Biomedical subjects

H M Pinedo

Publications and source records attributed to H M Pinedo.

At least 19 recordsLinked to original sources

PubMed1992

Determination of the immunoreactive fraction of radiolabeled monoclonal antibodies directed against intracellular antigens.

For investigations involving monoclonal antibodies (mAbs) against cellular antigens cell binding assays are routinely used to determine the immunoreactive fraction after radiolabeling. In general, surface antigens are targets for radioimmunodetection, but recent studies indicate that intracellular determinants may also prove useful for this purpose. Thus, there is a need to adapt the regular cell binding assay for use with antibodies directed against cytoplasmic antigens. Here we describe a fixation method which permits such mAbs to bind to cell surfaces as well as to intracellular determinants. Moreover, the procedure may be used for antigens that are sensitive to the commonly used aldehyde fixatives. The method is illustrated with two human IgM mAbs 16.88 and 28A32, which recognize cytoplasmic antigens. Human colon cancer cells in suspension were fixed with either acetone or glutaraldehyde. Intracellular antigens appeared to be best exposed for antibody binding after fixation with acetone as determined by immunofluorescent staining and flow cytometry. An antibody directed against the cell surface antigen HLA class I showed similar binding with both live cells and acetone-fixed cells. Double-inverse plots of the binding of radiolabeled 16.88 or 28A32 antibody with acetone-fixed cells gave reliable immunoreactive fraction values. Acetone-fixed cells stored at 4 degrees C could be used for immunoreactivity assays for at least 6 months without loss of performance.

Acetone↗

PubMed1992

Elevation of thymidylate synthase following 5-fluorouracil treatment is prevented by the addition of leucovorin in murine colon tumors.

The inhibition of thymidylate synthase (TS) by the 5-fluorouracil (5FU) metabolite 5-fluorodeoxyuridine monophosphate can be biochemically modulated by leucovorin (LV). LV administration increases the level of reduced folates in tissues, which promotes the inhibition of TS. We have studied the antitumor effect, free 5-fluorodeoxyuridine monophosphate levels, and inhibition of TS in two murine colon tumors at several time points after weekly 5FU or LV and 5FU administration. The antitumor effect of 5FU alone could be potentiated by LV in both tumors. 5-Fluorodeoxyuridine monophosphate levels (212 and 46 pmol/g wet wt. after 2 h for Colon 26 and Colon 38, respectively) were sufficient to mediate TS inhibition, but the levels were not related to antitumor activity. Untreated controls of the 5FU-sensitive tumor Colon 38 had 3 times lower TS levels than did those of the more resistant tumor Colon 26. One course of treatment resulted in a comparable extent and retention of TS inhibition for 5FU and LV/5FU therapy in both tumors. After 1 week there was complete recovery of TS inhibition, but the TS levels in tumors from 5FU-treated mice tended to be higher than the controls, which was more pronounced after three courses of therapy. A 4-fold increase of TS levels was seen in Colon 26 after 5FU therapy. The elevation of TS in this tumor affected the extent of TS inhibition. Tumors treated with 5FU and LV also showed an increase of TS, but to a lesser extent, while the absolute effect on TS inhibition remained the same. This might be related to the potentiating effect of LV on 5FU antitumor activity in vivo in these tumors.

Animals↗

PubMed1992

The effect of schedule, protein binding and growth factors on the activity of suramin.

Suramin has been shown to have antiproliferative activity, either by blocking the binding of growth factors to their receptors or by inhibiting critical cellular enzymes. In 6 different cell lines from 5 tumour types (MCF-7, MCF-7/ADRR, PC3, HT-29, UM-SCC-11B and SW-1573/IR500), we studied the effect of scheduling of suramin, of FCS and of human serum albumin (HSA), of epidermal growth factor (EGF) and of the addition of growth factors in serum-free medium on the activity of suramin. The concentration of suramin which gave 50% growth inhibition (IC50) varied from 45 microM in SW-1573/IR500 to 153 microM in PC3 cells grown in medium supplemented with 5% FCS, after 6 days of continuous exposure. Exposure for more than 4 days did not enhance the sensitivity to suramin, except in PC3. At exposure to suramin for 1 day followed by 5 days recovery, high IC50 values (greater than 0.5 mM) were observed in MCF-7 cells. In medium with 1% and 0.5% FCS these values were 3 to 8 and 14 to 26 times lower respectively. Addition of HSA increased the IC50 in PC3 and MCF-7 cells. Suramin binding to protein was dependent on the concentration of protein and of suramin. Excess of EGF in medium with different FCS concentrations did not change the IC50 values of suramin in PC3 and MCF-7 cells. Addition of EGF, fibroblast growth factor or platelet-derived growth factor in PC3 cells cultured in serum-free medium did not increase the IC50 values. Suramin was active against these 6 cell lines at clinically achievable concentrations. This activity varied depending on the cell line, exposure time and suramin concentration. The most significant factor interfering with sensitivity to suramin was the amount of protein present in the culture medium.

