piRNAs are the novel members of small non-coding RNAs. They have an impact on both genetic and epigenetic parameters. In this study, we aimed to determine the effect of piR-651 on ERα, hTERT, Ki-67, MMP-2, MMP-9 and HIF-1α protein expressions of MCF-7 breast cancer cells. Non-target and anti-piR-651 RNA sequences were transfected to MCF-7 breast cancer cells by lipofectamine method. After transfection, extracellular and intracellular protein samples were collected. Intracellular and extracellular protein expressions of ERα, hTERT, Ki-67, MMP-2, MMP-9 and HIF-1α were detected by enzyme-like immuno sorbent assay (ELISA). Although intracellular MMP-2 protein expression increased compared to control (p<0.001), neither intra and extracellular ERα, Ki-67, hTERT, HIF-1α or MMP-9 protein expressions changed in anti-piR-651-transfected MCF-7 cells compared to control group (p > 0.05). While extracellular HIF-1α protein expression decreased, extracellular MMP-2 and MMP-9 protein expressions increased in anti-piR-651-transfected cells (p < 0.001). With regard to the protein expressions of ERα, Ki-67, hTERT, HIF-1α and MMP-9, piR-651 inhibition could not affect various cellular characteristics of MCF-7 cells. However, increased protein expression of MMP-2 in both intra and extracellular parameters indicates some possibilities about adhesion. The obtained results provide that piR-651 can only change the adhesion properties 48 hours after its inhibition. It has been shown that this inhibition in MCF-7 cells transfected with anti-piR-651 does not adversely affect cancer development; it promotes death on contrary.