To further investigate the mechanism of erlotinib resistance in NSCLC, the transcription factors targeting MMP1 were explored by FunRich analysis, HOXA9, PBX1, JUND, JUNB, and JUN were identified to be the top five transcription factors which targeting MMP1 (Fig. 5a). This evidence concerns the gene HOXA9 and non-small cell lung carcinoma.