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Biomedical subjects

R Pieters

Publications and source records attributed to R Pieters.

At least 73 records · Page 4Linked to original sources
PubMed2001

Post-induction residual leukemia in childhood acute lymphoblastic leukemia quantified by PCR correlates with in vitro prednisolone resistance.

Most prognostic factors in childhood acute lymphoblastic leukemia (ALL) are informative for groups of patients, whereas new approaches are needed to predict the efficacy of chemotherapy for the individual patient. The residual leukemia following 4 weeks of induction therapy with prednisolone, vincristine, doxorubicin and i.t. methotrexate and the in vitro resistance to prednisolone, vincristine, and doxorubicin were measured in 30 boys and 12 girls with B (n = 34) or T lineage (n = 8) ALL. The residual leukemia was quantified after 2 (MRD-D15, n = 29) and 4 weeks (MRD-PI, n = 42) of induction therapy with a precise and reproducible clone-specific PCR technique. The median MRD-D15 and MRD-PI were 0.50% (75% range 0.0088.1%) and 0.014% (75% range 0.001-2.0%), respectively, and these levels correlated significantly (n = 29, rs = 0.75, P < 0.001). Both the MRD-D15 and the MRD-PI were related to the age of the patient (MRD-D15: rs= 0.48, P= 0.009; MRD-PI: rs = 0.45, P = 0.003). Patients with T lineage ALL had higher MRD-PI than those with B lineage ALL (median MRD-PI: 0.5% vs 0.01%, P = 0.05). The median LC50 (concentration lethal to 50% of cells) for prednisolone was 2.3 microg/ml (75% range 0.05-668). Both MRD-D15 and MRD-PI correlated significantly with the in vitro resistance to prednisolone (MRD-D15: rs = 0.41, P = 0.03; MRD-PI: rs = 0.39, P = 0.01); but not to in vitro vincristine or doxorubicin resistance. The correlations between MRD and in vitro prednisolone resistance were even more pronounced when B cell precursor and T cell leukemia were analyzed separately (B cell precursor ALL: MRD-PI vs prednisolone LC50: n = 33, rs = 0.47, P = 0.006; T cell ALL: MRD-PI vs prednisolone resistance: n = 8, rs = 0.84, P = 0.009). After a median follow-up of 5.0 years (75% range 3.2-6.9) eight patients have relapsed. All of the 21 patients with a MRD-PI < or =0.5% and a prednisolone LC50 < or =10 microg/ml have remained in remission whereas the 7 year event-free survival for the remaining 20 patients was 0.45 +/- 0.16 (P= 0.002) Prospective studies in childhood ALL are needed to clarify whether combined monitoring of in vitro drug resistance and residual leukemia early during chemotherapy could offer new ways to classify patients and stratify the intensity of therapy.

Adolescent↗
PubMed2001

In vitro drug resistance and prognostic impact of p16INK4A/P15INK4B deletions in childhood T-cell acute lymphoblastic leukaemia.

p16 gene deletions are present in about 70% of primary paediatric T-cell acute lymphoblastic leukaemia (T-ALL) and 20% of common/precursor B-cell ALL cases. It is not clear what the impact of the frequent p16 deletions is within the subgroup of T-lineage ALL. We studied the relationship between p16/p19ARF deletions, using fluorescence in situ hybridization, and in vitro drug resistance and prognosis in childhood T-ALL at diagnosis. The cellular drug resistance was measured with the methyl thiazol tetrazoliumbromide assay using a panel of drugs and the thymidylate synthase inhibition assay for methotrexate. There was a complete overlap of individual LC50 values of p16 gene homozygously deleted and p16 germ-line cases for most of the nine classes of drugs tested. The only difference was for dexamethasone: the p16-deleted group was more sensitive than the germ-line p16 group (P = 0.030). The homozygously deleted p16 T-ALL patients (n = 34) treated with the modern multiagent chemotherapy schemes of the Dutch Childhood Leukaemia Study Group ALL-VII/-VIII or Co-operative ALL-92/-97 protocols have a significantly lower 5-year disease-free survival (DFS) than germ-line p16 T-ALL (n = 25) (65.1 +/- 9.1% vs. 95.5 +/- 4.4%, Plog rank = 0.021). Hence, this study identifies a subpopulation of primary childhood T-ALL that appears to have an extremely high DFS. However, the observed differences in outcome do not seem to be related to intrinsic resistance for the tested drugs.

