Radiotoxicity of bismuth-213 bound to membranes of monolayer and spheroid cultures of tumor cells.

Monoclonal antibody 13A to murine CD44 was used to bind the alpha-particle emitter 213Bi to cell surfaces of cultured EMT-6 or Line 1 tumor cells. Data on kinetics and saturation of binding, cell shape and nuclear size were used to calculate the absorbed dose to the nuclei. Treatment of monolayer cells with [213Bi]MAb 13A produced a classical exponential survival curve with no apparent shoulder.

Receptor recognition by histidine 16 of human epidermal growth factor via hydrogen-bond donor/acceptor interactions.

Human epidermal growth factor (hEGF) and human transforming growth factor alpha (hTGFalpha) are prototypical of structurally related polypeptide mitogens which interact with the epidermal growth factor receptor (EGFR). Several determinants of receptor recognition that specify function have been proposed on the basis of structural criteria. This study evaluates the role of one such candidate, H16 of hEGF, by site-specific mutagenesis.

Multiple changes in gene expression are associated with normal cell-induced modulation of the neoplastic phenotype.

Specific regulatory pathways in neoplastic cells seem to be responsive to control signals provided by the normal cell/tissue environment. The present experiments were designed to define, at the molecular level, the growth-regulatory signals in neoplastic cells that are associated with the modulation of expression of the neoplastic phenotype by normal cell populations. When cultured in the presence of normal cell-conditioned medium, a highly malignant rat tracheal carcinoma-derived cell population (IC-12) undergoes dramatic changes in morphology, and the anchorage-independent growth of these cells is inhibited.

Emergence of undifferentiated rat tracheal cell carcinomas, but not squamous cell carcinomas, is associated with a loss of expression of E-cadherin and of gap junction communication.

A series of cells representing normal, non-tumorigenic cell lines, as well as differentiating neoplastic and undifferentiated neoplastic rat tracheal epithelial cell populations were evaluated for their ability to establish homologous and/or heterologous cell-cell gap junction communication in culture. Gap junction communication was evaluated by flow cytometric quantitation of the transfer of the fluorescent dye calcein from a donor to a recipient cell population via gap junctions. The data indicate that normal primary cultures of rat tracheal epithelial cells, as well as non-tumorigenic cell lines and squamous cell carcinomas cell populations, retain the ability to establish both homologous and heterologous gap junction communication.

Influence of cell position relative to planar alpha-particle sources on survival and preneoplastic transformation of primary rat tracheal epithelial cells.

Rat tracheal epithelial cells exposed directly on planar 210Po sources exhibited exponential cell killing; however, no significant increase in induction of preneoplastic transformation was observed over a range of alpha-particle fluences (0.017-0.050 micron-2).

Effects of radiation on rat respiratory epithelial cells: critical target cell populations and the importance of cell-cell interactions.

The oncongenic effects of radiation on rat respiratory tissues are modulated in vivo within the intact tissue. The degree of modulation as well as the mechanism whereby modulation occurs appears to be different for different types of ionizing radiations. A combined cell culture -in vivo model is described.

Effects of 210Po alpha particles on survival and preneoplastic transformation of primary rat tracheal epithelial cells irradiated while in suspension or in the intact tissue.

Rat tracheal epithelial cells exhibited exponential cell killing when exposed to 210Po alpha particles as single cell suspensions or in the intact tissue. Survival of cells in the intact tissue was not significantly different from that observed with cell suspensions. Comparison of survival of cells exposed in suspension to 300 kVpX rays yielded an RBE of 6.

Factors regulating the emergence of spontaneous and X-ray-induced variants in primary rat tracheal epithelial cell cultures.

A series of experiments have been carried out to identify those factors that affect the number of altered populations detected in control, nonexposed, and radiation-exposed primary cultures of rat tracheal epithelial cells. The number of colony forming cells per milliliter of culture medium and the frequency with which the culture medium is changed seemed to be the most critical factors regulating the emergence of induced and spontaneous variants. Increasing the number of cells plated so that of colony forming cells increase from 25 to 200 per ml, regardless of the dish size used, was associated with a 200-fold decline in the frequency of spontaneous variants and a 40-fold decline in X-ray-induced variants.

Characteristics of magnetically separated rat tracheal epithelial cell populations.

A simple magnetic separation technique has been developed using lectins specific for two of the cell types found in the tracheal mucosa. The resulting populations of basal and secretory cells were examined for proliferative capacity in culture and in vivo. The basal cell fraction contains the cells that proliferate in culture and respond to 12-O-tetradecanoylphorbol-13-acetate.

