Well, the answer depends on what cell type you are hoping to express your gene in (I"m not familiar with CAR-NK cells, just going for a general answer here). If you are trying for expression in a prokaryote (e.g. E. coli) then you need to use the intron-free version of your gene and pair it with a promoter that works in that system. Often, this version works well in eukaryotes too (and your gene is quite large so this approach would make cloning easier). However, sometimes introns contain important expression information.

If there are published reports of expressing the same (or similar) genes I'd look at the methods to see what has been done before.

Hope this helps!

Amy Klocko thank you!