Adolescent↗
PubMed2000

Organotins induce apoptosis by disturbance of [Ca(2+)](i) and mitochondrial activity, causing oxidative stress and activation of caspases in rat thymocytes.

Di-n-butyltin dichloride (DBTC) and tri-n-butyltin chloride (TBTC) cause thymus atrophy in rodents. At low doses, antiproliferative modes of action have been shown to be involved, whereas at higher doses apoptosis seems to be the mechanism of thymotoxicity by these chemicals. In vitro, a similar concentration-dependency has been observed. The purpose of the present research was to investigate the mechanisms underlying DNA fragmentation induced by these organotin compounds in freshly isolated rat thymocytes. As previously shown for TBTC, DBTC is also able to significantly increase intracellular Ca(2+) level ([Ca(2+)](i)). The rise in [Ca(2+)](i), already evident 5 min after treatment, was followed by a dose- and time-dependent generation of reactive oxygen species (ROS) at the mitochondrial level. Simultaneously, organotins induced the release of cytochrome c from the mitochondrial membrane into the cytosol. ROS production and the release of cytochrome c were reduced by BAPTA, an intracellular Ca(2+) chelator, or rotenone, an inhibitor of the electron entry from complex I to ubiquinone, indicating the important role of Ca(2+) and mitochondria during these early intracellular events. Furthermore, we demonstrated that rotenone prevents apoptosis induced by 3 microM DBTC or TBTC and, in addition, that both BAPTA and Z-DEVD FMK (mainly a caspase-3 inhibitor) decreased apoptosis by DBTC (already shown for TBTC). Taken together these data show the apoptotic pathway followed by organotin compounds starts with an increase of [Ca(2+)](i), then continues with release of ROS and cytochrome c from mitochondria, activation of caspases, and finally results in DNA fragmentation.

Animals↗
PubMed2000

Diesel exhaust, carbon black, and silica particles display distinct Th1/Th2 modulating activity.

Certain particulate air pollutants may play an important role in the increasing prevalence of respiratory allergy by stimulating T helper 2 cell (Th2)-mediated immune responses to common antigens. The study described here examined different particles, diesel exhaust particles (DEP), carbon black particles (CBP), and silica particles (SIP) for their immunomodulating capacity in both primary and secondary immune responses in female BALB/C mice. The primary response was studied after subcutaneous injection of 1 mg of particle together with 10 microgram of reporter antigen TNP-OVA (2,4,6-trinitrophenyl coupled to ovalbumin) into the hind paw. Interferon-gamma (IFN-gamma) and interleukin 4 (IL-4) production was assessed in the popliteal lymph node (PLN) at Day 2 and Day 5 after injection by flow cytometry and ELISA. The number of IL-4-containing CD4(+) T cells increased between Day 2 and Day 5 in DEP- and CBP-exposed mice, in contrast to SIP-treated animals. IL-4 production by cultured PLN cells was also significantly increased for DEP- and CBP-treated animals. The secondary response was studied in different organs after an intranasal challenge with TNP-OVA (50 microgram), which was given 4 weeks after the initial subcutaneous injection. Five days after challenge the number of antibody-forming cells (AFCs) was assessed in peribronchial lymph nodes (PBLN), spleen, bone marrow, and PLN, and antibody levels were determined in weekly obtained blood samples. It appeared that all particles acted as adjuvant, but the different particles stimulated distinct types of immune responses to TNP-OVA. DEP-treated animals show high IgG1 and IgE levels in serum and high IgG1 and IgE-forming AFC numbers in PBLN, bone marrow, and spleen. CBP-treated animals show even higher IgG1 and IgE levels and AFC numbers, and in addition display IgG2a production. SIP-injected animals display predominantly IgG2a responses. It is concluded that DEP are able to skew the immune response toward the T helper 2 (Th2) side, whereas SIP stimulate a Th1 response and CBP have a mixed activity, stimulating both Th1 and Th2 responses in this model.

