In addition to identifying a critical role of MCU in tumor growth, we determined that MCU deletion in transformed fibroblasts diminished malignant capabilities in vitro. Our studies indicate that genetic deletion of MCU limits the ability of transformed fibroblasts to form clonally-derived spheres and invade, capabilities associated with initiation and progression of metastatic tumors (Uchida et al., 2010; Ishiguro et al., 2017), as previously observed (Tosatto et al., 2016). Here, MCU is linked to metastatic neoplasm.