lncRNA TTN-AS1 facilitates proliferation, invasion, and epithelial-mesenchymal transition of breast cancer cells by regulating miR-139-5p/ZEB1 axis.

Breast cancer is a common malignant tumor suffered predominantly by women worldwide, which results in serious levels of morbidity and mortality. To control the effects of the cancer, it is critically important to elucidate the pathophysiological processes by which it occurs and develops. Reports have demonstrated that long noncoding RNAs perform a critical role in the development and metastasis of cancers. The lncRNA TTN-AS1 is considered carcinogenic. Nevertheless, the importance and biological functions of TTN-AS1 in breast cancer require greater exploration. In the current paper, we observed that TTN-AS1 expression was significantly upregulated in breast cancer tissues/cells compared with those that are healthy. TTN-AS1 enhanced the proliferation, migration, invasion, and epithelial-mesenchymal transformation of breast cancer cells. Furthermore, a direct target of TTN-AS1, miR-139-5p was negatively regulated. In addition, zinc finger E-box binding homeobox 1 (ZEB1) is an important nuclear transcription factor, the expression of which is increased in multiple tumors. Here, we also found that ZEB1 is a target of miR-139-5p, of which TTN-AS1 could regulate the expression through competition with miR-139-5p. That is, TTN-AS1 promoted proliferation and invasion of breast cancer cells by interaction with the miR-139-5p/ZEB1 axis. In conclusion, the present study aimed to illustrate the significance of TTN-AS1 in breast cancer metastasis and contribute to potentially innovative strategies for its treatment.