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Biomedical subjects

L B Chen

Publications and source records attributed to L B Chen.

At least 127 records · Page 7Linked to original sources
PubMed1987

Dequalinium, a topical antimicrobial agent, displays anticarcinoma activity based on selective mitochondrial accumulation.

Positively charged lipophilic compounds, such as rhodamine 123, localize in mitochondria and are selectively accumulated and retained by carcinoma cells. It has been suggested that this phenotype may be exploited for selective killing of carcinoma cells by lipophilic cations. Here we report that doubly positively charged dequalinium, which has been used for 30 years as an antimicrobial agent in over-the-counter mouthwashes, lozenges, ointments, and paints, exhibits significant anticarcinoma activity. Dequalinium is more effective than seven of eight established anticancer drugs in prolonging the survival of mice with intraperitoneally implanted mouse bladder carcinoma MB49. Dequalinium also inhibits the growth of subcutaneously implanted human colon carcinoma CX-1 in nude mice and recurrent rat colon carcinoma W163 in rats. Lipophilic cationic compounds, such as dequalinium, could comprise a unique class of anticarcinoma agents.

Animals↗
PubMed1986

Characterization of a new monoclonal antibody to a cell surface antigen on colorectal cancer and fetal gut tissues.

Murine hybridoma were raised against the human colon carcinoma cell line CL-187. One clone was found to secrete a monoclonal antibody (ND-1) that recognizes a large external antigen (LEA) on human colon carcinoma cells. With indirect immunofluorescence on formaldehyde-fixed cells, more than 90% of the human colorectal carcinoma cell lines tested expressed LEA. Almost all of the 46 human noncolorectal and nonhuman cell lines tested did not express LEA, including cancer cell lines from other endodermally derived tissues. Staining of frozen sections from human colorectal tumors, noncolorectal tumors, normal adult, and normal fetal tissues showed expression of the antigen on colorectal cancer tissue, fetal colon, and fetal biliary epithelium. LEA can also be detected in the serum and ascites of colorectal cancer patients. Double indirect immunofluorescence with rabbit anti-carcinoembryonic antigen (CEA) antibody and ND-1 monoclonal antibody on a human colorectal carcinoma cell line showed that LEA is distinct from CEA. Physicochemical analysis of LEA showed that it has a large molecular weight, is resistant to extraction from the cell surface, and that sialic acid is an important component of the antigenic site. Because of the specificity for colorectal cancer tissue along with certain biochemical properties, LEA appears to be unique when compared with other tumor-associated antigens. Further research is needed to define the clinical usefulness of LEA in either the diagnosis or treatment of colorectal carcinoma.

Animals↗
PubMed1986

Increased expression of the epidermal growth factor receptor on human colon carcinoma cells.

Epidermal growth factor (EGF) is a small polypeptide hormone that promotes the growth of cells in culture and elicits the differentiation of epithelial tissues in vivo. The effect of EGF is mediated by a transmembrane receptor that is expressed in increased amounts on some tumor cells. We have used a monoclonal antibody to the EGF receptor to detect increased expression of the receptor on human colon carcinoma cells. All eight of the moderately well-differentiated colon carcinoma cell lines tested and several frozen colon carcinoma tissue sections showed increased expression of the EGF receptor, while five poorly differentiated colon carcinoma cell lines and normal colon tissue sections did not. Increased expression of the EGF receptor on moderately well-differentiated colon carcinoma cells but not on poorly differentiated colon carcinoma cells was also demonstrated by western transfer and iodine 125-labeled EGF binding assays. Increased expression of the EGF receptor on moderately well-differentiated colon carcinoma cells seems to be a useful marker for the differentiation of human colon carcinoma cells. In addition, it might provide a site for adjuvant hormonal therapy or immunotherapy.

Antibodies, Monoclonal↗
PubMed1986

Inhibition of rat colon tumor isograft growth with dequalinium chloride.

In searching for a new approach to the systemic treatment of colorectal carcinoma, we have observed that certain lipophilic cationic compounds are accumulated and retained for a significantly longer period in the mitochondria of living carcinoma cells than in normal cells or sarcoma cells. We report the in vivo therapeutic effect of one of these compounds, dequalinium chloride, on the W163 rat colon carcinoma isograft, which grows rapidly in Wistar/Furth rats after primary tumor implantation, and which recurs rapidly after primary tumor resection. In the primary transplant model, tumors were implanted, and daily dequalinium chloride treatments were begun the following day in doses ranging from 1 to 10 mg/kg. In the recurrence model, isografts were implanted, allowed to grow for one week, and then all gross tumor was resected. Dequalinium chloride was administered in varying daily doses starting the day after resection. In both models, tumor was removed on day 11 after implantation or resection. At sublethal doses, dequalinium chloride significantly inhibited primary tumor growth to 60% that of controls and recurrent tumor growth to 50% that of controls. We propose that this unique biologic approach of targeting carcinoma mitochondria with lipophilic cationic compounds may provide a major new opportunity for treating colorectal carcinoma.

