7329

UBE2I

ubiquitin-conjugating enzyme E2I;UBE2I;ubiquitin-conjugating enzyme E2I

SUMO-1-protein ligase|SUMO-conjugating enzyme UBC9|SUMO-protein ligase|ubiquitin carrier protein 9|ubiquitin carrier protein I|ubiquitin conjugating enzyme 9|ubiquitin-conjugating enzyme E2I (UBC9 homolog, yeast)|ubiquitin-conjugating enzyme E2I (homologo

16p13.3

protein-coding

Ubc9 is an E2-conjugating enzyme that transfers the activated small ubiquitin-like modifier (SUMO) to protein substrates, and thus it has an important function in sumoylation-mediated cellular pathways. We have earlier reported that Ubc9 promotes tumor growth in the xenograft mouse model using breast cancer cell line MCF-7 in part through regulation of Bcl-2 expression. In this study, we show that ectopic expression of wild-type Ubc9 (Ubc9-WT) promotes cell invasion and metastasis. Surprisingly, the dominant negative mutant Ubc9 (Ubc9-DN) also causes the same phenotype, indicating that the ability of Ubc9 to promote invasion and metastasis is distinct from its ability to conjugate SUMO to protein substrates. Of considerable interest, several microRNAs such as miR-224 are regulated by Ubc9. Although ectopic expression of Ubc9 causes downregulation of miR-224, suppression of Ubc9 by Ubc9-siRNAs leads to its upregulation. We further show that miR-224 can inhibit cell invasion and directly targets CDC42 and CXCR4, and that suppression of CDC42 and CXCR4 by RNAi causes inhibition of Ubc9-mediated invasion. Together, these results show a molecular link between Ubc9 and the metastasis genes such as CDC42 and CXCR4, and thus provide new insight into the mechanism by which Ubc9 promotes tumor invasion and metastasis.

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.