deoxycholic-acid and Fibrosarcoma

Recent studies have implicated protein kinase C (PKC) activation in drug resistance in vitro. PKC can be activated directly by phorbol-ester tumor promoters as well as by the bile acid deoxycholate. In this report, we demonstrate that deoxycholate, at concentrations that are chronically present in the lumen of the colon in vivo, mimicked phorbol-ester tumor promoters by protecting Adriamycin (ADR)-sensitive and multidrug-resistant (MDR) murine fibrosarcoma UV-2237M cells from ADR cytotoxicity. Deoxycholate also enhanced the resistance of the MDR cell line UV-2237M-ADRR to the cytotoxic effects of vincristine and vinblastine. In contrast to cytotoxic drug-selected MDR phenotypes, deoxycholate-induced drug resistance was transient and required continuous exposure to the bile acid. The protein kinase inhibitor H7 completely reversed the protection against ADR cytotoxicity conferred on UV-2237M-ADRR cells by deoxycholate, providing evidence that deoxycholate exerts its protective effects by a mechanism that involves stimulation of protein phosphorylation and not merely by detergent effects on membrane permeability. PKC consists of a family of at least seven isozymes with distinct modes of activation and substrate specificities. We previously reported that MDR UV-2237M cell lines contain higher levels of PKC activity than the parental ADR-sensitive UV-2237M cell line (O'Brian et al., FEBS Lett 246: 78-82, 1989). The present report shows that PKC-III is a major PKC isozyme in ADR-sensitive and MDR UV-2237M cell lines. Thus, the resistance to ADR induced by the phorbol esters in UV-2237M cell lines provides strong evidence that PKC-III activation confers protection against ADR on ADR-sensitive and MDR UV-2237M cell lines. Furthermore, since deoxycholate is an endogenous molecule in the colonic epithelium, our finding that physiological concentrations of deoxycholate can render cells more resistant to chemotherapeutic drugs in vitro may have implications for the biology and therapy of intestinal cancers.

Topics: Animals; Cell Division; Dactinomycin; Deoxycholic Acid; Doxorubicin; Drug Resistance; Fibrosarcoma; Intestinal Neoplasms; Isoenzymes; Mice; Phenotype; Phorbol Esters; Protein Kinase C; Tumor Cells, Cultured; Vinblastine; Vincristine

Soluble tumor antigens were prepared from chemically-induced rat fibrosarcoma KMT-17 cells by sodium deoxycholate (DOC) extraction. Significant responses detected by the footpad assay and Winn assay were demonstrated in rats immunized with DOC extract. However, rats previously immunized with DOC extract showed a significant enhancement of tumor growth when challenged with KMT-17 cells. This enhancement was specific for the tumor line used. The tumor-neutralizing ability of KMT-17 immune spleen cells was abrogated when DOC extract immune spleen cells were added to a mixture of KMT-17 cells and KMT-17 immune spleen cells. This suppressive activity of the spleen cells was diminished by the treatment with anti T serum and complement. After fractionation of DOC extract immune spleen cells by the Ficoll density gradient, the cells in the light layer showed an enhancing effect on tumor growth, whereas the cells in the heavier region of the gradient had an inhibiting effect. These results suggested that both immunosuppressor cells and cytotoxic cells were induced in rats immunized with DOC extract.

Topics: Animals; Antigens, Neoplasm; Cytotoxicity, Immunologic; Deoxycholic Acid; Epitopes; Fibrosarcoma; Immunosuppression Therapy; Neoplasms, Experimental; Rats; Rats, Inbred Strains; Solubility

Immune response in WKA rats immunized with methylcholanthrene-induced KMT-17 tumor was measured by radioisotopic footpad assay. The assay was specific, quantitative, and objective compared with the ordinary method of measuring the thickness of footpads. The strongest footpad reaction was observed 24 hr after injection of the antigens. The reaction was transferred by lymphoid cells but not by serum. These results indicate that the footpad assay manifests delayed-type hypersensitivity to tumor antigens. In order to obtain more reliable antigen preparation for the footpad assay, antigens prepared by several methods were compared. Solubilized antigen extracted with sodium deoxycholate (DOC) showed the strongest reaction in the immunized host and weak reaction in the control non-immunized host. This marked difference between the immunized and control groups indicates that DOC-extracted antigen was better antigen than tumor cells treated with mitomycin-C (40 microgram/ml), formaldehyde solution (0.2%, 0.01%), X-irradiation (3,500, 10,000 rad), non-treated whole-cell antigen, crude membrane, cell homogenates, or antigens extracted by hypotonic sonication and 3M KCl method. The DOC-extracted antigen was well preserved at -20 degrees for 1 month.

Topics: Animals; Antigens, Neoplasm; Deoxycholic Acid; Epitopes; Fibrosarcoma; Hypersensitivity, Delayed; Iodine Radioisotopes; Methylcholanthrene; Mitomycins; Neoplasms, Experimental; Rats