What's the purity of your single-cell clone in terms of Luciferase expression? Do you monitor this? In transgenic cell lines, one can never forget that some cells might lose their insert, which can happen during in vitro passaging and in vivo transplantations. Perhaps this is one of the reasons for the lack of consistency you observe between tumour size and luminescence.

You can also purify a cell line from your primary tumours, put it back into culture, and check the purity again. If this is your problem, this experiment might help you understand where the loss of the construct is happening.

Let us know how you solved this :)

It's a common problem, I would say!

All the best.

Afonso Teixeira da Mota Thanks Dr. Teixeira, it is a good point to check the purity of the single clone in vitro. I haven't do that. And one concern is that I cannot see the luc signals by microscope, do you mean I can do it by flow cell sorter? or you have better methods.

After check single cell luc signals, the following cell line culture from the primary tumors would be easy.