Morphological Transformation Of Syrian Hamster Embryo Cells Research Articles

Effect of glucocorticoids on TPA-induced inhibition of gap-junctional communication and morphological transformation in Syrian hamster embryo cells

The effect of glucocorticoids on 12- O-tetradecanoylphorbol-13-acetate (TPA)-induced inhibition of gap-junctional intercellular communication (GJIC) and morphological transformation in Syrian hamster embryo (SHE) cells was examined. Fluocinolone acetonide (FA) and dexamethasone (DEX) almost completely suppressed the effect of TPA on induction of transformed morphology. On the other hand, up to 1000 times higher FA and DEX concentrations did not influence the inhibitory effect of TPA on GJIC. Neither treatment with these glucocorticoids for 4, 24 or 48 h before TPA exposure nor 24 h co-exposure with TPA altered the effect of TPA on GJIC. Thus the potent effect of glucocorticoids as inhibitors of the promotional effect of TPA on morphological transformation in SHE cells does not result in alterations of TPA-induced inhibition of GJIC.

Use of the Syrian Hamster Embryo (SHE) Cell Transformation Assay for the In Vitro Testing of Five Pesticides

The morphological transformation of Syrian hamster embryo (SHE) cells has been used for the in vitro testing of the transforming activity of five pesticides (Dual, Vucht 524, Piritione, Decemtione and Supercypermethrin). Morphological transformation with two known inducers, 3-methylcholanthrene and N-methyl- N‘-nitro- N-nitrosoguanidine, was used as a positive control. It was found that only one of the tested pesticides, Dual, failed to induce morphological transformation in SHE cells, whereas the remaining four demonstrated varying degrees of positive response and could be regarded as potential carcinogenic chemicals.

Ability of peroxisome proliferators to induce cell transformation, chromosome aberrations and peroxisome proliferation in cultured Syrian hamster embryo cells.

Di(2-ethylhexyl)phthalate (DEHP), a commonly used plasticizer, induces proliferation of peroxisomes in liver cells and causes hepatocellular carcinomas when chronically administered in the diet to rodents. To examine possible mechanisms for DEHP-associated cancer, we have measured induction of morphological transformation, chromosome aberrations and peroxisome proliferations of cultured Syrian hamster embryo (SHE) cells by DEHP and other peroxisome proliferators. Morphological transformation of SHE cells was weakly induced by treatment for 48 h with DEHP and its metabolite mono(2-ethylhexyl)phthalate (MEHP). The transformation frequency by DEHP was enhanced by exogenous metabolic activation using rat liver postmitochondrial supernatants. Treatment for 24 h with DEHP resulted in chromosome aberrations of the cells only in the presence of exogenous metabolic activation. 2-(p-chlorophenoxy)-2-methylpropionic acid ethyl ester (clofibrate), a widely used hypolipidemic drug, failed to induce morphological transformation or chromosome aberrations of SHE cells. Treatment with [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid (WY-14,643), which is a more potent carcinogen than DEHP or clofibrate, elicited a lower frequency of morphological transformation than DEHP in the presence of exogenous metabolic activation but was more active than DEHP at inducing chromosome aberrations. Similar levels of peroxisome proliferation, as determined by an intensity of diaminobenzidine staining, were observed in cultures treated for 2 h with DEHP, MEHP, clofibrate or WY-14,643. These results suggest a possible involvement of genetic damage by DEHP metabolites in the induction of cell transformation of SHE cells by DEHP; however, no clear relationship among induction of peroxisome proliferation, carcinogenicity in vivo and cell transformation was observed. Although the ability to induce cell transformation and chromosomal mutations is not adequate to explain the carcinogenicity of this class of compounds, these biological effects may be contributory to the carcinogenic activities of peroxisome proliferators.

Heterologous gap junctional intercellular communication in normal and morphologically transformed colonies of Syrian hamster embryo cells.

