Journal of Carcinogenesis & Mutagenesis

Abstract

Inactivation of P16 (INK4a) Gene by Promoter Hypermethylation is Associated with Disease Progression in Chronic Myelogenous Leukaemia

Imtiyaz Ah, Mir Rashid, Sameer G, Jamsheed J, Mariyam Z, Shazia F, Prasant Y, Masroor M, Ajaz Bhat, Sheikh Ishfaq, Naveen Kumar, Khalani T, Naresh Gupta, P C Ray and Alpana Saxena

Background: Chronic Myelogenous Leukemia (CML) has a typical progressive course with transition from a chronic phase to a terminal blast crisis phase. The mechanisms that lead to disease progression remain to be elucidated. Promoter hypermethylation is one of the putative mechanisms underlying the inactivation of negative cell-cycle regulators in haematological malignancies. Therefore, aim of our study was to examine whether the methylation status of P16 (INK4a) gene is a useful biomarker in the development and progression of CML.
Material and Methods: The methylation status of p16INK4A gene was evaluated by Methylation Specific Polymerase Chain Reaction (MSP) in 200 CML patients among which, 81 were in CP-CML, 54 in AP-CML and 65 in BC-CML.
Results: The p16INK4A gene was hypermethylated in 84 of 200 (42%) of CML patients (P<0.0001). Among the three stages p16 (INK4A) promoter gene was methylated in 26% (CP-CML), 43% (AP-CML and 68% (BCCML) patient (P<0.0001). Methylation was more frequent in blastic and accelerated phase patients than in chronic phase. A significant correlation was found between p16INK4A methylation and loss of Imatinib response. Similarly higher frequency of p16INK4A methylation was reported in CML patients with haematological (P<0.02) and molecular resistances (P<0.04). Significantly higher (p<0.0001) frequency of p16INK4A promoter methylation was reported in patients with thrombocytopenia. However no correlation was found between p16INK4a hypermethylation and other clinic-pathological parameters like age, gender, BCR-ABL transcripts etc.
Conclusion: Our results suggest that p16INK4a is a primary target for inactivation by promoter methylation in the disease progression of CML patients and that its detection is useful in the follow up of patients with a high risk of developing CML and resistance to Imatinib therapy.