Thalidomide Exerts Distinct Molecular Antileukemic Effects

Thalidomide Exerts Distinct Molecular Antileukemic Effects and Combined Thalidomide/Fludarabine Therapy is Clinically Effective in High-Risk Chronic Lymphocytic Leukemia Background: Thalidomide represents a promising immunomodulatory drug that targets both leukemia cells and the tumor microenvironment. Methods: We treated chronic lymphocytic leukemia (CLL) patients with a combined thalidomide/fludarabine regimen and monitored cellular and molecular changes induced by thalidomide in-vivo prior to fludarabine treatment. Thalidomide was given daily (100mg p.o./day) and fludarabine was administered on days 7-11 (25 mg/m² i.v./day) within each 4-week cycle (maximum of 6 cycles). Twenty patients received thalidomide/fludarabine as first line therapy and 20 patients were previously treated. Unmutated IgVH mutation status was found in 36 cases and 13 had high-risk cytogenetic aberrations (deletion of 17p13 or 11q22-q23). Results: The overall response rate was 80% and 25% for untreated and previously treated patients, respectively. While thalidomide effectively reduced the number of CLL cells, the number of CD3 lymphocytes showed no significant change, but the number of CD4+CD25hiFOXP3+ T-regulatory cells was significantly decreased. Gene expression profiling revealed a thalidomide induced signature containing both targets known to play a role in immunomodulatory drug action as well as novel candidate genes. Conclusions: Combined thalidomide/fludarabine therapy demonstrated efficacy in high-risk CLL patients. Furthermore, our study provides novel biological insights into thalidomide effect, which might act by enhancing apoptosis of CLL cells and reducing Tregs, thereby enabling T-cell dependent anti-tumor effect. Patients ("preTHAL") received thalidomide (100mg p.o./day) starting at day 0 and at day 7 Fludarabine therapy was added to the therapy. To evaluate the in-vivo influence of thalidomide on the transcriptome in CLL, paired GEP was performed in 20 cases at treatment start at day 0 (preTHAL) and prior to fludarabine treatment at day 7 (postTHAL) using HumanGenome U133 Plus2.0 Arrays according to the manufacturer's recommendations (Affymetrix; RNA was isolated from peripheral blood samples enriched for leukemic cells by Ficoll-density gradient centrifugation, percentage of leukemic cells > 90%). Fluorescence ratios were evaluated by both the GCOS software and normalized by applying the RMA algorithm using the BRB Array Tools software.