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Characterization and modulation of human lymphokine (interleukin 2) activated killer cell induction.

Culture of human peripheral blood mononuclear cells with purified interleukin 2 (IL-2) results in the induction of a cytotoxic population of cells capable of lysing autologous tumor cells and natural killer (NK) cell resistant tumor cell lines. The current study was undertaken to characterize biological agents which might modulate the induction of lymphokine (IL-2) activated killer (LAK) cells and to optimize culture conditions for LAK cell induction. Preliminary studies were undertaken to characterize optimal time and IL-2 concentration for induction of LAK cell activity. Subsequently, we demonstrated that: (a) LAK cell induction is inhibited at high (2.5 X 10(6)/ml) cell concentrations and this phenomenon is due to the presence of monocytes; (b) depletion of monocytes allows LAK cell induction at 5-10-fold higher cell concentrations without altering the extent or range of LAK-cell activity; (c) interleukin 1 enhances and alpha- and beta-interferons inhibit IL-2 induced proliferation, without altering LAK cell induction; and (d) gamma-interferon alters neither IL-2 induction of proliferation nor LAK cell activity.

Cytotoxicity, Immunologic↗

Standard induction and low dose ara-C treatment in patients over 60 with AML or MDS.

In this retrospective study, 61 induction treatment periods in 57 patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) were evaluated. According to the WHO performance status, 6 patients received no chemotherapy, 20 had low dose cytosine arabinoside (LD ara-C) induction courses, and 35 received standard induction consisting of daunorubicin and cytosine arabinoside. Untreated patients had a poor survival. Of the 20 patients with LD ara-C induction courses, 4 (20%) achieved complete remission (CR). Three patients (15%) died during induction. Of 35 patients with standard induction, 21 patients (60%) achieved CR. Toxicity was considerable - 11 patients (31%) dying during treatment. We conclude that patients over 60 yr of age with RAEB, RAEB-t or AML had a CR rate and survival comparable to those of younger patients if treated with standard induction chemotherapy at the cost of serious therapy-related complications. In patients who were judged not to be able to tolerate standard induction and who were subsequently treated with LD ara-C, complications occurred less frequently, but the CR rate was low and survival short.

Aged↗

Characterization of the accessory cells involved in suppressor T cell induction.

The ability of UV-treated splenic adherent cells (SAC) to induce T cell-mediated immunity and suppressor T cells was analyzed in the 4-hydroxy-3-nitrophenyl acetyl (NP) system. UV irradiation of 0.88 KJ/m2 decreased the capacity of NP-coupled SAC to induce delayed-type hypersensitivity (DTH) responses by about 50%. The ability of uncoupled UV-treated SAC to induce allogeneic DTH response was also imparied, indicating that UV-treated SAC are inefficient at inducing DTH in these systems. TS1 induction by UV-treated NP-SAC was evaluated TS1 induction by UV-treated NP-SAC was evaluated by using adherent cells that were subjected to the same dose of UV irradiation that impaired DTH induction. Intravenous administration of 10(3) or 10(4) UV-treated NP-coupled SAC induced TS1 cells with the same efficiency as non-UV-irradiated cells. The TS1 cells induced in this fashion were antigen specific. Furthermore, to establish that the antigen was not reprocessed by the host, I-J-mismatched, UV-treated NP-SAC were unable to induce TS1 cells. The population of antigen-presenting cells responsible for TS1 induction appear to express both I-A and I-J determinants. TS2 induction by UV-treated accessory cells was also analyzed. TSF1 inducer suppressor factor was pulsed onto graded numbers of either normal or UV-treated adherent cells. The same levels of antigen-specific suppression were induced with normal and UV-treated cells. Finally, TS3 induction by UV-treated NP-SAC was analyzed. UV-treated and normal NP-SAC (3 X 10(3] induced antigen-specific suppression of NP DTH responses. I-J-mismatched, UV-treated NP-SAC failed to induce suppression, suggesting that the hapten was not reprocessed by the host under these experimental conditions. The accessory cell population responsible for TS3 induction appears to express both I-A and I-J determinants. Thus, there are at least two functional distinctions between the antigen-presenting cells that induce immunity vs those that induce suppressor cells. First, UV treatment selectively impairs the antigen-presenting cells, which activate the positive limb of the immune response. Second, I-J determinants appear to be specifically associated with the SAC, which induce suppressor T cells. Although these criteria can be used to distinguish the accessory cells involved in suppressor cell pathways from those controlling helper T cell induction, there were no discernible phenotypic differences among the accessory cells that induce the TS1, TS2, and TS3 subsets.

