PT33 inhibited nuclear deubiquitinase activity which increased after IR in CRC cells. (A, B) Treatment schemes of 2D-adherent, 3D-spheroid (A) and xenograft (B) models. IR, ionizing radiation. (C) Relative deubiquitinating activity of whole cell lysates (WCL) or nuclear lysates (NL) from CRC cells. The DUB activity was calculated as the AMC fluorescence increment (folds) per minute and normalized to the corresponding control group, similarly hereinafter. (D, E) The relative deubiquitinating activity of NL from HCT116 (D) and HT-29 (E) was treated in 2D-adherent model as in (A). After the treatment and culture, cells were collected and NL was extracted. NL was treated with various DUB inhibitors (2 μmol/L) for 1 h (DMSO as a vehicle control), and the DUB activities were detected. Data are represented as mean ± SD (n = 3); P values were determined by Student's t test.