Ott_a_238143 5241..5255

1Vascular and Genomic Center, Changhua Christian Hospital, Changhua 50094, Taiwan; 2Department of Medicine, College of Medicine, China Medical University, Taichung 40447, Taiwan; 3Comprehensive Breast Cancer Center, Changhua Christian Hospital, Changhua 50094, Taiwan; 4Department of Medical Research, Changhua Christian Hospital, Changhua 50094, Taiwan; 5Department of Neurology, Changhua Christian Hospital, Changhua 50094, Taiwan; 6School of Chinese Medicine, Graduate Institute of Chinese Medicine, Graduate Institute of Integrated Medicine, College of Chinese Medicine, Research Center for Chinese Medicine and Acupuncture, China Medical University, Taichung 40447, Taiwan Background: The transfer of whole mitochondria has been demonstrated to be beneficial for treating breast cancer because it induces apoptosis and drug sensitivity; however, in vivo evidence of this benefit remains scant. The present study compared the transplantation of mitochondria with instinctive (Mito) and membrane-fused morphologies induced by Pep-1 conjugation (P-Mito) using a mouse model of triple-negative breast cancers. Materials and Methods: Mice with advanced severe immunodeficiency received orthotopic implantation of MDA-MB-231 human breast cancer cells followed by transplants of 5-bromo-2ʹ-deoxyuridine (BrdU)-labeled Mito or P-Mito (200 μg [10 μg/μL]) through intratumoral injection at multiple points once a week for 4 weeks. Results: After 1 month of consecutive treatment, 8.2% and 14.2% of the BrdU-labeled mitochondria were preserved in tumors of the Mito and P-Mito groups, respectively. Both Pep-1 and P-Mito treatments reduced tumor weight (21.7% ± 2.43% vs 40.6% ± 2.28%) and led to marked inhibition of Ki67 staining and angiogenesis. However, only the P-Mito group exhibited obvious necrosis and DNA fragmentation accompanied by an altered tumor microenvironment, which included reduced oxidative stress and size of cancer-associated fibroblast populations and enhanced immune cell infiltration. Transmission electron microscopy images further revealed an elongated network of perinuclear mitochondria fused with a few peripheral mitochondria in the nonnecrotic area in the P-Mito group as well as increases in mitochondrial fusion proteins and parkin compared with mitochondrial fission proteins. Conclusion: In this study, the results of mitochondrial transplantation emphasized that the facilitation of mitochondrial fusion is a critical regulator in breast cancer therapy.