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Title:Characterization of novel small molecule inhibitors of FOXM1 as potential therapeutic agents for breast cancer
Author(s):Sanabria Guillen, Valeria K
Director of Research:Katzenellenbogen, Benita
Doctoral Committee Chair(s):Katzenellenbogen, Benita
Doctoral Committee Member(s):Nelson, Erik; Raetzman, Lori; Shapiro, David
Department / Program:Molecular & Integrative Physl
Discipline:Molecular & Integrative Physi
Degree Granting Institution:University of Illinois at Urbana-Champaign
Breast cancer
Abstract:Breast cancer is the most common cancer in women in the United States and the second leading cause of cancer death among women. Despite significant advances in the treatment of breast cancer, few solutions exist addressing the challenges of hormone resistance, recurrence, and metastasis, highlighting the urgent need for new molecular targets and therapies. Forkhead box M1 (FOXM1) is a cell cycle associated transcription factor that is remarkably overexpressed in breast cancers and has a biological role in all hallmarks of cancer development, from oncogenic transformation to treatment resistance and metastasis. Inhibition of FOXM1 through small interfering RNA (siRNA) depletion and other modes abrogates its cancer promoting effects, bringing FOXM1 forth as a promising target in the treatment of breast and other cancers. Despite this compelling evidence, no inhibitors of FOXM1 that have therapeutic potential have emerged due to lack of specificity and potency, and importantly, poor pharmacokinetic profiles in animals. To this end, we have identified and characterized novel inhibitors of FOXM1 that effectively suppress breast cancer cell growth and survival in vitro and in vivo. Our potential FOXM1 inhibitors displayed significantly improved potency compared to other inhibitors, as well as strong pharmacokinetic profiles with both oral and subcutaneous activity. In breast cancer xenograft models, our FOXM1 inhibitors suppressed tumor growth at both high and low dose regimens with concurrent downregulation of FOXM1 target genes. We showed that our inhibitors bind the FOXM1 protein directly and decrease its stability, resulting in the downregulation of FOXM1 protein level. Genome-wide RNA-Seq studies revealed that these inhibitors modulate expression of FOXM1-regulated transcription networks in breast cancer cells. In addition, gene networks related to the known role of FOXM1 as a master regulator of the cell cycle, including G1/S and G2/M transition, execution of S-phase and mitotic processes, DNA damage repair, and apoptosis were impacted. Consistent with this, treatment of breast cancer cells with our inhibitors results in G2/M cell cycle arrest and apoptosis via caspase 3/7 activation. Breast cancer cells selected for resistance to our lead compound NB-73 displayed a remarkable reversal of the inhibition of FOXM1-regulated gene expression and cell cycle-related pathways seen in wild type cells after treatment, reflecting the importance of these pathways to the molecular mechanism of the compound. Chemotherapy is still the only treatment available for triple negative breast cancers lacking druggable targets. Triple negative breast cancers overexpress FOXM1 compared to other breast cancer subtypes, making targeting FOXM1 particularly important in this context. Since combination therapy is the standard of care in cancer treatment, we assessed the potential of combining our novel FOXM1 inhibitors with drugs currently used to treat cancer or in clinical development to inhibit triple negative breast cancers. Our FOXM1 inhibitors synergistically suppressed triple negative breast cancer cells in combination with drugs from several classes, including cyclin-dependent kinase inhibitors, proteasome inhibitors, and others. The combination of FOXM1 inhibitors with Bortezomib, a proteasome inhibitor, displayed particularly strong inhibition of MDA-MB-231 cells through induction of G2/M arrest and apoptosis. In Rb-expressing cells MDA-MB-231 cells, the CDK4/6 inhibitor Abemaciclib synergized with our FOXM1 inhibitors to potently suppress cell proliferation. Thus, in this work we present compounds that display strong translational potential through their FOXM1-specific activity, pharmacokinetic and antitumor activity, and synergistic interaction with targeted therapies.
Issue Date:2020-11-25
Rights Information:Copyright 2020 Valeria Sanabria Guillen
Date Available in IDEALS:2021-03-05
Date Deposited:2020-12

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