Injection of human cells into mouse mammary fat pad - (Oct/11/2006 )

I'm about to start the in vivo work and have to inject breast cancer cells into the mouse mammary fat pad. Quite a few papers suggest ususpending the cells in Matrigel - why? i know this might be a naive question, but I'm very new to this work. Will I need to anaesthatise the mice prior to injection, or will the cells be better off implanted?

Cheers!

This paper (link) gives some good explanations as to why matrigel is suggested when injecting cells. Essentially what it says is that matrigel can increase the uptake of the tumor cells as well as enhance the tumor growth. We use this technique when doing injections of cells into the liver. I don't know what the pros and cons are between injection and implantation. My lab does more injections of cells than they do implantations. I would imagine you would want to anesthesize the mouse so that you can inject more accurately and so that you can inject the cells slowly.