Animals↗

Persistent estrogen induction of hepatic Xenopus laevis serum retinol binding protein mRNA.

Administration of estradiol-17 beta to male Xenopus laevis induces the hepatic mRNA coding for the serum retinol binding protein (RBP) approximately 10-fold, both in vivo and in primary liver cultures. Estrogen induction of RBP mRNA is completely blocked by the anti-estrogen, hydroxytamoxifen. Testosterone administration reduces the elevated level of RBP mRNA observed in livers of female X. laevis to the constitutive level seen in livers of control male animals, and partially blocks the estrogen induction of RBP mRNA. Intracellular RBP mRNA levels therefore represent a balance between the opposing effects of estradiol-17 beta and testosterone. In marked contrast to the estrogen induction of vitellogenin mRNA, which requires the continuous presence of exogenous estrogen, induction of RBP mRNA persists for at least 4 months after a single injection of estrogen. Runoff transcription measurements demonstrate that persistent induction of RBP mRNA is due to an increased rate of RBP gene transcription. Administration of hydroxytamoxifen abolishes persistent induction of RBP mRNA, suggesting that residual hormone receptor complex plays a role in the persistent induction of RBP gene transcription. The persistent estrogen induction of RBP mRNA provides the first demonstration of long-term activation of the transcription of a hormone-responsive gene in response to a transient dose of a steroid hormone.

Animals↗

The control of bone induction in soft tissues.

The induction of bone at the boundary of parenchymal organs has been studied using acid demineralized rib implants in rabbits. The induction of bone is usually confined to that portion of an implant protruding from such an organ though both scant cartilage induction and the induction of bone within the territory of parenchymal organs were seen on a few occasions. Neonatal splenectomy does not influence the inductive properties of bone matrix in muscle or other soft tissues. The inclusion of composite autografts of liver and acid demineralized bone in muscle results in a reduction in the induction rate. It is postulated that the parenchymal organs exclude osteoprogenitor cells and possibly blood-bone bone-marrow-derived osteoinductor releasing cells by some mechanism that is diffusable, thus preventing the initial inductive event. Composite grafts of matrix and muscle produce bone in these tissue, demonstrating that once bone cell differentiation by induction is initiated bone tissue develops even in spleen, liver and kidney parenchyma.

Aging↗

Interferon-alpha-2b with VMCP for induction in multiple myeloma: the Israel Myeloma Cooperative Group experience.

In 1988, a prospective, randomized multicenter study was initiated to determine the efficacy of a combined induction regimen with recombinant interferon-alpha-2b (IFN-alpha) and maintenance with IFN-alpha on the response and survival rates in multiple myeloma (MM) patients. Induction therapy consisted of VMCP (vincristine, melphalan, cyclophosphamide, prednisone), randomized to combine IFN-alpha at a dose of 2 x 10(6) U, 5 days per week throughout the induction period of 12 months. Patients who achieved plateau phase were subsequently randomized again between IFN alpha maintenance (2 x 10(6) U, 3 days a week) for 12 months and no maintenance therapy. Of the previously untreated patients, 84 were initially randomized for induction therapy, and 31 for the maintenance phase with IFN-alpha. Results of the cohort median survival, based on the intention to treat, have shown that those on the VMCP/IFN-alpha arm had a median survival of 53 months, compared with patients on the VMCP induction arm who a median survival of 26 months (P = 0.052). The median survival of stage 3 evaluable patients who were on the VMCP/IFN induction arm was 43 months, and 13 months for patients treated by VMCP alone (P = 0.008). No significant difference in survival was detected among patients in partial remission (after induction) who had a second IFN-alpha randomization at the plateau phase. Hematologic toxicity, mild to moderate fever, and fatigue were more common in the VMCP/IFN induction arm. The results show that VMCP/IFN is a well-tolerated treatment regimen, and is superior to VMCP for patients with stage 3 myeloma.

