beta-elemene, a compound derived from Rhizoma zedoariae, is a promising new plant-derived drug with broad-spectrum anticancer activity. However, the underlying mechanism by which this agent inhibits human lung cancer cell growth has not been well elucidated. In this study, we showed that -elemene inhibits human non-small cell lung carcinoma (NSCLC) cell growth, and increased phosphorylation of ERK1/2, Akt and AMPK. Moreover, -elemene inhibited expression of DNA methyltransferase 1 (DNMT1), which was not observed in the presence of the specific inhibitors of ERK (PD98059) or AMPK (compound C). Overexpression of DNMT1 reversed the effect of -elemene on cell growth. Interestingly, metformin not only reversed the effect of -elemene on phosphorylation of Akt but also strengthened the -elemene-reduced DNMT1. In addition, -elemene suppressed Sp1 protein expression, which was eliminated by either ERK1/2 or AMPK inhibitor. Conversely, overexpression of Sp1 antagonized the effect of -elemene on DNMT1 protein expression and cell growth. Taken together, our results show that -elemene inhibits NSCLC cell growth via ERK1/2- and AMPK-mediated inhibition of transcription factor Sp1, followed by reduction in DNMT1 protein expression. Metformin augments the effect of -elemene by blockade of Akt signalling and additively inhibition of DNMT1 protein expression. The reciprocal ERK1/2 and AMPK signalling pathways contribute to the overall responses of -elemene. This study reveals a potential novel mechanism by which -elemene inhibits growth of NSCLC cells.