POU2F3 and small cell lung carcinoma: To test whether Slit2/Robo1 was SCLC subtype‐specific, we sub‐divided tumors based on the expression of transcription factors, ASCLC1 (SCLC‐subtype A), POU2F3 (SCLC‐subtype P), NEUROD1 (SCLC‐subtype N), and YAP1 (SCLC‐subtype Y) (Table S1) [47].