Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies with simian virus 40-transformed mouse 3T3 cells which are temperature sensitive for the expression of the transformed phenotype (ts SV3T3 cells) have shown that T-antigen expression and viral DNA transcription are under cell cycle control. Using these ts SV3T3 cells, we studied the expression of the viral genome under proliferating and non-proliferating conditions, in the presence and absence of inhibitors of macromolecular synthesis and of the tumor promoter phorbol myristate acetate. ts SV3TE cells which are growth arrested at 39 degrees C by low serum concentration or saturation density accumulated in G1 and did not express T-antigen. When these cells were induced to proliferate, at either 32 or 39 degrees C, T-antigen synthesis preceded the entry of the cells into the S-phase and was not coupled to DNA replication. G1-arrested ts SV3T3 cells were induced to synthesize T-antigen by phorbol myristate acetate treatment, but T-antigen alone was not sufficient to induce cellular DNA synthesis. Isoleucine deprivation arrested growth of ts SV3T3 cells, but these cells, as well as normal 3T3, did not accumulate in G1 and continued to express T-antigen. The temperature-sensitive expression of the transformed phenotype in the ts SV3T3 cells does not appear to be due to a lack of transcription of specific regions of the integrated simian virus 40 genome at 39 degrees C.
 ...
PMID:T-antigen expression in proliferating and non-proliferating simian virus 40-transformed mouse cells. 22 40

Rous sarcoma virus-transformed hamster BHK fibroblasts express a virus-induced cell surface antigen undetectable in cells either transformed by unrelated viruses or infected by transformation-defective strains of Rous sarcoma virus. To clarify whether this antigen plays any role in the process of malignant transformation or is expressed at the cell surface only as a consequence of the acquisition of the transformed phenotype, we have investigated its expression at the cell surface of Rous sarcoma virus-transformed BHK cells treated with dibutyryl cyclic adenosine 3':5'-monophosphate and at the surface of parental BHK cells transiently transformed by the tumor promoter phorbol myristate acetate. In the dibutyryl cyclic adenosine 3':5'-monophosphate-treated cells, in which most of the parameters of the transformed phenotype are reverted to normality, but the product of the transforming gene is still present, virus-induced cell surface antigen is expressed. In the mirror experiment, this antigen is not expressed by phenotypically transformed but genetically normal phorbol myristate acetate-treated cells. It is concluded that the tumor membrane antigen studied is intimately associated with the expression of the function(s) controlled by the transforming gene.
 ...
PMID:Relationship between Rous sarcoma virus-induced expression of membrane antigen and phenotypic transformation. 22 90

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate and the antileukemic agent mezerein are diterpene esters of plant origin with certain structural similarities. Both compounds, when applied topically to mouse skin, were equipotent on a molar basis in inducing hyperplasia, inflammation, and ornithine decarboxylase activity, as well as in reducing cyclic adenosine 3':5'-monophosphate accumulation in response to beta-adrenergic stimulation. In contrast, mezerein was much less effective as a tumor promoter; the phorbol ester at 8.5 nmol/application yielded 78-fold more tumors than did 8.5 nmol mezerein per application to similarly initiated SENCAR mice. The superiority of the phorbol ester was nearly as great in CD-1 mice.
 ...
PMID:Effects of 12-O-tetradecanoylphorbol-13-acetate and mezerein on epidermal ornithine decarboxylase activity, isoproterenol-stimulated levels of cyclic adenosine 3':5'-monophosphate, and induction of mouse skin tumors in vivo. 22 91

The diagnosis of malignant histiocytosis is usually based upon typical light microscopic features of the neoplasm. Supplementary cytochemical and immunologic features have been suggested as typical of malignant histiocytosis. The present study was prompted by an unusual erythropagocytic hepatocellular carcinoma having immunologic and cytochemical markers suggesting mononuclear phagocytic origin. Twenty-four neoplasms of unquestionable epithelial origin were prospectively evaluated for activity of alpha-naphthyl acetate esterase, a cytochemical marker useful in distinguishing between the non-Hodgkin's lymphomas and malignant histiocytosis. The epithelial tumors represented a broad spectrum of tissue origins and consistently demonstrated alpha-naphthyl acetate esterase activity. Thus, erythrophagocytosis and alpha-naphthyl acetate esterase positivity may be misleading in the unusual instance in which the histopathologic differential diagnosis includes malignant histiocytosis and epithelial neoplasia. Ultrastructural assessment is useful in the exclusion of poorly differentiated carcinoma.
 ...
PMID:Expression of monocytic--histiocytic cytochemical markers in epithelial neoplasia. 22 45

Carcinogenic chemicals enhanced infection in contact-inhibited cells with mouse leukemia virus. A correlation was found between the enhancing effects and the carcinogenicities of the 40 chemicals tested. The tumor promoter 12-O-tetradecanoylphorbol-13-acetate did not enhance viral infection.
 ...
PMID:Carcinogenic chemicals enhance mouse leukemia virus infection in contact-inhibited culture: a new simple method of screening carcinogens. 22 46

