Given that we previously reported (i) a dependence of mt tRF levels on the components of miRNA pathway Dicer and Ago2 and (ii) a major accumulation of mt tRFs in mitochondria from osteosarcoma 143B (WT and MELAS) cybrids (Meseguer et al., 2019), we decided to investigate whether those proteins are located within mitochondria of these cells. The gene discussed is AGO2; the disease is osteosarcoma.