Long-term thalidomide therapy resulted in lack of mdr1 gene expression in a patient with primary resistant multiple myeloma

The role of P-glycoprotein in drug resistance in multiple myeloma

Multiple myeloma (MM) is a malignant neoplastic cancer of the plasma cells that involves the bone marrow. The majority of patients with MM initially respond to chemotherapy, but they eventually become resistant to later drug therapy. One of the reasons for drug resistance in patients with MM is efflux transporters. P-glycoprotein (P-gp) is the most studied of the multidrug resistance proteins, and is up-regulated in response to many chemotherapeutic drugs. This up-regulation of P-gp causes a decrease in the intracellular accumulation of these drugs, limiting their therapeutic efficacy. In this review, we focus on the role of P-gp in drugs used for patients with MM. P-gp has been found to be an important factor with regard to drug resistance in many of the drug classes used in the treatment of MM (proteasome inhibitors, anthracyclines, alkylating agents and immunomodulators are examples). Thus, our further understanding of its mechanism and inhibitory effects will help us decrease drug resistance in patients with MM.

Inhibitory effect of thalidomide on the growth, secretory function and angiogenesis of estrogen-induced prolactinoma in Fischer 344 rats

The process of angiogenesis has been found to be essential for the development of estrogen-induced pituitary prolactinoma in Fischer 344 rats. Thalidomide [(alpha-(N-phthalimido)-glutarimide] is known to be a potent immunomodulatory drug with antiangiogenic properties, but its effect on lactotroph cell secretory function and pituitary prolactinoma formation has not been described yet. The purpose of this study was to examine the effects of thalidomide on secretion of prolactin (PRL) and vascular endothelial growth factor (VEGF), cell proliferation, apoptosis and angiogenesis within the anterior pituitary gland in long-term diethylstilboestrol (DES)-treated male F344 rats in vivo and in vitro. It was found that DES sharply increased serum PRL and VEGF levels. On the other hand, simultaneous treatment of F344 rats with thalidomide for the last 15 days of the experiment attenuated the stimulatory effect of DES on PRL and VEGF secretion. It also diminished prolactin cell proliferation evaluated as the number of proliferating cell nuclear antigen (PCNA)-positive stained cell nuclei and increased the number of apoptotic bodies determined by the terminal deoxynucleotidyl-mediated dUTP nick-end labeling (TUNEL) method in sections of the DES-induced pituitary prolactinoma. The density of pituitary microvessels evaluated by microscopic counting of CD-31-positive blood vessels was also diminished by the tested drug. In addition, thalidomide (10(-4) to 10(-6) M) inhibited cell proliferation, prolactin and VEGF secretion from rat pituitary prolactinoma cells cultured in vitro. In conclusion, our results provide strong evidence for the antiprolactin and antitumor activity of thalidomide in experimentally DES-induced pituitary adenoma.

Thalidomide in multiple myeloma

Multiple myeloma is an incurable bone marrow cancer, the treatment of which is notoriously difficult. Only modest advances have been achieved using complex polychemotherapeutic regimens, transplant strategies and supportive therapy. In 1999, when new drugs for myeloma were urgently needed, thalidomide was introduced and opened up a completely new line of therapy for the disease. Although the mechanism of action is not yet completely understood, thalidomide has demonstrated efficacy in patients with refractory, relapsed myeloma, even in late-stage cases. This article reviews the current knowledge of thalidomide in myeloma treatment, focusing especially on the possible mechanisms of action, clinical results and adverse events of this drug.