Mentor Name: Linda Resar

We propose to define targetable mechanisms underlying menin inhibitor resistance in childhood acute myeloid leukemia (AML) caused by KMT2A-r fusion proteins. KMT2A-r leukemias are often refractory to therapy and therefore highly lethal in infants and children. Prior studies identified drugs to target proteins that form complexes with the KMT2A-r fusions, such as the menin protein. While this groundbreaking work led to the recent FDA-approval of the first menin inhibitor [revumenib (REV)] for children with KMT2A-r AML, resistance frequently emerges. Thus, studies to elucidate the molecular underpinnings of resistance are urgently needed. We therefore propose a novel approach by focusing on HMGA1 proteins as “molecular keys” required by KMT2A-r fusions to “unlock” the genome and activate genes required by leukemic blasts to resist therapy. In preliminary studies, we discovered that: 1) HMGA1 is overexpressed in KMT2A-r leukemia with highest levels after blasts become resistant to cytotoxic therapy. 2) Another group recently identified HMGA1 among the gene signature that becomes activated when KMT2A-r blasts become resistant to menin inhibitors (MENi). 3) HMGA1 is also a highly expressed in the leukemic stem cell signature in KMT2A-r AML mouse models. 4) Using CRISPR or short hairpin RNA (shRNA) approaches, we discovered that silencing HMGA1 disrupts proliferation and clonogenicity in KMT2A-r AML cell lines in vitro. 5) In KMT2A-r mouse implantation models, HMGA1 silencing impairs leukemic engraftment and expansion, while prolonging survival. 6) Our preliminary RNA sequencing (RNAseq) results demonstrate that HMGA1 activates KMT2A-r gene targets (HOX genes), MENi resistance genes, and cell cycle progression genes. Together, these exciting data support the following hypotheses: 1) HMGA1 acts as a “chromatin key” that unlocks the genome to activate genes required for therapy resistance by KMT2A-r, 2) HMGA1 activates therapy resistance genes by altering chromatin architecture to modulate gene expression, and, 3) Targeting HMGA1 networks will synergize with MENi therapy and trigger an anti-tumor immune attack, resulting in durable remissions in children with KMT2A-r AML. To test this, we propose the following Specific Aims: 1) To elucidate the role of HMGA1 in therapy resistance to menin inhibitors using multiomics analyses and our unique experimental models, and, 2) To test the therapeutic efficacy of targeting HMGA1 networks in KMT2A-r preclinical models. We will translate our most promising results to the clinics for children with high risk KMT2A-r-AML. This work should uncover new treatment paradigms for KMT2A-r AML.