Identification of therapeutic targets in acute myeloid leukaemia expressing the mutant RAS oncogene

Mutational activation of RAS is one of the most common molecular abnormalities associated with acute myeloid leukaemia (AML). Normal human haematopoietic progenitor cells (HPC) expressing mutant RAS overproduce ROS due to NADPH oxidase (NOX) activation and this promotes the proliferation of these cells as well as AML blasts. The mechanisms by which ROS promote proliferation is however unclear. The current study investigated the effect of RAS-induced ROS production on gene expression in normal HPC using gene expression profiling (GEP) and assessed whether ROS-induced gene expression changes contributed to the pro-proliferative phenotype. In order to determine the ROS-specific GEP, Affymetrix Human Exon 1.0ST arrays were used for the comparison of mutant RAS and control cells cultured in the presence or absence of the NOX inhibitor, DPI, which strongly suppressed the production of ROS. This analysis showed that RAS changed the expression of 342 genes. Of these, 24 genes were specifically altered in response to ROS production by these cells and amongst these increased expressions of genes of the glycolytic pathway were prominent. To establish the functional significance of up-regulated expression of glycolytic enzymes, aldolase C (ALDOC) was investigated since it showed greatest induction with ROS. ALDOC was directly induced by physiological levels of ROS in both HPC and AML cell lines. Further, overexpression of ALDOC demonstrated that its overexpression promoted the proliferation and serum-independent survival of leukaemic cell lines. Conversely, antiproliferative effects were observed when ALDOC was knocked-down in cells known to have high levels of constitutive ROS production. Given the high frequency of ROS production in AML, this study provides a plausible mechanism of enhanced glycolysis seen in this disease and suggests that agents restoring the redox environment could be used to correct metabolic imbalances which contribute to treatment resistance