Adjuvants, Immunologic↗
PubMed2000

Cellular drug resistance profiles in childhood acute myeloid leukemia: differences between FAB types and comparison with acute lymphoblastic leukemia.

Determining in vitro drug resistance may reveal clinically relevant information in childhood leukemia. Using the methyl-thiazol-tetrazolium assay, the resistance of untreated leukemic cells to 21 drugs was compared in 128 children with acute myeloid leukemia (AML) and 536 children with acute lymphoblastic leukemia (ALL). The differences between 3 French-American-British (FAB) types (M1/M2, M4, and M5) were also compared. AML was significantly more resistant than ALL to the following drugs, as noted by the median resistance: glucocorticoids (greater than 85-fold), vincristine (4.4-fold), L-asparaginase (6.9-fold), anthracyclines (1.8- to 3.4-fold), mitoxantrone (2.6-fold), etoposide (4.9-fold), platinum analogues (2.4- to 3.4-fold), ifosfamide (3.5-fold), and thiotepa (3.9-fold). For cytarabine and thiopurines, the median LC50 values (the drug concentration that kills 5% of the cells) were equal. Also, busulfan, amsacrine, teniposide, and vindesine showed no significant differences, but the numbers were smaller, and the median LC50 values were 1.3- to 5.2-fold higher in AML. None of the drugs demonstrated greater cytotoxicity in AML. FAB M5 was significantly more sensitive than FAB M4 to most drugs frequently used in AML, as indicated by the following ratios of median sensitivities: the anthracyclines (2.6- to 3.2-fold), mitoxantrone (12.5-fold), etoposide (8.7-fold), and cytarabine (2.9-fold). For etoposide and cytarabine (5.4- and 3.4-fold, respectively) FAB M5 was also significantly more sensitive than FAB M1/M2. FAB M5 was equally sensitive to L-asparaginase and vincristine as ALL. Only 15% of the AML samples were "intermediately" sensitive to glucocorticoids, mainly in FAB M1/M2. The poorer prognosis of childhood AML is related to resistance to a large number of drugs. Within AML, FAB M5 had a distinct resistance pattern. These resistance profiles may be helpful in the rational design of further treatment protocols. (Blood. 2000;96:2879-2886)

Acute Disease↗
PubMed2000

TEL/AML1 gene fusion is related to in vitro drug sensitivity for L-asparaginase in childhood acute lymphoblastic leukemia.

The t(12;21) translocation resulting in TEL/AML1 gene fusion is present in approximately 25% of patients with precursor B-lineage pediatric acute lymphoblastic leukemia (ALL). Studies suggest an association with a good prognosis; however, relapse can occur. We studied the relation between t(12;21), determined by fluorescence in situ hybridization or polymerase chain reaction, and in vitro drug resistance, measured by the MTT assay, in childhood B-lineage ALL at diagnosis. A total of 180 ALL samples were tested, 51 (28%) of which were positive for t(12;21). The median LC(50) values did not differ significantly between TEL/AML1-positive and -negative samples for prednisolone, dexamethasone, daunorubicin, thiopurines, epipodophyllotoxins, and 4-HOO-ifosfamide. However, the TEL/AML1-positive patients were relatively more sensitive to L-asparaginase (ASP; 5.9-fold; P =.029) and slightly but significantly more resistant to vincristine (1.5-fold; P =.011) and cytarabine (1.5-fold; P =.014). After matching for unevenly distributed patient characteristics-that is, excluding patients younger than 12 months, patients with CD10-negative immature B-lineage ALL, patients with Philadelphia chromosome, and patients who were hyperdiploid (more than 50 chromosomes) from the TEL/AML1 negative group-the only remaining difference was a relative sensitivity for ASP in the TEL/AML1-positive samples (10.8-fold; P =. 012). In conclusion, the presence of TEL/AML1 gene fusion in childhood precursor B-lineage ALL does not seem to be associated with a high in vitro drug sensitivity, except for ASP, indicating that these patients could benefit from treatment schedules with significant use of this drug.

