45 research outputs found
Physical Aspects of Cancer Invasion
Invasiveness, one of the hallmarks of tumor progression, represents the
tumor's ability to expand into the host tissue by means of several complex
biochemical and biomechanical processes. Since certain aspects of the problem
present a striking resemblance with well known physical mechanisms, such as the
mechanical insertion of a solid inclusion in an elastic material specimen [1,
2] or a water drop impinging on a surface [3], we propose here an analogy
between these physical processes and a cancer system's invasive branching into
the surrounding tissue. Accounting for its solid and viscous properties, we
present a unifying concept that the tumor behaves as a granular solid. While
our model has been explicitly formulated for multicellular tumor spheroids in
vitro, it should also contribute to a better understanding of tumor invasion in
vivo.Comment: 20 pages, 2 figure
Remodeling of extracellular matrix by normal and tumor-associated fibroblasts promotes cervical cancer progression
Background:
Comparison of tissue microarray results of 29 cervical cancer and 27 normal cervix tissue samples
using immunohistochemistry revealed considerable reorganization of the fibrillar stroma of these tumors.
Preliminary densitometry analysis of laminin-1,
α
-smooth muscle actin (SMA) and fibronectin immunostaining
demonstrated 3.8-fold upregulation of laminin-1 and 5.2-fold increase of SMA in the interstitial stroma, indicating
that these proteins and the activated fibroblasts play important role in the pathogenesis of cervical cancer. In the
present work we investigated the role of normal and tumor-associated fibroblasts.
Methods:
In vitro
models were used to throw light on the multifactorial process of tumor-stroma interaction, by
means of studying the cooperation between tumor cells and fibroblasts. Fibroblasts from normal cervix and cervical
cancers were grown either separately or in co-culture with CSCC7 cervical cancer cell line. Changes manifest in
secreted glycoproteins, integrins and matrix metallo-proteases (MMPs) were explored.
Results:
While normal fibroblasts produced components of interstitial matrix and TGF-
β
1 that promoted cell
proliferation, cancer-associated fibroblasts (CAFs) synthesized ample amounts of laminin-1. The following results
support the significance of laminin-1 in the invasion of CSCC7 cells: 1.) Tumor-associated fibroblasts produced more
laminin-1 and less components of fibrillar ECM than normal cells; 2.) The production of laminin chains was further
increased when CSCC7 cells were grown in co-culture with fibroblasts; 3.) CSCC7 cells were capable of increasing
their laminin production; 4.) Tumor cells predominantly expressed integrin
α
6
β
4 laminin receptors and migrated
towards laminin. The integrin profile of both normal and tumor-associated fibroblasts was similar, expressing receptors
for fibronectin, vitronectin and osteopontin. MMP-7 secreted by CSCC7 cells was upregulated by the presence of
normal fibroblasts, whereas MMP-2 produced mainly by fibroblasts was activated in the presence of CSCC7 cells.
Conclusions:
Our results indicate that in addition to degradation of the basement membrane, invasion of cervical
cancer is accomplished by the remodeling of the interstitial stroma, which process includes decrease and partial replacement of fibronectin and collagens by a laminin-rich matrix
H-Ras Expression in Immortalized Keratinocytes Produces an Invasive Epithelium in Cultured Skin Equivalents
Ras proteins affect both proliferation and expression of collagen-degrading enzymes, two important processes in cancer progression. Normal skin architecture is dependent both on the coordinated proliferation and stratification of keratinocytes, as well as the maintenance of a collagen-rich basement membrane. In the present studies we sought to determine whether expression of H-ras in skin keratinocytes would affect these parameters during the establishment and maintenance of an in vitro skin equivalent.Previously described cdk4 and hTERT immortalized foreskin keratinocytes were engineered to express ectopically introduced H-ras. Skin equivalents, composed of normal fibroblast-contracted collagen gels overlaid with keratinocytes (immortal or immortal expressing H-ras), were prepared and incubated for 3 weeks. Harvested tissues were processed and sectioned for histology and antibody staining. Antigens specific to differentiation (involucrin, keratin-14, p63), basement-membrane formation (collagen IV, laminin-5), and epithelial to mesenchymal transition (EMT; e-cadherin, vimentin) were studied. Results showed that H-ras keratinocytes produced an invasive, disorganized epithelium most apparent in the lower strata while immortalized keratinocytes fully stratified without invasive properties. The superficial strata retained morphologically normal characteristics. Vimentin and p63 co-localization increased with H-ras overexpression, similar to basal wound-healing keratinocytes. In contrast, the cdk4 and hTERT immortalized keratinocytes differentiated similarly to normal unimmortalized keratinocytes.The use of isogenic derivatives of stable immortalized keratinocytes with specified genetic alterations may be helpful in developing more robust in vitro models of cancer progression
Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential
OBJECTIVE: The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems. MATERIAL AND METHODS: The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF). RESULTS: Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified. CONCLUSION: Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies
Protein-Profiling stratifizierter Epithelien mittels Bildverarbeitung histologischer Serienschnitte
The geometric organization of the extracellular matrix in the control of integrin-mediated adhesion and cell function in osteoblasts of the alveolar bone
Cell-extracellular matrix (ECM) interactions play a central role in tissue architecture and turnover. Particularly, integrin-mediated cell adhesion participates in biochemical and physical signals. The aim of this study is to investigate the importance of ECM organization for alveolar bone osteoblasts adhesion and to determine the effects on cell functions such as collagen and fibronectin production. By applying new concepts from the nanotechnology to biological systems, we have developed materials decorated with nano-patterns of peptides of the ECM arranged at a distance of 58 or 73 nm. On these surfaces, human osteoblasts from alveolar bone were cultured for 1-96 hr and examined by video and fluorescence microscopy. Protein quantification by western blotting and gene expression by RT-PCR were also performed. Good cell adhesion and spreading was observed on the 58 nm pattern after 30 min, while weak adhesion and increased motility was evident in osteoblasts on the 73 nm pattern, leading to alteration of cell shape and reduction of cell area after 24 hr. Moreover, cells on the 73 nm did not form focal adhesions and failed to organize the cytoskeleton. After 96 hr in culture, osteoblasts on the 73 nm retained intracellular collagen and produced a disorganized fibronectin network. Osteoblast adhesion and intra-and extra-cellular molecules reorganization are regulated not only by the composition but also by the structure of the extracellular environment. Our novel in vitro system makes it possible to elucidate some of the mechanisms necessary for the maintenance of tissue architecture and mechanical strength, as well as for the design of artificial materials for future clinical applications