Clinical relevance of P-glycoprotein expression in haematological malignancies

Although, generally speaking, haematological malignancies are chemotherapy-responsive tumours and high remission induction rates are obtained, disease-related death is the rule rather than the exception. The appearance of cell populations, resistant to multidrug-based chemotherapy, constitutes the major problem to achieve cures in these patients. Advances in cell biology have partly contributed to the elucidation of different multidrug resistance (MDR) mechanisms, which enable cells to survive the cytotoxic effects of multiple chemotherapeutic agents. Of these resistance mechanisms, the one that is referred to as classical MDR is the most extensively studied, both in the laboratory as well as in patients, and here we will focus on its clinical relevance in haematological malignancies. The classical MDR phenotype is caused by enhanced cellular drug efflux due to increased activity of a membrane-bound glycoprotein (P-glycoprotein) drug pump, that can pump out anthracyclines, anthracenediones, vinca alkaloids and epipodophyllotoxins, thereby actively lowering the intracellular drug concentrations to sublethal levels. As soon as molecular probes for the detection of MDR cells became available, clinical studies were initiated to answer three main questions. Do human tumour cells express P-glycoprotein? If so, is the expression indicative of a bad prognosis, c.q. resistant disease? And last but not least, can we interfere with the P-glycoprotein drug pump in the patient? Clinical data indicate that classical MDR may be involved in the development of drug resistance, especially in some haematological malignancies, such as acute myelocytic leukaemia (AML), non-Hodgkin's lymphomas (NHL), and multiple myelomas (MM). In almost all types of haematological malignancies, either untreated or treated, elevated P-glycoprotein levels have been reported, ranging from low to high. However, the acquisition of clinical MDR associated with P-glycoprotein expression occurs only in those diseases (for example, AML and MM) that are heavily treated with MDR-related drugs, probably by selection of pre-existing P-glycoprotein-expressing malignant cells. Since P-glycoprotein is found to be expressed on the membrane of normal haemopoietic progenitor cells as well, it seems likely that P-glycoprotein-positive haematological tumours develop by malignant transformation of P-glycoprotein-expressing normal haemopoietic counterparts. Especially for AML, convincing data have been reported in the literature to show that P-glycoprotein expression at diagnosis is a bad prognostic factor that predicts refractoriness. Using in vitro model systems for classical MDR, a large number of agents have been identified that can circumvent P-glycoprotein-mediated drug resistance, the so-called resistance modifying agents (RMA). Subsequently, clinical phase I and II studies have been initiated which combine the use of MDR-related drugs in conjunction with RMAs. The overall conclusions from such studies in AML, NHL, and MM are that modulation of drug resistance by RMAs seems promising and that further evaluation in prospective, randomized phase III trials is warranted

Acute dystonic reaction to metoclopramide in patients carrying homozygous cytochrome P450 2D6 genetic polymorphisms

BACKGROUND: Extrapyramidal syndromes (EPS) are clinically relevant side effects of metoclopramide which are often not anticipated. PATIENTS AND METHODS: Two patients who received metoclopramide developed an acute dystonic reaction. Symptoms disappeared after biperiden or trihexyphenidyl were given. Molecular analysis of the CYP2D6 gene was performed using a PCR-based method. RESULTS: Both patients were homozygous for inactive CYP2D6 alleles (CYP2D6*4/*4 and CYP2D6*4/*5), which are associated with slow drug metabolism. CONCLUSION: Metoclopramide-induced acute dystonic reactions may occur in patients carrying a CYP2D6 genetic polymorphism

Changes in income and employment after diagnosis among patients with multiple myeloma in The Netherlands

Objective: Due to new treatment options, survival rates in multiple myeloma (MM) are improving. Consequently, maintaining work and income is becoming more important for patients and society. Therefore, we aimed to explore the change in income and employment in patients with MM. Methods: Data from the Netherlands Cancer Registry of MM patients diagnosed between 2012 and 2017 were merged with socioeconomic data from Statistics Netherlands. Descriptive statistics were used to analyse total income, income from employment, and accumulated income before and after diagnosis. Results: Income from employment decreased by 45% in MM patients, between 1 year before and 4 years after diagnosis Four years after diagnosis, 35% of the patients were still employed, with an accumulated 5-year productivity loss of €121 million. Higher income loss from employment and job loss was observed in female patients, patients with more extensive disease, or those not treated with autologous stem cell transplant.Conclusion: Loss of (income from) employment among patients with MM was high, causing financial burden on the patient and society. With improving survival in MM, more research and awareness are needed to better assess the importance of income and work for MM patients and society.</p

Changes in income and employment after diagnosis among patients with multiple myeloma in The Netherlands

Objective: Due to new treatment options, survival rates in multiple myeloma (MM) are improving. Consequently, maintaining work and income is becoming more important for patients and society. Therefore, we aimed to explore the change in income and employment in patients with MM. Methods: Data from the Netherlands Cancer Registry of MM patients diagnosed between 2012 and 2017 were merged with socioeconomic data from Statistics Netherlands. Descriptive statistics were used to analyse total income, income from employment, and accumulated income before and after diagnosis. Results: Income from employment decreased by 45% in MM patients, between 1 year before and 4 years after diagnosis Four years after diagnosis, 35% of the patients were still employed, with an accumulated 5-year productivity loss of €121 million. Higher income loss from employment and job loss was observed in female patients, patients with more extensive disease, or those not treated with autologous stem cell transplant.Conclusion: Loss of (income from) employment among patients with MM was high, causing financial burden on the patient and society. With improving survival in MM, more research and awareness are needed to better assess the importance of income and work for MM patients and society.</p

Reversal of typical multidrug resistance by cyclosporin and its non-immunosuppressive analogue SDZ PSC 833 in Chinese hamster ovary cells expressing the mdr1 phenotype

Summary The new non-immunosuppressive cyclosporin derivative SDZ PSC 833 (PSC) is a potent agent used to overcome typical multidrug resistance (MDR) associated with overexpression of themdr1 gene encoding for a P-170 glycoprotein. In the present study, the efficacy of PSC as compared with cyclosporin was determined in Chinese hamster ovary cell lines exhibiting different levels of resistance to colchicine (0, 0.1, 0.2 and 10 μg/ml, respectively). Low concentrations of PSC (8.2nm) increased the cytotoxicity of colchicine in cell lines expressing low levels of drug resistance. The concentration resulting in 50% cell survival (LC50 value) found for colchicine alone or in combination with PSC in the CHO-A3 cell line that was resistant to 100 ng colchicine/ml decreased from >500 to 200 ng/ml at 8.2nm PSC and to 500 ng/ml for colchicine alone to 500 ng/ml for colchicine used in combination with 8.2nm PSC and to <100 ng/ml for colchicine combined with 82 or 820nm PSC. At a concentration of 82nm PSC, the maximal effect in MDR reversal was observed in the cell lines exhibiting moderate resistance. In the highly resistant cell line, PSC (820nm) also reversed colchicine resistance. In drug-accumulation experiments, we obtained a 4-fold increase in intracellular doxorubicin accumulation using 820nm PSC. A comparison of PSC with cyclosporin revealed that a cyclosporin concentration 20-fold that of PSC was required to obtain the same sensitising effect. On the basis of these data, it may be concluded that PSC is a most promising chemosensitiser