SPIN1 and cancer: Under the condition of low SPIN1 level, nucleolar uL18 escapes from the nucleolus into the nucleoplasm, and works together with uL5 to bind MDM2 and to inhibit its E3 ubiquitin ligase activity toward p53, consequently leading to p53 activation and p53-dependent cell growth arrest and apoptosis, suppressing cancer cell survival (Figure 7A).