PPP2R1B and neoplasm: PPP2R1B has been characterized as a tumor suppressor.28 As a constant regulatory subunit of the PP2A complex, PPP2R1B is crucial to the function of PP2A, a well-established phosphatase regulating numerous signaling pathways involved in cell proliferation, signal transduction and apoptosis.42 To determine whether PPP2R1B modulates 5-FU-induced apoptosis, its expression was knocked down by two independent siRNAs, which demonstrated robust effect in HCT116 and GEO cells, resulting in at least 90% reduction of PPP2R1B expression (Figure 6a).