SXR interacts with RXR in cells in a SN-38-dependent manner. LS180 and HepG2 cells were treated with 10 μM rifampicin (RIF), 10 ng/ml SN-38 (SN) or 1 μg/ml CPT-11 (CPT) for 4 h. Cell extracts were immunoprecipitated (IP) with either IgG (IP control) or anti-SXR (IP SXR) in the presence of vehicle (ctl), rifampicin, SN-38 or CPT-11. Association of the endogenous RXR with the anti-SXR precipitate was detected by WB using anti-RXR antibody. Input indicates endogenous RXR present in 5% of total cell lysates used in each IP. To ensure equal amounts were precipitated, WB using anti-SXR was also performed.