Hi Jenn,

It looks to me like uneven electrical field, rather then Dox effect. If the pattern of displacement is different each time check for air bubbles trapped at the bottom of the gel plate, when you pour running buffer above the bottom edge. My gels sometimes constricts after polymerisation leaving a groove at the bottom. I remove the retained air by pipetting buffer up and down near the edge. If this repeats every time and the pattern is identical each run, try also to clean platinum wire mechanically. Sometimes deposits can form over time.

Best regards.

Dear Jennifer,

Dox can affect the level of the expression and phosphorylation of different proteins such as p21 , p27, p53 and Caspases (depend on the cell lines). The phosphorylation of pAKT, pERK will also induced. The treatment of the cells by DOX shouldn't affect the migration of the proteins (only very minor changes, only depend on the level of the proteins). what differences are there on migration? 

As the previous commenters suggest, this sounds more like an SDS-PAGE and/or transfer issue than a biological effect. Perhaps you could upload an image of a stained gel or western blot, and provide more detail of running conditions (gradient or single %age gel, etc.) so that we can help you troubleshoot.