Basal cells are the progenitors of primary tracheal epithelial cell cultures.

The goal of this study was to identify the cells from the rat tracheal epithelium which attach and proliferate in primary culture. When cells isolated from tracheas by enzymatic digestion were held in suspension at 37 degrees C for several hours most of the differentiated cells died. The kinetics of this selective cell death were not dependent on the constituents of the holding medium.

Interactions between cell populations influence expression of the transformed phenotype in irradiated rat tracheal epithelial cells.

A combined in vivo-in vitro model has been utilized to evaluate the influence of cell-cell interactions on expression of radiation-induced transformation in irradiated rat tracheal epithelial cells. Two types of cell interactions are evaluated. One type of interaction appears to involve direct cell-cell contact as occurs within the intact tissue.

Induction of preneoplastic alterations by X rays and neutrons in exposed rat tracheas and isolated tracheal epithelial cells.

The relative potential of high- and low-LET radiation to induce preneoplastic alterations in rat tracheal epithelial cells was evaluated using a combined in vivo-cell culture model. The capacity of X rays and high- and low-dose-rate neutrons to induce preneoplastic changes in isolated rat tracheal epithelial cells and in the intact tissue was compared. The presence of altered populations was determined in culture in terms of the frequency of tracheal epithelial cell populations which exhibit enhanced growth capacity in culture and in terms of the induction of persistent morphological alterations in exposed transplanted tracheas.

Inhibitor production by normal rat tracheal epithelial cells influences the frequency of spontaneous and X-ray-induced enhanced growth variants.

A cell culture model was used to assay for the induction of cell populations with enhanced growth capacity in culture in irradiated normal rat tracheal epithelial cells (NTEC). When cultures were maintained in minimally enriched Ham's F-12 plus 5% fetal bovine serum, it was noted that increasing the seeding density from 1 to 100 colony forming units per 60 mm dish decreased the frequency of proliferating epithelial foci (PEF) scored 5-6 weeks after seeding, from 2.5 to 0.

Changes in response to, and production of, transforming growth factor type beta during neoplastic progression in cultured rat tracheal epithelial cells.

As rat tracheal epithelial cells progress from a normal to a neoplastic phenotype there are systematic changes in their ability to produce and activate latent transforming growth factor type beta (TGF-beta) as well as systematic changes in their response to this growth factor. Using a TGF-beta radioreceptor binding competition assay it was found that normal proliferating rat tracheal cells in early primary culture produced latent TGF-beta. With the emergence of terminally differentiated cell populations active TGF-beta was also detected in the conditioned medium.

Inhibition of carcinogen-altered rat tracheal epithelial cell proliferation by normal epithelial cells in vivo.

The experiments described investigate the potential influence of surrounding normal tracheal epithelial cells on the survival and growth of carcinogen-exposed epithelial cells in tracheal mucosa reconstructed from known cell mixtures. Cell mixtures containing preneoplastic or neoplastic rat tracheal epithelial cells and a small fraction of normal tracheal or esophageal epithelial cells were inoculated into the lumen of previously frozen-thawed tracheas which were then transplanted s.c.

Analysis of differentiation antigens on normal and carcinogen-altered rat epithelial cells in vivo and in culture.

Two murine monoclonal antibodies, 3BG8 and 9BG8, which were raised against a rat tracheal squamous-cell-carcinoma cell line, recognize cell-surface antigens on normal rat squamous epithelium (skin, esophagus, vagina, and cornea) as well as on carcinogen-exposed, immortalized, rat tracheal epithelial cells. Monoclonal antibody 3BG8 binds to a 115-kilodalton cell-surface protein on undifferentiated basal cells of the epithelium, while the binding of the other antibody, 9BG8, occurs in both differentiated and undifferentiated populations of normal squamous epithelium and squamous cell carcinomas. Undifferentiated tracheal carcinomas bound only the 3BG8 antibody.

Inhibition of carcinogen-altered rat tracheal epithelial cells by normal epithelial cell-conditioned medium.

There is mounting evidence that normal cells can either inhibit the growth of carcinogen-altered cells and/or affect progression to a neoplastic phenotype. This effect(s) has been observed both in vivo in intact rat tracheal tissues and in rat tracheal epithelial cell cultures. The inhibition of carcinogen-altered cells in culture appears to be associated with the production of an acid and heat stable, dithiothreitol sensitive, nondialyzable protein produced by normal tracheal epithelial cells or esophageal epithelial cells in primary culture.