Tirzepatide attenuates mammary tumor progression in diet-induced obese mice

We report for the first time an anticancer benefit of tirzepatide-a dual glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide receptor agonist-in a model of obesity and breast cancer in female mice. Long-term tirzepatide treatment induced weight loss, mitigated obesity-driven changes in circulating metabolic hormone levels, and suppressed orthotopic E0771 mammary tumor growth. Relative to tirzepatide, chronic calorie restriction, an established anticancer intervention in preclinical models, promoted even greater weight loss, systemic hormonal regulation, and tumor suppression. We conclude that tirzepatide represents a promising pharmacologic approach for mitigating the procancer effects of obesity. Moreover, strategies promoting greater weight loss than achieved with tirzepatide alone may augment the anticancer benefits of tirzepatide.

Regulation of IGF1R by MicroRNA-15b Contributes to the Anticancer Effects of Calorie Restriction in a Murine C3-TAg Model of Triple-Negative Breast Cancer

Calorie restriction (CR) inhibits triple-negative breast cancer (TNBC) progression in several preclinical models in association with decreased insulin-like growth factor 1 (IGF1) signaling. To investigate the impact of CR on microRNAs (miRs) that target the IGF1/IGF1R pathway, we used the spontaneous murine model of TNBC, C3(1)/SV40 T-antigen (C3-TAg). In C3-TAg mice, CR reduced body weight, IGF1 levels, and TNBC progression. We evaluated the tumoral expression of 10 miRs. CR increased the expression of miR-199a-3p, miR-199a-5p, miR-486, and miR-15b. However, only miR-15b expression correlated with tumorigenicity in the M28, M6, and M6C C3-TAg cell lines of TNBC progression. Overexpressing miR-15b reduced the proliferation of mouse (M6) and human (MDA-MB-231) cell lines. Serum restriction alone or in combination with low levels of recombinant IGF1 significantly upregulated miR-15b expression and reduced Igf1r in M6 cells. These effects were reversed by the pharmacological inhibition of IGFR with BMS754807. In silico analysis using miR web tools predicted that miR-15b targets genes associated with IGF1/mTOR pathways and the cell cycle. Our findings suggest that CR in association with reduced IGF1 levels could upregulate miR-15b to downregulate Igf1r and contribute to the anticancer effects of CR. Thus, miR-15b may be a therapeutic target for mimicking the beneficial effects of CR against TNBC.

Abstract 3010: Targeting metabolic pathways through pharmacological and chemotherapeutic interventions to improve triple-negative breast cancer therapy

Triple-negative breast cancers (TNBCs) lack targeted therapies, leaving surgery and systemic chemotherapy as current standard approaches for treatment. However, chemotherapy resistance is a major clinical challenge. Stimulation of receptor tyrosine kinases such as insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF-1R) activates the protein kinase A (PKA), mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling cascades. Activation of these pathways is observed in the majority of TNBC tumors and promotes pro-proliferative signaling. Thus IGF-1R/IR are potential therapeutic targets in TNBC, but clinical trials of anti-IGF-1R/IR therapies have consistently shown minimal and often heterogeneous therapeutic responses. Our objective was to determine whether metabolic reprogramming achieved by combination regimens, specifically the IGF-1R/IR inhibitor BMS-754807 and/or treatment with the platinum-based chemotherapeutic agent, carboplatin, promotes autophagy induction and sensitizes cancer cells to autophagy inhibition. Cytotoxicity of BMS-754807, alone or in combination with carboplatin and/or the autophagy inhibitor, hydroxychloroquine, was assessed in murine (E0771, metM-Wntlung, B6C3TAg 2.51) and human (MDA-MB-231, MDA-MB-468) models of TNBC using MTT assays. Analysis of mitochondrial mass was measured in cells stained with MitoTracker Green FM using flow cytometry. Autophagic flux was measured with an mCherry-EGFP-LC3B tandem fluorescent protein. BMS-754807 (10μM) significantly induced 22-51% cytotoxicity in all cell lines tested, with E0771 cells showing the strongest response. Treatment with BMS-754807 (2.5µM) significantly increased mitochondrial mass (31%) compared to untreated cells. In addition, co-treatment with BMS-754807 and carboplatin further suppressed cell viability and regulated phosphorylation of the double-stranded DNA damage response proteins γ;-H2AX and Chk2. Co-treatment with BMS-754807 and carboplatin also altered the GFP/RFP ratio in LC3-expressing cells, suggesting modulation of autophagic flux. Finally, the addition of the autophagy inhibitor hydroxychloroquine further induced cytotoxicity when coupled with BMS-754807 and carboplatin. This work indicates that IGF-1R/IR inhibition remodels metabolism in TNBC cells, potentially synergizing with carboplatin to induce double stranded DNA damage. Moreover, the combination of IGF-1R/IR and carboplatin can further collaborate with autophagy inhibition to strongly suppress TNBC cell growth. We conclude that inhibiting nutrient-sensing metabolic pathways such as IGF-1R/IR in combination with chemotherapy and/or autophagy inhibition warrants additional study as a strategy to improve therapeutic responses in women with TNBC.

Citation Format: Alyssa N. Ho, Violet A. Kiesel, Scott P. Connelly, Michael F. Coleman, Stephen D. Hursting. Targeting metabolic pathways through pharmacological and chemotherapeutic interventions to improve triple-negative breast cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3010.