Objective To determine the expression of miR-335 in breast cancer cells( BT474,T47 D,MCF-7,SK-BR-3,and MDA-MB-231) and normal breast cells( MCF-10A) and in primary breast cancer and lymph node metastatic breast cancer,and investigate the effect of miR-335 on the proliferation,apoptosis,and migration of MDA-MB-231 cells. Methods MDA-MB-231 cells were divided into 3 groups: a miR-335 group( transfected with miR-335 mimics),a control group( transfected with negative control) and a blank group( non-transfected)...