A study was made of whether normal and morphologically transformed colonies in the Syrian hamster embryo (SHE) cell transformation assay performed heterologous gap junctional intercellular communication (GJIC). Two compounds, 12-O-tetradecanoylphorbol-13-acetate (TPA) and Na-orthovanadate (vanadate), which induce high frequencies of morphological transformation in SHE cells, have been employed. Three approaches were used to study the possibility of heterologous GJIC. (i) Morphologically transformed colonies (induced by TPA) partially overlapping with normal colonies were selected. Cells in the border area were micro-injected with the fluorescent dye Lucifer yellow to determine whether the dye spread to cells belonging to the other colony. This approach proved to be unsuccessful due to an inability to pinpoint which cells belonged to which colony. (ii) X-irradiated, non-dividing feeder cells are easily recognized by their large size. Feeder cells in contact with normal or TPA-transformed colonies were injected with Lucifer yellow. The dye was found to spread to most of the contacting cells, irrespective of whether they belonged to a normal or morphologically transformed colony. (iii) TPA- and vanadate-exposed colonies were labelled by endocytosis of Lucifer yellow overnight. This resulted in a punctate fluorescent pattern. Unlabelled, previously unexposed cells were seeded onto the dishes and incubated for 3.5-7 h. The ability to perform heterologous GJIC between the newly seeded cells and labelled colony cells was investigated. Both normal and transformed colonies were found to be able to communicate with the newly seeded cells. Thus, the present results indicate that selective communication is not a general property of morphologically transformed SHE cell colonies.

5-Azacytidine induces micronuclei in and morphological transformation of Syrian hamster embryo fibroblasts in the absence of unscheduled DNA synthesis

It is known that 5-azacytidine (5-AC) induces tumors in several organs of rats and mice. The mechanisms of these effects are still poorly understood although it is known that 5-AC can be incorporated into DNA. Furthermore, it can inhibit DNA methylaion. The known data on its clastogenic and/or gene mutation-inducing potential are still controversial. Therefore, we have investigated the kinds of genotoxic effects caused by 5-AC in Syrian hamster embryo (SHE) fibroblasts. Three different endpoints (micronucleus formation, unscheduled DNA synthesis (UDS) and cell trnsformation) were assayed under similar conditions of metabolism and dose at target in this cell system, 5-AC induces morphological transformation of SHE cells, but not UDS. Therefore, 5-AC does not seem to cause repairable DNA lesions. Furthermore, our studies revealed that 5-AC is a potent inducer of micronuclei in the SHE system. Immunocytochemical analysis revealed that a certain percentage of these contain kinetochores indicating that 5-AC may induce both clastogenic events and numerical chromosome changes.

Morphological transformation of Syrian hamster embryo cells by aminobenzyl alcohols and nitrobenzyl alcohols is correlated with intercellular communication

Two aminobenzyl alcohols (ABAs) and 3 nitrobenzyl alcohols (NBAs) were studied in the Syrian hamster embryo (SHE) cell transformation system. All compounds induced statistically significant increases in morphological transformation of SHE cells. 2-ABA and 3-ABA induced dose-dependent increases in transformation, while the transformation frequencies for 2-NBA and 4-NBA decreased when concentrations were increased above 0.2 mM. When tested in an intercellular communication assay using dye transfer between SHE cells, 2-ABA inhibited communication, and 2-NBA and 4-NBA enhanced communication. Thus, the inverse dose-response of 2-NBA related to an increased intercellular communication.

Morphological transformation and catalase activity of syrian hamster embryo cells treated with hepatic peroxisome proliferators, TPA and nickel sulphate

The abilities of the hepatic peroxisome proliferators (HPPs) clofibrate, di(2-ethylhexyl)phthalate (DEHP), mono(2-ethylhexyl)-phthalate (MEHP), 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and tiadenol to induce morphological transformation and to increase the catalase activity of Syrian hamster embryo (SHE) cells were studied. DEHP, MEHP, clofibrate and tiadenol induced morphological transformation of SHE cells and increased the catalase activity. DEHP was more potent than clofibrate and tiadenol in both inducing catalase and morphological transformation, while MEHP seemed more potent than DEHP in inducing catalase, but not morphological transformation, 2,4,5-T and 2,4-D did not induce morphological transformation, but 2,4,5-T was more potent than clofibrate in increasing the catalase activity. These results show that several HPPs induce morphological transformation of SHE cells and an increase in the catalase activity. There is, however, no direct connection between these two parameters, as seen from the results of 2,4,5-T. The tumor promoter TPA, and the metal salt nickel sulphate, induced morphological transformation of SHE cells without any appreciable increase in the catalase activity. These results further corroborate the dissociation between induction of morphological transformation and the increase in catalase activity.