Animals↗
PubMed1986

Absence of intermediate filaments in a human adrenal cortex carcinoma-derived cell line.

Subclones of a human adrenal cortex carcinoma-derived cell line (SW13) are described which by immunofluorescence lack detectable expression of any of the five known classes of intermediate filament (IF) proteins. Further investigation for vimentin and keratins in these subclones by two-dimensional gel analysis and by immunoblotting gave results consistent with the immunofluorescence results. Despite the apparent absence of IFs, SW13 subclones have organized actin and microtubule cytoskeletal networks, maintain an epithelial shape and colony pattern, and grow well in culture. Although a rat hepatoma cell line which similarly appears to have ceased IF expression has been reported, this is the first such report of a human cell line. Although rare, these cases provide evidence that IFs in general are not essential to growth in culture, nor are the keratin-containing IFs in particular necessarily responsible for the 'cobblestone' morphology or colony-type growth pattern characteristic of cultured epithelial cells.

Actins↗
PubMed1986

Microtubules and the endoplasmic reticulum are highly interdependent structures.

The interrelationships of the endoplasmic reticulum (ER), microtubules, and intermediate filaments were studied in the peripheral regions of thin, spread fibroblasts, epithelial, and vascular endothelial cells in culture. We combined a fluorescent dye staining technique to localize the ER with immunofluorescence to localize microtubules or intermediate filaments in the same cell. Microtubules and the ER are sparse in the lamellipodia, but intermediate filaments are usually completely absent. These relationships indicate that microtubules and the ER advance into the lamellipodia before intermediate filaments. We observed that microtubules and tubules of the ER have nearly identical distributions in lamellipodia, where new extensions of both are taking place. We perturbed microtubules by nocodazole, cold temperature, or hypotonic shock, and observed the effects on the ER distribution. On the basis of our observations in untreated cells and our experiments with microtubule perturbation, we conclude that microtubules and the ER are highly interdependent in two ways: (a) polymerization of individual microtubules and extension of individual ER tubules occur together at the level of resolution of the fluorescence microscope, and (b) depolymerization of microtubules does not disrupt the ER network in the short term (15 min), but prolonged absence of microtubules (2 h) leads to a slow retraction of the ER network towards the cell center, indicating that over longer periods of time, the extended state of the entire ER network requires the microtubule system.

Animals↗
PubMed1986

Binding of 2-hydroxybenzo(a)pyrene to estrogen receptors in rat cytosol.

The potent carcinogen 2-hydroxybenzo(a)pyrene (2-OH-BP) competes for binding to the estrogen receptor in the cytosol of rat uterus and liver. The dissociation constant (K1) for this interaction is congruent to 2 X 10(-5) M. In contrast, 4-hydroxybenzo(a)pyrene does not bind to the estrogen receptor; 1-hydroxybenzo(a)pyrene, 5-hydroxybenzo(a)pyrene, 6-hydroxybenzo(a)pyrene, and 12-hydroxybenzo(a)pyrene bind less tightly than does 2-OH-BP. These five chemicals are not carcinogenic. We suggest that the estrogen receptor may mediate the carcinogenic effect of 2-OH-BP or of related chemicals. One possibility is that the receptor might convey 2-OH-BP to specific sites in DNA.

Animals↗
PubMed1985

Mitochondrial and plasma membrane potentials cause unusual accumulation and retention of rhodamine 123 by human breast adenocarcinoma-derived MCF-7 cells.

Quantitative studies of MCF-7 cells (derived from human breast adenocarcinoma) and CV-1 cells (from normal African green monkey kidney epithelium), using the permeant cationic compound tetraphenylphosphonium (TPP), in conjunction with fluorescence microscopy using rhodamine 123 (Rh123), indicate that the mitochondrial and plasma membrane potentials affect both uptake and retention of these compounds. Under conditions that depolarize the plasma membrane, uptake and retention of TPP and Rh123, driven only by the mitochondrial membrane potential, is greater in MCF-7 than in CV-1. An ionophore that dissipates the mitochondrial membrane potential of MCF-7 cells causes them to resemble CV-1 cells by decreasing uptake and retention. Hyperpolarizing the mitochondrial membrane of CV-1 increases accumulation and prolongs retention; hyperpolarization of the plasma membrane further heightens this effect, causing the uptake of CV-1 cells to resemble that of MCF-7 cells even more closely. The greater uptake and retention by MCF-7 appears to be a consequence of elevated mitochondrial and plasma membrane potentials. The plasma membrane potential affects mitochondrial retention of TPP and Rh123 and its role in enhancing the effect of a difference in mitochondrial membrane potential is explained.

