varying morphology of MCF-10A line - (Mar/26/2007 )

So I have been culturing MCF-10A cells for about two years (not the same thaw, don't worry!) and have noticed some things that puzzle me and wonder if anyone else has had these problems and/or can offer some explanation...

1. Sometimes when I thaw a vial (always low passage) the cells look like textbook 10As whereas other times they are little more elongated, not so rounded and seem to grow a little faster. I have not changed the supplier of my media, serum or growth factors in the time I have been growing them. Should I be worried?

2. My cultures experience a rapid decrease in transfection efficency over the course of about 2-3 weeks. It's to the point that I have to do my n=3 experiments all in the same week!

I grow my cells in DMEM/F12 +5% horse serum, with pen/strep, gentamicin, fungizone (low concentration), EGF, hydrocortisone and insulin. I have ordered these cells 2x from ATCC and have always had these problems. Am I going nuts???

Any help would be greatly appreciated!!!

Hi
I was also worried about that, but I was told then that MCF10A cells are known to have 2 different morphologies, they can be smaller, more like epithelial or they can be bigger and elongated, and with passaging you will get more and more elongated ones.

Thank you so much!!!! I thought I was going a bit nutty...