On the NE transformation side, reports indicate that MAPK induction may be incompatible with NE SCLC, where it induces cell cycle arrest and senescence.181 These results indicate that EGFR (or receptor tyrosine kinase) re-expression, which would lead to MAPK signaling, may be challenging in SCLC tumors. Here, NTRK1 is linked to small cell lung carcinoma.