Antineoplastic Agents↗
PubMed2000

The popliteal lymph node assay in predictive testing for autoimmunity.

A large number of chemicals or metabolites thereof is known to induce or exacerbate autoimmune disease (AID) in man. Due to the complex immunological processes involved, chemical-induced autoimmunity is hardly if ever detected in standard toxicity testing and generally applicable animal models that detect a chemical's potential to induce AID do not exist. The popliteal lymph node assay (PLNA) focusses on the chemical's ability to initiate an immune response rather than on inducing or exacerbating autoimmune reactions, and is regarded a suitable test for pre-screening of immunostimulating and -sensitizing potential. The most simple primary PLNA measures enlargement of the popliteal lymph node (PLN) 6-8 days after subcutaneous injection of a chemical into the footpad distinguishes between immunostimulating and innocent chemicals. The primary PLNA is however unable to assess the involvement of T cells and thus the immunosensitizing potential of a chemical. For this, the secondary and/or modified PLNA is appropriate. The secondary PLNA detects challenge reactions in the PLN to non-sensitizing doses of a chemical in pre-sensitized animals or in unsensitized animals that received an adoptive transfer of pre-sensitized syngeneic T cells. The modified PLNA uses the defined reporter antigens TNP-OVA (T cell-dependent antigen) and TNP-Ficoll (T cell-independent antigen) to distinguish sensitizing from non-sensitizing (IgG1-response or not to TNP-Ficoll) and mere inflammatory from complete innocent (IgG1-response or not to TNP-OVA) chemicals. To date, about 130 compounds (drugs and environmental pollutants) have been tested in either one or more of these PLNAs. Results show a good correlation with documented immunostimulating (both autoimmunogenic and allergic) potential and no false negative chemicals were detected if metabolism was considered. In particular the modified PLNA awaits validation before it can be recommended as a standard test for autoimmunogenic potential.

Animals↗
PubMed2000

mRNA expression levels of methotrexate resistance-related proteins in childhood leukemia as determined by a standardized competitive template-based RT-PCR method.

Drug resistance of leukemic blasts is correlated to event-free survival and might be predicted by mRNA expression of drug resistance-related proteins. Methotrexate (MTX) is an important component in the treatment of childhood leukemia. Mechanisms of MTX resistance include (1) decreased transport via the reduced folate carrier (RFC), (2) altered levels of target enzymes, eg dihydrofolate reductase (DHFR) and thymidylate synthase (TS), (3) decreased ratio of folylpolyglutamate synthetase (FPGS)/folylpolyglutamate hydrolase (FPGH). We designed competitive templates for each of these genes to measure mRNA expression by quantitative RT-PCR and normalized the expression to that of beta-actin. T-lineage acute lymphoblastic leukemia (T-ALL), relatively MTX resistant compared to common/preB-ALL, displayed higher mRNA levels of DHFR and TS (three- and four-fold higher, respectively; P < 0.001), while FPGS expression was lower (three-fold, P = 0.006) compared to common/preB-ALL. The ratio of (DHFR x FPGH)/(RFC x FPGS) was more discriminating between T-ALL and c/preB-ALL (eight-fold higher; P < 0.001) than either target independently. Acute myeloid leukemia (AML) cells, considered MTX resistant, expressed two-fold lower levels of FPGS mRNA compared to c/preB-ALL (P = 0.04). The ratio of FPGH/FPGS was more discriminating between AML and c/preB-ALL (four-fold higher; P = 0.001) than either target independently. For the total group of 79 leukemic samples, mRNA expression of DHFR varied 549-fold and paralleled TS mRNA expression (r = 0.80; P < 0.001). Although variations in mRNA expression resembled variations in functional activity, no direct correlations were found for RFC (58-fold variation in mRNA expression), FPGS (95-fold) and FPGH (178-fold). In conclusion, differences in mRNA expression of MTX resistance parameters between leukemic subtypes as detected by competitive RT-PCR are in line with known differences in MTX resistance.