Adult↗

An essential role of prostaglandin E on mouse mast cell induction.

We previously established a system for induction of mucosal-type mast cells from mouse spleen cells by long term culture without exogenous IL-3. FCS was important and was able to be divided into mast cell-inducible and non-mast cell-inducible sera. LPS contaminated in FCS was responsible for the mast cell induction. However, we unexpectedly found that both supernatants recovered from the cultures with mast cell-inducible and non-mast cell-inducible sera contained endogenous IL-3. Furthermore, addition of rIL-3 to the cultures with non-mast cell-inducible sera had no effect or induced only a small number of mast cells. This indicates that IL-3 alone is not enough for mast cell induction and that some inflammatory factor(s) induced by LPS is also essential. Prostaglandin E1 (PGE1) and PGE2 induced mast cells in a dose-dependent manner when added into the cultures. The activity of LPS for mast cell induction was inhibited by indomethacin. However, indomethacin failed to inhibit the mast cell induction by exogenous PGE. Exogenous PGE antagonized the indomethacin-induced inhibition of mast cell induction by LPS. Cholera toxin and dibutyryl cyclic AMP (cAMP) also induced mast cells. The A and B subunits of cholera toxin, PGF2 alpha, PGD2, and dibutyryl cGMP failed to induce mast cells. Furthermore, mast cell induction by PGE was dose-dependently suppressed by inhibitors for cAMP-dependent A kinase. The above results show that for mast cell induction, IL-3 needs the cooperation of PGE or other stimulants that can elevate the production of the second messenger cAMP in mast cell precursors.

Animals↗

[Fetal outcome after cervical ripeness-adjusted labor induction with prostaglandin E2 in relation to cervix status. Results of a multicenter study].

Prostaglandin E2 is often used for induction of labour. A procedure appropriate for obstetrical condition of the cervix uteri is recommended. 1,472 births with a medical indication were induced in a multicenter-study. With a bishopscore < 5 prostaglandin E2 gel intracervical and with a score between 5 and 8 vaginal tablets were used for induction. Appropriate for the condition of cervix it was allowed to continue the induction. With a bishopscore > 8 an infusion of oxytocin was given. The fetal outcome was evaluated appropriate for the condition of cervix before and during induction of labour. The APGAR-score one minute post partum was < 8 in 10.8 per cent of all neonates. This part was near the same in the gel- and in the tablet group (p > 5%). By continuation of induction, the part with pathological findings was at all times not in relation to the different groups of cervical condition. It's the same by APGAR-scores 5 and 10 minutes after delivery. The acidotic morbidity at all was 10.7%. Also in this connection it was only an unimportant (p > 5%) increasing to observe then the induction was continued. There is no relation between the different groups of cervical condition and the acidotic morbidity. Under observation of mother and child the to cervical condition appropriated used method of induction of labour does not expect a bad neonatal outcome. The longer the cervix is unripen, the higher is the rate of delivery by caesarean section. The exploitation of the possibilities of induction by drugs can be recommended.

Acid-Base Equilibrium↗

Elective induction versus spontaneous labor after sonographic diagnosis of fetal macrosomia.

OBJECTIVE: To test the hypothesis that elective induction of labor, compared to spontaneous labor, reduces the cesarean rate in women with a sonographic diagnosis of fetal macrosomia. METHODS: Sonography results over a period of 27 months were used to select 262 consecutive patients who met the following inclusion criteria: singleton pregnancy at term, estimated fetal weight (EFW) at the 90th percentile or greater, and delivery at our institution. The subjects were divided into four groups based on obstetric management: spontaneous labor (N = 115), elective induction of labor with macrosomia as the sole indication (N = 44), induction of labor for other maternal or fetal indications (N = 48), and elective cesarean delivery (N = 55). The analysis focused on the first two groups. These were compared regarding cesarean rate, indications for cesarean, and shoulder dystocia rate. Multiple logistic regression was used to control for potential confounders. RESULTS: With elective induction, the cesarean rate was 57%, significantly higher than the 31% rate with spontaneous labor (P < .01). The induced group also had a significantly higher EFW and birth weight. When logistic regression was used to control for birth weight, parity, and care provider, elective induction was still associated with a higher risk of cesarean delivery than was spontaneous labor (adjusted odds ratio 2.7, 95% confidence interval 1.2-5.9; P < .02). Shoulder dystocia occurred in one of 19 vaginal deliveries with elective induction (5.3%) and in two of 79 with spontaneous labor (2.5%). CONCLUSION: Because elective induction of labor increased the cesarean rate and did not prevent shoulder dystocia, we conclude that mothers with macrosomic fetuses can safely be managed expectantly unless there is a medical indication for induction.

