KRAS and non-small cell lung carcinoma: MTT assays were used to evaluate the anti-proliferative effects of sorafenib and gemcitabine as single agents on EGFR-TKI-sensitive PC-9 (mutant EGFR/wild-type K-Ras) and EGFR-TKI-resistant A549 (wild-type EGFR/mutant K-Ras) NSCLC cell lines.