I am working with breast cancer and healthy cell lines that are MCF7 MDA-MB-231 and MCF10A and I want to confirm them. Is there any biological marker to use for confirmation?
I would suggest making use of the ATCC Human STR profiling service for cell line authentication - it is a really easy process to send samples of each cell line to them and they will do the authentication and email the results back to you! In my experience this is the easiest and best way to validate your different cell lines which will be suitable and accepted by journals when it comes time for you to publish your data.
If you need this for publication purposes I would definitely do as Megan suggested and in case commercial testing is not available develop your own PCR protocol looking at the differential mutations across the three cell lines. CCLE database is a good place to start here.