RPS21 and prostate cancer: Ribosomal protein s21 (RPS21) is a ribosome-related protein, which has been shown to play an important role in ribosomal biogenesis and may affect the occurrence and development of osteosarcoma and prostate cancer through the RAS/MAPK pathway (Arthurs et al., 2017; Fan et al., 2018; Liang et al., 2019; Sawyer et al., 2020; Wang et al., 2020).