Survivin is highly expressed in CD34(+)38(-) leukemic stem/progenitor cells and predicts poor clinical outcomes in AML

Abstract

Survivin, a member of the inhibitors of apoptosis protein family, plays important roles in cell proliferation and survival and is highly expressed in various malignancies, including leukemias. To better understand its role in acute myeloid leukemia (AML), we profiled survivin expression in samples obtained from 511 newly diagnosed AML patients and in CD34(+)38(-) AML stem/progenitor cells using a validated reverse-phase protein array; we correlated its levels with clinical outcomes and with levels of other proteins in the same sample set. We found that survivin levels were higher in bone marrow than in paired peripheral blood leukemic cells (n = 140, P = .0001) and that higher survivin levels significantly predicted shorter overall (P = .016) and event-free (P = .023) survival in multivariate Cox model analysis. Importantly, survivin levels were significantly higher in CD34(+)38(-) AML stem/progenitor cells than in bulk blasts and total CD34(+) AML cells (P < .05). Survivin expression correlated with the expressions of multiple proteins involved with cell proliferation and survival. Particularly, its expression strongly correlated with HIF1α in the stem/progenitor cell compartment. These results suggest that survivin is a prognostic biomarker in AML and that survivin, which is overexpressed in AML stem/progenitor cells, remains a potentially important target for leukemia therapy.

Figure 1

Comparison of survivin levels in paired PB and BM samples. (A) Survivin levels in 140 paired PB and BM samples were determined by PRRA and compared by paired t test (P = .0001) and (B) Pearson product-moment correlation analysis (correlation coefficient = 0.24, P = .004).

Figure 2

Comparison of survivin levels in paired samples from patients at diagnosis and relapse. (A) Survivin levels in 47 paired new diagnosis and relapse samples were determined by PRRA and compared by paired t test (P = .64) and (B) Pearson product-moment correlation analysis (correlation coefficient = -0.017, P = .908).

Figure 3

Comparison of survivin levels in bulk blasts, CD34⁺ AML cells, and CD34⁺38⁻ AML cells. (A) CD34⁺ and CD34⁺38⁻ cells were isolated from blasts of 37 AML patient samples. Survivin levels in bulk, CD34⁺ and CD34⁺38⁻ cells were determined by RPPA and compared. (B) For direct comparison of survivin levels in CD34⁺ cells and CD34⁺38⁻ cells of paired samples, a line graph is shown.

Figure 4

Correlation of survivin expression levels with the levels of other proteins in samples from 511 newly diagnosed AML patients and in CD34⁺38⁻ cells isolated from blasts of AML patients. (A) Levels of survivin and 206 other proteins were determined by RPPA in the same sample set of 511 newly diagnosed AML samples. The expression level of survivin was correlated with the expression of 206 proteins and those with Pearson correlation −0.2 ≥ R ≥ 0.2 (P < .0001) are shown. (B) Levels of survivin and 120 other proteins were determined by RPPA in CD34⁺38⁻ cells isolated from blasts of 37 AML patients. The expression level of survivin was correlated with the expression of 120 other proteins and those with Pearson correlation −0.4 > R > 0.4 (P ≤ .01) are shown.