Although the precise role of Arl15 in tumorigenesis requires further investigation, our current data are consistent with what has been documented about the TGFβ signaling pathway in the metastasis of cancers (Derynck and Budi, 2019; Hao et al., 2019; Lamouille et al., 2014; Massagué, 2012; Schmierer and Hill, 2007; Seoane and Gomis, 2017), thus further supporting Arl15 as a positive and essential regulator for the complete activity of this pathway. The gene discussed is TGFB1; the disease is cancer.