The Prevalent, Features and Prognostic Impact of Deletion p16 in Patients with Adult Acute Lymphoblastic Leukemia

Background and objective: Deletion of chromosome 9p21 is a crucial event for acute lymphoblastic leukemia (ALL). 9p21.3 genes encode three cell cycle inhibitory proteins: p15INK4b, p16CDKN2A, and p14ARFT. Recently studies show that p16 (CDKN2A) alleles were hypermethylated at CpG islands in ALL patients and delation p16 was associated with poor prognosis in childhood ALL. However, the prognostic significance of the deletion p16 in adult ALL leukemia is controversial, so the aim of the present study was to investigate the prevalence, feature and specific prognostic relevance of delation p16 in Chinese ALL patients from a single center in China.

Patients and Methods: A total of 513 newly diagnosed adult ALL patients were identified retrospectively from the database of ALL between January 2008 and December 2013 at our center. We Detected delation p16 by interphase fluorescence in ituhybridization (I-FISH) and analyzed their clinical data retrospectively.

Results: Of 513 cases, the prevalence of having either heterozygous or homozygous p16 deletions was 32%. p16 deletion were identified in 27% of newly diagnosed Philadelphia positive(Ph+) patients by univariate analysis, patients with p16 deletion had no significant difference compared with wild-type patients in terms of sex, age, white blood cells (WBC) count at diagnosis,BM blast percentage,chromosome karyotype,extra infiltration and CR I rate. The patients with p16 deletion was more likely to relapse comparaed with wild-type patients (P=0.03), and at relapse, we found a strong trend in the detection rate of p16 loss (41%) compared with diagnosis (P=0.01), suggesting that loss of this genomic region may be involved in disease progression. Of note, in newly diagnosed Ph+ALL with delation p16 were likely relapse even in the patients who treated with allogeneic hematopoietic stem cell transplantation (P=0.03). In addition, deletion p16 were significantly associated with poor outcomes in terms of overall survival (P=0.01), disease free-survival (P< 0.001), and cumulative incidence of relapse (P< 0.001).

Conclusion: In our study, the absence of p16 expression seems to a poor prognostic marker in adult ALL patients. However, how to improve the survival of these patients need further study.