Non specific bands on Western blot - (Apr/18/2006 )

Hi everybody!
I have transfected my K562 cells with an HA tag protein. After doing I western from cells lysis I get several non specific bands with a higher molecular weight then the expected. And these bands were more intense than my band
Anyone of you can explain it?

is your antibody polyclonal? could be non-specific, or a cross-reaction...

also, was there some modification of the protein in your cells after expression was induced?