Which terminology is better: Heterologous expression system or heterologous cell model? I am reading a journal paper and I have read that the authors expressed the extracellular domain of the protein NCAM2 which is normally found in the brain in CHO cells. I know that this is an example of heterologous expression. However, when referring to these CHO cells which are overexpressing NCAM2 I am wondering whether the terminology 'heterologous expression system' is more appropriate compared to 'heterologous cell model'? Any insights are appreciated.

I would suggest that the preferable term depends on whether you are talking about the cells or talking about the modifications.

In other words, I would refer to the NCAM2 expression package as the "heterologous expression system", which is then integrated into the CHO platform in order to create a "heterologous cell model."

My reason for this suggestion is that the expression package is the core construct without which there is no expression, and that this package might potentially be transferred into other cell lines to construct other cellular models.