Induction of placental alkaline phosphatase in choriocarcinoma cells by 5-bromo-2'-deoxyuridine.

Growth of choriocarcinoma cells in the presence of 5-bromo-2'-deoxyuridine (BrdUrd) results in a 30- to 40-fold increase in alkaline phosphatase activity. The effects of BrdUrd is specific for phosphatase with an alkaline pH optimum. The induction by BrdUrd is probably not due to the production of an altered enzyme, since the induced enzyme resembles the basal enzyme in thermal denaturation and kinetic properties. Enzyme induction can be prevented by thymidine but not by deoxycytidine or deoxyuridine. The induction of alkaline phosphatase appears to require incorporation of the BrdUrd into cellular DNA. The presence of BrdUrd in the growth medium is not necessary for alkaline phosphatase induction in proliferating cells containing BrdUrd-substituted genomes. However, enzyme induction and maintenance of the induced levels of alkaline phosphatase in nonproliferating cells containing BrdUrd-substituted DNA requires the presence of the analogues in the medium. The induction of alkaline phosphatase by BrdUrd in probably an indirect process.     

Induction of alkaline phosphatase activity in HeLa cells by sodium butyrate.

The induction of HeLa cell alkaline phosphatase activity by sodium butyrate could be inhibited by the coadministration of caffeine or theophylline. The inhibitions were dose dependent, and at any given concentration the potency was theophylline greater than caffeine. Although the induction by sodium butyrate was more sensitive to the inhibition by the xanthines than was that produced by 5-iodo-2'-deoxyuridine, the magnitudes of the increases in cyclic AMP concentrations after treatment with the xanthines were similar in the inhibition of both types of induction. The induction of alkaline phosphatase activity by sodium butyrate also produced a shift in the thermostability pattern of the enzyme, with a proportionately greater increase in the heat-labile, rather than heat-stable, form of the activity.     

Induction of alkaline phosphatase activity in HeLa cells by sodium butyrate

Summary The induction of HeLa cell alkaline phosphatase activity by sodium butyrate could be inhibited by the coadministration of caffeine or theophylline. The inhibitions were dose dependent, and at any given concentration the potency was theophylline > caffeine. Although the induction by sodium butyrate was more sensitive to the inhibition by the xanthines than was that produced by 5-iodo-2′-deoxyuridine, the magnitudes of the increases in cyclic AMP concentrations after treatment with the xanthines were similar in the inhibition of both types of induction. The induction of alkaline phosphatase activity by sodium butyrate also produced a shift in the thermostability pattern of the enzyme, with a proportionately greater increase in the heat-labile, rather than heat-stable, from of the activity. Supported by National Cancer Institute Grant CA16460.     

Induction of alkaline phosphatase activity by synergistic action of dibutyryl cyclic adenosine monophosphate, prednisolone, butyrate and sodium chloride in cultured cells

Human urinary bladder carcinoma cells (JTC-32) retain a low alkaline phosphatase activity. Prednisolone or a hypertonic concentration of NaCl caused a moderate increase in the activity (10- to 15-fold of control), but dibutyryl cAMP or butyrate did not. Examination of the combined effect of these four agents revealed that they acted synergistically in any combination. When the cells were incubated with the four agents together, the enzyme activity increased 60- to 250-fold. Serum also contributed to this synergistic increase. These agents slightly inhibited cell growth and protein synthesis. The enzyme induction was completely inhibited by cycloheximide or actinomycin D. The synergistic effect of the four agents on the enzyme activity was also observed in other strains of carcinoma cells, human urinary bladder carcinoma cells (JTC-30) and monkey hepatocarcinoma cells (NCLP-6E). Thus, it is concluded that the coexistence of the four agents provides general and superior conditions for the induction of alkaline phosphatase in cultured carcinoma cells.     

Induction of osteoblastic cell differentiation by forskolin. Stimulation of cyclic AMP production and alkaline phosphatase activity

The effects of forskolin on differentiation of osteoblastic cells (clone MC3T3-E1) cultured in alpha-minimum essential medium containing 0.1% bovine serum albumin were investigated by assays of intracellular cyclic AMP level and alkaline phosphatase activity in the cells. Forskolin increased cyclic AMP production in the cells in a dose-related manner, the maximum increase being 250-fold above that of the controls. Alkaline phosphatase activity in the cells was also elevated as early as 24 h and rose to nearly its maximum at 48 h. The elevation was dose-dependent, with a maximum increase at 5 X 10(-6) M forskolin. Forskolin and prostaglandin E2 showed a supraadditive effect on cyclic AMP production in the cells and had an additive effect on alkaline phosphatase activity, whereas forskolin and dibutyryl cyclic AMP had little additive effect on either cyclic AMP production or enzyme activity. These results suggest that cyclic AMP is closely linked to the differentiation of osteoblastic cells in vivo.     

