It will certainly give you an idea of cellular mRNA expression, or at least be correlated with cellular expression. That said, you  won't know the cellular origin of this expression, except if you are very sure that your gene is cell type specific (but in most cases, it won't be the case). Cell free mRNA can originate from cells of the blood lineage, but there are more and more evidences that it can also come from tissues, either healthy or pathological, such as tumors, atheromas, non-alcoholic fatty liver, in short dying cells of many different origins.

What you can do is to use your gene expression level as a biomarker or pronostic factor if it correlates with clinical parameters such as patient survival, response to treatment... Good luck!

No.

If you could even detect your mRNA of interest free in serum/plasma, you'd have no idea where it came from. Additionally, level outside a cell tells you nothing about level inside a cell.

While there may be a correlation between the cellular mRNA expression and the circulating mRNA, I am not sure how stable will RNA be in the plasma so as to give quantitative results.

thanks alt

I want to test the expression of gamma globin gene which has a unique origin and their is no need to know where it comes from