The Tumor-Suppressive Role Of Secreted Maspin Via The Exosomes

This dissertation highlights several novel findings. Maspin has been consistently detected in the conditioned media of maspin-expressing cells of normal and tumor breast, prostate and lung origin. Furthermore, extracellular maspin has been demonstrated to have anti-tumor effects. Interestingly, maspin has been reported as cargo of the exosomes, which highlights one of the secretion mechanisms of maspin. Maspin secretion as an exosomal molecule was verified by electron microscopy, atomic force microscopy, light scattering dynamic analysis and immunoblot analysis. The data showed that exosomes derived from the non-malignant cell lines have two distinct populations that do no overlap in their size distributions. Based on the size distribution and the electron microscopy analysis, it is likely that exosomes derived from the non-malignant cells are aggregated exosomes. In contrast, tumor cell-derived exosomes comprised a population of broader size distribution. To understand how secreted maspin may contribute to tumor suppression, it is critical to understand how maspin is regulated at the step of protein trafficking. The data showed that maspin is secreted by dual mechanisms, as free and exosomal protein, respectively. These two mechanisms seem to be independent. While tumor cells are capable of secreting maspin as a free molecule, albeit at a lower level as compared to that by normal epithelial cells, they do not secrete exosomal maspin. Loss of maspin in exosomes from derived non-malignant cells conferred a stimulatory effect on the motility of fibroblasts, suggesting a biological function of exosomal maspin in suppressing the stromal reactivity in the tumor microenvironment. These novel findings highlight a new role for exosomal maspin as a tumor suppressor

Feeling Stress: The Mechanics of Cancer Progression and Aggression

The tumor microenvironment is a dynamic landscape in which the physical and mechanical properties evolve dramatically throughout cancer progression. These changes are driven by enhanced tumor cell contractility and expansion of the growing tumor mass, as well as through alterations to the material properties of the surrounding extracellular matrix (ECM). Consequently, tumor cells are exposed to a number of different mechanical inputs including cell-cell and cell-ECM tension, compression stress, interstitial fluid pressure and shear stress. Oncogenes engage signaling pathways that are activated in response to mechanical stress, thereby reworking the cell's intrinsic response to exogenous mechanical stimuli, enhancing intracellular tension via elevated actomyosin contraction, and influencing ECM stiffness and tissue morphology. In addition to altering their intracellular tension and remodeling the microenvironment, cells actively respond to these mechanical perturbations phenotypically through modification of gene expression. Herein, we present a description of the physical changes that promote tumor progression and aggression, discuss their interrelationship and highlight emerging therapeutic strategies to alleviate the mechanical stresses driving cancer to malignancy

Feeling Stress: The Mechanics of Cancer Progression and Aggression.

The tumor microenvironment is a dynamic landscape in which the physical and mechanical properties evolve dramatically throughout cancer progression. These changes are driven by enhanced tumor cell contractility and expansion of the growing tumor mass, as well as through alterations to the material properties of the surrounding extracellular matrix (ECM). Consequently, tumor cells are exposed to a number of different mechanical inputs including cell-cell and cell-ECM tension, compression stress, interstitial fluid pressure and shear stress. Oncogenes engage signaling pathways that are activated in response to mechanical stress, thereby reworking the cell's intrinsic response to exogenous mechanical stimuli, enhancing intracellular tension via elevated actomyosin contraction, and influencing ECM stiffness and tissue morphology. In addition to altering their intracellular tension and remodeling the microenvironment, cells actively respond to these mechanical perturbations phenotypically through modification of gene expression. Herein, we present a description of the physical changes that promote tumor progression and aggression, discuss their interrelationship and highlight emerging therapeutic strategies to alleviate the mechanical stresses driving cancer to malignancy

New Horizons in Advocacy Engaged Physical Sciences and Oncology Research

To address cancer as a multifaceted adaptive system, the increasing momentum for cross-disciplinary connectivity between cancer biologists, physical scientists, mathematicians, chemists, biomedical engineers, computer scientists, clinicians, and advocates is fueling the emergence of new scientific frontiers, principles, and opportunities within physical sciences and oncology. In parallel to highlighting the advances, challenges, and acceptance of advocates as credible contributors, we offer recommendations for addressing real world hurdles in advancing equitable partnerships among advocacy stakeholders

