MCF-7 cell-E2 responsiveness - (Aug/17/2006 )

Guys
I had problem with MCF-7 cells (from ATCC). This cells repeatedly lost E2 responsiveness. I don't know what happen to them? It looks like there is no ER positive cell anymore.
Is there any good, strong positive ER MCF-7 subtype cell?

I dont know about the subtyoe. But T-47 D is quite sturdy and gives a good E2 response.