PubMed Health⌕ Search

Biomedical subjects

M Lehnert

Publications and source records attributed to M Lehnert.

At least 19 recordsLinked to original sources
PubMed1998

Phase II trial of dexverapamil and epirubicin in patients with non-responsive metastatic breast cancer.

Agents capable of reversing P-glycoprotein-associated multidrug resistance have usually failed to enhance chemotherapy activity in patients with solid tumours. Based on its toxicity profile and experimental potency, dexverapamil, the R-enantiomer of verapamil, is considered to be promising for clinical use as a chemosensitizer. The purpose of this early phase II trial was to evaluate the effects of dexverapamil on epirubicin toxicity, activity and pharmacokinetics in patients with metastatic breast cancer. A two-stage design was applied. Patients first received epirubicin alone at 120 mg m(-2) i.v. over 15 min, repeated every 21 days. Patients with refractory disease continued to receive epirubicin at the same dose and schedule but supplemented with oral dexverapamil 300 mg every 6 h x 13 doses. The Gehan design was applied to the dexverapamil/epirubicin cohort of patients. Thirty-nine patients were entered on study, 25 proceeded to receive epirubicin plus dexverapamil. Dexverapamil did not increase epirubicin toxicity. The dose intensity of epirubicin was similar when used alone or with dexverapamil. In nine intrapatient comparisons, the area under the plasma concentration-time curve (AUC) of epirubicin was significantly reduced by dexverapamil (mean 2968 vs 1901 microg ml[-1] h[-1], P= 0.02). The mean trough plasma levels of dexverapamil and its major metabolite nor-dexverapamil were 1.2 and 1.5 microM respectively. The addition of dexverapamil to epirubicin induced partial responses in 4 of 23 patients evaluable for tumour response (17%, CI 5-39%, s.e.P 0.079). The remissions lasted 3, 8, 11 and 11+ months. These data suggest that the concept of enhancing chemotherapy activity by adding chemosensitizers may function not only in haematological malignancies but also in selected solid tumours. An increase in the AUC and toxicity of cytotoxic agents does not seem to be a prerequisite for chemosensitizers to enhance anti-tumour activity.

Adult↗
PubMed1997

Intermittent exposure to doxorubicin in vitro selects for multifactorial non-P-glycoprotein-associated multidrug resistance in RPMI 8226 human myeloma cells.

The purpose of the present study was to evaluate whether intermittent exposure to a constant dose of doxorubicin selects for multidrug resistance (MDR) in RPMI 8226 human myeloma cells and, if so, to determine the molecular mechanism. In an attempt to approximate clinical doxorubicin treatment in vitro, cells were exposed to a fixed dose of doxorubicin for 4 d alternating with growth in drug-free medium for 17 d. An MDR subline emerged, termed 8226/DOXint5, which was 3-4-fold resistant to doxorubicin, etoposide and m-AMSA, and 1.6-fold resistant to vincristine. Sensitivity to docetaxel, melphalan and cisplatin was normal. Verapamil normalized vincristine sensitivity but had little effect on resistance to the other agents. Cellular uptake and retention of daunorubicin and vincristine were reduced by approximately 10%. The 8226/DOXint5 cells showed diminished DNA topoisomerase IIalpha expression and increased expression of the multidrug resistance protein MRP. Expression of MDR1/P-glycoprotein was not detected. Immunostaining showed 70% of the cells to over-express the lung-resistance protein LRP. This new MDR myeloma cell line may prove to be a useful model for the development of strategies to overcome low-level, multifactorial MDR, which might be a common phenomenon in clinical myeloma treated with doxorubicin.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Randomized comparison of total androgen blockade alone versus combined with weekly epirubicin in advanced prostate cancer.