Induction by short-chain fatty acids of alkaline phosphatase activity in cultured mammalian cells.

Short-chain fatty acids, such as propionic, n-butyric, n-butyric, n-valeric, isovaleric, n-caproic, and n-caprylic acids, induce alkaline phosphatase activity in cultured mammalian cells. Long-chain fatty acids have no similar effects. With B-6 cells (mouse X Chinese hamster cell hybrids), n-butyrate at 2 to 5 mM exhibits the greatest activity. Induction begins exponentially about 24 hours after addition of the fatty acid and continues over 48 hours. Studies on the inducing activity-structure relationship revealed the necessity of a carboxyl and an ethyl or longer alkyl group. n-Butyrate shows a marked synergistic action of induction when added along with other types of inducers: adenosine 3':5'-cyclic monophosphate (cAMP) or 5-bromodeoxyuridine (BrdU). Treatment of other cell lines with either n-buryrate, cAMP, or BrdU revealed a cell-type specific response pattern of alkaline phosphatase. The biological significance of this effect of short-chain fatty acids is discussed.     

Induction of alkaline phosphatase by retinoic acid

Treatment of mammalian cells in culture with retinoic acid causes a time- and concentration-dependent increase of the specific activity of alkaline phosphatase. The increase reaches a factor of 15 and more and begins at a concentration of 10(-8)M retinoic acid. The induction is inhibited by cycloheximide or actinomycin D. The same isoenzyme of alkaline phosphatase is expressed in control and in retinoic acid-treated cells as demonstrated by the inhibitions by amino acids and peptides. The enzyme induction occurs in rat heart, skeletal muscle, brain, lung cells and HeLa cells. No induction was found in two lines of human melanoma cells. After treatment of cells with tunicamycin, the induction of alkaline phosphatase is detectable only in the homogenate and no longer detectable by histochemical methods. This shows that the glycosylation of the protein is an important step in the insertion of this enzyme into the plasma membrane.     

Multiple forms of alkaline phosphatase in untreated and 5-bromo-2'-deoxyuridine-treated choriocarcinoma cells

The alkaline phosphatases present in choriocarcinoma cells, either untreated or treated with 5-bromo-2′-deoxyuridine (BrdUrd), were purified and characterized. Three forms of phosphatase [I, IIa (or IIIa), and IIb (or IIIb)]were isolated from both the untreated and BrdUrd-treated cells. Although BrdUrd induced the synthesis of all three forms of alkaline phosphatase in these cells, the synthesis of forms IIa and IIb was, however, preferentially stimulated. The forms of phosphatase in choriocarcinoma cells resembled each other in their kinetic properties and thermal lability, but differed in their molecular weights and in their electrophoretic mobilities in nondenaturing polyacrylamide gels. All three phosphatases were inactivated by antiserum to term-placental alkaline phosphatase. The alkaline phosphatases from choriocarcinoma cells differed, however, from the enzyme from term placentas in several physicochemical properties. The phosphatases from choriocarcinoma cells had a lower K_m value for p-nitrophenyl phosphate, were more sensitive to inhibition by l-leucine, levamisole, l-p-bromotetramisole, and EDTA, and were more heat-labile. Phosphatase I comigrated with term-placental alkaline phosphatase on nondenaturing polyacrylamide electrophoretic gels, but phosphatases IIa and IIb migrated more slowly. The apparent molecular weights of phosphatase forms I, IIa, and IIb were estimated by gel filtration and polyacrylamide gel electrophoresis to be 115,000, 240,000, and 510,000, respectively. Although three molecular forms of alkaline phosphatase occurred in choriocarcinoma cells, the subunit molecular weight of these phosphatases appeared to be identical to each other and to the subunit of term-placental alkaline phosphatase (63,000 MW). The alkaline phosphatase in choriocarcinoma cells therefore exists in the dimeric, tetrameric, and octameric forms.     

5-Bromo-2'-deoxyuridine induces placental alkaline phosphatase biosynthesis in cultured choriocarcinoma cells

5-Bromo-2'-deoxyuridine (BrdUrd) stimulated the biosynthesis and hence increased the activity of placental alkaline phosphatase in choriocarcinoma cells. While BrdUrd had no effect on the rate of degradation or processing of placental alkaline phosphatase, it increased the rate of phosphatase synthesis. The stimulation of enzyme activity could be completely accounted for by the increase in alkaline phosphatase protein. Both control and BrdUrd-induced cells contained polypeptides of 61,500 and 64,500 Da, identified as the precursor and fully processed forms of placental alkaline phosphatase monomer. The half-life of this enzyme monomer in both control and BrdUrd-treated cells was estimated to be 36 h. BrdUrd induced a specific increase in the placental alkaline phosphatase mRNA leading to the observed enhancement of biosynthesis. The continued rise in alkaline phosphatase biosynthesis in BrdUrd-induced cells following BrdUrd removal indicated that this analog acted by incorporation into DNA.     

