Deletions of p15 and/or p16 genes as a poor-prognosis factor in adult T-cell leukemia

PURPOSE To determine the frequency of the deletions of p15/p16 genes in adult T-cell leukemia (ATL) cells and to evaluate their value in the diagnosis of clinical subtypes of ATL patients and the prediction of their clinical outcome. MATERIALS AND METHODS Peripheral-blood samples from 114 patients with ATL were examined by Southern blot analysis. In five chronic-type patients who showed disease progression to acute type, serial samples also were examined. RESULTS Among 114 patients, 28 (24.6%) showed the deletions of p15 and/or p16 genes. The results were well correlated with the clinical subtypes. Patients with deleted p15 and/or p16 genes had significantly shorter survival times than the patients in whom both genes were preserved (P < .0001). A similar decline in survival time was observed in the analyses within the same subtypes. In multivariate analysis using the Cox proportional hazard model, the deletions of p15 and/or p16 genes emerged as an independent prognostic indicator. Moreover, three of the five chronic-type patients who progressed to acute type lost the p16 gene alone or both the p15 and p16 genes at their exacerbation phase. CONCLUSION The results suggest the following: (1) that the deletions of p15 and/or p16 genes play a key role in the progression of ATL; and (2) that these deletions are reliable prognostic factors that predict shortened survival times.