Hormone deprivation is the gold standard for the treatment of metastatic prostate cancer. However, prostate cancer being primarily a heterogeneous tumor comprising hormone-dependent, hormone-sensitive, and hormone-insensitive cells, at least the latter remain unaffected by hormonal manipulations, thus making disease progression almost inevitable. In quest of a more comprehensive therapy we therefore studied the concept of early combined chemoendocrine therapy in a prospective randomized multicenter trial. The purpose of this study was to evaluate whether patients with previously untreated advanced prostate cancer benefit from combining total androgen blockade (TAB) with weekly epirubicin chemotherapy (E-TAB). From April 1988 to January 1991, 145 previously untreated patients with either metastatic (n = 117) or locally advanced (n = 28) histologically confirmed prostate cancer were randomly allocated to treatment with TAB by bilateral orchiectomy and flutamide 250 mg t.i.d. or TAB plus weekly epirubicin 25 mg/m2 i.v. for 18 weeks (E-TAB). The study endpoints were progression-free survival and overall survival. In addition the effects of treatment on quality of life were assessed by two methods. At regular intervals patients self-assessed ten qualities of physical, functional and emotional health using 5-point scales. In order to evaluate the time without disease progression and treatment-induced adverse effects, a modified Q-TWiST (quality-adjusted time without symptoms and toxicity) model was applied. At a median follow-up of 81 months, progression-free survival and overall survival in the TAB and E-TAB groups were 12 and 18 months (p < 0.02) and 22 and 30 months (p = 0.12), respectively. In patients with > 5 sites of bone metastasis (D2max), the corresponding periods were 9 and 14 months (p = 0.005) and 17 and 27 months (p = 0.06), respectively. Subjective quality of life assessment showed no impairment of quality of life by epirubicin treatment. Stage D and D2max patients treated with E-TAB had an average gain in Q-TWiST of 5 months (p = 0.098) and 8 months (p = 0.03), respectively, compared to the TAB treatment. Objective toxicities were generally mild with either treatment. In conclusion, the combination of TAB and epirubicin was well tolerated by patients with advanced prostate cancer and resulted in a significant extension of progression-free survival. This effect of E-TAB on objective treatment outcome was accompanied by prolonged time without treatment-induced adverse effects and tumor progression, i.e., time with good quality of life. Therefore, further studies with E-TAB appear warranted in patients with advanced prostate cancer.

Aged↗
PubMed1996

Tumor necrosis factor alpha is a powerful apoptotic inducer in lymphoid leukemic cells expressing the P-170 glycoprotein.

Multidrug resistance (MDR) is a phenomenon by which tumor cells exposed to a single anti-proliferative agent acquire resistance to other structurally and functionally unrelated drugs. The classical form of MDR is caused by a plasma-membrane protein currently named P-glycoprotein or P-170 encoded by the human mdr-1 gene in its functional isoform. In vitro cell lines expressing P-170 usually also present phenotypic and functional alterations. In the present study we report that the cytotoxicity mediated by tumor necrosis factor alpha (TNF alpha) in MDR variants of the human T-lymphoblastoid CEM cell line is associated with apoptosis (programmed cell death). Susceptibility of MDR cells to apoptosis was increased upon cycloheximide + TNF alpha sequential treatment, whereby the impairment of protein synthesis due to the former agent was followed by the effect of cytokine exposure. Massive apoptosis of P-170-positive cells, but not of controls, was also obtained by depletion of nutrients (i.e., serum starvation). In contrast, TNF-alpha exerted a similar apoptotic effect in epithelial (MCF-7) or myeloma (S8226) drug-sensitive/ -resistant cell pairs. However, the MDR variant of myeloma S8226 was more sensitive to the cytostatic effect of TNF alpha than the parental drug-sensitive cell line. These results suggest that the presence of the MDR phenotype may be associated with increased histotype-dependent cell susceptibility to specific, protein-synthesis-independent, apoptotic pathways.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Methods to detect P-glycoprotein-associated multidrug resistance in patients' tumors: consensus recommendations.

