Sabine Zöchbauer

MULTIDRUG RESISTANCE IN LEUKEMIAS AND ITS REVERSAL

Drug resistance often results in failure of anticancer chemotherapy in leukemias. Several mechanisms of drug resistance are known with multidrug resistance (MDR) being the best characterized one. MDR can be due to enhanced expression of certain genes (MDR1, MRP or LRP), alterations in glutathione-S-transferase activity or GSH levels and to reduction of the amount or the activity of topoisomerase II. Here we review the current status of the clinical significance of the various mechanisms of MDR in leukemias and also discuss possibilities for the reversal of MDR. MDR1 gene expression has been seen in many leukemias, notably in acute myeloid leukemia (AML) and blast crisis of chronic myeloid leukemia. Both MDR1 RNA and P-glycoprotein expression of the leukemic cells have been shown to correlate with poor clinical outcome in AML. However, preliminary results indicate that the MRP gene as well as the LRP gene can be expressed in AML. Thus, drug resistance in leukemias appears to be multifactorial. P-glycoprotein-mediated MDR can be reversed by several drugs. These resistance modifiers are currently evaluated with regard to their clinical efficacy. Despite some encouraging results, reversal of drug resistance and subsequent improvement in clinical outcome remains to be shown.

MRP Expression in Acute Myeloid Leukemia

To determine the clinical significance of the multidrug resistance protein (MRP) in patients with de novo AML, we have studied MRP expression of leukemic cells at diagnosis and its association with clinical outcome in 127 patients. MRP expression was determined by immunocytochemistry by means of monoclonal antibodies QCRL-l/QCRL-3. MRP expression was low, intermediate and high in 30%, 46% and 24% of the patients, respectively. MRP expression was independent of age and sex of the patients, white blood cell count, FAB subtype, serum lactate dehydrogenase levels and karyotype aberrations. MRP expression had no impact on response to induction chemotherapy. The complete remission rates were 75%, 70% and 64% for patients with low, intermediate and high expression, respectively. Patients with intermediate or high MRP expression showed a trend toward shorter overall survival (p=0.09) as compared to patients with low MRP expression. MRP does not predict for response to induction chemotherapy but intermediate or high MRP expression might be associated with shorter overall survival of the patients.

MDR1 Gene Expression in Lymphocytes of Patients with Renal Transplants

The MDR1 gene, a multidrug resistance gene, codes for P-glycoprotein which pumps hydrophobic drugs out of the cells. Since cyclosporins also bind to P-glycoprotein and might be pumped by this transmembrane protein, we determined the expression of the MDR1 gene in the lymphocytes of 32 patients with renal transplants. MDR1 RNA expression of lymphocytes was measured by slot blot analysis and compared to the expression of drug-sensitive KB-3-1 cells and multidrug-resistant KB-8-5 cells. MDR1 RNA expression was detected in the lymphocytes of 9 (28%) patients, whereas no expression was seen in the remaining 23 patients. No association between MDR1 RNA expression and transplant function or hematological parameters was observed. However, none of the 6 patients who had transplants for more than 40 months expressed the MDR1 gene in their lymphocytes. In conclusion, expression of the MDR1 gene does occur in lymphocytes of patients with renal transplants and might reduce the immunosuppressive efficacy of cyclosporins through enhanced efflux of cyclosporins.

MDR1 RNA Expression as a Prognostic Factor in Acute Myeloid Leukemia: An Update

In order to confirm our initial report on the negative impact of MDR1 gene expression on the outcome of de novo acute myeloid leukemia (AML), we present an update of our prospective study with a larger number of patients and a longer duration of follow-up. At diagnosis, MDR1 RNA expression of the leukemic cells was negative in 37% and positive in 63% of the patients (N = 79). The complete remission rate of induction chemotherapy was 76% for MDR1 RNA negative and 54% for MDR1 RNA positive patients (p = 0.05). At a median observation duration of 33 months, the duration of overall survival was 19 months for the MDR1 RNA negative patients but only 8 months for the patients with MDR1 gene expression (p = 0.02). Thus the long-term data also indicate that MDR1 gene expression is an unfavourable prognostic factor in AML.

MDR1 Gene Expression in Chronic Lymphocytic Leukemia

In order to assess the clinical role of the MDR1 gene in chronic lymphocytic leukemia (CLL), we determined its expression in the leukemic cells of 39 patients with CLL and compared this with other clinical and laboratory parameters. MDR1 RNA expression was detected in 29 patients. MDR1 RNA transcripts were independent of age, treatment status of the patients and the clinical stage of CLL, but correlated with the white blood cell count and MDR2 RNA transcripts. Expression of the tumor suppressor gene p53 was found in 30 out of 37 patients and was associated with MDR1 RNA expression (P < 0.001). Immunocytochemistry using the monoclonal antibody C219 was performed in 38 patients, and in 28 cases, more than 5% of the leukemic cells were found to express cell surface P-glycoprotein. P-glycoprotein expression correlated with the expression of MDR1 RNA (P = 0.048).

MDR1 RNA transcripts do not indicate long-term prognosis in colorectal carcinomas

Because P-glycoprotein expression might be associated with a more aggressive behaviour of colorectal carcinomas (Weinstein et al., Cancer Res, 1991, 51, 2720-2726), we determined the relationship between MDR1 RNA expression of the carcinomas and the survival of the patients. At a median duration of follow-up of 86 months, event-free survival of patients with MDR1 RNA-negative tumours (n = 35) was not significantly different to that of patients with MDR1 RNA positive tumours (n = 67). Among the different tumour stages, event-free survival of the patients was also independent of MDR1 gene expression of the tumours. Thus, these findings do not support the hypothesis that local aggressiveness of P-glycoprotein positive tumour cells translates into worse clinical outcome.