Blood↗

PubMed1992

Comparison of 131I-labelled anti-episialin 139H2 with cisplatin, cyclophosphamide or external-beam radiation for anti-tumor efficacy in human ovarian cancer xenografts.

Three human ovarian cancer xenografts of different origin and grown s.c. in nude mice as well-established tumors were studied for their sensitivity to cisplatin (CDDP), cyclophosphamide (CTX), 131I-labelled anti-episialin monoclonal antibody (MAb) 139H2, or external-beam radiotherapy. The maximum tolerated dose of CDDP given weekly i.v. x 2 induced a tumor growth inhibition (GI) of 77.5% and 85.1% of the serous xenografts Ov.Ri(C) and OVCAR-3, respectively. The mucinous xenograft Ov.Pe was relatively resistant to CDDP. The maximum tolerated dose of CTX, given i.p. x 2 with a 2-week interval, induced a GI between 52.9% and 59.7% for each of the 3 xenografts. Radioimmunotherapy with 500-750 microCi 131I-specific MAb 139H2, administered i.v. x 2 with a 2-week interval, was more effective than CDDP or CTX. The 500 microCi 131I-MAb 139H2 schedule induced 100% GI in Ov.Ri(C) xenografts and all tumors were cured. The same schedule was slightly less effective in OVCAR-3 xenografts, but complete tumor regressions could still be obtained. Ov.Pe xenografts were least sensitive to radioimmunotherapy. The 2 injections of 500 microCi 131I-control MAb gave only transient growth inhibition of OVCAR-3 and Ov.Pe tumors, but gave complete regressions of Ov.Ri(C) xenografts. Biodistribution using tracer doses of 131I-MAb 139H2 and 125I-control MAb showed different degrees of specificity for MAb 139H2 in the 3 xenografts. Radiation doses absorbed in OV.Ri(C), OVCAR-3 and Ov.Pe xenografts per 10 microCi injected dose were 30, 41 and 29 cGy respectively. Treatment with 10 Gy external-beam radiation suggested that the effects of radioimmunotherapy in each tumor line were related to the intrinsic radiosensitivity of the xenografts.

Animals↗

PubMed1992

Time dependence of the selective modulation of cisplatin-induced nephrotoxicity by WR2721 in the mouse.

2-(3-Aminopropylamino)ethylphosphorothioic acid (WR2721; ethiofos) was shown to selectively protect nontumor tissues from cis-diamminedichloroplatinum(II) (cisplatin)-induced toxicity, when administered 30 min prior to the platinum drug. Selectivity of protection by WR2721 is probably due to the preferential formation and uptake of the thiol metabolite 2-(3-aminopropylamino)ethanethiol (WR1065), which can inactivate toxic platinum-species inside the cell. We investigated the protective potential of WR2721, when administered at different time points relative to cisplatin. BALB/c mice treated with WR2721 (200 mg/kg i.p.) either 30 min or 5 min prior to cisplatin (i.p.) allowed a 2.2-fold increase in cisplatin dose to 19 mg/kg before the occurrence of nephrotoxicity as expressed by an increase in plasma urea. A small part of the protection could be ascribed to the mannitol (200 mg/kg), present in the formulated WR2721. WR2721 (200 mg/kg) 30 min after 14.5-16-mg/kg cisplatin did not offer any protection against the rise in plasma urea. WR2721 (200 mg/kg) 5 min before 19-mg/kg cisplatin did not cause liver toxicity (increase in serum glutamic pyruvic transaminase or serum glutamic oxaloacetic transaminase). Furthermore, WR2721 (200 mg/kg) 5 min prior to cisplatin did not reduce antitumor activity in nude mice bearing well-established human ovarian cancer xenografts. Under protection of WR2721, the dose of cisplatin could be increased by a factor of 1.6 to 8 mg/kg (administered twice weekly), resulting in an increased antitumor activity.

