ABSTRACT
Telomere shortening is associated with disease progression in chronic myeloid leukaemia (CML). To investigate the biology and regulation of telomerase in CML, we evaluated expression of the telomerase components, its regulators and several telomeric-associated proteins. Quantitative real-time-polymerase chain reaction (PCR) was used to compare gene expression in the CD34+/leukaemic blast cells of 22 CML patient samples to the CD34+ cell population of healthy individuals. hTERT, the catalytic component of telomerase, was downregulated in eight of 12 chronic phase (CP) patients (P = 0.0387). Furthermore, hTERT was significantly downregulated in two of three patients in accelerated phase (AP) and seven of seven patients in blast crisis (BC), P = 0.0017. Expression of hTR and telomeric-associated proteins TEP1, TRF1, TRF2, tankyrase and PinX1 was high in the majority of CP and AP patients. With the exceptions of TEP1 and hTR, expression of these factors was highest in CP and decreased during disease progression. Expression of c-Myc, a positive regulator of hTERT transcription, correlated with hTERT expression and decreased with disease progression, falling below control levels in BC. hTERT levels were increased in CP patients following successful treatment with imatinib, relative to untreated CP patients. We suggest that reduced hTERT expression directly causes the shortened telomeres observed in CML.
Subject(s)
DNA-Binding Proteins/metabolism , Gene Expression Regulation, Leukemic/genetics , Hematopoietic Stem Cells/metabolism , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism , Telomerase/metabolism , Adolescent , Adult , Aged , Antigens, CD34/biosynthesis , Benzamides , Carrier Proteins/biosynthesis , Cell Cycle Proteins , DNA-Binding Proteins/biosynthesis , DNA-Binding Proteins/genetics , Disease Progression , Down-Regulation/genetics , Female , Gene Expression Regulation, Enzymologic/drug effects , Gene Expression Regulation, Enzymologic/genetics , Gene Expression Regulation, Leukemic/drug effects , Humans , Imatinib Mesylate , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy , Male , Middle Aged , Piperazines/pharmacology , Piperazines/therapeutic use , Proto-Oncogene Proteins c-myc/biosynthesis , Pyrimidines/pharmacology , Pyrimidines/therapeutic use , RNA/biosynthesis , RNA-Binding Proteins , Reverse Transcriptase Polymerase Chain Reaction/methods , Sensitivity and Specificity , Tankyrases/biosynthesis , Telomerase/biosynthesis , Telomerase/genetics , Telomeric Repeat Binding Protein 1/biosynthesis , Telomeric Repeat Binding Protein 2/biosynthesis , Transcription, Genetic , Tumor Suppressor Proteins/biosynthesisABSTRACT
We report the use of reduced-intensity conditioning (RIC)-matched sibling allogeneic bone marrow stem cell transplantation as a method of establishing a graft-vs.-leukaemia (GvL) effect against myeloid disorders using a fludarabine-melphalan protocol without the use of T-lymphocyte-depleting antibodies. The 16 patients in this group had predominantly poor-risk acute myeloid leukaemia (AML) (n=10), AML/myelodysplasia (MDS) (n=2) and MDS (n=4). All but one patient achieved full haematopoietic engraftment. Thirteen of 16 patients are alive and in continued complete remission on completion of this study with a median follow-up of 426 d (range 83-1524). The actuarial 4 yr disease-free and overall survival is 79% for both. Only one patient relapsed following transplant, giving a relapse rate of 6% during the study period. The treatment-related mortality was 13% (n= 2). Overall, acute graft-vs.-host disease (GvHD) occurred in 53% (8/15), with acute GvHD grade II or above occurring in 47% (7/15). In the 13 evaluable patients, chronic GvHD occurred in 46% (6/13), with this being extensive in three patients. These results suggest that a GvL effect can be delivered against poor-risk myeloid disorders with a low non-relapse mortality using this fludarabine-melphalan RIC protocol.