Methylation of p15 and p16 genes in acute promyelocytic leukemia: potential diagnostic and prognostic significance.
OBJECTIVE
To investigate the frequency of p15 and p16 gene promoter methylation in acute promyelocytic leukemia (APL), and to define its value in the detection of minimal residual disease (MRD) and treatment prognostication.


METHODS
Bone marrow DNA obtained from 26 patients with APL at diagnosis and during follow-up was studied with the methylation-specific polymerase chain reaction (MS-PCR). Serial marrow DNA was studied by MS-PCR for MRD, and disease-free and overall survival were correlated with p15 methylation status at diagnosis.


RESULTS
MS-PCR for p16 and p15 gene methylation has a maximum sensitivity of 10(-4) and 10(-5). At diagnosis, 19 patients (73.1%) exhibited p15 methylation, whereas only three patients (11.5%) exhibited p16 methylation, all of whom had concomitant p15 methylation. During follow-up, p16 methylation was acquired in two patients, one during the third hematologic relapse, and the other during transformation into therapy-related myelodysplastic syndrome. Six patients were evaluated serially with MS-PCR for p15 methylation at diagnosis and at follow-up examinations. Persistent p15 methylation preceded subsequent hematologic relapses in two patients, and conversion to negative MS-PCR for p15 methylation correlated with prolonged survival in another four patients. The 5-year disease-free survival of patients with p15 methylation was significantly inferior to that of patients without p15 methylation (15% v 62.5%; P =.02), and this remained significant in multivariate analysis.


CONCLUSIONS
In APL, p15 but not p16 gene methylation is frequent. It is possible that p16 methylation is acquired during clonal evolution. p15 methylation is a potential marker of MRD and might be of prognostic significance.
University Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong. jcschin@hkucc.hku.hk
C S
CS
Chim
R
R
Liang
C Y
CY
Tam
Y L
YL
Kwong
D000206:Actuarial Analysis; D000328:Adult; D014408:Biomarkers, Tumor / Q000235:genetics*; D019175:DNA Methylation; D017931:DNA Primers; D018572:Disease-Free Survival; D005260:Female; D016147:Genes, Tumor Suppressor; D019942:Genes, p16; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000175:diagnosis* / Q000235:genetics*; D016015:Logistic Models; D008297:Male; D018365:Neoplasm, Residual; D016133:Polymerase Chain Reaction / Q000379:methods; D011401:Promoter Regions, Genetic; D016016:Proportional Hazards Models; D012680:Sensitivity and Specificity; D015996:Survival Rate
D014408:Biomarkers, Tumor; D017931:DNA Primers