The aberrant asynchronous replication - characterizing lymphocytes of cancer patients - is erased following stem cell transplantation.
BACKGROUND
Aberrations of allelic replication timing are epigenetic markers observed in peripheral blood cells of cancer patients. The aberrant markers are non-cancer-type-specific and are accompanied by increased levels of sporadic aneuploidy. The study aimed at following the epigenetic markers and aneuploidy levels in cells of patients with haematological malignancies from diagnosis to full remission, as achieved by allogeneic stem cell transplantation (alloSCT).


METHODS
TP53 (a tumor suppressor gene assigned to chromosome 17), AML1 (a gene assigned to chromosome 21 and involved in the leukaemia-abundant 8;21 translocation) and the pericentomeric satellite sequence of chromosome 17 (CEN17) were used for replication timing assessments. Aneuploidy was monitored by enumerating the copy numbers of chromosomes 17 and 21. Replication timing and aneuploidy were detected cytogenetically using fluorescence in situ hybridization (FISH) technology applied to phytohemagglutinin (PHA)-stimulated lymphocytes.


RESULTS
We show that aberrant epigenetic markers are detected in patients with hematological malignancies from the time of diagnosis through to when they are scheduled to undergo alloSCT. These aberrations are unaffected by the clinical status of the disease and are displayed both during accelerated stages as well as in remission. Yet, these markers are eradicated completely following stem cell transplantation. In contrast, the increased levels of aneuploidy (irreversible genetic alterations) displayed in blood lymphocytes at various stages of disease are not eliminated following transplantation. However, they do not elevate and remain unchanged (stable state). A demethylating anti-cancer drug, 5-azacytidine, applied in vitro to lymphocytes of patients prior to transplantation mimics the effect of transplantation: the epigenetic aberrations disappear while aneuploidy stays unchanged.


CONCLUSIONS
The reversible nature of the replication aberrations may serve as potential epigenetic blood markers for evaluating the success of transplant or other treatments and for long-term follow up of the patients who have overcome a hematological malignancy.
Nagler
Arnon
A
Bone Marrow Transplantation Department, Institute of Hematology, Chaim Sheba Medical Center, Tel-Hashomer 52621, Israel.
Cytron
Samuel
S
Mashevich
Maya
M
Korenstein-Ilan
Avital
A
Avivi
Lydia
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000782:Aneuploidy; D001374:Azacitidine / Q000494:pharmacology; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D002886:Chromosomes, Human, Pair 17; D002891:Chromosomes, Human, Pair 21; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D042522:DNA Replication Timing / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects; D005260:Female; D019337:Hematologic Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology / Q000601:surgery*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008214:Lymphocytes / Q000187:drug effects / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D033581:Stem Cell Transplantation; D013997:Time Factors; D014184:Transplantation, Homologous; D016896:Treatment Outcome; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D055815:Young Adult
D050676:Core Binding Factor Alpha 2 Subunit; D004791:Enzyme Inhibitors; C493728:RUNX1 protein, human; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D015254:DNA Modification Methylases; D001374:Azacitidine