We report that in HL-60 cells, by using a highly quantitative analysis of a set of genes found to be abnormally expressed in AML, polymerase chain reaction (PCR)-amplified p16 gene promoter molecules (each with 15 CpG sites), exhibited a CpG methylation level of 0-4% in untreated cells, which increased to 4-21% after treatment with ATRA for seven days.
H3K27me3, as well as EZH2, extends throughout p14ARF and p16INK4a, indicating that polycomb repression of p15INK4b is a common feature in all AML blasts irrespective of the DNA methylation status of the gene.
We recently showed that, unlike healthy cells, acute myeloid leukemia (AML) derived blasts show a down-regulation of p16(INK4a) mRNA with increasing age.
In contrast to the induced p16(INK4A) expression that is associated with physiologic aging, p16(INK4A) is down-regulated in AML samples of patients with increasing age.
Promoter methylation of p16 was detected in 85% of acute lymphocytic leukemia (ALL), 83% in acute myeloid leukemia (AML) whereas no methylation was detected in chronic myeloid leukemia (CML) in blast crisis.
DAP kinase methylation was detected in four (16%) ALL patients. p14 and Apaf-1 methylation was not detected in any of the 32 cases of acute promyelocytic leukaemia (APL), 50 cases of other subtypes of acute myeloid leukaemia (AML), and 25 cases of acute lymphoblastic leukaemia.
Myc expression in the context either of Arf/Ink4a loss or Bcl-2 coexpression induced a mixture of acute myeloid and acute lymphoid leukemias (AML+ALL).
At diagnosis, p15 methylation occurred in 29 (58%) AML patients, and 10 (40.0%) ALL patients. p16 methylation occurred in two (4%) AML and two (8%) ALL patients.
Our results suggest: a) increased levels of both p16INK4a and p14ARF may participate in the pathogenesis of AML, b) that high p14ARF mRNA expression might influence p16INK4a transcription and c) that post-transcriptional regulatory mechanisms are important for p14ARF expression.
Apart from the strong phenotypic impact of addition of acute myeloid leukemia/myelodysplasia-associated translocations and inversions, such as inv(3)(q21q26), t(3;21)(q26;q22), and t(15;17)(q22;q12-21), in CML BC, only a few significant differences between myeloid and lymphoid BC are discerned, with i(17q) and TP53 mutations being more common in myeloid BC and monosomy 7, hypodiploidy, and CDKN2A deletions being more frequent in lymphoid BC.
The methylation-specific polymerase chain reaction (MS-PCR) was used to analyze p15 and p16 gene methylation in 49 cases of acute lymphoblastic leukemia (ALL) and 29 cases of acute myelogenous leukemia (AML).
These results revealed the frequent methylation of p16 and p15 genes in B-ALL and AML despite a low frequency of p16 and p15 deletions and mutations in these leukemias.
We also demonstrated for the first time concomitant p16 and p15 methylation in 22% (8/37) of adults with AML or ALL, exclusively in those with M2, M4, or L2 subtypes.
All patients with follicular lymphoma (FL), myeloma or acute myeloid leukemia (AML) expressed p14ARF while nine of 23 patients with diffuse large B cell lymphoma (DLBCL) lost p14ARF expression.
We identified homozygous deletion of p16 and p15 genes in five (19%) of 27 acute lymphoblastic leukemias (ALLs) and in two (11%) of 19 acute myeloid leukemias (AMLs).
We conclude that MTS1 shows a significantly higher expression in leukemic than in normal peripheral blood cells, that deletion of MTS1 is not a frequent event in AML, and that its expression is not significantly correlated with outcome of the disease.