Small cell lung cancer tissue microarrays (TMA) were from US Biomax Inc. (LC818). IHC staining was performed using standard techniques described previously (26 (link)) with antibodies against PP2A A (Cell Signaling Technology) in the Pathology/Solid tumor core, The City of Hope. Briefly, each TMA was reviewed and scored by two independent pathologists on a scale of 0 to 3: 0+, no staining, no expression; 1+, weak staining, low expression; 2+, moderate staining, moderate expression; and 3+, strong staining, high expression. The IHC staining of PP2A A was examined by a pathologist who assigned a score 0+ (no staining), 1+ (5%–80% of weak stained cells), 2+ (50%–90% of moderate stained cells), 3+ (70%–100% of strong stained cells). The number of tumor cores with stage I disease (I-IA-IB) was 39 and the pathologic score assigned was between 0+ and 3+. A total of 28 tumor cores were stage II (II-IIA-IIB) and 12 were stage III/IV (IIIA-IIIB-IV). Both groups had the same range of pathologic scores as the stage I group. The TMA slide specification sheet is included in Supplementary Table S1.