PPP1R1B and small cell lung carcinoma: Conversely, shRNA-mediated depletion of DARPP-32 isoforms resulted in increased caspase-3 and PARP-I cleavage in DMS-53 (Fig. 1e) and H1048 (Fig. 1f) human SCLC cells, which is indicative of increased apoptosis upon silencing of DARPP-32 proteins.