Search

Proliferation and differentiation were assessed in a series of human colon carcinoma cell lines in response to a mineral-rich extract derived from the red marine algae, Lithothamnion calcareum. The extract contains 12% Ca2+, 1% Mg2+, and detectable amounts of 72 trace elements, but essentially no organic material. The red algae extract was as effective as inorganic Ca2+ alone in suppressing growth and inducing differentiation of colon carcinoma cells that are responsive to a physiological level of extracellular Ca2+ (1.4mM). However, with cells that are resistant to Ca2+ alone, the extract was still able to reduce proliferation and stimulate differentiation.

TGFbeta exerts a potent tumor-suppressive effect in the human colon carcinoma CBS and Moser cells. However, TGFbeta can also function as a tumor promoter. The mechanisms underlying the tumor promoting effect of TGFbeta are not understood. Both the CBS and Moser cells were found to express mutant (truncated) APC. Expression of this form of APC did not interfere with the tumor-suppressive function of TGFbeta. However, when APC expression was knocked down in these cells, TGFbeta function switched from that of tumor suppression to that of tumor promotion. TGFbeta stimulated cellular invasion and anchorage-independent growth in APC knocked-down cells. Knocking down APC expression abrogated the ability of TGFbeta to induce the expression of the tumor suppressor E-cadherin and the cyclin dependent kinase inhibitor p21/Waf1. TGFbeta now stimulated the constitutive TCF transcriptional activation activity associated with the beta-catenin/Wnt pathway in the APC knocked-down cells. Thus, the level of APC expression determined the type of TGFbeta function in these human colon carcinoma cells.

Transforming growth factor beta (TGFbeta) suppresses the malignant phenotype of human colon carcinoma cells through diverse cellular pathways. Activation of beta-catenin/Wnt signal pathway underlies the malignant phenotype of human colon carcinomas. The Smad family of signal transducing, sequence-specific transcription activators are mediators of TGFbeta signaling. In this report, we showed that TGFbeta suppressed the beta-catenin/Wnt signal pathway in human colon carcinoma cells and stimulated an adhesion response in these cells in a Smad4/DPC4 independent manner. Smad/DCP4, however, was found to be linked to the growth-inhibitory action of TGFbeta.

The goal of this study was to enhance gene delivery and tumor cell transfection in vivo by using a combination of ultrasonication with complex nanoparticles consisting of two types of nanoparticles: PEI/DNA beta-gal plasmid with highly positive zeta-potential and air-filled poly (lactic-co-glycolic acid) (PLGA) particles (with negative zeta-potential) manufactured in our laboratory. The PLGA/PEI/DNA nanoparticles were a colloid with positive zeta-potential and injected i.v. in nude mice with DU145 human prostate tumors. We found that the combination of PLGA/PEI/DNA nanoparticles with ultrasonication substantially enhanced tumor cell transfection in vivo. The overexpression of beta-gal gene was evaluated histochemically and by Western blot analysis. At least an 8-fold increase of the cell transfection efficacy was obtained in irradiated tumors compared to non-irradiated controls, while little to no cell death was produced by ultrasonication.

Diospyrin, a bisnaphthoquinonoid natural product, and three synthetic derivatives have been tested for their action in four human cancer cell lines: acute myeloblastic leukemia (HL-60), chronic myelogenic leukemia (K-562), breast adenocarcinoma (MCF-7) and cervical epithelial carcinoma (HeLa). In cells grown in appropriate media several derivatives elicited cytotoxicity as assessed by Trypan Blue dye exclusion, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide reduction and DNA synthesis. Diethyl ether derivative (D7) was most effective in this regard while the parent compound diospyrin (D1) was least active (D7>D3>D2>D1). D7 was not cytotoxic toward normal human lymphocytes, suggesting its action is specific for tumor cells. On microscopic examination D7-treated cells exhibited characteristic morphological features of apoptosis, such as cell shrinkage and formation of apoptotic bodies. Fluorescent staining with propidium iodide revealed distinct chromatin condensation and nuclear fragmentation. The apoptotic index paralleled cytotoxic parameters, and fragmented DNA extracted free of genomic DNA displayed on gel electrophoresis a typical ladder pattern. D7-induced apoptosis was mediated via activation of caspase 3 and caspase 8.

