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Biomedical subjects

A T Horowitz

Publications and source records attributed to A T Horowitz.

10 recordsLinked to original sources
PubMed1992

In vitro cytotoxicity of liposome-encapsulated doxorubicin: dependence on liposome composition and drug release.

We have investigated the in vitro cytotoxicity of free doxorubicin (DOX) and liposome-entrapped DOX (L-DOX) against a human ovarian carcinoma cell line (OV-1063) using a colorimetric assay. DOX was encapsulated in the inner water phase of liposomes by an ammonium sulfate-generated proton gradient. Liposomes varied in phospholipid composition but were of a similar size. It was found that the cytotoxic activity of L-DOX is substantially decreased when liposomes containing phospholipids of high phase-transition temperature (Tm) are used. The type of negatively charged headgroup did not have any significant influence on the cytotoxicity observed. Experiments using resin beads that bind free and protein-bound DOX, but do not interact with L-DOX, indicated that the cytotoxic effect is mediated by the release of drug from the liposomes into the extracellular medium; no evidence was found for direct cellular uptake of liposome-encapsulated drug. The use of the ionophore nigericin to induce the release of DOX from high-Tm liposomes increased cytotoxicity to a level comparable to free DOX, suggesting that 'remote release' techniques may substantially improve the efficiency of liposome-mediated drug delivery and allow for the full exploitation of the favorable pharmacokinetic properties of specific high-Tm formulations.

Cell Division↗
PubMed1990

Maintenance on extracellular matrix and expression of heparanase activity by human ovarian carcinoma cells from biopsy specimens.

A routine procedure has been developed for the isolation and maintenance in culture of human ovarian carcinoma cells derived from biopsy specimens. Cell attachment, plating efficiency and initial outgrowth were greatly improved by seeding the cells on a basement-membrane-like extracellular matrix (ECM) deposited by cultured corneal endothelial cells. These effects were most significant in serum-free conditions which markedly reduced the rate of cell attachment and growth on regular tissue culture plastic. In 60-80% of the cases and regardless of the patient's age, cells cultured on ECM in the absence of serum divided actively and formed a tightly packed epithelial cell monolayer. Fibroblast overgrowth and cell detachment often occurred on ECM in the presence of serum. Incubation of the human ovarian carcinoma cells with sulfate-labelled ECM, resulted in the release of heparan sulfate degradation fragments, 4- to 7-fold smaller than intact heparan sulfate side chains. This degradation was brought about by endoglycosidase (heparanase) activity expressed to a higher extent by cells that were first maintained in primary cultures as compared with cell aggregates taken directly from the biopsy specimen. In most cases, cells derived from metastatic tumors expressed a higher heparanase activity than cells from the primary ovarian tumor. This result corroborates previous studies, performed with cell lines, on the possible involvement of heparanase in tumor cell invasion and metastasis.

Autoradiography↗
PubMed1989

Oncogenous osteomalacia: a case study.

A case of oncogenous osteomalacia due to a fibrosarcoma of the maxilla is reported, with a 19 year course before treatment. Metabolic studies of calcium and phosphorus were performed 3 and 19 years after the first symptomology. There was a negative balance for both phosphorus and calcium with low serum levels of 1,25-dihydroxyvitamin D which were corrected by resection of the tumor. Portions of the tumor were cultured and the supernatant did not affect phosphorus transport by a proximal tubule kidney cell line. Other portions were injected into athymic nude mice where they resulted in hypophosphatemia and phosphaturia, thus confirming the endocrine nature of the oncogenous osteomalacia factor.

Adult↗
PubMed1987

Prevention of human bladder tumor cell implantation in an in vitro assay.

The high recurrence rate of bladder tumors can be reduced by prevention of tumor cell reimplantation on denuded urothelium following transurethral resection. This can be achieved by intravesical chemotherapy immediately after the resection of the bladder tumors. We have demonstrated, in an in-vitro system, the process of human bladder tumor cell implantation on a naturally produced extracellular matrix (ECM) which simulates the exposed bladder basement membrane and submucosa. Using this model we examined the efficacy of various cytotoxic agents in preventing tumor cell adhesion to the ECM. Human bladder tumor cell implantation was prevented following exposure of the cells to distilled water, epodyl or mitomycin C, and significantly reduced following one hour incubation in cisplatinum and doxorubicin. The maximal effect for each of these cytotoxic agents was reached within 30 to 60 minutes of treatment. Mitomycin C reached maximal effect within 10 minutes. In contrast, thiotepa did not cause a significant reduction in cell adherence to ECM as compared to untreated control cells.

Antineoplastic Agents↗
PubMed1986

Growth of human mammary carcinoma cells from biopsy specimens in serum-free medium on extracellular matrix.

A method developed for the initiation and maintenance in primary culture of human normal mammary epithelial cells was adopted for the growth of epithelial cells from 45 primary human breast tumors. The cells were grown on a naturally produced extracellular matrix (ECM) or on regular tissue culture plastic in a serum-free medium containing growth supplements and high-density lipoprotein (HDL). Successful enzymatic dissociation of the tumor biopsy into organoid structures and cell aggregates was crucial for subsequent cell attachment and growth. Fifty-five percent of the biopsy specimens were successfully dissociated and 87% of these gave rise to actively dividing epithelial cells forming monolayer cultures. In contrast, only 21% of the biopsies which were not optimally dissociated yielded growing cultures. Variations in sample size, duration of enzymatic digestion, and tumor composition affected the outcome of tumor dissociation. Omission of serum from the culture medium prevented the growth of fibroblasts, while plating on ECM greatly improved and in some cases was essential for cell attachment and subsequent outgrowth. The epithelial nature of the cells was verified by their cuboidal and closely apposed morphology and positive staining with antikeratin antibodies. The growth and subculture requirements and the expression of the B38.1 tumor marker were compared in human mammary epithelial cells derived from solid tumors, pleural effusion and normal breast tissue.