Adult↗

Pharmacological studies of the regulation of chronic FOS-related antigen induction by cocaine in the striatum and nucleus accumbens.

Previous work has demonstrated that chronic administration of cocaine induces apparently novel Fos-like transcription factors, termed chronic Fras (Fos-related antigens), in the rat striatum and nucleus accumbens. Induction of these proteins is associated with prolonged increases in AP-1 DNA binding activity that parallel the long half-life of the chronic Fras in brain. The goal of the present study was to characterize pharmacologically the regulation of chronic Fra induction by cocaine. Chronic Fra induction was examined with respect to the cocaine dose, time course and administration intervals used. Cocaine was found to induce the chronic Fras over widely differing treatment regimens in the striatum and nucleus accumbens, although clear differences between the two brain regions were observed. In general, maximal induction occurred with moderate treatment conditions, with more or less intensive treatments resulting in lower levels of chronic Fras. The pharmacological mechanisms underlying cocaine induction of the chronic Fras were also investigated. Pretreatment with a D1 receptor antagonist, which did not affect chronic Fra levels by itself, attenuated cocaine induction of the chronic Fras in striatum and nucleus accumbens. In contrast, treatment with a D2 receptor antagonist alone greatly induced chronic Fra levels, with no further increase seen in response to combined treatment with cocaine. Combined treatment with D1 and D2 receptor agonists, or with amphetamine, led to a strong induction of chronic Fras. Similarly, repeated treatment with a specific dopamine transporter inhibitor increased chronic Fra levels, whereas treatment with a specific serotonin or norepinephrine transporter inhibitor failed to produce this effect. These results support an important role for dopaminergic neurotransmission in the induction of chronic Fras by cocaine. Taken together, the results of the present study provide a more complete understanding of the pharmacological properties underlying cocaine regulation of the chronic Fras, which will assist in identifying the functional role played by these proteins in cocaine action.

Animals↗

[A comparative analysis of UMUDC-dependent induction of tandem duplications, point and insertional reversions in Salmonella].

Comparative analysis of UV induction of tandem chromosome (Mtc+) duplications and reversions of point mutations (base pair substitutions) and of insertion mutations (precise excision of Tn10) was carried out. Salmonella (umuST) genes deficiency preventing dose-dependent UV induction of point mutation reversion were shown to have a less pronounced effect on the induction of tandem chromosome duplications. UV induction of tandem chromosome duplications is similar to UV induction of insertion mutation reversion: dose-dependent UV induction of both occurs in umuST Salmonella strains. E. coli umuDC+ genes included in Salmonella genome appreciably enhance the UV induction of both tandem duplications and insertion mutation reversion. The presence of umuDC+ genes ensures an expressed dose-dependent UV induction of point mutation reversion.

Chromosome Aberrations↗

Outcome of cadaveric renal transplantation by induction treatment in the cyclosporine era.

A total of 358 cadaveric renal transplantations performed between 1984 and 1993 received induction therapy with Minnesota antilymphoblast globulin (MALG) 95, muromonab-CD3 (OKT3) 58, antithymocyte globulin--Upjohn (ATGAM) 104, rabbit antithymocyte serum (RATS) 37, or cyclosporine (CyA) 64. There were no differences in age, gender, HLA mismatches and maintenance immunosuppression between these groups of recipients. A significantly higher proportion of OKT3 induction patients were retransplants (50%, p < 0.0001). There were fewer diabetic recipients in the group that received RATS (8%) compared to the other groups (p = 0.0009). There was no significant difference in overall graft survival with the various forms of induction treatment (log rank test, p = 0.48). Similarly, primary cadaveric graft outcome was not different with various forms of induction treatment (p = 0.62). Acute rejection was higher with ATGAM, occurring in 65% of patients, compared to MALG (52%), OKT3 (55%), RATS (43%) and CyA (55%). A significantly lower number of patients were rejection-free with ATGAM (35%) compared to MALG (48%) (p = 0.04). Patients who received ATGAM induction also had a higher rate of rebound rejection. Patients receiving ATGAM induction had a significantly higher serum creatinine level at 1 and 6 months post-transplantation (p < 0.005) compared to other induction treatments. In conclusion, the prevalence of acute rejection was higher with ATGAM, which was also reflected by higher serum creatinine levels. However, the long-term graft function and survival were not different with the various induction treatments.