Feeling Stress: The Mechanics of Cancer Progression and Aggression

The tumor microenvironment is a dynamic landscape in which the physical and mechanical properties evolve dramatically throughout cancer progression. These changes are driven by enhanced tumor cell contractility and expansion of the growing tumor mass, as well as through alterations to the material properties of the surrounding extracellular matrix (ECM). Consequently, tumor cells are exposed to a number of different mechanical inputs including cell–cell and cell-ECM tension, compression stress, interstitial fluid pressure and shear stress. Oncogenes engage signaling pathways that are activated in response to mechanical stress, thereby reworking the cell's intrinsic response to exogenous mechanical stimuli, enhancing intracellular tension via elevated actomyosin contraction, and influencing ECM stiffness and tissue morphology. In addition to altering their intracellular tension and remodeling the microenvironment, cells actively respond to these mechanical perturbations phenotypically through modification of gene expression. Herein, we present a description of the physical changes that promote tumor progression and aggression, discuss their interrelationship and highlight emerging therapeutic strategies to alleviate the mechanical stresses driving cancer to malignancy

A Novel Geranylgeranyl Transferase Inhibitor in Combination with Lovastatin Inhibits Proliferation and Induces Autophagy in STS-26T MPNST CellsS⃞

Prenylation inhibitors have gained increasing attention as potential therapeutics for cancer. Initial work focused on inhibitors of farnesylation, but more recently geranylgeranyl transferase inhibitors (GGTIs) have begun to be evaluated for their potential antitumor activity in vitro and in vivo. In this study, we have developed a nonpeptidomimetic GGTI, termed GGTI-2Z [(5-nitrofuran-2-yl)methyl-(2Z,6E,10E)-3,7,11,15-tetramethylhexadeca-2,6,10,14-tetraenyl 4-chlorobutyl(methyl)phosphoramidate], which in combination with lovastatin inhibits geranylgeranyl transferase I (GGTase I) and GGTase II/RabGGTase, without affecting farnesylation. The combination treatment results in a G0/G1 arrest and synergistic inhibition of proliferation of cultured STS-26T malignant peripheral nerve sheath tumor cells. We also show that the antiproliferative activity of drugs in combination occurs in the context of autophagy. The combination treatment also induces autophagy in the MCF10.DCIS model of human breast ductal carcinoma in situ and in 1c1c7 murine hepatoma cells, where it also reduces proliferation. At the same time, there is no detectable toxicity in normal immortalized Schwann cells. These studies establish GGTI-2Z as a novel geranylgeranyl pyrophosphate derivative that may work through a new mechanism involving the induction of autophagy and, in combination with lovastatin, may serve as a valuable paradigm for developing more effective strategies in this class of antitumor therapeutics

Identification of an Intrinsic Determinant Critical for Maspin Subcellular Localization and Function

<div><p>Maspin, a multifaceted tumor suppressor, belongs to the serine protease inhibitor superfamily, but only inhibits serine protease-like enzymes such as histone deacetylase 1 (HDAC1). Maspin is specifically expressed in epithelial cells and it is differentially regulated during tumor progression. A new emerging consensus suggests that a shift in maspin subcellular localization from the nucleus to the cytoplasm stratifies with poor cancer prognosis. In the current study, we employed a rational mutagenesis approach and showed that maspin reactive center loop (RCL) and its neighboring sequence are critical for maspin stability. Further, when expressed in multiple tumor cell lines, single point mutation of Aspartate³⁴⁶ (D³⁴⁶) to Glutamate (E³⁴⁶), maspin^D346E, was predominantly nuclear, whereas wild type maspin (maspin^WT) was both cytoplasmic and nuclear. Evidence from cellular fractionation followed by immunological and proteomic protein identification, combined with the evidence from fluorescent imaging of endogenous proteins, fluorescent protein fusion constructs, as well as bimolecular fluorescence complementation (BiFC) showed that the increased nuclear enrichment of maspin^D346E was, at least in part, due to its increased affinity to HDAC1. Maspin^D346E was also more potent than maspin^WT as an HDAC inhibitor. Taken together, our evidence demonstrates that D³⁴⁶ is a critical <i>cis</i>-element in maspin sequence that determines the molecular context and subcellular localization of maspin. A mechanistic model derived from our evidence suggests a new window of opportunity for the development of maspin-based biologically competent HDAC inhibitors for cancer treatment.</p></div

Maspin nuclear localization correlates with increased histone acetylation and release of HDAC-repressed gene expression.

<p>(<b>A</b>) Western blot of recombinant maspin, HDAC1, and HDAC1 target protein (acetylated Histone 3 at Lysine 9 (H3 Acetyl K⁹)) in DU145 cells. GAPDH was used as a loading control. (<b>B</b>) Q-RT-PCR of HDAC1 targeted genes differentially regulated by maspin. The threshold cycle (ct) numbers obtained from qRT-PCR were normalized by the internal GAPDH controls and presented as the fold change. Maspin^WT: black bar; maspin^D346E: white bar.</p