Antibodies, Neoplasm↗
PubMed1986

The mechanism of human bladder tumor implantation in an in vitro model.

Implantation of tumor cells in the bladder following transurethral resection of superficial bladder tumors is believed to be one factor in the etiology of bladder tumor recurrences. Using an in vitro model system we have studied the initial interaction between bladder carcinoma cells and a naturally produced basement membrane-like substrate. Minced explants of superficial low grade human bladder tumors from 10 patients were plated into culture dishes coated with a naturally produced extracellular matrix (ECM). This ECM has been shown to resemble the human urothelial basement membrane and submucosa in its macromolecular composition and ultrastructural appearance. It was found that a firm attachment of the human bladder tumor cells occurred within one hour, reached a maximal value within 24 hours and was followed by flattening and proliferation of the plated cells. These results indicate that prevention of tumor implantation should be initiated in the first hour after transurethral resection of the bladder tumors. This assay can be used for the investigation of various treatments to prevent tumor implantation.

Basement Membrane↗
PubMed1986

Immunofluorescent characterization of fibronectin, laminin, and keratin in normal and neoplastic human mammary epithelial cells in culture and in breast tissue sections.

Employing indirect immunofluorescent staining, primary and secondary serum-free cultures and frozen sections of human mammary tissue, normal and neoplastic, were examined for the presence and distribution of fibronectin (FN) and keratin, and frozen sections also for laminin (LM). The epithelial cell purity of the cultures was confirmed by the observation that all cells stained with anti-keratin antibody. In confluent cultures, FN was absent at the apical cell surface, and was seen as a fibrillar matrix exclusively beneath the epithelial monolayer, at the cell-substratum interface. No differences were noted between normal and neoplastic cells in vitro. In sections of normal breast tissue, FN was localized in the basement membrane zone (BMZ) and in the connective tissue stroma. A distinguishing feature of the neoplastic tissue was the considerably more intensive anti-FN immunofluorescence of the stroma. In normal tissue sections, LM was present exclusively in the BMZ, where it formed a continuous, well-delineated, smooth line; this line was found to be distorted, interrupted, and sometimes entirely absent in the neoplastic tissue. The cytoplasm of all cultured cells, neoplastic as well as normal, exhibited a dense network of keratin filaments that was especially prominent around the nucleus. In the sections, keratin was ubiquitously present in the epithelial cells, predominantly along the interior border of the surface membrane; in the neoplastic tissue, this pattern was markedly disorganized, and some of the cells failed to express the substance.

Breast↗
PubMed1985

A new human ovarian carcinoma cell line: establishment and analysis of tumor-associated markers.

In the present study we describe the establishment and characteristics of a new human tumor cell line (OV-1063) positive for carcinoembryonic antigen (CEA) originating from ovarian metastatic tumor cells. Analysis of the cultured cells during their in vitro adaptation period revealed while the primary culture exhibited a low proportion of CEA-positive cells, this proportion increased with culture passages and eventually more than 90% of the cells in the established line were CEA-positive. Thus, during the period of adaptation to in vitro growth, a selection for CEA-positive cells took place but the amount of CEA secreted per each positive cell seemed to be constant. Several tumor-associated characteristics were found positive on the established OV-1063 cell line. The in vitro growing cell line exhibited an abnormal chromosome pattern with a near-trisomy karyotype for some chromosomes, colony formation in soft agar as well as positive staining with a monoclonal antibody B38.1. Culture supernatants of the OV-1063 cells contained significant amounts of CEA as well as CA-125 antigen which is an ovarian-carcinoma-associated antigen.

Agar↗
PubMedDate not supplied

Involvement of heparanase in tumor metastasis and angiogenesis.

The capacity of various blood-borne cells, whether normal or malignant, to extravasate was found to correlate with heparanase-mediated degradation of HS in subendothelial ECM. This degradation was stimulated by proteases or plasminogen and inhibited by native heparin and by various modified nonanticoagulant species of heparin. These heparins also induced a marked reduction in tumor cell metastasis and autoimmune diseases in experimental animals. Heparanase-mediated degradation of HS in ECM also released EC growth factors that are stored in ECM, most likely by high affinity binding to HS. Such growth factors were extracted from subendothelial ECM synthesized in vitro and from basement membranes of the cornea in vivo, and are structurally and functionally related to bFGF;bFGF binds to ECM and is readily released by incubation with either HS, heparin or low MW heparin fragments as well as by various normal and malignant cells and by heparanase-mediated degradation of ECM HS. In contrast, there was little or no release of growth-promoting activity upon incubation of ECM with hyaluronic acid, chondroitin sulfate or chondroitinase ABC. A model is proposed suggesting that regulation of capillary growth and neovascular response may result from displacement of an angiogenic protein (bFGF) from its storage sites within basement membranes.

Extracellular Matrix↗