I have used CD133/1 antibody (Human) but didn't observe a detectable amount of the protein in MCF-7 (although I did it only once). There are two possibilities here.

1. There's a mismatch of the epitope.

2. There is no detectable amount of protein on MCF-7 as such.

But the 2nd point is not at all the case, as the literature shows that MCF-7 cells express CD133. So, please give me suggestions on my further experiments.