Adult↗

Induction paclitaxel and carboplatin followed by concurrent chemoradiotherapy in patients with unresectable, locally advanced non-small cell lung carcinoma: report of Fox Chase Cancer Center study 94-001.

The paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ)/carboplatin combination has demonstrated promising activity in patients with incurable non-small cell lung cancer (NSCLC). Our exploratory study is designed to evaluate the efficacy of this combination as induction therapy in patients with locally advanced NSCLC, to determine the maximally tolerated doses of paclitaxel and carboplatin administered every 3 weeks during radical thoracic radiation after induction treatment, and to determine the efficacy of granulocyte colony-stimulating factor (G-CSF) priming before induction treatment, followed by conventional G-CSF, compared with conventional G-CSF alone. Eligibility stipulated Karnofsky performance status > or =70%, < or =5% weight loss, and stages IIIB or bulky IIIA NSCLC. Induction treatment consisted of two cycles of paclitaxel 175 to 225 mg/m2 infused over 3 hours combined with carboplatin (target area under the concentration-time curve of 7.5) given on days 1 and 22. On days 2 through 15 and 23 through 36, all patients received G-CSF 5 microg/kg; half were randomized to receive priming G-CSF daily for 5 days before day 1 of treatment. On day 43, thoracic radiation (60 Gy in 30 2-Gy fractions daily, 5 days a week for 6 weeks) was initiated. At dose level 1, patients received carboplatin dosed to a target area under the concentration-time curve of 3.75 and paclitaxel 67.5 mg/m2 over 3 hours on days 43 and 64. In the absence of dose-limiting toxicity, phase I escalation in three-patient cohorts proceeded to a maximum carboplatin area under the concentration-time curve of 5.0 and a paclitaxel dose of 175 mg/m2, delivered over 3 hours. To date, 35 patients (83% stage IIIB) have received induction treatment, 29 of whom are evaluable for response. Myelosuppression and neurotoxicity have been mild during induction treatment, prompting a paclitaxel dose increase to 225 mg/m2 on days 1 and 22 after the first seven patients were accrued. The phase III portion of the study evaluating G-CSF priming remains coded. Sixteen patients have received concurrent thoracic radiation and chemotherapy and are evaluable for response and toxicity. In sequential cohorts, the paclitaxel dose on days 43 and 64 has been escalated to 175 mg/m2 with only one episode each of grade 4 granulocytopenia and grade 3 anemia. In the first 13 patients evaluated, the severity of esophagitis corresponded to the length of the esophagus in the radiation treatment field: grade 1 in all six patients with esophageal exposure < or =16 cm and grade > or =2 in six of seven patients with > or =16 cm of the esophagus irradiated. Three episodes of grade > or =2 steroid-responsive pulmonary toxicity have occurred 2 to 6 months after the conclusion of concurrent thoracic radiation and chemotherapy. The major response rate is 38% to induction treatment and 59% to combined-modality treatment. Of the first 21 patients accrued, 62% survived 1 year. Induction paclitaxel/carboplatin therapy is active and well tolerated by patients with locally advanced NSCLC. The maximum tolerated doses of paclitaxel and carboplatin during concurrent thoracic radiation and the role of G-CSF priming are not yet established. Severity of esophagitis corresponds to the extent of esophagus irradiated during concurrent thoracic radiotherapy and chemotherapy.

Adult↗

Cyclosporine for induction of remission in Crohn's disease.

