, leading to pancreatic cancer progression
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Blocking Fibroblast-Mediated Extracellular Matrix Assembly to Inhibit Pancreatic Cancer Initiation
No full textPancreatic cancer is characterized by an intense fibrotic stroma that is mainly produced by cancer-associated fibroblasts (CAFs). CAFs are a major contributor to the progression of pancreatic cancer, and novel approaches to target their function could have a significant impact on patient outcomes. In this study, we explored how to target two complementary aspects of CAF-mediated pancreatic cancer initiation. First, we investigated an opportunity to impair the ability of CAFs to produce extracellular matrix (ECM) proteins that promote cancer progression. CAFs secrete and assemble ECM proteins, including fibronectin (FN), which serves as a provisional scaffold for the deposition of other ECM proteins. Here, we showed that targeting two primary FN-binding integrins on CAFs, α5β1 and αvβ3, with a bispecific antibody can prevent CAF matrix assembly and their ability to enhance tumor formation. Second, we investigated how to block the paracrine effects of CAFs on pancreatic cancer cells. We showed that CAF-secreted factors induce epithelial-to-mesenchymal transition (EMT) in pancreatic cancer cells and are reduced by inhibition of the TGFβ/SMAD2 pathway. Together, these findings highlight the potential of targeting CAF functions, including matrix assembly and soluble factors-mediated EMT, as strategies to disrupt pancreatic cancer stemness and progression
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Blocking adaptations to stress and inflammation in pancreatic cancer
No full textPancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, with a five-year survival rate under 13%. While nearly all cases harbor activating mutations in KRAS, progression from early lesions to invasive carcinoma depends on additional selective pressures, particularly chronic inflammation and tissue injury, that reprogram epithelial cells toward a stem-like, stress-tolerant state. Understanding how these rare events occur, and how established tumors adapt to environmental and therapeutic stress, is critical for improving early detection and treatment outcomes.Chapter 1 reviews the foundational genetic, epigenetic, and microenvironmental drivers of PDAC, with emphasis on epithelial plasticity, clonal selection, and adaptive signaling through JAK/STAT3. This synthesis highlights key shortcomings of current molecular subtyping frameworks, which capture static tumor features but fail to account for dynamic adaptive states that influence prognosis and therapeutic resistance.Chapter 2 presents original research identifying integrin αvβ3 as a downstream effector of inflammation-driven STAT3 activation. Using preclinical PDAC models, we show that αvβ3 acquisition requires both inflammatory signaling and a permissive chromatin state, enabling stemness, stress tolerance, and tumor initiation. These findings form the basis for the STRESS gene signature, which stratifies tumors by their reliance on STAT3-driven enhancer programs and identifies patients most likely to benefit from STAT3-targeted therapies.Chapter 3 addresses why most KRAS-mutant precursor lesions fail to progress, revealing that inflammation selectively induces αvβ3 in a subset of dedifferentiated epithelial cells to confer survival in non-permissive microenvironments and drive malignant transformation.Together, these studies link inflammation, epigenetic state, and integrin-mediated signaling to PDAC initiation and progression, providing a mechanistic and translational framework for identifying high-risk disease and targeting adaptive programs across disease stages
In vivo measurements of blood flow and glial cell function with two-photon laser scanning microscopy
No full textTwo-photon laser scanning microscopy is an ideal tool for high-resolution fluorescence imaging in intact organs of living animals. With regard to in vivo brain research, this technique provides new opportunities to study hemodynamics in the microvascular system and morphological dynamics and calcium signaling in various glial cell types. These studies benefit from the ongoing developments for in vivo labeling, imaging, and photostimulation. Here, we review recent advances in the application of two-photon microscopy for the study of blood flow and glial cell function in the neocortex. We emphasize the dual role of two-photon imaging as a means to assess function in the normal state as well as a tool to investigate the vascular system and glia under pathological conditions, such as ischemia and microvascular disease. Further, we show how extensions of ultra-fast laser techniques lead to new models of stroke, where individual vessels may be targeted for occlusion with micrometer precision
