Acute myeloid leukemia (AML) is a heterogeneous disorder, which is characterized by chromosomal abnormalities and genetic alterations. Cytarabine (Ara-C) is the most commonly used nucleoside analog for treatment of AML. However, the use of Ara-C is associated with two important clinical complications namely, inter-patient variability in response and development of intrinsic resistance. The inter-patient variability in response can be partly associated with polymorphisms in proteins that are required for intracellular uptake and activation of Ara-C to its phosphorylated form. Apart from genetic polymorphisms, expression of proteins involved in the uptake, activation, and inactivation of Ara-C have been shown to correlate with the overall patient survival. Over the past decade, various studies have identified microRNAs as important post-transcriptional regulators of gene expression. However, there are no studies till date that have identified key miRNAs involved in regulation of Ara-C pathway genes. Identification of these miRNAs will help in targeting these miRNAs to further understand inter-patient differences in gene expression. Additionally, drugs can also influence gene expression. However, there is critical gap in literature regarding role of Ara-C in inducing changes in gene expression. Understanding the dynamics of gene expression due to miRNAs and drug-induced changes would help open new opportunities for development of improved treatment strategies.
Thus, the objective of this study is to understand the role of microRNAs in altering cytarabine cytotoxicity by influencing expression of pharmacokinetics (PK) and pharmacodynamics (PD) genes (n=18) in AML cell lines representing different risk groups. We evaluated genome-wide miRNA expression in 7 AML cell lines from different risk groups (favorable risk group: Kasumi-1, ME-1; intermediate risk group: AML-193, KG-1; adverse risk group: HL-60, MV-4-11, MOLM-16). We also evaluated the impact of cytarabine-induced gene expression changes in these AML cell lines. The gene expression changes were correlated with the in vitro chemosensitivity.
Our preliminary results indicate that there was a significant correlation between the baseline miRNA expression for 16 miRNAs and Ara-C IC50 values (selected shown in Figure 1). We also observed that 57 microRNAs were associated with gene expression levels of the selected 18 Ara-C pharmacogenes (selected shown in Figure 1). Four miRNAs (miR-425-5p, miR-517a-3p, miR-519b-5p+hsa-miR-519c-5p, miR-522-3p) were found to be significantly associated with both gene expression and Ara-C IC50 values. We found that there were significant changes in gene expression of Ara-C pathway genes following treatment with 1uM or 10uM Ara-C. Briefly, there were significant changes in DCK, SLC29A1, CTPS1, CMPK1, NME1 and XRCC1 expression when treated with 10uM Ara-C and RRM2, NME1 and XRCC1 expression when treated with 1uM Ara-C.
In conclusion, drug-induced changes in gene expression and miRNAs expression were found to correlate with chemosensitivity of AML cell lines. The preliminary results from our study help provide an insight into potential/additional molecular mechanisms associated with resistance observed in AML patients. Such knowledge is clinically significant, as identification of factors that contribute to the variable drug response would help in understanding and thus improving the variability in efficacy associated with cytarabine therapy.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.