Malignant cells from breast cancer and other common cancers such as prostate and melanoma may persist in bone marrow as quiescent, non-dividing cells that remain viable for years or even decades before resuming proliferation to cause recurrent disease. This phenomenon, referred to clinically as tumor dormancy, poses tremendous challenges to curing patients with breast cancer. Quiescent tumor cells resist chemotherapy drugs that predominantly target proliferating cells, limiting success of neo-adjuvant and adjuvant therapies. We recently developed a 3D spheroid model of quiescent breast cancer cells in bone marrow for mechanistic and drug testing studies. We combined this model with optical imaging methods for label-free detection of cells preferentially utilizing glycolysis versus oxidative metabolism to investigate the metabolic state of co-culture spheroids with different bone marrow stromal and breast cancer cells. Through imaging and biochemical assays, we identified different metabolic states of bone marrow stromal cells that control metabolic status and flexibilities of co-cultured breast cancer cells. We tested metabolic stresses and targeted inhibition of specific metabolic pathways to identify approaches to preferentially eliminate quiescent breast cancer cells from bone marrow environments. These studies establish an integrated imaging approach to analyze metabolism in complex tissue environments to identify new metabolically-targeted cancer therapies.
Keywords: Optical metabolic imaging; bone marrow; fluorescence lifetime imaging; metastasis; quiescence.