Presenter: Anyeld Ubeda
Acute myeloid leukemia (AML) is the most prevalent myeloid disorder in adults with high mortality rates due to patient relapse. AML originates in the hematopoietic stem and progenitor cells and is characterized by the increase of immature myeloblasts or “blasts” in circulation overcrowding healthy cells and space in the bone marrow. In this project, we focused on gene silencing via RNA interference (RNAi) with silencing RNA (siRNA) as a targeted therapeutic approach, able to be directed to specific genetic mutations or genes that get over-expressed in leukemia cells compared to healthy tissues. As the specificity of RNAi therapy is given by the siRNA sequence, using this type of approach can offer alternatives and potent combinations to treat AML other than relying on protein inhibitors or chemotherapeutic agents with broad mechanisms of action. However, even though the use of siRNAs has great potential for therapeutic applications some obstacles prevent it from being readily used, mainly that it needs a delivery system.
Given their ease of synthesis and chemical flexibility with the incorporation of countless functional groups, we used modified lipopolymers to address siRNA delivery. More specifically, we used low molecular weight polyethyleneimine (PEI) modified with aliphatic groups, which have shown to make PEI into an effective delivery agent for AML cells in the past. By analyzing a library of modifications, we identified two main substitutions that were able to consistently and effectively transfect leukemic stem cell models and primary samples. Next, we utilized the modified lipopolymers to downregulate the expression of genes that target the proliferation and apoptosis of the leukemic cells and focused on the BCL2 Like 12 (BCL2L12) and Baculoviral IAP Repeat Containing 5 (BIRC5 or survivin) genes. Also, by optimizing the siRNA delivery schedule we were able to enhance the effect of the siRNAs on proliferation over a period of 10 days. In addition, we showed how after selecting the proper modifications for PEI we are also able to target multiple genes including MAP2K3, CDC 20, and SOD-1 and observed decreased proliferation in the desired cells. Our studies demonstrated the versatility of siRNA delivery with modified PEI to elicit an effect in leukemic cells that are difficult to treat as well as paramount therapeutic targets for AML, offering an alternative for more precise and targeted treatment options.