Antimetabolites, Antineoplastic↗
PubMed2000

Asparagine synthetase activity in paediatric acute leukaemias: AML-M5 subtype shows lowest activity.

Lack of sufficient cellular activity of asparagine synthetase (AS) in blast cells compared with normal tissue is thought to be the basis of the antileukaemic effect of L-asparaginase in acute lymphoblastic leukaemia (ALL). Although L-asparaginase is routinely used in ALL, its role and value in the treatment of acute myelogenous leukaemia (AML) is still being discussed. To evaluate the pharmacological basis for L-asparaginase treatment, we established pretreatment monitoring of the intracellular AS activity in blast cells of patients with AML and ALL. There was no general difference in AS activity between ALL and AML samples. Significantly lower AS activity, however, was found in the B-lineage ALL subgroups as well as AML-M5.

Adolescent↗
PubMed2000

Methotrexate resistance in relapsed childhood acute lymphoblastic leukaemia.

Treatment failure in childhood acute lymphoblastic leukaemia (ALL) might be associated with methotrexate (MTX) resistance. Little is known about MTX resistance in relapsed ALL. In this study, we determined ex vivo MTX resistance in precursor-B ALL at relapse (rALL) and determined possible defects in MTX membrane transport and polyglutamylation. Using the in situ thymidylate synthase inhibition assay, 21 rALL samples were threefold more MTX resistant than 63 initial precursor-B ALL samples, both after short-term and after continuous MTX exposure (P < or = 0.01). [3H]-MTX membrane transport did not differ between eight rALL and 25 precursor-B ALL samples. Incubation for 24 h with 1 microM [3H]-MTX resulted in a trend towards a lower accumulation of MTX in 20 relapsed than in 83 initial samples of precursor-B ALL samples (906 vs. 1364 pmol/109 cells; P = 0.07). Accumulation of long-chain MTX polyglutamates (MTX-Glu4-6) did not differ between relapsed and newly diagnosed samples (746 and 889 pmol/109 cells; P = 0.1). Activities of the enzymes involved in polyglutamylation (folylpolyglutamate synthetase and folylpolyglutamate hydrolase) did not differ between rALL and untreated c/pre-B-ALL. This study demonstrates that leukaemic cells of children with relapsed precursor-B ALL are relatively MTX resistant, but that this MTX resistance is not associated with major impairments in MTX uptake or polyglutamylation.

B-Lymphocytes↗
PubMed2000

In vitro drug resistance profiles of adult versus childhood acute lymphoblastic leukaemia.

The difference in the current cure rates between adult and childhood acute lymphoblastic leukaemia (ALL) may be caused by differences in drug resistance. Earlier studies showed that in vitro cellular drug resistance is a strong independent adverse risk factor in childhood ALL. Knowledge about cellular drug resistance in adult ALL is still limited. The present study compared the in vitro drug resistance profiles of 23 adult ALL patients with that of 395 childhood ALL patients. The lymphoblasts were tested by the MTT assay. The group of adult ALL samples was significantly more resistant to cytosine arabinoside, L-asparaginase, daunorubicin, dexamethasone and prednisolone. The resistance ratio (RR) was highest for prednisolone (31.7-fold) followed by dexamethasone (6.9-fold), L-asparaginase (6. 1-fold), cytosine arabinoside (2.9-fold), daunorubicin (2.5-fold) and vincristine (2.2-fold). Lymphoblasts from adult patients were not more resistant to mercaptopurine, thioguanine, 4-HOO-ifosfamide, mitoxantrone and teniposide. There were no significant differences in drug resistance between adult T-cell (T-) ALL (n = 11) and adult common/pre-B-cell (B-) ALL (n = 10). Additionally, adult T-ALL did not differ from childhood T-ALL (n = 69). There were significant differences between adult common/pre-B-ALL and childhood common/pre-B-ALL (n = 310) for prednisolone (RR = 302, P = 0.008), dexamethasone (RR = 20.9, P = 0.017) and daunorubicin (RR = 2.7, P = 0.009). Lymphoblasts from adults proved to be relatively resistant to drugs commonly used in therapy. This might contribute to the difference in outcome between children and adults with ALL.