Amifostine↗

PubMed1992

Drug-transporter proteins in clinical multidrug resistance.

Upon exposure to chemotherapeutic drugs, mammalian cells can acquire resistance to structurally and functionally unrelated compounds, a property known as multidrug resistance (MDR). One MDR mechanism, i.e. by the overexpression of a plasma membrane protein, P-glycoprotein (P-gp), has been identified at the molecular level. The mdr1 gene-encoded P-gp acts as a drug efflux pump, lowering intracellular drug concentration by active extrusion of drugs from the cell. The role of P-gp in determining clinical resistance to multiple anticancer drugs is likely to be largely different for various tumor types. Recently we selected a monoclonal antibody (mAb LRP56) for strong, granular cytoplasmic reactivity with MDR tumor cell lines without P-gp (over)expression. None or weak reactivity was observed with parental and P-gp positive cell lines. We hypothesize that as yet-undefined drug transport-mediating proteins are inserted in intracellular membranes lining the exocytotic compartment and thus may contribute to clinical multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1992

A rationale for carboplatin treatment and abdominal hyperthermia in cancers restricted to the peritoneal cavity.

The purpose of this study was to optimize the treatment of cancers restricted to the peritoneal cavity by combining i.p. chemotherapy with abdominal hyperthermia. In vitro experiments demonstrated that the uptake of carboplatin into CC531 tumor cells was increased at temperatures higher than 41.5 degrees C at dose levels of 5 and 50% cell kill. Carboplatin-DNA adduct formation and cytotoxicity, however, were already increased at temperatures of about 40 degrees C, indicating that carboplatin-DNA adduct formation and consequently cytotoxicity could be enhanced by mild hyperthermia (temperatures in the range of 39-41.5 degrees C). CC531 tumor bearing rats were treated i.v. and i.p. with carboplatin (6.15 mg/kg) in combination with regional hyperthermia of the abdomen (41.5 degrees C for 1 h). The mean temperature was 41.5 +/- 0.3 degrees C (SD) in the peritoneal cavity and 40.5 +/- 0.3 degrees C in the esophagus. Enhanced platinum concentrations were found in peritoneal tumors (factor 3) and in kidney, liver, spleen, and lung (a factor 2 average), after the combined i.v. or i.p. carboplatin-hyperthermia treatment. Pharmacokinetic data of i.p. CBDCA combined with hyperthermia demonstrated an increased tumor exposure for total and ultrafiltered platinum in plasma. The areas under the concentration x time curve for total platinum at 37 degrees C and 41.5 degrees C were 69 and 210 microM/h, respectively; for ultrafiltered platinum these values were 47 and 173 microM/h. This may have been due to a slower elimination of platinum from the blood at the higher temperature (t1/2 beta for total platinum 99 and 156 min at 37 and 41.5 degrees C, respectively). The direct exposure of the tumor via the peritoneal fluid appeared to diminish, since the area under the curve for total platinum was lower at 41.5 degrees C than at 37 degrees C (576 microM/h versus 1255 microM/h, respectively). Our results indicate that the advantage of adding hyperthermia is caused by an increased drug exposure of the tumor via the circulation. This was supported by the fact that platinum concentrations in peritoneal tumors after carboplatin treatment at elevated temperatures were similar for the i.p. and i.v. routes.

Adenocarcinoma↗

PubMed1992

Influence of dose and schedule on the therapeutic efficacy of 131I-labelled monoclonal antibody 139H2 in a human ovarian cancer xenograft model.

