lucifer-yellow and Breast-Neoplasms

Bisphosphonates are widely clinically used inhibitors of bone resorption. Pre-clinical studies indicate that bisphosphonates also inhibit the growth of various cancer cells in vitro, but their in vivo anti-cancer activity varies greatly, depending on the tumor type. We compared the various cellular effects of bisphosphonates in breast cancer and mesothelioma cells, with differences in growth inhibition responses to bisphosphonate-treatment in vivo. We show that the growth inhibitory effects of nitrogen-containing bisphosphonates are significantly affected by excess Ca(2+) in a cell- and bisphosphonate-specific fashion. Furthermore, excess pyrophosphate-resembling bisphosphonates prevent nitrogen-containing-bisphosphonate-induced accumulation of unprenylated Rap1A, p38 phosphorylation and growth inhibition in human MDA-MB-231 breast cancer and mouse AB-12 mesothelioma cells. For some, but not all tested, pyrophosphate-resembling bisphosphonate: nitrogen-containing bisphosphonate combinations these results may be partially explained by the ability of the excess pyrophosphate-resembling bisphosphonates to chelate Ca(2+). In mice, subcutaneous AB-12 and MDA-MB-231 tumors exhibit positive staining for Ca(2+) minerals, as revealed with Von Kossa stainings. We further show that the AB-12 tumors accumulate significantly more of the bone scanning bisphosphonate, Tc99m-medronate, as compared with MDA-MB-231 tumors. In conclusion, our results suggest that Ca(2+) regulates the growth inhibitory effects of bisphosphonates in a target cell and drug-specific fashion. These findings may be of physiological relevance since many tumor types are calcified. They further suggest that bisphosphonates can accumulate in tumors that are growing at the visceral sites and that differences in tumor accumulation of bisphosphonates may regulate their in vivo sensitivity to these drugs.

Topics: Blotting, Western; Breast Neoplasms; Calcium; Cell Line, Tumor; Cell Survival; Connexin 43; Diphosphonates; Female; Flow Cytometry; Fluorescent Dyes; Humans; Isoquinolines; Mesothelioma; Nitrogen; p38 Mitogen-Activated Protein Kinases; Radiopharmaceuticals; rap1 GTP-Binding Proteins; Receptors, Antigen, T-Cell; Technetium Tc 99m Medronate

Melatonin exerts a direct antiproliferative effect on estrogen-responsive MCF-7 cells in culture. Recently, the importance of the anti-invasive actions of melatonin as a part of the oncostatic action of this indolamine has been reported. Gap junctional intercellular communication is known to be involved in controlling cell proliferation and differentiation, and a decrease in intercellular junctional communication has been described in highly invasive mammary cancer cells. Because melatonin at physiological doses (1 nM) shifts MCF-7 cells to a lower invasive status, we postulate that melatonin could modulate the levels of gap junctional intercellular communication in these tumor cells. To test our hypothesis, we studied gap junctional intercellular communication in MCF-7 human breast cancer cells previously (7-8 days) treated, or not, with melatonin (10 microM or 1 nM). Using the scrape-loading assay dye-transfer technique to introduce 0.05% Lucifer yellow into cells, we measured the ability of the tumor cells to transfer dye to adjacent cells. Rhodamine dextran (0.05%) was used as a control dye to verify that dye-transfer occurs through intercellular junctions. The presence of melatonin (10 microM or 1 nM) in the culture medium significantly increased (P < 0.01) the transfer of the dye to adjacent cells through gap junctions. This increase was greater at 10 microM melatonin, and averaged scan profiles of cells treated with melatonin 10 microM showed a statistically significant increase (P < 0.01) in the integrated optical density values, and a broadening of the densitometric scan. These findings suggest that melatonin could exert its antitumor action, at least in part, by increasing regulatory signals that are passed between adjacent epithelial cells through intercellular junctions.

Topics: Breast Neoplasms; Cell Communication; Dextrans; Female; Fluorescent Dyes; Gap Junctions; Humans; Isoquinolines; Melatonin; Rhodamines; Tumor Cells, Cultured

Tumour-endothelial cell adhesion forms a key role in the establishment of distant metastases. This study examined the effect of gamma linolenic acid (GLA), an anti-cancer polyunsaturated fatty acid (PUFA), on both the gap junction communication of human vascular endothelial cells and tumour cell-endothelial interactions. By using scrape loading of Lucifer yellow dye, we showed that GLA at non-toxic levels increased Lucifer yellow transfer, indicating improved gap junction communication. The fatty acid also corrected the communication that was reduced by the mitogenic and motogenic factor HGF/SF. GLA inhibited the tyrosine phosphorylation of connexin-43, a protein that formed gap junction in this cell. When human tumour cells were added to quiescent or HGF/SF-activated endothelial cells, the presence of GLA reduced adhesion of tumour cells to the endothelium. It is concluded that GLA reduces tumour-endothelium adhesion, partly by improved gap junction communications of the endothelium.

Topics: Breast Neoplasms; Cell Adhesion; Cell Communication; Cell Line; Colonic Neoplasms; Connexin 43; Endothelium, Vascular; Fatty Acids; Fluorescent Dyes; gamma-Linolenic Acid; Gap Junctions; Hepatocyte Growth Factor; Humans; Isoquinolines; Kinetics; Phosphorylation; Precipitin Tests; Tumor Cells, Cultured

Gap junctional intercellular communication (GJIC) as well as cell migration play an essential role in the metastatic cascade of human tumors. We show a dependence of metastatogenic phenotypes of human tumor cells (cell lines T 24, SCC-25, MDA-MB-361 and SK-BR-3) from the GJIC and the migration activity. The GJIC was studied by microinjection of the fluorescent dye Lucifer Yellow (LY) and cell migration was studied by investigating the locomotion of the tumor cells in 3-dimensional collagen matrices. Diminished GJIC seems to be more influential for the metastatic phenotype than modulation of the locomotory behavior of the tumor cells.

Topics: Breast Neoplasms; Cell Communication; Cell Movement; Collagen; Colorectal Neoplasms; Humans; Intercellular Junctions; Isoquinolines; Neoplasm Metastasis; Tumor Cells, Cultured