Adolescent↗
PubMed2000

The prognostic significance of membrane transport-associated multidrug resistance (MDR) proteins in leukemia.

A major problem in the treatment of leukemia is the development of resistance to chemotherapeutic agents. There are several ways for cancer cells to develop resistance or defense mechanisms against cytotoxic drugs. This review paper will focus on membrane transport-associated multidrug resistance (MDR). The proteins involved, P-glycoprotein (P-gp), MRP1 and LRP/MVP, share the ability to act as drug transport proteins. Following upregulation of the mdr-1 gene, the energy-dependent transmembrane P-gp overexpression results in diminished intracellular concentrations of anthracyclins, vinca-alkaloids and epipodophyllotoxins. The other transmembrane protein, MRP1, also has intracellular epitopes which are involved in intracellular redistribution and sequestration of drugs. The last named mechanism has also been ascribed to LRP, a protein which only occurs intracellularly. In leukemia patients, cellular drug resistance profiles determined in vitro at the time of presentation show a strong correlation with outcome. In AML, mdr-1 overexpression at diagnosis is a strong independent predictor for CR and long-term survival. In ALL, mdr-1 expression is of minor importance for prediction of outcome. In AML, MRP1 expression at diagnosis is not correlated with clinical response and survival in most studies. In ALL, MRP1 expression at diagnosis is not associated with response and long-term survival in the few studies on this aspect which have been published. The studies on LRP in AML emphasize the importance of the correlation between LRP-expression and anthracycline accumulation and suggest that LRP-expression has prognostic value at diagnosis. However, there is an equal number of studies where a predictive value in the case of LRP-expression in de novo AML cannot be shown. The highest levels of LRP have been reported in multiple relapses of ALL. Furthermore, new membrane-associated drug transport proteins have been reported including the transporter associated with antigen processing (TAP), the anthracyclin resistance-associated protein (ARA), five new homologues of MRP (MRP2, or MOAT, MRP3, MRP4, MRP5, and MRP6), the sister of P-glycoprotein (sP-gp) and breast cancer resistance protein (BCRP). Studies on the (clinical) significance of these proteins have not yet been reported.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1999

Circumvention of methotrexate resistance in childhood leukemia subtypes by rationally designed antifolates.

Cellular methotrexate (MTX) resistance may cause treatment failure in childhood common/preB-acute lymphoblastic leukemia (c/preB-ALL), T-lineage ALL (T-ALL), and acute myeloid leukemia (AML). The ex vivo potency of several antifolates (MTX, trimetrexate [TMQ], GW1843U89, multitargeted antifolate [MTA], Raltitrexed, and ZD9331) was studied via in situ inhibition of thymidylate synthase (TS). After short-term exposure, relapsed c/preB-ALL (rALL, n = 21), T-ALL (n = 22), and AML (n = 22) were 3-fold, 10-fold, and 6-fold less sensitive to MTX (P </=.01) compared with initial c/preB-ALL (n = 43). This difference in resistance was not observed for TMQ. Also for GW1843U89 and MTA, no resistance was observed in rALL and AML compared with c/preB-ALL. T-ALL compared with c/preB-ALL tended to be less resistant to GW1843U89 (3-fold) and MTA (6-fold) than to MTX (10-fold) (P =.06). Raltitrexed was more active against c/preB-ALL compared with the other subtypes. After 21 hours continuous incubation, T-ALL and AML samples were equally sensitive as c/preB-ALL to MTX, but rALL was 3-fold resistant to MTX compared with initial c/preB-ALL (P =.003). The resistance of rALL was circumvented by TMQ (1-fold; P =.03) and GW1843U89 (1.4-fold; P =. 004). Novel antifolates, except MTA, displayed a more potent TS inhibition than MTX during continuous exposure. These results suggest that MTX resistance in AML and T-ALL can be circumvented by continuous exposure, and that novel antifolates should be explored further for MTX-resistant T-ALL, rALL, and AML cells.

