siRNA / miRNA gene silencing Human UCC (urothelial cancer cell lines)

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 Gβ 1 siRNA (h) to perform siRNA / miRNA gene silencing Human - T47-D GNB1

Get tips on using Stealth siRNA™ NOTCH2 to perform siRNA / miRNA gene silencing Human - THP-1 NOTCH2

Get tips on using Stealth siRNA™ NOTCH1 to perform siRNA / miRNA gene silencing Human - THP-1 NOTCH1

Get tips on using caveolin-1 siRNA (h) to perform siRNA / miRNA gene silencing Human - BEAS-2B CAV1

Get tips on using Flotillin-2 siRNA (h) to perform siRNA / miRNA gene silencing Human - BEAS-2B FLOT2

Get tips on using Rab 7 siRNA (h) to perform siRNA / miRNA gene silencing Human - BEAS-2B RAB7A

Get tips on using Rab 5C siRNA (h) to perform siRNA / miRNA gene silencing Human - BEAS-2B RAB5C

Get tips on using AMPKα1/2 siRNA (h) to perform siRNA / miRNA gene silencing Human - HepG2 AMPKα1/α2

Get tips on using GLI-1 siRNA (h) to perform siRNA / miRNA gene silencing Human - NHLF GLI-1