Adenocarcinoma↗
PubMed1985

Human cell variants resistant to rhodamine 6G.

Two variants have been isolated from the cultured human cell line VA2-B which are resistant in vivo to the mitochondrial-specific fluorescent dyes rhodamine 6G and rhodamine 123. Both mutants are cross-resistant to ethidium bromide but are sensitive to both colchicine and chloramphenicol. When either mutant is treated with low levels of rhodamine 6G, mitochondrial-associated fluorescence is significantly lower than in wild-type cells. Furthermore, when cell cultures are treated with high concentrations of either rhodamine 123 or 6G, and then washed free of the dye, mitochondrial-associated rhodamine fluorescence rapidly diminishes in the parental cell line. In hybrid cell fusions between resistant and sensitive cell lines, rhodamine resistance is gradually expressed, reaching maximal expression approximately 11 days after fusion. Cytoplasmic transmission of rhodamine resistance has not been clearly demonstrated in cytoplast-cell fusions, and thus resistance is probably due to a mutation of a nuclear, rather than mitochondrial DNA gene(s). These observations indicate that mitochondria of both rhodamine-resistant variants, unlike wild type, have a significantly decreased ability to bind and retain rhodamine, and thus their mitochondrial tramsmembrane electrical potential may be significantly reduced.

Cell Division↗
PubMed1985

Immunohistochemical localization of keratin in head and neck neoplasms and normal tissues.

Immunohistochemical localization of keratin antigens using keratin antisera and the immunoperoxidase technique have been shown to be helpful in identifying certain epithelial cells. Our study was designed to evaluate the application of this technique to head and neck neoplasms and normal tissues using two keratin antibody preparations. Our data indicate that the keratin antibodies stained normal epithelial structures in the head and neck except for cells with active secretory functions such as mucus, cerumen, or salivary secretion. Neoplasms of the head and neck showed keratin antibody staining for epithelial neoplasms and negative staining for mesenchymal neoplasms. The immunohistologic demonstration of keratin is useful in distinguishing undifferentiated or poorly differentiated epithelial malignancies from sarcomas or lymphomas and demonstrating myo-epithelial cells in salivary neoplasms.

Animals↗
PubMed1985

Selective killing of carcinoma cells "in vitro" by lipophilic-cationic compounds: a cellular basis.

Lipophilic positively-charged compounds are facilitated across biological membranes by the transmembrane potential of intact cells. One such compound, rhodamine 123, has recently been shown to be selectively toxic toward a variety of transformed (carcinoma), epithelial cells in vitro (Lampidis et al., 1982; Bernal et al., 1982; Lampidis et al., 1983). A mechanism that could account for the selectivity of this agent would be a difference in the plasma membrane potential between normal and carcinoma cells. We report here that a significantly higher transmembrane potential has been found in a pair of carcinoma (83 mV for human breast and -99 mV for human cervix) as compared to normal (-56 mV for marsupial kidney and -48 mV for monkey kidney) epithelial cell lines. We also identified 3 other positively-charged lipophilic compounds, safranin 0, rhodamine 6G and tetraphenylphosphonium chloride (TPP+), which show selective toxicity toward carcinoma cells in vitro, while an uncharged lipophilic analog, rhodamine 116, does not. These data suggest that the higher plasma membrane potential of carcinoma cells may in part contribute to the preferential accumulation and selective toxicity of the lipophilic cationic compounds we have examined. An extension of this concept to an in vivo environment could lead to a class of cationic compounds which selectively exploit differences between normal and carcinoma cells.

Animals↗
PubMed1985

Increased rhodamine 123 uptake by carcinoma cells.

The total cellular content of the fluorescent mitochondrial-specific dye rhodamine 123 (Rh-123) was quantified by butanol extraction as a function of time of exposure and dose for a variety of cell lines. These results were compared with observations made by fluorescence microscopy on dye localization and mitochondrial morphology. There appeared to be two categories of cell types based on Rh-123 uptake: those which progressively accumulate the dye, such as Ehrlich ascites tumor cells, carcinoma-derived lines MCF-7, PaCa-2, EJ, HeLa, and normal fibroblast line CCL 64; and those which appear to equilibrate with the extracellular dye within 1 h of incubation in Rh-123 (1 microgram/ml) with a minimal level of uptake, such as the normal epithelial-derived lines CV-1 and MDCK and the transformed fibroblast line 64F3. Within the first category, the absolute value of uptake per cell correlated with the concentration of Rh-123 in the medium and with the period of exposure to the dye up to a point of apparent cellular saturation. The length of time required for apparent saturation depended on the cell type. In the second category equilibration was very early, and the total uptake was a function of the extracellular concentration of Rh-123. This probably does not represent a saturation level of dye content in the non-accumulating, low uptake cell lines. Fluorescence microscopy revealed that Rh-123 localization was initially mitochondrial-specific for all of the cell lines examined. Over time, alterations in mitochondrial morphology and cytoplasmic fluorescence were observed in the high uptake cell lines but not in the minimal uptake cell lines. Incubation of the high uptake HeLa cell line with the mitochondrial membrane potential inhibitor p-trifluoromethoxyphenylhydrazone substantially decreased Rh-123 uptake. These observations may indicate a transformation-related characteristic of carcinoma cell mitochondria. It may be possible to exploit the mechanism responsible for the progressive accumulation of Rh-123 by carcinoma-derived cell types for chemotherapeutic approaches to certain types of carcinomas.