The therapeutic efficacy of various doses and schedules of 131I-labelled anti-episialin monoclonal antibody (MAb) 139H2 was assessed in the NIH:OVCAR-3 human ovarian cancer xenograft model. Radioimmunotherapy was started at the time s.c. tumors were well established (100 to 300 mm3). The anti-tumor effects induced by i.v. injections of 131I-MAb 139H2 were dose- and schedule-dependent. Optimal growth inhibition and long-lasting complete tumor regressions were obtained with 2 injections of 500, 700 or 750 muCi 131I-MAb 139H2 per mouse given with a 2-week interval. The percentage of tumors with more than 50% reduction of their initial volume after treatment with a total dose of 1,000 muCi 131I-MAb 139H2 per mouse, given as 10 injections of 100 muCi (3 x/week), 4 injections of 250 muCi (2 x/week), 10 injections of 100 muCi (5 x/week) within a period of 3 weeks, or 2 injections of 500 muCi with a 2-week interval, was 9%, 40%, 64% and 75% respectively. Unlabelled MAb 139H2 did not affect tumor growth, while the effects of 131I-control MAb were minor and transient. 131I-MAb 139H2 treatment did not select for outgrowth of episialin-negative cells in the OVCAR-3 xenografts. Highest absorbed doses of whole-body-radiation were calculated for 2 injections (500 to 750 muCi 131I-MAb 139H2) given with the 2-week interval. The radiation dose to the tumor after a single injection of 500 muCi 131I-MAb 139H2 was 1,300 cGy over 7 days, which appeared slightly lower than the dose calculated after administration of a tracer dose of iodinated MAb 139H2.

Animals↗

PubMed1992

Energy-dependent processes involved in reduced drug accumulation in multidrug-resistant human lung cancer cell lines without P-glycoprotein expression.

Mechanisms contributing to reduced cytotoxic drug accumulation were studied in two multidrug-resistant (MDR) human lung cancer cell lines without P-glycoprotein expression. In these (non-small cell) SW-1573/2R120 and (small cell) GLC4/ADR MDR cells, the steady-state accumulation of [14C]daunorubicin was 30 and 12%, respectively, of that in the parent cells. When cells, at steady state, were permeabilized with digitonin, the amount of daunorubicin binding increased only in the resistant cells. The reduced accumulation of daunorubicin in the SW-1573/2R120 and GLC4/ADR cells was accompanied by a lower initial (2 min) uptake rate of this drug. No difference in initial efflux rate of daunorubicin from preloaded cells could be detected between sensitive and resistant SW-1573 cells. However, daunorubicin was extruded 5-fold faster from GLC4/ADR cells than from the parental cells. In the presence of the energy metabolism inhibitors sodium azide and deoxyglucose, the reduced daunorubicin accumulations in the SW-1573/2R120 and GLC4/ADR MDR cells were (almost) completely reversed. The effects of these inhibitors on drug uptake were already apparent during the earliest measured time points (less than 15 s). Also, the enhanced efflux of daunorubicin from GLC4/ADR cells was inhibited. In ATP-depleted cells, the intracellular pH was lowered by approximately 0.3 units in resistant as well as in sensitive cells. The lower intracellular pH, however, could not account for the increase in daunorubicin accumulation in the resistant cells. Also, for vincristine and etoposide, the increases in drug accumulation under energy-deprived conditions were more pronounced in the resistant SW-1573/2R120 cells than in the parent SW-1573 cells. These results suggest that accumulation of drugs in the non-P-glycoprotein MDR human lung carcinoma cell lines SW-1573/2R120 and GLC4/ADR is reduced by an energy-dependent drug export mechanism which prevents efficient transport of drug to the target. Since P-glycoprotein expression in lung tumors is generally low, these MDR lung cancer cell lines can be used as a model to study alternative mechanisms leading to multidrug resistance in this tumor type.

Adenosine Triphosphate↗

PubMed1992

Quantification by laser scan microscopy of intracellular doxorubicin distribution.

