Abstract Dimethyl sulfoxide (DMSO) is an amphipathic molecule and has a diversity of antitumor activities. Previous studies demonstrated that DMSO could modulate AP-1 activity and lead to cell cycle arrest at G1 phase. HLJ1 is a newly identified tumor and invasion suppressor that inhibits tumorigenesis and cancer metastasis. Its transcriptional activity is also regulated by transcription factor AP-1. However, the effect of DMSO on HLJ1 is still unknown. In this study, low-HLJ1 expressing highly invasive CL1-5 lung adenocarcinoma cells were subjected to DMSO treatment. We found that DMSO can significantly inhibit cancer cell invasion and migration capabilities through up-regulation of HLJ1 in a concentration-dependent manner. In addition, knockdown of HLJ1 expression by siRNA was able to block the effects of DMSO-induction. The HLJ1 promoter and enhancer reporter assay revealed that DMSO transcriptionally upregulates HLJ1 expression through an AP-1 site within the HLJ1 enhancer. Furthermore, AP-1 subfamily members, JunD and JunB, were significantly upregulated by DMSO in a concentration-dependent manner. In conclusion, our results suggest that DMSO could be an important stimulator of the tumor suppressor protein, HLJ1, through AP-1 activation in highly invasive lung adenocarcinoma CL1-5 cells. Our findings provide some important information for further investigations to develop new drugs such as DMSO-derived analogues which may inhibit cancer invasion and progression by targeting HLJ1. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2360. doi:10.1158/1538-7445.AM2011-2360