Insulinomas are (in general) benign tumors that are largely composed of regenerated beta cells, and that produce insulin.
This study identified the genomic differences between regular beta cells and insulinomas:
What I think is interesting in this study: if my brother can ever get new beta cells working in his body, they will be regenerated beta cells. Insulinomas are a natural example of regenerated beta cells. So it seems to me that studying insulinomas is the right way to proceed in the direction of learning how to regenerate beta cells.
Another way would be to work on undifferentiated stem cells and try to turn them into beta cells. But I don’t know anyone who works on that today. So I think insulinomas are the next best.