Role of CD133 As a Marker of Previous Myelodysplasia in De Novo Elderly Patients with Acute Myeloid Leukemia

Conflicting results have been reported regarding the correlation between CD133, a surface marker of immature progenitors, and outcome in acute myeloid leukemia (AML). The expression of this antigen has also been reported in myelodysplastic syndromes (MDS), in particular in high-risk diseases, but always in small cohorts of patients and without a focus on the prognostic role of this antigen. Aim of our study was to establish a clinico-biologic correlation between CD133 expression and disease features at baseline in a large series of AML patients of different ages, with particular regard to the older age.Seven hundred AML patients consecutively diagnosed at a single Institution were retrospectively analyzed and enrolled in this study. There were 395 males and 305 females, with a median age of 54 years (range 1.1-90.4). A previous MDS phase was recognized in 124 patients. Several clinical and biologic features were recorded at baseline and retrospectively collected, such as age, gender, FAB and WHO morphologic classification, cytogenetic analysis, molecular alterations, hematologic parameters (Hb, platelet and WBC count), response to treatment and outcome. Overall, 157 patients expressed CD133. This first analysis was carried out on the older patient population (≥65 years) on the basis of the CD117 positivity. Seventy-three older patients expressed CD133 at baseline, whereas 36 patients were CD117+CD133-. Comparison between the two groups showed a significant prevalence of a previously recognized MDS phase in CD133+ patients (27% vs 13%, p=0.01), higher incidence of a complex karyotype or typical MDS cytogenetic aberrations (trisomy 8, del20q, del5q) (30% vs 8%, p=0.001) and of dysplastic morphologic features detectable in patients without a previous dysplastic identification (63% vs 27%, p=0.002). Forty-three patients in the CD133+ group and 21 patients in the CD133- group received intensive chemotherapy: the remission rate was 52% and 64%, respectively (p=0.06). The relapse rate was 25.5% in the CD133+ and 19% in the CD133- group, respectively (p=0.08). No differences were observed with regard to the hematologic parameters at baseline or in overall survival between the two groups. We then assessed the characteristics of cases negative for CD117, but CD133+ (13 patients) that were compared to the entire cohort of cases that were CD117+CD133+ (144 patients): again we found that, independently from the positivity for CD117, CD133 identified patients with a previously reported MDS phase (61% of patients CD117-CD133+), with a higher median age (69 years) and with dysplastic morphologic changes (100% CD117-CD133+).

Taken together, our findings strongly suggest that CD133 can identify at diagnosis a previous MDS phase. In particular, the presence of this antigen in the setting of older de novo AML patients should be used to recognize early a subset of patients who, for the associated biologic features, could benefit from the use of hypomethylating agents as first line treatment. Further analyses, aimed at identifying the prognostic role of this antigen in a large cohort of patients treated with azacitidine, are warranted.