I am culturing MCF-7 cells (P35) , did RNA extraction, cDNA synthesis and gradient PCR for a few housekeeping genes like GAPDH and Actin. However, the expression level for this genes seem to be very lowly expressed or sometimes not present at all in the gel.
The cells look relatively healthy, so am wondering if cells with high passage numbers will affect this?
In short, yes. For a comprehensive list of alterations due to repeated passaging read (https://www.atcc.org/en/Services/Testing_Services/Cell_Authentication_Testing_Service/Passage_Number_Effects_in_Cell_Lines.aspx). It is also likely that some mutations occurred and your primers are no longer complementary. (Article The Costs of using Unauthenticated, Over-Passaged Cell Lines...
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In general, MCF-7 is a cell line. Therfore, these cells should be relatively stable regarding expression and other profiles over time. However, in the context of tumoigenicity, it was found that the behaviour of these cells was affected/changed in higher passages (e.g. see: Cancer Lett. 2012 Mar;316(1):53-61).
Thus, yes, expression profile may be altered in later passages compared to lower passage numbers in these cells.
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