We found that we have this kit from Qiagen but labelled for serum/plasma samples. Can I isolate RNA from frozen cells pellet of MCF7 and MDA-MB231 cell lines using an RNA isolation kit intended for serum/plasma use?
while the miRNeasy Serum/Plasma Kit might work for your frozen cell pellet, it may not be the optimal choice. You might consider using a kit designed for cells to ensure higher RNA yield and quality.