Compared with adjacent normal tissues,HOST2 expression was higher but let-7b expression lower in breast cancer tissues. HOST2 expression in breast cancer cells was remarkably increased compared with that in the normal breast epithelial MCF-10A cells.In MCF-7 cells,in comparison with the blank and NC groups,expressions of HOST2 and c-Myc were reduced,but let-7b expression was remarkably elevated in the siHOST2 and let-7b mimic groups,the let-7b inhibitor group exhibited higher expressions of HOST2 and c-Myc but lower let-7b expression.Overexpression of HOST2 could promote cell motility,migration and invasion,thus enhancing the growth of breast cancer tumor. By inhibiting HOST2,opposite trends were found.LncRNA HOST2 promotes cell migration and invasion by inhibiting let-7b in breast cancer patients.