CHRNB4 and small cell lung carcinoma: It was also found that nAChR genes CHRNA3, CHRNA5, and CHRNB4 were necessary for the survival of small cell lung cancer (SCLC) and that α-conotoxin AuIB, a selective antagonist of α3β4 nAChR, inhibited the survival of SCLC cells [19,20].