Saturation of anti cyclic nucleotides antibodies by endogenous cyclic nucleotides.

Rabbits immunized against cyclic AMP or cyclic GMP produce antibodies which are fully saturated by their respective endogenous cyclic nucleotides. This was proved a) in comparing radioimmunological measurements of cyclic nucleotides in antiserum and the binding site concentration determined by equilibrium dialysis, b) in showing the ineffectiveness of serum phosphodiesterase to hydrolyze the cyclic AMP present in the anti-cyclic AMP antiserum. Immunological and radioimmunological implications of this phenomenon are discussed.     

Induction of E. coli alkaline phosphatase synthesis in cells preincubated at low temperatures]

Cell preincubation at lowered t degrees was found to result in increased alcaline phosphatase synthesis. The ability of cells for increased alcaline phosphatase synthesis correlates with increased content of cis-vaccinic acid and higher liquidity of lipids. It has been ascertained that modifications caused by cell preincubation at lowered t degrees favour the greater stability of mRNA coding the alcaline phosphatase.     

The effect of bromodeoxyuridine and dibutyryl cyclic AMP on the induction of placental alkaline phosphate in human choriocarcinoma cells.

The effect of 5-bromo-2'-deoxyuridine (BrdUrd) and dibutyryl cyclic AMP (Bt2cAMP) on the expression of the placental isoenzyme of human alkaline phosphatase was examined in BeWo choriocarcinoma cells. By using a combination of specific immunoprecipitation and polyacrylamide-gel electrophoresis of cells labelled either metabolically with [35S]methionine or cell-surface-labelled with 125I, both BrdUrd (5 micrograms/ml) and 1 mM-Bt2cAMP were shown to result in the enhanced accumulation of a specific protein. This protein has immunochemical identity and co-electrophoreses with placental alkaline phosphatase in two-dimensional gels. These results clearly demonstrate that the induction of placental alkaline phosphatase activity in choriocarcinoma cells treated with these agents is a consequence of the accumulation of specific enzyme protein rather than of altered catalytic activity.     

Modification of the sensitivity of CHO cells to mitomycin C by dibutyryl cyclic AMP

The survival of CHO cells exposed to mitomycin C was decreased three times that of the cells treated with 1 mM dibutyryl cyclic AMP before mitomycin C treatment, as compared to the absence of treatment with this cyclic nucleotide. The sensitization effect began at 3-4 hours after the start of pre-treatment, reached a maximum at around 10 hours and continued to be effective. Post-treatment with the cyclic nucleotide for more than 12 hours increased the survival of CHO cells exposed to mitomycin C.     

Effects of sodium butyrate on human colonic adenocarcinoma cells. Induction of placental-like alkaline phosphatase

We have examined the effects of the "differentiating agent," sodium butyrate, on the induction of alkaline phosphatase in human colonic tumor cell line LS174T. Culture of these cells in the presence of 2 mM butyrate caused this activity to increase from less than 0.0001 unit/mg of protein to greater than 0.7 unit/mg of protein over an 8-day period. This induction proceeded in a nonlinear fashion with a lag time of 2-3 days occurring before enzymatic activity began to rise. These increases in activity were accompanied by elevations in the content of a placental-like isozyme of alkaline phosphatase as demonstrated by "Western" immunoblots. Dome formation, indicative of differentiation in cultured cells, also required 3 days treatment with butyrate before becoming evident. The rate of biosynthesis of the enzyme, examined using metabolic labeling with L-[35S]methionine and immunoprecipitation, was found to increase continuously between days 2 and 6 of butyrate treatment. "Northern" blot analysis indicated that treatment of these cells with butyrate caused greater than 20-fold induction of a 2700-base mRNA that hybridized to a cDNA probe for placental alkaline phosphatase. The mRNA for alkaline phosphatase produced by these cells upon butyrate treatment was approximately 300-400 bases smaller than the mRNA for alkaline phosphatase found in placenta. Human small intestine also contained two mRNAs that hybridized relatively weakly with the placental alkaline phosphatase probe. These results indicate that a placental alkaline phosphatase-like protein and mRNA are induced by butyrate in LS174T cells with a time course consistent with cellular differentiation preceding induction.