Prolonged in vitro exposure of Syrian hamster embryo cells to 3-aminobenzamide induces transformation and chromosomal alterations but not gene mutations.

To investigate the genetic mechanisms involved in morphological transformation of Syrian hamster embryo (SHE) cells, we have studied the transforming potential of 3-aminobenzamide (3-AB). It was found that prolonged exposure to 3-AB induced morphological transformation of SHE cells as well as C3H10T 1/2 cells. At similar doses, 3-AB induced SCEs and chromosomal alterations (gaps, breaks and exchanges) in SHE cells, but no mutations at the hypoxanthine-guanine phosphoribosyl transferase locus. These data strongly suggest morphological transformation can result from genetic alterations other than gene mutations. The possible nature of these genetic alterations involved will be discussed.

Cytotoxic and neoplastic transforming effects of industrial hexavalent chromium pigments in Syrian hamster embryo cells.

Twenty eight moderately water-soluble to insoluble chromium (VI) compounds, such as zinc and lead chromate, industrial and laboratory synthesized pigments, and the analytical reagents strontium, barium and calcium chromate, were physicochemically characterized and studied for cytotoxicity and morphological transformation in cultured Syrian hamster embryo (SHE) cells. In vivo validation of malignancy of transformed SHE cells was performed. A high physicochemical diversity among the complex chromium pigments was revealed. The solubility of the compounds was greatly increased after incubation in a complete medium and even higher under cell culture conditions. The cytotoxic effects appeared to be due principally to extracellular solubilized chromium because the most solubilized compounds. Zn, Ca and Sr chromates, were equitoxic at about the same Cr concentration treatment and 8-fold more cytotoxic than less soluble compounds such as some Pb chromates and Ba chromate. However, certain physicochemical properties of lead chromate pigments could also influence their cytotoxic activity. All test compounds were, in a dose-dependent manner, efficient in inducing morphological transformation of SHE cells. Many of the Cr pigments, although physicochemically different, were similarly effective in transformation induction. Nevertheless, compounds among Zn and Pb chromates had various transforming potencies. Ba chromate was the least active in inducing transformation. Certain physicochemical properties could mediate the transforming activity but no particular relationship could be established between any one of the physicochemical parameters and the transforming potency. Cloned morphologically-transformed colonies of SHE cells were grown in soft agar medium and showed true neoplastic behaviour by tumour formation in syngeneic animals. These results show that various chromate pigments containing either Zn or Pb, of medium to very low aqueous solubility, induced neoplastic transformation of SHE cells.

Enhanced morphological transformation of early passage Syrian hamster embryo cells cultured in medium with a reduced bicarbonate concentration and pH.

Recent studies from our laboratory have demonstrated that clonal cell proliferation of early passage Syrian hamster embryo (SHE) cells is optimal at a bicarbonate concentration in the culture medium of 8.9 mM (pH 6.65-6.75) under the experimental conditions reported. The purpose of the studies reported here was to examine whether morphological transformation induced by benzo[a]pyrene (BP) was enhanced under optimal culture conditions for SHE cell proliferation. Culture media of pH 6.70, 7.11 and 7.34 under incubator conditions of 10% CO2 in air were obtained by the addition of 0.75 (8.9 mM), 2.25 (26.8 mM) and 3.75 g/l (44.6 mM) of NaHCO3 respectively to a modified formulation of Dulbecco's modified Eagles medium. The frequency of morphological transformation of SHE cells was increased at 8.9 mM bicarbonate (pH 6.70) relative to media containing 26.8 or 44.6 mM bicarbonate (pH 7.11 and 7.34 respectively). Additionally, the isolate of embryo cells and lot of fetal bovine serum used supported transformation induced by BP at 8.9 mM bicarbonate (pH 6.70), but did not with media of higher bicarbonate concentration and pH. The duration of cell culture and the no. of colonies per plate influenced the amount of increase of morphological transformation observed at 8.9 mM bicarbonate relative to media of higher bicarbonate concentration. Initial studies have shown that a fraction of morphologically transformed colonies generated at reduced bicarbonate concentration were tumorigenic in newborn hamsters. These results are discussed in terms of the potential utility of low bicarbonate concentration cultured SHE cells for transformation studies.