Changes in intracellular drug localization accompany doxorubicin resistance in multidrug resistant tumor cells. The purpose of this study was to develop a method to quantify these changes and so detect different levels of resistance. Tumor cells were incubated with the fluorescent anthracycline doxorubicin (excitation at 480 nm; emission maximum at 560-590 nm) and were quantified using laser scanning microscopy. The fluorescent mode was used to record the intracellular drug distribution, whereas the absorption mode was used to define the nuclear and cytoplasmic boundaries. The cell compartments were delineated interactively on an image processing system and the ratio nuclear fluorescence/cytoplasmic fluorescence (N/C ratio) was determined. N/C ratios were: 1.8 in the Chinese hamster ovarian cell line AUXB1 and 0.1 in its MDR subline CHRC5; 3.8 in the human squamous lung cancer cell line SW-1573 and 1.8 and 0.4 in its MDR sublines SW-1573/2R120 and SW-1573/2R160, respectively; and 3.6 in the human myeloma cell line 8226/S and 2.1 and 1.0 in its MDR sublines 8226/Dox4 and 8226/Dox40, respectively. The doxorubicin distribution was independent of the doxorubicin concentration within a range from 1-32 microM. Furthermore, the progressive mean of the nuclear/cytoplasmic doxorubicin fluorescence ratio showed that a minimal sample size of 30 cells is necessary for reliable results. The results of two independent assessments showed a high reproducibility (r = 0.97). Thus, with the method described in this paper, it is possible to detect relatively low levels of doxorubicin resistance (factor 8).

Animals↗

PubMed1992

The reversal of cisplatin-protein interactions by the modulating agent WR2721 and its metabolites WR1065 and WR33278.

The reversibility of cisplatin-protein interactions by the modulating agent WR2721, its active thiol-metabolite WR1065, and the symmetrical disulfide WR33278 was studied using the model compounds (Pt(diethylenetriammine) monofunctionally bound to the sulfur in glutathione (Pt(dien)SG) and Pt(diethylenetriammine) monofunctionally bound to the sulfur in S-methylglutathione (Pt(dien)SMeG). Both model compounds could be quantified by high-performance liquid chromatography (HPLC) with UV detection. The Pt-cysteine-like bond in Pt(dien)SG could not be reversed by any of the WR compounds or by the strong nucleophiles thiosulfate (TS) and diethyldithiocarbamate (DDTC). However, the Pt-methionine-like bond in Pt(dien)SMeG could be reversed by WR1065, although the reversal was slow (k2 = 0.142 M-1 s-1) as compared with that obtained using the modulating agents TS (k2 = 10.1 M-1 s-1) and DDTC (k2 = 3.66 M-1 s-1). WR2721 was hardly able to reverse the Pt-S bond in Pt(dien)SMeG (k2 = 0.00529 M-1 s-1), and WR33278 showed no capacity to do so. The activity of cis-diamminedichloroplatinum(II) (CDDP)-inactivated fumarase was not appreciably restored by any of the WR compounds (16%, 7.7%, and 0 for 20 mM WR1065, WR2721, and WR33278, respectively) in contrast to the strong nucleophile DDTC (61% for 2 mM DDTC). These in vitro studies provide information at the molecular level that may explain why WR2721, in contrast to DDTC, does not provide protection against cisplatin-induced nephrotoxicity when it is given after platinum-containing chemotherapy. The results support the present clinical use of WR2721 prior to the administration of platinum compounds.

Amifostine↗

PubMed1992

Analysis of a conjugate between anti-carcinoembryonic antigen monoclonal antibody and alkaline phosphatase for specific activation of the prodrug etoposide phosphate.

The selective targeting of tumors by enzymes conjugated to monoclonal antibodies (mAb) may be an ideal approach to convert relatively nontoxic prodrugs into active agents at the tumour site. We used the anti-carcinoembryonic antigen mAb BW431/26 conjugated to alkaline phosphatase (AP) and phosphorylated etoposide (etoposide-P) as a prodrug to study the feasibility of this concept. Etoposide was phosphorylated with POCl3. Quantitative hydrolysis of etoposide-P to etoposide occurred within 10 min in the presence of AP. BW431/26 and AP were conjugated using a thioether bond. The AP conjugate retained 93% of its calculated activity. 125I-labelled AP conjugate did not show a reduction of immunoreactivity as determined by a cell-binding assay. SW1398 colon cancer cells were used to analyse the cytotoxicity of etoposide and etoposide-P. Etoposide (IC50 22 microM) was 100 times more toxic than etoposide-P (20% growth inhibition at 200 microM). Pretreatment of the cells with BW431/26-AP prior to etoposide-P exposure resulted in a dramatic increase in cytotoxicity (IC50 70 microM). The pharmacokinetics and tumour-localizing properties of BW431/27 and the AP conjugate were assessed in nude mice bearing SW1398 tumours. BW431/26 showed excellent tumour localization (10% of the injected dose/g tissue retained from 8 h to 120 h), whereas the AP conjugate showed a reduced tumour uptake (3%-0.3% of the injected dose/g tissue at 8-120 h), a faster clearance from the circulation and a high liver uptake. Radiolabelled AP showed a similar pharmacokinetic profile to the AP conjugate. Gel filtration analysis of blood, liver, and tumour samples indicated good stability of the conjugate.

