Expression of p16INK4a,p15INK4b,p21WAF1/Clip1 cell cycle inhibitors on blastic cells in patients with acute myeloblastic leukemia (AML) and acute lymphoblastic leukemia (ALL)

Cyclin-dependent kinases (cdk) play the important role in neoplastic transformation. Their activity depends on interaction with proteins called inhibitors. There are two groups of inhibitors: INK4 (p16INK4a, p15INK4b, p18INK4c, p19INK4d) and proteins p21WAF1/Clip1, p27Kip1, p57Kip2. Alteration of inhibitors expression was assessed in acute lymphoblastic leukemia (ALL) and in acute myeloblastic leukemia (AML), but the results are not clear. The aim of our study was to estimate p16INK4a, p15INK-4b, p21WAF1/Clip1 expression in blast cells in patients with AML and ALL by cytochemistry method and to compare with the result of treatment. Forty-two patients were included in the study, 23 with AML and 19 with ALL. Expression of inhibitors was considered as positive when detected in > 5% of blast cells. Complete remission (CR) rate in patients with positive expression p16INK4a and p15INK4b was statistically significantly higher than in patients with negative expression: for p16INK4a chi 2 = 7.78, p < 0.01, for p15INK4b, chi 2 with Yates' modification = 3.94, p < 0.05. There was no difference in CR rate in patients with positive and negative p21WAF1/Clip1 expression. Moreover the patients with simultaneous expression of three inhibitors reached CR more often than the others: chi 2 = 7.43, p = 0.01 for AML and chi 2 = 6.74, p < 0.01 for ALL. Our study indicates that estimation of p16INK4a, p15INK4b, p21WAF1/Clip1 expression in blast cells can be used as prognostic factor in acute leukemia.