Physicochemical characteristics and biological effects of nickel oxides.

Ten nickel oxides and nickel-copper oxides, which all contained NiO (bunsenite) as the predominant crystalline phase, were assayed as follows: in vitro dissolution tests in water and body fluids; in vitro phagocytosis tests in Chinese hamster ovary and C3H-10T1/2 cells; morphological transformation and cytotoxicity tests in cultured Syrian hamster embryo (SHE) cells; erythropoiesis stimulation assay by intrarenal administration to Fischer-344 rats; and scoring the renal histopathologic responses in rats killed 3 months post-injection. The test compounds differed substantially in their biological effects when tested in the various experimental systems. Based upon highly significant concordance of ranked results in the assays (P less than 0.001), six colligative biological attributes of the compounds were identified: (i) dissolution half-times in rat serum and renal cytosol; (ii) phagocytosis by C3H-10T1/2 cells; (iii) morphological transformation of SHE cells; (iv) erythropoiesis stimulation in rats; (v) induction of tubular hyperplasia in rat kidneys; and (vi) induction of arteriosclerosis in rat kidneys. Strong rank correlation (P less than 0.01) between results of the cell transformation and erythropoiesis stimulation assays is especially notable, since the compounds were tested by blind protocols in independent laboratories. The presence of high surface area and demonstrable Ni(III) were two physicochemical characteristics that were associated with the greatest biological effects of nickel oxides.

Morphological transformation of Syrian hamster embryo fibroblasts by the anabolic agent trenbolone.

Trenbolone (TBOH), a synthetic androgen used as an anabolic agent in livestock, has been tested for mutagenicity in the Salmonella assay, for covalent DNA-binding in vitro, for induction of unscheduled DNA synthesis in HeLa cells and Syrian hamster embryo (SHE) fibroblasts and for morphological transformation of SHE cells. While TBOH gave negative results in the assays for mutagenicity and DNA damage, it was clearly capable of transforming SHE cells in culture. The natural androgen testosterone did not transform these cells. Thus, TBOH appears to be a substance which can transform cells independent of its hormonal action and without grossly damaging DNA.

Genetic and molecular mechanisms of the in vitro transformation of Syrian hamster embryo cells by the carcinogen N-ethyl-N-nitrosourea. I. Correlation of morphological transformation and enhanced fibrinolytic activity to gene mutation, chromosomal alterations and lethality.

The role of chromosomal alterations, as opposed to gene mutations, in the origin of early stages of the in vitro transformation of Syrian hamster embryo (SHE) cells was investigated. For that purpose we compared the rates at which SHE cells recover from potential tumorigenic, mutagenic, clastogenic and cytotoxic damage if they are held in confluence in low serum medium for 3 or 6 days following a single treatment of N-ethyl-N-nitrosourea (ENU) before the cells are allowed to divide and to express this damage. The results show: (i) that frequencies of gene mutations remain constant; (ii) frequencies of sister chromatid exchange (SCE) and cytotoxicity decrease with very similar kinetics; and (iii) frequencies of chromatid aberrations and micronuclei decrease rapidly in the first 3 days, but slowly or not at all between days 3 and 6. Thus, all the mutational damage and a small fraction of the clastogenic damage still persist after 6 days confluent holding. From the two early stages of in vitro transformation studied, morphological transformation and enhanced fibrinolytic activity, the former shows similar kinetic behaviour as chromatid aberrations and micronuclei, whereas the kinetics of the latter correspond with those of gene mutations. Neither is correlated to SCE or cytotoxicity. Our results suggest that chromosomal alterations can play a major role in induction of morphological transformation of SHE cells. Insofar as enhanced fibrinolytic activity is due to a genetic change, gene mutations can be responsible. Our observations further indicate that different types of ENU-induced DNA lesions are involved in gene mutations, SCE and cytotoxicity, and clastogenic damage. We have reported the results of experiments analysing these relationships in another paper.