Peripheral blood mononuclear cells exhibit increased mitochondrial respiration after adjuvant chemo- and radiotherapy for early breast cancer

Background Adjuvant chemo- and radiotherapy cause cellular damage not only to cancerous but also to healthy dividing cells. Antineoplastic treatments have been shown to cause mitochondrial respiratory dysfunction in non-tumorous tissues, but the effects on circulating human peripheral blood mononuclear cells (PBMCs) remain unknown. Aim We aimed to identify changes in mitochondrial respiration of PBMCs after adjuvant chemo- and radiotherapy in postmenopausal early breast cancer (EBC) patients and relate these to metabolic parameters of the patients. Methods Twenty-three postmenopausal women diagnosed with EBC were examined before and shortly after chemotherapy treatment often administered in combination with radiotherapy (n=18). Respiration (O 2 flux per million PBMCs) was assessed by high-resolution respirometry of intact and permeabilized PBMCs. Clinical metabolic characteristics were furthermore assessed. Results Respiration of intact and permeabilized PBMCs from EBC patients was significantly increased after adjuvant chemo- and radiotherapy ( p =6×10 −5 and p =1×10 −7 , respectively). The oxygen flux attributed to specific mitochondrial complexes and respiratory states increased by 17-43% compared to before therapy commencement. Leukocyte counts ( p =1×10 −4 ), hemoglobin levels ( p =0.0003), and HDL cholesterol ( p =0.003) decreased while triglyceride ( p =0.01) and LDL levels ( p =0.02) increased after treatment suggesting a worsened metabolic state. None of the metabolic parameters correlated significantly with PBMC respiration. Conclusion This study shows that mitochondrial respiration in circulating PBMCs is significantly increased after adjuvant chemo- and radiotherapy in postmenopausal EBC patients. The increase might be explained by a shift in PBMC subpopulation proportions towards cells relying on oxidative phosphorylation rather than glycolysis or a generally increased mitochondrial content in PBMCs. Both parameters might be influenced by therapy-induced changes to the bone marrow or vascular microenvironment wherein PBMCs differentiate and reside.