Submitted May 29, 2007
Accepted December 30, 2007
Internal tandem duplication of FLT3 (FLT3/ITD) induces increased ROS production, DNA damage and misrepair: implications for poor prognosis in AML
Annahita Sallmyr, Jinshui Fan, Kamal Datta, Kyu-Tae Kim, Dan Grosu, Paul Shapiro, Donald Small, and Feyruz Rassool*
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States
Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
School of Pharmacy, University of Maryland, Baltimore, MD, United States
* Corresponding author; email: frassool{at}som.umaryland.edu.
Activating mutations of the FMS-like tyrosine kinase-3 (FLT3) receptor occur in approximately 30% of acute myeloid leukemia (AML) patients and, at least for internal tandem duplication (ITD) mutations, are associated with poor prognosis. FLT3 mutations trigger downstream signaling pathways including RAS-MAP/AKT kinases and signal transducer and activator of transcription-5 (STAT5). We find that FLT3/ITD mutations start a cycle of genomic instability whereby increased reactive oxygen species (ROS) production leads to increase DNA double strand breaks (DSB) and repair errors that may explain aggressive AML in FLT3/ITD patients. Cell lines transfected with FLT3/ITD, and FLT3/ITD-positive AML cell lines and primary cells demonstrate increased ROS. Increased ROS levels appear to be produced via STAT5 signaling and activation of RAC1, an essential component of ROS-producing NADPH oxidase. A direct association of RAC1-GTP binding to phosphorylated STAT5 (pSTAT5) provides a possible mechanism for ROS generation. A FLT3 inhibitor blocked increased ROS in FLT3/ITD cells resulting in decreased DSB and increased repair efficiency and fidelity. Our study suggests that the aggressiveness of the disease and poor prognosis of AML patients with FLT3/ITD mutations could be the result of increased genomic instability that is driven by higher endogenous ROS, increased DNA damage and decreased end-joining fidelity.
