It has been reported that upon 24hrs of Erlotinib treatment in NSCLC cells, phosphorylation of STAT3 level increased in all the cell lines that express activating EGFR mutants, except HCC827 which lacks the STAT3 feedback loop, suggesting the genetic background of HCC827 may be different in terms of STAT3 signal pathway regulation [24]. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.