Co-existence of PHF6 and NOTCH1 mutations in adult T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) results from the collaboration of multiple genetic abnormalities in the transformation of T-cell progenitors. Plant homeodomain finger protein 6 (PHF6) has recently been established as a key tumor suppressor, which is mutated in T-ALL; however, the clinical significance of PHF6 mutations has not been fully determined in adult T-ALL. In the present study, amplification of the PHF6 exons was performed, followed by DNA sequencing to identify the genomic mutations and examine the expression of PHF6 in adult patients with T-ALL. The correlation between PHF6 mutations and clinical features was also analyzed using a χ(2) test, and between PHF6 mutations and survival curve using the Kaplan-Meier methods. PHF6 mutations were detected in 27.1% of the Chinese adults with T-ALL (16/59), 10 of which were found to be novel mutations. A significantly lower expression level of PHF6 was observed in T-ALL patients with PHF6 mutations compared with those without mutations. Of the observed mutations in PHF6, 6/16 were frame-shift mutations, indicating a PHF6 dysfunction in those patients. Of note, PHF6 mutations were found to be significantly associated with older age, lower hemoglobin levels, higher frequency of CD13 positivity and higher incidence of splenomegaly or lymphadenopathy. Furthermore, PHF6 mutations were found to be significantly correlated with Notch homolog 1, translocation-associated (Drosophila) (NOTCH1) mutations. The patients with T-ALL with co-existence of the two mutations had a significantly shorter event-free survival and a poor prognosis. The present results indicated that PHF6 is inactivated in adult T-ALL, due to its low expression and mutations. The present data indicated the synergistic effect of PHF6 and NOTCH1 mutations, as well as their co-existence, on the oncogenesis of adult T-ALL, and their potential as a prognostic marker for the disease.