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Fibronectin-Binding Integrins Alpha-5 Beta-1 and Alpha-v Beta-3 on Cancer-Associated Fibroblasts Block Fibronectin Collagen Matrix Assembly, Tumor Initiation and Tissue Stiffness
No full textPancreatic cancer is characterized by a dense fibrotic stroma, consisting of cancer-associated fibroblasts (CAFs), immune cells, and extracellular matrix (ECM) that promote tumor growth and treatment resistance. CAFs secrete and organize on their surface ECM proteins, including fibronectin (FN) which coordinates the assembly of collagen fibrils that promote matrix stiffness. Since CAFs are a major contributor to fibrosis and the progression of pancreatic cancer, novel approaches to target their function could have a significant impact on patient outcome. This research demonstrates that the ability of pancreatic cancer cells to initiate tumors in mice is greatly enhanced by co-injection of CAFs. Targeting FN via FN-binding integrins α5β1 and αvβ3 that are highly expressed on CAFs disrupts CAF-induced fibrosis, decreases tumor stiffness, and prevents the initiation of pancreas tumors in mice. These results highlight the therapeutic potential of targeting fibronectin-binding integrins, α5β1 and αvβ3, on CAFs to disrupt the fibrotic stroma in pancreatic cancer
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The combined role of stress and lysophosphatidic acid in pancreatic ductal adenocarcinoma progression
No full textPancreatic cancers are notoriously aggressive and drug-resistant, and surgical resection is complicated by widespread intraperitoneal dissemination and ascites. One component of malignant ascites is lysophosphatidic acid (LPA), a bioactive lipid that promotes multiple aspects of tumor progression. Here, I report that expression of the cancer stem cell marker αvβ3 integrin is necessary and sufficient for the production of LPA. In turn, LPA was shown to induce the expression of stem genes OCT4 and NANOG and promote anchorage-independent growth. Upon interrogating the LPA metabolic pathway, I found that expression of αvβ3 integrin is necessary and sufficient to promote the expression of cytoplasmic phospholipase A2 (cPLA2), an important enzyme in the production of LPA. Furthermore, αvβ3 integrin forms a physical complex with cPLA2 to stabilize and stimulate its activity. Subsequently, KRAS mutant pancreatic cancer cells utilize LPA to overcome the effects of cellular stress, including cancer therapy. A variety of stress, including nutrient deprivation, oxidative stress, and treatment with standard-of-care chemotherapies, sensitizes cells to LPA-induced migration as well as KRAS-driven advantages such as macropinocytosis in response to nutrient stress and ROS elimination in response to oxidative stress. In order to cope with these stresses, cancer cells selectively upregulate the expression of LPA Receptor 4 (LPAR4). I illustrate that this receptor is necessary and sufficient for adaptation to stress in vitro and tumor progression in vivo. I showed that LPAR4 is necessary and sufficient to activate the Gαs/cAMP/PKA signaling pathway and that this pathway is required for LPA-mediated protection from stress. This is accomplished through activation of Vasodilator Stimulated Phosphoprotein (VASP), an enzyme involved in actin polymerization. Ultimately, I found that VASP is necessary for stress-mediated and LPAR4-mediate migration and macropinocytosis. My work highlights how stress changes the repertoire of LPA receptors, leading to dependence on LPAR4 by virtue of its stress mitigating functions, such as macropinocytosis and ROS elimination. Furthermore, my findings illustrate that αvβ3 integrin expressing cancer stem-like cells can secrete the bioactive lipid LPA through cPLA2 upregulation. Subsequently, cellular stress drives a more aggressive cancer phenotype by priming pancreatic cells to be highly responsive to LPA
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Superenhancer-activation of KLHDC8A Drives Glioma Ciliation and Hedgehog Signaling
No full textGlioblastoma ranks among the most aggressive and lethal of all human cancers. Self-renewing, highly tumorigenic glioblastoma stem cells (GSCs) contribute to therapeutic resistance and maintain cellular heterogeneity. Here, we interrogated superenhancer landscapes of primary glioblastoma specimens and patient-derived GSCs, revealing a kelch domain-containing gene (KLHDC8A) with a previously unknown function as an epigenetically-driven oncogene. Targeting KLHDC8A decreased GSC proliferation and self-renewal, induced apoptosis, and impaired in vivo tumor growth. Transcription factor control circuitry analyses revealed that the master transcriptional regulator SOX2 stimulated KLHDC8A expression. Mechanistically, KLHDC8A bound Chaperonin-Containing TCP1 (CCT) to promote assembly of primary cilia to activate Hedgehog signaling. KLHDC8A expression correlated with Aurora B/C Kinase inhibitor activity, which induced primary cilia and Hedgehog signaling. Combinatorial targeting of Aurora B/C Kinase and Hedgehog displayed augmented benefit against GSC proliferation. Collectively, superenhancer-based discovery revealed KLHDC8A as a novel molecular target of cancer stem cells that promotes ciliogenesis to activate the Hedgehog pathway, offering insights into therapeutic vulnerabilities for glioblastoma treatment
