CHRNB4 and small cell lung carcinoma: All the siRNAs that yielded > 90% knockdown levels produced corresponding decreases in SCLC cell viability (n = 5 each, Figure 1B), suggesting that expression of CHRNA3, CHRNA5, and CHRNB4 is vital for SCLC cell viability, at least in the context of the DMS-53 cell line.