MicroRNA (miRNA) expression is a dynamic process in the cell, and the proper time period for post-transcriptional regulation might be critical due to the gene-on/-off expression times of the cell. Here, we investigated the effect of different time-points on proliferation, invasion and miRNA expression profiles of human breast cancer cell lines MCF-7 (non-metastatic, epithelium-like breast cancer cell line with oestrogen receptor (ER) positive (+) and human breast cancer cell lines MDA-MB-435 (metastatic, invasive, ER negative (-). For this purpose, MCF-7 and MDA-MB-435 cells were seeded different number in E-plate 16 for proliferation experiment using an electrical impedance-based real-time cell analyzer system (RTCA) for 168 h. Similarly, invasion potential of MCF-7 and MDA-MB-435 were determined by RTCA for 90 h. Total RNAs including miRNAs were isolated at 2, 4, 6, 12, 24, 48 h from the MCF-7 and MDA-MB-435 cells. Afterward, the quantitative 84 miRNA expressions of MCF-7 and MDA-MB-435 were analyzed by Fluidigm Microfluidic 96.96 Dynamic Array. The results of these study demonstrated that both proliferation potential and invasion capacity of MDA-MB-435 is higher than MCF-7 as time-dependent manner. Furthermore, we detected that up/down expressions of 32 miRNAs at all time points in MDA-MB-435 compared to MCF-7 (at least ten-fold increased). Because of the high number of miRNAs, we more closely evaluated the expression of six of them (miR-100–5p, miR-29a-3p, miR-130a-3p, miR-10a-5p, miR-10b-5p, miR-203a), and determined that their levels were dramatically changed by at least 50-fold at different time points of the experiment (p
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