Animals↗
PubMed1984

Rhodamine 123 inhibits bioenergetic function in isolated rat liver mitochondria.

Rhodamine 123 accumulates in the mitochondria of living cells and exhibits selective anticarcinoma activity. The biochemical basis of toxicity was investigated by testing the effect of the dye on isolated rat liver mitochondria. Much lower concentrations of rhodamine 123 were required to inhibit ADP-stimulated respiration and ATP synthesis in well-coupled energized mitochondria than were required to inhibit uncoupled respiration and uncoupler-stimulated ATP hydrolysis. The amount of rhodamine 123 associated with the mitochondria was several-fold greater under energized as compared to non-energized conditions, which may explain why coupled functions appeared to be more sensitive than uncoupled functions to inhibition at low concentrations of rhodamine 123. It was concluded that the site of rhodamine 123 inhibition is most likely the F0F1 ATPase complex and possibly electron transfer reactions as well.

2,4-Dinitrophenol↗
PubMed1984

A phosphotyrosyl-protein phosphatase activity associated with acid phosphatase from human prostate gland.

Using [32P]P-Tyr-IgG and [32P]P-Tyr-casein phosphorylated by pp60v-src as substrates, studies on the phosphotyrosyl-protein phosphatase activity in human prostate gland indicate that it is associated with prostatic acid phosphatase. Evidence to support this conclusion include the following: (a) these two enzymatic activities co-purify to apparent homogeneity; (b) they co-migrated on polyacrylamide gel electrophoresis, ion-exchange and gel filtration chromatographies; (c) the exhibit identical thermostability; and (d) the phosphotyrosyl-protein phosphatase activity is sensitive to inhibition by p-nitrophenyl phosphate and by several classical inhibitors of prostatic acid phosphatase including L(+)-tartrate, molybdate, vanadate and NaF. The purified enzyme exhibits high specificity towards phosphotyrosyl-proteins with little activity towards several phosphoseryl-proteins and phosphothreonyl-proteins examined. The present findings indicate that prostatic acid phosphatase may function in vivo as a phosphotyrosyl-protein phosphatase.

Acid Phosphatase↗
PubMed1984

Effects of the mitochondrial probe rhodamine 123 and related analogs on the function and viability of pulsating myocardial cells in culture.

Rhodamine 123, a cationic fluorescent dye, has previously been shown to specifically localize in or on mitochondria in living cells. Since it has also been shown to be relatively non-toxic in a variety of cell types it has been a useful tool for probing mitochondria in vitro. In this report, using cardiac cells in culture, we demonstrate that rhodamine 123 and 6G both positively charged compounds, quickly inhibit beating and kill cardiac-muscle cells while uncharged or neutral rhodamines, 116 and B, produce neither effect. We also present data which illustrate that the cationic rhodamines inhibit oxidative phosphorylation in isolated mitochondria while the neutral dyes do not. It is suggested that both phenomena may be related.

Animals↗
PubMed1984

The intranuclear location of a herpes simplex virus DNA-binding protein is determined by the status of viral DNA replication.

The herpes simplex viral DNA-binding protein, ICP8, is targeted to two different locations in the cell nucleus as part of its maturation pathway. Prior to viral DNA synthesis ICP8 was found at discrete pre-replicative sites throughout the nucleus, where it exhibited a high salt-labile association with the nuclear matrix. During viral DNA replication ICP8 was localized in randomly distributed replication compartments, where it is bound to viral DNA. Initiation of viral DNA replication caused the protein to move from the prereplicative sites to the replication compartments, while inhibition of replication caused movement in the opposite direction. In cells where viral DNA synthesis was proceeding, a minor population of ICP8 may also have been associated with the prereplicative sites. The prereplicative sites may serve as a nuclear reservoir for ICP8 not bound to replicating or progeny DNA.

Animals↗