TRIM28 and neoplasm: Interestingly, we found that XAF1 is a novel substrate of TRIM28 and that EGF-induced TRIM28 protects tumor cells from etoposide-induced apoptosis more significantly in XAF1+/+ versus XAF1−/− cells, indicating that TRIM28 exerts anti-apoptotic effect in a highly XAF1-dependent fashion.