Previous studies suggest that transforming growth factor-alpha (TGF alpha) may have the potential of a tumor marker. Since the levels of serum TGF alpha in cancer patients and healthy individuals have not been reported, we determined the serum TGF alpha levels of 83 breast cancer patients and 74 healthy individuals by using a TGF alpha radioimmunoassay kit. All of the cancer patients' sera were positive for TGF alpha; their TGF alpha concentrations ranged from 210 to 740 pg/ml, with a mean of 353 +/- 98 pg/ml. Sixty-seven percent (50 cases) of normal sera were positive for TGF alpha; the levels ranged from 120 to 207 pg/ml, with a mean of 144 +/- 17 pg/ml. The difference in serum TGF alpha levels between cancer patients of different disease stages and healthy individuals was found to be statistically significant by Student t-test and the Mann-Whitney test. No correlation was found between serum carcinoembryonic antigen and TGF alpha levels. The potential of serum immunoreactive TGF alpha as a marker for breast cancer warrants further investigation.

The nuclear protein and phosphoprotein profiles from 3 subpopulations of human colonic carcinoma cells which expressed different levels of neoplastic properties were characterized by two-dimensional electrophoresis. The silver stained nuclear protein profiles were found to be remarkably similar among the subpopulations. However, 2 types of nuclear proteins were found to be selectively modified by phosphorylation/dephosphorylation reactions. The dephosphorylation of type I and the phosphorylation of type II nuclear proteins were found to be associated with the HCT 116a subpopulation which expressed a high level of neoplastic properties. Conversely, the phosphorylation of type I and the dephosphorylation of type II nuclear proteins were found to be associated with the HCT 116b subpopulation, which expressed a low level of neoplastic properties. The HCT 116 subpopulation, which expressed an intermediate level of neoplastic properties, was found to possess an intermediate phosphoprotein profile relative to that of the other two subpopulations. Selective modification of cellular proteins by phosphorylation/dephosphorylation reactions may be involved in the generation of tumor cell diversity and heterogeneity.

The effects of retinoic acid on a transformed mouse embryo fibroblast cell line (AKR-MCA) were examined. Treatment with retinoic acid restored a non-transformed phenotype to this transformed cell line in a dose dependent manner. Retinoic acid (RA) treated AKR-MCA cells showed a non-transformed morphology, a slower growth rate, and did not grow with anchorage independence. A 38,000 Da protein was phosphorylated to a high degree in the AKR-MCA transformed cell line compared to the non-transformed AKR-2B cell line. RA treatment greatly reduced the level of phosphorylation of this protein in AKR-MCA cells. Growth arrested AKR-MCA cells showed a mitogenic response to nutrient replenishment, but not to epidermal growth factor (EGF). Treatment of AKR-MCA cells with RA restored their ability to respond to EGF while the response to nutrient replenishment was lost. This pattern of growth control was similar to that of the non-transformed AKR-2B cells.

Cellular phosphoprotein profiles from normal mouse embryonic fibroblast AKR-2B cells were compared to those of their permanently, chemically transformed malignant counterparts AKR-MCA cells, and AKR-2B cells reversibly transformed by transforming growth factor (AKR-TGF). Similar 32P-phosphorylation profiles were observed for both the AKR-TGF and AKR-MCA cells which were distinct from that of the normal AKR-2B cells. Dimethylformamide (DMF)-induced differentiation of the AKR-MCA cells resulted in a restoration of the normal AKR-2B phosphorylation profile to the malignant AKR-MCA cells.