Multidrug resistance (MDR), especially that associated with overexpression of MDR1 and its product, P-glycoprotein (Pgp), is thought to play a role in the outcome of therapy for some human tumors; however, a consensus conclusion has been difficult to reach, owing to the variable results published by different laboratories. Many factors appear to influence the detection of Pgp in clinical specimens, including its low and heterogeneous expression; conflicting definitions of detection end points; differences in methods of sample preparation, fixation, and analysis; use of immunological reagents with variable Pgp specificity and avidity and with different recognition epitopes; use of secondary reagents and chromogens; and differences in clinical end points. Also, mechanisms other than Pgp overexpression may contribute to clinical MDR. The combined effect of these factors is clearly important, especially among tumors with low expression of Pgp. Thus, a workshop was organized in Memphis, Tennessee, to promote the standardization of approaches to MDR1 and Pgp detection in clinical specimens. The 15 North American and European institutions that agreed to participate conducted three preworkshop trials with well-characterized MDR myeloma and carcinoma cell lines that expressed increasing amounts of Pgp. The intent was to establish standard materials and methods for a fourth trial, assays of Pgp and MDR1 in clinical specimens. The general conclusions emerging from these efforts led to a number of recommendations for future studies: (a) although detection of Pgp and MDR1 is at present likely to be more reliable in leukemias and lymphomas than in solid tumors, accurate measurement of low levels of Pgp expression under most conditions remains an elusive goal; (b) tissue-specific controls, antibody controls, and standardized MDR cell lines are essential for calibrating any detection method and for subsequent analyses of clinical samples; (c) use of two or more vendor-standardized anti-Pgp antibody reagents that recognize different epitopes improves the reliability of immunological detection of Pgp; (d) sample fixation and antigen preservation must be carefully controlled; (e) multiparameter analysis is useful in clinical assays of MDR1/Pgp expression; (f) immunostaining data are best reported as staining intensity and the percentage of positive cells; and (g) arbitrary minimal cutoff points for analysis compromise the reliability of conclusions. The recommendations made by workshop participants should enhance the quality of research on the role of Pgp in clinical MDR development and provide a paradigm for investigations of other drug resistance-associated proteins.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Serum can inhibit reversal of multidrug resistance by chemosensitisers.

The purpose of this study was to evaluate to what extent the ability of various chemosensitisers (CS) to reverse P-glycoprotein-associated multidrug resistance (MDR) is reduced when tested in physiological serum protein concentrations. Utilising drug sensitivity and accumulation assays, the CS were tested in medium containing 10% fetal bovine serum and in 100% horse or human serum. Two RPMI 8226 human myeloma sublines were used which express different levels of P-glycoprotein. The CS were tested at various concentrations, including clinically achievable blood levels. When using the CS at high doses, wide differences were observed in the extent CS activity was diminished by serum. Verapamil, cyclosporin A and quinine were not affected, quinidine and medroxyprogesterone acetate were moderately inhibited, and amiodarone and trifluoperazine were largely inactivated. When the CS were used at concentrations achievable in humans, the activity of all agents except quinine was markedly reduced by serum. With respect to the extent to which CS activity was diminished by serum, good statistical correlation (r > 0.90, P < 0.001) was found between the use of cytotoxicity and drug accumulation assays, horse and human serum or cell lines with high and low levels of P-glycoprotein, respectively. These studies demonstrated that physiological serum protein concentrations can profoundly diminish the MDR reversing activity of particular CS. Some drugs, such as amiodarone and trifluoperazine, are largely inactivated by serum when used at a wide range of concentrations. Other agents, such as verapamil and cyclosporin A, are essentially unaffected when used at high doses but markedly inhibited at concentrations achievable in humans. These data suggest that in vitro studies of CS in medium containing low serum protein concentrations can result in misleading conclusions regarding the potential clinical activity of such agents.

Animals↗
PubMed1996

A randomized phase II study with two schedules of the novel indoloquinone EO9 in non-small-cell lung cancer: a study of the EORTC Early Clinical Studies Group (ECSG).

In a multicentre randomized trial of the EORTC-ECSG, we have treated 38 chemotherapy naïve patients with advanced non-small-cell lung cancer (NSCLC) with EO9, a novel bio-reductive alkylating indoloquinone. The drug was given at two different dose schedules by a single bolus i.v. injection: arm A 12 mg/m2 weekly and arm B 22 mg/m2 every three weeks. All together 185 courses were administered (145 in arm A and 40 in arm B). The major toxicity was reversible proteinuria more frequently occurring in the three-weekly schedule (arm A 34.5% vs. arm B 62.5%). Creatinine elevation, fluid retention and pericardial or pleural effusion were also recorded in a limited number of patients. Other common toxicities more frequent in the three-weekly administration were asthenia (21% vs. 35% of cycles), nausea (15% vs. 27.5% of cycles) and vomiting (5% vs. 17.5% of cycles). Toxicities were mainly of grade I and II. No responses have been observed. Five patients (26%) on arm A and eight (53%) on arm B experienced stable disease. These doses and schedules of EO9 do not yield activity in NSCLC.

Adult↗
PubMed1995

Randomised phase II study of epirubicin-vindesine versus mitoxantrone-vindesine in metastatic breast cancer.