BACKGROUND: Cyclosporine was first found to be an effective and well-tolerated immunosuppressive agent in organ transplant recipients, and subsequently in several autoimmune diseases. It was reported in open studies that cyclosporine is effective for induction of remission in Crohn's disease. Four randomized controlled trials have been performed to determine whether the results observed in these open studies were valid. This systematic review summarizes the evidence on the use of oral cyclosporine for the induction of remission in Crohn's disease. OBJECTIVES: To evaluate the effectiveness of oral cyclosporine for induction of remission in patients with active Crohn's disease in the presence and absence of concomitant steroid therapy. Secondary objectives were to evaluate clinical response rates and adverse events associated with cyclosporine. SEARCH STRATEGY: Computer-assisted searches of the on-line bibliographic databases MEDLINE and EMBASE were performed to identify potentially relevant publications between 1980 and July 2004. The MeSH terms "Crohn Disease" or "Inflammatory Bowel disease" and "Cyclosporin" (exploded) were used to perform key word searches of the databases. Manual searches of reference lists from potentially relevant papers were performed in order to identify additional studies that may have been missed. Abstracts from major gastroenterological meetings, The Cochrane Central Register of Controlled Trials and the Cochrane Inflammatory Bowel Disease Group Specialized Trials Register were also searched for relevant studies. Appropriate officials at Sandoz Corporation were contacted to seek information on any unpublished trials. SELECTION CRITERIA: Prospective, randomized, double-blinded, placebo-controlled trials of parallel design with treatment duration of a minimum 12 weeks comparing oral cyclosporine therapy with placebo for treatment of patients with active Crohn's disease were eligible for inclusion. DATA COLLECTION AND ANALYSIS: All data were analyzed on an intention-to-treat basis. Data were extracted from the original research articles and converted into 2x2 tables (cyclosporine vs. placebo). Where available, individual 2x2 tables for strata within studies were also used. Heterogeneity was assessed using the chi-square test (p < 0.10 was regarded as statistically significant). For non-pooled data, p-values were derived using the chi-square test. For pooled data, summary test statistics were derived using the Peto odds ratio and 95% confidence intervals. A fixed effects model was used for pooling of data. For continuous data, summary test statistics were derived using the weighted mean difference and 95% confidence intervals. The definitions of treatment success, remission and clinical improvement were set by the authors of each paper, and the data were combined for analysis only if these definitions were sufficiently similar. MAIN RESULTS: Brynskov 1989a found that patients receiving high dose cyclosporine (median 7.6 mg/kg/day) had statistically significant clinical improvement at 12 weeks compared to placebo patients. None of the other studies found any statistically significant benefit for clinical improvement or induction of remission for low dose cyclosporine treatment (5 mg/kg/day) used by itself or in combination with corticosteroids compared to placebo. Cyclosporine was associated with a significantly higher proportion of adverse events and withdrawals due to adverse events relative to placebo. AUTHORS' CONCLUSIONS: Brynskov 1989a enrolled a small number of patients and the modified clinical grading scale used in the study has not been validated in other studies. Furthermore, statistically significant clinical improvement does not imply induction of clinical remission. Indeed, Brynskov 1989a found no statistically significant differences in the mean Crohn's Disease Activity Index score at 12 weeks indicating that cyclosporine was no more effective than placebo for induction of remission in Crohn's disease. The results of this review demonstrate that low dose (5 mg/kg/day) oral cyclosporine is not effective for the induction of remission in Crohn's disease. Patients treated with low dose oral cyclosporine are more likely than placebo treated patients to experience adverse events including renal dysfunction. The use of low dose oral cyclosporine for the treatment of chronic active Crohn's disease does not appear to be justified. Oral dosing at higher levels or parenteral administration of cyclosporine have not been adequately evaluated in controlled clinical trials. Higher doses of cyclosporine are not likely to be useful for the long-term management of Crohn's disease because of the risk of nephrotoxicity and the availability of other proven interventions.

Crohn Disease↗

The role of prostaglandin E1 in ornithine decarboxylase induction by tumor promoters.

