Breast cancer remains a leading cause of tumor-related deaths in the world. The pathogenesis contributing to breast cancer progression has not been fully understood. Increasing evidence suggests that long noncoding RNA (lncRNA) is implicated in various kinds of malignant cancers, including breast cancer. In the study, we attempted to explore the expression and effects of Inc-lung cancer associated transcript 1 (LUCAT1) on breast cancer development. Our results indicated that the expression of Inc-LUCAT1 was highly up-regulated in breast cancer tissues and cell lines. Over-expression of Inc-LUCAT1 enhanced cell proliferation, migration and invasion in breast cancer cell lines. Moreover, Inc-LUCAT1 was found to be a target of miR-7-5p. There was a negative correlation between Inc-LUCAT1 and miR-7-5p. The reduction of miR-7-5p was required in the augmentation of breast cancer development induced by Inc-LUCAT1 over-expression. In addition, SOX2 acted as a target of miR-7-5p. SOX2 was an oncogene in breast cancer through promoting cell proliferation, migration and invasion. The in vivo study confirmed the role of Inc-LUCAT1 in promoting tumor growth, accompanied with down-regulated SOX2 expression, whereas up-regulated miR-7-5p. Collectively, the Inc-LUCAT1/miR-7-5p-SOX2 regulatory pathway might provide a new and effective therapeutic strategy to prevent breast cancer development. (C) 2019 Published by Elsevier Inc.