The purpose of this study was to compare the activity and toxicity of epirubicin-vindesine (EV) with mitoxantrone-vindesine (MV) in patients with metastatic breast cancer. A total of 295 patients was randomly allocated to treatment with vindesine 3 mg/m2 combined with either epirubicin 40 mg/m2 or mitoxantrone 10 mg/m2. All drugs were given by intravenous push, treatment cycles were repeated at 3-4 week intervals. 255 patients were available for response, and 283 for toxicity. EV and MV yielded similar objective response rates (34 and 26%, respectively), response durations, times to progression and survival. Median time to remission was 1.8 and 3.1 months (P = 0.006) with EV and MV, respectively. In patients with visceral metastases, response rate was higher with EV than MV (40 versus 23%; P = 0.03). Patients receiving MV had less nausea/vomiting (P = 0.007) and alopecia (P = < 0.001) of WHO grade > or = 2. Bone marrow, cardiac and other toxicities were mild with both treatments. The observed differences in activity and toxicity between the two regimens appear to have clinical relevance. EV proved to be more active in visceral disease and to be able to induce remissions more rapidly. Accordingly, patients with visceral metastases or severe tumour-related symptoms may benefit from epirubicin-based treatment. Subjective toxicities, i.e. nausea/vomiting and alopecia, were less frequent and severe with MV. Thus, MV may prove useful in patients with more indolent disease and appears to warrant phase III evaluation in such patients.

Adult↗
PubMed1994

Multidrug resistance in human cancer.

Resistance to cytotoxic chemotherapy continues to be a major obstacle to more effective treatment of human cancers. A particular problem in clinical cancer chemotherapy is the phenomenon of simultaneous resistance of cancers to a variety of unrelated cytotoxic agents. Such resistance to multiple drugs is observed much more often than resistance to individual compounds. A similar experimental phenomenon has been termed multidrug resistance or MDR. Much has been learned in recent years about molecular mechanisms which can lead to MDR in cancer cells and a number of studies has been performed to evaluate the clinical relevance of such mechanisms. In particular, P-glycoprotein-associated MDR (MDR1) has received a lot of attention. This review will discuss (i) some principal aspects of drug resistance in cancer with particular emphasis on MDR1; (ii) available data on drug resistance mechanisms in brain tumors; and (iii) our current knowledge on the putative role of P-glycoprotein in the blood-brain barrier.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Results of conservative treatment of partial tears of the anterior cruciate ligament.

The diagnosis of an acute partial tear of the anterior cruciate ligament was made in 56 patients who did not undergo surgical repair. After a period of up to 5 years, 39 returned for follow up evaluation. They were divided into three groups according to clinical analysis of the knee and the Lysholm-Gillquist score. Our aim was to determine their long term functional limitations. 56% had progressed to anterior cruciate ligament deficiency at the time of follow up. This came about not only after resuming sporting activities, but also occurred in those who were not so active. Our results suggests that a partial tear leaves an irreversible defect which may progress to a complete tear, especially in young athletes engaged in active sport.

Adult↗
PubMed1993

Sinus histiocytosis with massive lymphadenopathy. Skeletal involvement.

A 64-year-old female patient has been suffering from sinus histiocytosis with massive lymphadenopathy (SHML) for 2 years. After 12 months of illness, the patient developed swelling and pain in various skeletal regions. Scintigraphic, radiological and CT imaging revealed multiple osseous lesions. Subsequent biopsies yielded the histomorphological findings typical for SHML. After operative resection of the left cuboid, which was the most painful region during walking, the defect was filled with an autologous bone transplant. At this time no other osteolytic region was treated surgically, because the patient had first to undergo ENT treatment.

Bone Diseases↗
PubMed1993

Chemohormonal and immunohormonal approaches in advanced prostatic carcinoma.

The standard palliative treatment for patients with advanced prostate cancer has for the past 50 years been androgen withdrawal. However, owing to the presence of hormone-insensitive cell clones, the benefits of this approach have now appeared to reach their optimum. It is now generally believed that further major therapeutic advances in the treatment of prostate cancer are unlikely, unless consideration is given to these hormonally independent cells. Two possible alternative strategies which address this problem are chemohormonal and immunohormonal approaches, both of which are discussed in detail in this article.

Androgen Antagonists↗