Intracellular concentrations of cyclic adenosine 3':5'-monophosphate (cyclic AMP) and cyclic guanosine 3':5'-monophosphate were measured in rat embryo fibroblasts stimulated to divide by either the addition of 12-0-tetradecanoyl phorbol-13-acetate (TPA) or a serum-supplemented medium change. Cyclic nucleotide levels were altered within minutes and large oscillations occurred in a reciprocal fashion over the pre-replicative and the replicative phases. Patterns of oscillating levels depended on the growth state of the cultures. Intracellular content of cyclic nucleotide similarly changed in response to either mitogenic treatment with the exception of the early alterations in cyclic AMP. The medium-change stimulation resulted within minutes in a drop of the cyclic AMP levels at confluence and a rise in growing cells when TPA-induced stimulation proceeded without altering those levels. Treatment with 4-0-methyl-phorbol didecanoate, a TPA derivative that is inactive as a tumor promoter, did not affect the cyclic nucleotide levels.
 ...
PMID:Cyclic nucleotide levels in rat embryo fibroblasts treated with tumor-promoting phorbol diester. 23 Feb 10

Induction of DNA synthesis by the tumor promoter tetradecanoyl phorbol acetate (TPA) was studied in a line of cultured rat fibroblasts (Rat-1) and their Rous sarcoma virus-transformed derivative (Rat-1 (RSV)). Following serum deprivation for 54 h to achieve quiescence, semiconservative DNA replication was measured by incubation of cells in BrdUrd and FdUrd after serum stimulation in the presence or absence of TPA. Optimal concentrations of TPA (0.1--0.5 microgram/ml) in serum-free medium induced a small increase (10--15%) in the amount of DNA made over a 30-h period in both Rat-1 and Rat-1 (RSV) cells. When Rat-1 cells were stimulated by a 4-h serum pulse, 30% of the DNA was replicated by 30 h. If the serum pulse was followed by TPA addition, 70% DNA replication was observed. If the serum pulse was preceded by TPA addition, the onset of DNA synthesis was delayed by several houses, but stimulation of DNA synthesis occurred. In contrast, the Rat-1 (RSV) cells did not show an increased in DNA synthesis induced by TPA in similar protocols, but the serum-induced onset of DNA synthesis was delayed by several hours in the presence of TPA. Therefore, TPA acts as a co-inducer of DNA synthesis in the Rat-1 but not in the Rat-1 (RSV) cells. The parent alcohol, phorbol, was inactive in Rat-1 cells, but delayed the onset of DNA synthesis in the Rat-1 (RSV) cells. We conclude that the co-inducing and delaying activities of TPA on DNA synthesis appear to be distinct and to act a different points in the G1 phase of the cell cycle.
 ...
PMID:Effects of the tumor promoter TPA on the induction of DNA synthesis in normal and RSV-transformed rat fibroblasts. 23 27

Clones of Friend erythroleukemia cells, characterized by the presence of 40-70% benzidine-positive cells synthesizing hemoglobin in the absence of inducing drugs, were treated with several phorbol diesters with a known range of tumor-promoting activity on mouse skin. Good correlation was found between the reported tumor-promoting activity of a particular phorbol diester and its ability to inhibit spontaneous erythroid differentiation in culture. The inhibition of differentiation by 12-O-tetradecanoyl-phorbol-13-acetate, the most active tumor promoter, was maximum after 4 days of treatment; this inhibition was reversed by removal of the phorbol diester no matter how long the period of treatment. Unlike control cells, which gradually revert to a population with a low percentage of benzidine-positive cells, cells treated with 12-O-tetradecanoyl-phorbol-13-acetate retained a high potential for spontaneous differentiation.
 ...
PMID:Tumor promoters inhibit spontaneous differentiation of Friend erythroleukemia cells in culture. 26 40

Benz[a]anthracene and the five metabolically possible vicinal trans dihydrodiols of benz[a]anthracene were tested for ability to initiate skin tumors in CD-1 female mice. A single topical application of 0.4-2.0 mumol of hydrocarbon was followed 18 days later by twice weekly applications of the skin promoter 12-O-tetradecanoylphorbol-13-acetate. Comparisons of latency period, percent of mice with tumors, and number of papillomas observed per mouse indicated that benz[a]anthracene 1,2-, 5,6-, 8,9-, and 10, 11-dihydrodiols were all less active tumor initiators than was benz[a]anthracene. The high tumorigenicity of benz[a]anthracene 3,4-dihydrodiol, presumably the result of metabolism to either or both of the diastereomeric benz[a]anthracene 3,4-diol-1,2-epoxides, supports the bay region theory of polycyclic hydrocarbon carcinogenicity and provides the first example of a proximate carcinogenic metabolite that is much more active than the parent hydrocarbon on mouse skin.
 ...
PMID:Tumorigenicity of five dihydrodiols of benz(a)anthracene on mouse skin: exceptional activity of benz(a)anthracene 3,4-dihydrodiol. 26 81

Addition of the potent tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), to murine erythroleukemia cell lines in suspension cultures inhibited both spontaneous differentiation and differentiation induced by hexamethylene bisacetamide (HMBA), dimethyl sulfoxide, or butyric acid. Inhibition was unrelated to cytotoxicity and was reversible. When several plant diterpenes were tested, there was a positive correlation between tumor-promoting activity and inhibition of differentiation. TPA inhibited HMBA-induced differentiation only if added prior to the time of commitment to differentiation, as assayed by scoring for differentiation after transfer of cells from HMBA to fresh medium without HMBA. TPA-mediated inhibition of differentiation was associated with a decrease in globin mRNA accumulation.
 ...
PMID:Tumor promoters inhibit spontaneous and induced differentiation of murine erythroleukemia cells in culture. 26 4


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>