Using this signature, together with TIAM1 and RAC1 expression, we performed hierarchical cluster analysis on RNA-sequencing (RNA-seq) data from 81 primary SCLC tumors (George et al., 2015) (Figure 1A), 44 circulating-tumor-cell-derived explant (CDX) models (Hodgkinson et al., 2014; Simpson et al., 2020) (Figure S1A), and 49 SCLC cell lines (Figure S1F). Here, RAC1 is linked to small cell lung carcinoma.