Mouse leukemia cells (p388D1) were grown in medium containing various amounts of mitomycin C for 4 h. Cellular localization of protein B23 was detected using an immunofluorescence technique. Translocation of protein B23 from nucleoli to the nucleoplasm was observed with increasing dose of mitomycin C. To study the correlation of B23 translocation and drug resistance, three human colon carcinoma cell lines, HCT116, HCT116b (a line that is natively or intrinsically resistant to mitomycin C), and HCT116-44 (a line with an acquired resistance to mitomycin C), were employed. These cells were incubated with 1--150 micrograms/ml of mitomycin C. The drug concentration that caused 50% of the cells to have complete translocation (IC50) was determined for each cell line. The IC50 values of HCT116, HCT116b and HCT116-44 were 6, 10 and 50 micrograms/ml, respectively. These IC50 values correlate well with the mitomycin C resistant phenotype of these tumor cells as determined by other in vivo and in vitro assays (Willson, et al. (1985) Cancer Res., 45, 5281-5286). These results identify an inverse relationship between the ease of protein B23 translocation and the degree of mitomycin C resistance in human colon carcinoma cells. This relationship applies to cells that have either acquired mitomycin C resistance or intrinsic resistance to the drug.

The molecular mechanism(s) responsible for the generation of phenotypic diversity within tumors is not understood. Since the cell surface/plasma membrane components are involved in a variety of important biological function such as growth and differentiation regulation which may be mediated through intercellular and/or extracellular matrix interaction, the plasma membranes from 3 human colonic carcinoma cell lines (originally isolated from a single primary tumor) were purified and characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Membrane carbohydrate moieties were also characterized by a panel of 5 125I-labeled lectin probes following their electrophoretic fractionation and transfer onto nitrocellulose. Though these cell lines possessed diverse biological properties, their Coomassie blue stained electrophoretic protein profiles were found to be very conserved. The altered quantitative expression of only 1 membrane protein (Mr = 46 KD) was found to be associated with the more neoplastic HCT 116a cells which distinguished this cell line from the less neoplastic HCT 116b and HCT 116 cells. All 5 lectin binding profiles, on the other hand, clearly and easily distinguished the HCT 116a cells from the HCT 116b and HCT 116 cells. Thus, heterogeneity in terms of differences in membrane carbohydrate moieties was more obvious.

Acquired mitomycin C (MMC) resistant phenotype in the HCT 116 human colon carcinoma cell line is associated with an inability of the resistant cells to activate MMC (Cancer Res., 46 (1986) 3456). This report shows that the natively resistant human colon carcinoma cell line (HCT 116b), which had never been exposed to the drug, also exhibited a deficiency in MMC activation. The deficient activation of MMC in the natively resistant cells (like their acquired resistant counterpart) was circumvented by the MMC analog BMY28282 which was designed with a low quinone reduction potential and thus a greater ease of reductive activation. Interestingly, the development of acquired MMC resistance in the HCT 116 to a level of resistance similar to that of the natively resistant cells also resulted in several other molecular alterations that paralleled the molecular phenotype of the natively MMC resistant HCT 116b cells. These alterations included a significant increase in membrane Ricinus communis I binding carbohydrate moieties (Mr 80,000-92,000) and decrease in the expression of specific membrane antigens (Mr 55,000-57,000). The decrease in phosphorylation of specific nuclear phosphoproteins was also observed. This included a major nuclear phosphoprotein with approximate Mr- and pI-values corresponding to 63,000/5.0, and three groups of lower molecular weight phosphoproteins with approximate Mr- and pI-values corresponding to 22,000/6.4, 22,000/6.8, and 22,000/7.4. The results of these studies suggested that similar resistant mechanism(s) might exist in these acquired and natively MMC resistant cell lines which possessed similar level of resistance to MMC.

In this study we have compared the anti-proliferative effects of transforming growth factor-beta (TGF-beta), N,N-dimethylformamide (DMF) and retinoic acid (RA) on a moderately-differentiated colon carcinoma cell line (JVC). TGF-beta, DMF and RA inhibited the anchorage-independent growth and induced morphological changes in JVC cells. EC50 values of 40 pM TGF-beta, 0.5% DMF and 5 nM RA were obtained for growth inhibition. In addition all three agents enhanced cellular fibronectin levels in a time- and dose-dependent manner. Inhibition of cell proliferation as well as fibronectin induction by all three agents were reversible. Combinations of any two agents at suboptimal doses, added simultaneously to JVC cells gave additive inhibitory response on growth. These data indicate that the effects of TGF-beta in this colon carcinoma cell line are similar to those of the two differentiation promoting agents DMF and RA.