Hi Nina, you may go for MCF7 SP breast cancer cells, which have been characterized as CD44+CD24−CK18+EpCAM+ CK19+ according with Steiniger et al (Stem Cells. 2008;26:3037–3046 and Engelmann et al (Cancer Res. 2008;68:2419–2426). If you're curious about have a look at the review by Kelly Britton and collegues (Cancers (Basel). 2011: 2106–2130). SP stands for Side Population and refers to a population of stem/progenitor cells which derives from the MCF7 cells. Hope you're good in getting these cells from someone close by you. Cheers!
I am also supposed to work on Mcf-7 and my work starts in a fortnight. I have gone through various culturing protocols for the Mcf-7. There seems to be a discrepancy about Insulin supplementation. Did you use insulin for your culture?