Lung cancer is the leading cause of cancer-related mortality worldwide. The 
mortality is high mainly due to the lack of known effective screening 
procedures; there is a high tendency for early spread and systemic therapies do 
not cure metastatic disease. Thus, it is important to investigate the molecular 
mechanism(s) of lung cancer development and, specifically, to identify an 
effective method by which to inhibit the invasion and metastasis of lung cancer. 
Ubiquitin-conjugating enzyme 9 (Ubc9), the sole conjugating enzyme for 
sumoylation, regulates protein function and plays a key role in tumorigenesis. 
Whether Ubc9 is involved in the invasion and metastasis of lung cancer remains 
unknown. Herein, we report that Ubc9 exhibits an important role in lung cancer 
invasion and metastasis. We first investigated the biological effect of Ubc9 on 
lung cancer by cloning the Ubc9 gene into a eukaryotic expression plasmid and 
stably expressing it in the human small cell lung cancer cell line NCI-H446 in 
order to observe any biological changes. We further analyzed the effect of Ubc9 
in an in vivo experiment, injecting NCI-H446 cells stably overexpressing Ubc9 
into nude mice and analyzing their metastatic ability. Our results demonstrated 
that Ubc9 is expressed at higher levels in primary lung cancer tissue and 
metastatic nodules as compared to premalignant and/or normal tissue. 
Furthermore, we demonstrated that upregulation of Ubc9 expression promotes 
migration and invasion. Ubc9 likely plays an important role in cancer 
progression by promoting invasion and metastasis in lung cancer.