siRNA / miRNA gene silencing Human MDA-MB-468

I would like to regulate the expression of a gene and in order to do that, I have purchased specific siRNA. After optimizing my transfection protocol and using electroporation I have achieved a 60-70% reduction of the gene of interest. However, I cannot observe a significant reduction of mRNA expression but only a reduction of protein. What might be the problem? Could the problem be in my cell treatment method?

Get tips on using SIRT1 siRNA and shRNA Plasmids (h) to perform siRNA / miRNA gene silencing Human - PC3 (human prostate cancer cell line) SIRT1

Get tips on using Silencer select_ObR siRNA to perform siRNA / miRNA gene silencing Human - MCF-7 ObR(leptin receptor/LEPR)

Get tips on using esiRNA human PTPN3 (esiRNA1) to perform siRNA / miRNA gene silencing Human - A2780 PTPN3

Get tips on using ON-TARGETplus SMARTpool - Human to perform siRNA / miRNA gene silencing Human - U2OS DKC1

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Get tips on using siRNA MAPKAPK-2 to perform siRNA / miRNA gene silencing Human - U937 MK2 (MAPK Kinase 2) Viral vectors

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Get tips on using mirVana® miRNA mimic to perform siRNA / miRNA gene silencing Human - Primary Endometrial Stromal Cells hsa-miR-542-3p