Investigating the differential impact of autophagy activation on the heart and tumor during cardiotoxic chemotherapy

Objective: Cardiotoxicity from cancer therapy is a rising clinical issue due to a lack of cardioprotective strategies that can be safely applied to cancer patients without diminishing chemotherapeutic efficacy. Modulating autophagy, a conserved cellular homeostasis pathway, can be beneficial by reducing apoptosis in heart disease. However, the impact of upregulated autophagy on cancer and cancer therapy remains unknown, and thereby, a major obstacle in clinical translation. We aim to study the pathophysiology of autophagy in the heart and in tumor during cancer therapy. Hypothesis: Using a novel Autophagy Detecting Nanoparticle (ADN) probe developed by our lab for in vitro and in vivo fluorescence quantification of autophagy, we hypothesize that direct imaging of autophagy may predict the differential impact of autophagy modulation on apoptosis in the heart and tumor in murine and human models. Methods: Cardiomyocytes (rat H9C2, human iPSC-CMs) and breast cancer cell lines (mouse 4T1-Luc, human MDA-MB-231 and MCF7) were treated with cardiotoxic doxorubicin (Dox) with or without either autophagy-activating (rapamycin (Rp, 0.1 μM) or starvation (Stv)), or autophagy-inhibiting (chloroquine (Cq, 20 μM)) conditions for 6-96 hours. Cell viability (MTT assay and Real-Time Cell Analysis), apoptosis (Annexin V), and autophagy levels (flow cytometry with ADN) were measured. Tumor formation from implanted 4T1-Luc in BALB/c mice (n=10) was measured, and the impact of acute 24-hour Stv on apoptosis and autophagy in the heart and tumor was simultaneously investigated following Dox (15 mg/kg) treatment. Results: ADN signal showed Dox impaired autophagy in cardiomyocytes and cancer lines 4T1-Luc and MCF7. Autophagy activation significantly reduced Dox-induced apoptosis after 24 hours, improved long-term viability of cardiomyocytes, and did not adversely affect the Dox killing of 4T1-Luc and MCF7 cells. In MDA-MB-231 cells, Dox activated autophagy which remained high when co-treated with Rp, and interestingly was further augmented by Cq, presumably by triggering autosis leading to enhanced Dox efficacy. In tumor bearing mice treated with Dox, Stv restored autophagy levels and reduced apoptosis in the heart after 24 hours, and rescued heart function at 4 weeks. Stv significantly increased autophagy and apoptosis levels in tumors after 24 hours, leading to reduced tumor volume over time and showing no adverse effect of acute Stv on Dox efficacy. Conclusions: ADN imaging of autophagy levels in vitro and in vivo reveals differential heart and tumor responses to autophagy modulation during cardiotoxic cancer therapy, and may further serve as a viable biomarker for evaluating cardioprotective strategies. NIH, American Heart Association This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.