The effect of topical application of PGE on induction of ODC in mouse epidermis was measured. When direct induction of ODC by TPA was blocked by also applying indomethacin, maximum ODC activity occurred only when PGE was applied simultaneously with TPA 4 1/2 hr before killing of the mice. If either TPA or PGE was applied at other times, ODC activity decreased substantially. Induction of ODC by mezerein was blocked by indomethacin but restored by PGE, as was observed with TPA, but induction by ethyl phenylpropiolate was not affected by indomethacin or PGE. DMBA did not cause a consistent increase in ODC activity, nor was its inductive action affected by indomethacin or PGE. However, another weak inducer, acetic acid, exhibited elevated ODC activity when PGE was also applied. Inhibition by topical retinoic acid of ODC induction by TPA was partially overcome in a dose-response fashion by PGE. The results indicate that at least 2 events, elevation of PGE and another independent event, are required for induction of ODC activity. It appears that TPA causes at least 4 independent events essential for tumor promotion. A model for the events in the 2-stage tumor promotion model is proposed.

9,10-Dimethyl-1,2-benzanthracene↗

Methotrexate induction of human sulfotransferases in Hep G2 and Caco-2 cells.

Methotrexate (MTX) was the first antifolate drug developed for the treatment of cancer. It is also effective in treating inflammatory and autoimmune diseases. Sulfotransferases are phase II drug-metabolizing enzymes and their induction by hormones and endogenous molecules is relatively well known, although xenobiotic drug induction of sulfotransferases has not been well studied. In the present investigation, MTX is shown to be a xenobiotic inducer of human sulfotransferases in transformed human liver (Hep G2) and intestinal (Caco-2) cells. Following MTX treatment, various sulfotransferases were induced in both cell lines. Enzyme assay, Western blot and reverse-transcription polymerase chain reaction (RT-PCR) results demonstrated that protein and mRNA expressions of human simple phenol sulfotransferase (P-PST), human monoamine sulfotransferase (M-PST), human dehydroepiandrosterone sulfotransferase (DHEA-ST) and human estrogen sulfotransferase (EST) were induced in Hep G2 cells; M-PST and DHEA-ST were induced in Caco-2 cells. Inductions in both cell lines were dose dependent. Enzyme activity and Western blot results were in good agreement with RT-PCR results, suggesting that the induction is at the gene transcription level. Folic acid had a significantly lesser effect on sulfotransferases compared with MTX. Interestingly, the induction of different sulfotransferases by MTX was inhibited by high doses of folic acid at both protein and mRNA levels in Hep G2 cells. Methotrexate is the first antifolate and apoptosis-inducing drug to show induction of sulfotransferases in Hep G2 cells and Caco-2 cells. The inhibition by folic acid suggests a possible mechanism for MTX induction.

Animals↗

The requirement of DNA synthesis for the induction of alkaline phosphatase by bromodeoxyuridine in a derivative of the HeLa cell line.

Non-lethal concentrations of bromodeoxyuridine induce a 2- to 5-fold increase in the specific activity of alkaline phosphatase in a HeLa subclone, S3G. Experiments employing 10-hour pulses of BRdU showed that 48 hours were required before induction commenced, and that maximal induction was attained by 96 hours. Under conditions in which DNA synthesis was prevented with hydroxyurea induction did not occur. Upon removal of hydroxyurea both DNA synthesis and induction were rapidly reestablished. Furthermore, experiments employing radiolabelled BRdU demonstrated that the kinetics of the induction process paralleled the incorporation of the analogue into cellular DNA. These results indicate that DNA synthesis, or some process intimately linked to DNA synthesis, is required for the induction of alkaline phosphatase, and suggest that the mode of the induction may be through the incorporation of the analogue into cellular DNA.

Alkaline Phosphatase↗

Kinetic models of induction: II. Decreased turnover of a product or its precursor.

Reduction of the turnover rate constant for a substance or its metabolic precursor is a mechanism for induction which differs markedly in its kinetic characteristics from induction resulting from a direct stimulation of synthesis. The unique aspect of induction following inhibited turnover is that the time course of recovery from the induced to the basal state is more rapid than the time course for induction itself. A general set of kinetic equations is presented here which represents the complete chain of events for such an induction; namely the kinetics of the inducer, the kinetics of a synthesis precursor to the induced product, and the kinetics of the induced product itself. These equations have been used to simulate examples of this type of induction and resemble induction experiments from the literature.

Enzyme Induction↗