Abstract

S100A8 and S100A9 are two members of the S100 calcium-binding protein family, preferentially form functional heterodimers of S100A8/S100A9, and have been increasingly recognized as biomarkers in malignancies.

Recent proteomic studies revealed that S100A8 and S100A9 played pivotal roles in hematologic malignancies and elevated expression of S100A8/S100A9 implicated in glucocorticoid resistance in MLL-rearranged infant acute lymphoblastic leukemia (ALL). In addition, S100A8 proteomic expression in leukemic cells was reported to predict survival in AML patients. However, information on the gene expression level of S100A8 and S100A9 and their clinical correlation in acute myeloid leukemia (AML) is lacking.

Using the real-time quantitative RT-PCR, we analyze the transcription levels of S100A8 and S100A9 in AML patient leukemic specimens underwent pre-planned induction chemotherapy. A total of 189 patient cases at different stages of AML (excluding acute promyelocytic leukemia [APL]), including 91 newly diagnosed AML, 64 patient remission marrow specimens and 34 patient specimens as well as 20 controls without leukemia were included in the study collected from the period between 2007 and 2011.

Among the cohort of 91 newly diagnosed AML, the over all median OS was 20 months, and the median follow-up for survivors was 24 months (range: 17 to 60 months). There were significant positive correlations of transcription levels between S100A8 and S100A9 in AML patients from different stages. The expression levels of S100A8 and S100A9 in newly diagnosed and relapsed AML patients revealed no significant difference, but were both lower than those in complete remission and control group.

Patients with high transcription level of S100A8 and S100A9 were predominantly in AML with myelo-monocytic differentiation (M4, M5) whereas those with low transcription level of S100A8 and S100A9 often showed more immature cytomorphology (M0, M1), erythrocytic or megakaryocytic differentiation.

The subgroup of patient with high transcription level of S100A8 could be a predictor for inferior overall survival (OS) (P = 0.0012). High levels of transcription for both S100A8 and S100A9 in de novo AML patients could predict shorter OS than those with low levels after adjustment on their ages at diagnosis (P = 0.003).

In a multivariate analysis for OS, high S100A8 transcription was a significant prognostic factor (P =0.001) after analysis adjustment for age (P = 0.019), bone marrow blast percentage (P = 0.04) and cytogenetic classification (P = 0.05) at diagnosis.

Using a combination of S100A8 transcription level and cytogenetic risk classification, survival analysis gave result that the new stratification was highly correlated with the OS (P < 0.0001). With significantly different OS, patients from the intermediate-risk group can be divided into two subgroups (IH = cytogenetically intermediate-risk with S100A8 high transcription and IL = cytogenetically intermediate-risk with S100A8 low transcription). Patients from group IL emerged with a probability of OS similar to the cytogenetically favorable-risk group, whereas the survival curve of IH subgroup was close to the unfavorable-risk group. (Figure)
Figure

Risk stratification of de novo AML patients by a combination of age and cytogenetic characteristics with S100A8 expression levels. 1H = cytogenetically favorable-risk with S100A8 high expression, 1L = cytogenetically favorable-risk with S100A8 low expression, 2H = cytogenetically intermediate-risk with S100A8 high expression, 2L = cytogenetically intermediate-risk with S100A8 low expression, 3H = cytogenetically unfavorable-risk with S100A8 high expression, 3L = cytogenetically unfavorable-risk with S100A8 low expression.

Figure

Risk stratification of de novo AML patients by a combination of age and cytogenetic characteristics with S100A8 expression levels. 1H = cytogenetically favorable-risk with S100A8 high expression, 1L = cytogenetically favorable-risk with S100A8 low expression, 2H = cytogenetically intermediate-risk with S100A8 high expression, 2L = cytogenetically intermediate-risk with S100A8 low expression, 3H = cytogenetically unfavorable-risk with S100A8 high expression, 3L = cytogenetically unfavorable-risk with S100A8 low expression.

In conclusion, the transcription levels of S100A8 and S100A9 were significantly associated with development and prognosis of AML. Both S100A8 and S100A9 expression levels provided useful clinical information, and more importantly, S100A8 expression level significantly correlates with prognosis in addition to well-known cytogenetic risk factors, and could potentially further refine current stratification of de novo AML patients.

Disclosures:

No relevant conflicts of interest to declare.

Author notes

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Asterisk with author names denotes non-ASH members.