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A Model For Alpha-1-Acid Glycoprotein-Mediated Immunosuppression In The Metastatic Breast Cancer Patient: Effects On The Lymphoid Cell Surface
No full textLymphoid cells from metastatic breast cancer patients showed a reduced capacity to respond to the mitogen Concanavalin A as compared to lymphoid cells from normal women in the same age group. In an attempt to determine if a serum factor was partially responsible for this anomaly, sera was collected from patients with metastatic breast cancer and tested for its ability to inhibit normal lymphocyte responsiveness. Normal lymphoid cells incubated in patients' sera showed a significant decrease in their Con A, PHA-P, and PWM blastogenic response as compared to the same cells incubated in sera from age and sex-matched normal individuals. Sera from these patients were analyzed for the presence of elevated levels of (alpha)-1-acid glycoprotein (AG), an acute phase reactant which had been shown to nonspecifically suppress various immunological functions. A correlation was established between the level of AG in the serum and its ability to inhibit mitogen induced blast transformation of normal lymphoid cells. To determine if breast cancer serum with elevated AG could perturb normal lymphoid membrane function, Con A capping, studies were performed on normal lymphoid cells pre-treated with serum from a breast cancer patient or normal individual. Con A capping of normal lymphoid cells was inhibited by pre-treatment with breast cancer sera, or normal sera supplemented with AG. Exogenous addition of AG to normal sera was also capable of inhibiting surface immunoglobulin capping on B lymphocytes, as well as Con A capping. With the use of flow cytometric analysis, it was shown that the ability of AG to inhibit the capping of either receptor-ligand complex was not due to an altered capacity of these ligands to bind to the lymphoid cell surface in the presence of elevated AG. The ability of AG to interact with the lipid portion of the membrane was tested with the use of synthetic vesicles composed of phosphatidyl choline. AG was shown to displace 1-anilino-8-naphthalene sulfonate (a fluorescent surface probe) from the polar head region of the phospholipid vesicles. AG was not able to displace N-phenyl-naphthalamine (a fluorescent probe of the membrance interior) from the hydrophobic portion of the synthetic vesicles. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI</p
Abstract 3966: Targeting integrin αvβ3-expressing cancer stem cells to manipulate tumor-associated macrophages
No full textAbstract
Tumor associated macrophages are involved in regulation of cancer growth and aggressiveness. Whereas M1 macrophages trigger an inflammatory response and inhibit tumor growth, M2 macrophages secrete pro-tumor cytokines into the microenvironment to support tumor progression. A macrophage switch from M1 to M2 has been associated with lung cancer progression, and cancer stem cells have been implicated as a driver of this reprogramming.
We recently reported that integrin αvβ3 expression is induced on lung adenocarcinoma cells during drug resistance and is both necessary and sufficient to reprogram these tumors to a stem-like state. Given the role that cancer stem cells play in switching M1 to M2 macrophages, we asked whether αvβ3 expression on lung adenocarcinoma cells account for this macrophage conversion. The M1/M2 macrophage ratio in αvβ3-positive tumors was markedly decreased relative to tumors lacking αvβ3. We next treated mice bearing αvβ3-positive tumors with a monoclonal antibody (LM609) targeting this receptor to assess its ability to alter the macrophage phenotype within these tumors. LM609 was able to selectively eliminate the αvβ3-positive cancer stem cells via antibody-dependent cell-mediated cytotoxicity (ADCC), and this not only increased the M1 macrophage population, but also markedly enhanced the sensitivity of these tumors to the effects of therapy.
These findings reveal that αvβ3-expressing cancer stem cells favor the pro-tumor M2 macrophage phenotype. Eliminating αvβ3-positive cancer stem cells via ADCC serves to both increase pro-inflammatory macrophages within the tumor microenvironment and prolong tumor sensitivity to therapy.
Citation Format: Hiromi I. Wettersten, Toshiyuki Minami, Megan M. Kaneda, Laetitia Seguin, Judith A. Varner, Sara M. Weis, David A. Cheresh. Targeting integrin αvβ3-expressing cancer stem cells to manipulate tumor-associated macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3966. doi:10.1158/1538-7445.AM2017-3966</jats:p
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