Antimetabolites, Antineoplastic↗
PubMed1999

Distinct immunomodulation by autoimmunogenic xenobiotics in susceptible and resistant mice.

HgCl(2) and diphenylhydantoin (DPH) are prototype chemicals associated with diverse (auto)immune effects in genetically susceptible individuals. Both chemicals activate T cells, and the balance of Th1 versus Th2 activation may influence the clinical outcome of exposure. It is unknown which chemically created neoantigens are responsible for Th activation. We therefore investigated the effect of DPH and HgCl(2) on specific responses to TNP-ovalbumin, in mouse strains with varying sensitivity for the adverse effects. HgCl(2) was found to enhance Th2-driven antibody responses in susceptible B10.s, but protective type 1 responses in resistant B10.d2 mice. This was chemical-specific, as DPH enhanced type 2 responses in both strains. DBA/2 mice were relatively unresponsive to HgCl(2), whereas DPH stimulated type 1 responses in these mice. Interestingly, prior exposure to HgCl(2), but not DPH, facilitated IC deposition in B10.s mice only. Thus, we demonstrate that, depending on MHC-II and background genes, HgCl(2) and DPH preferentially adjuvate type 1 or type 2 responses. In case of HgCl(2), the type of response corresponds with susceptibility to antibody-mediated autoimmunity induced by this chemical. In addition, we demonstrate that, within one strain, different autoimmunogenic chemicals can enhance distinct responses to the same antigen.

Adjuvants, Immunologic↗
PubMed1999

Cytotoxicity and aromatase (CYP19) activity modulation by organochlorines in human placental JEG-3 and JAR choriocarcinoma cells.

The human placental JEG-3 and JAR choriocarcinoma cell lines have been used as placental models for the study of aromatase (CYP19) activity and endocrine functions. In the present study, 21 organochlorines (OCs) mediated decreases in aromatase activity and protein and DNA content and increases in the percent lactate dehydrogenase (LDH) leakage in JEG-3 cells. These effects were highly variable among the types of OC and their treatment concentrations. Lowest observed effective concentrations reached 0. 001 microM for several OCs. Aromatase activity decreases and OC-mediated cytotoxicity were related. Thus, it was not possible to clearly assess the capacity of the OCs to modulate aromatase activity. Similar to 1,4-naphthoquinone, the most cytotoxic OCs contained a hydroxyl (4'-OH-2,4,6-trichlorobiphenyl and tris(4-chlorophenyl)methanol) or methylsulfonyl- (3- and 4-MeSO(2)-2, 2',5,5'-tetrachlorobiphenyl and -2,3',4',5-tetrachlorobiphenyl, and 3'- and 4'-MeSO(2)-2,2',3,4,5'-pentachlorobiphenyl and -2,2',4,5, 5'-pentachlorobiphenyl) functional group. Modulation of aromatase activity and LDH leakage were less for 3,3',4,4', 5-pentachlorobiphenyl and benzo[a]pyrene and insignificant for five alkyl-substituted trichloro-dibenzofurans and 2,3,7, 8-tetrachloro-dibenzo-p-dioxin (up to 10 microM). Cytotoxicity-related effects were influenced by the cell density and the presence of 10% fetal calf serum in the medium during compound incubation. Similar cytotoxic effects were observed for the JAR cell line. The involvement of an apoptotic mechanism of cytotoxicity in OC-treated JEG-3 cells was suggested by the binding of APO2.7 (an antibody specific to apoptotic cells), DNA fragmentation, and trypan blue staining. JEG-3 and JAR cells appear too sensitive toward OC-mediated cytotoxicity for use as in vitro bioassays to evaluate the potential modulation of aromatase activity. However, these cell lines may prove useful for examining the capacity of xenobiotics to modulate placental toxicity.

Apoptosis↗