Alkaline Phosphatase↗

PubMed1992

Treatment with tumour infiltrating lymphocytes and interleukin-2 in patients with metastatic melanoma: a pilot study.

Tumour infiltrating lymphocytes (TIL) were isolated and expanded from biopsy samples of 4 patients with metastatic melanoma. The patients were treated with autologous expanded TIL and continuous or bolus infusion of Interleukin 2 (IL-2) at a dose of 18 x 10(6) International Units/m2/day for 5 days starting 36-48 hours after administration of cyclophosphamide at a dose of 1 g/m2. The number of TIL infused ranged from 10(10) to 5.56 x 10(10) cells. Two patients had stable disease (SD) lasting for 2 1/2 and 4 months respectively and they died 24 and 13 months after therapy. One patient died during therapy due to a pseudomonas septicaemia and another patient developed progressive disease (PD). He died 3 months after the start of therapy. The side effects were substantial but most of them were reversible upon cessation of the treatment. The majority of the expanded TIL of all patients were of the CD8+ phenotype. Cutaneous metastases from two patients, removed after treatment with IL-2 and TIL, showed moderate lymphocytic infiltration also mainly of CD8+ T cells. The treatment with IL-2 and TIL is feasible, but further investigations should continue in an attempt to improve the efficacy of the therapy, to reduce toxicity and to diminish the costs and labour of the culture methods.

Cell Division↗

PubMed1992

Protection by WR-2721 of the toxicity induced by the combination of cisplatin and 5-fluorouracil.

We evaluated the effects of WR-2721 and its metabolite WR-1065 on in vitro growth inhibition by 5-fluorouracil (5FU) and cisplatin (CDDP) and the effect of WR-2721 on in vivo toxicity and antitumor effect of 5FU and CDDP. In cell culture both WR-2721 and WR-1065 were not able to reverse growth inhibition caused by either 5FU or CDDP. Administration of WR-2721 i.p. at 525 mg/kg to mice resulted in a severe temperature drop to 27 degrees C; at 200 mg/kg hypothermia was less severe. WR-2721 failed to prevent 5FU toxicity, but the maximum tolerated dose of CDDP in the combination with 5FU (at 100 mg/kg) could be increased from 3 to 7 mg/kg. CDDP at 7 mg/kg enhanced leukopenia caused by 5FU at 100 mg/kg to 20% and thrombocytopenia to 40%; WR-2721 reduced leukopenia and prevented thrombocytopenia induced by the combination. Combination of CDDP, 5FU, and WR-2721 resulted in an enhanced antitumor activity against the murine colon tumor Colon 26 compared to 5FU alone and to 5FU combined with CDDP at their maximum tolerated dose.

Amifostine↗

PubMed1992

Evaluation of desferal as a bifunctional chelating agent for labeling antibodies with Zr-89.

Zirconium-desferal was prepared and analysed by TLC, NMR and u.v.-spectroscopy. The stoichiometry of the complex was found to be 1:1. Chelation of desferal, coupled to resin, with 88Zr appeared to be fast and almost quantitative in various buffer systems in a broad pH-range (4-7). A high in vitro stability of the zirconium-desferal complex was observed; less than 0.2% zirconium was lost within 24 h in plasma-solutions.

Antibodies↗

PubMed1992

Modulation by D,L-buthionine-S,R-sulphoximine of etoposide cytotoxicity on human non-small cell lung, ovarian and breast carcinoma cell lines.