Dexverapamil as resistance modifier in acute myeloid leukaemia

In order to evaluate dexverapamil as a resistance modifier in acute myeloid leukaemia, we have added dexverapamil (4×300 mg/d orally) to DA chemotherapy (daunorubicin, cytosine arabinoside) in six patients with acute myeloid leukaemia. Two patients (1 first and 1 second relapse) achieved complete remission and two patients (1 refractory disease, 1 third relapse) showed some improvement. One patient in first relapse died due to disease progression and one drug-refractory patient remained refractory. The peak plasma levels of dexverapamil and nordexverapamil ranged from about 600 to 4100 ng/ml and from 450 to 1130 ng/ml, respectively. Major sideeffects were hypotension and sinus bradycardia. These results show the need for further evaluation of dexverapamil as a resistance modifier in acute myeloid leukaemia.

Multimodale Therapien bei bronchuskarzinomen

ZusammenfassungGrundlagenBei Patienten mit operablen Bronchuskarzinomen kommt es trotz Operation häufig zu lokalen und systemischen Rezidiven. Für die Prognose sind somit lokale und systemische Therapien von wesentlicher Bedeutung. Die Behandlung sowohl des nichtkleinzelligen als auch des kleinzelligen Bronchuskarzinoms erfolgt deshalb zunehmend mittels multimodaler Konzepte, die sowohl lokale Therapiemaßnahmen als auch die systemische Chemotherapie inkludieren.MethodikAls Lokaltherapie eignen sich die Operation und/oder Radiotherapie. Die systemische Chemotherapie erfolgt häufig mittels cisplatinhältiger Protokolle.ErgebnisseBei lokal fortgeschrittenen nichtkleinzelligen Bronchuskarzinomen kann die Prognose durch Induktionschemotherapien mit anschließender Operation im Vergleich zur alleinigen Operation verbessert werden. Auch die postoperative adjuvante Chemotherapie mit neuen Zytostatika und verbesserten supportiven Maßnahmen dürfte in Zukunft zu einer Verbesserung der Prognose bei Patienten mit operablen nichtkleinzelligen Bronchuskarzinomen führen. Das kleinzellige Bronchuskarzinom wird ebenfalls meist mittels multimodaler Konzepte, die die Operation in den Frühstadien inkludieren, behandelt.SchlußfolgerungenMultimodale Therapiekonzepte in Verbindung mit neuen Zytostatika und verbesserten supportiven Therapien dürften zu einer Verbesserung der Prognose von Patienten mit Bronchuskarzinomen führen.SummaryBackgroundTreatment of stage I–III lung cancer requires both local control of the disease and systemic treatment of micrometastatic disease. Thus multimodality treatment approaches are increasingly used for the treatment of lung cancer.MethodsLocal therapy includes surgery with and without radiotherapy. Systemic therapy is performed with preferentially cisplatin containing chemotherapy protocols.ResultsInduction chemotherapy with subsequent surgery has resulted in improved outcome of patients with stage III non-small cell lung cancer as compared to surgery alone. In patients with stage I–IIIA non-small cell lung cancer, postoperative adjuvant chemotherapy with better supportive care and new anticancer drugs might improve the survival of patients. Small cell lung cancer is also frequently treated by a multimodality approach that includes surgery in early disease stages.ConclusionsMultimodality approaches are increasingly used in the treatment of lung cancer and should improve the outcome of patients with lung cancer.

152 P - MDR1 transcripts do not indicate long-term prognosis in primary colorectal carcinomas

The MDRI gene, a multidrug resistance gene, is frequently expressed in colorectal carcinomas. To determine whether this expression is of prognostic value, we determined the relationship between MDRI gene expression of primary colorectal carcinomas and the long-term outcome of the patients. RNA was isolated from tumor specimens by standard techniques. MDRI gene expression was determined by slot blot analysis by means of a radiolabeled cDNA (probe 5A). Survival durations of the patients were calculated according to Kaplan-Meier. MDRl RNA was detected in 65% of the primary carcinomas. At a median follow-up of 80 months, the durations of both relapse-free survival and overall survival were not different between patients with MDRI RNA positive tumors and those with MDRl RNA negative tumors. Thus MDRI gene expression of colorectal carcinomas does not predict the prognosis of the patients, although it might be involved in the well known drug resistance of these tumors.

43 P - Paclitaxel/cisplatin in stage IIIB/IV non-small-cell lung cancer

Paclitaxel (Taxol ® ) as single agent has shown promising activity in advanced non-small-cell lung cancer (NSCLC). In our phase II trial, we have determined the efficacy of paclitaxel combined with cisplatin. Inclusion criteria were good performance status, adequate renal as well as bone marrow function and no prior chemotherapy. Patients with signs of severe cardiac or hepatic dysfunction, pregnancy, clinical manifest neuropathy or manifest cerebral metastasis were excluded. Twenty patients with histologically proven NSCLC stage IIIB or IV were treated with paclitaxel (175mg/m 2 ) as 3-hour infusion after standard premedication on day 1 and cisplatin (50mg/m 2 daily) on days 1 and 2 with antiemetic therapy and sufficient pre- and posthydration. Treatment cycles were repeated every 3 weeks. Progressive disease resulted in discontinuation of treatment. All 20 patients were evaluable for response and toxic effects. Partial responses were seen in 7 patients (35%), no change in 9 patients (45%) and progressive disease in 4 patients (20%). Major side effects included leukopenia (WHO Grade 4 in 1 patient), anemia, alopecia and dose-limiting neurotoxicity (WHO Grade 3 in 1 patient). No severe hypersensitivity reaction has been observed. Thus paclitaxel/cisplatin has shown good antitumor activity in patients with advanced NSCLC and should be further evaluated in this disease.