Prognostic Value of the Expression of Phosphatase and Tensin Homolog and CD44 in Elderly Patients with Refractory Acute Myeloid Leukemia

The leukemic stem cell marker CD44, has been reported to have prognostic significance in hematological malignancies. The present study therefore aimed to evaluate whether the expression levels of CD44 and the associated pathway components are associated with the survival rate of elderly patients with refractory acute myeloid leukemia (AML). A total of 20 elderly patients diagnosed with refractory AML were divided into two groups, following induction chemotherapy: Complete remission (CR, n=9) and non-remission (NR. n=11). Bone marrow biopsy specimens were collected, expression levels of CD44, phosphatase and tensin homolog (PTEN), mammalian target of rapamycin (mTOR) and nuclear factor-κB (NF-κB) were analyzed by immunohistochemistry and the captured images were analyzed in a blinded manner using Image Pro Plus software, version 6.0. The overall survival rates (OS) of the patients were then analyzed with log rank, and the correlation between CD44, PTEN, mTOR and NF-κB expression levels and patients survival rates were statistically analyzed using Pearson's method. Significant differences were observed between the CR and NR groups for PTEN (P=0.025) and CD44 (P=0.020) expression levels. Positive CD44 expression was significantly correlated with poor overall survival, with a hazard ratio of 6.281 (95% CI, 1.78-22.12; P=0.0042). The mean OS was 4.00 months for patients that demonstrated positive CD44 expression, compared with 9.27 months for patients that demonstrated negative CD44 expression. A tendency towards reduced survival rates was also observed in patients negative for PTEN expression, when compared with that of PTEN-positive patients. The mean OS was 4.81 months in PTEN-negative patients vs. 8.8 months in PTEN-positive patients, with a hazard ratio of 2.689 (95%CI, 0.89-8.08; P=0.078). Patients that exhibited PTEN-positive and CD44-negative expression, survived significantly longer than patients that demonstrated PTEN-negative and CD44-positive expression (mean OS, 9.86 vs 2.67 months; hazard ratio=0.037; 95% CI, 0.006-0.222, P=0.0006). The expression levels of NF-κB and mTOR were slightly increased in the NR group compared with those of the CR group, although no significant differences were identified. PTEN and CD44 expression levels demonstrated trends towards negative correlation. In conclusion, the expression levels of CD44 and PTEN may be useful markers to predict the prognosis of elderly patients with refractory AML.