Treatment with 25 mumol/l D,L-buthionine-S,R-sulphoximine (BSO) for at least 24 h depleted glutathione (GSH) in human non-small cell lung (SW-1573), ovarian (A2780) and breast carcinoma (MCF-7) cell lines to about 20% of control, and was accompanied by a 2-fold potentiation of the cytotoxicity of etoposide, doxorubicin and cisplatin. Cellular etoposide, but not doxorubicin or cisplatin, concentrations were increased 2-fold due to decreased efflux. This occurred independently of the presence of BSO during 1 h of etoposide exposure, but required prolonged exposure to BSO (at least 24 h). Energy depletion as well as cotreatment, but not pretreatment, of the cells with daunomycin, doxorubicin, vinblastine or vincristine increased cellular etoposide accumulation. Treatment of control cells with verapamil caused similar changes in etoposide cytotoxicity and cellular pharmacokinetics as GSH depletion, but did not further increase etoposide cytotoxicity and accumulation in GSH-depleted cells. Etoposide efflux may have been inhibited, not because of (competitive) inhibition by BSO or disturbance of the energy required for this process, but probably because of plasma membrane alterations.

Antimetabolites, Antineoplastic↗

PubMed1992

Malignant Leydig cell tumor of the testis in complete remission on o,p'-dichlorodiphenyl-dichloroethane.

A 56-year-old patient is described who presented with retroperitoneal lymph node metastases 2 years after resection of a Leydig cell tumor of the left testis. The patient did not suffer from endocrinological imbalance. Surgical removal of the metastases alleviated abdominal symptoms for 1 year. o,p'-Dichlorodiphenyl-dichloroethane (o,p'-DDD) treatment was started at the time of recurrence of the retroperitoneal mass and the appearance of a hepatic metastasis. Tumors were remarkably responsive to o,p'-DDD, since 2 complete remissions could be obtained for extended periods. The o,p'-DDD was tolerated reasonably well and serum levels of 15 to 20 mg./l. were sustained for many months. Unfortunately, the patient could not be cured with this effective treatment.

Humans↗

PubMed1992

Comparison of the pharmacokinetics, biodistribution and dosimetry of monoclonal antibodies OC125, OV-TL 3, and 139H2 as IgG and F(ab')2 fragments in experimental ovarian cancer.

Monoclonal antibody (MAb) 139H2 was previously shown to localise specifically into ovarian cancer xenografts in nude mice. MAb 139H2 was compared with MAbs OC125 and OV-TL 3, all reactive with ovarian carcinomas, for the binding characteristics as IgG and F(ab')2 fragments with the use of the OVCAR-3 cell line grown in vitro and as s.c. xenografts. Immunoperoxidase staining of OVCAR-3 tissue sections with MAbs OC125 and 139H2 was heterogeneous, whereas MAb OV-TL 3 showed homogeneity. No differences in binding were observed between IgG and F(ab')2. The avidity expressed as apparent affinity constants of MAbs OC125, OV-TL 3 and 139H2 for OVAR-3 cells were 1 x 10(9) M-1, 1 x 10(9) M-1, and 1 x 10(8) M-1, while the number of antigenic determinants were 5 x 10(6), 1 x 10(6) and 7 x 10(6), respectively. In OVCAR-3 bearing nude mice the blood half-lives of the MAbs as IgG and F(ab')2 were approximately 50 h and 6 h, respectively. Maximum tumour uptake for the whole MAbs OC125, OV-TL 3, 139H2 and a control MAb 2C7 was 8.5%, 17.7%, 11.1% and 2.5% of the injected dose g-1, reached at 72 h after injection. For the respective F(ab')2 fragments, the maximum values were 5.2%, 10.0%, 5.5% and 1.9% of the injected dose g-1, reached between 6 h and 15 h. Tumour to non-tumour ratios were more favourable for the F(ab')2 fragments as compared to those for MAbs as IgG. Biodistribution in mice bearing a control tumour confirmed the specificity of tumour localisation of MAbs OC125, OV-TL 3 and 139H2. After injection of a tracer dose of 10 microCi of radiolabelled MAbs OC125, OV-TL 3 and 139H2 as IgG, tumours received 38 cGy, and 9 cGy. In our OVCAR-3 model, a ranking in efficiency in tumour localisation would indicate MAb OV-TL 3 as most favourable MAb, but cross-reactivity with subpopulations of human white blood cells might hamper its clinical use. Dosimetric data indicate a 4-fold higher radiation absorbed dose to tumours for IgG compared with F(ab')2 fragments.

Animals↗